RELIABILITY OF UNCERTAIN NONLINEAR TRUSSES UNDER RANDOM-EXCITATION .1.

This is the first part of a two-part investigation of reliability of n on-linear-truss structures with uncertain system parameters under rand om excitations. The objective is to develop a method of stochastic fin ite-element analysis for obtaining response statistics. The related re liability problem is considered in the companion paper. In this study, random excitations are modeled as filtered Gaussian white noises and uncertain system parameters are modeled as either random fields or ran dom variables. Structural nonlinear behavior due to both large deflect ion and inelastic deformation is considered. The structure is discreti zed via a total Lagrangian finite-element formulation that yields a se t of stochastic nonlinear equations of motion. An equivalent lineariza tion method in conjunction with a perturbation method is then develope d to solve for the total response statistics. No separate mesh for eac h random field is necessary in this formulation. Numerical examples in dicate that the proposed method yields accurate results with much less computer time compared with the Monte Carlo simulation method. It is found that the system uncertainties contribute significantly to the to tal response statistics.