Non-Linear Finite Element Analysis of RC Bridge Columns using the Softened Membrane Model T Ravi S Mullapudi, PhD Candidate, University of Houston, Texas, USA Ashraf Ayoub, PhD, Associate Professor, University of Houston, Texas, USA ABSTRACT This paper presents a non-linear finite element beam-column model applied to reinforced concrete bridge columns using a new set of constitutive laws based on the fixed angle softened membrane model. These newly developed constitutive laws can predict the concrete contribution, 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 subjected to both monotonic and cyclic loads. The constitutive relationships of the RC element were developed based on the smear behavior of cracked continuous orthotropic material assumption, 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 proved to be in good agreement with the experimental results.
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