外文翻譯tallbuildingstructure外文翻譯(存儲版)
【正文】 s 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 bee 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 crosssectional 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 span values. A check is then made on the maximum horizontal deflection, and the forces in the major structural members, using some rapid approximate analysis technique. If the deflection is excessive, or some of the members are inadequate, adjustments are made to the member sizes or the structural arrangement. If certain members attract excessive loads, the engineer may reduce their stiffness to redistribute the load to less heavily stressed ponents. The procedure of preliminary analysis, checking, and adjustment is repeated until a satisfactory solution is obtained. Invariably, alterations to the initial layout of the building will be required as the client39。 which may be stated in the following form: F=Ma In which F is a force that produces an acceleration a when acting on a body of mass M. This equation is nondimensional. For calculations M is set equal to W/g, then: F=W/g*a (1) In which F is in pounds, a is in feet per second per second, W is the weight of the body also in pounds and g is the acceleration of gravity, which is feet per second per second. Equation (1) is empirical. It simply states the experimental fact that for a free falling body the acceleration a is equal to g and the acceleration force F is then equal to the weight W. For convenience, the acceleration of an earthquake is generally expressed as a ratio to the acceleration of gravity. This ratio is called a seismic coefficient. The advantage of this system is that the force exerted on a body by acceleration is simply the corresponding seismic coefficient multiplied by the weight of the body. This is in accordance with Equation (1) in which a/g is the seismic coefficient. Activity of faults All faults are not considered to present the same ha
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