土木工程毕业设计外文翻译
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。
土木工程专业毕业设计- 外文翻译
Structure in Design of ArchitectureAnd Structural Material专业：土木工程学生：指导老师：We have and the architects must deal with the spatial aspect of activity, physical, and symbolic needs in such a way that overall performance integrity is assured. Hence, he or she well wants to think of evolving a building environment as a total system of interacting and space forming subsystems. Is represents a complex challenge, and to meet it the architect will need a hierarchic design process that provides at least three levels of feedback thinking: schematic, preliminary, and final.Such a hierarchy is necessary if he or she is to avoid being confused , at conceptual stages of design thinking ,by the myriad detail issues that can distract attention from more basic considerations .In fact , we can say that an architect’s ability to distinguish the more basic form the more detailed issues is essential to his success as a designer .The object of the schematic feed back level is to generate and evaluate overall site-plan, activity-interaction, and building-configuration options .To do so the architect must be able to focus on the interaction of the basic attributes of the site context, the spatial organization, and the symbolism as determinants of physical form. This means that ,in schematic terms ,the architect may first conceive and model a building design as an organizational abstraction of essential performance-space in teractions.Then he or she may explore the overall space-form implications of the abstraction. As an actual building configuration option begins to emerge, it will be modified to include consideration for basic site conditions.At the schematic stage, it would also be helpful if the designer could visualize his or her options for achieving overall structural integrity and consider the constructive feasibility and economic of his or her scheme .But this will require that the architect and/or a consultant be able to conceptualize total-system structural options in terms of elemental detail .Such overall thinking can be easily fed back to improve the space-form scheme.At the preliminary level, the architect’s emphasis will shift to the elaboration of his or her more promising schematic design options .Here the architect’s structural needs will shift to approximate design of specific subsystem options. At this stage the total structural scheme is developed to a middle level of specificity by focusing on identification and design of major subsystems to the extent that their key geometric, component, and interactive properties are established .Basic subsystem interaction and design conflicts can thus be identified and resolved in the context of total-system objectives. Consultants can play a significant part in this effort; these preliminary-level decisions may also result in feedback that calls for refinement or even major change in schematic concepts.When the designer and the client are satisfied with the feasibility of a design proposal at the preliminary level, it means that the basic problems of overall design are solved and details arenot likely to produce major change .The focus shifts again ,and the design process moves into the final level .At this stage the emphasis will be on the detailed development of all subsystem specifics . Here the role of specialists from various fields, including structural engineering, is much larger, since all detail of the preliminary design must be worked out. Decisions made at this level may produce feedback into Level II that will result in changes. However, if Levels I and II are handled with insight, the relationship between the overall decisions, made at the schematic and preliminary levels, and the specifics of the final level should be such that gross redesign is not in question, Rather, the entire process should be one of moving in an evolutionary fashion from creation and refinement (or modification) of the more general properties of a total-system design concept, to the fleshing out of requisite elements and details.To summarize: At Level I, the architect must first establish, in conceptual terms, the overall space-form feasibility of basic schematic options. At this stage, collaboration with specialists can be helpful, but only if in the form of overall thinking. At Level II, the architect must be able to identify the major subsystem requirements implied by the scheme and substantial their interactive feasibility by approximating key component properties .That is, the properties of major subsystems need be worked out only in sufficient depth to very the inherent compatibility of their basic form-related and behavioral interaction . This will mean a somewhat more specific form of collaboration with specialists then that in level I .At level III ,the architect and the specific form of collaboration with specialists then that providing for all of the elemental design specifics required to produce biddable construction documents .Of course this success comes from the development of the Structural Material.The principal construction materials of earlier times were wood and masonry brick, stone, or tile, and similar materials. The courses or layers were bound together with mortar or bitumen, a tar like substance, or some other binding agent. The Greeks and Romans sometimes used iron rods or claps to strengthen their building. The columns of the Parthenon in Athens, for example, have holes drilled in them for iron bars that have now rusted away. The Romans also used a natural cement called puzzling, made from volcanic ash, that became as hard as stone under water.Both steel and cement, the two most important construction materials of modern times, were introduced in the nineteenth century. Steel, basically an alloy of iron and a small amount of carbon had been made up to that time by a laborious process that restricted it to such special uses as sword blades. After the invention of the Bessemer process in 1856, steel was available in large quantities at low prices. The enormous advantage of steel is its tensile force which, as we have seen, tends to pull apart many materials. New alloys have further, which is a tendency for it to weaken as a result of continual changes in stress.Modern cement, called Portland cement, was invented in 1824. It is a mixture of limestone and clay, which is heated and then ground into a power. It is mixed at or near the construction site with sand, aggregate small stones, crushed rock, or gravel, and water to make concrete. Different proportions of the ingredients produce concrete with different strength and weight. Concrete is very versatile; it can be poured, pumped, or even sprayed into all kinds of shapes. And whereas steel has great tensile strength, concrete has great strength under compression. Thus, the two substances complement each other.They also complement each other in another way: they have almost the same rate ofcontraction and expansion. They therefore can work together in situations where both compression and tension are factors. Steel rods are embedded in concrete to make reinforced concrete in concrete beams or structures where tensions will develop. Concrete and steel also form such a strong bond─ the force that unites them─ that the steel cannot slip within the concrete. Still another advantage is that steel does not rust in concrete. Acid corrodes steel, whereas concrete has an alkaline chemical reaction, the opposite of acid.The adoption of structural steel and reinforced concrete caused major changes in traditional construction practices. It was no longer necessary to use thick walls of stone or brick for multistory buildings, and it became much simpler to build fire-resistant floors. Both these changes served to reduce the cost of construction. It also became possible to erect buildings with greater heights and longer spans.Since the weight of modern structures is carried by the steel or concrete frame, the walls do not support the building. They have become curtain walls, which keep out the weather and let in light. In the earlier steel or concrete frame building, the curtain walls were generally made of masonry; they had the solid look of bearing walls. Today, however, curtain walls are often made of lightweight materials such as glass, aluminum, or plastic, in