Reinforced Concrete Frame Element with Axial-Shear-Flexural Interaction Under Cyclic Loading

Abstract

This thesis presents the reinforced concrete (RC) frame element for the analysis of the RC columns characterized by light and insufficiently detailed transverse reinforcement. This type of column is defined as the "non-ductile" RC column and also found in the existing RC frame buildings designed and constructed before the introduction of modern seismic codes. The frame element in this study is derived based on the displacement-based formulation and the Timoshenko beam kinematics assumption is used to describe the variation of strains along the RC cross- section at the fiber section level. As a result, the axial-flexure interaction is automatically taken into the element stiffness matrix while shear action uncouples with those actions. The shear-flexure interaction is taken into account via the shear hysteretic curve. The presented shear force and shear strain relation in the shear hysteretic curve is adopted and modified from the research work of Mergos and Kappos (2008 and 2012). The degradation of shear strength due to the influence of inelastic flexural deformations is accounted in this modified shear hysteretic curve within the framework of the so-called " UCSD Shear-Strength Model". Linked displacement interpolation functions are used to solve the problematic phenomenon known as "shear locking" in the Timoshenko frame element. Finally, the importance of including shear response and shear-flexure interaction in the evaluation of the non-ductile RC columns are presented and discussed through the three numerical examples. Furthermore, the numerical examples are employed to verify the model accuracy and its capability to predict rather complex responses of the non-ductile RC columns.