Collapse analysis of elastic-plastic trusses with unstable bars

Abstract

Large displacement analysis up to the collapse of trusses is considered. Bars are elastic-plastic and possibly unstable post-critical behaviour is accounted for. The collapse situation may correspond either to a limit point (snap-through buckling) or to the occurrence of bifurcation in Shanley's sense.Attention is mainly focused on the global stability test, which permits the collapse situation to be identified. It is shown that the test can be reduced to a check on the sign of a single number, which can be easily obtained for any given structural configuration. It is also shown how this test can be introduced into a large displacement elastic-plastic analysis code with little additional computational effort.