The Most Degrading Postbuckling Mode of Pin-Jointed Structures

This paper describes a numerical method which is used to determine the most unstable postbuckling mode capable of developing at the ultimate critical state of complex pin-jointed structures. In this method, the set of independent variables are the flexural shortenings of those members that are a subset of the critically loaded members in the lattice structure. This choice of independent variables greatly simplifies the analysis and promotes the evaluation of the most degrading mode under both equilibrium and collapse conditions. In this Technical Note, this method is used to evaluate these two modes for some rather simple structures. The deformed modes are plotted in each case and differences between the most degrading mode under equilibrium and collapse conditions are noted.