Discuss the construction temperature and crack of the
concrete lightly
By G. K. Kululanga, W. Kuotcha, R. McCaffer, Member, ASCE, and F. Edum-Fotwe ,The American Society of Civil Engineers
The summary , In order to prevent the owners of the concrete work of claims, we must do a good job in the construction process in the temperature and crack
control,through observation live for many years, through consulting the monograph about stress within the concrete, explain to concrete temperature reason , on-the-spot concrete control and measure , prevention of crack of temperature that crack produce. Keyword Concrete Temperature stress Crack Control
1. The concrete occupies the important position in modern engineering construction. But today, the crack of the concrete is comparatively general, the cracks are nearly omnipresent in the science of bridge building. Though we take various kinds of measures in constructing, careful, but the crack still occurs now and then. Tracing it to its cause, it is one of them incompletely that our change to concrete temperature stress pays attention to. In the large volume concrete, temperature stress and temperature control are significant. This is mainly because of the reason of two respects. First of all, concrete often appear the temperature crack in not constructing, influence the globality and durability of the structure. Secondly, in the course of operating, the temperature change has remarkable influence that can't be ignored on the stress state of the structure. We meet to construct temperature crack in mainly, so only to origin cause of formation and treatment measure, concrete of crack make a discussion in constructing this text.
Reason of a crack
Have many kinds of reasons to produce the crack in the concrete, it is mainly the changes of temperature and humidity, fragility and disparity of the concrete, and the structure is unreasonable, the raw materials is not up to standard (if the alkali aggregate react), the template is out of shape, the foundation does not subside etc. evenly . The cement emits a large amount of heat of hydration when the concrete is hardenned, inside temperature is rising constantly, cause the stress of drawing on the surface. In the course of lowering the temperature , is it congeal foundation pay restrain to mix always later stage, will present the stress of drawing within the concrete . Reducing of temperature can surface cause heavy stress of drawing very in concrete too. When these draw the stress and go beyond resisting the ability of splitting of concrete , namely will present the crack .
A lot of inside humidity of concrete change very light or change relatively slow, surface humidity might change heavy the violent change takes placing. Such as maintaining thoroughly, when getting wetter when not doing,contract surface there aren't deformation doing, often cause the crack too. The concrete is a kind of fragility material , tensile strength is about 1/10 of the compression strength, is it carry on one's shoulder or back limit when draw out of shape to have *104 only , is it carry on one's shoulder or back
limit location when stretch out of shape to there is *104 to add for a long time to add a short time. Because raw materials even, water dust than unstable, transport and build phenomenon of emanating of course, its tensile strength is not even in the same concrete, a lot of resist the ability of drawing very low, it is apt to present the weak position of the crack. Among armored concrete , draw stress to undertake by reinforcing bar mainly , concrete bear stress of keeping just. Or reinforcing bar mix if edge position gone to to congeal present the stress of drawing in the structure in plain concrete, must rely on the concrete oneself to bear . Require to avoid the stress of drawing or only very small stress of drawing appears of the the general design. But the concrete is cooled from maximum temperature to the steady temperature of operating period in constructing, often cause sizable to draw the stress within the concrete. The temperature stress can exceed other outsides and load the stresses caused sometimes, know change law , temperature of stress for carry on reasonable structural design and construct extremely important.
Analysis of 2 temperature stresses
Can be divided into following three stages according to the forming process of the temperature stress:
(1)It is early: Build concrete is it is it over basically to send out heat to cement to begin , generally one one day by oneself. Two characteristics at this stage, first, the cement emits a large amount of heat of hydration, second , mix and congeal the changing sharply of elastic model quantity. Because of the change of elastic model quantity , form the remaining stress in the concrete in this period.
(2)Middle period: Up till the concrete is cooled until stability temperature from cement send out heat function basically when expiring, in this period, the temperature stress is mainly because the cooling of the concrete and external temperature change cause, these stresses and remnants stresses that is formed in early days are superposed , mix and congeal the elastic mould amount that goes to and does not change much during this period.
(3)Later period: Operation period after the complete cooling of concrete. Temperature stress whether external temperature change cause mainly, these stresses and first two kinds of remnants stresseses are changed and added .
Can be divided into two kinds according to the reason why the temperature stress causes:
(1)Spontaneous stress: There are not any restraint or totally static structure at the border, if inside temperature is non-linear distribution, temperature stress appearing because structure restrains from each other. For example, the body of mound of the bridge, the physical dimension is relatively large, surface temperature is low when the concrete is cooled, inside temperature is high, present the stress of drawing on the surface, present the stress of pressing in the middle.
(2)Restrain the stress: All of the structure ones or it restrain external one some border,can't out of shape and stress not cause not free. Such as case roof beam roof concrete and guardrail concrete.
This two kinds of temperature stresses draw back stresses caused to act on with the doing of concrete together frequently. It is a more complicated job to want to analyse the distribution , size of the temperature stress accurately according to known temperature. In case of great majority , need to rely on the model test or the number value to calculate. To
is it make temperature stress have sizable limp to creep concrete, at the stress accounting temperature, must consider the influence that creep , calculate concretly that no longer states thinly here.
Control and preventing the measure of the crack of 3 temperature
For prevent crack , lighten temperature stress can from control temperature and is it is it set about to restrain terms from two to improve.
The measure of controlling temperature is as follows:
(1)Is it improve aggregate grade mix , is it do rigid concrete to spend , mix mixture to adopt, is it guide angry pharmaceutical or plastification pharmaceutical ,etc. measure in order to reduce cement consumption of concrete to add;
(2)Add water or the water to cool the broken stone in order to reduce the temperature of building of the concrete while mixing and shutting the concrete;
(3)Reduce the thickness of building while building the concrete on hot day, utilize and build the aspect to dispel the heat;
(4)Bury the water pipe underground in the concrete, enter the cold water to lower the temperature openly;
(5)Stipulate rational form removal time, the temperature keeps warm the surface while lowering suddenly, in case that the rapid temperature gradient takes place in the concrete surface;
(6)The concrete with medium and long-term and exposed construction builds a piece of surface or thin wall structure, take the measure of keeping warm in cold season;
The measure of improving condition of restraining is:
(1)Divide and sew and divide one rationally ;
(2)Prevent the foundation from rising and falling too big;
(3)Rational arrangement construction process, prevent the too big discrepancy in elevation and side from exposing for a long time;
In addition, improve the performance of the concrete and improve and resist the ability of splitting, strengthen maintenance , prevent the surface from being done and contracted , especially guarantee the quality of the concrete is very important to preventing the crack, should pay special attention to avoiding producing and running through the crack , the globality resumed its structure after appearing is very difficult, so should rely mainly on preventing the emergence of the running through crack while constructing.
In construction of concrete , for raise turnover rate of template , demand concrete form removal as soon as possible that build newly often. Should consider form removal time properly when concrete temperature is higher than the temperature, so as not to cause the superficial early crack of concrete. Building the early form removal newly, cause very large stress of drawing on the surface, the phenomenon that " temperature is assaulted " appears. Build initial stage in concrete, because heat of hydration is sent out, the surface causes sizable to draw the stress, surface temperature is also higher than temperature at this moment, remove the template at this moment , surface temperature is lowered suddenly, must cause temperature gradient , thus add and draw the stress on the surface , change and add with the heat of hydration stress, in addition, the concrete dries and contracts , the superficial stress of drawing reaches very great number value, have danger of causing the crack, but cover a light-duty heat insulator with on the surface in time after
removing the template , for instance foam sponge ,etc., for prevent concrete surface from produce the too big stress of drawing, have remarkable results.
Add muscle influence to large volume temperature stress of concrete very light , because large volume concrete include muscle to be rate very much low. Just have influence on the general armored concrete. On terms that temperature is not very high and the stress is less than limit of surrendering, every performance of the steel is steady, and have nothing to do with stress state , time and temperature. Line bloated coefficient of steel and concrete line bloated coefficient difference very light, take place little internal stress very only between the two while changing in temperature. Because elastic mould amount of steel concrete elastic mould 7~15 of quantity, reach as interior concrete stress tensile strength and when fracturing, the stress of the reinforcing bar will not exceed 10000kg/cm2. . So is it is it prevent tiny appearance difficulty very much of crack from to make use of reinforcing bar to want among concrete. But the crack in the structure generally becomes numerous, the interval is little, the width and depth are smaller after adding the muscle. And if diameter of reinforcing bar detailed and when interval dense, to improve concrete resist result of person who split better. Concrete and surface , armored concrete of structure can take place detailed and shallow crack often, among them the great majority belong to and do and draw back the crack. Though this kind of crack is generally all relatively light, it stills have certain influence on the intensity and durability of the structure.
In order to guarantee concrete project quality , prevent fracturing , improve the durability of the concrete, use the admixture to reduce one of the measures that fractures correctly. Whether is it reduce water is it split pharmaceutical to defend , I summarize his main function in practice to use.
