唐山市第九中学教学楼设计土木工程毕业设计外文文献翻译6
土木工程结构设计专业毕业设计英语翻译
XXXXXXXXX学院学士学位毕业设计（论文）英语翻译课题名称英语翻译学号学生专业、年级所在院系指导教师选题时间目录1、第一篇 (3)2、第二篇 (6)3、第三篇 (9)Concrete, Reinforced Concrete, and PrestressedConcreteConcrete is a stone like material obtained by permitting a carefully proportioned mixture of cement, sand and gravel or other aggregate, and water to harden in forms of the shape and dimensions of the desired structure. The bulk of the material consists of fine and coarse aggregate. Cement and water interact chemically to bind the aggregate particles into a solid mass. Additional water, over and above that needed for this chemical reaction, is necessary to give the mixture workability that enables it to fill the forms and surround the embedded reinforcing steel prior to hardening. Concretes with a wide range of properties can be obtained by appropriates adjustment of the proportions of the constituent materials. Special cements, special aggregates, and special curing methods permit an even wider variety of properties to be obtained.These properties depend to a very substantial degree on the proportions of the mix, on the thoroughness with which the various constituents are intermixed, and on the conditions of humidity and temperature in which the mix is maintained from the moment it is placed in the forms of humidity and hardened. The process of controlling conditions after placement is known as curing. To protect against the unintentional production of substandard concrete, a high degree of skillful control and supervision is necessary throughout the process, from the proportioning by weight of the individual components, trough mixing and placing, until the completion of curing.The factors that make concrete a universal building material are so pronounced that it has been used, in more primitive kinds and ways than at present, for thousands of years, starting with lime mortars from 12,000 to 600 B.C. in Crete, Cyprus, Greece, and the Middle East. The facility with which , while plastic, it can be deposited and made to fill forms or molds of almost any practical shape is one of these factors. Its high fire and weather resistance are evident advantages. Most of the constituent materials, with the exception of cement and additives, are usually available at low cost locally or at small distances from the construction site. Its compressive strength, like that of natural stones, is high, which makes it suitable for members primarily subject to compression, such as columns and arches. On the other hand, again as in natural stones, it is a relatively brittle material whose tensile strength is small compared with its compressive strength. This prevents its economical use in structural members that ate subject to tension either entirely or over part of their cross sections.To offset this limitation, it was found possible, in the second half of thenineteenth century, to use steel with its high tensile strength to reinforce concrete, chiefly in those places where its low tensile strength would limit the carrying capacity of the member. The reinforcement, usually round steel rods with appropriate surface deformations to provide interlocking, is places in the forms in advance of the concrete. When completely surrounded by the hardened concrete mass, it forms an integral part of the member. The resulting combination of two materials, known as reinforced concrete, combines many of the advantages of each: the relatively low cost , good weather and fire resistance, good compressive strength, and excellent formability of concrete and the high tensile strength and much greater ductility and toughness of steel. It is this combination that allows the almost unlimited range of uses and possibilities of reinforced concrete in the construction of buildings, bridges, dams, tanks, reservoirs, and a host of other structures.In more recent times, it has been found possible to produce steels, at relatively low cost, whose yield strength is 3 to 4 times and more that of ordinary reinforcing steels. Likewise, it is possible to produce concrete 4 to 5 times as strong in compression as the more ordinary concrete. These high-strength materials offer many advantages, including smaller member cross sections, reduced dead load, and longer spans. However, there are limits to the strengths of the constituent materials beyond which certain problems arise. To be sure, the strength of such a member would increase roughly in proportion to those of the materials. However, the high strains that result from the high stresses that would otherwise be permissible would lead to large deformations and consequently large deflections of such member under ordinary loading conditions. Equally important, the large strains in such high-strength reinforcing steel would induce large cracks in the surrounding low tensile strength concrete, cracks that would not only be unsightly but that could significantly reduce the durability of the structure. This limits the useful yield strength of high-strength reinforcing steel to 80 ksi according to many codes and specifications; 60 ksi steel is most commonly used.A special way has been found, however, to use steels and concrete of very high strength in combination. This type of construction is known as prestressed concrete. The steel, in the form of wires, strands, or bars, is embedded in the concrete under high tension that is held in equilibrium by compressive stresses in the concrete after hardening, Because of this precompression, the concrete in a flexural member will crack on the tension side at a much larger load than when not so precompressed. Prestressing greatly reduces both the deflections and the tensile cracks at ordinaryloads in such structures, and thereby enables these high-strength materials to be used effectively. Prestressed concrete has extended, to a very significant extent, the range of spans of structural concrete and the types of structures for which it is suited.混凝土，钢筋混凝土和预应力混凝土混凝土是一种经过水泥，沙子和砂砾或其他材料聚合得到经过细致配比的混合物，在液体变硬使材料石化后可以得到理想的形状和结构尺寸。
土木工程毕业设计外文翻译原文+翻译
The bridge crack produced the reason to simply analyseIn recent years, the traffic capital construction of our province gets swift and violent development, all parts have built a large number of concrete bridges. In the course of building and using in the bridge, relevant to influence project quality lead of common occurrence report that bridge collapse even because the crack appears The concrete can be said to " often have illness coming on " while fracturing and " frequently-occurring disease ", often perplex bridge engineers and technicians. In fact , if take certain design and construction measure, a lot of cracks can be overcome and controlled. For strengthen understanding of concrete bridge crack further, is it prevent project from endanger larger crack to try one's best, this text make an more overall analysis , summary to concrete kind and reason of production , bridge of crack as much as possible, in order to design , construct and find out the feasible method which control the crack , get the result of taking precautions against Yu WeiRan.Concrete bridge crack kind, origin cause of formation In fact, the origin cause of formation of the concrete structure crack is complicated and various, even many kinds of factors influence each other , but every crack has its one or several kinds of main reasons produced . The kind of the concrete bridge crack, on its reason to produce, can roughly divide several kinds as follows :(1) load the crack caused Concrete in routine quiet .Is it load to move and crack that produce claim to load the crack under the times of stress bridge, summing up has direct stress cracks , two kinds stress crack onces mainly. Direct stress crack refer to outside load direct crack that stress produce that cause. The reason why the crack produces is as follows, 1, Design the stage of calculating , does not calculate or leaks and calculates partly while calculating in structure; Calculate the model is unreasonable; The structure is supposed and accorded with by strength actually by strength ; Load and calculate or leak and calculate few; Internal force and matching the mistake in computation of muscle; Safety coefficient of structure is not enough. Do not consider the possibility that construct at the time of the structural design; It is insufficientto design the section; It is simply little and assigning the mistake for reinforcing bar to set up; Structure rigidity is insufficient; Construct and deal with improperly; The design drawing can not be explained clearly etc.. 2, Construction stage, does not pile up and construct the machines , material limiting ; Is it prefabricate structure structure receive strength characteristic , stand up , is it hang , transport , install to get up at will to understand; Construct not according to the design drawing, alter the construction order of the structure without authorization , change the structure and receive the strength mode; Do not do the tired intensity checking computations under machine vibration and wait to the structure . 3, Using stage, the heavy-duty vehicle which goes beyond the design load passes the bridge; Receive the contact , striking of the vehicle , shipping; Strong wind , heavy snow , earthquake happen , explode etc.. Stress crack once means the stress of secondary caused by loading outside produces the crack. The reason why the crack produces is as follows, 1, In design outside load function , because actual working state and routine , structure of thing calculate have discrepancy or is it consider to calculate, thus cause stress once to cause the structure to fracture in some position. Two is it join bridge arch foot is it is it assign " X " shape reinforcing bar , cut down this place way , section of size design and cut with scissors at the same time to adopt often to design to cut with scissors, theory calculate place this can store curved square in , but reality should is it can resist curved still to cut with scissors, so that present the crack and cause the reinforcing bar corrosion. 2, Bridge structure is it dig trough , turn on hole , set up ox leg ,etc. to need often, difficult to use a accurate one diagrammatic to is it is it calculate to imitate to go on in calculating in routine, set up and receive the strength reinforcing bar in general foundation experience. Studies have shown , after being dug the hole by the strength component , it will produce the diffraction phenomenon that strength flows, intensive near the hole in a utensil, produced the enormous stress to concentrate. In long to step prestressing force of the continuous roof beam , often block the steel bunch according to the needs of section internal force in stepping, set up the anchor head, but can often see the crack in the anchor firm section adjacent place. So if deal with improper, in corner or component form sudden change office , block place to be easy to appear crack strengthreinforcing bar of structure the. In the actual project, stress crack once produced the most common reason which loads the crack. Stress crack once belong to one more piece of nature of drawing , splitting off , shearing. Stress crack once is loaded and caused, only seldom calculate according to the routine too, but with modern to calculate constant perfection of means, times of stress crack to can accomplish reasonable checking computations too. For example to such stresses 2 times of producing as prestressing force , creeping ,etc., department's finite element procedure calculates levels pole correctly now, but more difficult 40 years ago. In the design, should pay attention to avoiding structure sudden change (or section sudden change), when it is unable to avoid , should do part deal with , corner for instance, make round horn , sudden change office make into the gradation zone transition, is it is it mix muscle to construct to strengthen at the same time, corner mix again oblique to reinforcing bar , as to large hole in a utensil can set up protecting in the perimeter at the terms of having angle steel. Load the crack characteristic in accordance with loading differently and presenting different characteristics differently. The crack appear person who draw more, the cutting area or the serious position of vibration. Must point out , is it get up cover or have along keep into short crack of direction to appear person who press, often the structure reaches the sign of bearing the weight of strength limit, it is an omen that the structure is destroyed, its reason is often that sectional size is partial and small. Receive the strength way differently according to the structure, the crack characteristic produced is as follows: 1, The centre is drawn. The crack runs through the component cross section , the interval is equal on the whole , and is perpendicular to receiving the strength direction. While adopting the whorl reinforcing bar , lie in the second-class crack near the reinforcing bar between the cracks. 2, The centre is pressed. It is parallel on the short and dense parallel crack which receive the strength direction to appear along the component. 3, Receive curved. Most near the large section from border is it appear and draw into direction vertical crack to begin person who draw curved square, and develop toward neutralization axle gradually. While adopting the whorl reinforcing bar , can see shorter second-class crack among the cracks. When the structure matches muscles less, there are few but wide cracks, fragility destruction may take place in thestructure 4, Pressed big and partial. Heavy to press and mix person who draw muscle a less one light to pigeonhole into the component while being partial while being partial, similar to receiving the curved component. 5, Pressed small and partial. Small to press and mix person who draw muscle a more one heavy to pigeonhole into the component while being partial while being partial, similar to the centre and pressed the component. 6, Cut. Press obliquly when the hoop muscle is too dense and destroy, the oblique crack which is greater than 45?? direction appears along the belly of roof beam end; Is it is it is it destroy to press to cut to happen when the hoop muscle is proper, underpart is it invite 45?? direction parallel oblique crack each other to appear along roof beam end. 7, Sprained. Component one side belly appear many direction oblique crack, 45?? of treaty, first, and to launch with spiral direction being adjoint. 8, Washed and cut. 4 side is it invite 45?? direction inclined plane draw and split to take place along column cap board, form the tangent plane of washing. 9, Some and is pressed. Some to appear person who press direction roughly parallel large short cracks with pressure.(2) crack caused in temperature changeThe concrete has nature of expanding with heat and contract with cold, look on as the external environment condition or the structure temperature changes, concrete take place out of shape, if out of shape to restrain from, produce the stress in the structure, produce the temperature crack promptly when exceeding concrete tensile strength in stress. In some being heavy to step foot-path among the bridge , temperature stress can is it go beyond living year stress even to reach. The temperature crack distinguishes the main characteristic of other cracks will be varied with temperature and expanded or closed up. The main factor is as follows, to cause temperature and change 1, Annual difference in temperature. Temperature is changing constantly in four seasons in one year, but change relatively slowly, the impact on structure of the bridge is mainly the vertical displacement which causes the bridge, can prop up seat move or set up flexible mound ,etc. not to construct measure coordinate , through bridge floor expansion joint generally, can cause temperature crack only when the displacement of the structure is limited, for example arched bridge , just bridge etc. The annual difference in temperature of our country generally changes therange with the conduct of the average temperature in the moon of January and July. Considering the creep characteristic of the concrete, the elastic mould amount of concrete should be considered rolling over and reducing when the internal force of the annual difference in temperature is calculated. 2, Rizhao. After being tanned by the sun by the sun to the side of bridge panel , the girder or the pier, temperature is obviously higher than other position, the temperature gradient is presented and distributed by the line shape . Because of restrain oneself function, cause part draw stress to be relatively heavy, the crack appears. Rizhao and following to is it cause structure common reason most , temperature of crack to lower the temperature suddenly 3, Lower the temperature suddenly. Fall heavy rain , cold air attack , sunset ,etc. can cause structure surface temperature suddenly dropped suddenly, but because inside temperature change relatively slow producing temperature gradient. Rizhao and lower the temperature internal force can adopt design specification or consult real bridge materials go on when calculating suddenly, concrete elastic mould amount does not consider converting into and reducing 4, Heat of hydration. Appear in the course of constructing, the large volume concrete (thickness exceeds 2. 0), after building because cement water send out heat, cause inside very much high temperature, the internal and external difference in temperature is too large, cause the surface to appear in the crack. Should according to actual conditions in constructing, is it choose heat of hydration low cement variety to try one's best, limit cement unit's consumption, reduce the aggregate and enter the temperature of the mould , reduce the internal and external difference in temperature, and lower the temperature slowly , can adopt the circulation cooling system to carry on the inside to dispel the heat in case of necessity, or adopt the thin layer and build it in succession in order to accelerate dispelling the heat. 5, The construction measure is improper at the time of steam maintenance or the winter construction , the concrete is sudden and cold and sudden and hot, internal and external temperature is uneven , apt to appear in the crack. 