TIME-DEPENDENT RESISTANCE DETERIORATION IN PROBABILISTIC STRUCTURAL SYSTEMS

Resistance deterioration which is purely a time function such as typif ied by simple corrosion problems is considered herein for structural s ystems subjected to one or more stochastic load processes. The resista nces are modelled as Gaussian random variables and the loads as Gaussi an random processes. Deterioration is considered by either of two simp le models-exponential or parabolic functions of time. Both an upcrossi ng and an outcrossing formulation is used to estimate the up (out) cro ssing rate through linear domain boundaries. Numerical integration is employed to evaluate the resulting integrals, although significant sim plifications are occasioned through the use of Gaussian random Variabl es and processes. Results are given for two simple structural examples and compared to purely simulation results both for the outcrossing ra te and for various sensitivity results. Good agreement is found. The r esults suggest that results for failure probability based on mean valu es of the deterioration models may be satisfactory in some cases.