(1)There is pore Dao of a large number of mao in the concrete , produce capillary tension in the capillary after water is evaporated, make concrete is it contract out of shape to do. Increasing the thin aperture of hair can reduce the capillary surface tension , but will make the intensity of concrete reduce . This surface tension theory has already been confirmed in the world as far back as the sixties.
(2)Water dust than influence important factor that concrete shrink, is it reduce water is it split pharmaceutical can make concrete water consumption reduce by 25% to defend to use.
(3)Cement consumption important factor, concrete of person who shrink too, is it add and subtract water is it split concrete reducible 15% of the cement consumption on terms that keep the intensity of concrete of pharmaceutical to defend to mix, its volume is supplemented by increasing aggregate consumption.
(4)Reduce water is it split pharmaceutical can improve consistency of grout , reduce concrete secrete ink to defend, reduce and sink and draw back deforming.
(5)Improve glueing the strength of forming of the grout and aggregate, the concrete improved resists the performance of splitting.
(6)Concrete is it produce stress of drawing to restrain from while shrinking, crack when drawing the stress and is greater than concrete tensile strength can produce. Reduce water is it split pharmaceutical effective concrete tensile strength of improvement very to defend , improve resisting the performance of splitting of concrete by a wide margin.
(7)It can make the concrete density good to add the admixture to mix , can improve
resisting carbonization of concrete effectively , reduce carbonization to shrink.
(8)Is it reduce water is it split slow coagulation time proper concrete under pharmaceutical to defend , on the basis of preventing the fast water of cement from sending out heat effectively to mix, prevent the plasticity shrink that brings because the cement is not congealed for a long time from increasing.
(9)Mix admixture concrete and getting easy and kind , surface easy to feel flat , form little membrane, reduce the moisture to evaporate, reduce drily and shrink. A lot of admixture all have the functions of slow coagulation , increasing and apt , improvement plasticity, the experiment that we should carry on in this respect more in the project practice is compared with and studied, than lean against not improving terms more simple,may getting simple and more direct, economy.
Early maintenance of 4 concrete
Practice has proved , the common crack of concrete , most is the surface crack of different depth, main reason its whether temperature gradient cause cold temperature of area lower too easy to form crack suddenly. So say the warm - keeping of the concrete is especially important to preventing the early crack of surface.
From the viewpoint of temperature stress, should reach and require to keep warm followingly:
1)Prevent concrete internal and external temperature poor and concrete surface gradient from , prevent the surface crack.
2)Prevent concrete from to be ultra and cold , should is it is it make the minimum temperature is not lower than the steady temperature of concrete service time construction time in concrete to try to try one's best.
3)Prevent the old concrete subcooling , in order to reduce the restraint among the old and new concrete.
The early maintenance of the concrete, the main purpose lies in keeping the suitable warm and humid condition , in order to get the result of two respects, on the other hand make the concrete avoid the invasion and attack of the unfavorable and warm , humidity out of shape, the ones that prevent from harmfully are cold to contract and do to contract. On one hand make cement water function go on smoothly , is in the hope of reaching the intensity designed and resisting the ability of splitting.
The suitable warm damp condition is interrelated. Mix warm - keeping measure paid to congeal often protect wet results too. Analyse , water concrete include moisture can meet demand , cement of water have enough and to spare newly theoretically. But because the reason of evaporating etc. often causes losses of the moisture, thus postpone or hinder water of the cement from, the surface concrete receives this kind of adverse effect easiestly and directly. Key period when maintained in initial a few days after so the concrete is built, should pay attention to conscientiously in constructing.
Conclusions
Construction temperature and relation of crack in concrete the above carry on preliminary discussion of theory and practice, though the academia has different theories to origin cause of formation and computing technology of the concrete crack, but to concrete prevention and improving the measure suggestion to relatively unify , application in practice result fine too at the same time, concrete to is it observe , compare more more by us to want in constructing, analyse more , summarize more after going wrong ,
combine many kinds of prevention and deal with the measure, the crack of the concrete can be avoided.
2.Quality control of waterproof concrete construction
Combined with experience, from formwork design, fabrication and installation, assembing reinforoement, pouring and curing of concrete and other aspects construction technology of fair-faced concrete is introduced as well as quality control measures and standards in order to reduce engineering cost to acquire satisfied economic and social benefits.
The factors of influening waterproof- concrete quality are very many
Any links does not pay attention to the water-proof concrete of field loss hinders the water function without exception jointly with degree.Engineering construction in the basement adopts secondary form board fabrication and installation, reinforced bar fabrication and bind, concrete stirring and mixing system and transport, concrete concrete covibration beat with a stick, construction joint practice, concrete curing and dismantle model and beingready for backfill and so on aspects.These are very critical to quality method to ensure that water-proof concrete self water-proof, and the way of practice has wan out.
Method being under construction
2.1 Fabrication and Installation
According to the concrett of closely knit , demand of reason why to form board since the water-proof also concrete have made and have assembled corresponding rise is special , be to require that not leaving out thick fluid , firm closely knit block of wood deformation , water absorption Character should be small and ought to give priority to select and using bamboo slab rubber form board or the steel form.. Strict control form board room gap size, necessary exceeding 2 mms uses foam rubber or plastic to squeeze a crack in , porous form board nonutility without exception to board face Be ready for wall post at the same time rotting the prevention and cure job Adopt the cement mortar pouring same ,indicia in before the root segment sticking the foam rubber or plastic strip , the bottom puts on a cement mortar , concrete a concrete, first 5 cm ~ 10 cm. Since water-proof, concrete structure wall thickness is mostly more infertile .Be to ensure that component geometry dimension , Chang adopt the inside and outside bolt to pull the measure meeting attention to, responds to on play receive bolt centre interpose stop water iron plate, to prevent water from forming pilotage passage along bolt leakage.
2.2 Assembing reinforoement
Water-proof concrete structure has demanding as follows to the reinforced bar 1) reinforced bar should adopt twisted steel as far as possible , increases by hold wrap a force composing in reply a water ability
2) reinforced bars connect should try one's best to adopt to solder connection , stop using and being needless to bind connection to the full
3) when binding a reinforced bar, the iron wire head responds to inner bending.
4) strict control reinforced bars protective layer thickness.
Minimal thickness of water-proof concrete reinforced bar protective layer is
not smaller than 25 mms , the protective layer welcoming water surface especially inadmissibility to disappoint error,
. The iron wire and reinforced bar that application buries in advance within mortar piece while
using mortar heel block as protective layer, are bound
solid .When the cavalry puts up the fixed reinforced bar if adopt a reinforced bar, Ying Jia also solders water iron plate or fixation just goes ahead, to strengthen water-proof effect in the
heel block.This project uses new materials nylon to have fixed there is an effect's had guarded against reinforced bar protective layer deviation piece big mass common failings.
The concrete stirring and mixing makes and transports
Since the water-proof concrete requires that higher closely knit , reason why stir and mix system also need to have the fairly good homogeneity , should be ready for burning as follows almost for this purpose
1) ensures that mixing time , mixing at every time are secondary jump into a expect the general ejection of compact block of wood less than 2 mins.
2) should use the apposition agent , the solution queen who should manufacture certain thickness from apposition agent adds the mixer inner, the dried powder or high concentration solution will add an agent extra not to adds the mixer inner directly ,prevent from mixing is uneven but part
concentrates, both lose the apposition agent effect, and affect concrete mass.
3) responds to the assured source of life degree having a spot test on the admeasurement concrete at the regular intervals collapsing in the process being under construction , construction is middle
if Yu rains or other cause, respond to the ratio determining whose water ratio, and adjusting the composition being under construction in time when change happened in sandstone moisture content.
4) project uses the commodity concrete , has boundary have raised a concrete stirring mass and of all kinds effect apposition agent adulterating falls when amounts , the water ash having controlled a concrete strictly collapsing.
5) concretes concrete adopt a pump to have given handicraft , effective avoiding
a concrete producing the phenomenon isolating Mi Shui and leaving out thick fluid in the
process of transportation.
2.4 Matters needing attention in being under construction
1) construction school assignment soft and floury is divided .Water-proof concreting should stratify strictly being in progress, and a continuous construction iscompletedThe front and back and high and low connect between the tier should subjugate within the cement initial setting
time，For this purpose ,with handling a worker dividing into several, at the same time each other, school assignment group faces or it is all right for each other, carry on the back .
2)Achieve strictly fixed point determines the amounts of the components of a substance material down According to the vehicle capacities stratifying concrete
altitude and the means of transport, the quantify carrying out fixed point strictly is able to go down one important ring expecting that this is to improve water-proof concreting mass.
