Automatic computation of plastic collapse loads for frames

Abstract

This paper describes an automatic approach to the determination of plastic collapse loads for plane frames using the kinematic method. An algorithm is developed to determine the elementary collapse mechanisms for an arbitrary frame. These mechanisms are then combined in a systematic manner using a recursive algorithm in order to find the mechanism with the lowest collapse load. Since all potential collapse mechanisms are investigated, the method is able to find alternative collapse mechanisms with the same load factor, and indeed the lowest n collapse mechanisms. The approach is applied to three examples, and is shown to be accurate and capable of practical application. A complete C++ program listing is included.