Cyclic Softened Membrane Model for Nonlinear Finite Element Analysis of Concrete Structures

Abstract

This paper describes how a Cyclic Softened Membrane Model (CSMM) was developed to rationally predict the cyclic shear responses of reinforced concrete (RC) elements, including the pinching effect in the hysteretic loops, the shear stiffness, the shear ductility and the energy dissipation capacities. This CSMM model was verified by the tests of fifteen RC panels at the University of Houston. The test results confirmed that the orientation of the steel bars and the percentage of steel in a panel are the two most important variables that influence the cyclic response of RC panel elements. Using OpenSees as a framework, the concept of the CSMM was simplified from a 2-D model into a 1-D model and implemented into a finite fiber element program for the prediction of concrete frame structures subjected to cyclic or dynamic loading. The developed program is validated by the reversed cyclic load tests of a reinforced concrete column and by the shake table tests of a prestressed concrete frame. The CSMM has recently been implemented into an OpenSees-based finite element program for a 2-D RC element that will allow structural engineers to predict the monotonic, cyclic and dynamic responses of structures containing walls. This 2-D RC element is validated in this paper by the prediction of the monotonic responses of two RC panels subjected to shear stresses.