6, Prefabricate T roof beam horizontal baffle when the installation , prop up seat bury stencil plate with transfer flat stencil plate when welding in advance, if weld measure to be improper, iron pieces of nearby concrete easy to is it fracture to burn. Adopt electric heat piece draw law piece draw prestressing force at the component ,prestressing force steel temperature can rise to 350 degrees Centigrade , the concrete component is apt to fracture. Experimental study indicates , are caused the intensity of concrete that the high temperature burns to obviously reduce with rising of temperature by such reasons as the fire ,etc., glueing forming the decline thereupon of strength of reinforcing bar and concrete, tensile strength drop by 50% after concrete temperature reaches 300 degrees Centigrade, compression strength drops by 60%, glueing the strength of forming to drop by 80% of only round reinforcing bar and concrete; Because heat, concrete body dissociate ink evaporate and can produce and shrink sharply in a large amount(3) shrink the crack causedIn the actual project, it is the most common because concrete shrinks the crack caused. Shrink kind in concrete, plasticity shrink is it it shrinks (is it contract to do ) to be the main reason that the volume of concrete out of shape happens to shrink, shrink spontaneously in addition and the char shrink. Plasticity shrink. About 4 hours after it is built that in the course of constructing , concrete happens, the cement water response is fierce at this moment, the strand takes shape gradually, secrete water and moisture to evaporate sharply, the concrete desiccates and shrinks, it is at the same time conduct oneself with dignity not sinking because aggregate,so when harden concrete yet,it call plasticity shrink. The plasticity shrink producing amount grade is very big, can be up to about 1%. If stopped by the reinforcing bar while the aggregate sinks, form the crack along the reinforcing bar direction. If web , roof beam of T and roof beam of case and carry baseplate hand over office in component vertical to become sectional place, because sink too really to superficial obeying the web direction crack will happen evenly before hardenning. For reducing concrete plasticity shrink,it should control by water dust when being construct than,last long-time mixing, unloading should not too quick, is it is it take closely knit to smash to shake, vertical to become sectional place should divide layer build. Shrink and shrink (do and contract). After the concrete is formed hard , as the top layer moisture is evaporated progressively , the humidity is reduced progressively , the volume of concrete is reduced, is called and shrunk to shrink (do and contract). Because concrete top layermoisture loss soon, it is slow for inside to lose, produce surface shrink heavy , inside shrink a light one even to shrink, it is out of shape to restrain from by the inside concrete for surface to shrink, cause the surface concrete to bear pulling force, when the surface concrete bears pulling force to exceed its tensile strength, produce and shrink the crack. The concrete hardens after-contraction to just shrink and shrink mainly .Such as mix muscle rate heavy component (exceed 3% ), between reinforcing bar and more obvious restraints relatively that concrete shrink, the concrete surface is apt to appear in the full of cracks crackle. Shrink spontaneously. Spontaneous to it shrinks to be concrete in the course of hardenning , cement and water take place ink react, the shrink with have nothing to do by external humidity, and can positive (whether shrink, such as ordinary portland cement concrete), can negative too (whether expand, such as concrete, concrete of slag cement and cement of fly ash). The char shrinks. Between carbon dioxide and hyrate of cement of atmosphere take place out of shape shrink that chemical reaction cause. The char shrinks and could happen only about 50% of humidity, and accelerate with increase of the density of the carbon dioxide. The char shrinks and seldom calculates . The characteristic that the concrete shrinks the crack is that the majority belongs to the surface crack, the crack is relatively detailed in width , and criss-cross, become the full of cracks form , the form does not have any law . Studies have shown , influence concrete shrink main factor of crack as follows, 1, Variety of cement , grade and consumption. Slag cement , quick-hardening cement , low-heat cement concrete contractivity are relatively high, ordinary cement , volcanic ash cement , alumina cement concrete contractivity are relatively low. Cement grade low in addition, unit volume consumption heavy rubing detailed degree heavy, then the concrete shrinks the more greatly, and shrink time is the longer. For example, in order to improve the intensity of the concrete , often adopt and increase the cement consumption method by force while constructing, the result shrinks the stress to obviously strengthen . 2, Variety of aggregate. Such absorbing water rates as the quartz , limestone , cloud rock , granite , feldspar ,etc. are smaller, contractivity is relatively low in the aggregate; And such absorbing water rates as the sandstone , slate , angle amphibolite ,etc. are greater, contractivity is relatively high. Aggregate grains of foot-path heavy to shrink light inaddition, water content big to shrink the larger. 3, Water gray than. The heavier water consumption is, the higher water and dust are, the concrete shrinks the more greatly. 4, Mix the pharmaceutical outside. It is the better to mix pharmaceutical water-retaining property outside, then the concrete shrinks the smaller. 5, Maintain the method . Water that good maintenance can accelerate the concrete reacts, obtain the intensity of higher concrete. Keep humidity high , low maintaining time to be the longer temperature when maintaining, then the concrete shrinks the smaller. Steam maintain way than maintain way concrete is it take light to shrink naturall. 6, External environment. The humidity is little, the air drying , temperature are high, the wind speed is large in the atmosphere, then the concrete moisture is evaporated fast, the concrete shrinks the faster. 7, Shake and smash the way and time. Machinery shake way of smashing than make firm by ramming or tamping way concrete contractivity take little by hand. Shaking should determine according to mechanical performance to smash time , are generally suitable for 55s / time. It is too short, shake and can not smash closely knit , it is insufficient or not even in intensity to form the concrete; It is too long, cause and divide storey, thick aggregate sinks to the ground floor, the upper strata that the detailed aggregate stays, the intensity is not even , the upper strata incident shrink the crack. And shrink the crack caused to temperature, worthy of constructing the reinforcing bar againing can obviously improve the resisting the splitting of concrete , structure of especially thin wall (thick 200cm of wall ). Mix muscle should is it adopt light diameter reinforcing bar (8 |? construct 14 |? ) to have priority , little interval assign (whether @ 10 construct @ 15cm ) on constructing, the whole section is it mix muscle to be rate unsuitable to be lower than 0 to construct. 3%, can generally adopt 0 . 3%~0. 5%.(4), crack that causes out of shape of plinth of the groundBecause foundation vertical to even to subside or horizontal direction displacement, make the structure produce the additional stress, go beyond resisting the ability of drawing of concrete structure, cause the structure to fracture. The even main reason that subside of the foundation is as follows, 1, Reconnoitres the precision and is not enough for , test the materials inaccuratly in geology. Designing, constructing without fully grasping the geological situation, this is the main reason that cause the ground not to subside evenly .Such as hills area or bridge, district of mountain ridge,, hole interval to be too far when reconnoitring, and ground rise and fall big the rock, reconnoitring the report can't fully reflect the real geological situation . 2, The geological difference of the ground is too large. Building it in the bridge of the valley of the ditch of mountain area, geology of the stream place and place on the hillside change larger, even there are weak grounds in the stream, because the soil of the ground does not causes and does not subside evenly with the compressing. 3, The structure loads the difference too big. Under the unanimous terms, when every foundation too heavy to load difference in geological situation, may cause evenly to subside, for example high to fill out soil case shape in the middle part of the culvert than to is it take heavy to load both sides, to subside soon heavy than both sides middle part, case is it might fracture to contain 4, The difference of basic type of structure is great. Unite it in the bridge the samly , mix and use and does not expand the foundation and a foundation with the foundation, or adopt a foundation when a foot-path or a long difference is great at the same time , or adopt the foundation of expanding when basis elevation is widely different at the same time , may cause the ground not to subside evenly too 5, Foundation built by stages. In the newly-built bridge near the foundation of original bridge, if the half a bridge about expressway built by stages, the newly-built bridge loads or the foundation causes the soil of the ground to consolidate again while dealing with, may cause and subside the foundation of original bridge greatly 6, The ground is frozen bloatedly. The ground soil of higher moisture content on terms that lower than zero degree expands because of being icy; Once temperature goes up , the frozen soil is melted, the setting of ground. So the ground is icy or melts causes and does not subside evenly . 7, Bridge foundation put on body, cave with stalactites and stalagmites, activity fault,etc. of coming down at the bad geology, may cause and does not subside evenly . 8, After the bridge is built up , the condition change of original ground . After most natural grounds and artificial grounds are soaked with water, especially usually fill out such soil of special ground as the soil , loess , expanding in the land ,etc., soil body intensity meet water drop, compress out of shape to strengthen. In the soft soil ground , season causes the water table to drop to draw water or arid artificially, the ground soil layer consolidates and sinks again,reduce the buoyancy on the foundation at the same time , shouldering the obstruction of rubing to increase, the foundation is carried on one's shoulder or back and strengthened .Some bridge foundation is it put too shallow to bury, erode , is it dig to wash flood, the foundation might be moved. Ground load change of terms, bridge nearby is it is it abolish square , grit ,etc. in a large amount to put to pile with cave in , landslide ,etc. reason for instance, it is out of shape that the bridge location range soil layer may be compressed again. So, the condition of original ground change while using may cause and does not subside evenly Produce the structure thing of horizontal thrust to arched bridge ,etc., it is the main reason that horizontal displacement crack emerges to destroy the original geological condition when to that it is unreasonable to grasp incompletely , design and construct in the geological situation.桥梁裂缝产生原因浅析近年来，我省交通基础建设得到迅猛发展，各地建立了大量的混凝土桥梁。
土木工程毕业设计中英文翻译
土木工程毕业设计中英文翻译附录:中英文翻译英文部分:LOADSLoads that act on structures are usually classified as dead loads or live loads.Dead loads are fixed in location and constant in magnitude throughout the life of the ually the self-weight of a structure is the most important part of the structure and the unit weight of the material.Concrete density2varies from about 90 to 120 pcf (14 to 19 )for lightweight concrete,and is about 145 pcf (23 KN/m2)for normal concrete.In calculating the dead load of structural concrete,usually a 5 pcf (1 KN/m2)increment is included with the weight of the concrete to account for the presence of the KN/mreinforcement.Live loads are loads such as occupancy,snow,wind,or traffic loads,or seismic forces.They may be either fully or partially in place,or not present at all.They may also change in location.Althought it is the responsibility of the engineer to calculate dead loads,live loads are usually specified by local,regional,or national codes and specifications.Typical sources are the publications of the American National Standards Institute,the American Association of StateHighway and Transportation Officials and,for wind loads,the recommendations of the ASCE Task Committee on Wind Forces.Specified live the loads usually include some allowance for overload,and may include measures such as posting of maximum loads will not be exceeded.It is oftern important to distinguish between the specified load,and what is termed the characteristic load,that is,the load that actually is in effect under normal conditions of service,which may be significantly less.In estimating the long-term deflection of a structure,for example,it is the characteristic load that isimportant,not the specified load.The sum of the calculated dead load and the specified live load is called the service load,because this is the maximum load which may reasonably be expected to act during the service resisting is a multiple of the service load.StrengthThe strength of a structure depends on the strength of the materials from which it is made.Minimum material strengths are specified incertain standardized ways.The properties of concrete and its components,the methods of mixing,placing,and curing to obtain the required quality,and the methods for testing,are specified by the American Concrete Insititue(ACI).Included by refrence in the same documentare standards of the American Society for TestingMaterials(ASTM)pertaining to reinforcing and prestressing steels and concrete.Strength also depends on the care with which the structure isbuilt.Member sizes may differ from specified dimensions,reinforcement may be out of position,or poor placement of concrete may result in voids.An important part of the job of the ergineer is to provide proper supervision of construction.Slighting of this responsibility has had disastrous consequences in more than one instance.Structural SafetySafety requires that the strength of a structure be adequate for all loads that may conceivably act on it.If strength could be predicted accurately and if loads were known with equal certainty,then safely could be assured by providing strength just barely in excess of the requirements of the loads.But there are many sources of uncertainty in the estimation of loads as well as in analysis,design,andconstruction.These uncertainties require a safety margin.In recent years engineers have come to realize that the matter of structural safety is probabilistic in nature,and the safety provisions of many current specifications reflect this view.Separate consideration is given to loads and strength.Loadfactors,larger than unity,are applied to the calculated dead loads and estimated or specified service live loads,to obtain factorde loads that the member must just be capable of sustaining at incipient failure.Loadfactors pertaining to different types of loads vary,depending on the degree of uncertainty associated with loads of various types,and with the likelihood of simultaneous occurrence of different loads.Early in the development of prestressed concrete,the goal of prestressing was the complete elimination of concrete ternsile stress at service loads.The concept was that of an entirely new,homogeneous material that woukd remain uncracked and respond elastically up to the maximum anticipated loading.This kind of design,where the limiting tensile stressing,while an alternative approach,in which a certain amount of tensile amount of tensile stress is permitted in the concrete at full service load,is called partial prestressing.There are cases in which it is necessary to avoid all risk of cracking and in which full prestressing is required.Such cases include tanks or reservious where leaks must be avoided,submerged structures or those subject to a highly corrosive envionment where maximum protection of reinforcement must be insured,and structures subject to high frequency repetition of load where faatigue of the reinforcement may be a consideration.However,there are many cses where substantially improved performance,reduced cost,or both may be obtained through the use of a lesser amount of prestress.Full predtressed beams may exhibit an undesirable amount of upward camber because of the eccentric prestressing force,a displacement that is only partially counteracted by the gravity loads producing downward deflection.This tendency isaggrabated by creep in the concrete,which magnigies the upward displacement due to the prestress force,but has little influence on the should heavily prestressed members be overloaded and fail,they may do so in a brittle way,rather than gradually as do beams with a smaller amount of prestress.This is important from the point of view of safety,because suddenfailure without warning is dangeroud,and gives no opportunity for corrective measures to be taken.Furthermore,experience indicates that in many cases improved economy results from the use of a combination of unstressed bar steel and high strength prestressed steel tendons.While tensile stress and possible cracking may be allowed at full service load,it is also recognized that such full service load may be infrequently applied.The typical,or characteristic,load acting is likely to be the dead load plus a small fraction of the specified liveload.Thus a partially predtressed beam may not be subject to tensile stress under the usual conditions of loading.Cracks may from occasionally,when the maximum load is applied,but these will close completely when that load is removed.They may be no more objectionablein prestressed structures than in ordinary reinforced.They may be no more objectionable in prestressed structures than in ordinary reinforced concrete,in which flexural cracks always form.They may be considered a small price for the improvements in performance and economy that are obtained.It has been observed that reinforced concrete is but a special case of prestressed concrete in which the prestressing force is zero.Thebehavior of reinforced and prestressed concrete beams,as the failure load is approached,is essentially the same.The Joint European Committee on Concrete establishes threee classes of prestressed beams.Class 1:Fully prestressed,in which no tensile stress is allowed in the concrete at service load.Class 2:Partially prestressed, in which occasional temporary cracking is permitted under infrequent high loads.Class 3:Partially prestressed,in which there may be permanent cracks provided that their width is suitably limited.The choise of a suitable amount of prestress is governed by avariety of factors.These include thenature of the loading (for exmaple,highway or railroadbridged,storage,ect.),the ratio of live to dead load,the frequency of occurrence of loading may be reversed,such as in transmission poles,a high uniform prestress would result ultimate strength and in brittle failure.In such a case,partial prestressing provides the only satifactory solution.The advantages of partial prestressing are important.A smaller prestress force will be required,permitting reduction in the number of tendons and anchorages.The necessary flexural strength may be provided in such cases either by a combination of prestressed tendons and non-prestressed reinforcing bars,or by an adequate number of high-tensile tendons prestredded to level lower than the prestressing force isless,the size of the bottom flange,which is requied mainly to resist the compression when a beam is in the unloaded stage,can be reduced or eliminated altogether.This leads in turn to significant simplification and cost reduction in the construction of forms,as well as resulting in structures that are mor pleasing esthetically.Furthermore,by relaxing the requirement for low service load tension in the concrete,a significant improvement can be made in the deflection characteristics of a beam.Troublesome upward camber of the member in the unloaded stage fan be avoeded,and the prestress force selected primarily to produce the desired deflection for a particular loading condition.The behavior of partially prestressed beamsm,should they be overloaded to failure,is apt to be superior to that of fully prestressed beams,because the improved ductility provides ample warning of distress.英译汉:荷载作用在结构上的荷载通常分为恒载或活载。
