Limit Loads for Layered Structures Using Extended Variational Principles and Repeated Elastic Finite Element Analysis

Layered structures are used in industry due to their better cost-to-strength and weight-to-strength performance compared with conventional structures. This paper presents a simple and systematic procedure to estimate the limit load for those layered structures that can undergo plastic collapse. The extended Mura’s variational principle is used in conjunction with repeated elastic finite element analyses (FEA). The elastic parameters are modified in order to ensure that the repeated analyses lead to a stress distribution close to the limit state. The secant modulus of a given element within the finite element discretization scheme is employed to simulate the plastic flow parameter $μ0,$ and rapid convergence of estimated multipliers to the exact value is achieved. By using the notion of “leap-frogging” to limit state, improved lower-bound values of limit loads have been obtained. The method has been applied to layered cylinders and beams.