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【推荐】道路桥梁专业书籍汇总有需要这些书的网友可以去这个网站下载!!~桥梁专业书籍集PDF（不断更新中）1《公路钢筋混凝土及预应力混凝土桥涵设计规范》（JTG D62-2004）条文应用算例2 桥梁工程（土木工程、交通工程专业用）3 大跨度桥梁结构计算理论4 桥梁风工程5 组合结构桥梁6 公路桥梁荷载横向分布计算(李国豪石洞)7 公路桥梁荷载横向分布计算方法(贺拴海谢仁物)8 现代悬索桥9 大跨度桥梁施工控制10 缆索支承桥梁：概念与设计_[丹麦]吉姆辛--金增洪译11 悬索桥手册12 高等桥梁结构理论13 斜拉桥理论与设计14 桥梁转体施工15 桥梁专业辞典16 斜拉桥手册17 桥梁工程检测手册18 桥梁结构空间分析设计方法与应用-戴公连李建连19 公路旧桥加固技术与实例20 桥梁加固设计与施工技术21 桥梁结构轻型化与造型艺术22 桥梁抗震设计理论及应用丛书之一_大跨度桥梁抗震设计_范立础23 桥梁抗震设计理论及应用丛书之二_桥梁减隔震设计_范立础24 大跨悬索桥的设计与施工25 桥梁工程概论26 桥梁工程(桥梁工程专业用)(第二版)_范立础27 桥梁通用构造及简支梁桥28 桥梁简化分析29 桥梁计算示例集混凝土简支梁（板）桥30 公路桥梁荷载试验与结构评定31 钢管混凝土拱桥实例集（一）32 桥梁与结构理论研究_李国豪33 润扬长江公路大桥建设第四册－斜拉桥34 造桥三十六年_邓文中35桥梁方案比选36钢筋混凝土桁架拱桥（第二版）道路专业书籍集PDF（不断更新中）1 高等级公路控制测量2 高等级公路沥青混凝土路面新技术3 公路挡土墙设计4 公路路基施工技术5 路面设计原理与方法6 真空排水预压法加固软土技术7 道路立体交叉规划与设计8 高速公路9 现代道路交通测试技术：原理与应用10 高速公路沥青路面早期破坏现象及预防11 高速公路立交工程12 高速公路路基路面施工工艺13 高速公路路面设计与施工14 公路排水设计手册15 公路设计指南16 公路养护工程17 国外沥青路面设计方法总汇18 沥青路面道路质量评估及养护指南19 沥青路面施工与养护技术20 路基工程现场施工技术21 路基路面工程—邓学钧22 复合式路面设计原理与施工技术23 改性沥青与SMA路面24 高等级公路施工技术与管理25 振动压路机与振动压实技术26 公路工程施工常见地质病害处治技术27 公路水泥混凝土路面典型结构设计方法28 公路与城市道路设计手册。
Unit 23 The Bridge Testing Technology桥梁测试技术内容概要本文以一座斜拉桥为例介绍了在瑞士进行荷载动力试验的一般步骤和获得的结果。
介绍了动力试验的主要目的以及结构的主要动力指标。
阐述了在试验中如何对桥梁进行激励以使其产生振动。
同时将试验获得的结果以图形的形式表示出来。
讨论了桥面受到破坏对动力性能的影响，并将动力试验与静力试验的结果进行了比较。
A. Text Dynamic Load Testing of A Cable-Stayed BridgesThe article presents results obtained using a simple dynamic testing procedure frequently used in Switzerland for highway bridges. Typical results are shown and tendencies observed in the dynamic behavior of highway bridges are presented. For a deteriorated pavement, the dynamic impact of heavy vehicles is shown to be larger at lower truck speeds. Some correlation is shown between the dynamic properties of the bridge and its stiffness, as measured in a static load test.1. IntroductionDynamic load testing is an important part of the acceptance process for new bridges in Switzerland. As a complement to static load tests, dynamic tests yield useful information about the actual behavior of the bridge under traffic. This information is usually difficult to obtain analytically, because of the complexity of the actual structure. The effect of pavement deterioration on the dynamic response of the bridge is of particular importance for the management of the structure. This information can be easily and realistically obtained from a dynamic test, and thereafter used by the highway authorities to organize the pavement maintenance.Drawing on the large number of tests performed by IBAP over the past twenty years, the paper describes the general dynamic characteristics of highway bridges. Some correlation is shown between the stiffness obtained in a static load test and the measured eigenfrequencies. The influence of the speed of a vehicle crossing the bridge is discussed. In particular, the effect of an artificial damage in the pavement on the dynamic behavior is presented.2. Dynamic Load TestingThe purpose of the dynamic load test is to determine the controlling parameters of the dynamic behavior of the bridges. The main dynamic characteristics of the structure are the fundamental vibration frequency, the dynamic amplification factor and the logarithmic decrement. These properties are usually not analyzed in detail in the design phase of small and middle sized structures. Some parameters, such as the logarithmic decrement or the dynamic amplification factor, can only be roughly estimated at the time of the design. However, these quantities are relatively easy to obtain experimentally, and can give valuable information for the exploitation and maintenance of the bridge.The general methodology used in the dynamic load test of a bridge will be presented using as an example the bridge shown in Fig.23-1. The Riddes-Leytron bridge is a cable-stayed structure with a slender deck, supporting two lanes of traffic and a sidewalk. The bridge was built fromFig. 23-2: Description of the dynamic load testa) Relative vertical deflection at mid-span caused by the passage of the truckb) Dynamic influence line of the passage of the truck. Determination of the dynamic amplification factor.1991 to 1992 and tested in the summer of 1992.3. MethodologyDynamic load testing is performed by exciting the vibration of the bridge and by measuring its properties after the excitation has ceased. Several methods are available for the excitation of the bridge, in particular: eccentric rotating masses, impact of a heavy weight and passage of a loaded truck. This last method is often preferred for the dynamic load testing of bridges because it gives, along with reasonably accurate values of the above mentioned quantities, a good approximation of the effect of the actual traffic on the structure. By varying the speed of the truck on the bridge, the full range of traffic speeds can be investigated. Furthermore, this method is easily implemented while some of the other ones necessitate more complicated installation procedures. The measurements are taken and recorded by a dynamic data acquisition system with integrated Fast-Fourier Transform (FFT) analyzer, allowing an immediate interpretation of the results during the test.The trucks used for the dynamic excitation of the bridge are usually 3-axle trucks, with a total weight of 250 kN (total mass of 25 metric tons), traveling on the bridge at several speeds. The effect of a deterioration of the pavement is simulated by the introduction of a normalized plank on the path of the truck. This induces a strong impact when the trucks passes at mid-span, that represents the effect of a pothole in the pavement, or the irregularity of the surface caused by packed snow. Fig. 23-2 shows the location of the instruments and the results for the dynamic testing of the Riddes-Leytron bridge. Absolute displacement sensors are used for the measurements, and therefore only components with a relatively high frequency (larger than 0.2 Hz) are recorded, as shown in Fig. 23-2a (vertical dispacement at mid-span as a function of the truck position). The static influence line of the truck passing on the bridge is then added to obtain the Fig. 23-1: Geometry of the Riddes-Leytron bridgecomplete dynamic influence line shown in Fig. 23-2b.4. ResultsBecause a lot of information is gathered in the course of dynamic load testing, the results are usually presented graphically. First, as shown in figure 3b, the dynamic influence line of the bridge subjected to the passage of a truck is drawn for all travel speeds, with and without plank. This allows a simple visual determination of the dynamic amplification factor F. The natural frequency of the bridge is obtained from acceleration spectra performed by the FFT analyzer. The logarithmic decrement is obtained from the decay of the bridge free oscillations, after the truck has left the bridge, or at least when it is far enough from the instruments (Fig. 23-2a).Fig. 23-3 shows the maximum measured vertical acceleration and displacement induced at mid-span of the Riddes-Leytron bridge by a passing truck, as a function of the truck speed. In the case of smooth riding surface, the response of the bridge is small and increases with increasing speed, while in the case of a deteriorated surface, the response is strong and the influence of the truck speed is less clear. It has been observed in other structures that lower truck speeds can induce larger displacements (and accelerations) than higher speeds. One possible explanation is that a truck traveling at a lower speed will cause two distinct shocks as its two rear axles successively hit the plank. At low truck speeds, the two shocks occur approximately one second apart, which is close to the natural period of most bridges. At higher speeds, the two shocks are very close to one another, and remote from the natural frequency of the bridge.Human beings are especially sensitive to vibrations, particularly to accelerations. Some codes give limiting values of acceleration as a function of the fundamental frequency. In practice, these limits are never reached if the riding surface is smooth, but they can be exceeded in the case of a deteriorated pavement. The results of the dynamic load tests give therefore useful information on the sensitivity of the bridge to deterioration, and can be used in defining the maintenance program for the pavement.5. Comparison with the Results of Static Load TestingBecause dynamic loading testing is usually performed on bridges that have also been subjected to static load testing, comparisons can be made between the behavior of a bridge under static and dynamic loading. Clearly, the two behaviors are related, in that the bridge stiffness, or spring constant k appears in both the static load test and in the components of the natural frequency. As expected, there is on average an increase in natural frequency with an increase in stiffness. However, the scatter is rather large, especially for concrete bridges, as their mass strongly depends on the construction method and cross section. A similar scatter can be observedwhen looking at the correlation between the dynamic amplification factor and the bridge span or Fig. 23-3 Dynamic response of the bridge as a function of the truck speednatural frequency. While some tendencies can be observed, the scatter of the data makes the derivation of a simple approximate formula impractical.6. ConclusionsThe paper presents results obtained from simple dynamic load tests of bridges. These tests are frequently performed in Switzerland as part of the acceptance process of new bridges. The main results are the natural frequency of the bridge, the dynamic amplification factor and the logarithmic decrement.By using a truck to induce vibrations of the bridge, it is possible to simulate the effects of pavement deterioration. Bridges that are especially sensitive to pavement deterioration are identified, and this information can then be used in establishing of the maintenance program of the structure. Truck speed is shown as having a great importance on the dynamic response of the bridge, especially in the case of a deteriorated riding surface.Some correlation is shown between the span and the natural frequency of a bridge, but a considerable scatter is observed. In a similar manner, there is some correlation between the bridge stiffness observed in a static load test and the dynamic properties of the bridge.New Words and Expressionscable-stayed bridges 斜拉桥deteriorate vt.