RELIABILITY OF PIECEWISE LINEAR SYSTEMS SUBJECT TO STOCHASTIC EXCITATIONS

Abstract eng:
This work investigates the reliability of nonlinear elastic and inelastic systems arising in mechanical and civil engineering applications due to impacts between structural parts. These systems are modeled by single and multi-degree of freedom models with piecewise linear elastic stiffness elements and often involve strong inelastic behavior in parts of the system. In order to gain useful insight into the behavior of these systems, one degree of freedom piecewise linear elastic and inelastic systems are first analyzed and the behavior to long duration transient stochastic excitations is investigated. Using subset simulation method, probabilistic response spectra characteristics and estimates of the sensitivity of these spectra to uncertainties in system and loading parameters, such as initial modal frequency, stiffness ratios, size of gaps, inelastic parameters, damping values, excitation strength and frequency content, are obtained. It is shown that the performance of such systems to uncertain stochastic excitation (sinusoid pulse or earthquake type) can be enhanced by optimally designing the system parameter values. The methodology is used to investigate the reliability of the four-span Kavala bridge (Greece) under stochastic earthquake excitations. The bridge deck is supported on columns through elastomeric bearings, allowing impacts to occur between the deck structure and the piers. Short duration sinusoid pulse excitations with uncertain characteristics as well as white noise stochastic excitations are used to simulate the short and moderate duration earthquake excitations and the sensitivity of the reliability to the size of gaps affecting the behavior of the bridge is explored.

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