Finite element simulation of reinforced concrete beams externally strengthened with short-length CFRP plates

Abstract

Fiber Reinforced Polymer (FRP) materials have been recently used as novel materials to retrofit aging and deficient structures. Several research programs have succeeded in narrowing down the knowledge gap of the debonding mechanism associated with the failure of externally bonded FRP systems. This study seeks numerical investigation of plate debonding and performance of reinforced concrete (RC) beams externally strengthened with bonded Carbon Fiber Reinforced Polymers (CFRPs) plates running for a length covering 25% of the shear span. The results are compared with plates covering 85% of the shear span in addition to a control unstrengthened specimen. The aim of this paper is to develop 3D finite element (FE) models that can accurately simulate the response and performance of RC beams externally strengthened with short-length CFRP plates. A total of six beams were modeled and the load–midspan deflection results and failure modes were compared with experimentally measured data published in the literature. Two out of the five strengthened beams were bonded to the soffit of the beams without any means of end anchorages. The other three beams were strengthened with CFRP plates and anchored transversely at the plate’s ends with different arrangements of CFRP U-wrap sheets. The developed models incorporate the different material nonlinear constitutive laws including the bond-slip action between steel rebars and surrounding concrete and debonding at the CFRP–concrete interface. The predicted and measured load–midspan deflection response results in addition to the failure modes are compared. It was observed that the predicted FE results are in good agreement with the experimental measured test data. A parametric study was then performed using the validated FE model to investigate the effect of the flexural reinforcement bar diameter as well as arrangements of the CFRP U-wraps. It has been concluded that the developed FE models are capable of accurately predicting and capturing capacity the debonding failure mode of RC beams strengthened with FRP plates.