土木外文翻译-高层建筑

Tall Building Structure

Tall buildings have fascinated mankind from the beginning of civilization, their construction being initially for defense and subsequently for ecclesiastical purposes. The growth in modern tall building construction, however, which began in the 1880s, has been largely for commercial and residential purposes.

Tall commercial buildings are primarily a response to the demand by business activities to be as close to each other, and to the city center, as possible, thereby putting intense pressure on the available land space. Also, because they form distinctive landmarks, tall commercial buildings are frequently developed in city centers as prestige symbols for corporate organizations. Further, the business and tourist community, with its increasing mobility, has fuelled a need for more, frequently high-rise, city center hotel accommodations.

The rapid growth of the urban population and the consequent pressure on limited space have considerably influenced city residential development. The high cost of land, the desire to avoid a continuous urban sprawl, and the need to preserve important agricultural production have all contributed to drive residential buildings upward.

Ideally, in the early stages of planning a building, the entire design team, including the architect, structural engineer, and services engineer, should collaborate to agree on a form of structure to satisfy their respective requirements of function, safety and serviceability, and servicing. A compromise between conflicting demands will be almost inevitable. In all but the very tallest structures, however, the structural arrangement will be subservient to the architectural requirements of space arrangement and aesthetics.

The two primary types of vertical load-resisting elements of tall buildings are columns and walls, the latter acting either independently

as shear walls or in assemblies as shear wall cores. The building function will lead naturally to the provision of walls to divide and enclose space, and of cores to contain and convey services such as elevators. Columns will be provided, in otherwise unsupported regions, to transmit gravity loads and, in some types of structure, horizontal loads also.

The inevitable primary function of the structural elements is to resist the gravity loading from the weight of the building and its contents. Since the loading on different floors tends to be similar, the weight of the floor system per unit floor area is approximately constant, regardless of the building height. Because the gravity load on the columns increases down the height of a building, the weight of columns per unit area increases approximately linearly with the building height.

The highly probable second function of the vertical structural elements is to resist also the parasitic load caused by wind and possibly earthquakes, whose magnitudes will be obtained from National Building Codes or wind tunnel studies. The bending moments on the building caused by these lateral forces increase with at least the square of the height, and their effects will become progressively more important as the building height increases.

Once the functional layout of the structure has been decided, the design process generally follows a well defined iterative procedure. Preliminary calculations for member sizes are usually based on gravity loading augmented by an arbitrary increment to account for wind forces. The cross-sectional areas of the vertical members will be based on the accumulated loadings from their associated tributary areas, with reductions to account for the probability that not all floors will be subjected simultaneously to their maximum live loading. The initial sizes of beams and slabs are normally based on moments and shears obtained from some simple method of gravity load analysis, or from codified mid and end