土木工程专业毕业设计外文文献及翻译
英文原文：Rehabilitation of rectangular simply supported RC beams with shear deficiencies using CFRP compositesAhmed Khalifa a,* , Antonio Nanni ba Department of Structural Engineering, University of Alexandria, Alexandria 21544, Egyptb Department of Civil Engineering, University of Missouri at Rolla, Rolla, MO 65409, USAReceived 28 April 1999; received in revised form 30 October 2001; accepted 10 January 2002AbstractThe present study examines the shear performance and modes of failure of rectangular simply supported reinforced concrete(RC) beams designed with shear deficiencies. These members were strengthened with externally bonded carbon fiber reinforced polymer (CFRP) sheets and evaluated in the laboratory. The experimental program consisted of twelve full-scale RC beams tested to fail in shear. The variables investigated within this program included steel stirrups, and the shear span-to-effective depth ratio, as well as amount and distribution of CFRP. The experimental results indicated that the contribution of externally bonded CFRP to the shear capacity was significant. The shear capacity was also shown to be dependent upon the variables investigated. Test results were used to validate a shear design approach, which showed conservative and acceptable predictions.○C2002 Elsevier Science Ltd. All rights reserved.Keywords: Rehabilitation; Shear; Carbon fiber reinforced polymer1. IntroductionFiber reinforced polymer (FRP) composite systems, composed of fibers embedded in a polymeric matrix, can be used for shear strengthening of reinforced con-crete(RC) members [1–7]. Many existing RC beams are deficient and in need of strengthening. The shear failure of an RC beam is clearly different from its flexural failure. In shear, the beam fails suddenly without sufficient warning and diagonal shear cracks are consid-erably wider than the flexural cracks [8].The objectives of this program were to:1. Investigate performance and mode of failure of simply supported rectangular RC beams with shear deficien-cies after strengthening with externally bonded CFRP sheets.2. Address the factors that influence shear capacity of strengthened beams such as: steel stirrups, shear span-to-effective depth ratio (a/d ratio), and amount and distribution of CFRP.3. Increase the experimental database on shear strength-ening with externally bonded FRP reinforcement.4. Validate the design approach previously proposed by the authors [9].For these objectives, 12 full-scale, RC beams designed to fail in shear were strengthened with different CFRP schemes. These members were tested as simple beams using a four-point loading configuration with two different a/d ratios.2. Experimental program2.1. Test specimens and materialsTwelve full-scale beam specimens with a total span of 3050 mm. and a rectangular cross-section of 150-mm-wide and 305-mm-deep were tested. The specimens were grouped into two main series designated SW and SO depending on the presence of steel stirrups in the shear span of interest.Series SW consisted of four specimens. The details and dimensions of the specimens designated series SW are illustrated in Fig. 1a. In this series, four 32-mm steel bars were used as longitudinal reinforcement with two at top and two at bottom face of the cross-section to induce a shear failure. The specimens were reinforced with 10-mm steel stirrups throughout their entire span. The stirrups spacing in the shear span of interest, right half, was selected to allow failure in that span.Series SO consisted of eight beam specimens, which had the same cross-section dimension and longitudinal steel reinforcement as for series SW. No stirrups were provided in the test half span as illustrated.Each main series (i.e. series SW and SO) was subdivided into two subgroups according to shear span-to-effective depth ratio. This was selected to be a/d = 3 and 4, resulting in the following four subgroups: SW3;SW4; SO3; and SO4.The mechanical properties of the materials used for manufacturing the test specimens are listed in Table 1.Fabrication of the specimens including surface preparation and CFRP installation is described elsewhere [10].2.2. Strengthening schemesOne specimen from each series (SW3-1, SW4-1, SO3-1 and SO4-1) was left without strengthening as a control specimen, whereas eight beam specimens were strengthened with externally bonded CFRP sheets following three different schemes as illustrated in Fig. 2.In series SW3, specimen SW3-2 was strengthened with two CFRP plies having perpendicular fiber directions (90°/0°). The first ply was attached in the form of continuous U-wrap with the fiber direction oriented perpendicular to the longitudinal axis of the specimen (90°). The second ply was bonded on the two sides of the specimen with the fiber direction parallel to the beam axis（0°）.This ply [i.e. 0°ply] was selected to investigate the impact of additional horizontal restraint on shear strength.In series SW4, specimen SW4-2 was strengthened with two CFRP plies having perpendicular fiber direction (90°/0°) as for specimen SW3-2.Four beam specimens were strengthened in series SO3. Specimen SO3-2 was strengthened with one-ply CFRP strips in the form of U-wrap with 90°-fiber orientation. The strip width was 50 mm with center-to-center spacing of 125 mm. Specimen SO3-3 was strengthened in a manner similar to that of specimen SO3-2, but with strip width equal to 75 mm. Specimen SO3-4 was strengthened with one-plycontinuous U-wrap (90°). Specimen SO3-5 was strengthened with twoCFRP plies (90°/0°) similar to specimens SW3-2 and SW4-2.In series SO4, two beam specimens were strengthened. Specimen SO4-2 was strengthened with one-ply CFRP strips in the form of U-wrap similar to specimen SO3-2. Specimen SO4-3 was strengthened with one-ply continuous U-wrap (90°) similar to SO3-4.2.3. Test set-up and instrumentationAll specimens were tested as simple span beams subjected to a four-point load as illustrated in Fig. 3. A universal testing machine with 1800 KN capacity was used in order to apply a concentrated load on a steel distribution beam used to generate the two concentrated loads. The load was applied progressively in cycles, usually one cycle before cracking followed by three cycles with the last one up to ultimate. The applied load vs. deflection curves shown in this paper are the envelopes of these load cycles.Four linear variable differential transformers (LVDTs) were used for each test to monitor vertical displacements at various locations as shown in Fig. 3. Two LVDTs were located at mid-span on each side of the specimen. The other two were located at the specimen supports to record support settlement.For each specimen of series SW, six strain gauges were attached to three stirrups to monitor the stirrup strain during loading as illustrated in Fig. 1a. Three strain gauges were attached directly to the FRP sheet on the sides of each strengthened beam to monitor strain variation in the FRP. The strain gauges were oriented in the vertical direction and located at the section mid-height with distances of 175, 300 and 425 mm, respectively, from the support for series SW3 and SO3. For beam specimens of series SW4 and SO4, the strain gauges were located at distance of 375, 500 and 625 mm, respectively, from the support.3. Results and discussionIn the following discussion, reference is always made to weak shear span or spanof interest.3.1. Series SW3Shear cracks in the control specimen SW3-1 were observed close to the middle of the shear span when the load reached approximately 90 kN. As the load increased, additional shear cracks formed throughout, widening and propagating up to final failure at a load of 253 kNIn specimen SW3-2 strengthened with CFRP (90°/0°), no cracks were visible on the sides or bottom of the test specimen due to the FRP wrapping. However，a longitudinal splitting crack initiated on the top surface of the beam at a high load of approximately 320 kN.The crack initiated at the location of applied load and extended towards the support. The specimen failed by concrete splitting at total load of 354 kN. This was an increase of 40% in ultimate capacity compared to the control specimen SW3-1. The splitting failure was due to the relatively high longitudinal compressive stress developed at top of the specimen, which created a transverse tension, led to the splitting failure. In addition, the relatively large amount of longitudinal steel reinforcement combined with over-strengthening for shear by CFRP wrap probably caused this mode of failure. The load vs. mid-span deflection curves for specimens SW3-1 and SW3-2 are illustrated , to show the additional capacity gained by CFRP. The maximum CFRP vertical strain measured at failure in specimen SW3-2 was approximately 0.0023 mm/mm, which corresponded to 14% of the reported CFRP ultimate strain. This value is not an absolute because it greatly depends on the location of the strain gauges with respect to a crack. However, the recorded strain indicates that if the splitting did not occur, the shear capacity could have reached higher load.Comparison between measured local stirrup strains in specimens SW3-1 and SW3-2 are shown in Fig. 6. The stirrups 1, 2 and 3 were located at distance of 175, 300 and 425 mm from the support, respectively. The results showed that the stirrups2 and3 did not yield at ultimate for both specimens. The strains (and the forces) in the stirrups of specimen SW3-2 were, in general, smaller than those of specimen SW3-1 at the same level of loading due to the effect of CFRP.3.2. Series SW4In specimen SW4-1, the first diagonal crack was formed in the member at a total applied load of 75 kN. As the load increased, additional shear cracks appeared throughout the shear span. Failure of the beam occurred when the total applied load reached 200 kN. This was a decrease of 20% in shear capacity compared to the specimen SW3-1In specimen SW4-2, the failure was controlled by concrete splitting similar to test specimen SW3-2. The total applied load at ultimate was 361 kN with an 80% increase in shear capacity compared to the control specimen SW4-1. In addition, the measured strains in the stirrups for specimen SW4-2 were less than those of specimen SW4-1. The applied load vs. mid-span deflection curves for beams SW4-1 and SW4-2 are illustrated . It may be noted that specimen SW4-2 resulted in greater deflection when compared to specimen SW4-1.When comparing the test results of series SW3 specimens to that of series SW4, the ultimate failure load of specimen SW3-2 and SW4-2 was almost the same. However, the enhanced capacity of specimen SW3-2 (a/d=3) due to the addition of the CFRP reinforcement was 101 kN, while specimen SW4-2 (a/d=4) was 161 kN. This indicates that the contribution of external CFRP reinforcement may be influenced by the ayd ratio and appears to decrease with a decreasing a/d ratio. Further, for both strengthened specimens (SW3-2 and SW4-2), CFRP sheets did not fracture or debond from the concrete surface at ultimate and this indicates that CFRP could provide additional strength if the beams did not failed by splitting.3.3. Series SO3Fig. 8 illustrates the failure modes for series SO3 specimens. That details the applied load vs. mid-span deflection for the specimens.The failure mode of control specimen SO3-1 was shear compression. Failure of the specimen occurred at a total applied load of 154 kN. This load was a decrease of shear capacity by 54.5 kN compared to the specimen SW3-1 due to the absent of the steel stirrups. In addition, the crack pattern in specimen SW3-1 was different from of specimen SO3-1. In specimen SW3-1, the presence of stirrups provided a better distribution of diagonal cracks throughout the shear span.In specimen SO3-2, strengthened with 50-mm CFRP strips spaced at 125 mm, the first diagonal shear crack was observed at an applied load of 100 kN. The crack propagated as the load increased in a similar manner to that of specimen SO3-1. Sudden failure occurred due to debonding of the CFRP strips over the diagonal shear crack, with spalled concrete attached to the CFRP strips. The total ultimate load was 262 kN with a 70% increase in shear capacity over the control specimen SO3-1. The maximum local CFRP vertical strain measured at failure in specimen SO3-2 was 0.0047 mm/mm (i.e. 28% of the ultimate strain), which indicated that the CFRP did not reach its ultimate.Specimen SO3-3, strengthened with 75-mm CFRP strips failed as a result of CFRP debonding at a total applied load of 266 kN. No significant increase in shear capacity was noted compared to specimen SO3-2. The maximum-recorded vertical CFRP strain at failure was 0.0052 mmymm (i.e. 31% of the ultimate strain).Specimen SO3-4, which was strengthened with a continuous CFRP U-wrap (908), failed as a result of CFRP debonding at an applied load of 289 kN. Results show that specimen SO3-4 exhibited increase in shear capacity of 87, 10 and 8.5% over specimens SO3-1,SO3-2 and SO3-3, respectively. Applied load vs. vertical CFRP strain for specimen SO3-4 is illustrated in Fig. 10 in which strain gauges sg1, sg2 and sg3 were located at mid-height with distances of 175, 300 and 425 mm from the support, respectively. Fig. 10 shows that the CFRP strain was zero prior to diagonal crack formation, then increased slowly until the specimen reached a load in the neighborhood of theultimate strength of the control specimen. At this point, the CFRP strain increased significantly until failure. The maximum local CFRP vertical strain measured at failure was approxi- mately 0.0045 mm/mm.When comparing the results of beams SO3-4 and SO3-2, the CFRP amount used to strengthen specimen SO3-4 was 250% of that used for specimen SO3-2. Only a 10% increase in shear capacity was achieved for the additional amount of CFRP used. This means that if an end anchor to control FRP debonding is not used, there is an optimum FRP quantity, beyond which the strengthening effect is questionable. A previous study [11] showed that by using an end anchor system, the failure mode of FRP debonding could be avoided. Reported findings are consistent with those of other research [7], which was based on a review of the experimental results available in the literature, and indicated that the contribution of FRP to the shear capacity increases almost linearly, with FRP axial rigidity expressed byf f E ρ(f ρ is the FRP area fraction and f E is the FRP elastic modulus) up to approximately 0.4 GPa. Beyond this value, the effectiveness of FRP ceases to be positive.In specimen SO3-5, the use of a horizontal ply over the continuous U-wrap (i.e. 90°/0°) resulted in a concrete splitting failure rather than a CFRP debonding failure. The failure occurred at total applied load of 339 kN with a 120% increase in the shear capacity compared to the control specimen SO3-1. The strengthening with two perpendicular plies (i.e. 90°/0°) resulted in a 17% increase in shear capacity compared to the specimen with only one CFRP ply in 90° orientation (i.e. specimen SO3-4). The maximum local CFRP vertical strain measured at failure was 0.0043 mm/mm.By comparing the test results of specimens SW3-2 and SO3-5, having the same a/d ratio and strengthening schemes but with different steel shear reinforcement, the shear strength (i.e. 177 and 169.5 kN for specimens SW3-2 and SO3-5, respectively), and the ductility are almost identical. One may conclude that the contribution of CFRP benefits the beam capacity to a greater degree for beams without steel shear reinforcement than for beams with adequate shear reinforcement.3.4. Series SO4Series SO4 exhibited the largest increase in shear capacity compared to the other series investigated with this research study. The experimental results in terms of applied load vs mid-span deflection for this series is illustrated in Fig. 11.The control specimen SO4-1 failed as a result of shear compression at a total applied load of 130 kN. Specimen SO4-2, strengthened with CFRP strips, the failure was controlled by CFRP debonding at a total load of 255 kN with 96% increase in shear capacity over the control specimen SO4-1. The maximum local CFRP vertical strain measured at failure was 0.0062mmymm.When comparing the test results of specimen SO4-2 to that of specimen SO3-2, the enhanced shear capacity of specimen SO4-2 (a/d=4) due to addition of CFRP strips was 62.5 kN, while specimen SO3-2 (a/d=3) resulted in added shear capacity of 54 kN. As expected, the contribution of CFRP reinforcement to resist the shear appeared to decrease with decreasing a/d ratio. Specimen SO4-3, strengthened with continuous U- wrap, failed as a result of concrete splitting at an applied load of 310 kN with a 138% increase in shear capacity compared to that of specimen SO4-1. The maximum local CFRP vertical strain measured at failure was 0.0037 mm/mm.4. Design