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|Title||Non-Linear Finite Element Analysis of RC Beams With Special Detailing of Stirrups|
1 ABSTRACT The paper includes the development and application of a non-linear finite element model for studying the structural behavior of beams designed using a flexure-shear interaction model. A two-dimensional material model with elasto-plastic and quadratic hardening function is used for concrete. The model takes the influence of confinement due to stirrups into considerations. The cracks propagation is modeled using a rotating crack smeared model. A modified quadratic Lagrange isoparametric element is used for modeling the concrete. This modeling allows variable positions of the interior nodes on both the edge and within the element. A bilinear elasto-plastic model is used for steel. The effect of tension stiffening and tension softening is considered in the analysis. Each bar of the reinforcement is modeled using either a discrete or a smeared model. A quadratic one dimensional isoparametric element is used for steel. The flexure-shear interaction design model considers the influence of shear force on reducing the flexural capacity of beams. The full flexural capacity is achieved by providing the load path within the beam with confinement stirrups. The beneficial influence of confinement on the strength and ductility of concrete is utilized in preventing the brittle shear failure. The test results have confirmed the applicability of the developed non-linear finite element and the flexure-shear interaction models. There was a good matching between the test results and the finite element analysis. 2 INTRODUCTION Normal size and short beams subjected to transverse loading may fail by diagonal cracking due to shear if they are not provided with web reinforcement. Traditional design methods for shear [1,2] are based on truss analogy developed by Mrsh one century ago . These approaches do not necessary represent actual behavior of beams. They ignore the shear-flexure interaction behavior. The beam is first designed for flexure then checked for shear. The nominal (average) shear strength " bd V v = " assumed to occur on a section perpendicular to the beam axis is not a real indicator for shear strength of the beam since failure occurs along diagonal surface due the development of tensile stresses. The applied shear is assumed to be resisted by the concrete shear strength through beam and/or arch actions while the remaining shear is resisted by shear reinforcement through a truss action. The assumption of simultaneous occurrence of three actions to resist applied shear is totally unrealistic since this would result in strain incompatibility. Recognizing these limitations, a more realistic approach for shear design "flexure-shear interaction design model" has been developed based on actual behavior of beams .
|Published in||International Conference on Engineering and City Development|
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