桥梁专业外文翻译--欧洲桥梁研究

Prestressed Concrete bridgesPrestressed concrete has been used extensively in U.S. bridge construction since its first introduction from Europe in the late 1940s. Literally thousands of highway bridges of both precast, prestressed concrete and cast-in-place post-tensioned concrete have been constructed in the United States. Railroad bridges utilizing prestressed concrete have become common as well. The use and evolution of prestressed concrete bridges is expected to continue in the years ahead.Short-span BridgeShort-span Bridge, as shown in Fig.18for the purposes of this discussion, will be assumed to have a maximum span of 45ft (13.7m). It should be understood that this is an arbitrary figure, and there is no definite line of demarcation between short, moderate, and long spans in highly bridges. Short-span bridges are most efficiently made of precast prestressed-concrete hollow slabs, I-beams, solid slabs or cast-place solid slabs, and the T-beams of relativily generous proportions.Precast solid slabs are most economical when used on very short spans. The slabs can be made in any convenient width, but widths of 3 or 4ft(0.9 to 1.2m ) have been common. Keys frequently are cast in the longitudinal sides of the precast units. After the slabs have been erected and joints between the slabs have been filled with concrete, the keys transfer live load shear forces between the adjacent slabs.Precast hollow slabs used in short-span bridge may have round or square void. They too are generally made in units 3 to 4 ft (0.9 to 1.2m) wide with thicknesses from 18 to 27 inch 9 (45.7 to 68.8cm). Precast hollow slabs can be made in any convenient width and depth, and frequently are used in bridges having spans from 20 to 50 ft (6.1 to 15.2cm). Longitudinal shear keys are used in the joints between adjacent hollow slabs in the same way as with solid slabs, but the use of a leveling course of some type normally is required as a means of obtaining an acceptable appearance and levelness.Transverse reinforcement normally is provided in precast concrete bridge superstructures for the purpose of tying the structure together in the transverse direction. Well-designed ties ensure that the individual longitudinal members forming the superstructure will act as a unit under the effects of the live load. In slab bridge construction, transverse ties most frequently consist of threaded steel bars placedthrough small holes formed transversely through the member during fabrication. Nuts frequently are used as fasteners at each end of the bars. In some instances, the transverse ties consist of post tensioned tendons placed, stressed, and grouted after the slabs have been erected. The transverse tie usually extends from one side of the bridge to the other.The shear forces imposed on the stringers in short-span bridges frequently are too large to be resisted by the concrete alone. Hence, shear reinforcement normally is required. The amount of shear reinforcement required may be relatively large if the webs of the stringers are relatively thin.Concrete diaphragms, reinforced with post-tensioned reinforcement or nonprestressed reinforcement, normally are provided transversely at ends and at intermediate locations along the span in stringer-type bridges. The diaphragms ensure the lateral-distribution of the live loads to the various stringers from displacing or rotating significantly with respect to the adjacent stringers.No generalities will be made here about the relative cost of each of the above types of construction; construction costs are a function of many variables which prohibit meaningful generalizations. However, it should be noted that the stringer type of construction requires a considerably greater construction depth that is requires a considerably greater construction depth that is required for solid, hollow, or channel slab bridge superstructure. Stringer construction does not require a separate wearing surface, as do the precast slab types of construction, unless precast slabs are used to span between the stringers in lieu of the more commonly used cast-in-place reinforced concrete deck. Strings construction frequently requires smaller quantities of superstructure materials than do slab bridges (unless the spans are very short). The construction time needed to complete a bridge after the precast members have beenerected is greater with stringer framing than with the slab type of framing.Bridge of moderate spanAgain for the purposes of this discussion only, moderate spans for bridges of prestressed concrete are defined as being from 45 to 80ft (13.7 to 24.4m). Prestressed concrete bridges in this spans range generally can be divided into two types; stringer-type bridges and slab-type bridges and slab-type bridges. The majority of the precast prestressed concrete bridges constructed in the United States have been stringer bridges using I-shaped stringers, but a large number of precast prestressedconcrete bridges have been constructed with precast hollow-box girders (sometimes also called stringer). Cast-in-place post-tensioned concrete has been used extensively in the construction of hollow-box girder bridges-a form of construction that can be considered to be a slab bridge.Stringer bridges, which employ a composite, cast-in-place deck slab, have been used in virtually all parts of the United States. These stringers normally are used at spacing of about 5 to 6 ft (1.5 to 1.8m). The cast-in-place deck is generally form 6.0 to 8.0 inch (15.2 to 20.3 cm) in thickness. This type of framing is very much the same as that used on composite stringer construction for short-span bridges.Diaphragm details in moderate-span bridges are generally similar to those of the short spans, with the exception that two or three interior diaphragms sometime are used, rather than just one at mid span as in the short-span bridge.As in the case of short-span bridges, the minimum depth of construction in bridges of moderate span is obtained by using slab construction, which may be either solid-or hollow-box in cross section. Average construction depths are required when stringers with large flanges are used in composite construction, and large construction depths are required when stringers with small bottom flanges are used. Composite construction may be developed through the use of cast-in-place concrete decks or with precast construction may be developed through the use of cast-in-place concrete decks or with precast concrete decks. Lower quantities of materials normally are required with composite construction, and dead weight of the materials normally is less for stringer construction than for slab construction.Long-Span BridgesPrestressed concrete bridges having spans of the order of 100 ft are of the same general types of construction as structures having moderate span lengths, with the single exception that solid slabs are not used for long spans. The stringer spacings are frequently greater (with stringers at 7 to 9 ft) as the span lengths of bridges increase. Because of dead weight consideration, precast hollow-box construction generally is employed for spans of this length only when the depth of construction must be minimized. Cast-in-place post-tensioned hollow-box bridges with simple and continues spans frequently are used for spans on the order of 100 ft and longer.Simple, precast, prestressed stringer construction would be economical in the United States in spans up to 300 ft under some condition. However, only limited use has been made of this type of construction on spans greater than 100 ft. For very longsimple spans, the advantage of precasting frequently is nullified by the difficulties involved in handing, transporting, and erecting the girders, which may have depths as great as 10 ft and weight over 200 tons. The exceptions to this occur on large projects where all of the spans are over water of sufficient depth and character that precast beams can be handled with floating equipment, when custom girder launchers can be used, and when segmental construction techniques can be used.The use of cast-in-place, post-tensioned, box-girder bridges has been extensive. Although structures of these types occasionally are used for spans less than 100 ft, they more often are used for spans in excess of 100ft and have been used in structures having spans in excess of 300ft. Structure efficient in flexure, especially for continues bridges, the box girder is torsionally stiff and hence an excellent type of structure for use on bridges that have horizontal curvature. Some governmental agencies use this form of construction almost exclusively in urban areas where appearance from the side, is considered important.Segmental BridgesBridges that are constructed in pieces of one various connected together in some way, frequently are referred to as segmental bridges. The segments may be cast-in-place or precast, elongated units, such as portions of stringers or girders, or relatively short units that are as wide as the completed bridge superstructure.The Esbly Bridge in France is an example of one of the earliest precast concrete segmental bridges. This bridge is one of five bridges that were made with the same dimensions and utilized the same steel molds for casting the concrete units. All of the bridges span the River Marne, and because of the required navigational clearances and the low grades on the roads approaching the bridge, the depth of construction at the center of each span was restricted. The bridges were formed of precast elements, 6ft long, and were made in elaborate molds by first casting and steam-curing the top and bottom flanges in which the ends of the web reinforcement were embedded. The flanges were then jacked apart, and held apart by the web forms resulted in the prestressing of the webs. The 6-ft-long elements were temporarily post-tensioned in the factory into units approximately 40ft long. The 40ft units were transported to the bridge site, raised into place, and post-tensioned together longitudinally, after which the temporary post tensioned was removed. Each span consists of six ribs or beams that were post tensioned together transversely after they were erected. Hence, the beams are triaxially prestressed. The completed Esbly Bridge consists of a very flat,two hinged, prestressed concrete arch with a span of 243 ft and a depth at midspan of about 3ft.Cast-in-place prestressed concrete segmental construction, in which relatively short, full-width sections of a bridge superstructure are constructed, cantilevered from both sides of a pier, originated in Germany shortly after World War 2. This procedure sometimes is referred to as balanced cantilever construction. The well-known, late German engineer U.Finterwalder is credited with being originator of the technique. The basic construction sequence used in this method is illustrated in Fig.18.2 which shows that segments, erected one after another on each side of a pier, form cantilevered spans. The construction sequence normally progresses from pier to pier, from one end of the bridge to the other, with the ends of adjacent cantilevered being joined together to continuous deck. The individual segments frequently are made in lengths of 12 to 16 ft in cycles of four to seven days. The method has been used in the United States for bridges having spans as long as 750ft.The segmental construction technique also has been used with precast segments. The technique originated in France and has been used in the construction of bridges having spans in excess of 300ft. the eminent French engineer Jean Muller is credited with originating precast segment bridge construction using match cast segments. The precast segment may be erected in balanced cantilever, similar to the method described above for cast-in-place segment bridges construction in cantilever, or by using span-by-span technique. Precast segments have been made in precasting plants located on the construction site as well as off site. The segments frequently are stored for a period of weeks or months before being moved to the bridge site and erected- a factor having favorable effects on concrete strength, shrink-age, and creep. Construction of precast segmental bridge superstructures normally progresses at a rapid rate once the erection progress begins. The erection of precast concrete segments normally does not commence, however, until such time as a large number of segments have been precast and stockpiled because the erection normally can progress at a faster rate than the production of the segments.Bridge DesignThe design of bridges requires the collection of extensive date and from this the selection of possible options. From such a review the choice is narrowed down to a shortlist of potential bridge design. A sensible work plan should be devised for the marshaling and deployment of information throughout the project from conception tocompletion to completion. Such a checklist will vary from project to project but a typical example might be drawn up on the following lines.Selection of Bridge TypeThe chief factors in deciding whether a bridge will be built as girder, cantilever, truss, arch, suspension, or some other type are: (1) location ;for example, across a river ; (2) purposes; for example, a bridge for carrying motor vehicles; (3) span length;(4) strength of available materials; (5) cost ; (6) beauty and harmony with the location.Each type of bridge is most effective and economical only within a certain range of span lengths, as shown in the following table:Selection of MaterialThe bridge designer can select from a number of modern high-strength materials, including concrete, steel, and a wide variety of corrosion-resistant alloy steels.For the Verrazano-narrows bridge, for example, the designer used at least seven different kinds of alloy steel, one of which has a yield strength of 50000 pounds per square inch (psi) (3515 kgs/sq cm) and does not need to be painted because an oxide coating forms on its surface and inhibits corrosion. The designer also can select steel wires for suspension cables that have tensile strengths up to 250 000 psi (14 577 kgs/sq cm).Concrete with compressive strength as high as 8 000 psi (562.5 kgs/sq cm) can now be produced for use in bridges, and it can be given high durability against chipping and weathering by the addition of special chemical and control of the hardening process. Concrete that has been prestressed and reinforced with steel wires has a tensile strength of 250 000 psi (17 577kgs/sq cm).Other useful materials for bridges include aluminum alloys and wood. Modern structural aluminum alloys have yield strengths exceeding 40 000 psi (2 812 kgs/spcm). Laminated strips of wood glued together can be made into beams with strengths twice that of natural timbers; glue-laminated southern pine, for example, can bear working stresses approaching 3 000 psi (210.9 kgs/sq cm).Analysis of ForcesA bridge must resist a complex combination of tension, compression, bending, shear, and torsion forces. In addition, the structure must provide a safety factor as insurance against failure. The calculation of the precise nature of the individual stresses and strains in the structure, called analysis, is perhaps the most technically complex aspect of bridge building. The goal of analysis is to determine all of the forces that may act on each structural member.The forces that act on bridge structure member are produced by two kinds of loads-static and dynamic. The static load-the dead weight of bridge structure itself-is usually the greatest load. The dynamic or live load has components, including vehicles carried by the bridge, wind forces, and accumulation of ice and snow.Although the total weight of the vehicles moving over a bridge at any time is generally a small fraction of the static and dynamic load, it presents special problems to the bridge designer because of the vibration and impact stresses created by moving vehicles. For example, the sever impacts caused by irregularities of vehicle motion or bumps in the roadway may momentarily double the effect of the live load on the bridge.Wind exerts forces on a bridge both directly by striking the bridge structure and indirectly by striking vehicles that are crossing the bridge. If the wind induces aeronautic vibration, as in the case of the Tacoma Narrows Bridge, its effect may be greatly amplified. Because of this danger, the bridge designer makes provisions for the strongest winds that may occur at the bridge location. Other forces that may act on the bridge, such as stresses created by earthquake tremors must also be provided for.Special attention must often be given to the design of bridge piers, since heavy loads may be imposed on them by currents, waves, and floating ice and debris. Occasionally a pier may even be hit by a passing ship.Electronic computers are playing an everincreasing role in assisting bridge designers in the analysis of forces. The use of precise model testing particularly for studying the dynamic behavior of bridges, also helps designers. A scaled-down model of the bridge is constructed, and various gauges to measure strains, acceleration, and deforestation are placed on the model. The model bridge is then subjected to variousscaled-down loads or dynamic conditions to find out what will happen. Wind tunnel tests may also be made to ensure that nothing like the Tacoma Narrows Bridge failure can occur. With modern technological aids, there is much less chance of bridge failure than in the past.预应力混凝土桥19世纪40年代后期，预应力混凝土首次引入美国，很快便广泛应用于桥梁结构中。

道路与桥梁专业外文翻译中英对照Jenny was compiled in January 2021本科毕业设计（论文）专业名称：土木工程专业（道路与桥梁）年级班级：道桥08-5班学生姓名：指导教师：二○一二年五月十八日专业外文翻译Geometric Design of HighwaysThe road is one kind of linear construction used for travel. It is made of the roadbed, the road surface, the bridge, the culvert and the tunnel. In addition, it also has the crossingof lines, the protective project and the traffic engineeringand the route facility.The roadbed is the base of road surface, road shoulder,side slope, side ditch foundations. It is stone material structure, which is designed according to route's planeposition .The roadbed, as the base of travel, must guaranteethat it has the enough intensity and the stability that can prevent the water and other natural disaster from corroding.The road surface is the surface of road. It is single or complex structure built with mixture. The road surface require being smooth, having enough intensity, good stability and anti-slippery function. The quality of road surface directly affects the safe, comfort and the traffic.Highway geometry designs to consider Highway Horizontal Alignment, Vertical Alignment two kinds of linear and cross-sectional composition of coordination, but also pay attentionto the smooth flow of the line of sight, etc. Determine theroad geometry, consider the topography, surface features,rational use of land and environmental protection factors, to make full use of the highway geometric components of reasonable size and the linear combination.DesignThe alignment of a road is shown on the plane view and is a series of straight lines called tangents connected by circular. In modern practice it is common to interpose transition orspiral curves between tangents and circular curves.Alignment must be consistent. Sudden changes from flat to sharp curves and long tangents followed by sharp curves must be avoided; otherwise, accident hazards will be created. Likewise, placing circular curves of different radii end to end (compound curves) or having a short tangent between two curves is poor practice unless suitable transitions between them are provided. Long, flat curves are preferable at all times, as they are pleasing in appearance and decrease possibility of future obsolescence. However, alignment without tangents is undesirable on two-lane roads because some drivers hesitate to pass on curves. Long, flat curves should be used for small changes in dir ection, as short curves appear as “kink”. Also horizontal and vertical alignment must be considered together, not separately. For example, a sharp horizontal curve beginning near a crest can create a serious accident hazard.A vehicle traveling in a curved path is subject to centrifugal force. This is balanced by an equal and opposite force developed through cannot exceed certain maximums, and these controls place limits on the sharpness of curves that can be used with a design speed. Usually the sharpness of a given circular curve is indicated by its radius. However, for alignment design, sharpness is commonly expressed in terms of degree of curve, which is the central angle subtended by a 100-ft length of curve. Degree of curve is inversely proportional to the radius.Tangent sections of highways carry normal cross slope; curved sections are super elevated. Provision must be made for gradual change from one to the other. This usually involves maintaining the center line of each individual roadway at profile grade while raising the outer edge and lowering theinner edge to produce the desired super elevation is attained some distance beyond the point of curve.If a vehicle travels at high speed on a carefullyrestricted path made up of tangents connected by sharp circular curve, riding is extremely uncomfortable. As the car approaches a curve, super elevation begins and the vehicle is tilted inward, but the passenger must remain vertical since there is on centrifugal force requiring compensation. When the vehicle reaches the curve, full centrifugal force develops at once, and pulls the rider outward from his vertical position. To achieve a position of equilibrium he must force his body far inward. As the remaining super elevation takes effect, further adjustment in position is required. This process is repeated in reverse order as the vehicle leaves the curve. When easement curves are introduced, the change in radius from infinity on the tangent to that of the circular curve is effected gradually so that centrifugal force also develops gradually. By careful application of super elevation along the spiral, a smooth and gradual application of centrifugal force can be had and the roughness avoided.Easement curves have been used by the railroads for many years, but their adoption by highway agencies has come only recently. This is understandable. Railroad trains must follow the precise alignment of the tracks, and the discomfort described here can be avoided only by adopting easement curves. On the other hand, the motor-vehicle operator is free to alter his lateral position on the road and can provide his own easement curves by steering into circular curves gradually. However, this weaving within a traffic lane (but sometimes into other lanes) is dangerous. Properly designed easement curves make weaving unnecessary. It is largely for safety reasons,then, that easement curves have been widely adopted by highway agencies.For the same radius circular curve, the addition ofeasement curves at the ends changes the location of the curve with relation to its tangents; hence the decision regardingtheir use should be made before the final location survey. They point of beginning of an ordinary circular curve is usually labeled the PC (point of curve) or BC (beginning of curve). Its end is marked the PT (point of tangent) or EC (end of curve).For curves that include easements, the common notation is, as stationing increases: TS (tangent to spiral), SC (spiral to circular curve), CS (circular curve to spiral), and ST (spiralgo tangent).On two-lane pavements provision of a wilder roadway is advisable on sharp curves. This will allow for such factors as(1) the tendency for drivers to shy away from the pavement edge,(2) increased effective transverse vehicle width because thefront and rear wheels do not track, and (3) added width because of the slanted position of the front of the vehicle to the roadway centerline. For 24-ft roadways, the added width is so small that it can be neglected. Only for 30mph design speedsand curves sharper than 22°does the added width reach 2 ft.For narrower pavements, however, widening assumes importance even on fairly flat curves. Recommended amounts of and procedures for curve widening are given in Geometric Design for Highways.2. GradesThe vertical alignment of the roadway and its effect on the safe and economical operation of the motor vehicle constituteone of the most important features of road design. The vertical alignment, which consists of a series of straight linesconnected by vertical parabolic or circular curves, is known as the “grade line.” When the grade line is increasing from the horizontal it is known as a “plus grade,” and when it is decreasing from the horizontal it is known as a “minusgrade.” In analyzing grade and grade controls, the designer usually studies the effect of change in grade on the centerline profile.In the establishment of a grade, an ideal situation is onein which the cut is balanced against the fill without a great deal of borrow or an excess of cut to be wasted. All haulsshould be downhill if possible and not too long. The gradeshould follow the general terrain and rise and fall in the direction of the existing drainage. In mountainous country the grade may be set to balance excavation against embankment as a clue toward least overall cost. In flat or prairie country itwill be approximately parallel to the ground surface but sufficiently above it to allow surface drainage and, where necessary, to permit the wind to clear drifting snow. Where the road approaches or follows along streams, the height of thegrade line may be dictated by the expected level of flood water. Under all conditions, smooth, flowing grade lines arepreferable to choppy ones of many short straight sections connected with short vertical curves.Changes of grade from plus to minus should be placed in cuts, and changes from a minus grade to a plus grade should be placed in fills. This will generally give a good design, and many times it will avoid the appearance of building hills and producing depressions contrary to the general existing contours of the land. Other considerations for determining the gradeline may be of more importance than the balancing of cuts and fills.Urban projects usually require a more detailed study of the controls and finer adjustment of elevations than do rural projects. It is often best to adjust the grade to meet existing conditions because of the additional expense of doing otherwise.In the analysis of grade and grade control, one of the most important considerations is the effect of grades on the operating costs of the motor vehicle. An increase in gasoline consumption and a reduction in speed are apparent when grades are increase in gasoline consumption and a reduction in speedis apparent when grades are increased. An economical approach would be to balance the added annual cost of grade reduction against the added annual cost of vehicle operation withoutgrade reduction. An accurate solution to the problem depends on the knowledge of traffic volume and type, which can be obtained only by means of a traffic survey.While maximum grades vary a great deal in various states, AASHTO recommendations make maximum grades dependent on design speed and topography. Present practice limits grades to 5 percent of a design speed of 70 mph. For a design speed of 30 mph, maximum grades typically range from 7 to 12 percent, depending on topography. Wherever long sustained grades are used, the designer should not substantially exceed the critical length of grade without the provision of climbing lanes forslow-moving vehicles. Critical grade lengths vary from 1700 ft for a 3 percent grade to 500 ft for an 8 percent grade.Long sustained grades should be less than the maximum grade on any particular section of a highway. It is often preferredto break the long sustained uniform grade by placing steeper grades at the bottom and lightening the grade near the top of the ascent. Dips in the profile grade in which vehicles may be hidden from view should also be avoided. Maximum grade forhighway is 9 percent. Standards setting minimum grades are of importance only when surface drainage is a problem as when water must be carried away in a gutter or roadside ditch. In such instances the AASHTO suggests a minimum of %.3. Sight DistanceFor safe vehicle operation, highway must be designed to give drivers a sufficient distance or clear version ahead so that they can avoid unexpected obstacles and can pass slowervehicles without danger. Sight distance is the length of highway visible ahead to the driver of a vehicle. The conceptof safe sight distance has two facets: “stopping” (or “no passing”) and “passing”.At times large objects may drop into a roadway and will do serious damage to a motor vehicle that strikes them. Again a car or truck may be forced to stop in the traffic lane in the path of following vehicles. In dither instance, proper design requires that such hazards become visible at distances great enough that drivers can stop before hitting them. Further more, it is unsafe to assume that one oncoming vehicle may avoid trouble by leaving the lane in which it is traveling, for this might result in loss of control or collision with another vehicle.Stopping sight distance is made up of two elements. Thefirst is the distance traveled after the obstruction comes into view but before the driver applies his brakes. During this period of perception and reaction, the vehicle travels at its initial velocity. The second distance is consumed while the driver brakes the vehicle to a stop. The first of these two distances is dependent on the speed of the vehicle and the perception time and brake-reaction time of the operator. The second distance depends on the speed of the vehicle; thecondition of brakes, times, and roadway surface; and the alignment and grade of the highway.On two-lane highways, opportunity to pass slow-moving vehicles must be provided at intervals. Otherwise capacity decreases and accidents increase as impatient drivers risk head-on collisions by passing when it is unsafe to do so. The minimum distance ahead that must be clear to permit safe passing is called the passing sight distance. In deciding whether or not to pass another vehicle, the driver must weigh the clear distance available to him against the distance required to carry out the sequence of events that make up the passing maneuver. Among the factors that will influence his decision are the degree of caution that he exercises and the accelerating ability of his vehicle. Because humans differ markedly, passing practices, which depend largely on human judgment and behavior rather than on the laws of mechanics, vary considerably among drivers.The geometric design is to ensure highway traffic safety foundation, the highway construction projects around the other highway on geometric design, therefore, in the geometry of the highway design process, if appear any unsafe potential factors, or low levels of combination of design, will affect the whole highway geometric design quality, and the safety of the traffic to bring adverse impact. So, on the geometry of the highway design must be focus on.公路几何设计公路是供汽车或其他车辆行驶的一种线形带状结构体。

