【正文】 other aspects of the deterministic structural respo nse,such as stresses,strains,internal forces,etc. ,are usually obtained as a secondary phase of the ana lysis, from the previously established displacement patterns. On the other hand,a nondeterministic analysis provides statistical information about the displacements which result from a statistically de fined loading. In this case,the time variation of the displacements is not determined,and other aspec ts of the response,such as stresses,internal forces, etc. , must be evaluated directly by independent nondeterministic analysis rather than from the displacement results. A structuraldynamic problem differs from its staticloading counterpart in two important respe cts. The first difference to be noted, by definition, is the timevarying nature of the dynamic proble m. Because the load and the response vary with time,it is evident that a dynamic problem does not have a single solution,as a static problem does. Instead the analyst must establish a succession of so lutions corresponding to all times of interest in the response history. Thus a dynamic analysis is cle arly more plex and timeconsuming than a static analysis. 10 However,a more fundamental distinction between static and dynamic problems is illustrated in Fig. 1. If a simple beam is subjected to a static load p ,as shown in Fig. )(a , its internal mome nts and shears and deflected shape depend directly upon the given load and can be puted from p by established principles of force equilibrium. On the other hand, if the load )(tp is applied dy namically,as shown in Fig. )(b , the resulting displacements of the beam are associated with accelra tions which produce inertia forces resisting the accelerations. Thus the internal moments and shears in the beam in Fig. )(b must equilibrate not only the externally applied force but also the inertia fo rces resulting from the accelerations of the beam. P )(a )(tP Inertia forces )(b Fig. 1 Basic difference between static and dynamic loads: )(a static loading。s function. It should not be in conf lict in terms of form. For example, a linear function demands a linear structure, and therefore it wo uld be improper to roof a bowling alley with a dome. Similarly, a theater must have large, unobstru ucted spans but a fine restaurant probably should not. Stated simply, the structure must be appropri ate to the function it is to shelter. Second, the structure must be fireresistant. It is obvious that the structural system must be a ble to maintain its integrity at least until the occupants are safely out. Building codes specify the nu mber of hours for which certain parts of a building must resist the heat without collapse. The struct ural materials used for those elements must be inherently fireresistant 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 buildingˊ 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 coordin ated as the design progresses. One can design in a sequential stepbystep manner within any one system, but the design of all of them should move in a parallel manner toward pletion. Spatially, all the various parts of a building are interdependent.