various combinations.Another advance in steel construction is the method of fastening together the beams. For many years the standard method was riveting. A rivet is a bolt with a head that looks like a blunt screw without threads. It is heated, placed in holes through the pieces of steel, and a second head is formed at the other end by hammering it to hold it in place. Riveting has now largely been replaced by welding, the joining together of pieces of steel by melting a steel material between them under high heat.Priestess’s concrete is an improved form of reinforcement. Steel r ods are bent into the shapes to give them the necessary degree of tensile strengths. They are then used to priestess concrete, usually by one of two different methods. The first is to leave channels in a concrete beam that correspond to the shapes of the steel rods. When the rods are run through the channels, they are then bonded to the concrete by filling the channels with grout, a thin mortar or binding agent. In the other (and more common) method, the priestesses steel rods are placed in the lower part of a form that corresponds to the shape of the finished structure, and the concrete is poured around them. Priestess’s concrete uses less steel and less concrete. Because it is a highly desirable material.Progressed concrete has made it possible to develop buildings with unusual shapes, like some of the modern, sports arenas, with large spaces unbroken by any obstructing supports. The uses for this relatively new structural method are constantly being developed.建筑中的结构设计及建筑材料专业：土木工程学生：指导老师：建筑师必须从一种全局的角度出发去处理建筑设计中应该考虑到的实用活动，物质及象征性的需求。
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。
土木工程毕业外文翻译
1.Central iron & Steel Research institute, Beijing 100081, China2.Chinese Society for Metals, Beijing 100711, China高层建筑与钢结构HUi Wei-jun,DONG HanWENG Yu-ging,CHEN Si-lian,WANG Mao-giu摘要耐火钢其实就是对火灾有一定抵抗能力的钢材，日本认为耐火钢是焊接结构用轧制钢材的一类，在我国它是建筑用低合金钢的一种。
耐火钢于普通的建筑用钢不同，它要求具有良好的耐高温性能，作为常温下的承载材料，只要求在遇到火灾的较短时间内（1到3小时）高温条件下能够保持高的屈服强度，常温下钢材强度的2/3相当于该材料的长期允许应力值，当发生火灾时，如果耐火钢的屈服点仍然在此值以上，建筑物就不会倒塌。
因此，就要求耐火钢在一定高温下的屈服不低于室温下屈服强度的2/3。
本文研究的目的在于研究提高耐火港的强韧性、抗震性和耐火性能。
关键字高层建筑；钢结构；发展应用1.前言近年来，虽然一般的建筑结构设计取得了很大的进步，但是取得显著成绩的还要数超高层建筑结构设计。
最初的高层建筑设计是从钢结构的设计开始的。
钢筋混凝土和受力外包钢筒系统运用起来是比较经济的系统，被有效地运用于大批的民用建筑和商业建筑中。
50层到100层的建筑被成为超高层建筑。
而这种建筑在美国被广泛的应用是由于新的结构系统的发展和创新。
这样的高度需要大柱和梁的尺寸，这样以来可以使建筑物更加坚固以至于在允许的限度范围内承受风荷载而不产生弯曲和倾斜。
过分的倾斜会导致建筑物的隔离构件、顶棚以及其它建筑细部产生循环破坏。
除此之外，过大的摇动也会使建筑物的使用者感觉到这样的晃动而产生不舒服的感觉。
无论是钢筋混凝土结构系统还是钢结构系统都充分利用了整个建筑的刚度潜力，因此，不能指望利用多余的刚度来限制侧向位移。
土木工程毕业设计--外文翻译
1 Introduction and scope1.1 Aims of the ManualThis Manual provides guidance on the design of reinforced and prestressed concrete building structures. Structures designed in accordance with this Manual will normally comply with DD ENV 1992-1-1: 19921 (hereinafter referred to as EC2).1.2 Eurocode systemThe structural Eurocodes were initiated by the European Commission but are now produced by the Comité Européen de Normalisation (CEN) which is the European standards organization, its members being the national standards bodies of the EU and EFTA countries,e.g. BSI.CEN will eventually publish these design standards as full European Standards EN (Euronorms), but initially they are being issued as Prestandards ENV. Normally an ENV has a life of about 3 years to permit familiarization and trial use of the standard by member states. After formal voting by the member bodies, ENVs are converted into ENs taking into account the national comments on the ENV document. At present the following Eurocode parts have been published as ENVs but as yet none has been converted to an EN:DD ENV 1991-1-1: Basis of design and actions on structures (EC1)DD ENV 1992-1-1: Design of concrete structures (EC2)DD ENV 1993-1-1: Design of steel structures (EC3)DD ENV 1994-1-1: Design of composite steel and concrete structures (EC4)DD ENV 1995-1-1: Design of timber structures (EC5)DD ENV 1996-1-1: Design of masonry structures (EC6)DD ENV 1997-1-1: Geotechnical design (EC7)DD ENV 1998-1-1: Earthquake resistant design of structures (EC8)DD ENV 1999-1-1: Design of aluminium alloy structures (EC9)Each Eurocode is published in a number of parts, usually with ‘General rules’ and ‘Rules for buildings’ in Part 1. The various parts of EC2 are:Part 1.1 General rules and rules for buildings;Part 1.2 Supplementary rules for structural fire design;Part 1.3 Supplementary rules for precast concrete elements and structures;Part 1.4 Supplementary rules for the use of lightweight aggregate concrete;Part 1.5 Supplementary rules for the use of unbonded and external prestressing tendons;Part 1.6 Supplementary rules for plain or lightly reinforced concrete structures;Part 2.0 Reinforced and prestressed concrete bridges;Part 3.0 Concrete foundations;Part 4.0 Liquid retaining and containment structures.All Eurocodes follow a common editorial style. The codes contain ‘Principles’ and‘Application rules’. Principles are general statements, definitions, requirements and sometimes analytical models. All designs must comply with the Principles, and no alternative is permitted. Application rules are rules commonly adopted in design. They follow the Principles and satisfy their requirements. Alternative rules may be used provided that compliance with the Principles can be demonstrated.Some parameters in Eurocodes are designated by | _ | , commonly referred to as boxed values. The boxed values in the Codes are indicative guidance values. Each member state is required to fix the boxed value applicable within its jurisdiction. Such information would be found in the National Application Document (NAD) which is published as part of each ENV.There are also other purposes for NADs. NAD is meant to provide operational information to enable the ENV to be used. For certain aspects of the design, the ENV may refer to national standards or to CEN standard in preparation or ISO standards. The NAD is meant to provide appropriate guidance including modifications required to maintain compatibility between the documents. Very occasionally the NAD might rewrite particular clauses of the code in the interest of safety or economy. This is however rare.1.3 Scope of the ManualThe range of structures and structural elements covered by the Manual is limited to building structures that do not rely on bending in columns for their resistance to horizontal forces and are also non-sway. This will be found to cover the vast majority of all reinforced and prestressed concrete building structures. In using the Manual the following should be noted:• The Manual has been drafted to comply with ENV 1992-1-1 together with the UK NAD• Although British Standards have been referenced as loading codes in Sections 3 and 6,to comply with the UK NAD, the Manual can be used in conjunction with other loading codes • The structures are braced and non-sway• The concrete is of normal weight• The structure is predominantly in situ• Prestressed concrete members have bonded or unbonded internal tendons• The Manual can be used in conjunction with all commonly used materials in construction; however the data given are limited to the following:– concrete up to characteristic cylinder strength of 50N/mm2 (cube strength 602N/mm)– high-tensile reinforcement with characteristic strength of 4602N/mm– mild-steel reinforcement with characteristic strength of 2502N/mm– prestressing tendons with 7-wire low-relaxation (Class 2) strands• High ductility (Class H) has been assumed for:– all ribbed bars and grade 250 bars, and– ribbed wire welded fabric in wire sizes of 6mm or over• Normal ductility (Class N) has been assumed for plain or indented wire welded fabric.For structures or elements outside this scope EC2 should be used.1.4 Contents of the ManualThe Manual covers the following design stages:• gene ral principles that govern the design of the layout of the structure• initial sizing of members• estimating of quantities of reinforcement and prestressing tendons• final design of members.2 General principlesThis section outlines the general principles that apply to both initial and final design of both reinforced and prestressed concrete building structures, and states the design parameters that govern all design stages.2.1 GeneralOne engineer should be responsible for the overall design, including stability, and should ensure the compatibility of the design and