3) insist that you go down material opening the door or use string to expect that under barrel (chute)Be to prevent a cement paste from parting from aggregate for , to expect that liberty should not exceed 1.5 ms now and then highly under water-proof concrete。The water-proof structure reinforced bar is concentrated Should concrete altitude when higher , respond to according to the material stipulating that you go down material opening the door on form board or using string of barrels (chute) to fall, prevent a cement paste from parting from aggregate for , avoid at the
same time also the cement paste or the concrete
accumulating the place and cement paste alternating in the reinforced bar loosely splashing sticky Yu form board with outsideNow that material is difficult under bringing about a later, the surface affecting structure glossy , becomes in the future leakage hidden trouble.
4) concretes vibrating beat one important ring being to ensure that the concrete is closely knit , defend against to seep with a stick. Also, should adopt fixed point vibrating , handle meticulously on basis expecting that under determining the amounts of the components of a substance homogeneously in fixed point .Pay attention to high and low tier of linking up
Now that needing to prevent from miss and vibrating , not vibrating enough , being going to prevent a fault from vibrating again, Need to forbid using prying the method coming to aid to vibrate moving a reinforced bar or shaking a reinforced bar especially, such separates to making the front already concrete the reinforced bar and concrete shaking the reality part , causes serious consequences.
5) being ready for the assured source of life degree taking over thick fluid measure , adjusting in time to collapse seriously .Average water-proof concrete structure construction, the construction joint being under construction respectively , composing namely on erecting wall sells be bottom board and vertical wall at reduced prices.Should irrigate thick a layer of 5 cm ~ 10 cms surname indicia cement mortars in seam place first linking up closely knitting tier, in order to ensuring that the seam place vibrates when concrete vertical wall.Simultaneous , improve step by step with concrete an altitude'.Should fall off step by step with the water yield , diminish collapsing to fall degree prevent from concrete insist to be short but the cement paste is partial to much phenomenon to aggregate appearing on upper part.
2.5 The method of Construction joint
The construction joint is one of water-proof architectural weak link. The construction joint is one of water-proof architectural weak link. Should stop staying or not staying to the full. equipment or props up conditional restricting of model, may then behind the agreement
collecting a design organ, on the wall stipulating that lienable level of location construction joint , sort keep vertical strokes getting along in all above 200 bottom board .Adopt new handicraft expansibility in the project rubber water just brings
handling the construction joint method , substituting method in common use , anxiously expecting the dyadic construction joint of mouth , at any rate dyadic construction joint , flat mouth construction joint such as and so on .Water proofing is in no lienable construction joint of perpendicularity direction like the concrete , rubber stops in having set up the construction joint irrigating belt , perpendicularity directionthe day afer tomorrow between the main building and the skirt building interposing expansibility in seam location water belt or steel plate stops water belt.weak link of water-proof structure, respond to specially-assigned person conscientiously , handle meticulously . Ensure mass to be under construction in construction. Adopt to stop having not to miss and not soldering time water steel plate, adopt rubber water belt just should be solid without fail reliably in receiving long time will
connect using special use glue to paste. When only think that concreting accepts 2.6 Dismantling model and curing of concrete
The water-proof concreting queen maintains goodness and badness working, not only affecting
the intensity arriving at a concrete, moreover the impervious function affecting to the concrete. Evidence , water-proof concrete early phase dehydration or curing process lack for water , will reduce whose impervious function by a wide margin. Water-proof concrete curing
responds to the block of wood less than 14 ds.
The water-proof concrete dismantles a model demanding to be unable to compare high , dismantle model time unsuitable untimely, respond to when dismantling a model handle meticulously , prevent an iron rod from using to pry, stiffly, that the sledgehammer is knocked suddenly
and forcibly pries , uses a concrete meet with destroy
2.7 Do good well at backfill