approachThe design approach for computing the shear capacity of RC beams strengthened with externally bonded CFRP reinforcement, expressed in ACI design code [12] format, was proposed and published in 1998 [13]. The design model described two possible failure mechanisms of CFRP reinforcement namely: CFRP fracture; and CFRP debonding. Furthermore, two limits on the contribution of CFRP shear were proposed. The first limit was set to control the shear crack width and loss of aggregate interlock, and the second was to preclude web crushing. Also, the concrete strength and CFRP wrap- ping schemes were incorporated as design parameters. In recent study [9,10], modifications were proposed to the 1998 design approach toinclude results of a new study on bond mechanism between CFRP sheets and concrete surface [14]. In addition, the model was extended to provide the shear design equations in Eurocode as well as ACI format. Comparing with all test results available in the literature to date, 76 tests, the design approach showed acceptable and conservative estimates [10,13]. In this section, the summary of the design approach is presented. The comparison between experimental results and the calculated factored shear strength demonstrates the ability of the design approach to predict the shear capacity of the strengthened beams. demonstrates the ability of the design approach to predict the shear capacity of the strengthened beams.4.1. Summary of the shear design approach — ACI formatIn traditional shear design (including the ACI Code), the nominal shear strength of an RC section is the sum of the nominal shear strengths of concrete and steel shear reinforcement. For beams strengthened with externally bonded FRP reinforcement, the shear strength may be computed by the addition of a third term to account of the FRP contribution. This is expressed as follows:The design shear strength,n Vφ, is obtained by multiplying the nominal shear strength by a strength reduction factor for shear,φ. It was suggested that the reduction factor φ=0.85 given in ACI [12] be main-tained for the concrete and steel terms. However, a more stringent strength reduction factor of 0.7 for the CFRP contribution was suggested w10x. This is due to the relative novelty of this repair technique. Thus, the design shear strength is expressed as follows.4.2. Contribution of CFRP reinforcement to the shear capacityThe expression used to compute shear contribution of CFRP reinforcement is given in Eq. (3). This equation is similar to that for shear contribution of steel stirrups and consistent with the ACI format.The area of CFRP shear reinforcement,f A , is the total thickness of the sheet (usually f t 2or sheets on both sides of the beam) times the width of the CFRP stripf ω. The dimensions used to define the area of CFRP in addition to the spacingf s and the effective depth of CFRP,f d ， are shown in Fig. 12. Note that for continuousvertical shear reinforcement, the spacing of the strip,f s , and the width of the strip,f ω, are equal.In Eq. (3), an effective average CFRP stressfe f , smaller than its ultimate strength,fu f , was used to replace the yield stress of steel. At the ultimate limit state for the member in shear, it is not possible to attain the full strength of the FRP [7,13]. Failure is governed by either fracture of the FRP sheet at average stress levels well below FRP ultimate capacity due to stress concentrations, debonding of the FRP sheet from the concrete surface, or a significant decrease in the post- cracking concrete shear strength from a loss of aggregate interlock. Thus, the effective average CFRP stress is computed by applying a reduction coefficient, R, to the CFRP ultimate strength as expressed in Eq. (4).The reduction coefficient depends on the possible failure modes (either CFRPfracture or CFRP debonding). In either case, an upper limit for the reduction coefficient is established in order to control shear crack width and loss of aggregate interlock.4.3. Reduction coefficient based on CFRP sheet fracture failureThe proposed reduction coefficient was calibrated on all available test results to date, 22 tests with failure controlled by CFRP fracture [10，13]. The reduction coefficient was established as a function of f f E ρ (where f ρis the area fraction ofCFRP) and expressed in Eq.(5) for ≤f f E ρ0.7 GPa.4.4. Reduction coefficient based on CFRP debonding failureThe shear capacity governed by CFRP debonding from the concrete surface was presented [9,10]as a function of CFRP axial rigidity, concrete strength, effective depth of CFRP reinforcement, and bonded surface configurations. In determining the reduction coefficient for bond, the effective bond length, e L , has to be determined first. Based on analytical and experimental data from bond tests, Miller [14] showed that the effective bond length slightly increases as CFRP axial rigidity,f f E t , increases. However, he suggested a constant conservative value e L for equal to 75 mm. The value may be modified when more bond tests data becomes available.After a shear crack develops, only that portion of the width of CFRP extending past the crack by the effective bonded length is assumed to be capable of carrying shear.[13] The effective width, fe W , based on the shear crack angle of 45°, and the wrapping scheme is expressed in Eqs. (6a) and (6b);if the sheet in the form of a U-wrap (6a)if the sheet is bonded only to the sides of the beam. (6b)The final expression for the reduction coefficient, R, for the mode of failure controlled by CFRP debonding is expressed in Eq. (8)Eq. (7) is applicable for CFRP axial rigidity, f f E t , ranging from 20 to 90 mm-GPa (kN/mm). Research into quantifying the bond characteristics for axial rigidities above 90 mm·GPa is being conducted at the University of Missouri, Rolla (UMR).4.5. Upper limit of the reduction coefficientIn order to control the shear crack width and loss of aggregate interlock, an upper limit of reduction coefficient, R, was suggested and calibrated with all of the availabletest results [10] to be equal to fu ε/006.0where fu εis the ultimate tensile CFRP strain. This limit is such that the average effective strain in CFRP materials at ultimate can not be greater than 0.006 mm/mm (without the strengthening reduction factor,φ).4.6. Controlling reduction coefficientThe final controlling reduction coefficient for the CFRP system is taken as the lowest value determined from the two possible modes of failure and the upper limit. Note that if the sheet is wrapped entirely around the beam or an effective end anchor is used, the failure mode of CFRP debonding is not to be considered. The reduction coefficient is only controlled by FRP fracture and the upper limit.4.7. CFRP spacing requirementsSimilar to steel shear reinforcement, and consistent with ACI provision for the stirrups spacing[12], the spacing of FRP strips should not be so wide as to allow the formation of a diagonal crack without intercepting a strip. For this reason, if strips are used, they should not be spaced by more than the maximum given in Eq. (8).4.8. Limit on total shear reinforcementACI 318M-95 [12] 11.5.6.7 and 11.5.6.8 set a limit on the total shear strength that may be provided by more than one type of shear reinforcement to preclude the web crushing. FRP shear reinforcement should be included in this limit. A modification to ACI 318M-95 Section 11.5.6.8 was suggested as follows:4.9. Shear capacity of a CFRP strengthened section — Eurocode formatThe proposed design equation wEq. (3)x for computing the contribution of externally bonded CFRP reinforcement may be rewritten in Eurocode (EC2 1992) [15] format as Eq. (10).In this equation, the partial safety factor for CFRP materials,f , was suggestedequal to 1.3 [10].5. Conclusions and further recommendation An experimental investigation was conducted to study the shear behavior and the modes of failure of simply supported rectangular section RC beams with shear deficiencies, strengthened with CFRP sheets. The parameters investigated in this program were existence of steel shear reinforcement, shear span-to-effective depth ratio (ayd ratio), and CFRP amount and distribution.The results confirm that the strengthening technique using CFRP sheets can be used to increase significantly shear capacity, with efficiency that varies depending on the tested variables. For the beams tested in this program, increases in shear strength of 40–138% were achieved.Conclusions that emerged from this study may be summarized as follows:● The contribution of externally CFRP reinforcement to the shear capacity isinfluenced by the a/d ratio.● Increasing the amount of CFRP may not result in a proportional increase in theshear strength. The CFRP amount used to strengthen specimen SO3-4 was 250% of that used in specimen SO3-2, which resulted in a minimal (10%) increase in shear capacity. An end anchor is recommended if FRP debonding is to be avoided. ● The test results indicated that contribution of CFRP benefits the shear capacity ata greater degree for beams without shear reinforcement than for beams with adequate shear reinforcement.● The results of series SO3 indicated that the 0° ply improved the shear capacity byproviding horizontal restraint.● The shear design algorithms provided acceptable and conservative estimates forthe strengthened beams. Recommendations for future research are as follows:● Experimental and analytical investigations are required to link the shearcontribution of FRP with the load condition. These studies have to consider both the longitudinal steel reinforcement ratio and the concrete strength as parameters. Laboratory specimens should maintain practical dimensions.● The strengthening effectiveness of FRP has to be addressed in the cases of shortand very short shear spans in which arch action governs failure.● The interaction between the contribution of external FRP and internal steel shearreinforcement has to be investigated.● To optimize design algorithms, additional specimens need to be tested withdifferent CFRP amount and configurations to create a large database of information.● Shear design algorithms need to be expanded to include strengthening witharamid FRP and glass FRP sheets in addition to CFRP .6. NomenclatureA: Shear spanf A :Area of CFRP shear reinforcements=2t f w fw b : Width of the beam cross-sectionD: Depth from the top of the section to the tension steel reinforcement centroidf d :Effective depth of the CFRP shear reinforcement (usually equal to d for rectangular sections and dyts for T-sections)f E :Elastic modulus of FRP (GPa)'c f :Nominal concrete compressive strength (MPa)fef :Effective tensile stress in the FRP sheet in the direction of the principal fibers (stress level in the FRP at failure)fu f :Ultimate tensile strength of the FRP sheet in the direction of the principal fibers e L :Effective bond length (mm)。
【设计】土木工程毕业设计英语论文及翻译
【关键字】设计土木工程毕业设计英语论文及翻译篇一：土木工程毕业设计外文文献翻译外文文献翻译Reinforced ConcreteConcrete and reinforced concrete are used as building materials in every country. In many, including the United States and Canada, reinforced concrete is a dominant structural material in engineered construction. 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, and the economy of reinforced concrete compared to other forms of construction. Concrete and reinforced concrete are used in bridges, buildings of all sorts underground structures, water tanks, television towers, offshore oil exploration and production structures, dams, and even in ships.Reinforced concrete structures may be cast-in-place concrete, constructed in their final location, or they may be precast concrete produced in a factory and erected at the construction site. Concrete structures may be severe and functional in design, or the shape and layout and be whimsical and artistic. Few other building materials off the architect and engineer such versatility and scope.Concrete is strong in compression but weak in tension. As a result, cracks develop whenever loads, or restrained shrinkage of temperature changes, give rise to tensile stresses in excess of the tensile strength of the concrete. In a plain concrete beam, the moments about the neutral axis due to applied loads are resisted by an internal tension-compression couple involving tension in the concrete. Such a beam fails very suddenly and completely when the first crack forms. In a reinforced concrete beam, steel bars are embedded in the concrete in such a way that the tension forces needed for moment equilibrium after the concrete cracks can be developed in the bars.The construction of a reinforced concrete member involves building a from of mold in the shape of the member being built. The form must be strong enough to support both the weight and hydrostatic pressure of the wet concrete, and any forces applied to it by workers, concrete buggies, wind, and so on. The reinforcement is placed in this form and held in place during the concreting operation. After the concrete has hardened, the forms are removed. As the forms are removed, props of shores are installed to support the weight of the concrete until it has reached sufficient strength to support the loads by itself.The designer must proportion a concrete member for adequate strength to resist the loads and adequate stiffness to prevent excessive deflections. In beam must be proportioned so that it can be constructed. For example, the reinforcement must be detailed so that it can be assembled in the field, and since the concrete is placed in the form after the reinforcement is in place, theconcrete must be able to flow around, between, and past the reinforcement to fill all parts of the form completely.The choice of whether a structure should be built of concrete, steel, masoy, or timber depends on the availability of materials and on a number of value decisions. The choice of structural system is made by the architect of engineer early in the design, based on the following considerations:1. Economy. Frequently, the foremost consideration is the overall const of the structure. This is, of course, a function of the costs of the materials and the labor necessary to erect them. Frequently, however, the overall cost is affected as much or more by the overall construction time since the contractor and owner must borrow or otherwise allocate money to carry out the construction and will not receive a return on this investment until the building is ready for occupancy. In a typical large apartment of commercial project, the cost of construction financing will be a significant fraction of the total cost. As a result, financial savings due to rapid construction may more than offset increased material costs. For this reason, any measures the designer can take to standardize the design and forming will generally pay off in reduced overall costs.In many cases the long-term economy of the structure may be more important than the first cost. As a result, maintenance and durability are important consideration.2. Suitability of material for architectural and structural function.A reinforced concrete system frequently allows the designer to combine the architectural and structural functions. Concrete has the advantage that it is placed in a plastic condition and is given the desired shapeand texture by means of the forms and the finishing techniques. This allows such elements ad flat plates or other types of slabs to serve as load-bearing elements while providing the finished floor and / or ceiling surfaces. Similarly, reinforced concrete walls can provide architecturally attractive surfaces in addition to having the ability to resist gravity, wind, or seismic loads. Finally, the choice of size of shape is governed by the designer and not by the availability of standard manufactured members.3. Fire resistance. The structure in a building must withstand the effects of a fire and remain standing while the building is evacuated and the fire is extinguished. A concrete building inherently has a 1- to 3-hour fire rating without special fireproofing or other details. Structural steel or timber buildings must be fireproofed to attain similar fire ratings.4. Low maintenance. Concrete members inherently require less maintenance than do structural steel or timber members. This is particularly true if dense, air-entrained concrete has been used for surfaces exposed to the atmosphere, and if care has been taken in the design to provide adequate drainage off and away from the structure. Special precautions must be taken for concrete exposed to salts such as deicing chemicals.5. Availability of materials. Sand, gravel, cement, and concrete mixing facilities are verywidely available, and reinforcing steel can be transported to most job sites more easily than can structural steel. As a result, reinforced concrete is frequently used in remote areas.On the other hand, there are a number of factors that may cause one to select a material other than reinforced concrete. These include:1. Low tensile strength. The tensile strength concrete is much lower than its compressive strength ( about 1/10 ), and hence concrete is subject to cracking. In structural uses this is overcome by using reinforcement to carry tensile forces and limit crack widths to within acceptable values. Unless care is taken in design and construction, however, these cracks may be unsightly or may allow penetration of water. When this occurs, water or chemicals such as road deicing salts may cause deterioration or staining of the concrete. Special design details are required in such cases. In the case of water-retaining structures, special details and / of prestressing are required to prevent leakage.2. Forms and shoring. The construction of a cast-in-place structure involves three steps not encountered in the construction of steel or timber structures. These are ( a ) the construction of the forms, ( b ) the removal of these forms, and (c) propping or shoring the new concrete to support its weight until its strength is adequate. Each of these steps involves labor and / or materials, which are not necessary with other forms of construction.3. Relatively low strength per unit of weight for volume. The compressive strength of concrete is roughly 5 to 10% that of steel, while its unit density is roughly 30% that of steel. As a result, a concrete structure requires a larger volume and a greater weight of material than does a comparable steel structure. As a result, long-span structures are often built from steel.4. Time-dependent volume changes. Both concrete and steel undergo-approximately the same amount of thermal expansion and