Damage Assessment for Steel Structures Subjected to cyclic pre-strain

Abstract

Plastic deformation provoked by unexpected events, such as earthquakes, can deteriorate the steel fracture toughness, and it can also induce premature failure of a structure and accidents. This study tries to formulate new equations to quantify the fracture toughness degradation of steel that was cyclic pre-strained. Four point bending tests were used to carry out the cyclic plastic pre-strain and Crack Tip Opening Displacement (CTOD) tests were conducted to compare pre-strained specimens with the steel without plastic deformation (as-received). The cumulative damage law was employed to account for the difference between each specimen, associated with Weibull stresses and critical CTOD values. Furthermore, additional Finite Element Method (FEM) simulations were conducted, using the new approach for the establishment an accurate Weibull Stress criterion, which can represent different cleavage fracture resistance according to the last pre-strain cycle. In the end, a new CTOD equation was also formulated using macro parameters, and it can account for the fracture toughness degradation of material that was subjected to cyclic plastic deformation.