Water-proof architectural backfill is a final working procedure , it be sometimes ignored , this is a very big faults in fact under the ground.When the water-proof structure job is over queen responds to the construction carrying out backfill immediately.Most important ,we should take backfill seriously self mass; Secondly, backfill varia and ponding should clear up the pit bottom in the front , respond to densification with layers when backfill. Water-proof structure vicinity layer pounds true backfill , self is a reliable and economical as well water proofing drapery under the ground. In project basement engineering construction Shanghai,since organizing water proofing down to earth strictly with all above seven passes, the concrete is under construction , effect is comparatively ideal.The percolating water phenomenon does not appear.
Conclusions
Construction temperature and relation of crack in concrete the above carry on preliminary discussion of theory and practice, though the academia has different theories to origin cause of formation and computing technology of the concrete crack, but to concrete prevention and improving the measure suggestion to relatively unify , application in practice result fine too at the same time, concrete to is it observe , compare more more
by us to want in constructing, analyse more , summarize more after going wrong , combine many kinds of prevention and deal with the measure, the crack of the concrete can be avoided.
浅谈混凝土的施工过程中温度与裂缝控制
By G. K. Kululanga, W. Kuotcha, R. McCaffer, Member, ASCE, and F. Edum-Fotwe
美国土木工程师学会
摘要为了防止业主对混凝土工程的索赔,就必须做好施工过程中温度与裂缝控制。本文通过多年的现场观察，通过查阅有关混凝土内部应力方面的专著，对混凝土温度裂缝产生的原因、现场混凝土温度的控制和预防裂缝的措施进行等进行阐述。
关键词：混凝土；温度应力；裂缝；控制
混凝土在现代工程建设中占有重要地位。而在今天，混凝土的裂缝较为普遍，在桥梁工程中裂缝几乎无所不在。尽管我们在施工中采取各种措施，小心谨慎，但裂缝仍然时有出现。究其原因，我们对混凝土温度应力的变化注意不够是其中之一。
在大体积混凝土中，温度应力及温度控制具有重要意义。这主要是由于两方面的原因。首先，在施工中混凝土常常出现温度裂缝，影响到结构的整体性和耐久性。其次，在运转过程中，温度变化对结构的应力状态具有显著的不容忽视的影响。我们遇到的主要是施工中的温度裂缝，因此本文仅对施工中混凝土裂缝的成因和处理措施做一探讨。
1、裂缝的原因
混凝土中产生裂缝有多种原因，主要是温度和湿度的变化，混凝土的脆性和不均匀性，以及结构不合理，原材料不合格（如碱骨料反应），模板变形，基础不均匀沉降等。
混凝土硬化期间水泥放出大量水化热，内部温度不断上升，在表面引起拉应力。后期在降温过程中，由于受到基础或老混凝上的约束，又会在混凝土内部出现拉应力。气温的降低也会在混凝土表面引起很大的拉应力。当这些拉应力超出混凝土的抗裂能力时，即会出现裂缝。许多混凝土的内部湿度变化很小或变化较慢，但表面湿度可能变化较大或发生剧烈变化。如养护不周、时干时湿，表面干缩形变受到内部混凝土的约束，也往往导致裂缝。混凝土是一种脆性材料，抗拉强度是抗压强度的1／10左右，短期加荷时的极限拉伸变形只有（0.6～1.0）×104，长期加荷时的极限位伸变形也只有（1.2～2.0）×104.由于原材料不均匀，水灰比不稳定，及运输和浇筑过程中的离析现象，在同一块混凝土中其抗拉强度又是不均匀的，存在着许多抗拉能力很低，易于出现裂缝的薄弱部位。在钢筋混
凝土中，拉应力主要是由钢筋承担，混凝土只是承受压应力。在素混凝土内或钢筋混凝上的边缘部位如果结构内出现了拉应力，则须依靠混凝土自身承担。一般设计中均要求不出现拉应力或者只出现很小的拉应力。但是在施工中混凝土由最高温度冷却到运转时期的稳定温度，往往在混凝土内部引起相当大的拉应力。有时温度应力可超过其它外荷载所引起的应力，因此掌握温度应力的变化规律对于进行合理的结构设计和施工极为重要。
2、温度应力的分析
根据温度应力的形成过程可分为以下三个阶段：
（1）早期：自浇筑混凝土开始至水泥放热基本结束，一般约30天。这个阶段的两个特征，一是水泥放出大量的水化热，二是混凝上弹性模量的急剧变化。由于弹性模量的变化，这一时期在混凝土内形成残余应力。
（2）中期：自水泥放热作用基本结束时起至混凝土冷却到稳定温度时止，这个时期中，温度应力主要是由于混凝土的冷却及外界气温变化所引起，这些应力与早期形成的残余应力相叠加，在此期间混凝上的弹性模量变化不大。
（3）晚期：混凝土完全冷却以后的运转时期。温度应力主要是外界气温变化所引起，这些应力与前两种的残余应力相迭加。
根据温度应力引起的原因可分为两类：
（1）自生应力：边界上没有任何约束或完全静止的结构，如果内部温度是非线性分布的，由于结构本身互相约束而出现的温度应力。例如，桥梁墩身，结构尺寸相对较大，混凝土冷却时表面温度低，内部温度高，在表面出现拉应力，在中间出现压应力。
（2）约束应力：结构的全部或部分边界受到外界的约束，不能自由变形而引起的应力。如箱梁顶板混凝土和护栏混凝土。
这两种温度应力往往和混凝土的干缩所引起的应力共同作用。
要想根据已知的温度准确分析出温度应力的分布、大小是一项比较复杂的工作。在大多数情况下，需要依靠模型试验或数值计算。混凝土的徐变使温度应力有相当大的松驰，计算温度应力时，必须考虑徐变的影响，具体计算这里就不再细述。
3、温度的控制和防止裂缝的措施
为了防止裂缝，减轻温度应力可以从控制温度和改善约束条件两个方面着手。
控制温度的措施如下：
（1）采用改善骨料级配，用干硬性混凝土，掺混合料，加引气剂或塑化剂等措施以减少混凝土中的水泥用量；
（2）拌合混凝土时加水或用水将碎石冷却以降低混凝土的浇筑温度；
（3）热天浇筑混凝土时减少浇筑厚度，利用浇筑层面散热；
（4）在混凝土中埋设水管，通入冷水降温；
（5）规定合理的拆模时间，气温骤降时进行表面保温，以免混凝土表面发生急剧的温度梯度；
（6）施工中长期暴露的混凝土浇筑块表面或薄壁结构，在寒冷季节采取保温措施；
改善约束条件的措施是：
（1）合理地分缝分块；
（2）避免基础过大起伏；
（3）合理的安排施工工序，避免过大的高差和侧面长期暴露；
此外，改善混凝土的性能，提高抗裂能力，加强养护，防止表面干缩，特别是保证混凝土的质量对防止裂缝是十分重要，应特别注意避免产生贯穿裂缝，出现后要恢复其结构的整体性是十分困难的，因此施工中应以预防贯穿性裂缝的发生为主。
在混凝土的施工中，为了提高模板的周转率，往往要求新浇筑的混凝土尽早拆模。当混凝土温度高于气温时应适当考虑拆模时间，以免引起混凝土表面的早期裂缝。新浇筑早期拆模，在表面引起很大的拉应力，出现“温度冲击”现象。在混凝土浇筑初期，由于水化热的散发，表面引起相当大的拉应力，此时表面温度亦较气温为高，此时拆除模板，表面温度骤降，必然引起温度梯度，从而在表面附加一拉应力，与水化热应力迭加，再加上混凝土干缩，表面的拉应力达到很大的数值，就有导致裂缝的危险，但如果在拆除模板后及时在表面覆盖一轻型保温材料，如泡沫海棉等，对于防止混凝土表面产生过大的拉应力，具有显著的效果。
加筋对大体积混凝土的温度应力影响很小，因为大体积混凝土的含筋率极低。只是对一般钢筋混凝土有影响。在温度不太高及应力低于屈服极限的条件下，钢的各项性能是稳定的，而与应力状态、时间及温度无关。钢的线胀系数与混凝土线胀系数相差很小，在温度变化时两者间只发生很小的内应力。由于钢的弹性模量为混凝土弹性模量的7~15倍，当内混凝土应力达到抗拉强度而开裂时，钢筋的应力将不超过100~200kg／cm2..因此，在混凝土中想要利用钢筋来防止细小裂缝的出现很困难。但加筋后结构内的裂缝一般就变得数目多、间距小、宽度与深度较小了。而且如果钢筋的直径细而间距密时，对提高混凝土抗裂性的效果较好。混凝土和钢筋混凝土结构的表面常常会发生细而浅的裂缝，其中大多数属于干缩裂缝。虽然这种裂缝一般都较浅，但它对结构的强度和耐久性仍有一定的影响。
为保证混凝土工程质量，防止开裂，提高混凝土的耐久性，正确使用外加剂
也是减少开裂的措施之一。例如使用减水防裂剂，笔者在实践中总结出其主要作用为：
（1）混凝土中存在大量毛细孔道，水蒸发后毛细管中产生毛细管张力，使混凝土干缩变形。增大毛细孔径可降低毛细管表面张力，但会使混凝土强度降低。这个表面张力理论早在六十年代就已被国际上所确认。
（2）水灰比是影响混凝土收缩的重要因素，使用减水防裂剂可使混凝土用水量减少25％。
（3）水泥用量也是混凝土收缩率的重要因素，掺加减水防裂剂的混凝土在保持混凝土强度的条件下可减少15％的水泥用量，其体积用增加骨料用量来补充。
（4）减水防裂剂可以改善水泥浆的稠度，减少混凝土泌水，减少沉缩变形。
（5）提高水泥浆与骨料的粘结力，提高的混凝土抗裂性能。
（6）混凝土在收缩时受到约束产生拉应力，当拉应力大于混凝土抗拉强度时裂缝就会产生。减水防裂剂可有效的提高的混凝土抗拉强度，大幅提高混凝土的抗裂性能。
（7）掺加外加剂可使混凝土密实性好，可有效地提高混凝土的抗碳化性，减少碳化收缩。
（8）掺减水防裂剂后混凝土缓凝时间适当，在有效防止水泥迅速水化放热基础上，避免因水泥长期不凝而带来的塑性收缩增加。
（9）掺外加剂混凝土和易性好，表面易抹平，形成微膜，减少水分蒸发，减少干燥收缩.
许多外加剂都有缓凝、增加和易性、改善塑性的功能，我们在工程实践中应多进行这方面的实验对比和研究，比单纯的靠改善外部条件，可能会更加简捷、经济。
4、混凝土的早期养护
实践证明，混凝土常见的裂缝，大多数是不同深度的表面裂缝，其主要原因是温度梯度造成寒冷地区的温度骤降也容易形成裂缝。因此说混凝土的保温对防止表面早期裂缝尤其重要。从温度应力观点出发，保温应达到下述要求：1）防止混凝土内外温度差及混凝土表面梯度，防止表面裂缝。2）防止混凝土超冷，应该尽量设法使混凝土的施工期最低温度不低于混凝土使用期的稳定温度。3）防止老混凝土过冷，以减少新老混凝土间的约束。
混凝土的早期养护，主要目的在于保持适宜的温湿条件，以达到两个方面的效果，一方面使混凝土免受不利温、湿度变形的侵袭，防止有害的冷缩和干缩。一方面使水泥水化作用顺利进行，以期达到设计的强度和抗裂能力。
适宜的温湿度条件是相互关联的。混凝上的保温措施常常也有保湿的效果。
从理论上分析，新浇混凝土中所含水分完全可以满足水泥水化的要求而有余。但由于蒸发等原因常引起水分损失，从而推迟或妨碍水泥的水化，表面混凝土最容易而且直接受到这种不利影响。因此混凝土浇筑后的最初几天是养护的关键时期，在施工中应切实重视起来。
2.防水混凝土施工质量控制
结合经验，对模板的设计、制作安装、钢筋绑扎、混凝土浇筑及养护等关键工序的操作要点进行了阐述，并介绍了成型后混凝土的质量控制标准，以降低工程造价，具有很好的经济和社会效益。
影响防水混凝土的质量因素很多。任何一个环节不注意均会不同程度地损失防水混凝土阻水功能，在地下室工程施工中，采取了从模板制作与安装、钢筋制作与绑扎、混凝土的拌制和运输、混凝土的浇筑和振捣、施工缝作法、混凝土的养护与拆模以及做好回填土等方面严把质量关方法确保防水混凝土自防水，并通过实践获得成功。
