土木工程英语论文.docx

1、土木工程英语论文Structure of BulidingsA building is closely bound up with people, for it provides people with the necessary space to work and live in. As classified by their use, buildings are mainly of two types: industrial buildings and civil buildings. Industrial buildings are used by various factories o

2、r industrial production while civil buildings are those that are used by people for dwelling, employment, education and other social activities.The construction of industrial buildings is the same as that of civil buildings. However, industrial and civil buildings differ in the material used, and in

3、 the structure forms or systems they are used.Considering only the engineering essentials, the structure of a building can be difined as the assemblage of those parts which exist for the purpose of maintaining shape and stability. Is primy purpose is to resist any loads applied to the building and t

4、o transmit those to the ground.In terms of architecture, the structue of a building is and dose much more than that. It is an inseparable part of the building form to varying degrees is a generator of that form. Used skillfully, the building structure can establish or reinforce orders and rhythms am

5、ong the architecture volumes and planes. It can be visually dominant or recessive. It can develop harmonies or conflicts. It can be both confining and emincipating. And, unfortunately in some cases, it cannot be ingored. It is physical.The structure must also be engineered to maintain the architectu

6、re form. The principles and tools of physics teand mathematics provide the basis for differentiating between rational and inrational forms in terms of construction. Artists can sometimes generate shapes that obviate any consideration of science, but architects cannot.There are at least three items t

7、hat must be present in the structure of a building: stabily, strength and stiffness, economy.Taking the first of the three requiements, it is obvious that stability is needed to maintain shape. An unstable building structure implies unbalanced forces or a lack of equilibrium and a consequent acceler

8、ation of the structure or its pieces.The requirement of strength means that the materials selected to resist the stresses generated by the loads and shapes of the structure(s) must be adequate. Indeed, a “factor of safety” is usually provided so that under the anticipated loads, a given material is

9、not stressed to a level even close to its rupture point. The material property called stiffness is considered with the requirement of strength. Stiffness is different form strength in that it directly involves how much a structure strains or deflects under load. A material that is very strong but la

10、cking in stiffness will deform too much to be of value in resisting the forces applied.Economy of a building structure refers to more than just the cost of the material used. Construction economy is a complicated subject invovling raw materials, fabrication, erection, and maintenance. Design and con

11、struction labor costs and the costs of energy consumption money(interest) are consumption must be consiedered. Speed of construction and the cost of money(interest) are also factors. In most design situations, more than one structural material requires consideration. Completive alternatives almost a

12、lways exist, and the choice is seldom obvious.Apart form these three primary requirements, several other factors are worthy of emphasis. First, the structure or suctructural system must relate to the buildings function. It should not be in conflict in terms of form. For example, a linear function de

13、mands a linear structure, and therefore it would be improper to roof a bowling alley with a dome. Similarly, a theater must have large, unobstructed spans but a fine restaurant probably should not. Stated simply, the structure must be appropriate to the function it is to shelter.Second, the structur

14、e must be fire-resistant. It is obvious that the structural system must be able to maintain its integrity at least until the occupuants are safely out. Building codes specify the number of hours for which certain parts of a building must resist the heat without collapse. The structural materials use

15、d for those elements must be inherently fire-resistant or be adequently protected by fireproofing materials. The degree of fire resistance to be provided will depend upon a number of items, including the use and occupancy load of the space, its dimensions, and the location of the building.Third, the

16、 structure should integrate well with the buildings circulation systems. It should not be in conflict with the piping systems for water and waste, the ducting systems for air, or (most important) the movement of people. It is obvious that the various building systems must be coordinated as the desig

17、n progresses. One can design in a sequential step-by-step manner within any one system, but the design of all of them should move in a parallel manner toward completion. Spatially, all the various parts of a building are interdependent.Fourth, the structure must be psychologically safe as well as ph

18、ysically safe. A highrise frame that sways considerably in the wind might not actually be dangerous but may make the building uninhabitable just the same. Ligheweight floor systems that are too “bouncy” can make the users very uncomfortable. Large glass windows, uninterrupted by dividing motions, ca

19、n bu quite safe but will appear very insecure to the occupant standing next to on 40 floors above the street.Sometimes the architect must make deliberate attempts to increase the apparent strength or solidness of the structure. This apparent safety may be more important than honestly expressing the

20、buildings structure, because the untrained viewer cannot distinguish between real and perceived safety.The building designer needs to understand the behavior of physical structures under load. An ability to intuit or “feel” structural behavior is possessed by those having much experience involving s

21、tructural analysis, both qualitative and quantitative. The consequent knowledge of how forces, stresses, and deformations build up in different materials and shapes is vital to development of this “sense”. Structural analysis is the process of determining the forces and deformations in structures du

22、e to specified loads so that the structure can be designed rationally, and so that the state of safety of existing structures can be checked.In the design of structures, it is necessary to start with a concept leading to a configuration which can then be analyzed. This is done to members can be size

23、d and the needed reinforcing determined, in order to: a) carry the design loads without distress or excessive deformations ( serviceability or working condition); and b) to prevent collapse before a specified overload has been placed on the structure (safety or ultimate condition).Since normally ela

24、stic conditions will prevail under working loads, a structural theory based on the assumptions of elastic behavior is appropriate for determining serviceability conditions. Collapse of a structure will usually occur only long after the elastic range of the materials has been exceeded at circal point

25、s, so that an ultimate strength theory based on the inelastic behavior of the material is necessary for a rational determination of the safety of a structure against collapse. Neverthelese, an elastic theory can be used to determine a safe approximation to the strength of ductile structures (the low

26、er bound approach of plasticity), and this approach is customarily followed in reinforced concrete practice. For this reasion only the elastic theory of gtructure is pursued in this chapter.Looked at critically, all structures are assemblies of three-dimensional elements, the exact analysis of which

27、 is a forbdding task even under ideal conditions and impossible to contemplate under conditions of professional practice. For this reason, an important part of the analysts work is the simplification of the actual structure and loading conditions to a model which is susceptible to rational analysis.

28、Thus, a structural framing system is decomposed into a slab and floor beams which in turn frame into girders carried by colums which transmit the loads to the foundations. Since traditional structural analysis has been unable to cope with the action of the slab, this has often been idealized into a

29、system of strips acting as beams. A lso, long-hand methods have been unable to cope with three-dimensional framing systems, so that the entire structure has been modeled by a system of planner subassemblies, to be analyzed one at a time. The modern matrix-computer methods have revolutionized structu

30、ral analysis by making it possible to analyze entrie systems, thus leading to more reliable predictions about the behavior of structures under loads.Actual loading conditions are also both difficult to determine and to express realistically, and must be simplified for purposes of analysis. Thus, tra

31、ffic loads on a bridge structure, which are essentially both of dynamic and random nature, are usually idealized into statically moving standard trucks, or distributed loads, intended to simulate the most severe loading conditions occurring in practice.Similary, continuous beams are sometimes reduce

32、d to simple beams, rigid joints to pin-joints, fillers-walls are neglected, shear walls considered as beams; in deciding how to model a structure so as to make it reasonably realistic but at the same time reasonably simple, the analyst must remember that each such idealization will make the soulatio

33、n more suspect. The more realistic the analysis, the greater will be the confidence which it inspires, and the smaller may be the safety factor ( or factor of ignorance ). Thus, unless code provisions control, the engineer must evaluate the extra expense of a thorough analysis as compared to possible savings in the structure.The most important u