Fatigue Reliability under Nonstationary Loads: Model Formulation

Abstract

This paper develops a method for predicting the expected low‐cycle fatigue damage in structures subjected to nonstationary loading processes. The load is a filtered Gaussian random process of limited duration. The resulting strain‐response process in a given structural component determines the fatigue damage of the component. The fatigue analysis is based on a recursive definition of waiting‐time distributions for range‐pair cycles. The range‐pair waiting‐time distribution is derived from the crossing rate of the strain‐response process through strain‐range limits. The waiting‐time distributions determine the probability that a given number of range‐pair cycles will occur through the duration of the response. The damage is assumed to accumulate linearly according to the Manson‐Coffin relationship. The methodology is applied numerically to a spherical storage tank subjected to a moderate earthquake. The expected damage correlates well with the results of a Monte‐Carlo simulation, indicating that the methodology can be successfully implemented for loadings of limited duration.