施工方法
2．1 模板制作与安装
由于防水混凝土特别强调密实性，所以对模板的制作和安装也相应提高了要求，即要求密实不漏浆，坚固不变形，吸水性要小，宜优先选用竹胶板模板或钢模板。严格控制模板间的缝隙大小，超过 2 mm的必须用海绵条塞缝，对于板面多孔的模板一律不用，同时做好墙柱烂根防治工作，采取根部贴海绵条，底部抹水泥砂浆，浇筑混凝土前，先注入同标号的水泥砂浆由于防水混凝土结构壁厚大多较薄，为保证构件的几何尺寸，常采用内外螺栓拉接的措施，需要注意的是，应在拉接螺栓中间设置止水铁板，以防止水沿着螺栓渗漏，形成引水通路。
2．2 钢筋制作与绑扎
防水混凝土结构对钢筋有如下要求：
1)钢筋应尽可能采用螺纹钢筋，增加握裹力和止水能力。
2)钢筋接头应尽量采用焊接接头，尽量少用和不用绑扎接头。
4)严格控制钢筋保护层厚度。
防水混凝土钢筋保护层最小厚度不小于25 mm，特别是迎水面的保护层不允许有负误差，用砂浆垫块作保护层时，应用预埋在砂浆块内的铁丝与钢筋绑扎牢
固。若采用钢筋铁马架固定钢筋时，也应加焊止水铁板或固定在垫块上，以增强防水效果,本工程用新型材料尼龙固定片有效的防止了钢筋保护层偏差过大的质量通病。
2.3混凝土的拌制和运输
由于防水混凝土要求较高的密实性，所以拌制也要有较好的均匀性，为此应做好如下几点：
1)确保搅拌时间，每次搅拌从投料到出料一般不少于 2 min。
2)当使用外加剂，应将外加剂制成一定浓度的溶液后加入搅拌机内，不得将外加剂的干粉或高浓度溶液直接加入搅拌机内，防止搅拌不均匀而局部集中，既失去外加剂作用，又影响混凝土质量。
3)施工过程中应定期抽查测定混凝土坍落度，施工中如遇下
雨或其他原因，砂石含水量发生变化时，应及时测定其含水率，并
调整施工配合比。
4)本工程使用商品混凝土，有效的提高了混凝土搅拌质量及各类外加剂的掺量，严格控制了混凝土水灰比及坍落度。
5)混凝土的浇筑采用泵送工艺，有效的避免了混凝土在运输过程中产生离析泌水及漏浆现象。
2．4 施工中的注意事项
1)施工作业面的合理划分。防水混凝土浇筑应严格分层进行，并一次连续施工完成前后及上下层之间接头应严格控制在水泥的初凝时间内为此，可将操作工人分成几个作业组同时相向或相背而行。
2)严格做到定点定量下料。根据分层浇筑高度和运输工具的车容量，严格进行定点定量方可下料，这是提高防水混凝土浇筑质量的重要一环。
3)坚持开门子下料或用串桶(溜槽)下料。
为防止水泥浆与骨料分离，防水混凝土下料时自由高度应不超过防水结构钢筋密集，当浇筑高度较高时，应按规定在模板上开门子下料或用串桶(溜槽)下料，防止水泥浆与骨料分离，同时也避免水泥浆或混凝土松散地堆积于钢筋交叉处和水泥浆溅粘于模板表面，既造成后面下料困难，又影响结构表面光滑，成为日后渗漏隐患。
4)混凝土的振捣是保证混凝土密实、防渗的重要一环，点定量均匀下料的基础上，也应采取定点振捣，精心操作注意上下层的衔接，既要防止漏振、欠振，又要防止过振，特别要禁止用撬动钢筋或振动钢筋来助振的方法，这样将使前面已浇筑振实部分的钢筋与混凝土分离，造成严重后果。
5)认真做好接浆措施，及时调整坍落度。
防水混凝土结构施工中，常常是底板与竖壁分别施工，即在竖壁上做施工缝处理。在浇筑竖壁时应在接缝处先浇一层 5cm～10 cm厚的同标号水泥砂浆衔接层，以保证接缝处振捣密实。同时，随着浇筑高度的逐步提高，应逐步减少用水量，减小坍落度防止浇筑到上部出现骨料偏少而水泥浆偏多现象。
2．5 施工缝作法
施工缝是防水结构的薄弱环节之一。应尽量少留或不留，当混凝土浇筑受到设备或支模条件的限制时，则可在征得设计单位的同意后，在规定部位留置水平施工缝，一般留在底板以上200 mm处的竖壁上工程中采用新工艺——膨胀性橡胶止水带处理施工缝的方法，取代常用方法，诸如企口式施工缝、高低式施工缝、平口施工缝等。防水混凝土一般在垂直方向不留置施工缝，在主楼与裙楼之间设了后浇带，垂直方向的施工缝在接缝部位设置膨胀性橡胶止水带或钢板止水带。由于施工缝是防水结构的一个薄弱环节，施工中应专人负责，精心操作，确保施工质量。采用止水钢板时不得有漏焊，采用橡胶止水带在接长时务必要将接头用专用胶水粘贴牢固可靠。
2．6 混凝土的养护与拆模
防水混凝土浇筑后养护工作的好坏，不仅影响到混凝土的强度，而且影响到混凝土的抗渗性能。试验证明，防水混凝土早期脱水或养护过程缺水，将大幅度降低其抗渗性能。防水混凝土养护应不少于 14 d防水混凝土拆模要求也比较高，拆模时间不宜过早，拆模时应精心操作，防止用铁棍撬，大锤猛敲硬撬，使混凝土遭到破坏。
2．7 做好回填土
地下防水结构的回填土是最后一道工序，它往往被忽视，这实在是一个很大的失误。当构筑物防水工作结束后应立即进行回填土施工。首先应重视回填土本身的质量；其次回填前应清理坑底的杂物和积水，回填时应分层夯实。地下防
水结构周围一层夯实的回填土，本身是一道可靠而又经济的防水帷幕。在工程地下室工程施工申，由于切切实实严把以上七道关口，组织防水混凝土施工，效果比较理想，没有出现渗漏水现象。
结束语
以上对混凝土的施工温度与裂缝之间的关系进行了理论和实践上的初步探讨，虽然学术界对于混凝土裂缝的成因和计算方法有不同的理论，但对于具体的预防和改善措施意见还是比较统一，同时在实践中的应用效果也是比较好的，具体施工中要靠我们多观察、多比较，出现问题后多分析、多总结，结合多种预防处理措施，混凝土的裂缝是完全可以避免的。
参考书目（略）：
外文翻译 专业机械设计制造及其自动化学生姓名刘链柱 班级机制111 学号1110101102 指导教师葛友华
外文资料名称： Design and performance evaluation of vacuum cleaners using cyclone technology 外文资料出处：Korean J. Chem. Eng., 23(6), (用外文写) 925-930 (2006) 附件： 1.外文资料翻译译文 2.外文原文
应用旋风技术真空吸尘器的设计和性能介绍 吉尔泰金，洪城铱昌，宰瑾李， 刘链柱译 摘要：旋风型分离器技术用于真空吸尘器 - 轴向进流旋风和切向进气道流旋风有效地收集粉尘和降低压力降已被实验研究。优化设计等因素作为集尘效率，压降，并切成尺寸被粒度对应于分级收集的50％的效率进行了研究。颗粒切成大小降低入口面积，体直径，减小涡取景器直径的旋风。切向入口的双流量气旋具有良好的性能考虑的350毫米汞柱的低压降和为1.5μm的质量中位直径在1米3的流量的截止尺寸。一使用切向入口的双流量旋风吸尘器示出了势是一种有效的方法，用于收集在家庭中产生的粉尘。 摘要及关键词：吸尘器; 粉尘; 旋风分离器 引言 我们这个时代的很大一部分都花在了房子，工作场所，或其他建筑，因此，室内空间应该是既舒适情绪和卫生。但室内空气中含有超过室外空气因气密性的二次污染物，毒物，食品气味。这是通过使用产生在建筑中的新材料和设备。真空吸尘器为代表的家电去除有害物质从地板到地毯所用的商用真空吸尘器房子由纸过滤，预过滤器和排气过滤器通过洁净的空气排放到大气中。虽然真空吸尘器是方便在使用中，吸入压力下降说唱空转成比例地清洗的时间，以及纸过滤器也应定期更换，由于压力下降，气味和细菌通过纸过滤器内的残留粉尘。 图1示出了大气气溶胶的粒度分布通常是双峰形，在粗颗粒（>2.0微米）模式为主要的外部来源，如风吹尘，海盐喷雾，火山，从工厂直接排放和车辆废气排放，以及那些在细颗粒模式包括燃烧或光化学反应。表1显示模式，典型的大气航空的直径和质量浓度溶胶被许多研究者测量。精细模式在0.18?0.36 在5.7到25微米尺寸范围微米尺寸范围。质量浓度为2?205微克，可直接在大气气溶胶和 3.85至36.3μg/m3柴油气溶胶。
第一课 土木工程学土木工程学作为最老的工程技术学科，是指规划，设计，施工及对建筑环境的管理。此处的环境包括建筑符合科学规范的所有结构，从灌溉和排水系统到火箭发射设施。 土木工程师建造道路，桥梁，管道，大坝，海港，发电厂，给排水系统，医院，学校，公共交通和其他现代社会和大量人口集中地区的基础公共设施。他们也建造私有设施，比如飞机场，铁路，管线，摩天大楼，以及其他设计用作工业，商业和住宅途径的大型结构。此外，土木工程师还规划设计及建造完整的城市和乡镇，并且最近一直在规划设计容纳设施齐全的社区的空间平台。 土木一词来源于拉丁文词“公民”。在1782年，英国人John Smeaton为了把他的非军事工程工作区别于当时占优势地位的军事工程师的工作而采用的名词。自从那时起，土木工程学被用于提及从事公共设施建设的工程师，尽管其包含的领域更为广阔。 领域。因为包含范围太广，土木工程学又被细分为大量的技术专业。不同类型的工程需要多种不同土木工程专业技术。一个项目开始的时候，土木工程师要对场地进行测绘，定位有用的布置，如地下水水位，下水道，和电力线。岩土工程专家则进行土力学试验以确定土壤能否承受工程荷载。环境工程专家研究工程对当地的影响，包括对空气和地下水的可能污染，对当地动植物生活的影响，以及如何让工程设计满足政府针对环境保护的需要。交通工程专家确定必需的不同种类设施以减轻由整个工程造成的对当地公路和其他交通网络的负担。同时，结构工程专家利用初步数据对工程作详细规划，设计和说明。从项目开始到结束，对这些土木工程专家的工作进行监督和调配的则是施工管理专家。根据其他专家所提供的信息，施工管理专家计算材料和人工的数量和花费，所有工作的进度表，订购工作所需要的材料和设备，雇佣承包商和分包商，还要做些额外的监督工作以确保工程能按时按质完成。 贯穿任何给定项目，土木工程师都需要大量使用计算机。计算机用于设计工程中使用的多数元件（即计算机辅助设计，或者CAD）并对其进行管理。计算机成为了现代土木工程师的必备品，因为它使得工程师能有效地掌控所需的大量数据从而确定建造一项工程的最佳方法。 结构工程学。在这一专业领域，土木工程师规划设计各种类型的结构，包括桥梁，大坝，发电厂，设备支撑，海面上的特殊结构，美国太空计划，发射塔，庞大的天文和无线电望远镜，以及许多其他种类的项目。结构工程师应用计算机确定一个结构必须承受的力：自重，风荷载和飓风荷载，建筑材料温度变化引起的胀缩，以及地震荷载。他们也需确定不同种材料如钢筋，混凝土，塑料，石头，沥青，砖，铝或其他建筑材料等的复合作用。 水利工程学。土木工程师在这一领域主要处理水的物理控制方面的种种问题。他们的项目用于帮助预防洪水灾害，提供城市用水和灌溉用水，管理控制河流和水流物，维护河滩及其他滨水设施。此外，他们设计和维护海港，运河与水闸，建造大型水利大坝与小型坝，以及各种类型的围堰，帮助设计海上结构并且确定结构的位置对航行影响。 岩土工程学。专业于这个领域的土木工程师对支撑结构并影响结构行为的土壤和岩石的特性进行分析。他们计算建筑和其他结构由于自重压力可能引起的沉降，并采取措施使之减少到最小。他们也需计算并确定如何加强斜坡和填充物的稳定性以及如何保护结构免受地震和地下水的影响。 环境工程学。在这一工程学分支中，土木工程师设计，建造并监视系统以提供安全的饮用水，同时预防和控制地表和地下水资源供给的污染。他们也设计，建造并监视工程以控制甚至消除对土地和空气的污染。他们建造供水和废水处理厂，设计空气净化器和其他设备以最小化甚至消除由工业加工、焚化及其他产烟生产活动引起的空气污染。他们也采用建造特殊倾倒地点或使用有毒有害物中和剂的措施来控制有毒有害废弃物。此外，工程师还对垃圾掩埋进行设计和管理以预防其对周围环境造成污染。
使用高级分析法的钢框架创新设计 1．导言 在美国，钢结构设计方法包括允许应力设计法(ASD)，塑性设计法(PD)和荷载阻力系数设计法(LRFD)。在允许应力设计中，应力计算基于一阶弹性分析，而几何非线性影响则隐含在细部设计方程中。在塑性设计中，结构分析中使用的是一阶塑性铰分析。塑性设计使整个结构体系的弹性力重新分配。尽管几何非线性和逐步高产效应并不在塑性设计之中，但它们近似细部设计方程。在荷载和阻力系数设计中，含放大系数的一阶弹性分析或单纯的二阶弹性分析被用于几何非线性分析，而梁柱的极限强度隐藏在互动设计方程。所有三个设计方法需要独立进行检查，包括系数K计算。在下面，对荷载抗力系数设计法的特点进行了简要介绍。 结构系统内的内力及稳定性和它的构件是相关的，但目前美国钢结构协会（AISC）的荷载抗力系数规范把这种分开来处理的。在目前的实际应用中，结构体系和它构件的相互影响反映在有效长度这一因素上。这一点在社会科学研究技术备忘录第五录摘录中有描述。 尽管结构最大内力和构件最大内力是相互依存的（但不一定共存），应当承认，严格考虑这种相互依存关系，很多结构是不实际的。与此同时，众所周知当遇到复杂框架设计中试图在柱设计时自动弥补整个结构的不稳定（例如通过调整柱的有效长度）是很困难的。因此，社会科学研究委员会建议在实际设计中，这两方面应单独考虑单独构件的稳定性和结构的基础及结构整体稳定性。图28.1就是这种方法的间接分析和设计方法。