(使)恶化stiffness n.坚硬, 硬度eigenfrequency n.本征频率,特征频率amplification n.扩大logarithmic a.对数的parameter n.参数, 参量, <口>起限定作用的因素methodology n.方法学, 方法论sidewalk n.人行道cease vi.停止, 终了implement n.工具, 器具vt.贯彻, 实现v. 执行necessitate vt.成为必要3-axle truck 三轴汽车spectra n.范围, 光谱histogram n.柱状图distinct a.清楚的, 明显的, 截然不同的, 独特的scatter n.分散, 散开, 撒开, 驱散Notes1. The effect of pavement deterioration on the dynamic response of the bridge is of particular importance for the management of the structure. This information can be easily and realistically obtained from a dynamic test, and thereafter used by the highway authorities to organize the pavement maintenance.路面状况变坏对桥梁动力反应的影响在结构管理方面是十分重要的。
道路桥梁与渡河工程专业书籍When it comes to the discipline of road and bridge engineering, there are a multitude of specialized books and resources available for both students and professionals to deepen their knowledge and understanding in this field. From textbooks that cover the fundamental principles of bridge design to advanced research publications on innovative bridge construction techniques, the literature on road and bridge engineering is both comprehensive and diverse.谈到道路和桥梁工程学科，有许多专业书籍和资源供学生和专业人士深入了解和理解这一领域。
从涵盖桥梁设计基本原理的教科书到关于创新桥梁施工技术的高级研究出版物，道路和桥梁工程领域的文献既全面又多样。
For students studying civil engineering with a focus on road and bridge engineering, textbooks such as "Bridge Engineering: Design, Rehabilitation, and Maintenance of Modern Highway Bridges" by Demetrios E. Tonnar, provide a solid foundation in the core concepts and practices of bridge design and construction. These resources not only cover the theoretical aspects of bridge engineering but alsooffer practical examples and case studies to illustrate real-world applications of the principles discussed.对于学习土木工程专业并专注于道路和桥梁工程的学生来说，Demetrios E. Tonnar的《桥梁工程：现代公路桥梁的设计、修复和维护》等教科书为他们提供了扎实的桥梁设计和施工核心概念和实践基础。
第1篇一、前言随着我国经济的快速发展，道路桥梁建设已成为基础设施建设的重要组成部分。
为确保道路桥梁工程质量、安全和进度，特编制本手册，以指导道路桥梁工程施工。
二、施工准备1. 施工图纸审查：施工单位应认真审查施工图纸，确保图纸完整、准确，并熟悉图纸中的设计要求。
2. 材料设备准备：根据施工图纸和工程量清单，采购、加工所需材料设备，并确保其质量符合规范要求。
3. 施工现场布置：合理规划施工现场，设置施工区域、材料堆场、施工道路等，确保施工顺利进行。
4. 施工人员培训：对施工人员进行技术培训，提高其业务水平，确保施工质量。
5. 施工方案编制：根据施工图纸、工程量清单和现场实际情况，编制施工方案，明确施工工艺、施工顺序、质量控制措施等。
三、施工工艺1. 路基施工：包括土方开挖、填筑、压实等工序，确保路基平整、坚实。
2. 桥梁基础施工：包括桩基础、承台、墩身等施工，确保桥梁基础稳固。
3. 桥梁上部结构施工：包括梁体、桥面板、桥墩等施工，确保桥梁上部结构安全、可靠。
4. 路面施工：包括基层、面层施工，确保路面平整、坚实、耐磨。
5. 隧道施工：包括洞口施工、洞身开挖、支护、衬砌等工序，确保隧道施工安全、顺利。
四、质量控制1. 材料质量控制：严格按照规范要求，对进场材料进行检验，确保材料质量。
2. 施工过程控制：加强对施工过程的监督检查，确保施工工艺、施工顺序、质量控制措施得到落实。
3. 质量验收：按照规范要求，对施工完成部位进行验收，确保工程质量。
五、安全管理1. 施工现场安全：加强施工现场安全管理，严格执行安全操作规程，确保施工安全。
2. 人员安全：加强对施工人员的安全教育培训，提高安全意识。
3. 设备安全：定期对施工设备进行检查、维护，确保设备安全运行。
六、施工进度管理1. 制定施工进度计划：根据工程量、施工条件等因素，制定合理的施工进度计划。
2. 施工进度控制：加强施工进度管理，确保工程按期完成。
3. 施工协调：协调各部门、各施工队伍之间的工作，确保施工顺利进行。
15HorizontallyCurved Bridges15.1 Introduction15.2 Structural Analysis for Curved BridgesSimplified Method: V-Load15.3 Curved Steel I-Girder Bridges Geometric Parameters •Design Criteria •DesignExample 15.4 Curved Steel Box-Girder Bridges 15.5 Curved Concrete Box-Girder BridgesAs a result of complicated geometrics, limited rights of way, and traffic mitigation, horizontally curved bridges are becoming the norm of highway interchanges and urban expressways. This type of superstructure has gained popularity since the early 1960s because it addresses the needs of transportation engineering. Figure 15.1 shows the 20th Street HOV in Denver, Colorado. The structure is composed of curved I-girders that are interconnected to each other by cross frames and are bolted to the bent cap. Cross frames are bolted to the bottom flange while the concrete deck is supported on a permanent metal form deck as shown in Figure 15.2. Figure 15.3 shows the elevation of the bridge and the connection of the plate girders into an integral bent cap. Figure 15.4 shows the U.S. Naval Academy Bridge in Annapolis, Maryland which is a twin steel box-girder bridge that is haunched at the interior support. Figure 15.5 shows Ramp Y at I-95 Davies Blvd. Interchange in Broward County, Florida. The structure is a single steel box girder with an integral bent cap.Figure 15.6 shows a photo of Route 92/101 Interchange in San Mateo, California. The structure is composed of several cast-in-place curved P/S box-girder bridges.The American Association of Highway and Transportation Officials (AASHTO) governs the structural design of horizontally curved bridges through Guide Specifications for Horizontally Curved Highway Bridges [1]. This guide was developed by Consortium of University Research Teams (CURT) in 1976 [2] and was first published by AASHTO in 1980. In its first edition the guide specification included allowable stress design (ASD) provisions that was developed by CURT and load factor design (LFD) provisions that were developed by American Iron and Steel Institute under project 190 [15]. Several changes have been made to the guide specifications since 1981. In 1993 a new version of the guide specifications was released by AASHTO. However, these new specifications did not include the latest extensive research in this area nor the important changes that affected the design of straight I-girder steel bridges.Ahmad M. ItaniUniversity of Nevada at Reno Mark L. RenoCalifornia Department ofTransportationFIGURE 15.1Curved I-girder bridge under construction — 20th St. HOV, Denver, Colorado.FIGURE 15.2Bottom view of curved I-girder bridge.The guide specifications for horizontally curved bridges under Project 12-38 of the National Cooperative Highway Research Program (NCHRP) [3] have been modified to reflect the current state-of-the-art knowledge. The findings of this project are fully documented in NCHRP interim reports: “I Girder Curvature Study” and “Curved Girder Design and Construction, Current Practice”[3]. The new “Guide Specifications for Horizontally Curved Steel Girder Highway Bridges” [18]proposed by Hall and Yeo was adopted as AASHTO Guide specifications in May, 1999. In addition to these significant changes, the Federal Highway Administration (FHWA) sponsored extensive theoretical and experimental research programs on curved girder bridges. It is anticipated that these programs will further improve the current curved girder specifications. Currently, the NCHRP 12–50 is developing “LRFD Specifications for Horizontally Curved Steel Girder Bridges” [19].The guidelines of curved bridges are mainly geared toward structural steel bridges. Limited information can be found in the literature regarding the structural design of curved structural concrete (R/C and P/S) bridges. Curved structural concrete bridges have a box shape, which makes the torsional stiffness very high and thus reduces the effect of curvature on the structural design.The objective of this chapter is to present guidelines for the design of curved highway bridges.Structural design of steel I-girder, steel, and P/S box-girder bridges is the main thrust of this chapter.The accuracy of structural analysis depends on the analysis method selected. The main purpose of structural analysis is to determine the member actions due to applied loads. In order to achieve reliable structural analysis, the following items should be properly considered:•Mathematical model and boundary conditions•Application of loadsFIGURE 15.3Curved I-girder bridge with integral bent cap.FIGURE 15.4Twin box-girder bridge — U.S. Naval Academy Bridge, Annapolis, Maryland.FIGURE 15.5Single box girder bridge with integral bent cap — Ramp Y, I-95 Davies Blvd., Broward County, Florida.The mathematical model should reflect the structural stiffness properly. The deck of the super-structure should be modeled in such a way that is represented as a beam in a grid system or as a continuum. The boundary conditions in the mathematical model must be represented teral bearing restraint is one of the