Three-Parameter Kinematic Approach for Shear Behaviour of Short Coupling Beams with Conventional Reinforcement

This paper presents a three-parameter kinematic theory (3PKT) for predicting the shear strength and deformation patterns of short coupling beams. The 3PKT approach is situated between simple and conservative strut-and-tie models and complex non-linear finite element (FE) models. It is aimed at improving the shear strength predictions of strut-and-tie models while maintaining relative simplicity and clear physical basis. In addition, it is aimed at providing estimates of the ultimate deformations in coupling beams which are typically calculated with FE models. While FE models use a large number of degrees of freedom (DOFs) to describe the deformation patterns in coupling beams, the 3PKT is based on a kinematic model with only three DOFs. In addition to kinematic conditions, the 3PKT also includes equilibrium equations and constitutive relationships for the mechanisms of shear resistance in short coupling beams. The paper presents the formulation of the 3PKT and compares its shear strength predictions to results from tests, finite element simulations, and strut-and-tie models. It is shown that the 3PKT approximates very well the predictions of the FE models, while the strut-and-tie model produce significantly lower strengths.