details of parts and components even where some or all of the design and details of those parts and components are not made by the same engineer.The structure should be so arranged that it can transmit dead, wind and imposed loads in a direct manner to the foundations. The general arrangement should ensure a robust and stable structure that will not collapse progressively under the effects of misuse or accidental damage to any one element.The engineer should consider engineer site constraints, buildability2, maintainability and decommissioning.The engineer should take account of his responsibilities as a ‘Designer’ under the Construction (Design & Management) Regulations.32.2 StabilityLateral stability in two orthogonal directions should be provided by a system of strongpoints within the structure so as to produce a braced non-sway structure, in which the columns will not be subject to significant sway moments. Strongpoints can generally be provided by the core walls enclosing the stairs, lifts and service ducts. Additional stiffness can be provided by shear walls formed from a gable end or from some other external or internal subdividing wall. The core and shear walls should preferably be distributed throughout the structure and so arranged that their combined shear centre is located approximately on the line of the resultant in plan of the applied overturning forces. Where this is not possible, the resulting twisting moments must be considered when calculating the load carried by each strongpoint. These walls should generally be of reinforced concrete not less than 180mm thick to facilitate concreting, but they may be of 215mm brickwork or 190mm solid blockwork properly tied and pinned up to the framing for low- to medium-rise buildings.Strongpoints should be effective throughout the full height of the building. If it is essential for strongpoints to be discontinuous at one level, provision must be made to transfer the forces toother vertical components.It is essential that floors be designed to act as horizontal diaphragms, particularly if precast units are used.Where a structure is divided by expansion joints each part should be structurally independent and designed to be stable and robust without relying on the stability of adjacent sections.2.3 RobustnessAll members of the structure should be effectively tied together in the longitudinal, transverse and vertical directions.A well-designed and well-detailed cast-in situ structure will normally satisfy the detailed tying requirements set out in subsection 5.11.Elements whose failure would cause collapse of more than a limited part of the structure adjacent to them should be avoided. Where this is not possible, alternative load paths should be identified or the element in question strengthened.2.4 Movement jointsMovement joints may need to be provided to minimize the effects of movements caused by, for example, shrinkage, temperature variations, creep and settlement.The effectiveness of movement joints depends on their location. Movement joints should divide the structure into a number of individual sections, and should pass through the whole structure above ground level in one plane. The structure should be framed on both sides of the joint. Some examples of positioning movement joints in plan are given in Fig. 2.1.Movement joints may also be required where there is a significant change in the type of foundation or the height of the structure. For reinforced concrete frame structures in UK conditions, movement joints at least 25mm wide should normally be provided at approximately 50m centres both longitudinally and transversely. In the top storey and for open buildings and exposed slabs additional joints should normally be provided to give approximately 25m spacing. Joint spacing in exposed parapets should be approximately 12m.Joints should be incorporated in the finishes and in the cladding at the movement joint locations.2.5 Fire resistance and durabilityFor the required period of fire resistance (prescribed in the Building Regulations), the structure should:• have adequate loadbearing capacity• limit the temperature rise on the far face by sufficient insulation, and• have sufficient integrity to prevent the formation of crack s that will allow the passage of fire and gases.Fig. 2.1 Location of movement jointsThe design should take into account the likely deterioration of the structure and its components in their environment having due regard to the anticipated level of maintenance. The following inter-related factors should be considered:• the required performance criteria• the expected environmental conditions• the composition, properties and performance of materials• the shape of members and detailing• the quality of workmanship• any protective measure• the likely maintenance during the intended life.Concrete of appropriate quality with adequate cover to the reinforcement should be specified. The above requirements for durability and fire resistance may dictate sizes for members greater than those required for structural strength alone.3 Design principles – reinforced concrete3.1 LoadingThe loads to be used in calculations are:(a) Characteristic dead load,k G : the weight of the structure complete with finishes, fixtures and fixed partitions (BS 4648)(b) Characteristic imposed load,k Q (BS6399，Parts1and 53)(c) Characteristic wind load, W k (90% of the load derived from CP3, Chapter V, Part 62)* (d) Nominal earth load,n E (BS 78004)(e) At the ultimate limit state the horizontal forces to be resisted at any level should be the greater of:(i) 1.5% of the characteristic dead load above that level, or(ii) 90% of the wind load derived from CP3, Chapter V, Part 62, multiplied by the appropriate partial safety factor.The horizontal forces should be distributed between the strongpoints according to their stiffness.In using the above documents the following modifications should be noted:(f) The imposed floor loads of a building should be treated as one load to which the reduction factors given in BS 6399: Part 1:51996are applicable.(g) Snow drift loads obtained from BS 6399: Part 3:51998 should be multiplied by 0.7 and treated in a similar way to an imposed load and not as an accidental load.3.2 Limit statesThis Manual adopts the limit-state principle and the partial factor format of EC2.3.2.1 Ultimate limit stateThe design loads are obtained by multiplying the characteristic loads by the appropriate partial factor f from Table 3.1.The ‘adverse’ and ‘beneficial’ factors should be used so as to produce the most onerous condition.3.2.2 Serviceability limit statesProvided that span/effective depth ratios and bar diameter and spacing rules are observedit will not be necessary to check for serviceability limit states.fThe Table uses the simplified combination permitted in EC2.†For pressures arising from an accidental head of water at ground level a partial factor of 1.15 may be used.3.3 Material and design stressesDesign stresses are given in the appropriate sections of the Manual. It should be noted that EC2 specifies concrete strength class by both the cylinder strength and cube strength (for exampleN/mm at 28 days). C25/30 is a concrete with cylinder strength of 25 and cube strength of 302Standard strength classes are C20/25, C25/30, C30/37, C35/45, C40/50, C45/55 and C50/60. All design equations which include concrete compressive strength use the characteristic 28 day cylinder strength,f.ckPartial factors for concrete are 1.5 for ultimate limit state and 1.0 for serviceability limit state. The strength properties of reinforcement are expressed in terms of the characteristic yield strength,f.ykPartial factors for reinforcement steel are 1.15 for ultimate limit state and 1.0 for serviceability limit state.4 Initial design – reinforced concrete4.1 IntroductionIn the initial stages of the design of building structures it is necessary, often at short notice,to produce alternative schemes that can be assessed for architectural and functional suitability and which can be compared for cost. They will usually be based on vague and limited information on matters affecting the structure such as imposed loads and nature of finishes, let alone firm dimensions, but it is nevertheless expected that viable schemes be produced on which reliable cost estimates can be based.It follows that initial