Author(s)

F. Trentadue & G. C. Marano

Abstract

In this work a new method for the optimal design of general elastic structures subject to random dynamic loads is proposed. Elastic structures are described as deterministic lumped multi degree of freedom systems and are based on structural collapse probability minimization, referred to first crossing passage failure case. The method here is applied to the shape optimization of a vertical column with a given extra-mass at the free top end, subject to a base acceleration modelled as a Gaussian stationary white noise, filtered throughout a second order linear oscillator. In a finite number of column cross sections the elastic threshold crossing probability is a determined and objective function assumed to be a measure of these probabilities. This measure of reliability is maximized under a constant weight constraint (or even under more general conditions). 1 Introduction In many structural dynamic problems actions related to natural phenomena, as seismic actions, wind loads and waves forces, have an intrinsic uncertain character. These actions, modeled as stochastic processes, induce a structural response that is a stochastic process too. Confident of these reasons, since the 60 years, in the field of structural dynamic the deterministic approach, where forces and structural response are assumed as exactly known quantities, has been surpassed thanks to the understanding that the stochastic approach consents a more realistic evaluation of structural reliability. Anyway, it is important to notice that forces acting on structures are not the only sources of uncertainness in structural analysis, but many other physical

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