Effects of Peak Strain on Collapse Load Assessment

This paper discusses effects of peak plastic strain on collapse load assessment by Finite Element Analysis (FEA). A pressurized disk with a fixed end was investigated by limit analysis with various mesh division. The effect of peak strain at the periphery was evaluated how it would affect on the collapse load. It was found that not only the peak strain varied with the mesh size, but also the resulted plastic hinge changed its shape in the cross-sectional area. Nevertheless, the utmost load supported by elastic-perfectly plastic material was not affected much with the differences. In a limit analysis criterion, it is sometimes stipulated to terminate the calculation at the load increment when specified displacement or strain has been developed, so as to use the definitely lower bound of the true collapse load. Among such criteria, Twice-Elastic-Slope Method, which focuses on the gross displacement of the structure, gave comparable solutions for the various mesh divisions. On the contrary, when the peak strain was taken to be a controlling factor, the results were highly dependent on the modeling.