领域：学术论文 · 应用学科

Apart from these three primary requirements, several other factors are worthy of emphasis. First, the structure or structural 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 occupants are safely out. Building codes specify the number of hours for which certain parts of a building must resist the heat without collapsing. The structural materials used for those elements must be inherently fire-resistant or be adequately 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 high-rise frame that sways considerably in the wind might not actually be dangerous, but may make the building uninhabitable just the same. Lightweight floor systems that are too "bouncy" can make the users very uncomfortable. Large glass windows, uninterrupted by dividing motions, can be quite safe but will appear very insecure to the occupant standing next to them 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 the development of this "sense". Structural analysis is the process of determining the forces and deformations in structures due to specified loads, allowing for rational design and ensuring that the safety of existing structures can be checked.

In the design of structures, it is necessary to start with a concept leading to a configuration that 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. The collapse of a structure will usually occur only long after the elastic range of the materials has been exceeded at critical 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. Nevertheless, 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 reason, only the elastic theory structure is pursued in this chapter.

Looked at critically, all structures are assemblies of three-dimensional elements, the exact analysis of which is a forbidding 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 that 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 columns 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 Iso, 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 entire 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 are 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 out 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 ", are 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 basics of matrix structural analysis and its use in digital computers, as well as in the use of available analysis programs or software.

翻译考点：
考点1：bouncy 可直译为 弹性，或意译为 晃动。
考点2：serviceability 译为 适用性。
考点3：working condition 译为 正常使用状态。
考点4：followed 需译为 “使用”或“应用”，不可直译为 遵循。
考点5：distributed loads 需译为 分布荷载。