Ductility Analysis of RC Beams Considering the Concrete Confinement Effect Produced by the Shear Reinforcement: a Numerical Approach

Abstract In this paper, a simplified numerical approach to study the influence of the confinement effect provided by transversal reinforcement on the ductility behavior of RC beams in bending is proposed. A unidimensional FEM mechanical model coupled to the Mazars’ damage model to simulate concrete behavior was adopted to assess ductility curvatures at the ultimate limit state. The confinement effect was incorporated to the numerical model through a calibration process of the damage internal parameters, based on the Least Square Method and an analytical law proposed by Kent and Park (1971). Several numerical analyses were carried out considering different designs of RC beams according to a parametric study varying the neutral axis position, concrete compressive strength and the volumetric transversal reinforcement ratio. The obtained results showed the importance of the amount of transversal reinforcement on the ductility behavior, increasing the ductility factor even for the cases with inappropriate neutral axis position.

摘要 本文提出一种简化数值方法，用以研究横向配筋所提供的约束效应对受弯钢筋混凝土（Reinforced Concrete, RC）梁延性性能的影响。为评估极限状态下的延性曲率，本文采用耦合马扎尔损伤模型以模拟混凝土受力行为的一维有限元（Finite Element Method, FEM）力学模型。基于最小二乘法与肯特-帕克（Kent and Park, 1971）提出的分析法则，通过对损伤内部参数的校准过程，将约束效应纳入该数值模型。本文针对不同设计方案的RC梁开展多组数值分析，通过参数化分析改变中和轴位置、混凝土抗压强度与横向配筋体积率三个变量。所得结果显示，横向配筋用量对梁的延性性能具有显著影响，即使在中和轴位置不合理的工况下，也可提升延性系数。