most important conditions in curved bridges because it affects the design of the superstructure. The deck overhang, which carries a rail, provides a significant torsion resistance. Moreover, the curved bottom flange would participate in resisting vertical load.This participation increases the applied stresses beyond those determined by using simple structural mechanics procedures [3].Due to geometric complexities, the gravity load will induce torsional shear stresses, warping normal stresses, and flexural stresses to the structural components of horizontally curved bridges.To determine these stresses, special analysis accounting for torsion is required. Various methods were developed for the analysis of horizontally curved bridges, which include simplified and refined analysis methods. The simplified methods such as the V-Load method [4] for I-girders and the M/R method for box girders are normally used with “regular” curved bridges. However, refined analysis will be required whenever the curved bridges include skews and lateral or rotational restraint. Most refined methods are forms of finite-element analysis. Grillage analysis as well as three-dimensional (3-D) models have been used successfully to analyze curved bridges. The grillage method assumes that the member can be represented in a series of beam elements. Loads are normally applied through a combination of vertical and torsion loads. The 3-D models that represent the actual depth of the superstructure will capture the torsion responses by combining the responses of several bridge elements.15.2.1Simplified Method: V-LoadIn 1984, AISC Marketing, Inc. published “V-Load Analysis” for curved steel bridges [4]. This report presented an approximate simplified analysis method to determine moments and shears for horizontally FIGURE 15.6Curved concrete box-girder bridges — Route 92/101 Interchange, San Mateo, California.curved open-framed highway bridges. This method is known as the V-Load method because a large part of the torsion load on the girders is approximated by sets of vertical shears known as “V-Loads.”The V-Load method is a two-step process. First, the bridge is straightened out so that the applied vertical load is assumed to induce only flexural stresses. Second, additional fictitious forces are applied to result in final stresses similar to the ones in a curved bridge. The additional fictitious forces are determined so that they result in no net vertical, longitudinal, or transverse forces on the bridge.Figure 15.7 shows two prismatic girders continuous over one interior support with two equal spans, L 1. Girder 1 has a radius of R and the distance between the girders is D . The cross frames are uniformly spaced at distance equal to d . As shown later, the cross frames in curved bridges are primary members since they are required to resist the radial forces applied on the girder due to bridge curvature.When the gravity load is applied, the flanges of the plate girder will be subjected to axial forces F = M/R, as shown in Figure 15.8. However, due to the curvature of the girder, laterally distributed load q will be applied to flanges of the plate girder in order to achieve equilibrium. By assuming that the flanges resist most of the bending moment, the longitudinal forces in the flanges at any point will be equal to the moment, M , divided by the section height, h . Due to the curvature of the bridge, these forces are not collinear along any given segment of the flange. Thus, radial forces must be developed along the girder in order to maintain equilibrium. The forces cause lateral bending FIGURE 15.7Plan view of two-span curved bridge.FIGURE 15.8Plan view of curved bridge top flange.of the girder flanges resulting in warping stresses. The magnitude of the radial forces is equal to M/hR and has the same shape of the bending moment diagram as shown in Figure 15.9.This distributed load creates equal and opposite reaction forces at every cross frame as shown in Figure 15.10. By assuming the spacing between the cross frames is equal to d , the reaction force at the cross frame is equal to H , which is equal to Md/hR .To maintain equilibrium of the cross frame forces, vertical shear forces must develop at the end of the cross frames as a result of cross frame rigidity and end fixity as shown in Figure 15.11.15.3.1Geometric ParametersAccording to the current AASHTO specifications [13], the effect of curvature may be neglected in determining the primary bending moment in longitudinal members when the central angle of each span in a two or more span bridge is less than 5° for five longitudinal girders. The framing system FIGURE 15.9Lateral forces on curved girder flange.FIGURE 15.10Reaction at cross frame location.for curved I-girder bridges may follow the preliminary design of straight bridges in terms of span arrangement, girder spacing, girder depth, and cross frame types. The choice of the exterior span length is normally set to give relatively equal positive dead-load moments in the exterior and interior spans. The arrangement results in the largest possible negative moment, which reduces both positive moments and related deflections. Normally, the depth of the superstructure is the same for all spans.Previous successful design showed a depth-to-span ratio equal to 25 for the exterior girder to be adequate. This ratio has been based on vibration and stiffness needed to construct the plate girders.Also, this ratio helps to ensure that the girders do not experience excessive vertical deflections. The uplift of the exterior girder should be prevented as much by extending the span length of the exterior girder rather than dealing with the use of tie-down devices.Girder spacing plays a significant role in the deck design and the determination of the number of girders. Wider spacing tends to increase the dead load on the girders, while closer spacing requires additional girders, which increases the fabrication and erections costs. For curved steel I-girder bridges, the girder spacing varies between 3.05 m (10 ft) and 4.87 m (16 ft). Wider spacing, common in Europe and Japan, requires a post-tensioned concrete deck, which is not common practice in the United States. The overhang length should not exceed 1.22 m (4 ft) because it tends to increase the load on the exterior girders by adding more dead load and permitting truckload to be applied on the cantilever. The flanges of the plate girder should have a minimum width to avoid out-of-plane buckling during construction. Many steel erectors limit the length of girder shipping pieces to 85 times the flange width [5]. Based on that, many bridge engineers tend to limit the width of the flange to 40.6 mm (16 in) based on a maximum shipping length equal to 36.6 m (120 ft). It is also recommended that the minimum web thickness be limited to 11.1 mm (⁷⁄₁₆ in) because of weld distortion problems. The thickness of the web depends on its depth and the spacing of the transverse stiffeners. This represents a trade-off between having extra material or adding more stiffeners. Many bridge engineers use the ratio of D/t =150 to choose the thickness of the web.The spacing of the cross frame plays an important factor in the amount of force carried out by it and the value of flange lateral bending. Normally, cross-frame spacing is held between 4.57 m (15 ft) and 7.62 m (25 ft).15.3.2Design CriteriaThe design guidelines, according to the Recommended Specifications for Steel Curved Girder Bridges [3], are established based on the following principles:•Statics•StabilityFIGURE 15.11Equilibrium at cross frame location and the formation of V-loads.•Strength of materials•Inelastic behaviorExternal and internal static equilibrium should be maintained under every expected loading condition. Stability of curved steel girder bridges is a very important issue especially during con-struction. By their nature, curved girders experience lateral deflection when subjected to gravity loading. Therefore, these girders should be braced at specified intervals to prevent lateral torsional buckling. The compactness ratio of the web and the flanges of curved I-girders are similar to the straight girders. The linear strain distribution is normally assumed in the design of curved girder bridges. The design specification recognizes that compact steel sections can undergo inelastic defor-mations; however, current U.S. practice does not utilize a compact steel section in the design of curved I-girder bridges.The design criteria for curved girder bridges can be divided into two main sections.