contraction. Because there is less mass of steel to be heated or cooled, and because steel is a better concrete, a steel structure is generally affected by temperature changes to a greater extent than is a concrete structure. On the other hand, concrete undergoes frying shrinkage, which, if restrained, may cause deflections or cracking. Furthermore, deflections will tend to increase with time, possibly doubling, due to creep of the concrete under sustained loads.In almost every branch of civil engineering and architecture extensive use is made of reinforced concrete for structures and foundations. Engineers and architects requires basic knowledge of reinforced concrete design throughout their professional careers. Much of this text is directly concerned with the behavior and proportioning of components that make up typical reinforced concrete structures-beams, columns, and slabs. Once the behavior of these individual elements is understood, the designer will have the background to analyze and design a wide range of complex structures, such as foundations, buildings, and bridges, composed of these elements.Since reinforced concrete is a no homogeneous material that creeps, shrinks, and cracks, its stresses cannot be accurately predicted by the traditional equations derived in a course instrength of materials forhomogeneous elastic materials. Much of reinforced concrete design in therefore empirical, i.e., design equations and design methods are based on experimental and time-proved results instead of being derived exclusively from theoretical formulations.A thorough understanding of the behavior of reinforced concrete will allow the designer to convert an otherwise brittle material into tough ductile structural elements and thereby take advantage of concrete’s desirable characteristics, its high compressive strength, its fire resistance, and its durability.Concrete, a stone like material, is made by mixing cement, water, fine aggregate ( often sand ), coarse aggregate, and frequently other additives ( that modify properties ) into a workable mixture. In its unhardened or plastic state, concrete can be placed in forms to produce a large variety of structural elements. Although the hardened concrete by itself, i.e., without any reinforcement, is strong in compression, it lacks tensile strength and therefore cracks easily. Because ueinforced concrete is brittle, it cannot undergo large deformations under load and fails suddenly-without warning. The addition fo steel reinforcement to the concrete reduces the negative effects of its two principal inherent weaknesses, its susceptibility to cracking and its brittleness. When the reinforcement is strongly bonded to the concrete, a strong, stiff, and ductile construction material is produced. This material, called reinforced concrete, is used extensively to construct foundations, structural frames, storage takes, shell roofs, highways, walls, dams, canals, and innumerable other structures and building products. Two other characteristics of concrete that are present even when concrete is reinforced are shrinkage and creep, but the negative effects of these properties can be mitigated by careful design.A code is a set technical specifications and standards that control important details of design and construction. The purpose of codes it produce structures so that the public will be protected from poor of inadequate and construction.Two types f coeds exist. One type, called a structural code, is originated and controlled by specialists who are concerned with the proper use of a specific material or who are involved with the safe design of a particular class of structures.篇二：土木工程毕业设计中英文翻译附录：中英文翻译英文部分：LOADSLoads that act on structures are usually classified as dead loads or live loads.Dead loads are fixed in location and constant in magnitude throughout the life of the ually the self-weight of a structure is the most important part of the structure and the unit weight of the material.Concrete density varies from about 90 to 120 pcf (14 to 19 KN/m2)for lightweight concrete,and is about 145 pcf (23 KN/mKN/m2)for normal concrete.In calculating the dead load of structural concrete,usually a 5pcf (1 )increment is included with the weight of the concrete to account for the presence of the 2 reinforcement.Live loads are loads such as occupancy,snow,wind,or traffic loads,or seismic forces.They may be either fully or partially in place,or not present at all.They may also change in location.Althought it is the responsibility of the engineer to calculate dead loads,live loads are usually specified by local,regional,or national codes and specifications.Typical sources are the publications of the American National Standards Institute,the American Association of State Highway and Transportation Officials and,for wind loads,the recommendations of the ASCE Task Committee on Wind Forces.Specified live the loads usually include some allowance for overload,and may include measures such as posting of maximum loads will not be exceeded.It is oftern important to distinguish between the specified load,and what is termed the characteristic load,that is,the load that actually is in effect under normal conditions of service,which may be significantly less.In estimating the long-term deflection of a structure,for example,it is the characteristic load that is important,not the specified load.The sum of the calculated dead load and the specified live load is called the service load,because this is the maximum load which may reasonably be expected to act during the service resisting is a multiple of the service load.StrengthThe strength of a structure depends on the strength of the materials from which it is made.Minimum material strengths are specified in certain standardized ways.The properties of concrete and its components,the methods of mixing,placing,and curing to obtain the required quality,and the methods for testing,are specified by the American Concrete Insititue(ACI).Included by refrence in the same documentare standards of the American Society for Testing Materials(ASTM)pertaining to reinforcing and prestressing steels and concrete.Strength also depends on the care with which the structure is built.Member sizes may differ from specified dimensions,reinforcement may be out of position,or poor placement of concrete may result in voids.An important part of the job of the ergineer is to provide proper supervision of construction.Slighting of this responsibility has had disastrous consequences in more than one instance.Structural SafetySafety requires that the strength of a structure be adequate for all loads that may conceivably act on it.If strength could be predicted accurately and if loads were known with equal certainty,then safely could be assured by providing strength just barely in excess of the requirements of the loads.But there are many sources of uncertainty in the estimation of loads as well as in analysis,design,and construction.These uncertainties require a safety margin.In recent years engineers have come to realize that the matter of structural safety isprobabilistic in nature,and the safety provisions of many current specifications reflect this view.Separate consideration is given to loads and strength.Load factors,larger than unity,are applied to the calculated dead loads and estimated or specified service live loads,to obtain factorde loads that the member must just be capable of sustaining at incipient failure.Load factors pertaining to different types of loads vary,depending on the degree of uncertainty associated with loads of various types,and with the likelihood of simultaneous occurrence of different loads.Early in the development of prestressed concrete,the goal of prestressing was the complete elimination of concrete ternsile stress at service loads.The concept was that of an entirely new,homogeneous material that woukd remain uncracked and respond elastically up to the maximum anticipated loading.This kind of design,where the limiting tensile stressing,while an alternative approach,in which a certain amount of tensile amount of tensile stress is permitted in the concrete at full service load,is called partial prestressing.There are cases in which it is necessary to avoid all risk of cracking and in which full prestressing is required.Such cases include tanks or reservious where leaks must be avoided,submerged structures or those subject to a highly corrosive envionment where maximum protection of reinforcement must be insured,and structures subject to high frequency repetition of load where faatigue of the reinforcement may be a consideration.However,there are many cses where substantially improved performance,reduced cost,or both may be obtained through the use of a lesser amount of prestress.Full predtressed beams may exhibit an undesirable amount of upward camber because of the eccentric prestressing force,a displacement that is only partially counteracted by the gravity loads producing downward deflection.This tendency is aggrabated by creep in the concrete,which magnigies the upward displacement due to the prestress force,but has little influence on the should heavily prestressed members be overloaded and fail,they may do so in a brittle way,rather than gradually as do beams with a smaller amount of prestress.This is important from the point of view of safety,because suddenfailure without warning is dangeroud,and gives no opportunity for corrective measures to be taken.Furthermore,experience indicates that in many cases improved economy results from the use of a combination of unstressed bar steel and high strength prestressed steel tendons.While tensile stress and possible cracking may be allowed at full service load,it is also recognized that such full service load may be infrequently applied.The typical,or characteristic,load acting is likely to be the dead load plus a small fraction of the specified live load.Thus a partially predtressed beam may not be subject to tensile stress under the usual conditions of loading.Cracks may from occasionally,when the maximum load is applied,but these will close completely when that load is removed.They may be no more objectionable in prestressed structures than in ordinary reinforced.They may be no more objectionable in prestressed structures than in ordinary reinforced concrete,in which flexural cracks alwaysform.They may be considered a small price for the improvements in performance and economy that are obtained.It has been observed that reinforced concrete is but a special case of prestressed concrete in which the prestressing force is zero.The behavior of reinforced and prestressed concrete beams,as the failure load is approached,is essentially the same.The Joint European Committee on Concrete establishes threee classes of prestressed beams.Class 1:Fully prestressed,in which no tensile stress is allowed in the concrete at service load.Class 2:Partially prestressed, in which occasional temporary cracking is permitted under infrequent high loads.Class 3:Partially prestressed,in which there may be permanent cracks provided that their width is suitably limited.The choise of a suitable amount of prestress is governed by a variety of factors.These include thenature of the loading (for exmaple,highway or railroad bridged,storage,ect.),the ratio of live to dead load,the frequency of occurrence of loading may be reversed,such as in transmission poles,a high uniform prestress would result ultimate strength and in brittle failure.In such a case,partial prestressing provides the only satifactory solution.The advantages of partial prestressing are important.A smaller prestress force will be required,permitting reduction in the number of tendons and anchorages.The necessary flexural strength may be provided in such cases either by a combination of prestressed tendons and non-prestressed reinforcing bars,or by an adequate number of high-tensile tendons prestredded to level lower than the prestressing force is less,the size of the bottom flange,which is requied mainly to resist the compression when a beam is in the unloaded stage,can be reduced or eliminated altogether.This leads in turn to significant simplification and cost reduction in the construction of forms,as well as resulting in structures that are mor pleasing esthetically.Furthermore,by relaxing the requirement for low service load tension in the concrete,a significant improvement can be made in the deflection characteristics of a beam.Troublesome upward camber of the member in the unloaded stage fan be avoeded,and the prestress force selected primarily to produce the desired deflection for a particular loading condition.The behavior of partially prestressed beamsm,should they be overloaded to failure,is apt to be superior to that of fully prestressed beams,because the improved ductility provides ample warning of distress.英译汉：荷载作用在结构上的荷载通常分为恒载或活载。
土木工程专业毕业设计外文翻译
Building construction concrete crack of prevention and processingAbstractThe crack problem of concrete is a widespread existence but again difficult in solve of engineering actual problem, this text carried on a study analysis to a little bit familiar crack problem in the concrete engineering, and aim at concrete the circumstance put forward some prevention, processing measure. Keyword:Concrete crack prevention processing ForewordConcrete's ising 1 kind is anticipate by the freestone bone, cement, water and other mixture but formation of the in addition material of quality brittleness not and all material.Because the concrete construction transform with oneself, control etc. a series problem, harden model of in the concrete existence numerous tiny hole, spirit cave and tiny crack, is exactly because these beginning start blemish of existence just make the concrete present one some not and all the characteristic of quality.The tiny crack is a kind of harmless crack and accept concrete heavy, defend Shen and a little bit other use function not a creation to endanger.But after the concrete be subjected to lotus carry, difference in temperature etc. function, tiny crack would continuously of expand with connect, end formation we can see without the aid of instruments of macro view the crack be also the crack that the concrete often say in the engineering. Concrete building and Gou piece usually all take sewer to make of, because of crack of existence and development usually make inner part of reinforcing bar etc. material creation decay, lower reinforced concrete material of loading ability, durable and antiShen ability, influence building of external appearance, service life, severity will threat arrive people's life and property safety.A lot of all of crash of engineerings is because of the unsteady development of the crack with the result that.Modern age science research with a great deal of of the concrete engineering practice certificate, in the concrete engineering crack problem is ineluctable, also acceptable in certainly of the scope just need to adopt valid of measure will it endanger degree control at certain of scope inside.The reinforced concrete norm is also explicit provision:Some structure at place of dissimilarity under the condition allow existence certain the crack of width.But at under construction should as far as possible adopt a valid measure control crack creation, make the structure don't appear crack possibly or as far as possible decrease crack of amount and width, particularly want to as far as possible avoid harmful crack of emergence, insure engineering quality thus. Concrete crack creation of the reason be a lot of and have already transformed to cause of crack:Such as temperature variety, constringency, inflation, the asymmetry sink to sink etc. reason cause of crack;Have outside carry the crack that the function cause;Protected environment not appropriate the crack etc. caused with chemical effect.Want differentiation to treat in the actual engineering, work°out a problem according to the actual circumstance. In the concrete engineering the familiar crack and the prevention 1.Stem Suo crack and prevention Stem the Suo crack much appear after the concrete protect be over of a period of time or concrete sprinkle to build to complete behind of around a week.In the cement syrup humidity of evaporate would creation stem Suo, and this kind of constringency is can't negative.Stem Suo crack of the creation be main is because of concrete inside outside humidity evaporate degree dissimilarity but cause to transform dissimilarity of result:The concrete is subjected to exterior condition of influence, surface humidity loss lead quick, transform bigger, inner part degree of humidity variety smaller transform smaller, bigger surface stem the Suo transform to be subjected to concrete inner part control, creation more big pullshould dint but creation crack.The relative humidity is more low, cement syrup body stem Suo more big, stem the Suo crack be more easy creation.Stem the Suo crack is much surface parallel lines form or the net shallow thin crack, width many between 0.05-0.2 mm, the flat surface part much see in the big physical volume concrete and follow it more in thinner beam plank short to distribute.Stem Suo crack usually the anti- Shen of influence concrete, cause the durable of the rust eclipse influence concrete of reinforcing bar, under the function of the water pressure dint would creation the water power split crack influence concrete of loading dint etc..Concrete stem the Suo be main with water ash of the concrete ratio, the dosage of the composition, cement of cement, gather to anticipate of the dosage of the property and dosage, in addition etc. relevant. Main prevention measure:While being to choose to use the constringency quantity smaller cement, general low hot water mire and powder ash from stove cement in the adoption, lower the dosage of cement.Two is a concrete of stem the Suo be subjected to water ash ratio of influence more big, water ash ratio more big, stem Suo more big, so in the concrete match the ratio the design should as far as possible control good water ash ratio of choose to use, the Chan add in the meantime accommodation of reduce water.Three is strict control concrete mix blend with under construction of match ratio, use of concrete water quantity absolute can't big in match ratio design give settle of use water quantity.Four is the earlier period which strengthen concrete to protect, and appropriate extension protect of concrete time.Winter construction want to be appropriate extension concrete heat preservation to overlay time, and Tu2 Shua protect to protect.Five is a constitution the accommodation