A2C01: Committee on General StructuresChairman: Donald J. FlemmingBridge EngineeringR AMANKUTTY K ANNANKUTTY, City of Minneapolis Department of Public WorksD ONALD J. F LEMMING, Minnesota Department of TransportationThe scope of the Transportation Research Board’s (TRBs) Committee on General Structures includes factors affecting the physical behavior, service life, economy, appearance, and safety of bridges and structures for transportation systems, and accounting for these factors and their interactions in design procedures and criteria. During the 20th century the United States has essentially created the safest, most efficient, and most effective highway and intermodal transportation network in the world. The challenge for the new millennium will be to further enhance this transportation network. In this paper the status of bridge engineering at the end of the 20th century in the area of general transportation structures is summarized. The focus is on bridge structure types, design aspects, new materials, aesthetic concerns, and key policy issues. An attempt is made to forecast the status of bridge engineering 20 to 30 years into the next millennium; the paper is written as though these forecasts will become a reality.BRIDGE STRUCTURE TYPESStructure types have been evolving throughout history. The evolution will continue into the future, perhaps at an accelerated rate.The driving forces behind continued advances in bridge engineering are traffic congestion and costs. In the future, just as now, the public will expect few traffic delays, if any. They will want transportation costs to be as low as possible. Computer technology will enhance traffic management so well that the public will become accustomed to flowing traffic and more aware of congestion locations. Disruptions from construction will be more obvious and even less tolerated. Given these conditions, structural types will be selected primarily on the basis of speed of construction to minimize traffic delays. Low maintenance will be a must, and the ability to widen a structure easily and quickly will be a priority in selecting a structure type.Safety and aesthetics will continue to play major roles in the selection of structure types. Keeping substructures out of the roadway clear zone will dictate longer span lengths and will keep the engineering community striving for optimal spans. Input from the public will grow to such a level that interactive design programs will become a necessity. Computer programs that automatically prepare detailed plans incorporating changes at the touch of a button will allow the public to modify or add aesthetic details right up to the point that construction begins.Transportation in the New Millennium2 Long SpanPosttensioning with high-strength materials will allow traditional concrete and steel bridges, especially box shapes, to reach continually longer spans that challenge steel truss bridges and even the shorter-span cable-stayed bridges. Cable-stayed bridges and suspension bridges will most likely continue to dominate the long-span bridge category. Long-span bridges will continue to be the most dramatic, capturing the public’s awareness with highly visible and innovative structures. Shown in Figure 1 are two impressive structures, the Sunshine Skyway Bridge and the Houston Ship Channel Bridge, which is the longest concrete box to date.Medium SpanMedium spans include spans from 50 to 200 feet and traditionally have been prestressed concrete girders and steel girders. In the future, new materials with high-performance characteristics will be developed, and the strengths of concrete and steel materials will be enhanced. Stronger materials and innovative design concepts will come together to yield much longer spans. The result will be simpler structures with fewer substructures and a reduction in overall cost. Space frame structures using steel and concrete in combination may enter this market because of ease of construction and relatively low cost. Preengineered, “out-of-the-box,” prefabricated component bridges will also become more common and will begin to challenge individualized designs. Innovations will cause greater change to the medium-span range than to the other two ranges. An innovative steel bridge that clear-spans an entire freeway is shown in Figure 2. Bridges that clear-span roadways will become popular in the future.Short SpanConcrete slabs, timber slabs, prestressed concrete shapes, and rolled steel shapes currently share the market for spans up to 50 feet. In the future, these types will be challenged by long-span culverts and preengineered, out-of-the-box, prefabricated component bridges. Shown in Figure 3 is a typical long-span culvert (44-foot span) that is starting to challenge more typical short-span structures.DESIGNDesigning bridges according to a standard specification became the norm in the 20th century. This will continue in the next century. However, the process of designing will be much different in the future because of changes in specifications, loads, testing, and computerization.SpecificationsThe specifications used for structural bridge design at the end of the 20th century are split between the American Association of State Highway and Transportation Officials (AASHTO) load factor design (LFD) specification and the load and resistance factor design (LRFD) specification, with LRFD recently being designated as the standard for the future. LFD will continue to be used for some time, but its usage will decline as LRFD becomes more widely accepted. Eventually LFD will be discontinued and LRFD will be fully adopted, which will prove to be the right course of action. The AASHTO LRFD specification will continue to evolve with new research, new design ideas, and newGeneral Structures3 materials. The LRFD method will prove to be effective and will be easily adapted to all construction materials including steel, concrete, timber, and the new high-strength plastic polymers.Acceptance of the LRFD method by the design community will not be easy because of concerns in two areas: substructure design and computer software. One goal in establishing the LRFD specification was to provide a more uniform level of reliability in every component of the structure, from substructure to superstructure. The design of substructures using the LRFD philosophy will remain in an immature state for several years because of a lack of accepted methods for analyzing and designing foundations. Only after more research and specification enhancement will the situation for substructures change. Widespread usage of LRFD will be somewhat slowed by the lack of computer software. The detailed nature of LRFD code requires that designers develop spreadsheets and other computer worksheets to complete computations efficiently. Introduction of programs such as the AASHTO OPIS computer program will help, but the full benefit of the new design code will not be realized for several years.LoadsAt the heart of the load specification is the design vehicle. The old HS-20 truck, which has been in use since 1944, is being questioned as a vehicle relevant to traffic needs of the 21st century. Early in the century, two specific questions will arise over the continued use of this vehicle. The first question is whether a different vehicle would better match the weigh-in-motion (WIM) data coming from the monitoring systems installed in roadways. Though the data are of questionable accuracy, they indicate definite trends—that truck lengths, weights, and traffic counts have increased dramatically since the arrival of the HS-20 truck.The second question is whether another vehicle would simplify computations. Various factors and loading conditions were applied to the HS-20 truck to make it fit the LRFD specification. In consideration of these two questions, a new “millennium truck” live-load configuration will be proposed. After extensive data collection, the testing and monitoring will begin.Field TestingTo help determine an appropriate design vehicle, a more comprehensive system of WIM sites will be installed. Because of advances in accuracy and durability of the equipment, dynamic load data will begin to agree with static load data. An accurate picture will then develop of actual truck axle loads and axle spacings on highway bridges. Emerging technologies such as quartz sensors and fiber-optic enhancements, along with piezo cable, will make more accurate data collection possible. Smart bridges will be the order of the new millennium because of a dramatic increase in the number of instrumented bridges. Actual stresses will be measured and tracked in much the same way as the National Weather Service tracks daily temperatures. The WIM information will be correlated with the information from the instrumented bridges. Analysis of the massive amounts of data will be possible through the use of high-capacity computers. The LRFD design load factors will be updated on the basis of the new data.Steel structures will especially benefit from instrumentation and field testing. In response to fatigue and associated problems, steel bridges will be instrumented to determine failure mechanisms, especially crack initiation at low stress ranges with large numbers ofTransportation in the New Millennium4 loading cycles. Emerging technologies will lead to the discovery of relationships that will bring about a refinement of design methods. Cost-effective retrofit applications for fatigue-prone details will lead to a change in bridge management planning for bridges with fatigue problems. As this knowledge increases, steel bridges will be replaced mostly for functional rather than for structural reasons.AnalysisComputer programs capable of analyzing large amounts of data will be developed. Key design parameters such as distribution factors, multiple presence factors, and uniform loads will be verified. Trends in loadings and the way structures respond to those loadings will be made easier to predict. This may lead to a simplification of design factors and equations, which will allow a drastic improvement in the speed of completing design computations. The design of bridges in the 21st century will be much easier and more accurate than at the end of the 20th century.Design ToolsMore and more states will cooperate in the use of standardized details, computer programs, and drafting details, making designs and plans more similar on a regional basis. Such standardization will tend to reduce construction costs for contractors and suppliers. Speed and accuracy will be increased.After many years of working separately, computer-aided engineering and computer-aided drafting will be successfully integrated. Designs and plans will be iterative and interactive, and plan preparation will be extremely cost-effective. Design engineers will be alerted by automatic specification checkers and code verifiers, enabling them to minimize design errors. More important, optimization of a design will be a keystroke away. Artificial intelligence will supplement institutional memories and expand designers’ options for obtaining real-time expert advice. The need to develop expert systems to check the accuracy and reliability of design software will be a challenge to bridge design professionals. Of course, associated with this challenge is the ever-present debate on professional liability. AutomationThe Internet and e-mail will be standards for communication between designers, fabricators, and contractors. It will become more common for designers and drafters in different states to combine efforts. Correspondence will be handled electronically, eliminating the time necessary to print and mail correspondence back and forth. Contractors and fabricators will view the final plans electronically.MaterialsMaterials have always played a key role in the evolution of bridge structures. Enhancements of the traditional materials of concrete, steel, and timber will continue, but the most revolutionary changes will occur in the areas of fiber-reinforced plastics (FRPs), high-strength and high-performance steel, high-performance concrete (HPC), and the blending of FRP and timber.General Structures5 FRPsToday, FRPs are in their infancy as bridge construction materials. However, further experimentation with various combinations of FRP materials will result in innovative and long-lasting solutions to simple and complex bridge construction issues. Experimental FRP bridge projects have shown that this material has inherent problems in deflection, material ductility, creep, reactivity with concrete and steel, and performance under long-term exposure to ultraviolet light and other environmental factors such as moisture, freeze-thaw, humidity, and external chemical attack. To help resolve these issues, material testing standards and design methodology will be developed to fit FRP material properties. A comprehensive research effort at the national level will be undertaken to make FRP a dependable, low-maintenance bridge material capable of delivering high performance over the life of a bridge structure.Collaboration of practicing designers, construction engineers, and bridge owners will make FRP a feasible and competitive alternative to conventional bridge construction materials. Universities will most likely expand their curricula to include FRP and other composite materials in their structural and material courses to prepare future bridge professionals to accept and fully utilize FRP.High-Strength and High-Performance SteelUnlike FRP, high-strength steel materials will be more readily accepted by bridge engineers. Initial acceptance will be gained because the new steel materials make it possible to reduce structural dead loads. Wider acceptance of high-strength steels will develop because of their enhanced material properties. Gains made in improving material toughness and weldability of high-strength steels will extend to all grades of steel. Design specifications will continue to be updated to deal with material performance issues such as welding, toughness, fabrication, and constructibility. The high-performance steel materials of today will become the standard for future construction.Advances in construction and experimentation with bridge types, such as space frames and innovative composite structures, will lead to further optimization of steel materials. FRP combined with high-strength steel has high potential for future bridge structures.High-performance reinforcing bars will become common in the new millennium. Composite bars with a steel core and a cladding of stainless steel or other noncorroding material will gain wide acceptance for use in concrete structures. Coupled with the use of HPC in bridge decks, the average life of such structures may approach twice the life span of similar structures built previously. Future national policies requiring life-cycle cost analysis will provide a large incentive to further develop and implement the use of innovative materials in bridge decks.HPCHPC is well on its way to becoming a conventional bridge construction material as a result of Strategic Highway Research Program research and Federal Highway Administration implementation efforts. The debate as to whether strength or permeability is the primary indicator of long-term durability of HPC will continue among practicing engineers. However, past case studies clearly demonstrate the need for permeability tests as an indicator of long-term concrete durability. The future is bright for HPC because it has good durability and strength characteristics, making it a versatile material. Currently, assessmentTransportation in the New Millennium6 of long-term durability is an after-the-fact determination, resulting in quality control/quality assurance problems, which hamper the use of performance-based specifications. Scientists and engineers will eventually develop a device that instantaneously predicts the long-term durability properties of hardened concrete by testing the concrete in an unhardened state.TimberNew processes of reinforcing wood will continue to be developed, including the combination of glued-laminated timber and FRP composites. The concept is similar to that of reinforced concrete; wood resists the compression load, while FRP composite resists tensile load. The concept will be commonly used in future timber structures. Advantages of this technology are in areas where bending strength controls the design (as with lower grades of wood). Reinforcing with FRP greatly increases the tensile capacity of the beams, which will allow lower grades of wood to be used economically in many structures. The new composite material will also be used where minimum clearance is a problem.Breakthroughs in the area of wood preservatives will continue. They will result in the development and refinement of new alternative treatment processes and procedures that will be environmentally sound with respect to application, use, and disposal of treated timber. Other MaterialsA significant future challenge for the construction industry will be the incorporation of recycled materials (including plastics), by-products, and waste materials into conventional and HPC construction materials. Future environmental regulations and lack of space to store waste products will bring this issue to a head. Significant time and financial resources will be spent in developing recycled materials into products suitable for use as construction materials.AESTHETIC CONCERNSPublic InvolvementPublic participation in the design process has increased in recent years because the public wants better aesthetic treatment of bridges, especially bridges considered neighborhood landmarks. Public participation will continue in the future and will likely increase. To facilitate the process, engineers will display plans using three-dimensional visualization technology. The public will be able to view and comment on the plans at hearings or on the Internet.Interactive DesignIncorporating public comment into the plans will require that last-minute changes be easily accommodated into the design and drafting process. Computer design and drafting programs that automatically adjust the designs and generate plans will allow for quick modifications. The latest engineering analytical skills will be needed to accommodate this technology. The emphasis on flexible design will undoubtedly require engineers to increase their aesthetic design skills and overall people skills.General Structures7 Aesthetic ProcessAesthetic treatment of structures will become so common that only the most remote sites will be unaffected. Nearly all bridges will have a detailed aesthetic treatment, or at least an aesthetic review. Extra planning time and design time will become an accepted part of the cost of a structure. The level of public attention will determine the extent of the aesthetic design process and the resources devoted to aesthetic considerations. Three levels of bridge aesthetic consideration and processes will tend to emerge: the highest level for landmark bridges with major cultural or aesthetic significance, a middle level for transportation corridors and urban structures, and a lower level for replacement bridges in rural and industrial settings.POLICY ISSUESSeveral issues of a political nature will need to be addressed by the engineering community during the next decade. They need to be studied and discussed so that a consensus among engineers is reached. Only in this way can the voice of our profession be heard by the public, who will ultimately decide policy.Design-BuildThe design-build method for project delivery will increase. Design-build specifications will become a major factor in acceptance and overall performance of the design-build method. The specifications need to require the contractor to consider both the life-cycle costs and the initial construction costs in the selection of materials and structure type. When the engineering community and the legal community work together to accomplish this, the bridge owners will become more comfortable with the design-build method and will begin to use it even more frequently. Successful design-build projects with improved speed of construction and reduced construction problems will continue to make this project delivery option attractive to owners.Life-Cycle CostsDuring the 20th century, computation of accurate life-cycle costs was difficult because of a limited amount of historical data. But in the 21st century, data collection and analysis will improve because of significant improvements in bridge management systems. The sharing of information among states will lead to a much larger database. Because of better data and better ways of handling data, life-cycle costs will be much more accurate. Life-cycle costs will become the basis for selecting structure types and aesthetic treatments.Truck Size and WeightWhether to allow larger and heavier trucks onto the roadways is a political issue that the engineering community will take very seriously. To predict as accurately as possible the consequences of such an action, extensive studies will be done to determine the relationship between the rate of deterioration and increased loadings. The resulting damage evaluation surveys, coupled with data from bridge management systems, will become the basis of a national debate on the financial effects on the transportation infrastructure.Transportation in the New Millennium8 Intermodal Design SpecificationsThe increase in funding for mass transit and the resulting proposals for light rail transit systems will bring to light the need for uniformity between the AASHTO and American Railway Engineering Association (AREA) bridge design specifications. Variations between the two codes and the lack of a definitive code for light rail transit lead to a great deal of confusion. Deciding which code applies in which circumstance will cause delays and add to the cost of design. The engineering community will sponsor studies leading to a blending of specifications and a more uniform code for the design and construction of intermodal structures.Public InvolvementThe public’s desire to be involved in design will remain strong, especially in the area of aesthetics. At times engineers will be criticized for catering too much to aesthetic interests at the expense of completing the projects on a timely basis and at normal costs. Of course, at times they will be criticized for restricting input and being insensitive to the need for aesthetically pleasing structures. Obviously, interdisciplinary teams will be developed to better facilitate the process and resolve the issues. The engineering community will learn how to better incorporate public involvement into the overall design process. CONCLUSIONSDuring the past 100 years, bridge engineers have participated in major projects that have significantly affected society. In 1900, people and freight were transported primarily by horseback and railroad. Today, the public travels by automobile and airline, and freight is carried by truck and railroad. These are sweeping changes in transportation, and bridge engineers have played a major role in them. Will the 21st century have equally great changes? Whatever the future holds, it will be an exciting and challenging time for engineers. How well structural engineers address the needs and issues discussed in this paper will determine to a great extent how much society will rely on our expertise. People demand and have a right to expect safe and cost-effective structures that meet their transportation needs.General Structures9FIGURE 1 Sunshine Skyway Bridge (top) and Houston Ship Channel Bridge (bottom).Transportation in the New Millennium10FIGURE 2 Steel bridge clear-spanning an entire freeway.FIGURE 3 Typical long-span culvert (44-foot span).。

1 INTRODUCTION1.1 BackgroundBridges are a major part of the infrastructure system in developed countries. It has been estimated that in the USA about 600,000 bridges (Dunker 1993), in the UK about 150,000 bridges (Woodward et al. 1999), in Germany about 120,000 bridges (Der Prüfingenieur 2004) and in China more then 500,000 road bridges (Yan and Shao 2008) exist. Historical stone arch bridges still represent a major part of this multitude. It has been estimated that 60 % of all railway bridges and culverts in Europe are arch bridges (UIC 2005). Recent estimations regarding the number of historical railway natural stone arch bridges and culverts in Europe lie between 200,000 (UIC 2005) and 500,000 (Harvey et al. 2007). Also in some regions in Germany about one third of all road bridges are historical arch bridges (Bothe et al. 2004, Bartuschka 1995). Dawen & Jinxiang estimate that 70 % of all bridges in China are arch bridges.The success of historical natural stone arch bridges - which are often more than 100 years old- is based on the excellent vertical load bearing behaviour (Proske et al. 2006) and the low cost of maintenance (Jackson 2004) - not only in mountainous regions. However, changes in loads or new types of loads (Hannawald et al. (2003) have measured 70 tonne trucks on German highways under regular traffic conditions and Pircher et al. have measured 100 tonne trucks) might endanger the safety of such historical structures. Obviously, bridges with an age of more than 100 years were not designed for motorcars since this mode of transportation has only been in existence for approximately 110 years. The increase of loads does not only include vertical loads but also horizontal loads in the longitudinal direction and perpendicular to the longitudinal direction of these bridges. For example, the weight of inland waterway ships in Germany has increased dramatically in the last decades, which also corresponds with increasing horizontal ship impact forces (Proske 2003).Furthermore some loads from natural processes such as gravitational processes may not have been considered during the design process of the bridges. Especially in mountain regions this Historical stone arch bridges under horizontal debris flow impact Klaudia Ratzinger and Dirk ProskeUniversity of Natural Resources and Applied Life Sciences, Vienna, AustriaABSTRACT: Many historical arch bridges are situated in Mountain regions. Such historical bridges may be exposed to several natural hazards such as flash floods with dead wood and debris flows. For example, in the year 2000 a heavy debris flow destroyed an arch bridge in Log Pod Mangartom, Slovenia and only recently, in September 2008 an arch bridge was overflowed by a debris flow. A new launched research project at the University of Natural Resources and Applied Life Sciences, Vienna tries to combine advanced numerical models of debris flows with advanced models of historical masonry arch bridges under horizontal loads. The research project starts with separate finite element modelling of different structural elements of arch bridges such as spandrel walls, the arch itself, roadway slabs, pavements and foundations under single and distributed horizontal loads. Furthermore miniaturized tests are planned to investigate the behaviour of the overall bridge under debris flow impacts. The results will be used to combine the modelling of the different structural elements considering the interaction during a horizontal loading. Furthermore this bridge model will then be combined with debris flow simulation. Also earlier works considering horizontal ship impacts against historical arch bridges will be used control. The paper will present latest research results.400 ARCH’10 – 6th International Conference on Arch Bridgesgravitational processes (debris flow impacts (Zhang 1993), rock falls (Erismann and Abele 2001) and flash floods (Eglit et al. 2007) including water born missiles or avalanches) can cause high horizontal impact loads.1.2 Historical EventsIn the year 2000, a debris flow destroyed two bridges in Log Pod Mangartom, Slovenia, one of them was a historical arch bridge. In October 2007 the historical arch bridge in Beniarbeig, Spain was destroyed by a flash flood. Similarly the Pöppelmann arch bridge in Grimma, Germany was destroyed in 2002, in 2007 a farm track and public footpath arch bridge over the River Devon collapsed.Figure 1: Debris flow impact at the Lattenbach (Proske & Hübl, 2007)Fig.1 shows an example of the historical arch bridge at the Lattenbach, before and after a debris flow event, where the bridge is nearly completely filled with debris.Due to far too expensive solutions or not applicable methods for historical arch bridges it would be very useful if models were available to estimate the load bearing capacity of historical masonry arch bridges for horizontal loads perpendicular to the longitudinal direction.Since intensive research was carried out for the development of models dealing with vertical loads for historical arch bridges, there is an unsurprising lack of models capable for horizontal impact forces against the superstructure. This might be mainly based on the assumption that horizontal loads are not of major concern for this bridge type due to the great death load of such bridges.The goal of this investigation is the development of engineering models describing the behaviour of historical natural stone arch bridges under horizontal forces, mainly debris flow impacts, focused strongly on the behaviour of the superstructure and based on numerical simulations using discrete element models and finite element models.2 INNOVATIVE ASPECT AND GOALS2.1 Innovative AspectsThe conservation of historical arch bridges is not only an issue of the preservation of cultural heritage but is also an economic issue since the number of historical bridges in developed countries is huge (Proske 2009). Compared to vertical load cases no models currently exist for horizontal loads perpendicular to the longitudinal direction. It is therefore required to develop new models dealing with these capacious horizontal loads which include all types of gravitational hazards like avalanches, debris flow, rock falls or flood borne missiles or impacts from modes of transportation. First works related to the development of debris flow design impact forces and the behaviour of arch bridges under such an impact have started already 2007 at the Institute of Alpine Mountain Risk Engineering at the University of Natural Resources and Applied Life Sciences, Vienna (see Fig.2)Klaudia Ratzinger and Dirk Proske 401Figure 2 : Examples of the structural behaviour under impacts (left against the pier, right against the arch itself) (Proske and Hübl 2007)This investigation and its results regarding debris flow impact will flow into the development of the new Austrian code of practice Ö-Norm 24801 for the design of structures exposed to debris flow impacts as well.2.2 GoalTo develop load bearing behavior models of historical natural stone arch bridges under horizontal loads perpendicular to the longitudinal direction, a realistic model of debris flow against solid structures has to be implemented indifferent programs. Separate finite element modelling of different structural elements of arch bridges such as spandrel walls, the arch itself, roadway slabs, pavements and foundations under single and distributed horizontal loads are part of this investigation. Furthermore miniaturized tests are part of the project to investigate the behaviour of the overall bridge under debris flow impacts. The results will be used to combine the modelling of the different structural elements considering the interaction during a horizontal loading. Furthermore this bridge model will then be combined with debris flow simulation. Also earlier works considering horizontal ship impacts against historical arch bridges will be used. Therefore three models of historical arch bridges are developed:(1) Discrete element program model (PFC),(2) Explicit finite difference program model (FLAC),(3) Finite element program model (ANSYS, ATENA).The first and second models are developed to simulate an overall debris flow impact scenario, whereas the third model is used to investigate details, such as single force against a spandrel wall, single force against parapets, friction at the arch, single impact force against the arch. Results from the impact simulation against the superstructure should give an answer, whether the complete process can be separated into forces acting on the bridge. This reference force (force-time-function) will then be applied on the finite element models.The numerical modelling will be accompanied by testing to permit validation of the models. The tests will be carried out as miniaturized tests (scale about 1:20…50). Already miniaturized tests of the impact of debris flows against debris flow barriers were already carried out at the Institute of Mountain Risk Engineering (Proske et al. 2008, Hübl & Holzinger 2003,Fig.3). Based on this experience, miniaturized arch bridges (span about 40 to 50 cm) will be constructed and investigated. Also single parts of the arch structure will be investigated in testing machines, such as behaviour of a pure arch under a horizontal load. Since the machine cannot be turned, force redirection mechanisms will be used to allow the application of a standard compression test machine from the University of Natural Resources and Applied Life Sciences, Vienna.402 ARCH’10 – 6th International Conference on Arch BridgesFigure 3 : Side view and view from above of the used debris flow impact measurement test set-up (Hübl & Holzinger 2003)3 CALCULATIONS3.1 Discrete element methodsDiscrete element modeling can be done by usingPFC3D (Particle Flow Code 3D) which is used in analysis, testing and research in any field where the interaction of many discrete objects exhibiting large-strain and/or fracturing is required. By using the program PFC3D, materials can be modeled as either bonded (cemented) or granular assemblies of particle s.3.2 Finite element methodsThe finite element method (FEM) is one of the most powerful computer methods for solving partial differential equations applied on complex shapes and with complex boundary conditions.A mesh made of a complex system of points is programmed containing material and structural properties defining the reaction of the structure to certain loading conditions. Nodes are assigned at a certain density throughout the material depending on the anticipated stress levels of a certain area.Two types of analysis are commonly used: 2-D modelling and 3-D modelling. 2-D modelling allows the analysis to be run on a normal computer but tends to yield less accurate results whereas 3-D modelling shows more accurate results.For this investigation two FEM programs are used:(1) ANSYS(2) ATENAANSYS is the leading finite element analysis package for numerically solving a wide varietyof mechanical problems in 2D and 3D. By using ANSYS, the analysis can be done linear and non-linear, is applicable to static and dynamic structural analysis, heat transfer and fluid problems as well as acoustic and electromagnetic problems.The ATENA program is determined for nonlinear finite element analysis of structures, offers tools specially designed for computer simulation of concrete and reinforced concrete structural behaviour. Moreover, structures from other materials, such as soils, metals etc. can be treated as well.In the first step finite element methods are used to simulate the behaviour of historical natural stone arch bridges under an impact. Required data for the debris flow models are taken from the database of the Institute of Mountain Risk Engineering as well from the Austrian RailwayService (ÖBB).Klaudia Ratzinger and Dirk Proske 403The basic requirements for an appropriate assessment of stone arch bridges are:(1) Choice of a realistic calculation model(2) Consideration of geometrical and material nonlinearities(3) Using applicable material models for masonry(4) Adapted evidence based on the chosen material models.Therefore, a simplified arch bridge model with various lengths (L), rising of the vault (r) and thickness of the stone arch (t) was chosen (Fig.4) – first by using a two-dimensional model –with the purpose to investigate the importance of geometrical properties to their structural performance and to demonstrate different results. Further models are in process and will be implemented in the FEM programs as well.Figure 4 : FE model of a simplified arch bridge (Becke, 2005)4 CONCLUSIONSThis research project launched by the University of Natural Resources and Applied Life Sciences, Vienna combines advanced numerical models of debris flows with advanced models of historical masonry arch bridges under horizontal loads. It started with the implementation of separate finite element modelling of different structural elements of arch bridges. Furthermore miniaturized tests will be done in 2010 to investigate the behaviour of the overall bridge under debris flow impacts. The results will be used to combine the modelling of the different structural elements considering the interaction during a horizontal loading and the bridge model will be combined with debris flow simulation.Last but not least recommendation values for such bridge types should be given by this investigation that may include further formulas considering for example the adaptation of masonry stiffness or strength values.1介绍1．1背景桥梁是发达国家的基础设施系统的一个主要部分。

