The influence of elastic follow-up on the integrity of structures

Based on the traditional definitions associated with creep strain accumulation in defect free components, a generalised definition for “elastic follow-up” factor, Z, is proposed that characterises the influence of a “nonlinear” event experienced locally within a structure, i.e., creep, plasticity, cracking, growth of an existing crack, or any combination of such events, on the response of the structure to the applied loading. A “crack affected zone” approach is then outlined for evaluation of this parameter in a defective component. The significance of quantifying elastic follow-up in relation to integrity assessment procedures and the challenges facing its practical implication to the codes is discussed. The approach is finally examined through its application to two example problems; a standard test geometry, centre cracked plate and an external circumferential cracked thick cylinder, i.e., a conventional structural component.