ABSTRACT
The fatigue assessment is based on probabilistic models of fatigue loading and fatigue resistance (related to S-N curves). However, the fatigue reliability of a welded connection cannot be expressed simply in terms of a separable ‘‘load’’ and ‘‘resistance’’ because the failure criterion (limit state) is related to a cumulative fatigue damage indicator (normally based on the Palmgren-Miner summation) that is a function of both a load spectrum and a corresponding resistance spectrum (for variable stress ranges). Furthermore, the resistance spectra are based on S-N curves that have discontinuities associated with ‘‘constant stress range fatigue limits’’ and ‘‘cut-off limits’’, at low stresses. Hence, fatigue damage is a highly non-linear function of the levels of fatigue loading and fatigue strengths. Accordingly, the proposed method of reliability assessment is based on the summation of conditional probabilities of failure for various levels of fatigue strengths.
