Seismic Response Evaluation of Reinforced High Strength Concrete Columns based on the Modified Constitutive Model

Current study deals with strength and seismic ductility assessment of reinforced high strength concrete (HSC) columns. We have studied the nonlinear response of HSC columns with various reinforcement and axial force ratios subjected to cyclic loading. Study consists of primary verification of mathematical nonlinear model and further calibration to ensure accuracy. An existing experimental work is assumed as verification pilot that consists of four columns. Column members differ in the strength and axial force. Concrete has 63.1 MPa mean strength and 0.3% crushing strain. The longitudinal and transverse reinforcements are according to ACI 318 regulations in experiment. We used the nonlinear fiber-element code in OpenSees environment for modeling and analysis of models. The existing proposed stress-strain curve is modified to ensure validity of assessment. Calibration procedure led to conclusion that the post-yield slope needs to be modified in HSC model as the average value of ACI 363 reference. We have developed twelve extra models to estimate the interaction of concrete strength, rebar ratio and the axial force effect on the seismic performance. Parametric study of calibrated models reveals that the seismic energy dissipation in HSC members is function of the provided longitudinal reinforcement ratio and lateral confining stirrup amount.