design methods should be simple, quick, conservative and reliable. Lengthy analytical methods should be avoided.This section offers some advice on the general principles to be applied when preparing a scheme for a structure, followed by methods for sizing members of superstructures. Foundation design is best deferred to later stages when site investigation results can be evaluated.The aim should be to establish a structural scheme that is suitable for its purpose, sensibly economical, and not unduly sensitive to the various changes that are likely to be imposed as the overall design develops.Sizing of structural members should be based on the longest spans (slabs and beams) and largest areas of roof and/or floors carried (beams, columns, walls and foundations). The same sizes should be assumed for similar but less onerous cases – this saves design and costing time at this stage and is of actual benefit in producing visual and constructional repetition and hence, ultimately, cost benefits.Simple structural schemes are quick to design and easy to build. They may be complicated later by other members of the design team trying to achieve their optimum conditions, but a simple scheme provides a good ‘benchmark’ at the initial stage.Loads should be carried to the foundation by the shortest and most direct routes. In constructional terms, simplicity implies (among other matters) repetition; avoidance of congested, awkward or structurally sensitive details and straightforward temporary works with minimal requirements for unorthodox sequencing to achieve the intended behaviour of the completed structure.Standardized construction items will usually be cheaper and more readily available than purpose-made items.4.2 LoadsLoads should be based on BS 4648，BS6399：Parts1 and 53 andCP3：ChapterV ：Part 62Imposed loading should initially be taken as the highest statutory figures where options exist. The imposed load reduction allowed in the loading code should not be taken advantage of in the initial design stage except when assessing the load on the foundations.Loading should be generous and not less than the following in the initial stages:floor finish (screed) 1.82kN/mmceiling and service load 0.52kN/mmAllowance for:demountable lightweight partitions* 1.02kN/mmblockwork partitions† 2.52kN/mmWeight of reinforced concrete should be taken as 243kN/mDesign loads should be obtained using Table 3.1.4.3 Material propertiesFor normal construction in the UK, a characteristic cylinder concrete strength ck f of 252N/mm should be assumed for the initial design. In areas with poor aggregates this may have to be reduced.For UK steels a characteristic strength yk f of 4602N/mm should be used for high-tensile reinforcement and 2502N/mm for mild steel.4.4 Structural form and framingThe following measures should be adopted:(a) provide stability against lateral forces and ensure braced construction by arranging suitable shear walls deployed symmetrically wherever possible(b) adopt a simple arrangement of slabs, beams and columns so that loads are carried to the foundations by the shortest and most direct routes(c) allow for movement joints (see subsection 2.4)(d) choose an arrangement that will limit the span of slabs to 5m to 6m and beam spans to 8m to l0m on a regular grid; for flat slabs restrict column spacings to 8m(e) adopt a minimum column size of 300mm × 300mm or equivalent area(f) provide a robust structure.The arrangement should take account of possible large openings for services and problems with foundations, e.g. columns immediately adjacent to site boundaries may require balanced or other special foundations.4.5 Fire resistance and durabilityThe size of structural members may be governed by the requirement of fire resistance and may also be affected by the cover necessary to ensure durability. Table 4.1 shows the minimum practical member sizes for different periods of fire resistance and the cover to the main reinforcement required for continuous members in dry and humid environments without frost. For other exposure classes, cover should be increased. For simply supported members, sizes and cover should be increased (see Section 5 and Appendix C).4.6 StiffnessTo provide adequate stiffness, the effective depths of beams, slabs and the waist of stairs should not be less than those derived from Table 4.2.Beams should be of sufficient depth to avoid the necessity for excessive compression reinforcement and to ensure that economical amounts of tension and shear reinforcement are provided. This will also facilitate the placing of concrete.*To be treated as imposed loads.†To be treated as dead load s when the layout is fixed.Table 4.1 Minimum member sizes and cover† for initial design of continuous members†C over is to main reinforcement.Table 4.2 Basic ratios of span/effective depth for initial design (yk f = 4602N/mm )1. For two-way spanning slabs (supported on beams), the check on the ratio of span/effective depth should be carried out on the shorter span. For flat slabs, the longer span should be taken.2. For flanged sections with the ratio of the flange to the rib width greater than 3, the Table value should be multiplied by 0.8.3. For members, other than flat slab panels, which support partitions liable to be damaged by excessive deflection of the member, and where the span exceeds 7m, the Table value should be multiplied by 7/span.4. For flat slabs where the greater span exceeds 8.5m, the Table value should be multiplied by 8.5/span.第一章引言和适用范围1.1手册的作用这本手册为设计钢筋和预应力混凝土建筑结构提供了指导。
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 。
土木工程毕业设计外文翻译
Ecological Engineering 35(2009)1043–1050Contents lists available at ScienceDirectEcologicalEngineeringj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /e c o l e ngEnhancement of nitrogen removal in towery hybrid constructed wetland to treat domestic wastewater for small rural communitiesa r t i c l e i n f o Article history:Received 11September 2008Received in revised form 6January 2009Accepted 23March 2009Keywords:Constructed wetlands Nitrification DenitrificationDomestic wastewater Nitrogen removal Nitrifying bacteria Denitrifying bacteriaa b s t r a c tEfforts to protect watercourses,especially sources of drinking water,particularly in rural areas,are now underway in China.Nitrogen present in wastewater,due to its role in eutrophication and potential toxicity to aquatic species,is a focus of primary concern.Constructed wetlands (CWs),a simpler,less costly treat-ment alternative,have been used to treat domestic wastewater for small communities.Although showing great promise for removing carbonaceous materials from wastewater,wetland systems have not been suc-cessful in removing nitrogen mainly due to lack of dissolved oxygen (DO).To enhance nitrogen removal,a novel CW configuration with three stages,towery hybrid constructed wetland (THCW),was designed.The first and third stages were rectangle subsurface horizontal flow CWs,and the second stage was a cir-cular three-layer free-water flow CW.Increased DO by passive aeration of a tower type cascade overflow from the upper layer into the lower layer in the second stage of the wetland enhanced nitrification rates.Denitrification rates were also improved by additional organic matter supplied as a result of bypass influ-ent directly into the second stage.Evergreen tree Pond Cypress (Taxodium ascendens ),industrial plants Mat Rush (Schoenoplectus trigueter )and Wild Rice shoots (Zizania aquatica ),ornamental floriferous plants Pygmy Waterlily (Nymphaea tetragona )and Narrow-leaved Cattail (Typha angustifolia )were planted in the wetland.The average percentage of removal was 89%,85%,83%,83%and 64%for total suspended solid,chemical oxygen demand,ammonia nitrogen,total nitrogen and total phosphorus,respectively.There was no significant difference (p <0.05)at low and high hydraulic loads (16cm/d and 32cm/d)for perfor-mance of THCW.Nitrifying and denitrifying bacteria as well as potential nitrification activity and potential denitrification rates measured have shown that nitrification–denitrification is the main mechanism for nitrogen removal in the wetland.THCW also provided additional aesthetic benefits.