A comparison of various plastic work curvature methods

• Different methods to determine collapse load, using curvature of a work vs load plot.
• Resulting collapse loads are compared to the load determined by the TES method.
• A curve fitting method is identified as being recommended for use.

The use of plastic work as a means of determining the plastic collapse load of a structure is a promising new approach. Several methods of assessing the plastic limit have been proposed in recent publications but there is, as yet, no clear consensus as to the best approach to take. This article compares the various methods proposed and recommends a new approach which is not subjective and which is considered to be more reliable than the twice elastic slope load.The recommended method plots normalised work versus normalised load, and uses a curve fitting method to estimate the plastic load. It is illustrated by application to several pressure vessels.