Abstract
A general purpose finite element computer program has been written for the large-deflection, elasto-plastic analysis of plate assemblages upto and including collapse. The approximate Ilyushin's yield criterion has been adopted, where sudden plastic flow in the full section depth of the plate is assumed. The program has been compared with other theoretical and experimental treatments, and gives acceptable results. In the present work, the computer program has been used to study the interaction between the webs, flanges and diaphragm on the collapse behaviour of single cell rectangular box girders in the support region. A special beam element has been incorporated into the program to represent portions of the structure away from the support that may be assumed to behave in a linear elastic manner. The imperfection sensitivity of the box whose dimensions are shown to be in a critical range regarding interaction between two types of collapse has been established. Suggestions are made for a simplified two dimensional treatment to give safe values of collapse load involving the flange-diaphragm interaction.