Elastic-Plastic Analysis of Framed Structures under Cyclic Loads by Plastic Node Method

Abstract

Extending the basic theory of Plastic Node Method (PNM), a new method of elastic-plastic analysis of framed structures considering combined strain-hardening effects is developed. The proposed method is applied to two and three-dimensional frames under cyclic loads. In the PNM, a generalized hinge mechanism (plastic node) based on the flow theory of plasticity is introduced at a node of beam-column elements. A strain-hardening rate for the plastic node is obtained by equating a plastic work done at the plastic node with that evaluated in the actual elastic-plastic stress distribution in the element. The resulting elastic-plastic stiffness matrix can be derived simply by matrix calculation. The numerical results are compared with those calculated by FEM program MARC. It was shown that the proposed. method provides very accurate results in a short computation time.