•Strength•ServiceabilityLimit state design procedures are normally used for the strength design, which includes flexure and shear. Service load design procedures are used for fatigue design and deflection control. The primary members should be designed to be such that their applied stress ranges are below the allowable fatigue stress ranges according to AASHTO fatigue provisions [6]. The deflection check is used to ensure the serviceability of the bridge. According to the recommended specifications for the design of curved steel bridges [3], the superstructure should be first analyzed to determine the first mode of flexural vibration. The frequency of this mode is used to check the allowable deflection of the bridge as indicated in the Ontario Bridge Code[7].15.3.3Design ExampleFollowing the 1994 Northridge Earthquake in California, the California Department of Transpor-tation (Caltrans) embarked on a task of rebuilding damaged freeways as soon as possible. At the SR 14–I-5 interchange in the San Fernando Valley, several spans of cast-in-place prestressed concrete box girders have collapsed [9]. These were the same ramps that were previously damaged during the 1971 San Fernando Earthquake [8]. Because of the urgency of completion and the restrictions on geometry, steel plate girders were considered a viable replacement alternative. The idea was that the girders could be fabricated while the substructure was being constructed. Once the footings and columns were completed, the finished girders would be delivered to the job site. Therefore, in a period of 5 weeks Caltrans designed two different alternatives for two ramps approximately 396 m (1300 ft) and 457 m (1500 ft) in length. The South Connector Ramp will be discussed in this section. The “As-Built” South Connector was approximately 397 m (1302 ft) in length set on a horizontal curve with a radius of 198 m (650 ft) producing a superelevation of 11%. This ramp was designed utilizing Bridge Software Development International (BSDI) curved girder software package [10] as one frame with expansion joints at the abutments. This computer program is considered one of the most-advanced programs for the analysis and design of curved girder bridges. The program analyses the curved girders based on 3-D finite-element analysis and utilizes the influence surface for live-load analysis. The program has also an interactive postprocessor for performing designs and code checking. The design part of the program follows the 15th edition of AASHTO [13] and the Curved Girder Guide Specifications [1]. The ramp was then checked using DESCUS I [14], another software package, and spot-checked with in-house programs developed by Caltrans. A cross-sectional width of 11.43 m (37.5 ft) was selected for two lanes of traffic (3.66 m, 12 ft), two shoulders (1.52 m, 5 ft), and two concrete barriers (0.533 m, 1.75 ft). This ramp has a 212.7 mm (8⅜ inch) concrete deck, which was composite with four continuous welded plate girders with bolted field splices for erection. The material selected was A709 Grade 50W. The spans ranged from35.97 m (118 ft) up to 66.44 m (218 ft) in length, which meant the girder depths alone were around 2.2 m (7.25 ft) deep and the composite section was 2.44 m (8 ft) deep. The cross frames were a mixture of inverted K frames and plate diaphragms at the bents. The K frames were inverted so as to place the catwalks between the girders, and the braces were changed to plate sections at the bents to help handle the large seismic forces that are transmitted from the superstructure to the “ham-merhead” bent caps both longitudinally and transversely. The bracing was designed for both live-load and seismic-load conditions. Figure 15.12 shows the elevation of intermediate cross frames. The bracing was held to a spacing of less than 6.1 m (20 ft).The BSDI program works by placing unit loads on a defined geometry pattern of the deck. Then an influence surface is developed so that application of loads for maximum and minimum stresses becomes a simple numerical solution. This program was thoroughly checked utilizing the V-Load method and using an SC-Bridge package that utilizes GT Strudl [11] for the moving load generator. Good correlation was seen by all methods with the exception of the V-Load, which consistently gave more conservative results. As is frequently the case with curved girders, the outside girder ends up being designed heavier than the remaining sections. This difference can be as little as 15%, but as great at 40%, depending on location. It should also be understood that by designing a stiffer girder for the outside, there is the tendency to attract more loads, thereby requiring more material. This is a similar phenomenon to that seen in seismic design. The BSDI system allows the designer to check for construction loads and sequencing. This was absolutely critical on a project like this as the girder sections were often controlled by the sequence of construction load application. Limits on concrete pours were set around limiting stresses on the girders.Girder plate sizes were optimized both for the design and for the fabrication. A typical span would have five different sections in it. There were two sections at either end over the bents. The top and bottom flanges were very similar at point of maximum negative moment. Then on either side a transition section would be utilized until the inflection point. Finally, a maximum positive section where there is usually a significant difference in the top and bottom flanges was designed. The elevation of the plate girder that shows the different flange dimensions is shown in Figure 15.13. The five different flange dimensions were justified by considering the material costs vs. the welded splice costs. In addition, the “transition” sections were often sized such that the top flange width was the same as the negative moment sections. This way the plates could be welded end to end and then all four girders could be cut on one bed with one operation, saving handling costs. Plate sections were also set based on erection and shipping capabilities.Steel was a good choice of structure type for this project because of the seismic risk, which exists in this location. Several faults pass in the vicinity of this interchange, and the structure would be subjected to “near-fault” phenomenon. This structure was designed with vertical acceleration. The plate girder with concrete deck superstructure weighs one third as much as the traditional cast-in-place box structure. Some ductile steel details were developed for this project [12]. Since the girders rest on a hammerhead bent cap, the load transfer mechanism is through the bearings and the shear can be as much as the plastic shear of the column. To make this load transfer possible, plate diaphragms were designed at the bent caps. With the plates in place, a concrete diaphragm could be poured that would not only add stiffness, but strength to handle these large seismic forces. The diaphragms were approximately 0.91 m (3 ft) wide by the depth of the girder. The plates were covered with shear studs and reinforcing was placed prior to the concrete. In addition, pipe shear keys were installed in the top of the bent cap on either side of the diaphragm. This structure was redundant in that if the displacements were excessive, the pipes would be engaged.FIGURE 15.12Elevation of intermediate cross frames.FIGURE 15.13Elevation of interior and exterior curved plate girder.The most common type of curved steel box girder bridges are tub girders that consist of independent top flanges and cast-in-place reinforced concrete decks. The design guidelines are covered in the “Recommended Specifications for Steel Curved Girder Bridges”[3]. Normally the tub girder is composed of a bottom plate flange, two web plates, and an independent top flange attached to each web. The top flanges should be braced to become capable of resisting loads until the girder acts in a composite manner. The tub girders require internal bracing because of the distortion of the box due to the bending stresses. Finite-element analysis, which accounts for the distortion, is normally utilized to calculate the stresses and displacement of the box.The webs of the box girder may be inclined with a ratio of one-to-four, width-to-depth. The AASHTO provisions for straight box girders apply for curved boxes regarding the shear capacity of the web and the ultimate capacity of the tub girders. The maximum bending stresses are determined according to the factored loads with the considerations of composite and noncomposite actions. Bending stresses should be checked at critical sections during erection and deck placement. The bending stresses may be assumed uniform across the width of the box. Prior to curing of concrete, the top flanges of tub girders are to be assumed laterally supported at top flange lateral bracing. The longitudinal warping stresses in the bottom flange are computed based on the stiffness and spacing of internal bracing. It is recommended that the warping stresses should not exceed 15% of the maximum bending stresses.As mentioned earlier, the M/R method is usually used to analyze curved box girder bridges. The basic concept behind this method is the conjugate beam analogy. The method loads a conjugate simple span beam with a distributed loading, which is equal to the moment in the real simple or continuous span induced by the applied load divided by the radius of curvature of the girder. The reactions of the supports are obtained and thus the shear diagram can be constructed representing