在目前的美国钢结构协会荷载抗力系数规范中，分析结构体系的方法是一阶弹性分析或二阶弹性分析。在使用一阶弹性分析时，考虑到二阶效果，一阶力矩都是由B1,B2系数放大。在规范中，所有细部都是从结构体系中独立出来，他们通过细部内力曲线和规范给出的那些隐含二阶效应，非弹性，残余应力和挠度的相互作用设计的。理论解答和实验性数据的拟合曲线得到了柱曲线和梁曲线，同时Kanchanalai发现的所谓“精确”塑性区解决方案的拟合曲线确定了梁柱相互作用方程。 为了证明单个细部内力对整个结构体系的影响，使用了有效长度系数，如图28.2所示。有效长度方法为框架结构提供了一个良好的设计。然而，有效长度方法的
a common way to construct steel truss and prestressed concrete cantilever spans is to counterbalance each cantilever arm with another cantilever arm projecting the opposite direction,forming a balanced cantilever. they attach to a solid foundation ,the counterbalancing arms are called anchor arms /thus,in a bridge built on two foundation piers,there are four cantilever arms ,two which span the obstacle,and two anchor arms which extend away from the obstacle,because of the need for more strength at the balanced cantilever's supports ,the bridge superstructure often takes the form of towers above the foundation piers .the commodore barry bridge is an example of this type of cantilever bridge 一种常见的方法构造钢桁架和预应力混凝土悬臂跨度是每一个悬臂抗衡预测相反的方向臂悬臂，形成一个平衡的悬臂。他们重视了坚实的基础，制约武器被称为锚武器/因此，在两个基础上建一座桥桥墩，有四个悬臂式武器，这两者之间跨越的障碍，和两个锚武器哪个延长距离的障碍，因为为更多的在平衡悬臂的支持力量的需要，桥梁上部结构往往表现为塔墩基础之上形成的准将巴里大桥是这种类型的例子悬臂桥 steel truss cantilever support loads by tension of the upper members and compression of the lower ones .commonly ,the structure distributes teh tension via teh anchor arms to the outermost supports ,while the compression is carried to the foundation beneath teh central towers .many truss cantilever bridges use pinned joints and are therefore statically determinate with no members carrying mixed loads 钢桁架悬臂由上层成员和下层的紧张压缩支持负载。通常，结构分布通过锚武器的最外层的支持紧张，而压缩抬到下方的中央塔的基础。桁架悬臂许多桥梁使用固定的关节，是静定，没有携带混合负载的成员，因此 prestressed concrete balanced cantilever bridges are often built using segmental construction .some steel arch bridges are built using pure cantilever spans from each sides,with neither falsework below nor temporary supporting towers and cables above ,these are then joined with a pin,usually after forcing the union point apart ,and when jacks are removed and the bridge decking is added the bridge becomes a truss arch bridge .such unsupported construction is only possible where appropriate rock is available to support the tension in teh upper chord of the span during construction ,usually limiting this method to the spanning of narrow canyons 预应力混凝土平衡悬臂桥梁往往建立使用段施工。一些钢拱桥是使用各方面的纯悬臂跨度既无假工作下面也临时支撑塔和电缆上面，这些都是再加入了一根针，通常在迫使工会点外，当插孔删除，并添加桥梁甲板桥成为桁架拱桥，这种不支持的建设，才可能在适当情况下的岩石可用于支持在施工期间的跨度弦上的张力，通常限制这狭隘的峡谷跨越方法 an arch bridge is a bridge with abutments at each end shaped as a curved arch .arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side .a viaduct may be made from a series of arches ,although other more economical structures are typically used today 在拱桥桥台的桥梁，是一个在一个弧形拱状，每年年底。拱桥通过转移到由部分在两边的桥台水平推
第一部分必须掌握，第二部分尽量掌握 第一部分： 1 Finite Element Method 有限单元法 2 专业英语Specialty English 3 水利工程Hydraulic Engineering 4 土木工程Civil Engineering 5 地下工程Underground Engineering 6 岩土工程Geotechnical Engineering 7 道路工程Road (Highway) Engineering 8 桥梁工程Bridge Engineering 9 隧道工程Tunnel Engineering 10 工程力学Engineering Mechanics 11 交通工程Traffic Engineering 12 港口工程Port Engineering 13 安全性safety 17木结构timber structure 18 砌体结构masonry structure 19 混凝土结构concrete structure 20 钢结构steelstructure 21 钢-混凝土复合结构steel and concrete composite structure 22 素混凝土plain concrete 23 钢筋混凝土reinforced concrete 24 钢筋rebar 25 预应力混凝土pre-stressed concrete 26 静定结构statically determinate structure 27 超静定结构statically indeterminate structure 28 桁架结构truss structure 29 空间网架结构spatial grid structure 30 近海工程offshore engineering 31 静力学statics 32运动学kinematics 33 动力学dynamics 34 简支梁simply supported beam 35 固定支座fixed bearing 36弹性力学elasticity 37 塑性力学plasticity 38 弹塑性力学elaso-plasticity 39 断裂力学fracture Mechanics 40 土力学soil mechanics 41 水力学hydraulics 42 流体力学fluid mechanics 43 固体力学solid mechanics 44 集中力concentrated force 45 压力pressure 46 静水压力hydrostatic pressure 47 均布压力uniform pressure 48 体力body force 49 重力gravity 50 线荷载line load 51 弯矩bending moment 52 torque 扭矩53 应力stress 54 应变stain 55 正应力normal stress 56 剪应力shearing stress 57 主应力principal stress 58 变形deformation 59 内力internal force 60 偏移量挠度deflection 61 settlement 沉降 62 屈曲失稳buckle 63 轴力axial force 64 允许应力allowable stress 65 疲劳分析fatigue analysis 66 梁beam 67 壳shell 68 板plate 69 桥bridge 70 桩pile 71 主动土压力active earth pressure 72 被动土压力passive earth pressure 73 承载力load-bearing capacity 74 水位water Height 75 位移displacement 76 结构力学structural mechanics 77 材料力学material mechanics 78 经纬仪altometer 79 水准仪level 80 学科discipline 81 子学科sub-discipline 82 期刊journal ,periodical 83文献literature 84 ISSN International Standard Serial Number 国际标准刊号 85 ISBN International Standard Book Number 国际标准书号 86 卷volume 87 期number 88 专着monograph 89 会议论文集Proceeding 90 学位论文thesis, dissertation 91 专利patent 92 档案档案室archive 93 国际学术会议conference 94 导师advisor 95 学位论文答辩defense of thesis 96 博士研究生doctorate student 97 研究生postgraduate 98 EI Engineering Index 工程索引 99 SCI Science Citation Index 科学引文索引 100ISTP Index to Science and Technology Proceedings 科学技术会议论文集索引 101 题目title 102 摘要abstract 103 全文full-text 104 参考文献reference 105 联络单位、所属单位affiliation 106 主题词Subject 107 关键字keyword 108 ASCE American Society of Civil Engineers 美国土木工程师协会 109 FHWA Federal Highway Administration 联邦公路总署
