Structure of Bulidings 土木工程毕业论文外文资料翻译

Structure of Bulidings

A 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 or 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 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 to 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 among 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 architecture 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 that 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 acceleration 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 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 lacking 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 construction 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 always 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 building’s function. It should not be in conflict in terms of form. For example, a linear function demands 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 structure 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 used 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 structure should integrate well with the building’s 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 design 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 physically 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, can 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 building’s 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 structural 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 due 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 sized 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 elastic 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 points, 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 lower 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 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 analyst’s work is the simplification of the actual structure and loading conditions to a model which is susceptible to rational analysis.

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 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 structural 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, traffic 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 reduced 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 soulation 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 use of structure analysis is as a tool in structural design. As such, it will usually be a part of a trial-and-error procedure, in which an assumed configuration with assumed dead loads is analyzed, and the members designed in accordance with the results of the

analysis. This phase is called the preliminary design; since this design is still subject to change, usually a crude, fast analysis method is adequate. At this stage, the cost of the structure is estimated, loads and member properties are revised, and the design is checked for possible improvements. The changes are now incorporated in the structure, a more refined analysis is performed, and the member design is revised. This project is carried to convergence, the rapidity of which will depend on the capability of the designer. It is clear that a variety of analysis methods, ranging from “ quick and dirty to exact ”, is needed for design purposes.

An efficient analyst must thus be in command of the rigorous methods of analysis, must be able to reduce these to shortcut methods by appropriate assumptions, and must be aware of available design and analysis aids, as well as simplification permitted by applicable building codes. An up-to-date analyst must likewise be versed in the bases of matrix structural analysis and its use in digital computers as well as in the use of available analysis programs or software.

建筑结构

建筑物与人类有着密切的关系，它能为人们在其中工作和生活提供必要的空间。根据其功能不同，建筑物主要有两大类：工业建筑和民用建筑。工业建筑有各种工厂或制造厂，而民用建筑指的是那些人们用以居住、工作、教育或其他社会活动的场所。

工业建筑的建造与民用建筑相同，但两者在选用的材料、结构形式或体系方面是有差别的。

就工程的实质而言，建筑结构可定义为：以保持形状和稳定为目的的各个基本构件的组合体。其基本目的是抵抗作用在建筑物上的各种荷载并把它传到地基上。

从建筑学的角度来讲，建筑结构并非仅仅如此。它与建筑风格是不可分割的，在不同程度上是一种建筑风格的体现。如能巧妙地设计建筑结构，则可建立或加强建筑空间与建筑平面之间的格调与节奏。它在直观上可以是显性的或是隐性的。它能产生和谐体或对照体。它可能既局限又开放。不幸的是，在一些情况下，它不能被忽视。它是实际存在的。

结构设计还必须与建筑风格相吻合。物理学和数学的原理及工具为区分在结构上的合理和不合理的形式提供了依据。艺术家有时可以不必考虑科学就能画出图形，但建筑师却不行。在建筑结构中至少应包括三项内容：稳定性、强度和刚度，经济性。

在上述三种要求中，首先是稳定性。它在保持建筑物形状上是必不可少的。一座不稳定的建筑结构意味着有不平衡的力或失去平衡状

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