Proposal of Failure Mode Map Under Dynamic Loading—Ratcheting and Collapse

Abstract

Ratcheting, collapse, and fatigue are the probable failure modes which can occur under alternate dynamic loading like seismic loading. The objective of this study is to propose a failure mode map for rectangular beams by determining the conditions of occurrence of the ratcheting and collapse failure modes. The paper considers the analogy between thermal ratcheting and dynamic ratcheting. The nonlinear dynamic finite element method was used to analyze a rectangular beam model for different loading conditions. The results were plotted on a nondimensional primary and secondary stress parameter graph similar to the Bree diagram for thermal ratcheting. The similarity between thermal load and dynamic load was observed. The main difference between thermal and dynamic loading is the effect of the frequency of dynamic loading on the occurrence of ratcheting and collapse. Experimental observations of ratcheting have been obtained and are used for comparison to validate the analytical predictions. From the above results, a failure mode map has been proposed which can evaluate the occurrence conditions of ratcheting and collapse under dynamic loadings.