is in the concrete structure of the constringency sew. 2.The Su constringency crack and prevention Su constringency is the concrete is before condense, surface because of lose water quicker but creation of constringency.The Su constringency crack is general at dry heat or strong wind the weather appear, crack's much presenting in the center breadth, both ends be in the centerthin and the length be different, with each other not coherent appearance.Shorter crack general long 20-30 cm, the longer crack can reach to a 2-3 m, breadth 1-5 mm.It creation of main reason is:The concrete is eventually almost having no strength or strength before the Ning very small, perhaps concrete just eventually Ning but strength very hour, be subjected to heat or compare strong wind dint of influence, the concrete surface lose water to lead quick, result in in the capillary creation bigger negative press but make a concrete physical volume sharply constringency, but at this time the strength of concrete again can't resist itsconstringency, therefore creation cracked.The influence concrete Su constringency open the main factor of crack to have water ash ratio, concrete of condense time, environment temperature, wind velocity, relative humidity……etc.. Main prevention measure:One is choose to use stem the Suo value smaller higher Huo sour salt of the earlier period strength or common the Huo sour brine mire.Two is strict the control water ash ratio, the Chan add to efficiently reduce water to increment the collapse of concrete fall a degree and with easy, decrease cement and water of dosage.Three is to sprinkle before building concrete, water basic level and template even to soak through.Four is in time to overlay the perhaps damp grass mat of the plastics thin film, hemp slice etc., keep concrete eventually before the Ning surface is moist, perhaps spray to protect etc. to carry on protect in the concrete surface.Five is in the heat and strong wind the weather to want to establish to hide sun and block breeze facilities, protect in time. 3.Sink to sink crack and prevention The creation which sink to sink crack is because of the structure foundation soil quality not and evenly, loose soft or return to fill soil dishonest or soak in water but result in theasymmetry sink to decline with the result that;Perhaps because of template just degree shortage, the template propped up to once be apart from big or prop up bottom loose move etc. to cause, especially at winter, the template prop up at jelly soil up, jelly the soil turn jelly empress creation asymmetry to sink to decline and cause concrete structure creation crack.This kind crack many is deep enter or pierce through sex crack, it alignment have something to do with sinking to sink a circumstance, general follow with ground perpendicular or present 30 °s-45 °Cape direction development, bigger sink to sink crack, usually have certain of wrong, crack width usually with sink to decline quantity direct proportion relation.Crack width under the influence of temperature variety smaller.The foundation after transform stability sink to sink crack also basic tend in stability. Main prevention measure:One is rightness loose soft soil, return to fill soil foundation a construction at the upper part structure front should carry on necessity of Hang solid with reinforce.Two is the strength that assurance template is enough andjust degree, and prop up firm, and make the foundation be subjected to dint even.Three is keep concrete from sprinkle infusing the foundation in the process is soak by water.Four is time that template tore down to can't be too early, and want to notice to dismantle a mold order of sequence.Five is at jelly soil top take to establish template to notice to adopt certain of prevention measure. 4.Temperature crack and prevention Temperature crack much the occurrence is in big surface or difference in temperature variety of the physical volume concrete compare the earth area of the concrete structure.Concrete after sprinkling to build, in the hardening the process, cement water turn a creation a great deal of of water turn hot, .(be the cement dosage is in the 350-550 kg/m 3, each sign square the rice concrete will release a calories of 17500-27500 kJ and make concrete internal thus the temperature rise to reach to 70 ℃or so even higher)Because the physical volume of concrete be more big, a great deal of of water turn hot accumulate at the concrete inner part but not easy send forth, cause inner part the temperature hoick, but the concrete surface spread hot more quick, so formation inside outside of bigger difference in temperature, the bigger difference in temperature result in inner part and exterior hot the degree of the bulge cold Suo dissimilarity, make concrete surface creation certain of pull should dint.When pull should dint exceed the anti- of concrete pull strength extreme limit, concrete surface meeting creation crack, this kind of crack much occurrence after the concrete under construction period.In the concrete of under construction be difference in temperature variety more big, perhaps is a concrete to be subjected to assault of cold wave etc., will cause concrete surface the temperature sharply descend, but creation constringency, surface constringency of the concrete be subjected to inner part concrete of control, creation very big of pull should dint but creation crack, this kind of crack usually just in more shallow scope of the concrete surface creation. The alignment of the temperature crack usually none settle regulation, big area structure the crack often maneuver interleave;The size bigger structure of the beam plank length, the crack run parallel with short side more;Thorough with pierce through sex of temperature crack general and short side direction parallelism or closeparallelism, crack along long side cent the segment appear, in the center more airtight.Crack width the size be different, be subjected to temperature variety influence more obvious, winter compare breadth, summer more narrow.The concrete temperature crack that the heat inflation cause is usually in the center the thick both ends be thin, but cold Suo crack of thick thin variety not too obvious.The emergence of the this kind crack will cause the rust eclipse of reinforcing bar, the carbonization of concrete, the anti- jelly which lower concrete melt, anti- tired and anti- Shenability etc.. Main prevention measure:One is as far as possible choose to use low hot or medium hot water mire, like mineral residue cement, powder ash from stove cement……etc..Two is a decrease cement dosage, cement dosage as far as possible the control is in the 450 kg/m 3 following.Three is to lower water ash ratio, water ash of the general concrete ratio control below 0.6.Four is improvement the bone anticipate class to go together with, the Chan add powder ash from stove or efficiently reduce water etc. to come to reduce cement dosage and lower water to turn hot.Five is an improvement concrete of mix blend to process a craft, lower sprinkle of concrete to build temperature.Six is the in addition that the Chan add a have of fixed amount to reduce water and increase Su, slow Ning etc. function in the concrete, improvement the concrete mix to match a thing of mobility, protect water, lower water to turn hot, postpone hot Feng of emergence time.Seven is the heat season sprinkle to build can the adoption take to establish to hide sun plank etc. assistance measure control concrete of Wen Sheng, lowBuilding construction concrete crack of prevention and processingAbstractThe crack problem of concrete is a widespread existence but again difficult in solve of engineering actual problem, this text carried on a study analysis to a little bit familiar crack problem in the concrete engineering, and aim at concrete the circumstance put forward some prevention, processing measure. Keyword:Concrete crack prevention processing ForewordConcrete's ising 1 kind is anticipate by the freestone bone, cement, water and other mixture but formation of the in addition material of quality brittleness not and all material.Because the concrete construction transform with oneself, control etc. a series problem, harden model of in the concrete existence numerous tiny hole, spirit cave and tiny crack, is exactly because these beginning start blemish of existence just make the concrete present one some not and all the characteristic of quality.The tiny crack is a kind of harmless crack and accept concrete heavy, defend Shen and a little bit other use function not a creation to endanger.But after the concrete be subjected to lotus carry, difference in temperature etc. function, tiny crack would continuously of expand with connect, end formation we can see without the aid of instruments of macro view the crack be also the crack that the concrete often say in the engineering. Concrete building and Gou piece usually all take sewer to make of, because of crack of existence and development usually make inner part of reinforcing bar etc. material creation decay, lower reinforced concrete material of loading ability, durable and antiShen ability, influence building of external appearance, service life, severity will threat arrive people's life and property safety.A lot of all of crash of engineerings is because of the unsteady development of the crack with the result that.Modern age science research with a great deal of of the concrete engineering practice certificate, in the concrete engineering crack problem is ineluctable, also acceptable in certainly of the scope just need to adopt valid of measure will it endanger degree control at certain of scope inside.The reinforced concrete norm is also explicit provision:Some structure at place of dissimilarity under the condition allow existence certain the crack of width.But at under construction should as far as possible adopt a valid measure control crack creation, make the structure don't appear crack possibly or as far as possible decrease crack of amount and width, particularly want to as far as possible avoid harmful crack of emergence, insure engineering quality thus. Concrete crack creation of the reason be a lot of and have already transformed to cause of crack:Such as temperature variety, constringency, inflation, the asymmetry sink to sink etc. reason cause ofcrack;Have outside carry the crack that the function cause;Protected environment not appropriate the crack etc. caused with chemical effect.Want differentiation to treat in the actual engineering, work°out a problem according to the actual circumstance. In the concrete engineering the familiar crack and the prevention 1.Stem Suo crack and prevention Stem the Suo crack much appear after the concrete protect be over of a period of time or concrete sprinkle to build to complete behind of around a week.In the cement syrup humidity of evaporate would creation stem Suo, and this kind of constringency is can't negative.Stem Suo crack of the creation be main is because of concrete inside outside humidity evaporate degree dissimilarity but cause to transform dissimilarity of result:The concrete is subjected to exterior condition of influence, surface humidity loss lead quick, transform bigger, inner part degree of humidity variety smaller transform smaller, bigger surface stem the Suo transform to be subjected to concrete inner part control, creation more big pull should dint but creation crack.The relative humidity is more low, cement syrup body stem Suo more big, stem the Suo crack be more easy creation.Stem the Suo crack is much surface parallel lines form or the net shallow thin crack, width many between 0.05-0.2 mm, the flat surface part much see in the big physical volume concrete and follow it more in thinner beam plank short to distribute.Stem Suo crack usually the anti- Shen of influence concrete, cause the durable of the rust eclipse influence concrete of reinforcing bar, under the function of the water pressure dint would creation the water power split crack influence concrete of loading dint etc..Concrete stem the Suo be main with water ash of the concrete ratio, the dosage of the composition, cement of cement, gather to anticipate of the dosage of the property and dosage, in addition etc. relevant. Main prevention measure:While being to choose to use the constringency quantity smaller cement, general low hot water mire and powder ash from stove cement in the adoption, lower the dosage of cement.Two is a concrete of stem the Suo be subjected to water ash ratio of influence more big, water ash ratio more big, stem Suo more big, so in the concrete match the ratio the design should as far as possible control good water ash ratio of choose to use, the Chan add in the meantime accommodation of reduce water.Three is strict control concrete mix blend with under construction of match ratio, use of concrete water quantity absolute can't big in match ratio design give settle of use water quantity.Four is the earlier period which strengthen concrete to protect, and appropriate extension protect of concrete time.Winter construction want to be appropriate extension concrete heat preservation to overlay time, and Tu2 Shua protect to protect.Five is a constitution the accommodation is in the concrete structure of the constringency sew. 2.The Su constringency crack and prevention Su constringency is the concrete is before condense, surface because of lose water quicker but creation of constringency.The Su constringency crack is general at dry heat or strong wind the weather appear, crack's much presenting in the center breadth, both ends be in the centerthin and the length be different, with each other not coherent appearance.Shorter crack general long 20-30 cm, the longer crack can reach to a 2-3 m, breadth 1-5 mm.It creation of main reason is:The concrete is eventually almost having no strength or strength before the Ning very small, perhaps concrete just eventually Ning but strength very hour, be subjected to heat or compare strong wind dint of influence, the concrete surface lose water to lead quick, result in in the capillary creation bigger negative press but make a concrete physical volume sharply constringency, but at this time the strength of concrete again can't resist itsconstringency, therefore creation cracked.The influence concrete Su constringency open the main factor of crack to have water ash ratio, concrete of condense time, environment temperature,wind velocity, rela tive humidity……etc.. Main prevention measure:One is choose to use stem the Suo value smaller higher Huo sour salt of the earlier period strength or common the Huo sour brine mire.Two is strict the control water ash ratio, the Chan add to efficiently reduce water to increment the collapse of concrete fall a degree and with easy, decrease cement and water of dosage.Three is to sprinkle before building concrete, water basic level and template even to soak through.Four is in time to overlay the perhaps damp grass mat of the plastics thin film, hemp slice etc., keep concrete eventually before the Ning surface is moist, perhaps spray to protect etc. to carry on protect in the concrete surface.Five is in the heat and strong wind the weather to want to establish to hide sun and block breeze facilities, protect in time. 3.Sink to sink crack and prevention The creation which sink to sink crack is because of the structure foundation soil quality not and evenly, loose soft or return to fill soil dishonest or soak in water but result in the asymmetry sink to decline with the result that;Perhaps because of template just degree shortage, the template propped up to once be apart from big or prop up bottom loose move etc. to cause, especially at winter, the template prop up at jelly soil up, jelly the soil turn jelly empress creation asymmetry to sink to decline and cause concrete structure creation crack.This kind crack many is deep enter or pierce through sex crack, it alignment have something to do with sinking to sink a circumstance, general follow with ground perpendicular or present 30 °s-45 °Cape direction development, bigger sink to sink crack, usually have certain of wrong, crack width usually with sink to decline quantity direct proportion relation.Crack width under the influence of temperature variety smaller.The foundation after transform stability sink to sink crack also basic tend in stability. Main prevention measure:One is rightness loose soft soil, return to fill soil foundation a construction at the upper part structure front should carry on necessity of Hang solid with reinforce.Two is the strength that assurance template is enough andjust degree, and prop up firm, and make the foundation be subjected to dint even.Three is keep concrete from sprinkle infusing the foundation in the process is soak by water.Four is time that template tore down to can't be too early, and want to notice to dismantle a mold order of sequence.Five is at jelly soil top take to establish template to notice to adopt certain of prevention measure. 4.Temperature crack and prevention Temperature crack much the occurrence is in big surface or difference in temperature variety of the physical volume concrete compare the earth area of the concrete structure.Concrete after sprinkling to build, in the hardening the process, cement water turn a creation a great deal of of water turn hot, .