the internal torque diagram of the curved girder. After the concentrated torque at the ends of the floor beam is known, the end shears are computed from statics. These shears are applied as vertical concentrated loads at each cross frame location to determine the moment of the developed girder. This procedure constitutes a convergence process whereby the M/R values are applied until conver-gence is attained.Current curved bridge specifications in the United States do not have any guidelines regarding curved concrete box-girder bridges. It is generally believed that the concrete monolithic box girders have high torsional rigidity, which significantly reduces the effect of curvature. However, during the last 15 years a problem has occurred with small-radius horizontally curved, post-tensioned box-girder bridges. The problem has occurred at two known sites during the construction [16]. The problem can be summarized as, during the prestressing of tendons in a curved box girder, they break away from the web tearing all the reinforcement in the web along the profile of the tendon. Immediate inspection of the failure indicated that the tendons exerted radial horizontal pressure along the wall of the outermost web.In recognition of this problem, Caltrans has prepared and implemented design guidelines since the early 1980s [17]. Charts and reinforcement details were developed to check girder webs for containment of tendons and adequate stirrup reinforcement to resist flexural bending. Caltrans’Memo-to-Designers 11-31 specifies that designers of curved post-tensioned bridges should consider the lateral prestress force, F, for each girder. This force F is equal to the jacking force, P j, of each girder divided by the horizontal radius of the girder. If the ratio of P j/R > 100 kN/m per girder orthe horizontal radius is equal to 250 m or less, Detail A, as shown in Figure 15.14 should be used.Charts for No. 16 and No. 19 stirrups were developed to be used with the ratio of P j /R in order to get minimum web thickness and spacing between the No. 16 stirrups, as shown in Figure 15.15.The first step is to enter the chart with the value of F on the vertical axis of the chart and travel horizontally until the height of the web h c is reached. The chart then indicates the minimum web thickness and the spacing of the No. 16 stirrups.These charts were developed assuming that the girder web is a beam with a length equal to the clear distance between top and bottom slabs. The lateral force, F , is acting at the center point of the web creating a bending moment in the web. This moment is calculated by the simple beam formula reduced by 20% for continuity between the web and slabs. The value of this bending moment is equal to(15.1)In the commentary of this memo, Caltrans considered the stirrups to be capable of handling the bending and shear stresses for the following reasons:•M u is calculated for the maximum conditions of F acting at h c /2. This occurs at only two points in a span due to tendon drape.•The jacking force, P j , is used in the calculation of M u and, at the time P j is applied, the structure is supported on falsework. When the falsework is removed and vertical shear forces act, the prestressing forces will be reduced by the losses.In addition, for curve box girders with an inside radius of under 243.8 m (800 ft), intermediate diaphragms are required at a maximum spacing of 24.4 m (80 ft) unless shown otherwise by tests or structural analysis. The code goes further to say that if the inside radius is less than 121.9 m (400ft), the diaphragm spacing must not exceed 12.2 m (40 ft).FIGURE 15.14Caltrans duct detail in curved concrete bridges.The authors would like to thank Dr. Duan and Prof. Chen for selecting them to participate in this Bridge Engineering Handbook . The National Steel Bridge provided the photographs of curved bridges in this document for which the authors are sincerely grateful. The support and the cooperation of Mr. Dan Hall of BSDI are appreciated. Finally, the two authors warmly appreciate the continued support of Caltrans.References1.AASHTO, Guide Specifications for Horizontally Curved Highway Bridges , American Association ofState Highway and Transportation Officials, Washington, D.C., 1993, 1–111.FIGURE 15.15Caltrans chart design for web thickness and reinforcement.2.Mozar, J., Cook, J., and Culver, C., Horizontally Curved Highway Bridges-Stability of Curved PlateGirders, Report No. P1, Carnegie-Mellon University, CURT Program, Pittsburgh, PA, Sept. 1971.3.Hall, D. H. and Y oo, C. H., Curved Girder Design and Construction, Current Practice, NCHRPProject 12-38, 1995, 1–136.4.V-Load analysis, in USS Highway Structures Design Handbook, Vol. 1, AISC Marketing, Inc., Chi-cago, IL, 1984, chap. 12, 1–565.AISC, Highway Structure Design Handbook, Newsletter Issue No. 2, AISC Marketing, Chicago, IL,19916.AASHTO, LRFD Bridge Design Specifications, American Association of State Highway and Trans-portation Officials, Washington, D.C, 1994.7.Ontario Highway Bridge Design Code, 3rd ed., Ministry of Transportation and Communications,Highway Engineering Division, Toronto, Ontario, 1991.8.The San Fernando Earthquake — Field Investigation of Bridge Damage, State of California, Cal-trans, Division of Structures, Sacramento, 1991.9.Northridge Earthquake — Field Investigation of Bridge Damage, State of California, Caltrans,Division of Structures, Sacramento, 1994.10.Hall, D. H., BSDI 3D System, Internal Document, Bridge Software Development International,Ltd., Coopersburg, PA, 1994.11.SC-Bridge, User’s Guide, Version 2.1, SC Solutions, Mountain View, CA, 1994.12.Itani, A. and Reno, M., Seismic design of modern steel highway connectors, in ASCE StructuresCongress, Vol. 2, 1995, 1528–1531.13.AASHTO, Standard Specifications for Highway Bridges, 15th ed. with interim’s, American Associa-tion of State Highway and Transportation Officials, Washington, D.C., 1994.14.DESCUS I and II, Opti-Mate, Inc., Bethlehem, PA.15.Analysis and Design of Horizontally Curved Steel Bridges, U.S. Steel Structural Report ADUCO91063, May 1963.16.Podolny, W., The cause of cracking in post-tensioned concrete box girder bridges and retrofitprocedures, PCI J., March 1985.17.Caltrans, Bridge Memo-to-Designers, Vol. 1, California Department of Transportation, Sacra-mento, 1996.18.Hall, D.H. and Y oo, C.H., Recommended Specifications for Steel Curved-Girder Bridges, NCHRPProject 12–38. BSDI, Ltd., Coopersburg, PA, Dec. 1998.19.NCHRP (12–52), LRFD Specifications for Horizontally Curved Steel Girder Bridges, Transporta-tion Research Board, Washington, D.C.。
桥梁工程教材桥梁工程目录1.桥梁工程名词解释 (02)2.桥梁工程与道路工程、隧道工程的关系 (34)3.桥梁工程总复习题 (34)4.桥梁工程教案 (43)5.东南大学考试试题 (82)6.公路工程常识 (86)7.附示意图 (87)图书编号ISBN 7-114-521-5编辑单位：临汾公路分局长安大学公路学院中国路桥（集团）总公司桥梁工程名词解释【桥梁的基本组成部分：1.上部结构：是线路中断时跨越障碍的主要承重结构，包括桥跨结构（梁）和桥面构造两大部分；2.下部结构：指支座以下的支撑结构，包括桥墩、桥台、基础，桥台与路堤相连接抵御路堤土压力，防治土塌落。
3.支座 4.附属设施【净跨径：设支座桥梁为相邻两墩、台身顶内缘之间水平净距。
对不设支座为上下部结构相交处内缘间的水平距离【总跨径多孔桥梁中各孔净跨径的总和反映宣泄洪水能力【计算跨径：对设支座，为相邻支座中心的水平距离，对不设的，为上下部结构相交面之中心间水平距离【标准跨径：对梁式桥、板石桥以两桥墩中线之间桥中心线长度，拱式桥和涵洞以净跨径为主【桥梁全长：桥长。
有桥台的桥梁为两岸桥台翼墙尾端间距离，无桥台为桥面系行车道长度【桥下净空：满足通航的需要和保证桥梁安全而对上部结构底缘以下规定的空间界限【桥梁建筑高度：上部结构底缘至桥面顶面的垂直距离。
不得大于容许建筑高度（线路定线确定桥面高程与通航净空界限顶部高程之差）【桥面净空：桥梁行车道、人行道上方应保持的空间界限【低水位：枯水季节最低水位【高水位：洪水季节河流中最高水位【设计水位：桥梁设计中按规定设计洪水频率计算所得的高水位【通航水位：各级航道中，能保持船舶正常航行水位【桥梁体系分类梁式桥—主梁受弯拱桥—主拱受压刚构桥—构件受弯压缆索承重—缆索受拉组合体系—几种受力的组合【桥梁的主要类型（基本构件受力）1.梁式桥：最古老、最普遍、最实用的结构体系。
主要受力特点：竖向荷载作用下无水平反力。
主要优点：施工方便，对地基承载力要求不高，技术成熟。
第1篇一、前言桥梁工程是现代城市建设的重要组成部分，其施工质量直接关系到桥梁的安全性和使用寿命。
为了帮助桥梁工程施工人员掌握施工技术，提高施工质量，特编写本便携手册。
本手册旨在为桥梁工程施工人员提供实用、便捷的施工指导，以保障桥梁工程顺利进行。
二、桥梁工程施工基础知识1. 桥梁工程类型：桥梁工程主要分为梁桥、拱桥、斜拉桥、悬索桥等类型。
2. 桥梁结构组成：桥梁结构主要由桥跨结构、桥墩、桥台、基础等组成。
3. 桥梁施工顺序：桥梁施工顺序一般分为基础施工、下部结构施工、上部结构施工、桥面系施工等阶段。
4. 桥梁施工工艺：桥梁施工工艺包括预制、现浇、装配式等。
三、桥梁工程施工关键技术1. 基础施工：基础施工是桥梁工程的关键环节，主要包括钻孔灌注桩、挖孔桩、地下连续墙等施工方法。
2. 下部结构施工：下部结构施工主要包括桥墩、桥台等施工，主要施工方法有现浇混凝土、装配式构件等。
3. 上部结构施工：上部结构施工主要包括梁体、桥面板等施工，主要施工方法有预制、现浇、装配式等。
4. 桥面系施工：桥面系施工主要包括桥面防水、排水、铺装等施工。
四、桥梁工程施工安全与质量控制1. 安全生产：桥梁工程施工过程中，应严格执行安全生产法规，加强现场安全管理，确保施工人员生命安全。
2. 质量控制：桥梁工程施工过程中，应严格执行质量验收规范，加强施工过程控制，确保桥梁工程质量。
五、桥梁工程施工管理1. 施工组织设计：桥梁工程施工前，应编制详细的施工组织设计，明确施工方案、施工工艺、施工进度、施工安全等。
2. 施工协调：桥梁工程施工过程中，应加强各施工工序之间的协调，确保施工进度和质量。
3. 施工资料管理：桥梁工程施工过程中，应做好施工资料的管理工作，包括施工记录、验收记录、试验报告等。
六、桥梁工程施工案例分析本手册列举了桥梁工程施工中的典型案例，以供读者参考。
总结：《桥梁工程施工便携手册》旨在为桥梁工程施工人员提供实用、便捷的施工指导，帮助提高桥梁工程施工质量。