©2009Elsevier B.V.All rights reserved.1.IntroductionWidespread demands for improved receiving water quality,especially drinking water are currently driving the implementa-tion of advanced wastewater treatment techniques.In rural areas of China,the domestic sewage was discharged directly into water-courses,lakes,rivers,soil or sea.This discharge of poorly treated sewage is responsible for many watercourses,reservoirs and lakes not meeting their quality objectives.Many small communities located in rural areas of China lack adequate domestic wastewa-ter treatment facilities.Wastewater collection and treatment are problematic in these areas due to mountainous terrain,dispersed population,and a lower economic base.In order for resource-scarce,economically developing rural areas to adopt wastewater treatment,the treatment technologies must be cost-effectiveand easy to adopt,require less energy input and maintenance costs,and be capable of meeting effluent discharge standards.The centralized wastewater treatment plants based on activated sludge or bacterial beds processes which are utilized in large and small cities are not economically adaptable for such rural areas,mainly due to the construction costs of sewage collec-tors.On the other hand,the nitrogen content of many watercourses,reservoirs and lakes in China does not meet the standards of national and local governments.It now seems clear that in many lakes,most estuaries,and almost all coastal waters,nitrogen also plays a major role in eutrophication.Therefore,national regula-tions have recently been issued;the project is called “new country construction”.The regulations stipulate that the domestic wastew-ater in rural areas must be treated before being discharged into a watercourse or soil.Constructed wetlands (CWs)have been scientifically tested and constructed for on-site treatment in rural areas for small units and small villages.Simple construction,large buffering capacity,little1044 F.Ye,Y.Li/Ecological Engineering35(2009)1043–1050excess sludge production,simple operation and maintenance,as well as low operational and maintenance costs are the advantages of CWs.The treatment efficiency is generally good in terms of sus-pended solid(SS),biochemical oxygen demand(BOD)and chemical oxygen demand(COD)removal;but nitrogen removal,particularly ammonia nitrogen(NH3-N),in most of the present generation of operating wetland systems(predominately horizontalflow beds)is deficient mainly due to the insufficient amount of oxygen available to the nitrifying microbial population in CWs.Generally nitrogen removal in subsurface horizontalflow(SSHF)systems is about 30–40%,and means of30%(NH3-N)and39.6%total nitrogen(TN) are given for268European constructed wetlands.However,sin-gle sets of data concerning removal efficiency differ extremely in most of the long-term evaluated SSHF systems(Vymazal,2005). This problem is caused by an unsatisfactory hydraulic conductivity and an oxygenation deficiency in the root zone.To achieve higher elimination rates,verticalflow systems have been developed.But, again,removal of nutrients often turned out to be insufficient in all these designs of constructed wetlands.Nitrification does occur in conventional wetland systems,but typically requires long hydraulic retention time(HRT).Biological nitrification–denitrification is usually the most sig-nificant nitrogen removal mechanism in CWs;other mechanisms such as plant uptake,substrate adsorption and ammonia volatiliza-tion are generally of less importance(Green,1997).Although plant uptake of nitrogen occurs,only a minor fraction can typically be removed by plants on a sustainable basis.The uptake capacity of emergent macrophytes,if harvested,is roughly200–2500kg N/ka per year,whereas the capacity of submerged macrophytes is lower(<700kg N/ka per year)(Brix,1994).Furthermore,if the wetlands are not harvested,the vast majority of the nutri-ents that have been incorporated into the plant tissue will be returned to the water by decomposition processes.The biologi-cal nitrification–denitrification process depends on various factors such as temperature,pH,alkalinity and,above all,electron and dissolved oxygen(DO)availability.The removal of NH3-N is largely dependent on the O2supply.The bed medium is con-tinuously water-saturated and therefore generally anaerobic.The plants transport O2to the rhizosphere,thereby creating aerobic microsites,adjacent to the roots and rhizomes where NH4+will be oxidizedfirst to nitrite by nitrifying bacteria such as Nitrosomonas and then to nitrate by bacteria with the same enzymatic equip-ment as Nitrobacter.After diffusion in an anaerobic zone of the wetland and in the presence of an electron source such as lac-tate or hydrogen gas,nitrates will serve as an electron sink for a very large family of bacteria called nitrate reducers.Nitrate is finally reduced to N2and emitted into the atmosphere(Drio et al., 1997).The rate of nitrification is significantly lower than that of denitrification and,in fact,becomes the limiting factor for con-trolling nitrogen removal.When1g of NH3-N is oxidized to be NO3-N,4.3g of oxygen is required.For NH3-N with a concentra-tion of1mg/L,nitrification will not occur successfully until the DO reaches4.6mg/L.The mineralization of the excess influent BOD likely depleted the available oxygen and retarded nitrifica-tion.However,the oxygen conducted by aquaculture is limited.Root oxygen release rates from a number of submerged aquatic plants is reported to be in the range of0.5–5.2g/(m2d)(Caffreya and Kempb,1991),and from free-floating plants0.25–9.6g/(m2d)(Brix, 1997).The DO in subsurface water in vegetated subsurface bed (VSB)wetlands is normally low.For example,DO concentrations averaged less than1ppm for VSB microcosm planted systems (Steinberg and Coonrod,1994).Many studies have shown that the oxygen release from roots of different macrophytes is far less than the amount needed for aerobic degradation of organic mat-ter and nitrification.Due to low DO in VSB wetlands,nitrification is considered the rate limiting step for nitrogen removal.Nitrifi-cation can occur at low DO,but the reaction rate is considerably less than that at DO levels greater than2mg/L(Grady et al., 1980).In order to improve the nitrification rate,aeration was employed to increase the dissolved oxygen and nitrification rate.But while the removal rate of NH3-N was increased,the removal rate of NO3-N was decreased(Green,1997).Wetlands have two environ-mental characteristics that promote denitrification:one is anoxic sediments,a requisite condition for denitrification(redox poten-tial<300mV);another is a source of carbon fuel for denitrification (Vymazal,2005).About87%of the nitrogen removal by the planted wetlands was due to denitrification,with13%due to accumula-tion in sediment and plant biomass.The plants(including plant litter)and influent organic matter were each responsible for about 50%of nitrogen removal,mainly through supplying organic carbon and creating anaerobic conditions for denitrification(van Oostrom, 1995;Newman et al.,2000).Denitrification of1g NO3-N to be N2,the organic material equivalent to2.86g BOD is needed.It was found that a C:N ratio(measured as mg BOD5:mgNO x-N) of less than2.3would limit denitrification rates.However,the decomposition of organic matter takes place mainly in the forepart of CWs,which results in a lack of organic matter in the back part of CWs and low denitrification.So nitrogen removal via the nitrification–denitrification coupling may be improved if a part of CWs is sufficient in oxygen to accomplish the nitrification of NH3-N;meanwhile another part of CWs is anoxic and BOD is enough to denitrify.Small-scale constructed wetlands for rural domestic wastewater treatment are a relatively new technology,and the physical,chem-ical and biological processes which facilitate treatment are still not well understood.In hybrid systems the advantage and disadvan-tage of SSHF and free-water surface(FWS)or subsurface vertical flow(SSVF)systems can be combined to complement each other. It is possible to produce an effluent in low COD(or BOD),which is fully nitrified and partly denitrified,and hence has a much lower TN concentration.The objectives of this study were:1.To evaluate the performance of the novel CW,towery hybrid con-structed wetland(THCW),especially nitrogen removal under a high hydraulic load.The THCW was designed to increase the nitrification rate by elevating the DO level in wastewater by pas-sive oxygenation