(be the cement dosage is in the 350-550 kg/m 3, each sign square the rice concrete will release a calories of 17500-27500 kJ and make concrete internal thus the temperature rise to reach to 70 ℃or so even higher)Because the physical volume of concrete be more big, a great deal of of water turn hot accumulate at the concrete inner part but not easy send forth, cause inner part the temperature hoick, but the concrete surface spread hot more quick, so formation inside outside of bigger difference in temperature, the bigger difference in temperature result in inner part and exterior hot the degree of the bulge cold Suo dissimilarity, make concrete surface creation certain of pull should dint.When pull should dint exceed the anti- of concrete pull strength extreme limit, concrete surface meeting creation crack, this kind of crack much occurrence after the concrete under construction period.In the concrete of under construction be difference in temperature variety more big, perhaps is a concrete to be subjected to assault of cold wave etc., will cause concrete surface the temperature sharply descend, but creation constringency, surface constringency of the concrete be subjected to inner part concrete of control, creation very big of pull should dint but creation crack, this kind of crackusually just in more shallow scope of the concrete surface creation. The alignment of the temperature crack usually none settle regulation, big area structure the crack often maneuver interleave;The size bigger structure of the beam plank length, the crack run parallel with short side more;Thorough with pierce through sex of temperature crack general and short side direction parallelism or closeparallelism, crack along long side cent the segment appear, in the center more airtight.Crack width the size be different, be subjected to temperature variety influence more obvious, winter compare breadth, summer more narrow.The concrete temperature crack that the heat inflation cause is usually in the center the thick both ends be thin, but cold Suo crack of thick thin variety not too obvious.The emergence of the this kind crack will cause the rust eclipse of reinforcing bar, the carbonization of concrete, the anti- jelly which lower concrete melt, anti- tired and anti- Shen ability etc.. Main prevention measure:One is as far as possible choose to use low hot or medium hot water mire, like mineral residue cement, powder ash from stove cement……etc..Two is a decrease cement dosage, cement dosage as far as possible the control is in the 450 kg/m 3 following.Three is to lower water ash ratio, water ash of the general concrete ratio control below 0.6.Four is improvement the bone anticipate class to go together with, the Chan add powder ash from stove or efficiently reduce water etc. to come to reduce cement dosage and lower water to turn hot.Five is an improvement concrete of mix blend to process a craft, lower sprinkle of concrete to build temperature.Six is the in addition that the Chan add a have of fixed amount to reduce water and increase Su, slow Ning etc. function in the concrete, improvement the concrete mix to match a thing of mobility, protect water, lower water to turn hot, postpone hot Feng of emergence time.Seven is the heat season sprinkle to build can the adoption take to establish to hide sun plank etc. assistance measure control concrete of Wen Sheng, lower to sprinkle temperature of build the concrete.Eight is the temperature of big physical volume concrete should the dint relate to structure size, concrete structure size more big, temperature should dint more big, so want reasonable arrangement construction work preface, layering, cent the piece sprinkle to build, for the convenience of in spread hot, let up control.Nine is at great inner part constitution of the physical volume concrete cool off piping, cold water perhaps cold air cool off, let up concrete of inside outside difference in temperature.Ten is the supervision which strengthen concrete temperature, adopt to cool off in time, protection measure.11 is to reserve temperature constringency to sew.12 is to let up to control, sprinkle proper before building concrete in the Ji rock and old concrete top build a 5 mm or so sand mat a layer or usage asphalt etc. material Tu2 Shua.13 is to strengthen concrete to protect, the concrete after sprinkle build use moist grass Lian in time, hemp slice's etc. overlay, and attention sprinkle water to protect, appropriate extension protect time, assurance the concrete surface be slow-moving cool off.At the cold season, concrete surface should constitution heat preservation measure, in order to prevent cold wave assault.14 is the allocation be a little amount in the concrete of reinforcing bar perhaps add fiber material concrete of temperature crack control at certain of scope inside. 5.Crack and prevention that the chemical reaction cause Alkali bone's anticipating the crack that reaction crack and reinforcing bar rust eclipse cause is the most familiar in the reinforced concrete structure of because of chemical reaction but cause of crack. The concrete blend a future reunion creation some alkalescence ion, these ion with some activity the bone anticipate creation chemical reaction and absorb surroundings environment in of water but the physical volume enlarge, make concrete crisp loose, inflation open crack.In this kind of crack general emergence concrete structure usage。
土木工程毕业设计中英文翻译.doc
附录：中英文翻译英文部分：LOADSLoads that act on structures are usually classified as dead loads or live loads.Dead loads are fixed in location and constant in magnitude throughout the life of the ually the self-weight of a structure is the most important part of the structure and the unit weight of the material.Concrete density varies from about 90 to 120 pcf (14 to 19 2KN/m)for lightweight concrete,and is about 145 pcf (23 2KN/m)for normal concrete.In calculating the dead load of structural concrete,usually a 5 pcf (1 2KN/m)increment is included with the weight of the concrete to account for the presence of the reinforcement.Live loads are loads such as occupancy,snow,wind,or traffic loads,or seismic forces.They may be either fully or partially in place,or not present at all.They may also change in location.Althought it is the responsibility of the engineer to calculate dead loads,live loads are usually specified by local,regional,or national codes and specifications.Typical sources are the publications of the American National Standards Institute,the American Association of State Highway and Transportation Officials and,for wind loads,the recommendations of the ASCE Task Committee on Wind Forces.Specified live the loads usually include some allowance for overload,and may include measures such as posting of maximum loads will not be exceeded.It is oftern important to distinguish between the specified load,and what is termed the characteristic load,that is,the load that actually is in effect under normal conditions of service,which may be significantly less.In estimating the long-term deflection of a structure,for example,it is the characteristic load that is important,not the specified load.The sum of the calculated dead load and the specified live load is called the service load,because this is the maximum load which may reasonably be expected to act during the service resisting is a multiple of the service load.StrengthThe strength of a structure depends on the strength of the materials from which it is made.Minimum material strengths are specified in certain standardized ways.The properties of concrete and its components,the methods of mixing,placing,and curing to obtain the required quality,and the methods for testing,are specified by the American Concrete Insititue(ACI).Included by refrence in the same documentare standards of the American Society for Testing Materials(ASTM)pertaining to reinforcing and prestressing steels and concrete.Strength also depends on the care with which the structure is built.Member sizes may differ from specified dimensions,reinforcement may be out of position,or poor placement of concrete may result in voids.An important part of the job of the ergineer is to provide proper supervision of construction.Slighting of this responsibility has had disastrous consequences in more than one instance.Structural SafetySafety requires that the strength of a structure be adequate for all loads that may conceivably act on it.If strength could be predicted accurately and if loads were known with equal certainty,then safely could be assured by providing strength just barely in excess of the requirements of the loads.But there are many sources of uncertainty in the estimation of loads as well as in analysis,design,and construction.These uncertainties require a safety margin.In recent years engineers have come to realize that the matter of structural safety is probabilistic in nature,and the safety provisions of many current specifications reflect this view.Separate consideration is given to loads and strength.Load factors,larger than unity,are applied to the calculated dead loads and estimated or specified service live loads,to obtain factorde loads that the member must just be capable of sustaining at incipient failure.Load factors pertaining to different types of loads vary,depending on the degree of uncertainty associated with loads of various types,and with the likelihood of simultaneous occurrence of different loads.Early in the development of prestressed concrete,the goal of prestressing was the complete elimination of concrete ternsile stress at service loads.The concept was that of an entirely new,homogeneous material that woukd remain uncracked and respond elastically up to the maximum anticipated loading.This kind of design,where the limiting tensile stressing,while an alternative approach,in which a certain amount of tensile amount of tensile stress is permitted in the concrete at full service load,is called partial prestressing.There are cases in which it is necessary to avoid all risk of cracking and in which full prestressing is required.Such cases include tanks or reservious where leaks must be avoided,submerged structures or those subject to a highly corrosive envionment where maximum protection of reinforcement must be insured,and structures subject to high frequency repetition of load where faatigue of the reinforcement may be a consideration.However,there are many cses where substantially improved performance,reduced cost,or both may be obtained through the use of a lesser amount of prestress.Full predtressed beams may exhibit an undesirable amount of upward camber because of the eccentric prestressing force,a displacement that is only partially counteracted by the gravity loads producing downward deflection.This tendency is aggrabated by creep in the concrete,which magnigies the upward displacement due to the prestress force,but has little influence on the should heavily prestressed members be overloaded and fail,they may do so in a brittle way,rather than gradually as do beams with a smaller amount of prestress.This is important from the point of view of safety,because suddenfailure without warning is dangeroud,and gives no opportunity for corrective measures to be taken.Furthermore,experience indicates that in many cases improved economy results from the use of a combination of unstressed bar steel and high strength prestressed steel tendons.While tensile stress and possible cracking may be allowed at full service load,it is also recognized that such full service load may be infrequently applied.The typical,or characteristic,load acting is likely to be the dead load plus a small fraction of the specified live load.Thus a partially predtressed beam may not be subject to tensile stress under the usual conditions of loading.Cracks may from occasionally,when the maximum load is applied,but these will close completely when that load is removed.They may be no more objectionable in prestressed structures than in ordinary reinforced.They may be no more objectionable in prestressed structures than in ordinary reinforced concrete,in which flexural cracks always form.They may be considered a small price for the improvements in performance and economy that are obtained.It has been observed that reinforced concrete is but a special case of prestressed concrete in which the prestressing force is zero.The behavior of reinforced and prestressed concrete beams,as the failure load is approached,is essentially the same.The Joint European Committee on Concrete establishes threee classes of prestressed beams.Class 1:Fully prestressed,in which no tensile stress is allowed in the concrete at service load.Class 2:Partially prestressed, in which occasional temporary cracking is permitted under infrequent high loads.Class 3:Partially prestressed,in which there may be permanent cracks provided that their width is suitably limited.The choise of a suitable amount of prestress is governed by a variety of factors.These include thenature of the loading (for exmaple,highway or railroad bridged,storage,ect.),the ratio of live to dead load,the frequency of occurrence of loading may be reversed,such as in transmission poles,a high uniform prestress would result ultimate strength and in brittle failure.In such a case,partial prestressing provides the only satifactory solution.The advantages of partial prestressing are important.A smaller prestress force will be required,permitting reduction in the number of tendons and anchorages.The necessary flexural strength may be provided in such cases either by a combination of prestressed tendons and non-prestressed reinforcing bars,or by an adequate number of high-tensile tendons prestredded to level lower than the prestressing force is less,the size of the bottom flange,which is requied mainly to resist the compression when a beam is in the unloaded stage,can be reduced or eliminated altogether.This leads in turn to significant simplification and cost reduction in the construction of forms,as well as resulting in structures that are mor pleasing esthetically.Furthermore,by relaxing the requirement for low service load tension in the concrete,a significant improvement can be made in the deflection characteristics of a beam.Troublesome upward camber of the member in the unloaded stage fan be avoeded,and the prestress force selected primarily to produce the desired deflection for a particular loading condition.The behavior of partially prestressed beamsm,should they be overloaded to failure,is apt to be superior to that of fully prestressed beams,because the improved ductility provides ample warning of distress.英译汉：荷 载作用在结构上的荷载通常分为恒载或活载。
土木工程专业毕业设计外文翻译
High-Rise BuildingsIn troducti onIt is difficult to defi ne a high-rise buildi ng . One may say that a low-rise build ing ranges from 1 to 2 stories . A medium-rise buildi ng p robably ran ges betwee n 3 or 4 stories up to 10or 20 stories or more .Although the basic principles of vertical and horiz on tal subsystem desig n rema in the samefor low- , medium- , or high-rise build ings , whe n a build ing gets high the verticalsubsystemsbecome a con trolli ng p roblem for two reas ons . Higher vertical loads will requirelarger colu mns , walls , and shafts . But , more sig nifica ntly , the overtur ning mome nt and theshear deflect ions p roduced by lateral forces are much larger and must be carefully pro vided for .The vertical subsystems in a high-rise buildi ng tran smit accumulated gravity load from storyto story , thus requiri ng larger colu mn or wall secti ons to support such loadi ng .In additi onthese same vertical subsystems must tran smit lateral loads , such as wi nd or seismic loads , tothe foun datio ns. However , in con trast to vertical load , lateral load effects on build ings arenot lin ear and in crease rap idly with in crease in height . For example under wind load , theoverturning moment at the base of buildings varies approximately as the square of a buildings mayvary as the fourth power of buildings height , other things being equal. Earthquake produces an evenmore pronoun ced effect.When the structure for a low-or medium-rise building is designed for dead and live load , it isalmost an in here nt property that the colu mns , walls , and stair or elevator shafts can carrymost of the horiz on tal forces . The p roblem is p rimarily one of shear resista nee . Moderateadditi on braci ng for rigid frames in easily be pro vided by filli ng certa in pan els ( or eve n“short ” buildi all pan els ) without in creas ing the sizes of the colu mns and girders otherwise required forvertical loads.Unfortunately , this is not is for high-rise buildings because the problem is p rimarily resistanee to mome nt and deflect ion rather tha n shear alone . Sp ecial structural arra ngeme nts will often have to be made and additi onal structural material is always required for the columns , girders ,walls , and slabs in order to made a high-rise buildi ngs sufficie ntly resista nt to much higherlateral deformati ons .As p reviously men ti oned , the qua ntity of structural material required per square foot offloor of a high-rise buildings is in excess of that required for low-rise buildings . The verticalcomponents carrying the gravity load , such as walls , columns , and shafts , will need to bestrengthened over the full height of the build ings . But qua ntity of material required for resisting lateral forces is eve n more sig nifica nt .With rei nforced con crete , the qua ntity of material also in creases as the nu mber ofstories in creases . But here it should be no ted that the in crease in the weight of material addedfor gravity load is much more sizable tha n steel , whereas for windIn crease the effective width of the mome nt-resisti ng subsystems . This is very usefulbecause in creas ing the width will cut dow n the overtur n force directly and willreduce deflecti on by the third po wer of the width in crease , other things rema iningcin sta nt . However , this does require that vertical components of the widenedsubsystem be suitably connected to actually gain this ben efit.Desig n subsystemssuch that the components are made to in teract in the most efficientmanner . For example , use truss systems with chords and diagonals efficiently stressed ,place reinforcing for walls at critical locati ons , and op timize stiff ness ratios for rigid frames .In crease the material in the most effective resist ing components . For exa mple ,materials added in the lower floors to the flan ges of colu mns and conn ect ing girderswill directly decrease the overall deflect ion and in crease the mome nt resista neewithout con tribut ing mass in the upper floors where the earthquake p roblem isaggravated .Arrange to have the greater part of vertical loads be carried directly on the primarymoment-resisting components . This will help stabilize the build ings aga inst ten sileovertu rning forces by p reco mp ress in gthe major overturn-resisti ng components .The local shear in each story can be best resisted by strategic pl aceme nt if solid wallsor the use of diagonal members in a vertical subsystem . Resist ing these shears solelyby vertical members in bending is usually less econo mical , since achiev ing sufficient bending resista nee in the colu mns and conn ect ing girders will require morematerial and con struct ion en ergy tha n using walls or diago nal members .Sufficie nt horiz on tal dia phragm acti on should be pro vided floor . This will help tobring the various resist ing eleme nts to work together in stead of sep arately .Create mega-frames by joining large vertical and horizontal components such as two or moreelevator shafts at multistory intervals with a heavy floor subsystems , or by use of verydee p girder trusses .Remember that all high-rise build ings are esse ntially vertical can tilevers which aresupported at the ground . When the above principles are judiciously applied , structurally desirable schemes can be obta ined by walls , cores , rigid frames, tubular con struct ion , and othervertical subsystems to achieve horiz on tal stre ngth and rigidity . Some of these app licati ons will now be described in subseque nt secti ons in the followi ng .Shear-Wall SystemsWhen shear walls are comp atible with other fun cti onal requireme nts , they can beeconomically utilized to resist lateral forces in high-rise buildings . For example , ap artme nt build ings n aturally require many sep arati on walls . Whe n some of these are desig ned to be load the in crease for lateral force resista nee is not that much more since the weight of a concrete buildings helps to resist overturn . On the other hand , the problem of desig n for earthquake forces . Additi onal mass in the upper floors will give rise to a greater overall lateral force un der the of seismic effects .In the case of either concrete or steel design , there are certain basic principles for pro vid ing additi onal resista nee to lateral to lateral forces and deflecti ons in high-rise build ings without too much sacrifire in economy .1.2. 