附录一英文翻译原文AUTOMATIC DEFLECTION AND TEMPERATURE MONITORING OFA BALANCED CANTILEVER CONCRETE BRIDGEby Olivier BURDET, Ph.D.Swiss Federal Institute of Technology, Lausanne, SwitzerlandInstitute of Reinforced and Prestressed Concrete SUMMARYThere is a need for reliable monitoring systems to follow the evolution of the behavior of structures over time.Deflections and rotations are values that reflect the overall structure behavior. This paper presents an innovative approach to the measurement of long-term deformations of bridges by use of inclinometers. High precision electronic inclinometers can be used to follow effectively long-term rotations without disruption of the traffic. In addition to their accuracy, these instruments have proven to be sufficiently stable over time and reliable for field conditions. The Mentue bridges are twin 565 m long box-girder post-tensioned concrete highway bridges under construction in Switzerland. The bridges are built by the balanced cantilever method over a deep valley. The piers are 100 m high and the main span is 150 m. A centralized data acquisition system was installed in one bridge during its construction in 1997. Every minute, the system records the rotation and temperature at a number of measuring points. The simultaneous measurement of rotations and concrete temperature at several locations gives a clear idea of the movements induced by thermal conditions. The system will be used in combination with a hydrostatic leveling setup to follow the long-term behavior of the bridge. Preliminary results show that the system performs reliably and that the accuracy of the sensors is excellent.Comparison of the evolution of rotations and temperature indicate that the structure responds to changes in air temperature rather quickly.1.BACKGROUNDAll over the world, the number of structures in service keeps increasing. With the development of traffic and the increased dependence on reliable transportation, it is becoming more and more necessary to foresee and anticipate the deterioration of structures. In particular,for structures that are part of major transportation systems, rehabilitation works need to be carefully planned in order to minimize disruptions of traffic. Automatic monitoring of structures is thus rapidly developing.Long-term monitoring of bridges is an important part of this overall effort to attempt to minimize both the impact and the cost of maintenance and rehabilitation work of major structures. By knowing the rate of deterioration of a given structure, the engineer is able to anticipate and adequately define the timing of required interventions. Conversely, interventions can be delayed until the condition of the structure requires them, without reducing the overall safety of the structure.The paper presents an innovative approach to the measurement of long-term bridge deformations. The use of high precision inclinometers permits an effective, accurate and unobtrusive following of the long-term rotations. The measurements can be performed under traffic conditions. Simultaneous measurement of the temperature at several locations gives a clear idea of the movements induced by thermal conditions and those induced by creep and shrinkage. The system presented is operational since August 1997 in the Mentue bridge, currently under construction in Switzerland. The structure has a main span of 150 m and piers 100 m high.2. LONG-TERM MONITORING OF BRIDGESAs part of its research and service activities within the Swiss Federal Institute of Technology in Lausanne (EPFL), IBAP - Reinforced and Prestressed Concrete has been involved in the monitoring of long-time deformations of bridges and other structures for over twenty-five years [1, 2, 3, 4]. In the past, IBAP has developed a system for the measurement of long-term deformations using hydrostatic leveling [5, 6]. This system has been in successful service in ten bridges in Switzerland for approximately ten years [5,7]. The system is robust, reliable and sufficiently accurate, but it requires human intervention for each measurement, and is not well suited for automatic data acquisition. One additional disadvantage of this system is that it is only easily applicable to box girder bridges with an accessible box.Occasional continuous measurements over periods of 24 hours have shown that the amplitude of daily movements is significant, usually amounting to several millimeters over a couple of hours. This is exemplified in figure 1, where measurements of the twin Lutrive bridges, taken over a period of several years before and after they were strengthened by post-tensioning, areshown along with measurements performed over a period of 24 hours. The scatter observed in the data is primarily caused by thermal effects on the bridges. In the case of these box-girder bridges built by the balanced cantilever method, with a main span of 143.5 m, the amplitude of deformations on a sunny day is of the same order of magnitude than the long term deformation over several years.Instantaneous measurements, as those made by hydrostatic leveling, are not necessarily representative of the mean position of the bridge. This occurs because the position of the bridge at the time of the measurement is influenced by the temperature history over the past several hours and days. Even if every care was taken to perform the measurements early in the morning and at the same period every year, it took a relatively long time before it was realized that the retrofit performed on the Lutrive bridges in 1988 by additional post-tensioning [3, 7,11] had not had the same effect on both of them.Figure 1: Long-term deflections of the Lutrive bridges, compared to deflections measured in a 24-hour period Automatic data acquisition, allowing frequent measurements to be performed at an acceptable cost, is thus highly desirable. A study of possible solutions including laser-based leveling, fiber optics sensors and GPS-positioning was performed, with the conclusion that, provided that their long-term stability can be demonstrated, current types of electronic inclinometers are suitable for automatic measurements of rotations in existing bridges [8].3. MENTUE BRIDGESThe Mentue bridges are twin box-girder bridges that will carry the future A1 motorway from Lausanne to Bern. Each bridge, similar in design, has an overall length of approximately 565 m, and a width of 13.46 m, designed to carry two lanes of traffic and an emergency lane. The bridges cross a deep valley with steep sides (fig. 2). The balanced cantilever design results from a bridge competition. The 100 m high concrete piers were built using climbing formwork, after which the construction of the balanced cantilever started (fig. 3).4. INCLINOMETERSStarting in 1995, IBAP initiated a research project with the goal of investigating the feasibility of a measurement system using inclinometers. Preliminary results indicated that inclinometers offer several advantages for the automatic monitoring of structures. Table 1 summarizes the main properties of the inclinometers selected for this study.One interesting property of measuring a structure’s rotations, is that, for a given ratio of maximum deflection to span length, the maximum rotation is essentially independent from its static system [8]. Since maximal allowable values of about 1/1,000 for long-term deflections under permanent loads are generally accepted values worldwide, developments made for box-girder bridges with long spans, as is the case for this research, are applicable to other bridges, for instance bridges with shorter spans and other types of cross-sections. This is significant because of the need to monitor smaller spans which constitute the majority of all bridges.The selected inclinometers are of type Wyler Zerotronic ±1°[9]. Their accuracy is 1 microradian (μrad), which corresponds to a rotation of one millimeter per kilometer, a very small value. For an intermediate span of a continuous beam with a constant depth, a mid-span deflection of 1/20,000 would induce a maximum rotation of about 150 μrad, or 0.15 milliradians (mrad).One potential problem with electronic instruments is that their measurements may drift overtime. To quantify and control this problem, a mechanical device was designed allowing the inclinometers to be precisely rotated of 180° in an horizontal plane (fig. 4). The drift of each inclinometer can be very simply obtained by comparing the values obtained in the initial and rotated position with previously obtained values. So far, it has been observed that the type of inclinometer used in this project is not very sensitive to drifting.5. INSTRUMENTATION OF THE MENTUE BRIDGESBecause a number of bridges built by the balanced cantilever method have shown an unsatisfactory behavior in service [2, 7,10], it was decided to carefully monitor the evolution of the deformations of the Mentue bridges. These bridges were designed taking into consideration recent recommendations for the choice of the amount of posttensioning [7,10,13]. Monitoring starting during the construction in 1997 and will be pursued after the bridges are opened to traffic in 2001. Deflection monitoring includes topographic leveling by the highway authorities, an hydrostatic leveling system over the entire length of both bridges and a network of inclinometers in the main span of the North bridge. Data collection iscoordinated by the engineer of record, to facilitate comparison of measured values. The information gained from these observations will be used to further enhance the design criteria for that type of bridge, especially with regard to the amount of post-tensioning [7, 10, 11, 12, 13].The automatic monitoring system is driven by a data acquisition program that gathers and stores the data. This system is able to control various types of sensors simultaneously, at the present time inclinometers and thermal sensors. The computer program driving all the instrumentation offers a flexible framework, allowing the later addition of new sensors or data acquisition systems. The use of the development environment LabView [14] allowed to leverage the large user base in the field of laboratory instrumentation and data analysis. The data acquisition system runs on a rather modest computer, with an Intel 486/66 Mhz processor, 16 MB of memory and a 500 MB hard disk, running Windows NT. All sensor data are gathered once per minute and stored in compressed form on the hard disk. The system is located in the box-girder on top of pier 3 (fig. 5). It can withstand severe weather conditions and will restart itself automatically after a power outage, which happened frequently during construction.6. SENSORSFigure 5(a) shows the location of the inclinometers in the main span of the North bridge. The sensors are placed at the axis of the supports (①an d⑤), at 1/4 and 3/4 (③an d④) of the span and at 1/8 of the span for②. In the cross section, the sensors are located on the North web, at a height corresponding to the center of gravity of the section (fig.5a). The sensors are all connected by a single RS-485 cable to the central data acquisition system located in the vicinity of inclinometer ①. Monitoring of the bridge started already during its construction. Inclinometers①,②and③were installed before the span was completed. The resulting measurement were difficult to interpret, however, because of the wide variations of angles induced by the various stages of this particular method of construction.The deflected shape will be determined by integrating the measured rotations along the length of the bridge (fig.5b). Although this integration is in principle straightforward, it has been shown [8, 16] that the type of loading and possible measurement errors need to be carefully taken into account.Thermal sensors were embedded in concrete so that temperature effects could be taken into account for the adjustment of the geometry of the formwork for subsequent casts. Figure 6 shows the layout of thermal sensors in the main span. The measurement sections are located at the same sections than the inclinometers (fig. 5). All sensors were placed in the formwork before concreting and were operational as soon as the formwork was removed, which was required for the needs of the construction. In each section, seven of the nine thermal sensor (indicated in solid black in fig. 6) are now automatically measured by the central data acquisition system.7. RESULTSFigure 7 shows the results of inclinometry measurements performed from the end ofSeptember to the third week of November 1997. All inclinometers performed well during that period. Occasional interruptions of measurement, as observed for example in early October are due to interruption of power to the system during construction operations. The overall symmetry of results from inclinometers seem to indicate that the instruments drift is not significant for that time period. The maximum amplitude of bridge deflection during the observed period, estimated on the basis of the inclinometers results, is around 40 mm. More accurate values will be computed when the method of determination ofdeflections will have been further calibrated with other measurements. Several periods of increase, respectively decrease, of deflections over several days can be observed in the graph. This further illustrates the need for continuous deformation monitoring to account for such effects. The measurement period was .busy. in terms of construction, and included the following operations: the final concrete pours in that span, horizontal jacking of the bridge to compensate some pier eccentricities, as well as the stressing of the continuity post-tensioning, and the de-tensioning of the guy cables (fig. 3). As a consequence, the interpretation of these measurements is quite difficult. It is expected that further measurements, made after the completion of the bridge, will be simpler to interpret.Figure 8 shows a detail of the measurements made in November, while figure.9 shows temperature measurements at the top and bottom of the section at mid-span made during that same period. It is clear that the measured deflections correspond to changes in the temperature. The temperature at the bottom of the section follows closely variations of the air temperature(measured in the shade near the north web of the girder). On the other hand, the temperature at the top of the cross section is less subject to rapid variations. This may be due to the high elevation of the bridge above ground, and also to the fact that, during the measuring period, there was little direct sunshine on the deck. The temperature gradient between top and bottom of the cross section has a direct relationship with short-term variations. It does not, however, appear to be related to the general tendency to decrease in rotations observed in fig. 8.8. FUTURE DEVELOPMENTSFuture developments will include algorithms to reconstruct deflections from measured rotations. To enhance the accuracy of the reconstruction of deflections, a 3D finite element model of the entire structure is in preparation [15]. This model will be used to identify the influence on rotations of various phenomena, such as creep of the piers and girder, differential settlements, horizontal and vertical temperature gradients or traffic loads.Much work will be devoted to the interpretation of the data gathered in the Mentue bridge. The final part of the research project work will focus on two aspects: understanding the very complex behavior of the structure, and determining the most important parameters, to allow a simple and effective monitoring of the bridges deflections.Finally, the research report will propose guidelines for determination of deflections from measured rotations and practical recommendations for the implementation of measurement systems using inclinometers. It is expected that within the coming year new sites will be equipped with inclinometers. Experiences made by using inclinometers to measure deflections during loading tests [16, 17] have shown that the method is very flexible and competitive with other high-tech methods.As an extension to the current research project, an innovative system for the measurement of bridge joint movement is being developed. This system integrates easily with the existing monitoring system, because it also uses inclinometers, although from a slightly different type.9. CONCLUSIONSAn innovative measurement system for deformations of structures using high precision inclinometers has been developed. This system combines a high accuracy with a relatively simple implementation. Preliminary results are very encouraging and indicate that the use of inclinometers to monitor bridge deformations is a feasible and offers advantages. The system is reliable, does not obstruct construction work or traffic and is very easily installed. Simultaneous temperature measurements have confirmed the importance of temperature variations on the behavior of structural concrete bridges.10. REFERENCES[1] ANDREY D., Maintenance des ouvrages d’art: méthodologie de surveillance, PhD Dissertation Nr 679, EPFL, Lausanne, Switzerland, 1987.[2] BURDET O., Load Testing and Monitoring of Swiss Bridges, CEB Information Bulletin Nr 219, Safety and Performance Concepts, Lausanne, Switzerland, 1993.[3] BURDET O., Critères pour le choix de la quantitéde précontrainte découlant de l.observation de ponts existants, CUST-COS 96, Clermont-Ferrand, France, 1996.[4] HASSAN M., BURDET O., FAVRE R., Combination of Ultrasonic Measurements and Load Tests in Bridge Evaluation, 5th International Conference on Structural Faults and Repair, Edinburgh, Scotland, UK, 1993.[5] FAVRE R., CHARIF H., MARKEY I., Observation à long terme de la déformation des ponts, Mandat de Recherche de l’OFR 86/88, Final Report, EPFL, Lausanne, Switzerland, 1990.[6] FAVRE R., MARKEY I., Long-term Monitoring of Bridge Deformation, NATO Research Workshop, Bridge Evaluation, Repair and Rehabilitation, NATO ASI series E: vol. 187, pp. 85-100, Baltimore, USA, 1990.[7] FAVRE R., BURDET O. et al., Enseignements tirés d’essais de charge et d’observations à long terme pour l’évaluation des ponts et le choix de la précontrainte, OFR Report, 83/90, Zürich, Switzerland, 1995.[8] DAVERIO R., Mesures des déformations des ponts par un système d’inclinométrie,Rapport de maîtrise EPFL-IBAP, Lausanne, Switzerland, 1995.[9] WYLER AG., Technical specifications for Zerotronic Inclinometers, Winterthur, Switzerland, 1996.[10] FAVRE R., MARKEY I., Generalization of the Load Balancing Method, 12th FIP Congress, Prestressed Concrete in Switzerland, pp. 32-37, Washington, USA, 1994.[11] FAVRE R., BURDET O., CHARIF H., Critères pour le choix d’une précontrainte: application au cas d’un renforcement, "Colloque International Gestion des Ouvrages d’Art: Quelle Stratégie pour Maintenir et Adapter le Patrimoine, pp. 197-208, Paris, France, 1994. [12] FAVRE R., BURDET O., Wahl einer geeigneten Vorspannung, Beton- und Stahlbetonbau, Beton- und Stahlbetonbau, 92/3, 67, Germany, 1997.[13] FAVRE R., BURDET O., Choix d’une quantité appropriée de précontrain te, SIA D0 129, Zürich, Switzerland, 1996.[14] NATIONAL INSTRUMENTS, LabView User.s Manual, Austin, USA, 1996.[15] BOUBERGUIG A., ROSSIER S., FAVRE R. et al, Calcul non linéaire du béton arméet précontraint, Revue Français du Génie Civil, vol. 1 n° 3, Hermes, Paris, France, 1997. [16] FEST E., Système de mesure par inclinométrie: développement d’un algorithme de calcul des flèches, Mémoire de maîtrise de DEA, Lausanne / Paris, Switzerland / France, 1997.[17] PERREGAUX N. et al., Vertical Displacement of Bridges using the SOFO System: a Fiber Optic Monitoring Method for Structures, 12th ASCE Engineering Mechanics Conference, San Diego, USA, to be published,1998.译文平衡悬臂施工混凝土桥挠度和温度的自动监测作者Olivier BURDET博士瑞士联邦理工学院，洛桑，瑞士钢筋和预应力混凝土研究所概要：我们想要跟踪结构行为随时间的演化，需要一种可靠的监测系统。

外文资料The Tenth East Asia-Pacific Conference on Structural Engineering and ConstructionAugust 3-5, 2006, Bangkok, ThailandStructural Rehabilitation of Concrete Bridges with CFRPComposites-Practical Details and ApplicationsRiyad S. ABOUTAHA1, and Nuttawat CHUTARAT2 ABSTRACT: Many old existing bridges are still active in the various highway transportation networks, carrying heavier and faster trucks, in all kinds of environments. Water, salt, and wind have caused damage to these old bridges, and scarcity of maintenance funds has aggravated their conditions. One attempt to restore the original condition; and to extend the service life of concrete bridges is by the use of carbon fiber reinforced polymer (CFRP) composites. There appear to be very limited guides on repair of deteriorated concrete bridges with CFRP composites. In this paper, guidelines for nondestructive evaluation (NDE), nondestructive testing (NDT), and rehabilitation of deteriorated concrete bridges with CFRP composites are presented. The effect of detailing on ductility and behavior of CFRP strengthened concrete bridges are also discussed and presented.KEYWORDS: Concrete deterioration, corrosion of steel, bridge rehabilitation, CFRP composites.1 IntroductionThere are several destructive external environmental factors that limit the service life of bridges. These factors include but not limited to chemical attacks, corrosion of reinforcing steel bars, carbonation of concrete, and chemical reaction of aggregate. If bridges were not well maintained, these factors may lead to a structural deficiency, which reduces the margin of safety, and may result in structural failure. In order to rehabilitate and/or strengthen deteriorated existing bridges, thorough evaluation should be conducted. The purpose of the evaluation is to assess the actual condition of any existing bridge, and generally to examine the remaining strength and load carry capacity of the bridge.1 Associate Professor, Syracuse University, U.S.A.2 Lecturer, Sripatum University, Thailand.One attempt to restore the original condition, and to extend the service life of concrete bridges is by the use of carbon fiber reinforced polymer (CFRP) composites.In North America, Europe and Japan, CFRP has been extensively investigated and applied. Several design guides have been developed for strengthening of concrete bridges with CFRP composites. However, there appear to be very limited guides on repair of deteriorated concrete bridges with CFRP composites. This paper presents guidelines for repair of deteriorated concrete bridges, along with proper detailing. Evaluation, nondestructive testing, and rehabilitation of deteriorated concrete bridges with CFRP composites are presented. Successful application of CFRP composites requires good detailing as the forces developed in the CFRP sheets are transferred by bond at the concrete-CFRP interface. The effect of detailing on ductility and behavior of CFRP strengthened concrete bridges will also be discussed and presented.2 Deteriorated Concrete BridgesDurability of bridges is of major concern. Increasing number of bridges are experiencing significant amounts of deterioration prior to reaching their design service life. This premature deterioration considered a problem in terms of the structural integrity and safety of the bridge. In addition, deterioration of a bridge has a considerable magnitude of costs associated with it. In many cases, the root of a deterioration problem is caused by corrosion of steel reinforcement in concrete structures. Concrete normally acts to provide a high degree of protection against corrosion of the embedded reinforcement. However, corrosion will result in those cases that typically experience poor concrete quality, inadequate design or construction, and harsh environmental conditions. If not treated a durability problem, e.g. corrosion, may turn into a strength problem leading to a structural deficiency, as shown in Figure1.Figure1 Corrosion of the steel bars is leading to a structural deficiency3 Non-destructive Testing of Deteriorated Concrete Bridge PiersIn order to design a successful retrofit system, the condition of the existing bridge should be thoroughly evaluated. Evaluation of existing bridge elements or systems involves review of the asbuilt drawings, as well as accurate estimate of the condition of the existing bridge, as shown in Figure2. Depending on the purpose of evaluation, non-destructive tests may involve estimation of strength, salt contents, corrosion rates, alkalinity in concrete, etc.Figure2 Visible concrete distress marked on an elevation of a concrete bridge pier Although most of the non-destructive tests do not cause any damage to existing bridges, some NDT may cause minor local damage (e.g. drilled holes & coring) that should be repaired right after the NDT. These tests are also referred to as partial destructive tests but fall under non-destructive testing.In order to select the most appropriate non-destructive test for a particular case, thepurpose of the test should be identified. In general, there are three types of NDT to investigate: (1) strength, (2) other structural properties, and (3) quality and durability. The strength methods may include; compressive test (e.g. core test/rebound hammer/ ultrasonic pulse velocity), surface hardness test (e.g. rebound hammer), penetration test (e.g. Windsor probe), and pullout test (anchor test).Other structural test methods may include; concrete cover thickness (cover-meter), locating rebars (rebar locator), rebar size (some rebar locators/rebar data scan), concrete moisture (acquameter/moisture meter), cracking (visual test/impact echo/ultrasonic pulse velocity), delamination (hammer test/ ultrasonic pulse velocity/impact echo), flaws and internal cracking (ultrasonic pulse velocity/impact echo), dynamic modulus of elasticity (ultrasonic pulse velocity), Possion’s ratio (ultrasonic pulse velocity), thickness of concrete slab or wall (ultrasonic pulse velocity), CFRP debonding (hammer test/infrared thermographic technique), and stain on concrete surface (visual inspection).Quality and durability test methods may include; rebar corrosion rate –field test, chloride profile field test, rebar corrosion analysis, rebar resistivity test, alkali-silica reactivity field test, concrete alkalinity test (carbonation field test), concrete permeability (field test for permeability).4 Non-destructive Evaluation of Deteriorated Concrete Bridge PiersThe process of evaluating the structural condition of an existing concrete bridge consists of collecting information, e.g. drawings and construction & inspection records, analyzing NDT data, and structural analysis of the bridge. The evaluation process can be summarized as follows: (1) Planning for the assessment, (2) Preliminary assessment, which involves examination of available documents, site inspection, materials assessment, and preliminary analysis, (3) Preliminary evaluation, this involves: examination phase, and judgmental phase, and finally (4) the cost-impact study.If the information is insufficient to conduct evaluation to a specific required level, then a detailed evaluation may be conducted following similar steps for the above-mentioned preliminary assessment, but in-depth assessment. Successful analytical evaluation of an existing deteriorated concrete bridge should consider the actual condition of the bridge and level of deterioration of various elements. Factors, e.g. actual concrete strength, level of damage/deterioration, actual size of corroded rebars, loss of bond between steel and concrete, etc. should be modeled into a detailed analysis. If such detailed analysis is difficult to accomplish within a reasonable period of time, thenevaluation by field load testing of the actual bridge in question may be required.5 Bridge Rehabilitation with CFRP CompositesApplication of CFRP composite materials is becoming increasingly attractive to extend the service life of existing concrete bridges. The technology of strengthening existing bridges with externally bonded CFRP composites was developed primarily in Japan (FRP sheets), and Europe (laminates). The use of these materials for strengthening existing concrete bridges started in the 1980s, first as a substitute to bonded steel plates, and then as a substitute for steel jackets for seismic retrofit of bridge columns. CFRP Composite materials are composed of fiber reinforcement bonded together with a resin matrix. The fibers provide the composite with its unique structural properties. The resin matrix supports the fibers, protect them, and transfer the applied load to the fibers through shearing stresses. Most of the commercially available CFRP systems in the construction market consist of uniaxial fibers embedded in a resin matrix, typically epoxy. Carbon fibers have limited ultimate strain, which may limit the deformability of strengthened members. However, under traffic loads, local debonding between FRP sheets and concrete substrate would allow for acceptable level of global deformations before failure.CFRP composites could be used to increase the flexural and shear strength of bridge girders including pier cap beams, as shown in Figure3. In order to increase the ductility of CFRP strengthened concrete girders, the longitudinal CFRP composite sheets used for flexural strengthening should be anchored with transverse/diagonal CFRP anchors to prevent premature delamination of the longitudinal sheets due to localized debonding at the concrete surface-CFRP sheet interface. In order to prevent stress concentration and premature fracture of the CFRP sheets at the corners of concrete members, the corners should be rounded at 50mm (2.0 inch) radius, as shown in Figure3.Deterioration of concrete bridge members due to corrosion of steel bars usually leads in loss of steel section and delamination of concrete cover. As a result, such deterioration may lead to structural deficiency that requires immediate attention. Figure4 shows rehabilitation of structurally deficient concrete bridge pier using CFRP composites.Figure3 Flexural and shear strengthening of concrete bridge pier with FRP compositesFigure4 Rehabilitation of deteriorated concrete bridge pier with CFRP composites6 Summary and ConclusionsEvaluation, non-destructive testing and rehabilitation of deteriorated concrete bridges were presented. Deterioration of concrete bridge components due to corrosion may lead to structural deficiencies, e.g. flexural and/or shear failures. Application of CFRP composite materials is becoming increasingly attractive solution to extend the service life of existing concrete bridges. CFRP composites could be utilized for flexural and shear strengthening, as well as for restoration of deteriorated concrete bridge components. The CFRP composite sheets should be well detailed to prevent stress concentration and premature fracture or delamination. For successful rehabilitation of concrete bridges in corrosive environments, a corrosion protection system should be used along with the CFRP system.第十届东亚太结构工程设计与施工会议2006年8月3-5号，曼谷，泰国碳纤维复合材料修复混凝土桥梁结构的详述及应用Riyad S. ABOUTAHA1, and Nuttawat CHUTARAT2摘要：在各式各样的公路交通网络中，许多现有的古老桥梁，在各种恶劣的环境下，如更重的荷载和更快的车辆等条件下，依然在被使用着。

