Authors
Abstract
This paper describes a three- dimensional nonlinear finite element model suitable for the analysis of reinforced concrete Beams with Large Opening under Flexure. The 20-node isoparametric brick elements have been used to model the concrete. The nonlinear equations of equilibrium have been solved using an incremental-iterative technique operating under load control. The solution algorithm used was the modified Newton-Raphson method. The numerical integration has been conducted using the 27-point Gaussian type rule. The reinforcing bars are idealized as axial members embedded within the concrete element and perfect bond between the concrete and the reinforcement has been assumed to occur. The behavior of concrete in compression is modeled using an elasto-plastic work hardening model followed by a perfectly plastic response, which is terminated at the onset of crushing. In tension, a smeared crack model with fixed orthogonal cracks has been used with the inclusion of models for the retained post-cracking tensile stress and the reduced shear modulus. Different types of reinforced concrete beams with large rectangular transverse openings have been analyzed and the finite element solutions are compared with the experimental data. Generally, good agreement has been obtained between the numerical and experimental load-deflection curves and ultimate load. Numerical studies including some material parameters such as concrete compressive strength, amount of longitudinal tensile reinforcement and opening size on the load-deflection response have been carried out to study their effect on the over all behavior of reinforced concrete beams with Large opening under Flexure.The finite element solution revealed that the ultimate load and post-cracking stiffness increase with the increases of concrete compressive strength, increases with the increase of the bottom steel reinforcement amount and decreases with the increase of length or depth of opening.
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