2323.1 IntroductionRailroad Network •Basic Differences betweenRailroad and Highway Bridges •Manual for RailwayEngineering, AREMA 23.2 Railroad Bridge Philosophy23.3 Railroad Bridge Types23.4 Bridge DeckGeneral •Open Deck •Ballast Deck •DirectFixation •Deck Details23.5 Design CriteriaGeometric Considerations •Proportioning •Bridge Design Loads •Load Combinations •Serviceability Considerations23.6 Capacity Rating General •Normal Rating •Maximum Rating23.1.1 Railroad NetworkThe U.S. railroad network consists predominantly of privately owned freight railroad systems classified according to operating revenue, the government-owned National Railroad Passenger Cor-poration (Amtrak), and numerous transit systems owned by local agencies and municipalities.Since the deregulation of the railroad industry brought about by the 1980 Staggers Act, there have been numerous railway system mergers. By 1997 there remained 10 Class I (major) Railroads,32 Regional Railroads, and 511 Local Railroads operating over approximately 150,000 track miles.The 10 Class I Railroads comprise only 2% of the number of railroads in the United States but account for 73% of the trackage and 91% of freight revenue.By far the present leading freight commodity is coal, which accounts for 25% of all the carloads.Other leading commodities in descending order by carloads are chemicals and allied products, farm products, motor vehicles and equipment, food and sundry products, and nonmetallic minerals.Freight equipment has drastically changed over the years in container type, size and wheelbase, and carrying capacity. The most predominant freight car is the hopper car used with an open top for coal loading and the covered hopper car used for chemicals and farm products. In more recent years special cars have been developed for the transportation of trailers, box containers, and automobiles. The It should be noted that much of this material was developed for the American Railway Engineering and Maintenance of Way Association (AREMA) Structures Loading Seminar. This material is used with the permission of AREMA.Donald F. SorgenfreiModjeski and Masters, Inc.W. N. Marianos, Jr.Modjeski and Masters, Inc.average freight car capacity (total number of freight cars in service divided by the aggregate capacity of those cars) has risen approximately 10 tons each decade with the tonnage ironically matching the decades, i.e., 1950s — 50 tons, 1960s — 60 tons, and so on. As the turn of the century approaches, various rail lines are capable of handling 286,000 and 315,000-lb carloads, often in dedicated units. In 1929 there were 56,936 steam locomotives in service. By the early 1960s they were nearly totally replaced by diesel electric units. The number of diesel electric units has gradually decreased as available locomotive horsepower has increased. The earlier freight trains were commonly mixed freight of generally light railcars, powered by heavy steam locomotives. In more recent years that has given way to heavy railcars, unit trains of common commodity (coal, grain, containers, etc.) with powerful locomotives. Newer locomotives generally have six axles, weigh 420,000 lbs, and can generate up to 8000 Hp.These changes in freight hauling have resulted in concerns for railroad bridges, many of which were not designed for these modern loadings. The heavy, steam locomotive with steam impact governed in design considerations. Present bridge designs are still based on the steam locomotive wheel configuration with diesel impact, but fatigue cycles from the heavy carloads are of major importance.The railroad industry records annual route tonnage referred to as “million gross tons” (MGT). An experienced railroader can fairly well predict conditions and maintenance needs for a route based on knowing the MGT for that route. It is common for Class I Railroads to have routes of 30 to 50 MGT with some coal routes in the range of 150 MGT.Passenger trains are akin to earlier freight trains, with one or more locomotives (electric or diesel) followed by relatively light cars. Likewise, transit cars are relatively light.23.1.2 Basic Differences between Railroad and Highway BridgesA number of differences exist between railroad and highway bridges:1.The ratio of live load to dead load is much higher for a railroad bridge than for a similarlysized highway structure. This can lead to serviceability issues such as fatigue and deflection control governing designs rather than strength.2.The design impact load on railroad bridges is higher than on highway structures.3.Simple-span structures are preferred over continuous structures for railroad bridges. Manyof the factors that make continuous spans attractive for highway structures are not as advan-tageous for railroad use. Continuous spans are also more difficult to replace in emergencies than simple spans.4.Interruptions in service are typically much more critical for railroads than for highwayagencies. Therefore, constructibility and maintainability without interruption to traffic are crucial for railroad bridges.5.Since the bridge supports the track structure, the combination of track and bridge movementcannot exceed the tolerances in track standards. Interaction between the track and bridge should be considered in design and detailing.6.Seismic performance of highway and railroad bridges can vary significantly. Railroad bridgeshave performed well during seismic events.7.Railroad bridge owners typically expect a longer service life from their structures than highwaybridge owners expect from theirs.23.1.3Manual for Railway Engineering, AREMAThe base document for railroad bridge design, construction, and inspection is the American Railway Engineering Maintenance of Way Association (AREMA) Manual for Railway Engineering (Manual) [1].Early railroads developed independent specifications governing the design loadings, allowable strains, quality of material, fabrication, and construction of their own bridges. There was a prolif-eration of specifications written by individual railroads, suppliers, and engineers. One of the earliest general specifications is titled Specification for Iron Railway Bridges and Viaducts, by Clarke, Reeves and Company (Phoenix Bridge Company). By 1899 private railroads joined efforts in forming AREMA. Many portions of those original individual railroad specifications were incorporated into the first manual titled Manual of Recommended Practice for Railway Engineering and Maintenance of Way published in 1905. In 1911 the Association dropped “Maintenance of Way” from its name and became the American Railway Engineering Association (AREA); however, in 1997 the name reverted back to the original name with the consolidation of several railroad associations.The Manual is not deemed a specification but rather a recommended practice. Certain provisions naturally are standards by necessity for the interchange of rail traffic, such as track gauge, track geometrics, clearances, basic bridge loading, and locations for applying loadings. Individual rail-roads may, and often do, impose more stringent design requirements or provisions due to differing conditions peculiar to that railroad or region of the country, but basically all railroads subscribe to the provisions of the Manual.Although the Manual is a multivolume document, bridge engineering provisions are grouped in the Structural Volume and subdivided into applicable chapters by primary bridge material and special topics, as listed:Chapter 7 Timber StructuresChapter 8Concrete Structures and FoundationsChapter 9Seismic Design for Railway StructuresChapter 10Structures Maintenance & Construction (New)Chapter 15Steel StructuresChapter 19Bridge BearingsChapter 29WaterproofingThe primary structural chapters each address bridge loading (dead load, live load, impact, wind, seismic, etc.) design, materials, fabrication, construction, maintenance/inspection, and capacity rating. There is uniformity among the chapters in the configuration of the basic live load, which is based on the Cooper E-series steam locomotive. The present live-load configuration is two loco-motives with tenders followed by a uniform live load as shown in Fig. 23.1. There is not uniformity in the chapters in the location and magnitude of many other loads due to differences in the types of bridges built with different materials and differences in material behavior. Also it is recognized that each chapter has been developed and maintained by separate committee groups of railroad industry engineers, private consulting engineers, and suppliers. These committees readily draw from railroad industry experiences and research, and from work published by other associations such as AASHTO, AISC, ACI, AWS, APWA, etc.Railroad routes are well established and the construction of new railroad routes is not common; thus, the majority of railroad bridges built or rehabilitated are on existing routes and on existing right-of-way. Simply stated, the railroad industry first extends the life of existing bridges as long as economically justified. It is not uncommon for a railroad to evaluate an 80- or 90-year-old bridge, estimate its remaining life, and then rehabilitate it sufficiently to extend its life for some economical period of time. Bridge replacement generally is determined as a result of a lack of load-carrying capacity, restrictive clearance, or deteriorated physical condition. If bridge replacement is necessary, then simplicity, cost, future maintenance, and ease of construction without significant rail traffic disruptions typically govern the design. Types of bridges chosen are most often based on the capability of a railroad to do itsown construction work. Low-maintenance structures, such as ballasted deck prestressed concrete box-girder spans with concrete caps and piles, are preferred by some railroads. Others may prefer weathering steel elements.In a