Design of reinforced concrete bridgesP. Jackson Giord and PartnersThe shortest span reinforced concrete decks are built as solid slabs. These may be supported on bearings although, due to durability issues with expansion joints and bearings, it is usually preferable to cast them integral with in-situ abutments or place them as part of pre cast box culverts. As the span increases, the optimum form of construction changes to voided slab or beam and slab then box girder bridges. Open spandrel arches enable relatively long spans, more commonly built in steel or prestressed concrete, to be built efficiently in reinforced concrete. Reinforced concrete is also used for deck slabs and substructures for bridges with main elements of steel or prestressed concrete. The key design criteria and checks required by codes are the same regardless of the form of construction. These are for ultimate strength in flexure, shear and torsion and for serviceability issues including crack widths and service stresses. For elements with significant live load ratios, reinforcement fatigue may sometimes also have to be checked. IntroductionMost modern small bridges are of reinforced concrete construction and nearly all modern bridges contain some elements of reinforced concrete (RC). In this chapter, the design of reinforced concrete bridge superstructures is considered and some aspects of the design criteria for reinforced concrete, which are also relevant to other reinforced concrete substructures and reinforced concrete parts of bridges with steel or prestressed main elements, are reviewed.Some specific aspects which are most often relevant to deck slabs in bridges with prestressed or steel beams will be considered in the section on beam and slab bridges.In situ reinforced concrete construction has the great advantage of simplicity; formwork is placed, reinforcement fixed and concrete poured and the structure is then com-plete. In modern practice, precast bridge elements are usually prestressed. For smaller elements, this is because pretensioning on long line beds is a convenient method of providing the steel. For larger structures, post-tensioning provides the most convenient way of fixing manageable sized elements together. The result is that, with some exceptions which will be discussed, purely reinforced concrete bridges are usually cast in situ.In the following, the various types of RC bridge are considered and the design criteria for reinforced concrete are then reviewed.Solid slab bridgesSingle spansThe solid slab is the simplest form of reinforced concrete bridge deck. Ease of construction resulting from the sim-plicity makes this the most economic type for short span structures. Solid slabs also have good distribution properties which makes them efficient at carrying concentrated movable loads such as wheel loads for highway bridges. However, above a span of around 10m the deadweight starts to become excessive, making other forms of construction more economic.Solid slab bridges can be simply supported on bearings or built into the abutments. Until recently, bridge engineers tended to be quite pedantic about providing for expansion and even bridges as short as 9m span were often provided with bearings and expansion joints. However, bearings and expansion joints have proved to be among the most troublesome components of bridges. In particular, deterior-ation of substructures due to water leaking through expan-sion joints has been common especially in bridges carrying roads where de-icing salt is used.Recently, the fashion has changed back to designing bridges that are cast integral with theabutments or bank seats (Department of Transport, 1995). Apart from the durability advantages, this can lead to saving in the deck due to the advantage of continuity. On short span bridges with relatively high abutment walls, being able to use the deck to prop the abutments can also lead to significant savings in the abutments. However, this normally depends on being able to build the deck before backfilling behind the abutments. When assumptions about construction approach such as this are made in design, it is important that they should be properly conveyed to the contractor, normally by stating them on the drawings.A feature of the design of integral bridges which has not always been appreciated is that, because the deck is not structurally isolated from the substructure, the stress state in the deck is dependent on the soil properties. This inevitably means that the analysis is less ‘accurate’than in conventional structures. Neither the normal at-rest pressure behind abutments nor the resistance to movement is ever very accurately known. It might be argued that, because of this, designs should be done for both upper and lower bounds to soil properties. In practice, this is not generally done and the design criteria used have sufficient reserve so that this does not lead to problems.Depending on the ground conditions, span and obstacle crossed, the abutments of asingle-span bridge may be separate or may be joined to form a complete box. Such box type structures have the advantage that they can be built without piles even in very poor ground, as the bearing pressure is low. Since the box structure is likely to be lighter than the displaced fill, the net bearing pressure is often negative. This can lead to problems in made ground as the embankment either side of the box may settle much more than the box, leading to problems with vertical align-ment and damage to the surfacing or rails over the bridge.RC slab bridges are normally cast in situ. An exception is very short span shallower structures (typically up to some 6m span and 3.6m clear height) which can be most eco-nomically precast effectively complete as box culverts, leav-ing only parapets and, where required, wing walls to cast in situ. This form of construction is most commonly used for conveying watercourses under embankments but can be used for footway and cycletracks.In situ construction is very convenient for greenfield sites and for crossing routes that can be diverted. It is less con-venient for crossing under or over live routes. For the latter, spanning formwork can be used if there is sufficient headroom. However, in many cases beam bridges are more convenient and the precast beams will normally be pre-stressed. RC box type structures can, however, be installed under live traffic. They can be pushed under embankments. The issues are considered by Allenby and Ropkins (2004). A reasonable amount of fill over the box is needed to do this under live traffic. The box structure is cast adjacent to its final position and then jacked into position with anti-drag ropes preventing the foundations below and the fill above moving with it. If there is not much fill depth, it becomes impractical to push the box whilst keeping a road or rail route over the top still. A similar approach can, how-ever, be used with the box cast in advance and then jacked into place in open cut over a relatively short possession.Multiple spansIn the past, some in situ multi-span slab bridges were built which were simply supported. However, unlike in bridges built from precast beams, it is no more complicated to build a continuous bridge. Indeed, because of the absence of the troublesome and leak-prone expansion joints, it may actually be simpler. It is therefore only in exceptional circumstances (for example construction in areas subject to extreme differential settlement due to mining subsidence) thatmultiple simply supported spans are now used.Making the deck continuous or building it into the abut-ments also leads to a significant reduction in the mid-span sagging moments in the slab.The advantage of this continuity in material terms is much greater than in bridges of pre-stressed beam construction where creep redistribution effects usually more than cancel out the saving in live load moments.Various approaches are possible for the piers. Either leaf piers can be used or discrete columns. Unlike in beam bridges, the latter approach needs no separate transverse beam. The necessary increase in local transverse moment capacity can be achieved by simply providing additional transverse reinforcement in critical areas. This facility makes slab bridges particularly suitable for geometrically complicated viaducts such as arise in some interchanges in urban situations. Curved decks with varying skew angles and discrete piers in apparently random locations can readily be accommodated.Whether discrete columns or leaf piers are used, they can either be provided with bearings or built into the deck. The major limitation on the latter approach is that, if the bridge is fixed in more than one position, the pier is subject to significant moments due to the thermal expansion and contraction of the deck. Unless the piers are very tall and slender, this usually precludes using the approach for more than one or two piers in a viaduct.Voided slab bridgesAbove a span of about 10–12m, the dead weight of a solid slab bridge starts to become excessive. For narrower bridges, significant weight saving can be achieved by using relatively long transverse cantilevers giving a bridge of ‘spine beam’form as shown in Figure 1. This canextend the economic span range of this type of structure to around 16m or more. Above this span, and earlier for wider bridges, a lighter form of construction is desirable.One of the commonest ways of lightening a solid slab is to use void formers of some sort. The commonest form is circular polystyrene void formers. Although polystyrene appears to be impermeable, it is only the much more expensive closed cell form which is so. The voids should therefore be provided with drainage holes at their lower ends. It is also important to ensure that the voids and reinforcement are held firmly in position in the formwork during construction. This avoids problems that have occurred with the voids floating or with the links moving to touch the void formers, giving no cover.Provided the void diameters are not more than around 60% of the slab thickness and nominal transverse steel is provided in the flanges, the bridge can be analysed much as a solidslab. That is, without considering either the reduced transverse shear stiffness or the local bending in the flanges. Unlike the previous British code, EN 1992-2 (BSI, 2005) does not give specific guidance on voided slabs. However, some is provided in the accompanying ‘PD’pub- lished by the British Standards Institution (BSI, 2008a).The section is designed longitudinally in both flexure and shear allowing for the voids. Links should be provided and these are designed as for a flanged beam with the minimum web thickness.The shear stresses are likely to become excessive near supports, particularly if discrete piers are used. However, this problem can be avoided by simply stopping the voids off, leaving a solid section in these critical areas.If more lightening is required, larger diameter voids or square voids forming a cellular deck can be used. These do then have to be considered in analysis. The longitudinal stiff-ness to be used for a cellular deck is calculated in the normal way, treating the section as a monolithic beam.Transversely, such a structure behaves quite differently under uniform and non-uniform bending. In the former, the top and bottom flanges act compositely whereas in the latter they flex about their separate neutral axes as shown in Figure 2. This means the correct flexural inertia can be an order of magnitude greater for uniform than non-uniform bending. The behaviour can, however, be modelled in a conventional grillage model by using a shear deformable grillage. The composite flexural properties are used and the extra defor-mation under non-uniform bending is represented by calcu-lating an equivalent shear stiffness.Having obtained the moments and forces in the cellular structure, the reinforcement has to be designed. In addition to designing for the longitudinal and transverse moments on the complete section, local moments in the flanges have to be considered. These arise from the wheel loads applied to the deck slab and also from the transverse shear. This shear has to be transmitted across the voidsby flexure in the flanges, that is by the section acting like a vierendeel frame as shown in Figure 2.Voided slab bridges typically have the rather utilitarian appearance typical of bridges with the type of voided section shown in Figure 1 and with either single spans or with intermediate piers of either leaf or discrete vertical pier form. However, one of the potential great advantages of concrete is that any shape can be formed. Figure 3 shows a voided slab bridge of more imaginative appearance which carries main line rail loading. To make most efficient use of the curved soffit varying depth section, different sizes of void were used across the width.Beam and slab bridgesIn recent years, in situ beam and slab structures have been less popular than voided slab forms, while precast beams have generally been prestressed. Reinforced beam andslab structures have therefore been less common. However, there is no fundamental reason why they should not be used and there are thousands of such structures in service.One of the disadvantages of a beam and slab structure compared with a voided slab or cellular slab structure is that the distribution properties are relatively poor. In the UK at least, this is less of a disadvantage than it used to be. This is because the normal traffic load has increased with each change of the loading specification, leaving the abnormal load the same until the most recent change which could actually make it less severe for shorter spans. However, reinforced concrete beam and slab bridges do not appear to have increased in popularity as a result. They are more popular in some other countries.The relatively poor distribution properties of beam and slab bridges can be improved by providing one or more transverse beams or diaphragms within the span, rather than only at the piers. In bridges built with precast beams, forming these ‘intermediate diaphragms’is extremely inconvenient and therefore expensive so they have become unusual. However, in an in situ structure which has to be built on falsework, it makes relatively little difference and is therefore more viable.The beams for a beam and slab structure are designed for the moments and forces from the analysis. The analysis is now usually computerised in European practice, although the AASHTO (2002) code encourages the use of a basically empirical approach.Having obtained the forces, the design approach is the same as for slabs apart from the requirement for nominal links in all beams. Another factor is that if torsion is consid-ered in the analysis the links have to be designed for torsion as well as for shear. Itis, however,acceptable practiceto use torsionless analysis at least for right decks.Because the deck slab forms a large top flange, the beams of beam and slab bridges are more efficiently shaped for resisting sagging than hogging moments. It may therefore be advantageous to haunch them locally over the piers even in relatively short-span continuous bridges.The biggest variation in practice in the design of beam and slab structures is in the reinforcement of the deck slab. A similar situation arises in the deck slabs of bridgeswhere the main beams are steel or prestressed concrete and this aspect will now be considered.Conventional practice in North America was to design only for the moments induced in the deck slab by its action in spanning between the beams supporting wheel loads (the ‘local moments’). These moments were obtained from Westergaard (1930) albeit usually by way of tables given in AASHTO. British practice also uses elastic methods to obtain local moments, usuallyeither Westergaard or influ-ence charts such as Pucher (1964). However, the so-called‘global transverse moments’, the moments induced in the deck slab by its action in distributing load between the beams, are considered. These moments, obtained from the global analysis of the bridge, are added to the local moments obtained from Westergaard (1930) or similar methods. Only‘co-existent’moments (the moments induced in the same part of the deck under the same load case) are considered, and the worst global and local moments often do notcoin-cide. However, this still has a significant effect. In bridges with very close spaced beams (admittedly rarely used in North America) the UK approach can give twice the design moments of the US approach.Although the US approach may appear theoretically unsound (the global moments obviously do exist in American bridges), it has produced satisfactory designs.One reason for this is that the local strength of the deck slabs is actually much greater than conventional elastic analysis suggests. This has been extensively researched (Hewit and Batchelor, 1975; Holowka and Csagoly, 1980;Kirkpatrick et al., 1984).In Ontario (Ontario Ministry of Transportation and Communications, 1983) empirical rules have been devel-oped which enable such slabs to be designed very simply and economically. Although these were developed without major consideration of global effects, they have been shown to work well within the range of cases they apply to (Jack-son and Cope, 1990). Similar rules have been developed in Northern Ireland (Kirkpatrick et al., 1984) and elsewhere but they have not been widely accepted in Europe.Longer span structuresIn modern practice, purely reinforced structures longer than about 20m span are quite unusual; concrete bridges of this size are usually prestressed. However, there is no funda-mental reason why such structures should not be built.The longest span reinforced concrete girder bridges tend to be of box girder form. Although single cell box girders are a well-defined form of construction, there is no clear-cut distinction between a ‘multi-cellular box girder’and a voided slab. However, the voids in voided slab bridges are normally formed with polystyrene or other permanent void formers, whereas box girders are usually formed with removable formwork. The formwork can only be removed if the section is deep enough for access, which effectively means around 1.2m minimum depth. Permanent access to the voids is often provided. In older structures, this was often through manholes in the top slab. This means traffic management is required to gain access and also means there is the problem of water, and de-icing salt where this is used, leaking into the voids. It is therefore preferable to provide access from below.In a continuous girder bridge (particularly one with only two spans) the hogging moments, particularly the perma-nent load moments, over the piers are substantially greater than the sagging moments at mid-span. This, combinedwith the greater advantage of saving weight near mid-span, encourages longer span bridges to be haunched. Haunching frequently also helps with the clearance required for road, rail or river traffic under the bridge by allowing a shallower section elsewhere.The longest span and most dramatic purely reinforced concrete bridges are open spandrel arches as in the Catha-leen’s Falls Bridge shown in Figure 4. The true arch form suits reinforced concrete well as the compressive force in the arch rib increases its flexural strength. As a result, the form is quite efficient in terms of materials.Because of the physical shape of the arch and the require- ment for good ground conditions to resist the lateral thrust force from the arch, this form of construction is limited in its application. It is most suitable for crossing valleys in hilly country. The simplest way to build such a structure is on falsework. However, the falsework required is very extensive and hence relatively expensive. Because of this, such bridges are often more expensive than structurally less efficient forms, such as prestressed cantilever bridges, that can be built with less temporary works. However, they may still be economic in some circumstances, particularly in countries where the labour required to erect the falsework is relatively cheap. A further factor may be local availability of the materials in countries where the prestressing equip-ment or structural steelwork required for other bridges of this span range would have to be imported.It is also possible to devise other ways of building arches.They have been built out in segments from either end supported by tying them back with temporary stays. Another approach, which is only likely to be viable with at least three spans, is to insert temporary diagonal mem- bers so that the bridge, including the columns supporting the deck and at least main longitudinal members at deck level, can be built bay by bay behaving as a truss until it is joined up.The efficiency of arch structures, like other forms used for longer span bridges, arises because the shape is optimised for resisting the near-uniform forces arising from dead load which is the dominant load. The profile of the arch is arranged to minimise the bending moments in it. Theoretically, the optimum shape approximates to a catenary if the weight of the rib dominates or a parabola if the weight of the deck dominates but the exact shape is unlikely to be critical.Arch structures can be so efficient at carrying dead weight that applying the usual load factor for dead load actually increases live load capacity by increasing the axial force in, andhence flexural capacity of, the rib. The design code’s lesser load factor (normally 1.0) for‘relieving effects’should be applied to dead weight when this arises. However, the letter of many codes only requires this to be applied in certain cases which are defined in such a way that it does not appear to apply here. This cannot be justified philosophi-cally and the reduced factor should be used.Because the geometry is optimised for a uniform load,loading the entire span is unlikely to be the critical live load case, unlike in a simple single-span beam bridge. It will normally be necessary to plot influence lines to determine the critical case. For uniform loads, this is often loading a half-span.Arch bridges have been built in which the live load bending moments are taken primarily by the girders at deck level, enabling the arch ribs to be very slim in appear-ance. However, the more usual approach is to build the arch rib first and then build the deck structure afterwards, possibly even after the falsework has been struck so that this does not have to be designed to take the full load.The deck structure is then much like a normal viaduct supported on piers from the arch rib and the rib has to take significant moments.In the past, reinforced concrete truss structures have also been built but they are not often used in modern practice because the building costs are high due to the complexity of formwork and reinforcement.Design calculationGeometryThe shape of reinforced concrete bridges is usually decided by experience aided by typical span-to-depth ratios. The design calculations are only really used to design the reinforcement. A typical simply supported slab has a span-to-depth ratio of around 10–15 but continuous or integral bridges can be shallower. Because the concentrated live load (i.e. the wheel load) the deck has to carry does not reduce with span, the span-to-depth ratio of short span slabs tends to be towards the lower end of the range.However, deck slabs of bigger bridges often have greater span-to-depth ratios than slab bridges. This is economic because the dead weight of the slab, although an insignifi-cant part of the load on the slab, is significant to the global design of the bridge.There was a fashion for very shallow bridges in the 1960s and 1970s as they were considered to look more elegant. However, unless increasing the construction depth has major cost implications elsewhere (such as the need to raise embankments) it is likely to be more economic to use more than the minimum depth. The appearance dis-advantage on short span bridges can be resolved by good detailing of the edges. Bridge decks with short transverse cantilevers at the edges tend to look shallower than vertical sided bridges even if they are actually deeper.Having decided the dimensions of the bridge, the design calculations then serve primarily to design the reinforce-ment and the key checks will now be considered. They will be illustrated mainly by considering slab structures but most of the principles apply to all reinforced concrete. Ultimate strength in flexure and torsionReinforced concrete is normally designed for ultimate strength in flexure first. This is partly because this is usually, although not invariably, the critical design criterion.Another reason is that reinforcement can be more readily designed directly for this criterion. For other criteria, suchas crack width or service stresses, a design has to be assumed and then checked. This makes thedesign process iterative. A first estimate is required to start the iterative procedure and the ultimate strength design provides such an estimate.Although other analytical methods give better estimates of strength, elastic analysis is usually used in design. This has to be used when checking serviceability criteria. Because of this, the use of more economic analyses at the ultimate limit state (such as yield-line analysis) invariably results in other criteria (such as cracking or stress limits) becoming critical leaving little or no advantage.Concrete slabs have to resist torsion as well as flexure. However, unlike in a beam, torsion and flexure in slabs are not separate phenomena. They interact in the same way that direct and shear stresses interact in plane stress situations. They can be considered in the same way: thatis using Mohr’s circle. Theoretically, it is most efficient to use orthogonal reinforcement placed in the directions of maximum and minimum principal moments. Since there is no torsion in these directions, torsion does not then have to be considered. However, it is not often practical to do this as the principal moment directions change with both position in the slab and load case.In right slabs the torsional moments in the regions (the elements of the computer model where this is used),where the moments are maximum, are relatively small and can often be ignored. In skew slabs, in contrast, the torsions can be significant. The usual approach is to design for an increased equivalent bending moment in the reinforcement directions. Wood (1968) has published the relevant equations for orthogonal steel and Armer (1968) for skew steel. Many of the computer programs commonly used for the analysis of bridge decks have post-processors that enable them to give these corrected moments, com-monly known as ‘Wood–Armer’moments, directly. To enable them to do this, it is necessary to specify the direc-tion of the reinforcement.When the reinforcement is very highly skewed, the Wood–Armer approach leads to excessive requirements for transverse steel. When assessing existing structures, this problem can be avoided by using alternative analytical approaches. However, in design it is usually preferable to avoid the problem by avoiding the use of very highly skewed reinforcement. The disadvantage of this is that it makes the reinforcement detailing of skew slab bridges more complicated. This arises because the main steel in the edges of the slab has to run parallel with the edges. Orthogonal steel can therefore only be achieved in the centre of the bridge either by fanning out the steel or bypro-viding three layers in the edge regions. That is, one parallel to the edge in addition to the two orthogonal layers.When torsion is considered, it will be found that there is a significant requirement for top steel in the obtuse corners even of simply supported slabs. It can be shown using other analytical methods (such as yield-line or torsionless grillage analysis) that equilibrium can be satisfied without resisting these moments. The top steel is therefore not strictly necessary for ultimate strength. However, the moments are real and have caused significant cracking in older slab structures which were built without this steel. It is therefore preferable to reinforce for them. Ultimate strength in shearShear does not normally dictate the dimensions of the element. However, codes allow slabs (unlike beams) which do not have shear reinforcement and it is economically desirable to avoid shear reinforcement in these if e of links is particularly inconvenient in very shallow slabs, such as in box culverts or the deck slabs of beam and slab bridges, and many codes do not allow them to be considered effective. The shear strength rules can therefore be critical in design.。

