Adaptive Space Frame Analysis: Part Ii, a Distributed Plasticity Approach

In a previous companion paper (Part I: A Plastic Hinge Approach), adaptive elasto-plastic analysis of space frames was discussed in the context of a plastic hinge approach. The present paper extends the concept of automatic mesh refinement to deal with accurate elasto-plastic large displacement analysis accounting for the spread of yield within structural members. This is achieved through the use of the quartic formulation in the elastic range, and performing automatic subdivision of quartic elements into elasto-plastic cubic elements which account for the spread of plasticity across the section depth and along the element length. The main advantage of this approach is the ability to start full elasto-plastic large displacement analysis using only one element per member, with automatic mesh refinement performed only where and when necessary within the structure and during the analysis. The paper presents a description of the elasto-plastic cubic formulation, discusses the concept of automatic mesh refinement in the context of elastoplastic analysis, and provides verification examples using the computer program ADAPTIC to demonstrate the accuracy and extreme efficiency of the proposed nonlinear analysis procedure.