Nonlinear Finite Element Modelling of FRP Strengthened RC Beam-column Joints

A research study was conducted at the University of Queensland in order to evaluate the ability of CFRP web-bonded systems in strengthening an exterior beam-column joint subjected to monotonic loads. As part of this study, one 1/2.2 scaled plain and two CFRP retrofitted joints subjected to monotonic loads were tested and analysed using the nonlinear finite-element program ANSYS. A modified version of the Hognestad's model was used to model the concrete compressive strength and the ANSYS model was employed in order to account for tension stiffening in concrete after cracking. In order to model the stress-strain properties of main steel bars a multilinear isotropic hardening model was considered. For FRPs however an anisotropic model was used. Perfect bond between materials was assumed as nodes were shared between adjacent elements irrespective of their type. Good agreement between the numerical predictions and the experimental observation of the failure mechanisms for all specimens was observed. This proved that the numerical analysis could be used as a practical tool for the analysis of web-bonded FRP strengthened beam-column joints.