中文4840字附录 2 外文资料翻译原文11.7.4 Deflection11.7.4.1 Dead Load and Creep DeflectionGlobal vertical deflections of segmental box-girder bridges due to the effects of dead load and post-tensioning as well as the long-term effect of creep are normally predicted during the design process by the use of a computer analysis program. The deflections are dependent, to a large extent, on the method of construction of the structure, the age of the segments when post-tensioned, and the age of the structure when other loads are applied. It can be expected, therefore, that the actual deflections of the structure would be different from that predicted during design due to changed assumptions.The deflections are usually recalculated by the contractor’s engineer, based on the actual construction sequence.11.7.4.2 Camber RequirementsThe permanent deflection of the structure after all creep deflections have occurred, normally 10 to 15 years after construction, may be objectionable from the perspective of riding comf ort for the users or for the confidence of the general public. Even if there is no structural problem with a span with noticeable sag, it will not inspire public confidence. For these reasons, a camber will normally be cast into the structure so that the p ermanent deflection of the bridge is nearly zero. It may be preferable to ignore the camber, if it is otherwise necessary to cast a sag in the structure during onstruction.11.7.4.3 Global Deflection Due to Live LoadMost design codes have a lim it on the allowable global deflection of a bridge span due to the effects of live load. The purpose of this limit is to avoid the noticeable vibration for the user and minimize the effects of moving load iMPact. When structures are used by pedestrians as well as motorists,the limits are further tightened.11.7.4.4 Local Deflection Due to Live LoadSimilar to the limits of global deflection of bridge spans, there are also limitations on the deflection of the local elements of the box-girder cross section. For example, the AASHTO Specifications limit the deflection of cantilever arms due to service live load plus iMPact to ¹⁄₃of the cantilever length,except where there is pedestrian use [1].11.7.5 Post-Tensioning Layout11.7.5.1 Exter nal Post-TensioningWhile most concrete bridges cast on falsework or precast beam bridges have utilized post-tensioning in ducts which are fully encased in the concrete section, other innovations have been made in precast segmental construction.Especially prevalent in structures constructed using the span-by-span method, post-tensioning has been placed inside the hollow cell of the box girder but not encased in concrete along its length. This is know as external post-tensioning. External post-tensioning is easily inspected at any time during the life of the structure, eliminates the problems associated with internal tendons, and eliminates the need for using expensive epoxy adhesive between precastsegments. The problems associated with internal tendons are (1) misalignment of the tendons at segment joints, which causes spalling; (2) lack of sheathing at segment joints; and (3) tendon pull-through on spans with tight curvature (see Figure 11.39). External prestressing has been used on many projects in Europe, the United States, and Asia and has performed well.11.7.5The provision for the addition of post-tensioning in the future in order to correct unacceptable creep deflections or to strengthen the structure for additional dead load, i.e., future wearing surface, is now required by many codes. Of the positive and negative moment post-tensioning, 10% is reasonable. Provisions should be made for access, anchorage attachment, and deviation of these additional tendons. External, unbonded tendons are used so that ungrouted ducts in the concrete are not left open. 11.8 Seismic Considerations11.8.1 Design Aspects and Design CodesDue to typical vibration characteristics of bridges, it is generally accepted that under seismic loads,some portion of the structure will be allowed to yield, to dissipate energy, and to increase the period of vibration of the system. This yielding is usually achieved by either allowing the columns to yield plastically (monolithic deck/superstructure connection), or by providing a yielding or a soft bearing system [6].The same principles also apply to segmental structures, i.e., the segmental superstructureneeds to resist the demands imposed by the substructure. Very few implementations of segmental struc-tures are found in seismically active California, where most of the research on earthquake-resistant bridges is conducted in the United States. The Pine Valley Creek Bridge, Parrots Ferry Bridge, and Norwalk/El Segundo Line Overcrossing, all of them being in California, are examples of segmental structures; however, these bridges are all segmentally cast in place, with mild reinforcement crossing the segment joints.Some guidance for the seismic design of segmental structures is provided in the latest edition of the AASHTO Guide Specifications for Design and Construction of Segmental Concrete Bridges [2], which now contains a chapter dedicated to seismic design. The guide allows precast-segmental construction without reinforcement across the joint, but specifies the following additional require-ments for these structures:•For Seismic Zones C and D [1], either cast-in-place or epoxied joints are required.•At least 50% of the prestress force should be provided by internal tendons.•The internal tendons alone should be able to carry 130% of the dead load.For other seismic design and detailing issues, the reader is referred to the design literature providedby the California Department of Transportation, Caltrans, for cast-in-place structures [5-8].11.8.2 Deck/Superstructure ConnectionRegardless of the design approach adopted (ductility through plastic hinging of the column or through bearings), the deck/superstructure connection is a critical element in the seismic resistant system. A brief description of the different possibilities follows.11.8.2.1 Monolithic Deck/Superstructure ConnectionFor the longitudinal direction, plastic hinging will form at the top and bottom of the columns. Since most of the testing has been conducted on cast-in-place joints, this continues to be the preferred option for these cases. For short columns and for solid columns, the detailing in this area can be readily adapted from standard Caltrans practice for cast-in-place structures, as shown on Figure 11.40. The joint area is then essentially detailed so it is no different from that of a fully cast-in-place bridge. In particular, a Caltrans requirement for positive moment reinforcement over the pier can be detailed with prestressing strand, as shown below. For large spans and tall columns, hollow column sections would be more appropriate. In these cases, care should be taken to confine the main column bars with closely spaced ties, and joint shear reinforcement should be provided according to Reference [3 or 7]. The use of fully precast pier segments in segmental superstructures would probably require special approval of the regulating government agency, since such a solution has not yet been tested for bridges and is not codified. Nevertheless, based upon first principles, and with the help of strut–tiemodels, it is possible to design systems that would work in practice [6]. The segmental superstructure should be designed to resist at least 130%of the column nominal moment using the strength reduction factors prescribed in Ref. [2]. Of further interest may be a combination of precast and cast-in-place joint as shown in Figure 11.41, which was adapted from Ref.[8]. Here, the precast segment serves as a form for the cast-in-place portion that fills up the remainder of the solid pier cap. Other ideas can also be derived from the building industry where some model testing has been performed. Of particular interest for bridges could be a system that works by leaving dowels in the columns and supplying the precast segment with matching formed holes, which are grouted after the segment is slipped over the reinforcement [9]11.8.2.2Deck/Superstructure Connection via BearingsTypically, for spans up to 45 m erected with the span-by-span method, the superstructure will be supported on bearings. For action in the longitudinal direction, elastomeric or isolation bearings are preferred to a fixed-end/expansion-end arrangement, since these better distribute the load between the bearings. Furthermore, these bearings will increase the period of the structure, which results in an overall lower induced force level (beneficial for higher-frequency structures), and isolation bearings will provide some structural damping as well.In the transverse direction, the bearings may be able to transfer load between super- and sub-structure by shear deformation; however, for the cases where this is not possible, shear keys can be provided as is shown in Figure 11.42. It should be noted that in regions of high seismicity,for structures with tall piers or soft substructures, the bearing demands may become excessive and a monolithic deck–superstructure connection may become necessary.For the structure-on-bearings approach, the force level for the superstructure can be readily，determined, since once the bearing demands are obtained from the analysis, they can be applied to the superstructure and substructure. The superstructure should resist the resulting forces at ultimate (using the applicable code force-reduction factors), whereas the substructure can be allowed to yield plastically if necessary.11.8.2.3 Expansion HingesFrom the seismic point of view, it is desirable to reduce the number of expansion hinges (EH)to a minimum. If EHs are needed, the most beneficial location from the seismic point of view is at midspan. This can be explained by observing Figure 11.43, where the superstructure bending midspan and for an EH at quarterspan. For the latter, it can be seen that the moment at the face The location of expansion hinges within a span, and its characteristics, depends also on the stiffness of the substructure and the type of connection of the superstructure to the piers. presents general guidelines intended to assist in the selection of location of expansion hinges.11.8.2.4 Precast Segmental PiersPrecast segmental piers are usually hollow cross section to save weight. From research inother areas it can be extrapolated that the precast segments of the pier would be joined by means of unbonded prestressing tendons anchored in the footing. The advantage of unbonded over bonded tendons is that for the former, the prestress force would not increase signi ficantly under high column displace-ment demands, and would therefore not cause inelastic yielding of the strand, which would other-wise lead to a loss of prestress.The detail of the connection to the superstructure and foundation would require some insight into the dynamic characteristics of such a connection, which entails joint opening and closing providing that dry joints are used between segments. This effect is similar to footing rocking, which is well known to be bene ficial to the response of a structure in an earthquake. This is due to the period shift and the damping of the soil. The latter effect is clearly not available to the precast columns, but the period shift is. Details need to be developed for the bearing areas at the end of the columns, as well as the provision for clearance of the tendons to move relative to the pier during the event.If the upper column segment is designed to be connected monolithically to the superstructure, yielding of the reinforcement should be expected. In this case, the expected plastic hinge length should be detailed ductile, using closely spaced ties [3,5].11.9 Casting and Erection11.9.1 CastingThere are obvious major differences in casting and erection when working with cast-in-placecantilever in travelers or in handling precast segments. There are also common features, which must be kept in mind in the design stages to keep the projects simple and thereby economic and ef ficient,such as• Keeping the length of segments equal and segments straight, even in curved bridges; • Maintaining constant cross section dimensions as much as possible;• Minimizing the number of diaphragms and stiffeners, and avoiding dowels through form- work.11.9.1.1 Cast-in-Place CantileversThe conventional form traveler supports the weight of the fresh concrete of the new segment by means of longitudinal beams or frames extending out in cantilever from the last segment. These beams are tied down to the previous segment. A counterweight is used when launching the traveler forward. The main beams are subjected to some de flections, which may produce cracks in the joint between the old and new segments. Jacking of the form during casting is sometimes needed to avoid these cracks. The weight of a traveler is about 60% of the weight of the segment.The rate of construction is typically one segment per traveler per week. Precast concrete anchor blocks are used to speed up post-tensioning operations. In cold climates, Conventional Travelers Construction Camber Controlcuring can be accelerated by various heating processes.The most critical practical problem of cast-in-place construction is deflection control. There are five categories of deflections during and after construction:•Deflection of traveler frame under the weight of the concrete segment;•Deflection of the concrete cantilever arm during construction under the weight of segment plus post-tensioning;•Deflection of cantilever arms after construction and before continuity;•Short- and long-term deflections of the continuous structure;•Short- and long-term pier shortenings and foundation settlements.The sum of the various deflection values for the successive sections of the deck allows the construc-tion of a camber diagram to be added to the theoretical profile of the bridge. A construction camber for setting the elevation of the traveler at each joint must also be developed.11.9.1.2 Precast SegmentsOpposite to the precast girder concept where the bridge is cut longitudinally in the precast segmental methods, the bridge is cut transversally, each slice being a segment. Segments are cast in a casting yard one at a time. Furthermore, the new segment is cast against the previously cast segment so that the faces in contact match perfectly. This is the match-cast principle. When the segments are reassembled at the bridge site, they will take the same relative position with regard to the adjacent segments that they had when they were cast. Accuracy of segment geometry is an absolute priority, and adequate surveying methods must be used to ensure follow-up of the geometry.Match casting of the segments is a prerequisite for the application of glued joints, achieved by covering the end face of one or both of the meeting segments with epoxy at the erection. The epoxy serves as a lubricant during the assembly of the segments, and it ensures a watertight joint in thefinished structure. Full watertightness is needed for corrosion protection of internal tendons (ten-dons inside the concrete). The tensile strength of the epoxy material is higher than that of the concrete, but, even so, the strength of the epoxy is not considered in the structural behavior of the joint. The required shear capacity is generally provided by shear keys, single or multiple, in com-bination with longitudinal post-tensioning.With the introduction of external post-tensioning, where the tendons are installed in PE ducts,outside the concrete but inside the box girder, the joints are relieved of the traditional requirement of watertightness and are left dry. The introduction of external tendons in connection with dry joints greatly enhanced the efficiency of precasting.11.9.1.3 Casting MethodsThere are two methods for casting segments. The first one is the long-line method, where all the segments are cast in their correct position on a casting bed that reproduces the span. The second method, used most of the time, is the short-line method, where all segments are cast in the same place in a stationary form, and against the previously cast segment. After casting and initial curing, the previously cast segment isremoved for storage, and the freshly cast segment is moved into place.11.9.1.4 Geometry ControlA pure translation of each segment between cast and match-cast position results in a straight bridge(Figure 11.45). To obtain a bridge with a vertical curve, the match-cast segment must first be translated and given a rotation in the vertical plane (Figure 11.46). Practically, the bulkhead is left fixed and the mold bottom under the conjugate unit adjusted. To obtain a horizontal curvature, the conjugate unit is given a rotation in the horizontal plane (see Figure 11.47). To obtain a variable superelevation, the conjugate unit is rotated around a horizontal axis located in the middle of the top slab (Figure 11.48).All these adjustments of the conjugate unit can be combined to obtain the desired geometry of the bridge.11.9.2 ErectionThe type of erection equipment depends upon the erection scheme contemplated during the design process; the local conditions, either over water or land; the speed of erection and overall construction schedule. It falls into three categories, independent lifting equipment such as cranes,deck-mounted lifting equipment such as beam and winch or swivel crane, and launching girder equipment.The principle of the method is to erect or cast the pier segment first, then to place typical segments one by one from each side of the pier, or in pairs simultaneously from both sides. Each newly placed precast segment is fixed to the previous one with temporary PT bars, until the cantilever tendons are installed and stressed. The closure joint between cantilever tips is poured in place and continuity tendons installed and stressed.In order to carry out this erection scheme, segments must be lifted and installed at the proper location. The simplest way is to use a crane, either on land or barge mounted. Many bridges have Bridge with superelevation.been erected with cranes as they do not require an investment in special lifting equipment. This method is slow. Typically, two to four segments per day are placed. It is used on relatively short bridges. An alternative is to have a winch on the last segment erected. The winch is mounted on a beam fixed to the segment. It picks up segments from below, directly from truck or barge. After placing the segment, the beam and winch system is moved forward to pick up the next segment and so on. Usually, a beam-and-winch system is placed on each cantilever tip. This method is also slow; however, it does not require a heavy crane on the site, which is always very expensive, especially if the segments are heavy.When bridges are long and the erection schedule short, the best method is the use of launching girders, which then take full advantage of the precast segmental concept for speed of erection.There are two essential types of self-launching gantries developed for this erection method. The first type is a gantry with a length slightly longer than the typical span (see Figure 11.49). During erection of the cantilever, the center leg rests on the pier while the rear leg rests on the cantilever tip of the previously erected span, which must resist the corresponding reaction. Prior to launching,the back spans must be made continuous. Then, the center leg is moved to the forward cantilever tip, which must resist the weight of the gantry plus the weight of the pier segment.This stage controls the design of the gantry, which must be made as light as possible, and of the cantilever.The second type of gantry has a length that is twice that of the typical span (see Figure 11.50).The reaction from the legs during the erection and launching of the next span is always applied on the piers, so there is no concentrated erection load on the cantilever tip. Each erection cycle consists of the erection of all typical segments of the cantilever and then the placement of the pier segment for the next cantilever, without changing the position of the truss.The gantries can be categorized by their cross section: single truss, with portal-type legs, and two launching trusses with a gantry across. The twin box girders of the bridge in Hawaii were built with two parallel, but independent trusses (see Figure 11.51), with a typical span of 100.0 m, segmentweights of 70 tons; the two bridge structures are 27.5 m apart with different elevations and longi-tudinal slopes. This system is a refinement of the first type of gantry applied to twin decks with variable geometry.Normally, the balanced cantilever method is used for spans from 60 to 110 m, with a launching girder. One full, typical cycle of erection is placing segments, installing and stressing post-tensioning tendons, and launching the truss to its next position. It takes about 7 to 10 days, but may vary greatly according to the specifics of a project and the sophistication of the launching girder. With proper equipment and planning, erection of 16 segments per day has been achieved.译文11.7.4 挠度11.7.4.1 恒载和徐变部分箱梁的整体变形是由恒载和后加张力造成的，也包括在设计过程中用电脑分析软件正常算出的徐变的长期影响。

桥梁工程中英文对照外文翻译文献(文档含英文原文和中文翻译)BRIDGE ENGINEERING AND AESTHETICSEvolvement of bridge Engineering,brief reviewAmong the early documented reviews of construction materials and structu re types are the books of Marcus Vitruvios Pollio in the first century B.C.The basic principles of statics were developed by the Greeks , and were exemplifi ed in works and applications by Leonardo da Vinci,Cardeno,and Galileo.In the fifteenth and sixteenth century, engineers seemed to be unaware of this record , and relied solely on experience and tradition for building bridges and aqueduc ts .The state of the art changed rapidly toward the end of the seventeenth cent ury when Leibnitz, Newton, and Bernoulli introduced mathematical formulatio ns. Published works by Lahire (1695)and Belidor (1792) about the theoretical a nalysis of structures provided the basis in the field of mechanics of materials .Kuzmanovic(1977) focuses on stone and wood as the first bridge-building materials. Iron was introduced during the transitional period from wood to steel .According to recent records , concrete was used in France as early as 1840 for a bridge 39 feet (12 m) long to span the Garoyne Canal at Grisoles, but r einforced concrete was not introduced in bridge construction until the beginnin g of this century . Prestressed concrete was first used in 1927.Stone bridges of the arch type (integrated superstructure and substructure) were constructed in Rome and other European cities in the middle ages . Thes e arches were half-circular , with flat arches beginning to dominate bridge wor k during the Renaissance period. This concept was markedly improved at the e nd of the eighteenth century and found structurally adequate to accommodate f uture railroad loads . In terms of analysis and use of materials , stone bridges have not changed much ,but the theoretical treatment was improved by introd ucing the pressure-line concept in the early 1670s(Lahire, 1695) . The arch the ory was documented in model tests where typical failure modes were considered (Frezier,1739).Culmann(1851) introduced the elastic center method for fixed-e nd arches, and showed that three redundant parameters can be found by the us e of three equations of coMPatibility.Wooden trusses were used in bridges during the sixteenth century when P alladio built triangular frames for bridge spans 10 feet long . This effort also f ocused on the three basic principles og bridge design : convenience(serviceabili ty) ,appearance , and endurance(strength) . several timber truss bridges were co nstructed in western Europe beginning in the 1750s with spans up to 200 feet (61m) supported on stone substructures .Significant progress was possible in t he United States and Russia during the nineteenth century ,prompted by the ne ed to cross major rivers and by an abundance of suitable timber . Favorable e conomic considerations included initial low cost and fast construction .The transition from wooden bridges to steel types probably did not begin until about 1840 ,although the first documented use of iron in bridges was the chain bridge built in 1734 across the Oder River in Prussia . The first truss completely made of iron was in 1840 in the United States , followed by Eng land in 1845 , Germany in 1853 , and Russia in 1857 . In 1840 , the first ir on arch truss bridge was built across the Erie Canal at Utica .The Impetus of AnalysisThe theory of structures ,developed mainly in the ninetheenth century,foc used on truss analysis, with the first book on bridges written in 1811. The Wa rren triangular truss was introduced in 1846 , supplemented by a method for c alculating the correcet forces .I-beams fabricated from plates became popular in England and were used in short-span bridges.In 1866, Culmann explained the principles of cantilever truss bridges, an d one year later the first cantilever bridge was built across the Main River in Hassfurt, Germany, with a center span of 425 feet (130m) . The first cantileve r bridge in the United States was built in 1875 across the Kentucky River.A most impressive railway cantilever bridge in the nineteenth century was the Fir st of Forth bridge , built between 1883 and 1893 , with span magnitudes of 1711 feet (521.5m).At about the same time , structural steel was introduced as a prime mater ial in bridge work , although its quality was often poor . Several early exampl es are the Eads bridge in St.Louis ; the Brooklyn bridge in New York ; and t he Glasgow bridge in Missouri , all completed between 1874 and 1883.Among the analytical and design progress to be mentioned are the contrib utions of Maxwell , particularly for certain statically indeterminate trusses ; the books by Cremona (1872) on graphical statics; the force method redefined by Mohr; and the works by Clapeyron who introduced the three-moment equation s.The Impetus of New MaterialsSince the beginning of the twentieth century , concrete has taken its place as one of the most useful and important structural materials . Because of the coMParative ease with which it can be molded into any desired shape , its st ructural uses are almost unlimited . Wherever Portland cement and suitable agg regates are available , it can replace other materials for certain types of structu res, such as bridge substructure and foundation elements .In addition , the introduction of reinforced concrete in multispan frames at the beginning of this century imposed new analytical requirements . Structures of a high order of redundancy could not be analyzed with the classical metho ds of the nineteenth century .The importance of joint rotation was already dem onstrated by Manderla (1880) and Bendixen (1914) , who developed relationshi ps between joint moments and angular rotations from which the unknown mom ents can be obtained ,the so called slope-deflection method .More simplification s in frame analysis were made possible by the work of Calisev (1923) , who used successive approximations to reduce the system of equations to one simpl e expression for each iteration step . This approach was further refined and int egrated by Cross (1930) in what is known as the method of moment distributi on .One of the most import important recent developments in the area of analytical procedures is the extension of design to cover the elastic-plastic range , also known as load factor or ultimate design. Plastic analysis was introduced with some practical observations by Tresca (1846) ; and was formulated by Sa int-Venant (1870) , The concept of plasticity attracted researchers and engineers after World War Ⅰ, mainly in Germany , with the center of activity shifting to England and the United States after World War Ⅱ.The probabilistic approa ch is a new design concept that is expected to replace the classical determinist ic methodology.A main step forward was the 1969 addition of the Federal Highway Adim inistration (F HWA)”Criteria for Reinforced Concrete Bridge Members “ that co vers strength and serviceability at ultimate design . This was prepared for use in conjunction with the 1969 American Association of State Highway Offficials (AASHO) Standard Specification, and was presented in a format that is readil y adaptable to the development of ultimate design specifications .According to this document , the proportioning of reinforced concrete members ( including c olumns ) may be limited by various stages of behavior : elastic , cracked , an d ultimate . Design axial loads , or design shears . Structural capacity is the r eaction phase , and all calculated modified strength values derived from theoret ical strengths are the capacity values , such as moment capacity ,axial load ca pacity ,or shear capacity .At serviceability states , investigations may also be n ecessary for deflections , maximum crack width , and fatigue .Bridge TypesA notable bridge type is the suspension bridge , with the first example bu ilt in the United States in 1796. Problems of dynamic stability were investigate d after the Tacoma bridge collapse , and this work led to significant theoretica l contributions Steinman ( 1929 ) summarizes about 250 suspension bridges bu ilt throughout the world between 1741 and 1928 .With the introduction of the interstate system and the need to provide stru ctures at grade separations , certain bridge types have taken a strong place in bridge practice. These include concrete superstructures (slab ,T-beams,concrete box girders ), steel beam and plate girders , steel box girders , composite const ruction , orthotropic plates , segmental construction , curved girders ,and cable-stayed bridges . Prefabricated members are given serious consideration , while interest in box sections remains strong .Bridge Appearance and AestheticsGrimm ( 1975 ) documents the first recorded legislative effort to control t he appearance of the built environment . This occurred in 1647 when the Cou ncil of New Amsterdam appointed three officials . In 1954 , the Supreme Cou rt of the United States held that it is within the power of the legislature to de termine that communities should be attractive as well as healthy , spacious as well as clean , and balanced as well as patrolled . The Environmental Policy Act of 1969 directs all agencies of the federal government to identify and dev elop methods and procedures to ensure that presently unquantified environmenta l amentities and values are given appropriate consideration in decision making along with economic and technical aspects .Although in many civil engineering works aesthetics has been practiced al most intuitively , particularly in the past , bridge engineers have not ignored o r neglected the aesthetic disciplines .Recent research on the subject appears to lead to a rationalized aesthetic design methodology (Grimm and Preiser , 1976 ) .Work has been done on the aesthetics of color ,light ,texture , shape , and proportions , as well as other perceptual modalities , and this direction is bot h theoretically and empirically oriented .Aesthetic control mechanisms are commonly integrated into the land-use re gulations and design standards . In addition to concern for aesthetics at the sta te level , federal concern focuses also on the effects of man-constructed enviro nment on human life , with guidelines and criteria directed toward improving quality and appearance in the design process . Good potential for the upgradin g of aesthetic quality in bridge superstructures and substructures can be seen in the evaluation structure types aimed at improving overall appearance .Lords and lording groupsThe loads to be considered in the design of substructures and bridge foun dations include loads and forces transmitted from the superstructure, and those acting directly on the substructure and foundation .AASHTO loads . Section 3 of AASHTO specifications summarizes the loa ds and forces to be considered in the design of bridges (superstructure and sub structure ) . Briefly , these are dead load ,live load , iMPact or dynamic effec t of live load , wind load , and other forces such as longitudinal forces , cent rifugal force ,thermal forces , earth pressure , buoyancy , shrinkage and long t erm creep , rib shortening , erection stresses , ice and current pressure , collisi on force , and earthquake stresses .Besides these conventional loads that are ge nerally quantified , AASHTO also recognizes indirect load effects such as fricti on at expansion bearings and stresses associated with differential settlement of bridge components .The LRFD specifications divide loads into two distinct cate gories : permanent and transient .Permanent loadsDead Load : this includes the weight DC of all bridge components , appu rtenances and utilities, wearing surface DW nd future overlays , and earth fill EV. Both AASHTO and LRFD specifications give tables summarizing the unit weights of materials commonly used in bridge work .Transient LoadsVehicular Live Load (LL) Vehicle loading for short-span bridges :considera ble effort has been made in the United States and Canada to develop a live lo ad model that can represent the highway loading more realistically than the H or the HS AASHTO models . The current AASHTO model is still the applica ble loading.桥梁工程和桥梁美学桥梁工程的发展概况早在公元前1世纪，Marcus Vitrucios Pollio 的著作中就有关于建筑材料和结构类型的记载和评述。