(1)Concrete and reinforced concrete are used as building materials in every country. In many, including Canada and the United States, reinforced concrete is a dominant structural material in engineered construction. (1)混凝土和钢筋混凝土在每个国家都被用作建筑材料。在许多国家，包括加拿大和美国，钢筋混凝土是一种主要的工程结构材料。 (2)The universal nature of reinforced concrete construction stems from the wide availability of reinforcing bars and the constituents of concrete, gravel, sand, and cement, the relatively simple skills required in concrete construction. (2) 钢筋混凝土建筑的广泛存在是由于钢筋和制造混凝土的材料，包括石子，沙，水泥等，可以通过多种途径方便的得到，同时兴建混凝土建筑时所需要的技术也相对简单。 (3)Concrete and reinforced concrete are used in bridges, building of all sorts, underground structures, water tanks, television towers, offshore oil exploration and production structures, dams, and even in ships. (3)混凝土和钢筋混凝土被应用于桥梁，各种形式的建筑，地下结构，蓄水池，电视塔，海上石油平台，以及工业建筑，大坝，甚至船舶等。 (4)Reinforce concrete structures consist of a series of individual members that interact to support the loads placed on the structure. The floor of concrete buildings is often built of concrete joist-slab construction. (4)钢筋混凝土结构由一系列单独构件组成，这些构件通过相互作用共同抵抗施加在结构上的荷载。混凝土建筑的楼层通常采用肋梁楼盖的形式。 (5)A series of parallel ribs or joists support the load from the top slab. The reactions supporting the joists apply load to the beams, which in turn are supported by the columns. (5)一系列的平行梁肋或次梁抵抗其上楼板传来的荷载，次梁的反力作为荷载施加在主粱上，主粱则支承在柱上。 (6)The slab transfers load laterally to the joists, and serves as the top flange of the joists, which act as T-shaped beams that transmit the load to the beams running at right angles to the joists. (6)楼板将荷载垂直传递给次梁，并且作为上翼缘和次梁一起形成T形截面梁，将荷载传递给与次梁正交的主粱。 (7)Some floors of have a slab-and-beam design in which the slab spans between beams, which in turn apply loads to the columns. (7)一些楼层被设计成梁板结构，即楼板直接支承在相邻的主粱上，主粱再将荷载传递到柱上。 (8)Concrete is strong in compression but weak in tension. As a result, cracks develop whenever loads, or restrained shrinkage or temperature changes, give rise to tensile stresses in excess of the tensile strength of the concrete. (8)混凝土的抗压能力很强但抗拉能力很弱。因此，当荷载、受约束的收缩或温度变化所引起的拉应力超过其抗拉强度时，混凝土中的裂缝就会开展。 (9)The construction of a reinforced concrete member involves building a form or mould in the shape of the member being built. The form must be strong enough to support the weight and hydrostatic pressure of the wet concrete. (9)钢筋混凝土构件的制作需要一个与构件形状相同的模子，其必须具有足够的强度以抵抗湿混凝土的重量和流动压力。 (10)The reinforcement is placed in this form and held in place during the concreting
non-destructive test 非破损检验 non-load—bearingwall 非承重墙 non—uniform cross—section beam 变截面粱 non—uniformly distributed strain coefficient of longitudinal tensile reinforcement 纵向受拉钢筋应变不均匀系数 normal concrete 普通混凝土 normal section 正截面 notch and tooth joint 齿连接 number of sampling 抽样数量 O obligue section 斜截面 oblique—angle fillet weld 斜角角焊缝 one—way reinforced(or prestressed)concrete slab “单向板” open web roof truss 空腹屋架， ordinary concrete 普通混凝土(28) ordinary steel bar 普通钢筋(29) orthogonal fillet weld 直角角焊缝(61) outstanding width of flange 翼缘板外伸宽度(57) outstanding width of stiffener 加劲肋外伸宽度(57) over-all stability reduction coefficient of steel beam·钢梁整体稳定系数(58) overlap 焊瘤(62) overturning or slip resistance analysis 抗倾覆、滑移验算(10) P padding plate 垫板(52) partial penetrated butt weld 不焊透对接焊缝(61) partition 非承重墙(7) penetrated butt weld 透焊对接焊缝(60) percentage of reinforcement 配筋率(34) perforated brick 多孔砖(43) pilastered wall 带壁柱墙(42) pit·凹坑(62) pith 髓心(?o) plain concrete structure 素混凝土结构(24) plane hypothesis 平截面假定(32) plane structure 平面结构(11) plane trussed lattice grids 平面桁架系网架(5) plank 板材(65) plastic adaption coefficient of cross—section 截面塑性发展系数(58) plastic design of steel structure 钢结构塑性设计(56) plastic hinge·塑性铰(13) plastlcity coefficient of reinforced concrete member in tensile zone 受拉区混凝土塑性影响系数
理工学院毕业设计(论文)外文资料翻译 专业：热能与动力工程 姓名：赵海潮 学号：09L0504133 外文出处：Applied Acoustics, 2010(71):701~707 附件： 1.外文资料翻译译文；2.外文原文。
附件1：外文资料翻译译文 基于一维CFD模型下汽车排气消声器的实验研究与预测Takeshi Yasuda, Chaoqun Wua, Noritoshi Nakagawa, Kazuteru Nagamura 摘要目前，利用实验和数值分析法对商用汽车消声器在宽开口喉部加速状态下的排气噪声进行了研究。在加热工况下发动机转速从1000转/分钟加速到6000转/分钟需要30秒。假定其排气消声器的瞬时声学特性符合一维计算流体力学模型。为了验证模拟仿真的结果，我们在符合日本工业标准（JIS D 1616）的消声室内测量了排气消声器的瞬态声学特性，结果发现在二阶发动机转速频率下仿真结果和实验结果非常吻合。但在发动机高阶转速下（从5000到6000转每分钟的四阶转速，从4200到6000转每分钟的六阶转速这样的高转速范围内），计算结果和实验结果出现了较大差异。根据结果分析，差异的产生是由于在模拟仿真中忽略了流动噪声的影响。为了满足市场需求，研究者在一维计算流体力学模型的基础上提出了一个具有可靠准确度的简化模型，相对标准化模型而言该模型能节省超过90％的执行时间。 关键字消声器排气噪声优化设计瞬态声学性能 1 引言 汽车排气消声器广泛用于减小汽车发动机及汽车其他主要部位产生的噪声。一般而言，消声器的设计应该满足以下两个条件：（1）能够衰减高频噪声，这是消声器的最基本要求。排气消声器应该有特定的消声频率范围，尤其是低频率范围，因为我们都知道大部分的噪声被限制在发动机的转动频率和它的前几阶范围内。（2）最小背压，背压代表施加在发动机排气消声器上额外的静压力。最小背压应该保持在最低限度内，因为大的背压会降低容积效率和提高耗油量。对消声器而言，这两个重要的设计要求往往是互相冲突的。对于给定的消声器，利用实验的方法，根据距离尾管500毫米且与尾管轴向成45°处声压等级相近的排气噪声来评估其噪声衰减性能，利用压力传感器可以很容易地检测背压。 近几十年来，在预测排气噪声方面广泛应用的方法有：传递矩阵法、有限元法、边界元法和计算流体力学法。其中最常用的方法是传递矩阵法（也叫四端网络法）。该方
土木工程专业英语原文 及翻译 文档编制序号：[KKIDT-LLE0828-LLETD298-POI08]
