Elastic-Plastic Design by Analysis for Gross Plastic Collapse

An investigation of the ASME VIII Div 2 elastic-plastic stress analysis method for protection against plastic collapse is presented. Four example configurations are considered and calculated design pressures are compared with values determined by alternative procedures based on limit analysis and bilinear hardening/the twice elastic slope criterion. It is found that the ASME VIII Div 2 procedure does not generally lead to evaluation of higher design pressures than the alternative approaches. In an example configuration demonstrating significant geometric strengthening, the allowable load is limited by the local strain criterion and in practice user-defined service criteria would be applied to limit permanent deformation under design conditions. In two example configurations that failed through membrane action, the evaluated design pressure was found to be less than that based on limit analysis. These initial results indicate that the more complex elastic-plastic stress analysis used in the ASME VIII Div 2 method does not necessarily lead to evaluation of higher design loads than alternative design routes. Further studies are required to determine the general circumstances in which the more complex analysis method is advantageous in design.