Reliability assessment of structural systems with interval uncertainties under spectrum-compatible seismic excitations

The paper deals with reliability assessment of linear structures with interval parameters subjected to seismic excitations modeled as stationary spectrum-compatible Gaussian random processes. Under the Vanmarcke assumption that the up-crossings of a specified threshold occur in clumps, an efficient procedure for the evaluation of the bounds of the interval reliability function of the generic response process is presented. The key idea is to view the interval reliability function as depending on the first three interval spectral moments of the structural response rather than on the interval structural parameters. Then, the lower and upper bounds of the interval reliability function are obtained by properly combining the bounds of the interval spectral moments. Such bounds are evaluated in approximate form by applying an approach recently proposed by the authors. Finally, based on the knowledge of the interval reliability function, a method for evaluating the interval survival probability of a structural element with imprecise strength probability density function is developed.