A new FEM approach for FRP-strengthened RC frames

Owing special mechanical properties has made Fiber Reinforced Polymer (FRP) as one of the best strengthening materials for Reinforced Concrete (RC) structures. The effect of externally applied FRP sheets on RC elements has been the topic of many experimental investigations. On the other hand, simulating the behavior of RC structures strengthened by means of externally bonded FRP sheets is yet to be scrutinized. In this work, a new Finite Element (FE) procedure for inelastic analysis of RC structures has been enriched to account the presence of externally bonded FRP sheets on RC sections. The proposed FE procedure works in the framework of lumped plasticity. It is able to identify the exact location of plastic hinges and imposes rotational discontinuities in the position of plastic hinges. The yield domain of the FRP-strengthened sections is constructed based on the hypothesis of strain linearity and taking into account the debonding failure between FRP sheet and concrete substrate. Numerical applications are presented for unstrengthened and strengthened RC frames. Pushover analysis has been carried out on numerical applications and the results are compared to each other. In order to verify the results of the numerical applications, the same models are built and analyzed in OpenSees, which proves the integrity of the FE procedure and its applicability for FRPstrengthened RC frames.