due to a cascade-type current,and improve the denitrification rate by supplying a part of the wastewater directly into the middle part of the wetland,and then couple the nitrification–denitrification.2.To assess the effects of evergreen perennial woody plants andherbage plants together in THCW on removing nitrogen,espe-cially during winter season,and plant biomass contribution to nitrogen removal processes in this wetland.3.To investigate whether the hybrid system combined with SSHFand FWS exhibits better performance in removing or transform-ing wastewater pollutants,especially nitrogen.2.Materials and methods2.1.System descriptionA THCW system designed by our research group was constructed at a village in Northern Ningbo,China.It consists of three stages dimensioned for the equivalent of40people(PE)(Fig.1).The climate is characterized by an average rainfall of1300–1400mmF.Ye,Y.Li/Ecological Engineering35(2009)1043–10501045Fig.1.Flow diagram of towery hybrid constructed wetland:1,first stage;2,second towery stage;3,third stage(discharge);4,wetland plants;5,bottom circular cell;6, middle circular cell;7,upper circular cell;8,cascade.and an air temperature annual average of16.2◦C.Extremes vary between−4.2◦C at the lowest and38.8◦C at the highest.The cold period represents about3months from December to February and during this period the effluent mean temperature was close to8◦C with5.5◦C as the lowest.Thefirst and third stages were8m long and6m wide with a depth of1.0m.The beds were constituted of three layers,the lowest layer of washed gravel(2–6cm)with a depth of20cm,the middle layer offine gravel(0.5–2.0cm)with a depth of65cm,and the upper layer of soil(0.1–0.2cm)with a depth of15cm.The bottom slope was about1%.The second stage consisted of three circular cells with diameters of7m,5m and3m, respectively,from the bottom cell to the upper cell,each0.6m deep,providing approximately38.5m2of surface area.The over-flow from the upper cell drops into the lower cell immediately creating a turbulent cascade,which increases DO and maintains oxic conditions.The bottom of the wetland was lined with a high-density polyethylene liner and the circumference of the wetland was con-structed with approximately5cm of brick to eliminate seepage and mixing of wastewater with underground water.Seedlings of Pond Cypress(Taxodium ascendens)purchased from a nurs-ery were planted0.8m apart around the circumference of the bottom of the whole wetland,and Mat Rush(Schoenoplectus trigueter)was planted in the center of the bottom of the whole wetland in a density of approximately56plants per m2in November and harvested in May of the next year.Wild Rice shoots(Zizania aquatica)were planted in a density of approx-imately9plants per m2after the Mat Rush was harvested to grow from June to October.In the second stage,the upper circular cell was planted with Pygmy Waterlily(Nymphaea tetrag-ona)in a density of approximately6plants per m2,and the middle circular cell was planted with Narrow-leaved Cattail (Typha angustifolia)in a density of approximately36plants per m2.80%of the raw wastewaterflowed continuously into thefirst stage of the wetland.20%of the raw wastewater was pumped directly into the uppermost circular cell in the second stage of the wetland,and overflowed into the middle circular cell,then over-flowed to the bottom cell.This wastewater together with water from thefirst stageflowed into the third stage of the wetland,and discharged from the end of the third stage of the wetland.Water depth was controlled with a standpipe.In Phase1,the THCW was operated with a hydraulic loading of16cm/d(corresponding to HRT of5.4d)for4months(from May2006to August2006).In Phase2, the THCW was operated with a high hydraulic loading of32cm/d (corresponding to HRT of2.7d)for8months(from September2006 to April2007).The domestic wastewater was pretreated in a septic tank(Table1).2.2.Analytical procedure2.2.1.Chemical analysisWastewater samples were collected daily(regular working days) from the inlet of thefirst stage,outlet of the second stage(only during the Phase2test)and outlet of the third stage in the THCW wetland,and formed into weekly composite samples that were pre-served and analyzed for total suspended solid(TSS),COD,NH3-N, TN,and total phosphorous(TP).Weekly in situ temperature,pH and DO measurements of each stage and cell were made using an YSI probe.TSS,COD,TN,TP and NH3-N were determined according to the Standard Methods(APHA,1998).Wild Rice shoots(Z.aquatica)and Mat Rush(S.trigueter)were harvested(by cutting all visible portions above the water surface) in October2006and May2007,respectively.The harvested plants were washed in distilled water and dried in the sun for24h and later in an oven of105◦C for another24h.The plants were weighed before and after drying for water content analysis.The dried plants were powdered and prepared for total Kjeldahl nitrogen(TKN)anal-ysis according to the Standard Methods(APHA,1998).2.2.2.Measurement of nitrification and denitrificationThe potential nitrification activity(PNA)was determined on samples in the upper5cm of sediment taken from the front part of the third stage of the wetland.The test media used con-tained per litre:0.14g K2HPO4;0.027g KH2PO4;0.59g(NH4)2SO4;1.20g NaHCO3;0.3g CaCl2·2H2O;0.2g MgSO4;0.00625g FeSO4;0.00625g EDTA;1.06g NaClO3;the pH was7.5.Sodium chlorate was used to inhibit the oxidation of nitrite to nitrate.50mL sediment slurry samples were added to100mL of test media and incubated at 25◦C on a horizontal shaker at150rpm.Subsamples were collected after2,6,20,and24h of incubation.Nitrite concentrations were measured colorimetrically.PNA was calculated by angular coeffi-cient assessment of linear regression calculated for hours and the amount of nitrite produced.Results were normalized for volume loss during sampling,referred to by dry weight(DW)and expressed as nmol of nitrite per gram dry matter per hour.Potential denitrification rate(PDR)was measured using the acetylene inhibition technique.Sediment core samples were col-lected at four locations in the back part of the third stage(two located in bulk,two located in rhizome,diameter=3.5cm),and immediately wrapped tightly in aluminium foil to prevent diffu-sion of oxygen into the sediment cores.Each of these four samples were put into a1500mL Erlenmeyerflask,and incubated in water enriched with nutrients(15mg/L NO3-N,72mg/L Ca,10mg/L Mg, 27mg/L Na,39mg/L K and2.5mg/L PO4-P).The headspace of the flasks wasflushed with N2for30min.Theflasks were shaken on a rotary shaker at60rpm.The cores were incubated for8h in dark-1046 F.Ye,Y.Li /Ecological Engineering 35(2009)1043–1050Table 1Physical and chemical characteristics of influent and effluents from THCW.a .ParameterInfluentEffluent of the second stage in Phase 2Wetland effluent Removal rate (%)Phase 1Phase 2pH7.11(0.04)7.02(0.04) 6.98(0.05) 6.86(0.04)–TSS (mg/L)124.2(20.6)28.2*(3.6)16.6*(5.2)14.2*(5.6)88.57(16.3)DO (mg/L) 1.28(0.52) 2.98*(0.38) 2.04*(0.12) 2.22*(0.13)–CODcr (mg/L)320.2(13.9)119.2*(8.8)46.7*(5.1)49.3(13.9)84.60(9.6)NH 3-N (mg/L)45.6(1.8)12.6*(0.9)8.5*(1.1)7.7*(1.3)83.11(10.2)TN (mg/L)69.38(6.66)49.06(5.12)12.4*(4.1)11.9*(3.9)82.85(8.5)TP (mg/L)6.22(0.96) 2.91*(0.85) 2.06*(0.96)2.23*(0.96)64.15(7.9)aArithmetic mean (standard error in parentheses)of 62samples (4replicates/sample)collected weekly over 1-year period.Values followed by an asterisk are significantly different from the influent (p <0.05)within the same row.ness at 20◦C.Gas samples were taken with a syringe after each hour.Headspace samples were analyzed for N 2O concentration on a gas chromatograph (Shimadzu GC-14B)equipped with an elec-tron capture detector at an operating temperature of 340◦C.PDR was expressed as mg N 2O-N per m 2sediment per hour.2.2.3.Microbial number analysisThe nitrifying and denitrifying bacteria in the sediment of the wetland were enumerated using the most probable number (MPN)calculation (Carter and Gregorich,2006)using the follow-ing media.The medium for nitrifying bacteria:13.5g Na 2HPO 4;0.7g KH 2PO 4;0.1g MgSO 4·7H 2O;0.5g NaHCO 3;2.5g (NH 4)2SO 4;14.4mg FeCl 3·6H 2O;18.4mg CaCl 2·7H 2O;1L distilled water;pH 8.0.The medium for denitrifying bacteria: 1.0g KNO 3;0.1g Na 2HPO 4;2.0g Na 2S 2O 7;0.1g NaHCO 3;0.1g MgCl 2;1L distilled water;pH 7.0.The sediments for nitrifying and denitrifying bacteria