桥梁词条解释1．桥位地形图（qiao wei di xing tu ）topography map of bridge site应用地形测量的方法，测绘出桥位处地物、地貌的平面位置，并把地面的高低起伏用规定的符号绘制成正射投影图。

桥位地形图是经过实地测绘的，能客观的反映桥位处地面情况，所以成为桥梁规划设计的重要依据。

2．桥位地质剖面图（qiao wei di zhi pou mian tu）geologic section drawing of bridge site 通过假设的方法，把实际上看不见的桥位地质资料情况，按岩石的种类、地层、年代、地质构造单元等绘制于图上，形成桥位地质剖面图。

它是基础设计的重要依据。

3．水文资料（shui wen zi liao ）hydrologic data水文资料是河流水情变化（通常指流量、流速、水位、降雨、蒸发、泥砂、冰冻等）的记录。

它是进行水文分析与计算的基础，其来源一般有三个方面：水文站观测资料，洪水调查资料和文献资料。

一般以水文站观测资料作为主要依据，同时利用洪水调查和文献进行补充与完善。

4．气象资料（qi xiang zi liao）meteorologic data气象资料是某一地区在一定的时间内，大气圈状态的变化记录。

包括温度、湿度、云量、降水、蒸发、气压、风速等物理指标和因素。

气象资料是进行气候分析与温度计算的基础，是桥梁计算中不可缺少的部分。

5．水力计算（shui li ji suan）hydraulic computation根据液体平衡和运动的规律由已知条件计算水体的水力特性（如：水力最优断面、允许流速、粗糙系数等）称为水力计算。

水力计算是解决水力问题的基本方法之一。

6．设计流速（she ji liu su）design current velocity设计流速：Vs=Qs/(p*Wy)其中：Vs---- 设计流速（m/s）；Qs---- 设计流量(m^3/s)；P------冲刷系数；Wy----冲刷前桥下的有效过水面积(m^2)。

本科毕业设计论文专业外文翻译专业名称：土木工程专业道路与桥梁年级班级：道桥08-5班学生姓名：指导教师：二○一二年五月十八日Geometric Design of HighwaysThe road is one kind of linear construction used for travel. It is made of the roadbed, the road surface, the bridge, the culvert and the tunnel. In addition, it also has the crossing of lines, the protective project and the traffic engineering and the route facility.The roadbed is the base of road surface, road shoulder, side slope, side ditch foundations. It is stone material structure, which is designed according to route's plane position .The roadbed, as the base of travel, must guarantee that it has the enough intensity and the stability that can prevent the water and other natural disaster from corroding.The road surface is the surface of road. It is single or complex structure built with mixture. The road surface require being smooth, having enough intensity, good stability and anti-slippery function. The quality of road surface directly affects the safe, comfort and the traffic.Highway geometry designs to consider Highway Horizontal Alignment, Vertical Alignment two kinds of linear and cross-sectional composition of coordination, but also pay attention to the smooth flow of the line of sight, etc. Determine the road geometry, consider the topography, surface features, rational use of land and environmental protection factors, to make full use of the highway geometric components of reasonable size and the linear combination.DesignThe alignment of a road is shown on the plane view and is a series of straight lines called tangents connected by circular. In modern practice it is common to interpose transition or spiral curves between tangents and circular curves.Alignment must be consistent. Sudden changes from flat to sharp curves and long tangents followed by sharp curves must be avoided; otherwise, accident hazards will be created. Likewise, placing circular curves of different radii end to end compound curves or having a short tangent between two curves is poor practice unless suitable transitions between them are provided. Long, flat curves are preferable at all times, as they are pleasing in appearance and decrease possibility of future obsolescence. However, alignment without tangents is undesirable on two-lane roads because some drivers hesitate to pass on curves. Long, flat curves should be used for small changes in direction, as short curves appear as “kink”. Also horizontal and vertical alignment must be considered together, not separately. For example, a sharp horizontal curve beginning near a crest can create a serious accident hazard.A vehicle traveling in a curved path is subject to centrifugal force. This is balanced by an equal and opposite force developed through cannot exceed certain maximums, and these controls place limits on the sharpness of curves that can be used with a design speed. Usually the sharpness of a given circular curve is indicated by its radius. However, for alignment design, sharpness is commonly expressed in terms of degree of curve, which is the central angle subtended by a 100-ft length of curve. Degree of curve is inversely proportional to the radius.Tangent sections of highways carry normal cross slope; curved sections are super elevated. Provision must be made for gradual change from one to the other. This usually involves maintaining the center line of each individual roadway at profile grade while raising the outer edge and lowering the inner edge to produce the desired super elevation is attained some distance beyond the point of curve.If a vehicle travels at high speed on a carefully restricted path made up of tangents connected by sharp circular curve, riding is extremely uncomfortable. As the car approaches a curve, super elevation begins and the vehicle is tilted inward, but the passenger must remain vertical since there is on centrifugal force requiring compensation. When the vehicle reaches the curve, full centrifugal force develops at once, and pulls the rider outward from his vertical position. To achieve a position of equilibrium he must force his body far inward. As the remaining super elevation takes effect, further adjustment in position is required. This process is repeated in reverse order as the vehicle leaves the curve. When easement curves are introduced, the change in radius from infinity on the tangent to that of the circular curve is effected gradually so that centrifugal force also develops gradually. By careful application of super elevation along the spiral, a smooth and gradual application of centrifugal force can be had and the roughness avoided.Easement curves have been used by the railroads for many years, but their adoption by highway agencies has come only recently. This is understandable. Railroad trains must follow the precise alignment of the tracks, and the discomfort described here can be avoided only by adopting easement curves. On the other hand, the motor-vehicle operator is free to alter his lateral position on the road and can provide his own easement curves by steering into circular curves gradually. However, this weaving within a traffic lane but sometimes into other lanes is dangerous. Properly designed easement curves make weaving unnecessary. It is largely for safety reasons, then, that easement curves have been widely adopted by highway agencies.For the same radius circular curve, the addition of easement curves at the ends changes the location of the curve with relationto its tangents; hence the decision regarding their use should be made before the final location survey. They point of beginning of an ordinary circular curve is usually labeled the PC point of curve or BC beginning of curve. Its end is marked the PT point of tangent or EC end of curve. For curves that include easements, the common notation is, as stationing increases: TS tangent to spiral, SC spiral to circular curve, CS circular curve to spiral, and ST spiral go tangent.On two-lane pavements provision of a wilder roadway is advisable on sharp curves. This will allow for such factors as 1 the tendency for drivers to shy away from the pavement edge, 2 increased effective transverse vehicle width because the front and rear wheels do not track, and 3 added width because of the slanted position of the front of the vehicle to the roadway centerline. For 24-ft roadways, the added width is so small that it can be neglected. Only for 30mph design speeds and curves sharper than 22°does the added width reach 2 ft. For narrower pavements, however, widening assumes importance even on fairly flat curves. Recommended amounts of and procedures for curve widening are given in Geometric Design for Highways.2. GradesThe vertical alignment of the roadway and its effect on the safe and economical operation of the motor vehicle constitute one of the most important features of road design. The vertical alignment, which consists of a series of straight lines connected by vertical parabolic or circular curves, is known as the “grade line.” When the grade line is increasing from the horizontal it is known as a “plus grade,” and when it is decreasing from the horizontal it is known as a “minus grade.” In analyzing grade and grade controls, the designer usually studies the effect of change in grade on the centerline profile.In the establishment of a grade, an ideal situation is one inwhich the cut is balanced against the fill without a great deal of borrow or an excess of cut to be wasted. All hauls should be downhill if possible and not too long. The grade should follow the general terrain and rise and fall in the direction of the existing drainage. In mountainous country the grade may be set to balance excavation against embankment as a clue toward least overall cost. In flat or prairie country it will be approximately parallel to the ground surface but sufficiently above it to allow surface drainage and, where necessary, to permit the wind to clear drifting snow. Where the road approaches or follows along streams, the height of the grade line may be dictated by the expected level of flood water. Under all conditions, smooth, flowing grade lines are preferable to choppy ones of many short straight sections connected with short vertical curves.Changes of grade from plus to minus should be placed in cuts, and changes from a minus grade to a plus grade should be placed in fills. This will generally give a good design, and many times it will avoid the appearance of building hills and producing depressions contrary to the general existing contours of the land. Other considerations for determining the grade line may be of more importance than the balancing of cuts and fills.Urban projects usually require a more detailed study of the controls and finer adjustment of elevations than do rural projects. It is often best to adjust the grade to meet existing conditions because of the additional expense of doing otherwise.In the analysis of grade and grade control, one of the most important considerations is the effect of grades on the operating costs of the motor vehicle. An increase in gasoline consumption and a reduction in speed are apparent when grades are increase in gasoline consumption and a reduction in speed is apparent when grades are increased. An economical approach would be to balancethe added annual cost of grade reduction against the added annual cost of vehicle operation without grade reduction. An accurate solution to the problem depends on the knowledge of traffic volume and type, which can be obtained only by means of a traffic survey.While maximum grades vary a great deal in various states, AASHTO recommendations make maximum grades dependent on design speed and topography. Present practice limits grades to 5 percent of a design speed of 70 mph. For a design speed of 30 mph, maximum grades typically range from 7 to 12 percent, depending on topography. Wherever long sustained grades are used, the designer should not substantially exceed the critical length of grade without the provision of climbing lanes for slow-moving vehicles. Critical grade lengths vary from 1700 ft for a 3 percent grade to 500 ft for an 8 percent grade.Long sustained grades should be less than the maximum grade on any particular section of a highway. It is often preferred to break the long sustained uniform grade by placing steeper grades at the bottom and lightening the grade near the top of the ascent. Dips in the profile grade in which vehicles may be hidden from view should also be avoided. Maximum grade for highway is 9 percent. Standards setting minimum grades are of importance only when surface drainage is a problem as when water must be carried away in a gutter or roadside ditch. In such instances the AASHTO suggests a minimum of %.3. Sight DistanceFor safe vehicle operation, highway must be designed to give drivers a sufficient distance or clear version ahead so that they can avoid unexpected obstacles and can pass slower vehicles without danger. Sight distance is the length of highway visible ahead to the driver of a vehicle. The concept of safe sight distance has two facets: “stopping” or “no passing” and “passing”.At times large objects may drop into a roadway and will do seriousdamage to a motor vehicle that strikes them. Again a car or truck may be forced to stop in the traffic lane in the path of following vehicles. In dither instance, proper design requires that such hazards become visible at distances great enough that drivers can stop before hitting them. Further more, it is unsafe to assume that one oncoming vehicle may avoid trouble by leaving the lane in which it is traveling, for this might result in loss of control or collision with another vehicle.Stopping sight distance is made up of two elements. The first is the distance traveled after the obstruction comes into view but before the driver applies his brakes. During this period of perception and reaction, the vehicle travels at its initial velocity. The second distance is consumed while the driver brakes the vehicle to a stop. The first of these two distances is dependent on the speed of the vehicle and the perception time and brake-reaction time of the operator. The second distance depends on the speed of the vehicle; the condition of brakes, times, and roadway surface; and the alignment and grade of the highway.On two-lane highways, opportunity to pass slow-moving vehicles must be provided at intervals. Otherwise capacity decreases and accidents increase as impatient drivers risk head-on collisions by passing when it is unsafe to do so. The minimum distance ahead that must be clear to permit safe passing is called the passing sight distance. In deciding whether or not to pass another vehicle, the driver must weigh the clear distance available to him against the distance required to carry out the sequence of events that make up the passing maneuver. Among the factors that will influence his decision are the degree of caution that he exercises and the accelerating ability of his vehicle. Because humans differ markedly, passing practices, which depend largely on human judgment and behavior rather than on the laws of mechanics, vary considerablyamong drivers.The geometric design is to ensure highway traffic safety foundation, the highway construction projects around the other highway on geometric design, therefore, in the geometry of the highway design process, if appear any unsafe potential factors, or low levels of combination of design, will affect the whole highway geometric design quality, and the safety of the traffic to bring adverse impact. So, on the geometry of the highway design must be focus on.公路几何设计公路是供汽车或其他车辆行驶的一种线形带状结构体.它是由路基、路面、桥梁、涵洞和隧道组成.此外,它还有路线交叉、工程和交通工程及沿线设施.路基是路面、路肩、边坡、等部分的基础.它是按照路线的平面位置在地面上开挖和成的土物.路基作为行车部分的基础,必须保证它有足够的强度和稳定性,可以防止水及其他自然灾害的侵蚀.路面是公路表面的部分.它是用混合料铺筑的单层或多层结构物.路面要求光滑,具有足够的强度,稳定性好和抗湿滑功能.路面质量的好环,直接影响到行车的安全性、舒适性和通行.公路几何线形设计要考虑公路平面线形、纵断面线形两种线形以及横断面的组成相协调,还要注意视距的畅通等等.确定公路几何线形时,在考虑地形、地物、土地的合理利用及环境保护因素时,要充分利用公路几何组成部分的合理尺寸和线形组合.1、线形设计道路的线形反映在平面图上是由一系列的直线和与直线相连的圆曲线构成的.现代设计时常在直线与圆曲线之间插入缓和曲线.线形应是连续的,应避免平缓线形到小半径曲线的突变或者长直线末端与小半径曲线相连接的突然变化,否则会发生交通事故.同样,不同半径的圆弧首尾相接曲线或在两半径不同的圆弧之间插入短直线都是不良的线形,除非在圆弧之间插入缓和曲线.长而平缓的曲线在任何时候都是可取的,因为这种曲线线形优美,将来也不会废弃.然而,双向道路线形全由曲线构成也是不理想的,因为一些驾驶员通过曲线路段时总是犹豫.长而缓的曲线应用在拐角较小的地方.如果采用短曲线,则会出现“扭结”.另外,线路的平、纵断面设计应综合考虑,而不应只顾其一,不顾其二,例如,当平曲线的起点位于竖曲线的顶点附近时将会产生严重的交通事故.行驶在曲线路段上的车辆受到离心力的作用,就需要一个大小相同方向相反的由超高和侧向磨擦提供的力抵消它,这些控制值对于某一规定设计车速可能采用曲线的曲率作了限制.通常情况下,某一圆曲线的曲率是由其半径来体现的.而对于线形设计而言,曲率常常通过曲线的程度来描述,即100英尺长的曲线所对应的中心角,曲线的程度与曲线的半径成反比.公路的直线地段设置正常的路拱,而曲线地段则设置超高,在正常断面与超高断面之间必须设置过渡渐变路段.通常的做法是维持道路每一条中线设计标高不变,通过抬高外侧边缘,降低内侧边缘以形成所需的超高,对于直线与圆曲线直接相连的线形,超高应从未到达曲线之前的直线上开始,在曲线顶点另一端一定距离以外达到全部超高.如果车辆以高速度行驶在直线与小半径的圆曲线相连的路段,行车是极不舒服.汽车驶近曲线路段时,超高开始,车辆向内侧倾斜,但乘客须维持身体的垂直状态,因为此时未受到离心力的作用.当汽车到达曲线路段时,离心力突然产生,迫使乘客向外倾斜,为了维持平衡,乘客必须迫使自己的身体向内侧倾斜.由于剩余超高发挥作用,乘客须作进一步的姿势的调整.当汽车离开曲线时,上述过程刚好相反.插入缓和曲线后,半径从无穷大逐渐过渡到圆曲线上的某一固定值,离心力逐渐增大,沿缓和曲线心设置超高,离心力平稳逐渐增加,避免了行车颠簸.缓和曲线在铁路上已经使用多年,但在公路上最近才得以应用,这是可以理解的.火车必须遵循精确的运行轨道,采用缓和曲线后,上述那种不舒服的感觉才能消除.然而,汽车司机在公路上可以随意改变侧向位置,通过迂回进入圆曲线来为自己提供缓和曲线.但是在一个车道上有时在其他车道上做这种迂回行驶是非常危险的.设计合理的缓和曲线使得上述迂回没有必要.主要是出于安全原因,公路部门广泛采用了缓和曲线.对于半径相同的圆曲线来说,在未端加上缓和曲线就会改变曲线与直线的相关位置,因此应在最终定线勘测之前应决定是否采用缓和曲线.一般曲线的起点标为PC或BC,终点标为PT或EC.对含有缓和曲线的曲线,通常的标记配置增为：TC、SC、CS和ST.对于双向道路,急弯处应增加路面宽度,这主要基于以下因素：1驾驶员害怕驶出路面边缘；2由于车辆前轮和后轮的行驶轨迹不同,车辆有效横向宽度加大；3车辆前方相对于公路中线倾斜而增加的宽度.对于宽度为24英尺的道路,增加的宽度很小,可以忽略.只有当设计车速为30mile/h,且曲度大于22℃时,加宽可达2英尺.然而,对于较窄的路面,即使是在较平缓的曲线路段上,加宽也是很重要推荐加宽值及加宽设计见公路线形设计2、纵坡线公路的竖向线形及其对车辆运行的安全性和经济性的影响构成了公路设计中最重要的要素之一.竖向线形由直线和竖向抛物线或圆曲线组成,称为纵坡线.纵坡线从水平线逐渐上升时称为坡度变化的影响.在确定坡度时最理想的情况是挖方与填方平衡,没有大量的借方或弃方.所有运土都尽可能下坡运并且距离不长,坡度应随地形而变,并且与既有排水系统的升、降方向一致.在山区,坡度要使得挖填平衡以使总成本最低.在平原或草原地区,坡度与地表近似平行,介是高于地表足够的高度,以利于路面排水,苦有必要,可利用风力来清除表面积雪.如公路接近或沿河流走行,纵坡线的高度由预期洪水位来决定.无论在何种情况下,平缓连续的坡度线要比由短直线段连接短竖曲线构成的不断变向的坡度线好得多.由上坡向下坡变化的路段应设在挖方路段,而由下坡向上坡变化的路段应设在填方路段,这样的线形设计较好,往往可以避免形成与现状地貌相反的圭堆或是凹地.与挖填方平衡相比,在确定纵坡线时,其他考虑则重要得多.城市项目通常比农村项目要求对控制要素进行更详尽的研究,对高程进行更细致地调整.一般来说,设计与现有条件相符的坡度较好,这样可避免一些不必要的花费.在坡度的分析和控制中,坡度对机动车运行费用的影响是最重要的考虑因素之一.坡度增大油耗显然增大,车速就要减慢.一个较为经济的方案则可使坡度减小而增加的年度成本与坡度不减而增加的车辆运行年度成本之间相平衡.这个问题的准确方法取决于对交通流量和交通类型的了解,这只有通过交通调查才能获知.在不同的州,最大纵坡也相差悬殊,AASHTO标准建议由设计车速和地形来选择最大纵坡.现行设计以设计车速为70mile/h时最大纵坡为5%,设计车速30mile/h时,根据地形不同,最大纵坡一般为7％－12％.当采用较长的待续爬坡时,在没有为慢行车辆提供爬坡道时,坡长不能够超过临界坡长.临界坡长可从3％纵坡的1700英尺变化至8%纵坡的500英尺.持续长坡的坡度必须小于公路任何一个断面的最大坡度,通常将长的持续单一纵坡断开,设计成底部为一陡坡,而接近坡顶则让坡度减小.同时还要避免由于断面倾斜而造成的视野受阻.调整公路的最大纵坡为9%只有当路面排水成问题时,如水必须排至边沟或排水沟,最小坡度标准才显示其重要性.这种情况下,AASHTO标准建议最小坡度为%.3、视距为保证行车安全,公路设计必须使得驾驶员视线前方有足够的一段距离,使他们能够避让意外的障碍物,或者安全地超车.视距就是车辆驾驶员前方可见的公路长度.安全视距具有两方面含义：“停车视距”或“不超车视距”或“超车视距”.有时,大件物体也许会掉到路上,会对撞上去的车辆造成严重的危害.同样,轿车或卡车也可能会被一溜车辆阻在车道上.无论是哪种情况发生,合理设计要求驾驶员在一段距离以外就能看见这种险情,并在撞上去之前把车刹住.此外,认为车辆通过离开所行驶的车道就可以躲避危险的想法是不安全的,因为这会导致车辆失控或与另一辆车相撞.停车视距由两部分组成：第一部分是当驾驶员发现障碍物面作出制动之前驶过的一段距离,在这一察觉与反应阶段,车辆以其初始速度行驶；第二部分是驾驶员刹车后车辆所驶过的一段距离.第一部分停车视距取决于车速及驾驶员的察觉时间和制动时间.第二部分停车视距取决于车速、刹车、轮胎、路面的条件以及公路的线形的坡度.在双车道公路上,每间隔一定距离,就应该提供超越慢行车辆的机会.否则,公路容量将降低,事故将增多,因为急燥的驾驶员在不能安全超车时冒着撞车危险强行超车,能被看清的允许安全超车的前方最小距离叫做超车视距.驾驶员在做出是否超车的决定时,必须将前方的能见距离与完成超车动作所需的距离对比考虑.影响他做出决定的因素是开车的小心程度和车辆加速性能.由于人与人的显着差别,主要是人的判断和动作而不是力学定理决定的超车行为随着驾驶员的不同而大不相同.公路是确保交通安全的基础,建设的其他项目都围绕的而展开,因此,在的过程中,如果出现任意的不安全潜在因素,或者低水平的组合,都会影响到整个的质量,并对交通的安全带来不利影响.因此对于的必须予以重点关注.。

