The response spectrum is very useful in dynamic analysis even though its use for multimass systems involves approximations as to modal combinations. It is especially useful in predicting effects of possible real earthquakes or of proposed nuclear detonations because it may be postulated or predicted much more readily than a complete time history of ground motion. The relationships of multimass system response—in terms of displacement, velocity, acceleration, force, shear, and moment—to elastic spectral response are given, together with examples taken from the AEC nuclear testing program in Nevada. The effects of relative building stiffnesses and stiffness taper on mode shape and thus on response are shown, as are the base shears relative to spectral response for several idealized fundamental mode shapes.

A Spectral Response Reconciliation procedure is presented and demonstrated by which procedure spectral response is reconciled with measured real building motion to obtain damping or other data under actual response to ground motion of any intensity. Damping values of highrise buildings are determined by this procedure.

Comparisons are made between 5 per cent damped response spectral values at the fundamental mode period of buildings and measured building motion.

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