Abstract

This paper describes a three-dimensional nonlinear finite element techniques used to successfully model reinforced concrete beam-column joint specimens subjected to non-proportional axial and shear loads. A 20-noded isoparametric brick element had been used to model the concrete. The reinforcing steel bars were idealized as axial members embedded within the brick elements. Perfect bond between the concrete and the reinforcing bars was assumed. The behaviour of concrete in compression was simulated by an elasto-plastic work hardening model followed by a perfect plastic response, which was terminated at the onset of crushing. In tension, a fixed smeared crack model had been used with a tension-stiffening model to represent the retained post-cracking tensile stresses and a shear retention model that modified the shear modulus after cracking. The nonlinear equations of equilibrium have been solved using an incremental-iterative technique operating under load control. The solution algorithms used were the standard and modified Newton-Raphson method. The numerical integration has been conducted using the 27-point Gaussian type rule. Two types of reinforced concrete beam-column joints had been analyzed and the finite element solutions were compared with the experimental data. Several parametric studies have been carried out to investigate the effect of some important finite element and material parameters on the predicted finite element results. The study included the effect of concrete compressive strength, column axial load, beam tension and compression reinforcement, and beam shear span to depth ratio