桥梁设计外文翻译文献(文档含中英文对照即英文原文和中文翻译) 原文：A Bridge For All CenturiesAn extremely long-and record setting-main span was designed for the second bridge to across the Panama Canal in order to meet the owner’s requirement that no piers be placed in the water.Because no disruption of canal traffic was permitted at any time,the cable-stayed bridge of cast-in-place cancrete was carefully constructed using the balanced-cantilever method.In 1962 ,the Bridge of Americas(Puente de las America) opened to traffic,serving as the only fixed link across the Panama Canal .The bridge was designed to carry 60,000 vehicles per day on four lanes, but it has beenoperating above its capacity for many years.Toalleviate bottlenecks on the route that the bridge carries over the canal-the Pan-AmericanHighway(Inter-American Highway)-and promotegrowth on the western side of Panama,the country’s Ministry of Public Works(Ministerio de Obras Publicas,or MOP )decided to build a new highway systerm linking the northern part of Panama City,on the eastern side of the canal, to the town of Arraijan,located on the western side of the canal.The Centennial Bridge –named to commemorate 100 years of Panamanian independence-has noe been constructed and, when opend, will carry six lanes of traffic. This cable-stayed bridge of cast-in-place cancrete features a main span of 420m,the longest such span for this type of bridge in the Western Hemisphere.In 200 the MOP invited international bridge design firms to compete for the design of the crossing, requesting a two-package proposal:one techinical, the other financial. A total of eight proposals were received by December 2000 from established bridge design firms all over the world. After short-listing three firms on the basis of the technical merits of their proposals, the MOP selected T.Y.Lin International, of San Francisco, to prepare the bridge design and provide field construction support based on the firm’s financial package.The Centennial Bridge desige process was unique and aggressive,incorporating concepts from the traditional design/build/bid method, the design/build method , and the sa-called fast-track design process.To complete the construction on time-that is ,within just 27 months-the design of the bridge was carried out to a level of 30 percent before construction bidding began, in December 2001.The selected contractor-the Wiesbaden,Germany,office of Bilfinger Berger,AG-was brought on board immediately after being selected by the MOP ,just as would be the case in a fast-track approach. The desige of the bridge was then completed in conjunction with construction , a process that id similan to desige/build.The design selected by the client features two single-mast towers,each supporting two sets of stay cables that align in one vertical plane.Concrete was used to construct both the towers and the box girder deck,as well as the approach structures.The MOP , in conjunction with the Panama Canal Authority,established the following requirements for the bridge design :A 420m,the minimum length for the main span to accommodate the recently widened Gaillard Cut,a narrow portion of the canal crossing the Continental Divide that was straightened and widened to 275m in 2002;A navigational envelope consisting of 80m of vertical clearance and 70mof horizontal clearance to accommodate the safe passage of a crane of World War 11 vintage-a gift from the ernment that is used by the Panama Canal Authority to maintain the canal gates and facilities;A roadway wide enough to carry six lanes of traffic, three in each direction;A deck able to accommodate a 1.5m wide pedestrian walkway;A design that would adhere to the American Association of State Highway and Transportation Official standard for a 100-year service life and offer HS-25 truck loading;A structure that could carry two 0.6m dianeter water lines;A construction method that would not cross the canal at any time or interrupt canal operationa in any way.Because of the bridge’s long main span and the potential for strong seismic activity in the area,no single building code covered all aspects of the project.Therefore the team from T.Y. Lin International determinded which portions of several standard bridge specifications were applicable and which were not.The following design codes were used in developing the design criteria for the bridge，it is standard specifications for highway bridge ,16th ed,1996It was paramount that the towers of the cable-stayed structucture be erected on land to avoid potential ship collision and the need to construct expensive deep foundation in water. However, geological maps and boring logs produced during the preliminary design phrase revealed that the east and west banks of the canal, where the towers were to be located, featured vastly different geologicaland soil conditions. On the east side of the canal, beneath shallow layers of overburden that rangs in consistency from soft to hard, lies a block of basalt ranging from medium hard to hard with very closely spaced joint.The engineers determined that the basalt would provide a competent platform for the construction of shallow foundation for tower, piers, and approach structures on this side of bridge.The west side, however,featured the infamous Cucaracha Formation, which is a heterogeneous conglomerate of clay shale with inclusions of sandstone, basalt,and ash that is prone to landslide. As a sudsurface stratum the Cucaracha Formation is quite stable,but it quickly erodes when exposed to the elements. The engineers determined that deep foundations would therefore be needed for the western approach structure,the west tower,and the western piers.Before a detailed design of the foundationa could be developed,a thorough analysis of the seismic hazards at the site was required,The design seismic load for the project was developed on the basis of a probabilistic seismic hazard assessment that considered the conditions at the site.Such an assessment establishes the return period for a given earthquake and the corresponding intensity of ground shaking in the horizontal directtion in terms of an acceleration response spectrum.The PSHA determined two dominant seismic sources: a subduction source zone associated with the North Panama Deformed Belt capable of producing a seimic event as strong as 7.7MW,and the Rio Gatun Fault, capable of producing an event as strong as 6.5MW.The 7.7MW NPDB event was used as the safety evluation earthquake,that is,the maximum earthquake that could strike without putting the bridge out of service.The damage to the bridge would be minor but would require some closures of the bridge.The 6.5MWRio Gatun Fault event was used as the foundational evaluation earthquake,a lower-level temblor that would cause minimal damage to the bridge and would not require closures.For the FEE load case,the SEE loading was scaled back by two-thirds.The FEE is assumed to have a peak acceleration of 0.21g and a return period of 500 years; the probability that it will be exceeded within 50 years is 10 pencent and within 100 years,18 persent.The SEE is assumed to have a peak acceleration of 1.33g and a return period of 2,500 years;the probability that it will be exceeded within 50 years is 2 pencent and within 100 years,4 persent.Because of uncertainty about the direction from which the seismic waves would approach the site, a single response spectrum-a curve showing the mathematically computed maximum response of a set of simple damped harmonic oscillators of different natural frequencies to a particular earthquake ground acceleration-was used to characterize mitions in two mutually orthogonal directions in the horizontal plane.To conduct a time-history analysis of the bridge’s multiple supports,a set of synthetic motions with three components-longitudinal,transverse,and vertical-was developd using an iterative technique.Recorded ground motions from an earthquake in Chile in 1985 were used as “seed”motions for the sythesis process.A time delay estimate-that is,an estimate of the time it would take for the motions generated by the SEEand FEE earthquakes to travel from one point to the next-was create using the assumed seismic wave velocity and the distance between the piers of the ing an assumed was velocity of approximately 2.5km/s,a delay on the order of half a second to a secondis appropriate for a bridge 1 to 2km long.Soil-foundation interaction studies were performed to determine the stiffness of the soil and foundation as well as the seismic excitation measurement that would be used in the dynamic analyses.The studieswere conducted by means of soil-pile models using linear and nonlinear soil layera of varying depths.The equivalent pile lengths in the studies-that is, the lengths representing the portions of a given pile that would actually be affected by a given earthquake-induced ground motion-ranged from2to10m.In such a three-dimensional model,there are six ways in which the soil can resist the movement of the lpile because of its stiffness:throngh axial force in the three directions and through bending moments in three directions.Because the bridge site contains so many layers of varying soil types,each layer had to be represented by a different stiffness matrix and then analyzed.Once the above analyses were completed,the T.Y.Lin International engineers-taking into consideration the project requirements developedby the owener-evaluated several different concrete cable-stayed designs.A number of structural systems were investigated,the main variables,superstructure cross sections,and the varying support conditions described above.The requirement that the evevation of the deck be quite high strongly influenced the tower configuration.For the proposed deck elevation of more than 80m,the most economical tower shapes included single-and dual-mast towers as well as “goal post”towers-that is,a design in which the two masts would be linked to each other by crossbeams.Ultimately the engineers designd the bridge to be 34.3m wide with a 420mlong cable-stayd main span,two 200mlong side spans-one on each side of the main span-and approach structures at the ends of the side spans.On the east side there is one 46m long concrete approach structure,while on the west side there are three,measuring 60,60,and 66m,for a total bridge length of 1,052m.The side spans are supported by four piers,referred to,from west to east,as P1.P2,P3,and P4.The bridge deck is a continuous single-cell box girder from abutment to abutment; the expansion joints are located at the abutments only. Deck movements on the order of 400 mm are expected at these modular expansion joints Multidirectional pot bearings are used at the piers and at the abutments to accommodate these movements.The deck was fixed to the two towers to facilitate the balanced-cantilevermethod of construction and to provide torsional rigidity and lateral restraint to the deck.. Transverse live loads, seismic loads, and wind loads are proportionally distributed to the towers and the piers by the fixity of the deck to the towers and by reinforced-concrete shear keys located at the top of P1, P3, and P4. The deck is allowed to move longitudinally over the abutments and piers. The longitudinal, seismic, live, and temperature loads are absorbed by what is known as portal frame structural behavior, whereby the towers and the deck form a portal-much like the frame of a door in a building-that acts in proportion to the relative stiffness of the two towers.As previously mentioned, the presence of competent basalt on the east side of the site meant that shallow foundations could be used there; in particular, spread footings were designed for the east tower, the east approach structure, and the east abutment. The west tower, the west approach structure, and the western piers (P2 and P3), however, had to be founded deep within the Cucaracha Formation. A total of 48 cast-in-drilled-hole (CIDH) shafts with 2 m outer diameters and lengths ranging from 25 to 35 m were required. A moment curvature analysis was performed to determine the capacity of the shafts with different amounts of longitudinal steel rebar. The results were plotted against the demands, and on the basis of the results the amount of required longitudinal reinforcing steel was determined to be 1 percent of the amount of concrete used in the shafts. The distribution of the longitudinal reinforcing steel was established by following code requirements, with consideration also given to the limitations of constructing CIDH piles with the contractor’s preferred method, which is the water or slurry displacement method.A minimum amount of transverse steel had to be determined for use in the plastic regions of the shaft-that is, those at the top one-eighth of eighth of each shaft and within the shaft caps, which would absorb the highest seismic demands. Once this amount was determined, it was used as the minimum for areas of the shafts above their points of fixity where large lateral displacements were expected to occur. The locations of the transverse steel were then established by following code requirements and by considering the construction limitations of CIDH piles. The transverse steel was spiral shaped.Even though thief foundation designs differed, the towers themselves were designed to be identical. Each measures 185.5 m from the top of its pile cap and is designed as a hollow reinforced-concrete shaft with a truncated elliptical cross section (see figure opposite). Each tower’s width in plan varies along its height, narrowing uniformly from 9.5 m at the base of the tower to 6 m at the top. In the longitudinal direction, each pylon tapers from 9.5 m at the base to about 8 m right below the deck level,which is about 87 m above the tower base. Above the deck level the tower’s sections vary from 4.6 m just above the deck to 4.5 m at the top. Each tower was designed with a 2 by 4 m opening for pedestrian passage along the deck, a design challenge requiring careful detailing.The towers were designed in a accordance with the latest provisions of the ATC earthquake design manual mentioned previously (ATC-32). Owing to the portal frame action along the bridge’s longitudinal axis, special seismic detailing was implemented in regions with the potential to develop plastic hinges in the event of seismic activity-specifically, just below the deck and above the footing. Special confining forces and alternating open stirrups-with 90 and 135 degree hooks-within the perimeter of the tower shaft.In the transverse direction, the tower behaves like a cantilever, requiring concrete-confining steel at its base. Special attention was needed at the joint between the tower and the deck because of the central-plane stay-cable arrangement, it was necessary to provide sufficient torsional stiffness and special detailing at the pier-to-deck intersection. This intersection is highly congested with vertical reinforcing steel, the closely spaced confining stirrups of the tower shaft, and the deck prestressing and reinforcement.The approach structures on either side of the main span are supported on hollow reinforced-concrete piers that measure 8.28 by 5 m in plan. The design and detailing of the piers are consistent with the latest versions of the ATC and AASHTO specifications for seismic design. Capacity design concepts were applied to the design of the piers. This approach required the use of seismic modeling with moment curvature elements to capture the inelastic behavior of elements during seismic excitation. Pushover analyses of the piers were performed to calculate the displacement capacity of the piers and to compare them with the deformations computed in the seismic time-history analyses. To ensure an adequate ductility of the piers-an essential feature of the capacity design approach-it was necessary to provide adequate concrete-confining steel at those locations within the pier bases where plastic hinges are expected to form.The deck of the cable-stayed main span is composed of single-cell box girders of cast-in-place concrete with internal, inclined steel struts and transverse posttensioned ribs, or stiffening beams, toward the tops. Each box girder segment is 4.5 m deep and 6 m long. To facilitate construction and enhance the bridge’s elegant design, similar sizes were used for the other bridge spans. An integral concrete overlay with a thickness of 350 mm was installed instead of an applied concrete overlayon the deck. In contrast to an applied overlay, the integral overlay was cast along with each segment during the deck erection. Diamond grinding equipment was used to obtain the desired surface profile and required smoothness. The minimum grinding depth was 5 mm.A total of 128 stay cables were used, the largest comprising 83 monostrands. All cables with a length of more than 80 m were equipped at their lower ends with internal hydraulic dampers. Corrosion protection for the monostrands involved galvanization of the wires through hot dipping, a tight high-density polyethylene (HDPE) sheath extruded onto each strand, and a special type of petroleum wax that fills all of the voids between the wires.The stays are spaecd every 6 m and are arranged in a fan pattern.They are designed to be stressed from the tower only and are anchored in line with a continuous stiffening beam at the centerline of the deck.The deck anchorage system is actually a composite steel frame that encapsulates two continous steel plates that anchor the stays and transfer the stay forces in a continuous and repetitive system-via shear studs-throuthout the extent of the cable-supported deck (see figure above).A steel frame was designed to transfer the stays’horizontal forces to the box girders through concrete-embedded longitudinal steel plates and to transfer the boxes’ vertical forces directly through the internal steel struts.This innovative and elegant load transfer system made rapid construction of the concrete deck segments-in cycles of three to five days-possible.In addition to the geotechnical and seismic analyses,several structural analyses were performed to accurately capture the behavior of this complex bridge.For the service-load analysis,which includes live,temperature,and wind loads,the engineers used SAP2000, a computer program created and maintained by Computers &Structrures,Inc.(CSI), of Berkeley, California.This program was selected for its ability to easily model the service loads and to account for tridimensional effects.For correct SAP2000 modeling, it was necessary to define a set of initial stresses on the cables, deck, and tower elements to capture the state of the structure at the end of construction.For the calculation of those initial stresses, a series of iterations on the basic model were performed to obtain the stay forces in the structure that balance both the bridges’s self-weight and the superimposed dead loads. Once the correct cable stiffness and stress distribution were obtained, all subsequent service-load analyses were performed to account for the geometric stiffness and P-deltaeffects, which consider the magnitude of an applied load (P) versus the displacement(delta).The seismic analysis of the structure was conducted using the SADSAP structural analysis program, also a CSI product, based on the differences in seismic motions that will be experienced at the different piers based on their distance from one another.This sophisticated program has the capability to model inelastic behavior in that flexural plastic hinges can readily be simulated.Plastic hinge elements were modeled at varous locations along the structure where the results from a preliminary response spectrum analysis in SAP2000 indicated that inelastic behavior might be expected.The time-history records pertaining to the site were used in conjunction with the SADSAP model to botain a performace-based design of the piers and towers and to verifh the design of several deck stctions.As previously mentioned,the construction contractor was brought on board early in the process;the company’s bid of $93 million was accepted and the project was awarded in March 2002.To guarantee unimpeded canal traffic,the bridge had to be constructed without the use of the canal waters.To accomplish this, the cast-in-place main-pain superstructure was erected using the balanced-cantilever method.Form travelers were used to accomplish this, and they were designed in such a way that they could be used as an integral part of the pier tables’falsework.After assembly on the ground, two 380 Mg form travelers were raised independently into the pier table casting position and connected to each other.After an initial learning period, the contractor was able to achieve a four-day cycle for the casting of the cantilevered deck segments, an achievement that greatly enhanced the ability of the team to construct the project on time.Once the side-span and mai-span closures were cast, the travelers had to be removed from locations adjacent to the towers rather than over water so as to avoid any influence on canal traffic.To save time, the towers approach structure, and piers were built simultaneously.The approach viaducts were designed and built using the span-by-span erection method by means of an underslung suupport truss.The east viaduct span was built first and the support truss was then removed and transferred to the west side so that it could be used to build the three spans of the west viaduct, one span at a time.The bridge construction was completeed in Auguse 2004 at a cost of approximately $2,780 per square meter.Its opening awaits the completion of the rest of the highway it serves.跨越世纪之桥1962年，横跨巴拿马运河的美国大桥作为仅有的固定连接开放交通车。