3. 4. 5. 6. 7.solid , they can act as shear walls to resist lateral forces and to carry the vertical load aswell . For buildi ngs up to some 20storise , the use of shear walls is com mon .If give n sufficie nt len gth ,such walls can econo mically resist lateral forces up to 30 to 40 stories or more .However , shear walls can resist lateral load only the plane of the walls ( i.e .not in adireti on perpen dicular to them ) . There fore ,it is always n ecessary to pro vide shear walls in two perpen dicular directi ons can be at least in sufficie nt orie ntati on so that lateral force in any direct ion can be resisted .In additi on , that wall layout should reflect con siderati on of any torsi onal effect .In desig n p rogress , two or more shear walls can be conn ected to from L-sha ped or cha nnel-sha ped subsystems .In deed ‘internal shear walls can be conn ected to from a rectangular shaft that will resist lateral forces very efficiently . If all external shear walls are continuously connected , then the whole buildings acts as tube , and conn ected , the n the whole buildi ngs acts as a tube , and is excelle nt Shear-Wall Seystems resist ing lateral loads and torsi on .Whereas con crete shear walls are gen erally of solid type with openings whe n necessary, steel shear walls are usually made of trusses . These trusses can have single diagonals , “X” diagona|sor “ K” arrang e nhs . A trussed wall will have its members act esse ntially in direct tension or comp ressi on un der the acti on of view , and they offer some opportunity anddeflection-limitation point of view , and they offer some opportunity for penetration between members . Of course , the inclined members of trusses must be suitable p laced so as not to in terfere with requireme nts for wion dows and for circulati on service pen etrati ons though these walls .As stated above , the walls of elevator , staircase ,and utility shafts form n atural tubes and are com monly empio yed to resist both vertical and lateral forces . Since these shafts are no rmally recta ngular or circular in cross-sect ion , they can offer an efficie nt means for resist ing mome nts and shear in all directi ons due to tube structural action . But a p roblem in the desig n of these shafts is pro vided sufficie nt stre ngth around door openings and other pen etrati ons through these eleme nts . For rein forced concrete construction , special steel reinforcements are placed around such opening .In steel con struct ion , heavier and more rigid conn ecti ons are required to resist rack ing at the openings .In many high-rise build ings , a comb in ati on of walls and shafts can offer excelle ntresista nee to lateral forces whe n they are suitably located ant conn ected to one ano ther . It is also desirable that the stiff ness offered these subsystems be more-or-less symmertrical in all direct ions .Rigid-Frame SystemsIn the desig n of architectural build ings , rigid-frame systems for resist ing vertical and lateral loads have long bee n acce pted as an imp orta nt and sta ndard means for designingbuilding . They are empioyed for low-and medium means for designing build ings . They are empio yed for low- and medium up to high-rise build ing p erha ps 70 or 100 stories high . Whe n comp ared to shear-wall systems , these rigid frames both with in and at the outside of a buildi ngs . They also make use of the stiff ness in beams and colu mns that are required for the build ings in any case , but the colu mns are made stron ger whe n rigidly conn ected to resist the lateral as well as vertical forces though frame bending .Freque ntly , rigid frames will not be as stiff as shear-wall con struct ion , and therefore may p roduce excessive deflecti ons for the more sle nder high-rise buildi ngs desig ns . But because of this flexibility , they are ofte n con sidered as being more ductile and thus less susceptible to catastr op hic earthquake failure whe n comp ared with ( some ) shear-wall desig ns . For exa mple , if over stress ing occurs at certa in p orti ons of a steel rigid frame ( i.e., near the joi nt ) , ductility will allow the structure as a whole to deflect a little more , but it will by no means colla pse eve n un der a much larger force tha n exp ected on the structure . For this reas on , rigid-frame con struct ion is considered by some to be a “ best ” seisresisting type for high-rise steel buildings . On the other hand ,it is also unlikely that a well-designed share-wall system would colla pse.In the case of con crete rigid frames ,there is a diverge nee of opinion .It true that if a con crete rigid frame is desig ned in the conven ti onal manner , without sp ecial care to produce higher ductility , it will not be able to withstand a catastrophic earthquake that can p roduce forces several times lerger tha n the code desig n earthquake forces . therefore , some believe that it may not have additi onal cap acity p ossessed by steel rigid frames . But moder n research and exp erie nee has in dicated that con crete frames can be desig ned to be ductile , whe n sufficie nt stirr ups and joinery rein forceme nt are designed in to the frame . Modern buildings codes have specifications for the so-called ductile con crete frames . However , at p rese nt , these codesofte n require excessive rein forceme nt at certa in points in the frame so as to cause con gesti on and result in construction difficulties 。
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教师学科教案[ 20 – 20 学年度第__学期]任教学科：_____________任教年级：_____________任教老师：_____________xx市实验学校学号：xxxxxxxxxxHEBEI UNITED UNIVERSITY中英文翻译Abstract设计题目：唐山市第九中学教学楼设计学生姓名：XXX专业班级：X土木X班学院：建筑工程学院指导教师：XXXXXX2014年5月28日钢筋混凝土在每一个国家，混凝土及钢筋混凝土都被用来作为建筑材料。
很多地区，包括美国和加拿大，钢筋混凝土在工程建设中是主要的结构材料。
钢筋混凝土建筑的普遍性源于钢筋的广泛供应和混凝土的组成成分，砾石，沙子，水泥等，混凝土施工所需的技能相对简单，与其他形式的建设相比，钢筋混凝土更加经济。
混凝土及钢筋混凝土用于桥梁、各种地下结构建筑、水池、电视塔、海洋石油勘探建筑、工业建筑、大坝，甚至用于造船业。
钢筋混凝土结构可能是现浇混凝土结构，在其最后位置建造，或者他们可能是在一家工厂生产混凝土预制件，再在施工现场安装。
混凝土结构在设计上可能是普通的和多功能的，或形状和布局是奇想和艺术的。
其他很少几种建材能够提供建筑和结构如此的通用性和广泛适用性。
混凝土有较强的抗压力但抗拉力很弱。
因此，混凝土，每当承受荷载时，或约束收缩或温度变化，引起拉应力，在超过抗拉强度时，裂缝开始发展。
在素混凝土梁中，中和轴的弯矩是由在混凝土内部拉压力偶来抵抗作用荷载之后的值。
这种梁当出现第一道裂缝时就突然完全地断裂了。
在钢筋混凝土梁中，钢筋是那样埋置于混凝土中，以至于当混凝土开裂后弯矩平衡所需的拉力由纲筋中产生。
钢筋混凝土构件的建造包括以被建构件的形状支摸板。
模型必须足够强大，以至于能够支承自重和湿混凝土的静水压力，工人施加的任何力量都适用于它，具体的手推车，风压力，等等。
在混凝土的运作过程中，钢筋将被放置在摸板中。
在混凝土硬化后，模板都将被移走。
当模板被移走时，支撑将被安装来承受混凝土的重量直到它达到足够的强度来承受自重。
设计师必须使混凝土构件有足够的强度来抵抗荷、载和足够的刚度来防止过度的挠度变形。
除此之外，梁必须设计合理以便它能够被建造。
例如，钢筋必须按构造设计，以便能在现场装配。
由于当钢筋放入摸板后才浇筑混凝土，因此混凝土必须能够流过钢筋及摸板并完全充满摸板的每个角落。
被建成的结构材料的选择是混凝土，还是钢材、砌体，或木材，取决于是否有材料和一些价值决策。
结构体系的选择是由建筑师或工程师早在设计的基础上决定的，考虑到下列因素：1.经济。
常常首要考虑的是结构的总造价。
当然，这是随着材料的成本和安装构件的必需劳动力改变的。
然而，总投资常常更受总工期的影响，因为承包商和业主必须借款或贷款以便完成建设，在建筑物竣工前他们从此项投资中将得不到任何回报。
在一个典型的大型公寓或商业项目中，建筑成本的融资将是总费用的一个重要部分。
因此，金融储蓄，由于快速施工可能多于抵消增加材料成本。
基于这个原因，设计师可以采取任何措施规范设计来减轻削减的成本。
在许多情况下，长期的经济结构可能比第一成本更重要。
因此，维修和耐久性是重要的考虑因素。
2 .用于建筑与结构功能适宜的材料。
钢筋混凝土体系经常让设计师将建筑与结构的功能相结合。
混凝土被放置在塑性条件下借助于模板和表面加工来造出想要的形状和结构，这是它具有的优势。
在提供成品楼或天花板表面时，这使得平板或其他形式的板作为受力构件。
同样，钢筋混凝土墙壁能提供有吸引力的建筑表面，还有能力抵御重力、风力，或地震荷载。
最后，大小和形状的选择是由设计师而不是由提供构件的标准决定的。
3 .耐火性。
建筑结构必须经受得住火灾的袭击，并且当人员疏散及大火扑灭之时建筑物仍然保持不倒。
钢筋混凝土建筑特殊的防火材料及其他构造措施情况下，自身具有1-3个小时的耐火极限。
钢结构或木结构必须采取防火措施才能达到类似的耐火极限。
4 .低维护。
混凝土构件本身比结构钢或木材构件需要更少的维修。
如果致密，尤其如此，加气混凝土已经被用于暴露于大气中的表面，如果在设计中已经采取谨慎措施，以提供足够的排水和远离的结构。
必须采取的特别预防措施是让混凝土接触到盐，如除冰化学品。
5 .材料的供应。
砂、碎石、水泥和混凝土搅拌设备是被非常广泛使用的，以及钢筋比结构钢更容易运到多数工地。
因此，钢筋混凝土在偏远地区经常使用。
另一方面，有一些因素可能会导致选择钢筋混凝土以外的材料。
这些因素包括：1.低抗拉强度。
混凝土的抗拉强度是远低于其抗压强度（约1 / 10)，因此，混凝土易经受裂缝。
在结构用途时，用钢筋承受拉力，并限制裂缝宽度在允许的范围内来克服。
不过，在设计和施工中如果不采取措施，这些裂缝可能会有碍观瞻，或可允许水的浸入。
发生这种情况时，水或化学物质如道路除冰盐可能会导致混凝土的恶化或污染。
这种情况下，需要特别设计的措施。
在水支挡结构这种情况下，需要特别的措施和/或预应力，以防止泄漏。
2 .支摸。
建造一个现浇结构包括三个步骤，在钢或木结构的施工中是遇不到的。
这些都是支摸、拆摸、安装支撑，直至其达到足够的强度以支承其重量。
上述每个步骤，涉及劳动力和材料，在其他结构形式中，这是没有必要的。
3 . 每单位重量或量的相对低强度。
该混凝土抗压强度大约是钢材抗压强度5至10 ％，，而其单位密度大约是钢材密度的30 ％。
因此，一个混凝土结构，与钢结构相比，需要较大的体积和较大重量的材料。
因此，大跨度结构，往往建成钢结构。
4 .时间依赖的量的变化。
混凝土与钢进行大约同样数量的热膨胀和收缩时，有比较少量的钢材加热或冷却，因为钢与混凝土相比是一个较好的导体，钢结构比混凝土结构在更大程度上更易受温度变化。
另一方面，混凝土经历了干缩，如果被抑制，可能会导致变形或开裂。
此外，变形随着时间的推移将趋于增加，由于混凝土在持续的负荷下的徐变，可能会增加一倍。
几乎在土木工程和建筑的每一个分支中，钢筋混凝土在结构和基础领域内都得到了广泛的使用。
因此，工程师及建筑师在其整个职业生涯中需要钢筋混凝土设计的基本知识。
文章的大部分是直接关于组成典型的钢筋混凝土结构的部件如梁、柱和板他们之间的作用、协调。
一旦这些个别要素的作用被理解，设计师将有能力分析和设计这些元素组成的各种各样的复杂结构，例如地基，建筑物和桥梁。
由于钢筋混凝土是一个徐变、收缩，并出现裂缝的非匀质材料，它的应力不能由适用于材料强度均匀弹性材料的传统方程推导出的方程准确预测。
因此，许多钢筋混凝土的设计基于实证，即设计方程和设计方法是基于实验和费时的证明，而不是从理论的提法被完全导出的结果。
Reinforced ConcreteConcrete and reinforced concrete are used as building materials in every country. In many, including the United States and Canada, reinforced concrete is a dominant structural material in engineered construction. 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, and the economy of reinforced concrete compared to other forms of construction. Concrete and reinforced concrete are used in bridges, buildings of all sorts underground structures, water tanks, television towers, offshore oil exploration and production structures, dams, and even in ships.Reinforced concrete structures may be cast-in-place concrete, constructed in their final location, or they may be precast concrete produced in a factory and erected at the construction site. Concrete structures may be severe and functional in design, or the shape and layout and be whimsical and artistic. Few other building materials off the architect and engineer such versatility and scope.Concrete is strong in compression but weak in tension. As a result, cracks develop whenever loads, or restrained shrinkage of temperature changes, give rise to tensile stresses in excess of the tensile strength of the concrete. In a plain concrete beam, the moments about the neutral axis due to applied loads are resisted by an internal tension-compression couple involving tension in the concrete. Such a beam fails very suddenly and completely when the first crack forms. In a reinforced concrete beam, steel bars are embedded in the concrete in such a way that the tension forces needed for moment equilibrium after the concrete cracks can be developed in the bars.The construction of a reinforced concrete member involves building a from of mold in the shape of the member being built. The form must be strong enough to support both the weight and hydrostatic pressure of the wet concrete, and any forces applied to it by workers, concrete buggies, wind, and so on. The reinforcement is placed in this form and held in place during the concreting operation. After the concrete has hardened, the forms are removed. As the forms are removed, props of shores are installed to support the weight of the concrete until it has reached sufficient strength to support the loads by itself.The designer must proportion a concrete member for adequate strength to resist the loads and adequate stiffness to prevent excessive deflections. In beam must be proportioned so that it can be constructed. For example, the reinforcement must be detailed so that it can be assembled in the field, and since the concrete is placed in the form after the reinforcement is in place, the concrete must be able to flow around, between, and past the reinforcement to fill all parts of the form completely.The choice of whether a structure should be built of concrete, steel, masonry, or timber depends on the availability of materials and on a number of value decisions. The choice of structural system is made by the architect of engineer early in the design, based on the following considerations:1. Economy.Frequently, the foremost consideration is the overall const of the structure. This is, of course, a function of the costs of the materials and the labor necessary to erect them. Frequently, however, the overall cost is affected as much or more by the overall construction time since the contractor and owner must borrow or otherwise allocate money to carry out the construction and will not receive a return on this investment until the building is ready for occupancy. In a typical large apartment of commercial project, the cost of construction financing will be a significant fraction of the total cost. As a result, financial savings due to rapid construction may more than offset increased material costs. For this reason, any measures the designer can take to standardize the design and forming will generally pay off in reduced overall costs.In many cases the long-term economy of the structure may be more important than the first cost. As a result, maintenance and durability are important consideration.2. Suitability of material for architectural and structural function.A reinforced concrete system frequently allows the designer to combine the architectural and structural functions. Concrete has the advantage that it is placed in a plastic condition and is given the desired shape and texture by means of the forms and the finishing techniques. This allows such elements ad flat plates or other types of slabs to serve as load-bearing elements while providing the finished floor and ceiling surfaces. Similarly, reinforced concrete walls can provide architecturally attractive surfaces in addition to having the ability to resist gravity, wind, or seismic loads. Finally, the choice of size of shape is governed by the designer and not by the availability of standard manufactured members.3. Fire resistance. The structure in a building must withstand the effects of a fire and remain standing while the building is evacuated and the fire is extinguished. A concrete building inherently has a 1- to 3-hour fire rating without special fireproofing or other details. Structural steel or timber buildings must be fireproofed to attain similar fire ratings.4. Low maintenance. Concrete members inherently require less maintenance than do structural steel or timber members. This is particularly true if dense, air-entrained concrete has been used for surfaces exposed to the atmosphere, and if care has been taken in the design to provide adequate drainage off and away from the structure. Special precautions must be taken for concrete exposed to salts such as deicing chemicals.5. Availability of materials. Sand, gravel, cement, and concrete mixing facilitiesare very widely available, and reinforcing steel can be transported to most job sites more easily than can structural steel. As a result, reinforced concrete is frequently used in remote areas.On the other hand, there are a number of factors that may cause one to select a material other than reinforced concrete. These include:1. Low tensile strength. The tensile strength concrete is much lower than its compressive strength ( about 1/10 ), and hence concrete is subject to cracking. In structural uses this is overcome by using reinforcement to carry tensile forces and limit crack widths to within acceptable values. Unless care is taken in design and construction, however, these cracks may be unsightly or may allow penetration of water. When this occurs, water or chemicals such as road deicing salts may cause deterioration or staining of the concrete. Special design details are required in such cases. In the case of water-retaining structures, special details and / of prestressing are required to prevent leakage.2. Forms and shoring. The construction of a cast-in-place structure involves three steps not encountered in the construction of steel or timber structures. These are the construction of the forms、the removal of these forms、and propping or shoring the new concrete to support its weight until its strength is adequate. Each of these steps involves labor and materials, which are not necessary with other forms of construction.3. Relatively low strength per unit of weight for volume. The compressive strength of concrete is roughly 5 to 10% that of steel, while its unit density is roughly 30% that of steel. As a result, a concrete structure requires a larger volume and a greater weight of material than does a comparable steel structure. As a result, long-span structures are often built from steel.4.Time-dependent volume changes.Both concrete and steel undergo-approximately the same amount of thermal expansion and contraction. Because there is less mass of steel to be heated or cooled, and because steel is a better concrete, a steel structure is generally affected by temperature changes to a greater extent than is a concrete structure. On the other hand, concrete undergoes frying shrinkage, which, if restrained, may cause deflections or cracking. Furthermore, deflections will tend to increase with time, possibly doubling, due to creep of the concrete under sustained loads.In almost every branch of civil engineering and architecture extensive use is made of reinforced concrete for structures and foundations. Engineers and architects requires basic knowledge of reinforced concrete design throughout their professional careers. Much of this text is directly concerned with the behavior and proportioning of components that make up typical reinforced concrete structures-beams, columns, and slabs. Once the behavior of these individual elements is understood, the designer willhave the background to analyze and design a wide range of complex structures, such as foundations, buildings, and bridges, composed of these elements.Since reinforced concrete is a no homogeneous material that creeps, shrinks, and cracks, its stresses cannot be accurately predicted by the traditional equations derived in a course in strength of materials for homogeneous elastic materials. Much of reinforced concrete design in therefore empirical, i.e., design equations and design methods are based on experimental and time-proved results instead of being derived exclusively from theoretical formulations.。