08 级土木(1) 班课程考试试卷 考试科目专业英语 考试时间 学生姓名 所在院系土木学院 任课教师 徐州工程学院印制 Stability of Slopes Introduction Translational slips tend to occur where the adjacent stratum is at a relatively shallow depth below the surface of the slope:the failure surface tends to be plane and roughly parallel to the slips usually occur where the adjacent stratum is at greater depth，the failure surface consisting of curved and plane sections． In practice, limiting equilibrium methods are used in the analysis of slope stability. It is considered that failure is on the point of occurring along an assumed or a known failure surface．The shear strength required to maintain a condition of limiting equilibrium is compared with the available shear strength of the soil，giving the average factor of safety along the failure surface．The problem is considered in two dimensions，conditions of plane strain being assumed．It has been shown that a two-dimensional analysis gives a conservative result for a failure on a three-dimensional(dish-shaped) surface． Analysis for the Case of φu =0 This analysis, in terms of total stress，covers the case of a fully saturated clay under undrained conditions, . For the condition immediately after construction．Only moment equilibrium is considered in the analysis．In section, the potential failure surface is assumed to be a circular arc. A trial failure surface(centre O，radius r and length L a where F is the factor of safety with respect to shear strength．Equating moments about O：
学士学位证书及毕业证英文翻译模板 附录：今天老师给我们留了个作业，让我们把本科毕业证书翻译成英文的，怎么翻译啊~所以请大家帮帮忙吧~谁能给我提供一个毕业证书的英文模版啊~本科毕业证书的啊~越快越好，如果老师满意，多少钱我都不在乎~包括专升本证书，能有工商管理硕士的最好！学士学位证书英语翻译与毕业证英文翻译模板，为爱大学本科生及研究生提供英文毕业证翻译样本。首先请看《办理中英文成绩单、英文毕业证学位证书的须知》。涉及中文或英文成绩单翻译，含英文毕业证书学位证书的证明。学生学位证书英文翻译模板BACHELOR’S DEGREE CERTIFICATE This is to certify that Ms. Wang Danli, born in October 1977, has studied in the Department of Law, xxx University with a specialty of Law from September 1996 to June 2000. Upon completing and passing all the required courses of the 4-year undergraduate program, she is granted graduation. In accordance with the academic degree act of the People’s Republic of China, the aforesaid student is awarded the Bachelor’s Degree in Law. xxx Chairman of Degree Appraising Committee of xx University June 30, 2000 Certificate No.: 103354003888 本科毕业证书翻译模板DIPLOMA This is to certify that Ms. Wang Lan, born on February 29, 1980, has studied in the Department of Foreign Languages,xxxUniversity with a specialty of English from September 1997 to June 2000. Upon completing and passing all the required
Part IV：Commonly Used Professional Terms of Civil Engineering development organization 建设单位 design organization 设计单位 construction organization 施工单位 reinforced concrete 钢筋混凝土 pile 桩 steel structure 钢结构 aluminium alloy 铝合金 masonry 砌体（工程）reinforced ~ 配筋砌体load-bearing ~ 承重砌体unreinforced ~非配筋砌体 permissible stress (allowable stress) 容许应力plywood 胶合板 retaining wall 挡土墙 finish 装修 finishing material装修材料 ventilation 通风 natural ~ 自然通风 mechanical ~ 机械通风 diaphragm wall (continuous concrete wall) 地下连续墙 villa 别墅 moment of inertia 惯性矩 torque 扭矩 stress 应力normal ~ 法向应力shear ~ 剪应力 strain 应变 age hardening 时效硬化 air-conditioning system空调系统 (air) void ration（土）空隙比 albery壁厨，壁龛 a l mery壁厨，贮藏室 anchorage length锚固长度 antiseismic joint 防震缝 architectural appearance 建筑外观 architectural area 建筑面积 architectural design 建筑设计 fiashing 泛水 workability (placeability) 和易性 safety glass安全玻璃 tempered glass (reinforced glass) 钢化玻璃foamed glass泡沫玻璃 asphalt沥青 felt (malthoid) 油毡 riveted connection 铆接 welding焊接 screwed connection 螺栓连接 oakum 麻刀，麻丝 tee三通管 tap存水弯 esthetics美学 formwork 模板（工程） shoring 支撑 batching 配料 slipform construction (slipforming) 滑模施工 lfit-slab construction 升板法施工 mass concrete 大体积混凝土 terrazzo水磨石 construction joint 施工缝 honeycomb蜂窝，空洞，麻面 piled foundation桩基 deep foundation 深基础 shallow foundation浅基础 foundation depth基础埋深 pad foundation独立基础 strip foundation 条形基础 raft foundation筏基 box foundation箱形基础 BSMT=basement 地下室 lift 电梯electric elevator lift well电梯井 escalator 自动扶梯 Poisson’s ratio 泊松比μ Young’s modulus , modulus of elasticity 杨氏模量，弹性模量E safety coefficient 安全系数 fatigue failure 疲劳破坏 bearing capacity of foundations 地基承载力bearing capacity of a pile 单桩承载力 two-way-reinforcement 双向配筋 reinforced concrete two-way slabs钢筋混凝土双向板 single way slab单向板 window blind 窗帘sun blind wind load 风荷载 curing 养护 watertight concrete 防水混凝土 white cement白水泥 separating of concrete混凝土离折segregation of concrete mortar 砂浆~ joint 灰缝 pilaster 壁柱 fire rating耐火等级 fire brick 耐火砖 standard brick标准砖
故障概率模型的数控车床 摘要：领域的失效分析被计算机数字化控制（CNC）车床描述。现场收集了为期两年的约80台数控车床的故障数据。编码系统代码失效数据是制定和失效分析数据库成立的数控车床。失败的位置和子系统，失效模式及原因进行了分析，以显示薄弱子系统的数控车床。另外，故障的概率模型，分析了数控车床的模糊多准则综合评价。 作者关键词：数控车床；场失败；概率模型；模糊信息 文章概述 1.介绍 2. CNC车床的概述 3.收集和整理数据 3.1. 收集数据 3.2. 领域失效数据的有效性 3.3. 数据核对和数据库 4. 失效分析 4.1. 对失败位置和子系统的频率分析 4.2. 对失败形式的频率分析 5.失败机率模型 5.1. 方法学 5.2. 分布倍之间连续的失败 5.3. 修理时间的发行 6.结论 1.介绍 在过去十年中，计算机数字化控制（CNC）车床已经越来越多地被引入到机械加工过程中。由于其固有的灵活性很大，稳定的加工精度和高生产率，数控车床是能给用户巨大的利益。然而，作为一个单一的数控车床故障也许会导致整个生产车间被停止，而且维修更加困难和昂贵，当故障发生时[1]，数控车床能够给用户带来很多的麻烦。 与此同时，制造商还需要持续改进数控车床的可靠性来提高市场的竞争力。因此，数控车床的可靠性能使生产商和用户增加显著性和至关重要的意义。 需要改进数控车床的可靠性，使用户和制造商收集和分析领域的故障数据和采取措施减少停机时间。本文论述了研究失效模式及原因，失效的位置和薄弱的子系统，故障概率模型的数控车床。
图1 系统框图的数控车床 机械系统包括主轴及其传动链（固定在主轴箱），两根滑动轴（命名X、Z或者U，W在轮），车床拖板箱，转动架或刀架，尾座，床身等。主轴持续或加强连续变速，驱动交流或直流主轴电机直接或通过主传动，并有一个光电编码器的主轴车削螺纹。X和Z 两根轴的驱动交流或直流伺服车削螺纹和控制同时进行。该转动架或刀架可自动交换工