measure-ments were removed from the sediment–water interface (0–2cm)and from a deeper level (5–8cm),respectively,with the aid of a 4.7cm (inner diameter)glass tube.Slime was scraped from rocks,rooted aquatic plant materials,and were then dispersed by blend-ing into the cold water with a mixer.Aliquots (1mL)of serial 10-fold sterile distilled water dilutions of the sediment sample were trans-ferred to 96-cell microtiter plates containing each type of mediumand incubated at 28◦C for 21d (nitrifying bacteria)and 5d (denitri-fying bacteria),respectively.In order to determine the dry weight of sediment samples,10g of sediment samples were oven-dried at 105◦C overnight to produce a constant weight.The amounts of nitrifying and denitrifying bacteria in the sediment were analyzed bimonthly during the wetland operation period.2.2.4.Statistical analysisSoftware SPSS was used for all statistical analyses with one-way ANOVA test.Differences were considered as significant if p <0.05.Significance of differences within means was evaluated with the Duncan’s test.Pearson’s correlations were used for significant lin-ear relationships assessment between PDA and hydraulic load,and PDR and hydraulic load.3.ResultsThe changes in the physico-chemical parameters at influent,effluent of the second stage during Phase 2and effluent of the third stage are presented in Table 1.Water pH did not change greatly.DO was relatively higher in effluent than influent as the result of passive oxygenation of the cascade overflow in the second stage of THCW.Mean DO increased from 1.28±0.52mg/L in influent to 2.98±0.38mg/L in effluent of the second stage during Phase 2Fig.2.COD,NH 3-N,TN and TP contents on influent and discharge ports as well as removal rates from THCW during operation period.F.Ye,Y.Li/Ecological Engineering35(2009)1043–10501047Fig.3.PNA(nmol/g DW/h)and PDR(mg N2O-N/m2/h)of sediment in third stage of THCW at the end of experiment.testing.The highest removal rate that was observed was for the TSS of88.57±16.3%.Organic matter measured as COD has shown removal of84.60±9.6%.Nitrogen removal was high and averaged 83.11±10.2%and82.85±8.5%for NH3-N and TN,respectively. However,at the end of the second stage during Phase2testing, NH3-N and TN removal rates were72%and29%,respectively.It suggested that a major amount of nitrogen was transformed into NO3-N by nitrification in the second stage and54%of nitrogen was removed by denitrification and/or other mechanisms in the third stage of the wetland.Phosphorus removal of64.15±7.9%was also observed.In comparison to results of Phase2,the greater removal for all measured pollutants took place during Phase1due to the lower hydraulic loading rate employed.But there were no signifi-cant differences in removal rates for all pollutants between the two hydraulic loads(p<0.02).Fig.2describes influent and effluent concentrations,as well as removal rates of CODcr,NH3-N,TN and TP during a12-month investigation period.During both Phase1and2of the study, NH3-N and TN had been removed efficiently over the12-month experiment.The highest nitrogen removal rates were observed during thefirst10weeks and the last10weeks when the water temperature was high.However,the wetland also showed high nitrogen,organic matter and phosphorus removal efficiencies dur-ing the winter season.Additionally,mean nitrogen loss attributed to nitrification–denitrification was significantly(p<0.003)higher during the summer than in winter.Ammonia volatilization may be ruled out since the maximum pH measured in the wetland was 7.7,and it should not have been sufficient for significant ammonia gas production.Also found were no statistically significant differ-ences between all average removals at two different hydraulic loads (16cm/d and32cm/d).As shown in Fig.2,phosphorus removal did not change signif-icantly during the operation period,even at the higher hydraulic load and in the winter season.There was no significant difference in TP effluent concentrations during winter and summer operations.As seen in Fig.3,PNA and PDR increased with time over thefirst 4months.About1month later when hydraulic loading was ele-vated from16cm/d to32cm/d,PNA decreased during October to December2006and PDR decreased during October2006to Jan-uary2007.Then PNA did not change significantly till the end of the test,and PDR increased a little.PNA and PDR tallied well with MPN counts of nitrifying bacteria and denitrifying bacteria,respectively, thus showing two good positive correlations(p<0.05).As seen in Table2,the numbers of nitrifying bacteria and denitri-fying bacteria in the sediment of the wetland were all in the range of104–105MPN/g sediment.A quantitative estimation of nitrify-ing and denitrifying bacteria and their corresponding PNA and PDR (Fig.3)in the sediment of the wetland indicated higher numbers of nitrifying bacteria than denitrifying bacteria,and higher activity of PNA.To show the effects of plant harvesting on nitrogen removal,TKN content in dried weight of harvested plants in October2006and May2007was measured.It showed a much larger nitrogen mass in Mat Rush(S.trigueter)than Wild Rice shoots(Z.aquatica).Average nitrogen contents in the dried plants were6.8±0.3/kg dry plant and 4.7±0.2/kg dry plant,and the TN uptake rates of these emergent plants were17.18kg/ha per day and12.63kg/ha per day for Mat Rush(S.trigueter)and Wild Rice shoots(Z.aquatica),respectively.4.DiscussionNitrification does not remove nitrogen from wastewaters.But nitrification coupled with denitrification seems to be the major removal process in many CWs.Nitrification occurs when oxygen is present in a high enough concentration to support the growth of strictly aerobic nitrifying bacteria.Nitrification takes place in all types of CWs;however,the extent of this process is determined by oxygen availability.As NH3-N is the dominant types of nitro-gen in many wastewaters,nitrification is a limiting process for nitrogen removal from most types of CWs.Denitrification is con-sidered as a major removal mechanism for nitrogen in most types of CWs.However,the concentrations of nitrates are usually very low in wastewater and,therefore,denitrification must be coupled with nitrification.Different requirements for the presence of oxy-gen for nitrification and denitrification are the major obstacle in many treatment wetlands for achieving higher nitrogen removal.It is generally accepted that DO concentrations above1.5mg/L are essential for nitrification to occur.In this wetland,average 2.22±0.13mg/L DO in outflow during the study,which most likely resulted from the tower type cascade in the middle of THCW, indicated that DO concentrations support nitrification;this result would be consistent with much more nitrifying bacteria in the sed-iment(Table2).High DO and available organic matter,due to the bypass of influent directly into the second stage,thereby reduced competition between heterotrophs and nitrifiers.More slow grow-ing nitrifying bacteria therefore colonized the rhizome and surface of the sediment.In THCW,the nitrogen load removal rate was about1440g N/m2 per year.As compared to other single and combined CWs(Table3), THCW exhibited higher removal rates of nitrogen than single CWs,and NH3-N removal rates were comparable to the results in the hybrid system.However,the TN removal rate was higher than that observed both in single wetland and combined systems (Cooper,1999;Platzer,1999;Kyambadde et al.,2005),suggest-Table2The amount of nitrifying bacteria and denitrifying bacteria in THCW.Bacteria Times12345MeanNitrifying bacteria(MPN/g sediment)8.89×104 2.55×105 3.67×105 3.16×105 4.23×105 2.90×105 Denitrifying bacteria(MPN/g sediment)9.12×1049.02×104 2.77×105 5.11×1057.03×105 3.34×1051048 F.Ye,Y.Li/Ecological Engineering35(2009)1043–1050Table3Removal of nitrogen in THCW and other various types of CWs.CW type Efficiency(%)in concentration(mg/L)Efficiency of TN load(g/m2/year)Ref.NH3-N TNFFP a–54.8b407b Vymazal(2007) FWS55.1c41.2d247d Vymazal(2007) SSHF48.3e42.3f250g Vymazal(2007) SSVF84.2h44.6i630j Vymazal(2007) SSVF–SSHF84––O’Hogain(2003) SSVF–SSHF78––Cooper(1999) SSHF–SSVF9761–Brix et al.(2003) SSHF–SSVF99–Laber et al.(2003) SSHF–SSVF–SSHF–SSVF–SSHF8086–Brix et al.(2003) SSVF–SSHF–FWS–65–Mander et al.(2003) SSHF–FWS–82–Masi et al.