review of the existing railroad industry bridge inventory, the majority of bridges by far are simple-span structures over streams and roadways. Complex bridges are generally associated with crossing major waterways or other significant topographical features. Signature bridges are rarely constructed by railroads. The enormity of train live loads generally preclude the use of double-leaf bascule bridges and suspension and cable-stayed bridges due to bridge deflection and shear load transfer, respectively. Railroads, where possible, avoid designing skewed or curved bridges, which also have inherent deflection problems.When planning the replacement of smaller bridges, railroads first determine if the bridge can be eliminated using culverts. A hydrographic review of the site will determine if the bridge opening needs to be either increased or can be decreased.The Manual provides complete details for common timber structures and for concrete box-girder spans. Many of the larger railroads develop common standards, which provide complete detailed plans for the construction of bridges. These plans include piling, pile bents, abutments and wing walls, spans (timber, concrete, and steel), and other elements in sufficient detail for construction by in-house forces or by contract. Only site-specific details such as permits, survey data, and soil conditions are needed to augment these plans.Timber trestles are most often replaced by other materials rather than in kind. However, it is often necessary to renew portions of timber structures to extend the life of a bridge for budgetary reasons. Replacing pile bents with framed bents to eliminate the need to drive piles or the adding of a timber stringer to a chord to increase capacity is common. The replacement of timber trestles is commonly done by driving either concrete or steel piling through the existing trestle, at twice the present timber span length and offset from the existing bents. This is done between train movements. Either precast or cast-in-place caps are installed atop the piling beneath the existing timber deck. During a track outage period, the existing track and timber deck is removed and new spans (concrete box girders or rolled steel beams) are placed. In this type of bridge renewal, key factors are use of prefabricated bridge elements light enough to be lifted by railroad track mounted equipment (piles, caps, and spans), speed of installation of bridge elements between train move-ments, bridge elements that can be installed in remote site locations without outside support, and overall simplicity in performing the work.The railroad industry has a large number of 150 to 200 ft span pin-connected steel trusses, many with worn joints, restrictive clearances, and low carrying capacity, for which rehabilitation cannot be economically justified. Depending on site specifics, a common replacement scenario may be to install an intermediate pier or bent and replace the span with two girder spans. Railroad forces have perfected the technique of laterally rolling out old spans and rolling in new prefabricated spans between train movements.Railroads frequently will relocate existing bridge spans to other sites in lieu of constructing new spans, if economically feasible. This primarily applies to beam spans and plate girder spans up to 100 ft in length.In general, railroads prefer to construct new bridges online rather than relocating or doglegging to an adjacent alignment. Where site conditions do not allow ready access for direct span replace-ment, a site bypass, or runaround, called a “shoofly” is constructed which provides a temporary bridge while the permanent bridge is constructed.The design and construction of larger and complex bridges is done on an individual basis. Railroad bridges are nearly always simple-span structures. Listed below in groupings by span length are the more common types of bridges and materials used by the railroad industry for those span lengths.Short spans to 16 ft Timber stringersConcrete slabsRolled steel beamsto 32 ft Conventional and prestressed concrete box girders and beamsRolled steel beamsto 50 ft Prestressed concrete box girders and beamsRolled steel beams, deck and through girdersMedium spans, 80 to 125 ft Prestressed concrete beamsDeck and through plate girdersLong spans Deck and through trusses (simple, cantilever, and arches) Suspension bridges are not used by freight railroads due to excessive deflection.23.4.1 GeneralThe engineer experienced in highway bridge design may not think of the typical railroad bridge as having a deck. However, it is essential to have a support system for the rails. Railroad bridges typically are designed as either open deck or ballast deck structures. Some bridges, particularly in transit applications, use direct fixation of the rails to the supporting structure.23.4.2 Open DeckOpen deck bridges have ties supported directly on load-carrying elements of the structure (such as stringers or girders). The dead loads for open deck structures can be significantly less than for ballast deck structures. Open decks, however, transfer more of the dynamic effects of live load into the bridge than ballast decks. In addition, the bridge ties required are both longer and larger in cross section than the standard track ties. This adds to their expense. Bridge tie availability has declined, and their supply may be a problem, particularly in denser grades of structured timber.TABLE 23.1Weight of Rails, Inside Guard Rails, Ties, Guard Timbers, and Fasteningsfor Typical Open Deck (Walkway not included)Item(plf of track)Rail (136 RE):(136 lb/lin. yd × 2 rails/track × 1 lin. yd/3 lin. ft)91Inside guard rails:(115 lb/lin. yd × 2 rails/track × 1 lin. yd/3 lin. ft)77Ties (10 in. × 10 10 ft bridge ties):(10 in. × 10 in. × 10 ft × 1 ft2/144 in.2× 60 lb/ft3× 1 tie/14 in. × 12 in./1 ft)357Guard Timbers (4 × 8 in.):(4 in. × 8 in. × 1 ft × 1 ft2/144 in.3× 60 lb/1 ft3× 2 guard timbers/ft)27Tie Plates (7¾× 14¾ in. for rail with 6 in. base):24.32 lb/plate × 1 tie/14 in. × 12 in./ft × 2 plates/tie)42Spikes (⁵⁄₈×⁵⁄₈ in. × 6 in. reinforced throat)(0.828 lb/spike × 18 spikes/tie × 1 tie/14 in. × 12 in./1 ft)13Miscellaneous Fastenings (hook bolts and lag bolts):(Approx. 2.25 lb/hook bolt + 1.25 lb/lag screw × 2 bolts/tie × 1 tie/14 in. × 12 in./ft)6Total weight613Item(plf of track)Rail (136 RE):(136 lb/lin. yd. × 2 rails/track × 1 lin. yd/3 lin. ft)91Inside Guard Rails:(115 lb/lin. yd × 2 rails/track × 1 lin. yd/3 lin. ft)77Ties (neglect, since included in ballast weight)—Guard Timbers (4 × 8 in.):(4 in. × 8 in. × 1 ft × 1 ft2/144 in.2× 60 lb/1 ft3× 2 guard timbers/ft)27Tie Plates (7¾× 14¾ in. for rail with 6 inc. base):(24.32 lb/plate × 1 tie/19.5 in. × 12 in./ft × 2 plates/tie)30Spikes (⁵⁄₈×⁵⁄₈× 6 in. reinforced throat)(0.828 lb/spike × 18 spikes/tie × 1 tie/19.5 in. × 12 in./1 ft)9Ballast (assume 12 in. additional over time)(Approx. 120 lb/ft3× 27 in. depth/12 in./1 ft × 16 ft)4320Waterproofing:(Approx. 150 lb/ft3× 0.75 in. depth/12 in./1 ft × 20 ft)188Total weight:474223.4.3Ballast DeckBallast deck bridges have the track structure supported on ballast, which is carried by the structural elements of the bridge. Typically, the track structure (rails, tie plates, and ties) is similar to track constructed on grade. Ballast deck structures offer advantages in ride and maintenance require-ments. Unlike open decks, the track alignment on ballast deck spans can typically be maintained using standard track maintenance equipment. If all other factors are equal, most railroads currently prefer ballast decks for new structures.In ballast deck designs, an allowance for at least 6 in. of additional ballast is prudent. Specific requirements for additional ballast capacity may be provided by the railroad. In addition, the required depth of ballast below the tie should be verified with the affected railroad. Typical values for this range from 8 to 12 in. or more. The tie length used will have an effect on the distribution of live-load effects into the structure. Ballast decks are also typically waterproofed. The weight of waterproofing should be included in the dead load. Provisions for selection, design, and installation of waterproofing are included in Chapter 29 of the AREMA Manual.23.4.4Direct FixationDirect fixation structures have rails supported on plates anchored directly to the bridge deck or superstructure. Direct fixation decks are much less common than either open decks or ballast decks and are rare in freight railroad service. While direct fixation decks eliminate the dead load of ties and ballast, and can reduce total structure height, they transfer more dynamic load effects into the bridge. Direct fixation components need to be carefully selected and detailed.23.4.5Deck DetailsWalkways are frequently provided on railroad bridge decks. They may be on one or both sides of the track. Railroads have their own policies and details for walkway placement and construction. Railroad bridge decks on curved track should allow for superelevation. With ballast decks, this can be accomplished