毕业设计(论文)外文资料翻译系别：专业：班级：姓名：学号：外文出处：土木工程网附件： A.英文文献； B. 译文附录A英文文献BridgesBridges are great symbols of mankind’s conquest of space.The sight of the crimson tracery of the Golden Gate Bridge against a setting sun in the Pacific Ocean, or the atch of the Garabit Biaduct soaring triumphantly above the deep gorge. Fills one’s heart with wonder and admiration for the art of their builders[11]. They are the enduring expressions of mankind’s determination to remove all barriers in its pursuit of a better and freer world. Their design and building schemes are conceived in dream-like bisions. But vision and determination are not enough. All the physical forces of nature and gravity must be understood with mathematical precision and such forces have to be resisted by manipulating the right materials in the right pattern. This requires both the inspiration of an artist and the skill of an artisan.Scientific knowledge about materials and structural behavior has expanded tremendously, and computing techniques are now widely available to manipulate complex theories in innumerable ways very quickly. Engineers have virtually revolutionized bridge design and construction methods in the past decade. The advances apply to short-medium and long-span bridges.For permanent bridge，the most commonly used materials are steel and concrete. Bridge of many different type are built with these materials, used singly or in combination. Timber may be used for temporary above-water construction, for the elements of a structure that lie below the waterline (particularly timber pile s), or for short-span bridges located on secondary roads. A few short-span aluminum bridges have been built in the United States on an experimental basis.The principal portions of a bridge may be said to be the “substructure” and the “superstructure.” This division is used here simply for convenience, since in many bridges there is no clear dividing lint between the two.Common elements of the substructure are abutments (usually at the bridge ends) and piers (between the abutments).Piers and abutments often rest on separately constructed foundations such as concrete spread footings or groups of bearing piles;these foundations are part of the substructure. Occasionally a bridge substructure comprises a series of pile bents in which the piles extend above the waterline and are topped by a pile cap that, in turn, supports the major structural elements of the superstructure. Such bents often are used in arepetitive fashion as part of along, low, over-water crossing.In recent years, the dividing lines between short-medium and long-span bridge have blurred somewhat. Currently, spans of 20 to 100 ft (6.1 to 30.5m) are regarded as short by many designers, who have developed many standardized designs to handle these spans economically. Medium spans range up to, per-haps, 400ft (121.9m) in modern bridge practice, depending on the organization involved and the materials used. Long spans range up to 4000ft (1219.2m) or more, but a clear span above 1000ft (304.8m)is comparatively rare.In the United States, highway bridges generally must meet loading, design, and construction requirements of the AASHTO Specification. The design and construction of railway bridges are governed by provisions of the AREA Manual for Railway Engineering. Design requirements for pedestrian crossings and bridges serving other purposes may be established by local or regional codes and specifications. ACI Code provisions are often incorporated by reference, and in most cases serve as model provisions for other governing documents.Bridge spans to about 100 ft often consist of pre-cast integral-deck units. These units offer low initial cost, minimum maintenance, and fast easy constrction, with traffic interruption. Such girders are generally pretensioned, the units are placed side by side, and are often post-tensioned laterally at intermediate diaphragm lacations, After which shear keys between adjacent units are filled with non-shrinking mortar. For highway spans, an asphalt wearing surface may be applied directly to the top of the pre-cast concrete. In some cases, a cast-in-place slab is placed to provide composite action.For medium-span highway bridges, to about 120 ft, AASHTO standard I beams are generally used. he are intended for use with a composite cast-in-place roadway slab. Such girders often combine pre-tensioning of the pre-cast member withpost-tensioning of the composite beam after the deck is placed.Pre-cast girders may not be used for spans much in excess of 120 ft because of the problems of transporting and erecting large, heavy units. On the other hand, there is a clear trend toward the use of longer spans for bridges. Highway safety is improved by eliminating central piers and moving outer piers away from the edge of divided highways. For elevated urban expressways, long spans facilitate access and minimize obstruction to activities below. Concern for environmental damage has led to the choice of long spans for continuous viaducts. For river crossing, intermediate piers may be impossible because of requirements of navigational clearance.Such requirements have led to the development in Europe, and more recently in the western hemisphere, of long span segmental pre-stressed concrete box girder bridges. In typical construction of this type, piers are cast-in-place, often using the slip-forming technique. A “hammerhead” section of box girder is then cast at the top of the pier, and construction proceeds in each direction by the balanced cantilever method. The construction is advanced using either cast-in-place or pre-cast segments, each post-tensioned to the previously completed construction. Finally, after the closing cast-in-place joint is made at mid-span, the structure is further post-tensioned for full continuity.Bridge may also be classed as “deck” or “through” types. In the deck type of bridge, the roadway is above the supporting structure; that is, the load-carrying elements of the superstructure are below the roadway. In the through type of bridge, the roadway passes between the elements of the super-structure, as in a through steel-truss bridge. Deck structures predominate: they have a clean appearance, provide the motorist with a better view of the surrounding area, and are easier to widen if future traffic requires it.Examples of short-span concrete bridges include cast-in-lace, reinforced concrete beam (and slab);simple-span, pre-stressed (this type incorporates pre-cast, pre-stressed I-girders or box girders topped by a cast-in-place deck);and cast-in place box girder.The designer of each medium-and long-span bridge tries to devise a structurethat is best suited to the conditions encountered at that particular location. The result is an almost bewildering variety of structures that differ either in basic design principles or in design details.General categories of steel bridge are briefly described in the following paragraphs.Girder bridges come in two basic varieties-plate and box girders.Plate girders are used in the United States for medium spans. They generally are continuous structures with maximum depth of girder over the piers and minimum depth at mid-span. The plate girders generally have an I cross section; they are arranged in lines that support stringers, floor-beams, and, generally, a cast-in-lace concrete deck. The girders are shop-fabricated by welding; field connections generally are by high-strength bolts.Welded-steel box girder structures are generally similar to plate girder spans except for the configuration of the bridge cross section.Rigid frames are used occasionally, most often for spans in the range of 75 to 100 ft (22.9 to 30.5 m) and for grade0separation structures.Arch bridges are used for longer spans at locations where intermediate piers cannot be used and where good rock is available to withstand the thrusts at the arch abutments.Variations in the arch bridge are specially suited in the span range of 200 to 500m and thus provide a transition between the continuous box girder bridge and the stiffened suspension cable. The cables provided above the deck and connected to the towers would permit elimination of intermediate piers facilitating a larger width for purposes of navigation. Because of the damping effect of inclined cables, the cable-stayed decks are less prone to wind-induced oscillations than suspension bridges.Suspension bridges are used for very long spans or for shorter spans where intermediate piers cannot be built. An example is the Verrazano Narrows Bridge which was completed in 1964.The $305 million,4260ft(1298.5m)structure spans the entrance to New York Harbor to join Staten Island and Brooklyn.Concrete bridges come in nearly as great a variety as do steel bridges.The bridge construction in France benefits by a strong growth in rail and highway infrastructures. For the time being the competition with other material turns to the advantage of composite bridge solutions. Before presenting any features concerning the recent trends in composite bridge design it is important to clarify, the bridge market, through the analysis of some statistical data.In France, there is a very limited market for long span bridges. In the recent construction, the demand for bridges of span length higher than 200m is rather exceptional. The main market is for bridges of span length (or multi span length) less than 100m.In France 800 to 1200 bridges are built every year, which represent about 300,000m to 500,000m of deck surface. However the majority of bridges being erected each year are of small span length. Less than 10% of the bridge patrimony have span. Length greater than 30m and deck surface greater than 1000 m2. Now that the market has been identified lets have an idea, in term of competitiveness, of the French market situation between several bridge types. In 1977 less than 2.5%.Of bridges were steel or composite bridges. The steel-concrete composite construction has continued to grow steadily over the last 15 years. This trend is mainly attributable to the gain in competitiveness of composite bridges against reinforcedand prestressed concrete bridges.For short span length the majority of steel bridges is of concrete type. Bridges composed of steel beams encased in concrete are very often used for railway bridges of small span length in order to meet stiffness requirements.The recent statistical evaluation, performed by SETRA [1] on the bridges recently built in France between 1990 to 1993 by various owners (State, Highway concession companies, Departments and Communities, SNCF) shows that the competitive span length range for steel and concrete composite bridges is between 30 and 110 m with a very distinctive peak for the interval 60 to 80 m. In that range of spans length it is noticed that 85% of bridges being built belong to the composite category (Fig. 4).The statistical analysis of the deck cost per square metre of surface confirms that the average price for a composite bridge is less than the price for a concrete bridge for spans length within intervals of 40 to 60 m and 60 to 80 m. The difference being of 1 500 FF/m2 over a total cost of 8 200 FF/m2 (VAT excluded) in favour of the composite bridge. It means that an 18% cost difference represents a great shift in terms of competition.The last 15 years have seen a great simplification of composite bridges for both roadway and railway bridges, which have made them, as previously indicated, very competitive compared to prestressed and reinforced bridges. These composite bridges, that we will name them as classical, have however several features which are described hereafter. Then, from these classical features, improvements have been constantly brought to the design and execution of composite bridges, which will be depicted later on.The traditional composite roadway bridge is composed of two longitudinal girders which are connected to the concrete slab by shear connectors (usually welded stud are mostly met; however steel angle connectors are still used). A limited number of transverse cross beams joining the two longitudinal girders, usually not connected to the slab — see half cross section (a) are welded to the vertical stiffeners. The main girders have a few numbers of horizontal stiffeners, if any which are mostly needed to resist the stress state in the girder webs occurring at the launching phase.Plain concrete is formed form a hardened mixture of cement, water, fine aggregate, coarse aggregate (crushed stone or gravel), air, and often other admixtures. The plastic mix is placed and consolidated in the formwork, then cured to facilitate the acceleration of the chemical hydration reaction of the cement/water mix, resulting in hardened concrete. The finished product has high compressive strength, and low resistance to tension, such that its tensile strength is approximately one-tenth of its compressive strength. Consequently, tensile and shear reinforcement in the tensile regions of sections has to be provided to compensate for the weak-tension regions in the reinforced concrete element.It is this deviation in the composition of a reinforced concrete section from thehomogeneity of standard wood or steel sections that requires a modified approach to the basic principles of structural design. The two components f the heterogeneous reinforced concrete section are to be so arranged and proportioned that optimal use is made of the materials involved. That is possible because concrete can easily be given any desired shape by placing and compacting the wet mixture of the constituent ingredients into suitable forms in which the plastic mass hardens. If the various ingredients are properly proportioned, the finished product becomes strong, durable, and, in combination with the reinforcing bars, adaptable for use as main members of any structural system.The techniques necessary for placing concrete depend on the type of member to be cast: that is, whether it is a column, a beam, a wall, a slab, a foundation, amass concrete dam, or an extension of previously placed and hardened concrete. For beams, columns, and walls, the forms should be well oiled after cleaning them, and the reinforcement earth should be compacted and thoroughly moistened to about 6 in. in depth to avoid absorption of the moisture present in the wet concrete. Concrete should always be placed in horizontal layers which are compacted by means of high-prequency power-driven vibrators of either the immersion or external type, as the case requires, unless it is placed by pumping. It must be kept in mind, however, that over vibration can be harmful since it could cause segregation of the aggregate and bleeding of the concrete.Hydration of the cement takes place in the presence of moisture at temperatures above F50. It is necessary to maintain such a condition in order that the chemical hydration reaction can take place. If drying is too rapid, surface cracking takes place. This would result in reduction of concrete strength due to cracking as well as the failure to attain full chemical hydration.It is clear that a large number of parameters have to be dealt with in proportioning a reinforced concrete element, such as geometrical width, depth, area of reinforcement, steel strain, concrete strain, steel strees, and so on. Consequently, trial and adjustment is necessary in the choice of concrete sections, with assumptionsbased on conditions at site, availability of the constituent materials, particular demands of the owners, architectural and headroom requirements, the applicable codes, and environmental conditions. Such an array of parameters has to be considered because of the fact that reinforced concrete is often a site-constructed composite, in contrast to the standard mill-fabricate beam and column sections in steel structures.A trial section has to be chosen for each critical location in a structural system. The trial section has to be analyzed to determine if its nominal resisting strength is adequate to carry the applied factored load. Since more than one trial is often necessary to arrive at the required section, the first design input step generates into a series of trial-and-adjustment analyses.The trial-and-adjustment procedures for the choice of a concrete section lead to the convergence of analysis and design. Hence every design is an analysis once a trial section is chosen. The availability of approach as a more efficient, compact, and speedy instructional method compared with the traditional approach of treating the analysis of reinforced concrete separately from pure design.The rapid growth from 1945 onwards in the prestressing of concrete shows that there was a real need for this high-quality material. The quality must be high because the worst conditions of loading normally occur at the beginning of the life of the member, at the transfer of stress later, when the concrete has become stronger and the stress in the steel has decreased because of creep in the steel and the concrete, and shrinkage of the concrete. Faulty members are therefore observed and thrown out early, before they enter the structure, or at least before it becomes inconvenient and expensive to remove them.The main advantages of prestressed concrete in comparison with reinforced concrete are:(a) The whole concrete cross-section resists load. In reinforced concrete about half the section, the cracked area below the neutral axis, does no useful work. Working deflections are smaller.(b) High working stresses are possible. In reinforced concrete they are notusually possible because hey result in severe cracking which is always ugly and may be dangerous if it causes rusting of the steel.(c) Cracking is almost completely avoided in prestressed concrete.The main disadvantage of prestressed concrete is that much more care is needed to make it than reinforced concrete and it is therefore more expensive, but because it is of higher quality less of it needs to be used.It can therefore happen that a solution of a structural problem may be cheaper in prestressed concrete than in reinforced concrete, and it does often happen that a solution is possible with prestressing but impossible without it.Prestressing of the concrete means that it is placed under compression before it carries any working load. This means that the section can be designed so that it takes no tension or very little under the full design load. It therefore has theoretically no cracks and in practice the concrete in which it is embedded has hardened. After the concrete has hardened enough to take the stress from the steel, some of the stress is transferred from the steel to the concrete. In a bridge with abutments able to resist thrust, the prestress can be applied without steel in the concrete. It is applied by jacks forcing the bridge inwards from the abutments. This method has the advantage that the jacking force, or prestress, can be varied during the life of the structure as required.In the ten years from 1950 to 1960 prestressed concrete ceased to be an experimental material and engineers won confidence in its use. With this confidence came an increase in the use of precast prestressed concrete particularly for long-span floors or the decks of motorways. Wherever the 500 m long, provided that most of the spans could be made the same and not much longer than 18 m, it became economical to use factory-precast prestressed beams, at least in industrial areas near a precasting factory. Most of these beams are heat-cured so as to free the forms quickly or reuse.In this period also, in the United States, precast prestressed roof beams and floor beams were used in many school buildings, occasionally 32 m long or more. Such long beams over a single span could not possibly be successful in reinforced concrete unless they were cast on site because they would have to be much deeper and muchheavier than prestressed concrete beams. They would certainly be less pleasing to the eye and often more expensive than the prestressed concrete beams. These school buidings have a strong, simple architectural appeal and will be a pleasure to look at for many years.The most important parts of a precast prestressed concrete beam are the tendons and the concrete. The tendons, as the name implies, are the cables, rods or wires of steel which are under tension in the concrete. Before the concrete has hardened (before transfer of stress), the tendons are either unstressed (post-tensioned prestressing) or are stressed and held by abutments outside the concrete (pre-tensioned prestressing). While the concrete is hardening it grips each tendon more and more tightly by bond along its full length. End anchorages consisting of plates or blocks are placed on the ends of the tendons of post-tensioned prestressed units, and such tendons are stressed up at the time of transfer, when the concrete has hardened sufficiently. In the other type of presstressing, with pre-tensioned tondons, the tendons are released from external abutments at the moment of transfer, and act on the concrete through bond or anchorage or both, shortening it by compression, and themselves also shortening and losing some tension.Further shortening of the concrete (and therefore of the steel) takes place with time. The concrete is said to creep. This means that it shortens permanently under load and spreads the stresses more uniformly and thus more safely across its section. Steel also creeps, but rather less. The result of these two effects (and of the concrete shrinking when it dries) is that prestressed concrete beams are never more highly stressed than at the moment of transfer.The factory precasting of long prestressed concrete beams is likely to become more and more popular in the future, but one difficulty will be road transport. As the length of the beam increases, the lorry becomes less and less manoeuvrable until eventually the only suitable time for it to travel is in the middle of the night when traffic is at a minimum. The limit of length for road transport varies tith the traffic in the district and the route, whether the roads are straight or curved. Precasting at the site avoids these difficulties; it may be expensive, but it has often been used for largebridge beams.Materials for building must have certain physical properties to be structurally useful. Primarily, they must be able to carry a load, or weight, without changing shape per- manently. When a load is applied to a structure member, it will deform; that is, a wire will stretch or a beam will bend. However, when the load is removed, the wire and the beam come back to the original positions. This material property is called elasticity. If a material were not elastic and a deformation were present in the structure after removal of the load, repeated loading and unloading eventually would increase the deformation to the point where the structure would become useless .All materials used in architect- tural structures, such as stone and brick, wood, steel, aluminum, reinforced concrete, and plastics, behave elastically within a certain defined range of loading. If the loading is increased above the range, two types of behavior can occur: brittle and plastic. In the former, the material will break suddenly. In the latter, the material begins to flow at a certain load (yield strength), ultimately leading to fracture. As examples, steel exhibits plastic behavior, and stone is brittle. The ultimate strength of a material is measured by the stress at which failure (fracture) occurs.A second important property of a building material is its stiffness. This property is defined by the elastic modulus, which is the ratio of the stress (force per unit area), to the strain (deformation per unit length). The elastic modulus, therefore, is a measure of the resistance of a material to deformation under load. For two materials of equal area under the same load, the one with the higher elastic modulus has the smaller deforma- tion. Structural steel, which has an elastic modulus of 30 million pounds per square in- ch (psi), or 2 100 000 kilograms per square centimeter, is 3 time as stiff as aluminum, 10 times as stiff as concrete, and 15 times as stiff as wood.Masonry consists of natural materials, such as stone, or manufactured products, such as brick and concrete blocks. Masonry has been used since ancient times; mud bricks were used in the city of Babylon for secular buildings, and stone was used for the great temples of the Nile Valley. The Great Pyramid in Egypt, standing 481 feet (147 meters) high, is the most spectacular masonry construction. Masonry units origin- nally were stacked without using any bonding agent, but all modern masonryconstruc- tion uses a cement mortar as a bonding material. Modern structural materials include stone, brick of burnt clay or slate, and concrete blocks.Masonry is essentially a compressive material; it cannot withstand a tensile force, that is, a pull. The ultimate compressive strength of bonded masonry depends on the strength of the masonry unit and the mortar. The ultimate strength will vary from 1 000 to 4 000 psi (70 to 280 kg/sq cm), depending on the particular combination of masonry unit and mortar used.Timber is one of the earliest construction materials and one of the few natural ma- terials with good tensile properties. Hundreds of different species of wood are found throughout the world, and each species exhibits different physical characteristics. Only a few species are used structurally as framing members in building construction. In the United States, for instance, out of more than 600 species of wood, only 20 species are used structurally. These are generally the conifers, or softwoods, both because of their abundance and because of the ease with which their wood can be shaped. The species of timber more commonly used in the United States for construction are Douglas fir, Southern pine, sqruce, and redwood. The ultimate tensile strength of these species varies from 5 000 to 8 000 psi (350 to 560 kg/sq cm). Hardwoods are used primarily for cabinetwork and for interior finishes such as floors.Because of the cellular nature of wood, it is stronger along the grain than across the grain. Wood is particularly strong in tension and compression parallel to the grain. And it has great bending strength. These properties make it ideally suited for columns and beams in structures. Wood is not effectively used as a tensile member in a truss, however, because the tensile strength of a truss member depends upon connections between members. It is difficult to devise connections which do not depend on the shear or tearing strength along the grain, although numerous metal connectors have been produced to utilize the tensile strength of timbers.Steel is an outstanding structural material. It has a high strength on a pound-for- pound basis when compared to other materials, even though its volume-for-volume weight is more than ten times that of wood. It has a high elastic modulus, which results in small deformations under load. It can be formed by rolling into variousstructural shapes such as I-beams, plates, and sheets; it also can be cast into complex shapes; and it is also produced in the form of wire strands and ropes for use as cables in suspension bridges and suspended roofs, as elevator ropes, and as wires for prestressing concrete. Steel elements can be joined together by various means, such as bolting, riveting, or welding. Carbon steels are subject to corrosion through oxidation and must be protected from contact with the atmosphere by painting them or embedding them in concrete. Above temperatures of about 700F (3710C), steel rapidly loses its strength, and there- fore it must be covered in a jacket of a fireproof material (usually concrete) to increase its fire resistance.The addition of alloying elements, such as silicon or manganese, results in higher strength steels with tensile strengths up to 250 000 psi (17 500 kg/sq cm). These steels are used where the size of a structural member becomes critical, as in the case of co- lumns in a skyscraper.Aluminum is especially useful as a building material when lightweight, strength, and corrosion resistance are all important factors. Because pure aluminum is extremely soft and ductile, alloying elements, such as magnesium, silicon, zinc, and copper, must be added to it to impart the strength required for structural use. Structural aluminum alloys behave elastically. They have an elastic modulus one third as great as steel and therefore deform three times as much as steel under the same load. The unit weight of an aluminum alloy is one third that of steel, and therefore an aluminum member will be lighter than a steel member of comparable strength. The ultimate tensile strength of aluminum alloys ranges from 20 000 to 60 000 psi (1 400 to 4 200 kg/sq cm).Aluminum can be formed into a variety of shapes; it can be extruded to form I- beams, drawn to form wire and rods, and rolled to form foil and plates. Aluminum members can be put together in the same way as steel by riveting, bolting, and (to a lesser extent) by welding. Apart from its use for framing members in buildings and prefabricated housing, aluminum also finds extensive use for window frames and for the skin of the building in curtain-wall construction.Concrete is a mixture of water, sand and gravel, and portland cement. Crushed。

毕业设计外文资料翻译原文题目：Bridge research in Europe译文题目：欧洲桥梁研究欧洲桥梁研究在欧洲，一个共同研究的平台随着欧盟的发展诞生了。

为了举例说明欧洲的研究方法已经被这种方式所替代，一个典型的案例就是有关英国后张法桥梁被讨论的事，爱丁堡大学给出了这个关于用数字化脉冲雷达鉴定后张法混凝土桥梁孔隙的资源互补的案例。

引言利用各研究团体的研究成果去验证大量相关论据是所有研究领域所面临的挑战，这是为了能使研究和实践更好地结合，具有针对性。

此外，在欧洲，不容忽视的语言壁垒也是一个巨大的障碍,为了避免再次爆发类似于从1939年至1945的第二次世界大战似的的欧洲内战，欧洲国家有了一个共同的政治目的，成立于20世纪60年代的欧共体便是基于这一目的。

它的成立带有很强的政治动机，但英国并非这一组织的成员，因为很多的欧洲国家视英国的利益为单纯的经济利益，直到70年代，英国才加入由欧共体转化而来的欧洲经济共同体。

到90年代，欧洲经济共同体扩展为欧洲国家联盟，而此时的欧盟既有共同的政治目标又有建立欧洲共同的货币体系的经济目标。

随着经济和政治的发展，土木工程，尤其是桥梁工程至今没能形成某种统一阵线。

这缘于英国和其他的欧洲国家迥异的大学教育培养体制，欧洲基金计划如苏格拉底计划、大不列颠（英国）欧洲计划等等。

对改变这种局面发挥了独特的作用，苏格拉底计划是以各成员国内互派学生学习为基础，而英国欧洲计划主要是给予一些国家的学术机构和工业伙伴以科研援助；它通常是由一个工业国家牵头。

关于知识的传播，目前似乎已出现了2种非常不同的方式、英美主要集中于在相关期刊出版物上发表首要的研究成果，例如ASCE、LCE及其它期刊，而欧洲内陆国家主要集中于在专门会议上展示其重要的研究成果，后者存在着局限性，新的研究成果的发布受到了限制。

另外，语言也是难以逾越的障碍，那些以英语作为强势外语的欧洲内陆国家积极参与各种国际会议，如德国、意大利、比利时、以及荷兰和瑞士。

桥梁工程中英文对照外文翻译文献(文档含英文原文和中文翻译)BRIDGE ENGINEERING AND AESTHETICSEvolvement of bridge Engineering,brief reviewAmong the early documented reviews of construction materials and structu re types are the books of Marcus Vitruvios Pollio in the first century B.C.The basic principles of statics were developed by the Greeks , and were exemplifi ed in works and applications by Leonardo da Vinci,Cardeno,and Galileo.In the fifteenth and sixteenth century, engineers seemed to be unaware of this record , and relied solely on experience and tradition for building bridges and aqueduc ts .The state of the art changed rapidly toward the end of the seventeenth cent ury when Leibnitz, Newton, and Bernoulli introduced mathematical formulatio ns. Published works by Lahire (1695)and Belidor (1792) about the theoretical a nalysis of structures provided the basis in the field of mechanics of materials .Kuzmanovic(1977) focuses on stone and wood as the first bridge-building materials. Iron was introduced during the transitional period from wood to steel .According to recent records , concrete was used in France as early as 1840 for a bridge 39 feet (12 m) long to span the Garoyne Canal at Grisoles, but r einforced concrete was not introduced in bridge construction until the beginnin g of this century . Prestressed concrete was first used in 1927.Stone bridges of the arch type (integrated superstructure and substructure) were constructed in Rome and other European cities in the middle ages . Thes e arches were half-circular , with flat arches beginning to dominate bridge wor k during the Renaissance period. This concept was markedly improved at the e nd of the eighteenth century and found structurally adequate to accommodate f uture railroad loads . In terms of analysis and use of materials , stone bridges have not changed much ,but the theoretical treatment was improved by introd ucing the pressure-line concept in the early 1670s(Lahire, 1695) . The arch the ory was documented in model tests where typical failure modes were considered (Frezier,1739).Culmann(1851) introduced the elastic center method for fixed-e nd arches, and showed that three redundant parameters can be found by the us e of three equations of coMPatibility.Wooden trusses were used in bridges during the sixteenth century when P alladio built triangular frames for bridge spans 10 feet long . This effort also f ocused on the three basic principles og bridge design : convenience(serviceabili ty) ,appearance , and endurance(strength) . several timber truss bridges were co nstructed in western Europe beginning in the 1750s with spans up to 200 feet (61m) supported on stone substructures .Significant progress was possible in t he United States and Russia during the nineteenth century ,prompted by the ne ed to cross major rivers and by an abundance of suitable timber . Favorable e conomic considerations included initial low cost and fast construction .The transition from wooden bridges to steel types probably did not begin until about 1840 ,although the first documented use of iron in bridges was the chain bridge built in 1734 across the Oder River in Prussia . The first truss completely made of iron was in 1840 in the United States , followed by Eng land in 1845 , Germany in 1853 , and Russia in 1857 . In 1840 , the first ir on arch truss bridge was built across the Erie Canal at Utica .The Impetus of AnalysisThe theory of structures ,developed mainly in the ninetheenth century,foc used on truss analysis, with the first book on bridges written in 1811. The Wa rren triangular truss was introduced in 1846 , supplemented by a method for c alculating the correcet forces .I-beams fabricated from plates became popular in England and were used in short-span bridges.In 1866, Culmann explained the principles of cantilever truss bridges, an d one year later the first cantilever bridge was built across the Main River in Hassfurt, Germany, with a center span of 425 feet (130m) . The first cantileve r bridge in the United States was built in 1875 across the Kentucky River.A most impressive railway cantilever bridge in the nineteenth century was the Fir st of Forth bridge , built between 1883 and 1893 , with span magnitudes of 1711 feet (521.5m).At about the same time , structural steel was introduced as a prime mater ial in bridge work , although its quality was often poor . Several early exampl es are the Eads bridge in St.Louis ; the Brooklyn bridge in New York ; and t he Glasgow bridge in Missouri , all completed between 1874 and 1883.Among the analytical and design progress to be mentioned are the contrib utions of Maxwell , particularly for certain statically indeterminate trusses ; the books by Cremona (1872) on graphical statics; the force method redefined by Mohr; and the works by Clapeyron who introduced the three-moment equation s.The Impetus of New MaterialsSince the beginning of the twentieth century , concrete has taken its place as one of the most useful and important structural materials . Because of the coMParative ease with which it can be molded into any desired shape , its st ructural uses are almost unlimited . Wherever Portland cement and suitable agg regates are available , it can replace other materials for certain types of structu res, such as bridge substructure and foundation elements .In addition , the introduction of reinforced concrete in multispan frames at the beginning of this century imposed new analytical requirements . Structures of a high order of redundancy could not be analyzed with the classical metho ds of the nineteenth century .The importance of joint rotation was already dem onstrated by Manderla (1880) and Bendixen (1914) , who developed relationshi ps between joint moments and angular rotations from which the unknown mom ents can be obtained ,the so called slope-deflection method .More simplification s in frame analysis were made possible by the work of Calisev (1923) , who used successive approximations to reduce the system of equations to one simpl e expression for each iteration step . This approach was further refined and int egrated by Cross (1930) in what is known as the method of moment distributi on .One of the most import important recent developments in the area of analytical procedures is the extension of design to cover the elastic-plastic range , also known as load factor or ultimate design. Plastic analysis was introduced with some practical observations by Tresca (1846) ; and was formulated by Sa int-Venant (1870) , The concept of plasticity attracted researchers and engineers after World War Ⅰ, mainly in Germany , with the center of activity shifting to England and the United States after World War Ⅱ.The probabilistic approa ch is a new design concept that is expected to replace the classical determinist ic methodology.A main step forward was the 1969 addition of the Federal Highway Adim inistration (F HWA)”Criteria for Reinforced Concrete Bridge Members “ that co vers strength and serviceability at ultimate design . This was prepared for use in conjunction with the 1969 American Association of State Highway Offficials (AASHO) Standard Specification, and was presented in a format that is readil y adaptable to the development of ultimate design specifications .According to this document , the proportioning of reinforced concrete members ( including c olumns ) may be limited by various stages of behavior : elastic , cracked , an d ultimate . Design axial loads , or design shears . Structural capacity is the r eaction phase , and all calculated modified strength values derived from theoret ical strengths are the capacity values , such as moment capacity ,axial load ca pacity ,or shear capacity .At serviceability states , investigations may also be n ecessary for deflections , maximum crack width , and fatigue .Bridge TypesA notable bridge type is the suspension bridge , with the first example bu ilt in the United States in 1796. Problems of dynamic stability were investigate d after the Tacoma bridge collapse , and this work led to significant theoretica l contributions Steinman ( 1929 ) summarizes about 250 suspension bridges bu ilt throughout the world between 1741 and 1928 .With the introduction of the interstate system and the need to provide stru ctures at grade separations , certain bridge types have taken a strong place in bridge practice. These include concrete superstructures (slab ,T-beams,concrete box girders ), steel beam and plate girders , steel box girders , composite const ruction , orthotropic plates , segmental construction , curved girders ,and cable-stayed bridges . Prefabricated members are given serious consideration , while interest in box sections remains strong .Bridge Appearance and AestheticsGrimm ( 1975 ) documents the first recorded legislative effort to control t he appearance of the built environment . This occurred in 1647 when the Cou ncil of New Amsterdam appointed three officials . In 1954 , the Supreme Cou rt of the United States held that it is within the power of the legislature to de termine that communities should be attractive as well as healthy , spacious as well as clean , and balanced as well as patrolled . The Environmental Policy Act of 1969 directs all agencies of the federal government to identify and dev elop methods and procedures to ensure that presently unquantified environmenta l amentities and values are given appropriate consideration in decision making along with economic and technical aspects .Although in many civil engineering works aesthetics has been practiced al most intuitively , particularly in the past , bridge engineers have not ignored o r neglected the aesthetic disciplines .Recent research on the subject appears to lead to a rationalized aesthetic design methodology (Grimm and Preiser , 1976 ) .Work has been done on the aesthetics of color ,light ,texture , shape , and proportions , as well as other perceptual modalities , and this direction is bot h theoretically and empirically oriented .Aesthetic control mechanisms are commonly integrated into the land-use re gulations and design standards . In addition to concern for aesthetics at the sta te level , federal concern focuses also on the effects of man-constructed enviro nment on human life , with guidelines and criteria directed toward improving quality and appearance in the design process . Good potential for the upgradin g of aesthetic quality in bridge superstructures and substructures can be seen in the evaluation structure types aimed at improving overall appearance .Lords and lording groupsThe loads to be considered in the design of substructures and bridge foun dations include loads and forces transmitted from the superstructure, and those acting directly on the substructure and foundation .AASHTO loads . Section 3 of AASHTO specifications summarizes the loa ds and forces to be considered in the design of bridges (superstructure and sub structure ) . Briefly , these are dead load ,live load , iMPact or dynamic effec t of live load , wind load , and other forces such as longitudinal forces , cent rifugal force ,thermal forces , earth pressure , buoyancy , shrinkage and long t erm creep , rib shortening , erection stresses , ice and current pressure , collisi on force , and earthquake stresses .Besides these conventional loads that are ge nerally quantified , AASHTO also recognizes indirect load effects such as fricti on at expansion bearings and stresses associated with differential settlement of bridge components .The LRFD specifications divide loads into two distinct cate gories : permanent and transient .Permanent loadsDead Load : this includes the weight DC of all bridge components , appu rtenances and utilities, wearing surface DW nd future overlays , and earth fill EV. Both AASHTO and LRFD specifications give tables summarizing the unit weights of materials commonly used in bridge work .Transient LoadsVehicular Live Load (LL) Vehicle loading for short-span bridges :considera ble effort has been made in the United States and Canada to develop a live lo ad model that can represent the highway loading more realistically than the H or the HS AASHTO models . The current AASHTO model is still the applica ble loading.桥梁工程和桥梁美学桥梁工程的发展概况早在公元前1世纪，Marcus Vitrucios Pollio 的著作中就有关于建筑材料和结构类型的记载和评述。

AUTOMATIC DEFLECTION AND TEMPERATURE MONITORING OFA BALANCED CANTILEVER CONCRETE BRIDGEby Olivier BURDET， Ph。

D.Swiss Federal Institute of Technology， Lausanne, SwitzerlandInstitute of Reinforced and Prestressed Concrete SUMMARYThere is a need for reliable monitoring systems to follow the evolution of the behavior of structures over time。

Deflections and rotations are values that reflect the overall structure behavior. This paper presents an innovative approach to the measurement of long-term deformations of bridges by use of inclinometers。

High precision electronic inclinometers can be used to follow effectively long—term rotations without disruption of the traffic. In addition to their accuracy，these instruments have proven to be sufficiently stable over time and reliable for field conditions。

The Mentue bridges are twin 565 m long box-girder post—tensioned concrete highway bridges under construction in Switzerland. The bridges are built by the balanced cantilever method over a deep valley. The piers are 100 m high and the main span is 150 m。