Structural reliability under evolutionary seismic excitation: Fid-Bau Portal

Structural reliability under evolutionary seismic excitation

Solomos, G.P. / Spanos, P-T.D.

Abstract Two approximate methods of obtaining survival probability estimates of a structure initially at rest, and subjected to a non-stationary seismic excitation have been presented. Both methods are based on approximating the response amplitude by a Markov process. In the first one, a discrete extreme point process has been utilized for the derivation of reliability estimates of the absolute response |x(t)|. In the second approach, similar estimates for the amplitude a(t) have been derived by solving by discretization an integral equation. The seismic excitations which have been considered are stationary processes modulated by exponential type deterministic functions. It has been found that, for this particular type of excitation, the structure experiences an early dramatic reduction of its survival probability as compared to that for the unmodulated excitation. Characteristic of the structural behavior is, also, the fact that for higher barriers the survival probability does not eventually tend to zero, as is the case for the stationary excitations, but it attains a constant non-zero value. Consequently for this case the concept of first-passage time density function is meaningless. Based on numerical data obtained by conducting digital Monte Carlo simulations it has been shown that the accuracies of the proposed methods are quite acceptable for common engineering applications.