CRITICAL EARTHQUAKE INPUT POWER SPECTRAL DENSITY-FUNCTION MODELS FOR ENGINEERING STRUCTURES

The problem of determining optimal power spectral density models for e arthquake excitation which satisfy constraints on total average power, zero crossing rate and which produce the highest response variance in a given linear system is considered. The solution to this problem is obtained using linear programming methods. The resulting solutions are shown to display a highly deterministic structure and, therefore, fai l to capture the stochastic nature of the input. A modification to the definition of critical excitation is proposed which takes into accoun t the entropy rate as a measure of uncertainty in the earthquake loads . The resulting problem is solved using calculus of variations and als o within linear programming framework. Illustrative examples on specif ying seismic inputs for a nuclear power plant and a tall earth dam are considered and the resulting solutions are shown to be realistic.