Non-Linear Finite Element Analysis of RC Bridge Columns Using the Softened Membrane Model

Abstract

This paper presents a nonlinear finite element model applied to various types of structures using a new set of constitutive models that adopt the fixed angle soften truss model and the soften membrane model. These newly developed constitutive laws can predict the concrete contribution V c which is produced by the shear resistance of concrete along the initial crack direction. A computer code was developed specifically for application to reinforced concrete structures by modifying the general purpose finite element program FEAP. The constitutive relationships of the RC element have been developed based on the smeared behavior of cracked continuous orthotropic material assumption of concrete with the inclusion of Poisson effect (mutual effect of the two normal strains). The concrete model accounts for the biaxial state of stress in the directions of orthotropy, in addition to degradation under reversed cyclic loading. The shear mechanism along the beam is modeled by using Timoshenko beam approach. Transverse strains are internal variables determined by imposing equilibrium between concrete and vertical steel stirrups. Element forces are obtained by performing equilibrium based numerical integration on section axial, flexural and shear behaviors along the length of the element. The predictions made by the new element are in good agreement with the experimental results.