Confinement Characteristics of GFRP-RC Circular Columns under Simulated Earthquake Loading: A Numerical Study

The seismic behavior of fiber-reinforced polymer-reinforced concrete (FRP-RC) columns is far from being fully explored. Therefore, numerical and analytical studies were performed to address the effects of different parameters and evaluate the current design provisions for confinement reinforcement under seismic loading. Using a commercially available software package, a three-dimensional nonlinear finite-element model (FEM) was constructed and validated against the experimental results of full-scale glass FRP (GFRP)-RC circular columns previously tested by the authors. The validated FEM was, then, used to conduct an extensive parametric study investigating the effect of concrete compressive strength, spiral pitch, axial load level, and column aspect ratio (i.e., shear span-to-depth ratio). It was found that increasing the concrete strength caused an increase in lateral load capacity and initial stiffness, whereas the drift capacity decreased. The latter property was also significantly affected by the variation of spiral pitch and axial load level. On the other hand, the aspect ratio had a marginal effect on moment or drift capacities. Using the results of the FEMs, two new design models were proposed. The proposed models showed remarkably better predictions than the equation adopted by the Canadian standard for the design of FRP-RC structures.