by adjusting ballast depths. With open decks, it can require the use of beveled ties or building the superelevation into the superstructure.Continuous welded rail (CWR) is frequently installed on bridges. This can affect the thermal movement characteristics of the structure. Check with the affected railroad for its policy on anchor-age of CWR on structures. Long-span structures may require the use of rail expansion joints.23.5.1Geometric ConsiderationsRailroad bridges have a variety of geometric requirements. The AREMA Manual has clearance diagrams showing the space required for passage of modern rail traffic. It should be noted that lateral clearance requirements are increased for structures carrying curved track. Track spacing on multiple-track structures should be determined by the affected railroad. Safety concerns are leading to increased track-spacing requirements.If possible, skewed bridges should be avoided. Skewed structures, however, may be required by site conditions. A support must be provided for the ties perpendicular to the track at the end of the structure. This is difficult on open deck structures. An approach slab below the ballast may be used on skewed ballast deck bridges.23.5.2ProportioningTypical depth-to-span length ratios for steel railroad bridges are around 1:12. Guidelines for girder spacing are given in Chapter 15 of the Manual.23.5.3Bridge Design Loads23.5.3.1Dead LoadDead load consists of the weight of the structure itself, the track it supports, and any attachments it may carry. Dead loads act due to gravity and are permanently applied to the structure. Unit weights for calculation of dead loads are given in AREMA Chapters 7, 8, and 15. The table in Chapter 15 is reproduced below:Unit Weights for Dead Load StressesSteel490Concrete150Sand, gravel, and ballast120Asphalt-mastic and bituminous macadam150Granite170Paving bricks150Timber60Dead load is applied at the location it occurs in the structure, typically as either a concentrated or distributed load.The Manual states that track rails, inside guard rails, and rail fastenings shall be assumed to weigh 200 pounds per linear foot (plf) of track. The 60 pound per cubic foot weight given for timber should be satisfactory for typical ties. Exotic woods may be heavier. Concrete ties are sometimes used, and their heavier weight should be taken into account if their use is anticipated.In preliminary design of open deck structures, a deck weight of 550 to 650 plf of track can be assumed. This should be checked with the weight of the specific deck system used for final design. Example calculations for track and deck weight for open deck and ballast deck structures are included in this chapter.Railroad bridges frequently carry walkways and signal and communication cables and may be used by utilities. Provisions (both in dead load and physical location) may need to be made for these additional items. Some structures may even carry ornamental or decorative items.23.5.3.2Live LoadHistorically, freight railroads have used the Cooper E load configuration as a live-load model. The Cooper E80 load is currently the most common design live load. The E80 load model is shown in Figure 23.1. The 80 in E80 refers to the 80 kip weight of the locomotive drive axles. An E60 load has the same axle locations, but all loads are factored by 60/80. Some railroads are designing new structures to carry E90 or E100 loads.The Cooper live-load model does not match the axle loads and spacings of locomotives currently in service. It did not even reflect all locomotives at the turn of the 20th century, when it was introduced by Theodore Cooper, an early railroad bridge engineer. However, it has remained in use throughout the past century. One of the reasons for its longevity is the wide variety of rail rolling stock that has been and is currently in service. The load effects of this equipment on given spans must be compared, as discussed in Section 23.6. The Cooper live-load model gives a universal system with which all other load configurations can be compared. Engineering personnel of each railroad can calculate how the load effects of each piece of equipment compare to the Cooper loading.The designated steel bridge design live load also includes an “Alternate E80” load, consisting of four 100-kip axles. This is shown in Figure 23.2. This load controls over the regular Cooper load on shorter spans.A table of maximum load effects over various span lengths is included in Chapter 15, Part 1 of the AREMA Manual .23.5.3.3ImpactImpact is the dynamic amplification of the live-load effects on the bridge caused by the movement of the train across the span. Formulas for calculation of impact are included in Chapters 8 and 15of the AREMA manual. The design impact values are based on an assumed train speed of 60 mph.It should be noted that the steel design procedure allows reduction of the calculated impact for ballast deck structures. Different values for impact from steam and diesel locomotives are used. The steam impact values are significantly higher than diesel impact over most span lengths.FIGURE 23.1Cooper E8O live load.FIGURE 23.2Alternate live load.Impact is not applied to timber structures, since the capacity of timber under transient loads is significantly higher than its capacity under sustained loads. Allowable stresses for timber design are based on the sustained loads.23.5.3.4Centrifugal ForceCentrifugal force is the force a train moving along a curve exerts on a constraining object (track and supporting structure) which acts away from the center of rotation. Formulas or tables for calculation of centrifugal force are included in Chapters 7, 8, and 15 of the AREMA manual. The train speed required for the force calculation should be obtained from the railroad.Although the centrifugal action is applied as a horizontal force, it can produce overturning moment due to its point of application above the track. Both the horizontal force and resulting moment must be considered in design or evaluation of a structure.The horizontal force tends to displace the structure laterally:•For steel structures (deck girders, for example), it loads laterals and cross frames.•For concrete structures (box girders, for example), the superstructure is typically stiff enough in the transverse direction that the horizontal force is not significant for the superstructure.For all bridge types, the bearings and substructure must be able to resist the centrifugal horizontal force.The overturning moment tends to increase the live-load force in members on the outside of the curve and reduce the force on inside members. However, interior members are not designed with less capacity than exterior members. Substructures must be designed to resist the centrifugal overturning moment. This will increase forces toward the outside of the curve in foundation elements. The centrifugal force is applied at the location of the axles along the structure, 6 ft above the top of rail, at a point perpendicular to the center of a line connecting the rail tops. The effect of track superelevation may compensate somewhat for centrifugal force. The plan view location of the curved track on the bridge (since railroad bridge spans are typically straight, laid out along the curve chords) can also be significant. Rather than applying the centrifugal force at each axle location, some railroads simply increase the calculated live-load force by the centrifugal force percentage, factor in the effect of the force location above the top of rail, and use the resulting value for design.23.5.3.5Lateral Loads from EquipmentThis item includes all lateral loads applied to the structure due to train passage, other than centrifugal force. The magnitude and application point of these loads varies among Chapters 7, 8, and 15. For timber, a load of 20 kips is applied horizontally at the top of rail. For steel, a load of one quarter of the heaviest axle of the specified live load is applied at the base of rail. In both cases, the lateral load is a moving concentrated load that can be applied at any point along the span in either horizontal direction. It should be noted that lateral loads from equipment are not included in design of concrete bridges. However, if concrete girders are supported on steel or timber substructures, lateral loads should be applied to the substructures.Lateral loads from equipment are applied to lateral bracing members, flanges of longitudinal girders or stringers without a bracing system, and to chords of truss spans. Experience has shown that very high lateral forces can be applied to structures due to lurching of certain types of cars. Wheel hunting is another phenomenon that applies lateral force to the track and structure. Damaged rolling stock can also create large lateral forces.It should be noted that there is not an extensive research background supporting the lateral forces given in the AREMA Manual. However, the lateral loads in the Manual have historically worked well when combined with wind loads to produce adequate lateral resistance in structures.。