(2002) SSHF–FWS8481b–Vymazal(2005) This study(SSHF–FWS)8383(TKN)1440a Free-floating plant.b Mean values of14wetlands.c Mean values of64wetlands.d Mean values of247wetlands.e Mean values of151wetlands.f Mean values of137wetlands.g Mean values of113wetlands.h Mean values of80wetlands.i Mean values of51wetlands.j Mean values of42wetlands.ing that nitrification–denitrification coupling may be improved in this wetland.Several possible mechanisms for nitrogen removal in treatment wetlands are included,but the principal mechanism most often cited in long-term nitrogen removal is denitrification (Reed et al.,1995).The wetland also showed high nitrogen,organic matter and phosphorus removal efficiencies during the winter sea-son due to the presence of growing plants,such as Mat Rush(S. trigueter)and Pond Cypress(T.ascendens).Comparatively,this wetland exceeded reduction efficiencies of 60%reported for a FWS pilot wetland using duckweed for treat-ment of domestic primary effluent in Israel at a hydraulic load of 22cm/d with10–20%nitrogen removal and negligible phospho-rus removal(Ran et al.,2004).Although the hydraulic load was increased by about double in Phase2,TP removal efficiencies of this wetland remained high compared to Phase1and were in agreement with other studies(Kyambadde et al.,2005;Tuncsiper,2007).This supports the fact that the plants have limited ability for uptake of phosphorus nutrient and that adsorption or precipitation by bed media contributes to phosphorus removal.Phosphorus removal was also dependent on water temperature.Removal efficiencies for all measured pollutants were higher at lower hydraulic loading rates than those at higher hydraulic load-ing rates.Sun et al.(1998)had shown a decrease in organic removal with the increase in hydraulic load using an SSHF system at more than0.3kg/(m2d)hydraulic load which was similar to our wetland. However,thisfinding is in contrast to the FWS system with much lower loads.COD showed a decrease in hydraulic loads higher than 30cm/d when BOD5did not(Ran et al.,2004).This indicated that hydraulic efficiency is higher at lower hydraulic loads and varies between different configurations of CWs.COD removal rate was not as high as expected in THCW,which may be because of the bypass(about20%)of influent into the middle wetland,resulting in low HRT of this wastewater.NH3-N removal rate even at short HRT of2.7d in Phase2was comparable or greater than otherfindings in single wetlands(Kyambadde et al.,2005;Tuncsiper et al.,2006; Tuncsiper,2007).They also found that the highest removal efficien-cies were achieved at2d HRT in the SSHF,and6d HRT in the FWS and subsurfaceflow(SF)systems,suggesting that the longer HRT may be inefficient at nutrient removal.Reed and Brown(1995)sug-gested that to achieve low levels of ammonia(2mg/L)a6–8d HRT in the SF wetland must be maintained during the growing season.Commonly,the sediment is considered to be the site where the predominant denitrification occurs in wetlands.Denitrification in periphytic communities on submerged plants can make a sig-nificant contribution to overall denitrification in a wetland.PNA and PDR values obtained in THCW were higher than other reports (Bastviken et al.,2005),which perhaps contributed to higher lev-els of oxygen available for nitrifying bacteria and to the available organic carbon for denitrifying bacteria,as well as to the growth of mixed varieties plants in this wetland.Bachand and Horne(2000) noted a higher nitrate removal rate in wetlands containing mixed stands of emergent macrophytes than in those containing mono-culture.Bastviken et al.(2005)found that submerged plants exhibit a considerably higher denitrifying capacity than emergent plants. Although the macrophytes in this THCW were all emergent plants and a part of plants were harvested,the below-ground portion of the plants still remained in the wetland;these may provide organic carbon and be a suitable surface for bacterial attach-ment.DNA–DNA hybridization data indicated that most bacteria of the total population lived in the upper(5cm)soil layer.Hybridizations with all denitrification probes also showed that denitrifying bac-teria are enriched in the vicinity of plant roots,as compared to bulk,root-free soil(Joergensen,1989).So the sediments for nitri-fying and denitrifying bacteria measurements were removed from the sediment–water interface(0–2cm),and from a deeper level (5–8cm),paring the performance of the wetland over time,it suggested that microbial activity along with loading change was a little lag,and was not an accurate parameter.Higher DO concentration due to passive oxygenation resulting from the cascade current in the second stage of THCW may be contribut-ing to the higher PDR,and approximately two orders of magnitude higher numbers of nitrifying bacteria,and comparable denitrifying bacteria in this study as compared to that found in other reports (Bastviken et al.,2003;He et al.,2004).In sediments of a Danish fjord estuary,denitrification activity determined by15N isotope measurements and by the acetylene inhibition technique showed that denitrification capacity was high-。
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原文题目：Composite Box Girder Bridges
译文题目：混合箱梁桥
院系名称：土木建筑学院专业班级：土木工程F0905 学生姓名：学号： 200948040
指导教师：熊晓莉教师职称：
附件： 1.外文资料翻译译文；2.外文原文。
混合箱梁桥
摘要：在复合箱梁桥的建造过程中，独立梁的梁部分可能会扭曲，因此会增加建造的压力。
这种扭曲和附加的力可能会有效的减少简单的增加和经济的支撑系统。
在阻止扭曲的梁中这样一个系杆的作用从其他规模的模型中获得的结果，简单的工程理论和有限条法分析得到验证。
在梁中相互联系的系杆也被验证。
基于梁对各种各样轴心和偏心荷载的反应所推荐的初步设计也给出了。
14.1 介绍
背景
复合钢筋混凝土箱梁桥在最近几年已经被广泛的使用在中等跨度的桥梁中。
已建成的复合箱梁桥是非常稳定的，就像一个三面的钢筋盒子上面放了一个混凝土平板。
然而，在建造梁的过程中可能会有一个柔性的开口截面可能导致相当大的扭曲产生建造荷载。
开口截面梁的性质并未被很好的掌握，并且有文献报道在桥板安装前和安装时，存在着几何变形和过大的扭曲。
已经完成的结构看起来赏心悦目，由钢箱梁和复合材料制成的混凝土板构成。
在箱梁的设计中与类似的工字型梁和板梁相比更加经济，因为完全复合梁截面有更好的抗弯刚度和并能更好的活荷载水平分布，比起有相似韧性的工字梁结构。
在制造和树立箱梁时也可能会增加费用，比起类似的工字梁，由于风荷载和横向支撑系统。
对于完整的箱型结构来说多种多样的几何横截面是可能的，梁的数量从两个到六个或者更多取决于结构的设计平面几何。
典型的几何横截面在14.2中给出单轴和双轴的布置，浅的和深的无支撑的隔板也列举出来。
通常箱梁的中心线的间距从4.3到6.7米，混凝土板的计算高度为190mm到250mm。
因此，箱梁结构的恒载和活载的比例取决于板的厚度，横截面和间距的选取由设计工程师决定。
建造箱梁的经验表明设计说明并不对设计或者建造工程师提供足够的关于薄樯的箱梁在建造阶段的性能指导。
说明并未清晰的提到建造阶段的支撑需求。
中间隔板或横框可能需要在装配处理和安放混凝土板的时候保持每一根梁的几何横断面的形状。
类似的，隔板或横框在梁中间使用来确保稳定性和限制混凝土浇筑过程中限制水平位移大梁。
经常是总承包商或钢结构制造商负责支撑。
由于在设计中尤为强调的是桥梁的使用状况，所以设计工程师会经常忽略建造时的状况。
在这种情况下，承包商必须使用适宜的程序来支撑箱梁。
支撑的设计可能并不能阻止横向运动，也可能是
过度，造成浪费材料和劳动力以及与业主和承包商之间的冲突。
概述本文介绍了可能存在于薄壁箱梁施工过程中的负荷配置，并验证在典型的扭转半封闭的箱形梁产生的变形和应力。
基于模型试验和原型桥，辅以独立的开口、半封闭的箱形截面和复合部分的分析结果。
对一些支撑系统进行检查，主要包括支撑配置的跨度和一个给定的结构的横截面的功能的类型。
在施工期间，使用这些系统以尽量减少梁的横截面和整个梁的变形，这对设计工程师，制造商和普通承包者来说都更乐于接受。
14.2施工荷载
作为设计的一部分，设计工程师应选择一个符合高速公路的功能要求的横截面几何形状的桥梁结构。
在设计过程的早期阶段桥板相对于箱梁中心线和已经完成箱梁系统的位置已经被确定。
典型的截面几何形状连同各种负载情况下的示意图在两个例子中给出的，即图14,3。
轴心和偏心载荷的混凝土梁已经列出。
对于理想化的轴心加载情况下，板的重量由四个倾斜腹板共同承担。
一旦箱梁所承受的荷载沿中心线，扭曲的剪切中心将不会发生，弯曲和扭转载荷很容易识别。
压力法兰的支撑系统是必须的，以避免由于垂直载荷和水平方向的力的组合作用造成的横向移动或屈曲。
几何设计上的限制，可能会导致混凝土相对于单个梁的纵向中心线偏心（图
14.3）。
例如，设计者可能按照规范采取措施将悬臂梁上边选出部分控制到相邻相邻桥相邻上翼缘之间的距离百分之六十或少于两米。
偏心混凝土板导致荷载分布的不规整，弯曲和扭转载荷的发展，梁的剪切中心旋转产生垂直偏转和水平偏转。
对于轴心和偏心荷载来说，由于垂直荷载的作用约束对剪切中心有限制作用。
还应当提供的支撑约束扭转载荷。
约束扭转荷载很容易被设计成14.2中的系统1或者2.然而，一个同铰支座相连的标准隔横板（图14.2中的系统3）需要特殊设计和详细的链接和隔板构件图以确保有足够的刚度和抗扭刚度。
这后一种用单轴承和名义隔膜的系统不推荐使用。
可以给其他的附载在施工期间产生可预测的扭转效应;这些包括暴露的大梁的风荷载，整理机，和模板。
在每一种情况下，必须提供足够的扭转约束不仅保证了桥梁的整体稳定性的，但也限制单个梁的水平挠曲到可接受的水平。
扭转荷载的计算和因为风荷载，地震荷载产生的位移的计算可以再设计阶段用一些简化的假设来进行。
在施工期间也有其他的扭矩作用。
这些可能包括由总承包商选择的混凝土处理系统，或将桥面混凝土在非对称结构时的影响。
这些荷载的扭曲影响可以通过细致的规范来降低，而且这些相对于上述讨论的那些通常是很小的，
从加拿大三个独立的箱梁桥的设计图纸中总结出来的，弯曲和扭转载荷的总结在图14.4中。
对于设计师来说由混凝土和模板产生的弯矩导致剪心和隔板弯曲形式类似。
混凝土，模板和风力负荷相结合产生的弯曲类似于这些弯矩图。
在图中给出的均匀分布的荷载和均匀分布的弯矩为垂直风荷载值。
值中也给出的偏心率，e / b，其中，e是相对于主梁中心线的偏心的垂直载荷和b是框的平均宽度。
这些偏心率从0.04到0.12不等。
14.3行业通常做法
单个做法
一个不规则的箱梁截面的选择和面积比例由于扭转要遵循以下特点：
（a）扭转开口截面;
（b）半封闭的扭转截面，带有一个靠近凸缘水平的桁架系统;
（c）一个连接梁的顶部法兰的连续板的扭转的封闭截面。
在图14.5中示出的开口和半封闭截面。
扭转封闭截面很少用于复合桥梁结构，因为经济原因和在力作用下薄的封闭板确保稳定的困难。
因而，计算程序经常把封闭的截面作为一个理想化的半封闭截面。
当截面为任何形式的单跨桥受扭时，桥绕着剪心扭转，剪心的位置是所用截面的几何函数。
对于典型的开口截面的箱梁桥来说，剪切中心位大约位于中间部位，在梁底部边缘的下面。
对于具有长细比约200的的一个半封闭截面桁架式支撑系统，剪切中心的位置的稍上方的开口部分。
如果梁是一个封闭的截面，并有两个轴的对称结构，既有垂直腹板和等厚上下翼缘板，剪切中心和几何形心重合。
桥梁很少有这样的几何结构。
对于顶端的平面支撑法兰截面和扭转开口截面，剪切中心和旋转中心位于底部边缘以下。
横截面
在小跨度跨度箱形梁重力和扭转线荷载。
在重力荷载，刚性的部分偏转（纵向弯曲），变形（弯曲变形）。
在扭转载荷作用下，部分刚性旋转（混合扭转）和变形（扭转变形）。
纵向弯曲
当梁承受作用在剪切中心横向载荷，弯曲正应力也随之产生。
关联的剪切应力也可能会发生由于沿着梁的弯矩的变化。
这些可以从平衡考虑来计算。
这种分析是基于的的纳维假设和忽视由于引起的横截面变形位移的应力弯曲产生的剪切应变。
这些变形位移几乎是线性的，在腹板和法兰中受到剪切的影响为抛物线形。
也造成了弯曲正应力的从分配。
这种影响通常是小箱梁，大集中荷载作用下或薄，宽法兰梁除外。
混合扭矩
重力荷载不通过剪切中心时，梁的纵向轴线将会扭转变形。
如果扭转角度的变化比率是恒定的而且弯曲不受限制那么均匀扭转和相关联的剪切应力将会出现。
如果沿着梁的扭矩是变化的或者弯曲被阻止那么非均匀扭转（混合扭转）就会出现，纵向扭转弯曲应力继续增大。
这些应力的变化导致了在横截面弯曲剪应力的产生，这些应力加上圣维南应力来平衡截面中的总弯矩。
在开口箱梁中，扭矩主要由弯曲扭矩来平衡，因为圣维南扭矩的刚度相比较来说刚度比较小。