Behavior of RC beams patch repaired and strengthened with FRP composites: a numerical study.

Abstract

Reinforced concrete (RC) beams get deteriorated and become deficient mainly due to corrosion of steel reinforcements, poor maintenance and design, earthquakes and aging. Patch repair and structural strengthening using fiber reinforced polymers (FRP) have been increasingly adopted all over the world as an economical solution to upgrade the load carrying capacity of such beams. However, the failure modes of such repaired and strengthened RC beams are governed by brittle and sudden premature debonding which involves separation of external reinforcement; i.e. FRP and RC beam. Different researchers have used different approaches including experimental, analytical and numerical to investigate the behavior of patch repaired and FRP strengthened RC beams. It is noteworthy that there are no such numerical studies that investigated the effect of patch repair. In this study, a numerical investigation was carried out using the commercial finite elements analysis software ABAQUS with the aim of investigating the overall behavior of RC beams patch repaired and strengthened with FRP plates including the failure mechanisms. One control RC beam and four patch repaired and FRP strengthened RC beams with varying degrees of damage were investigated. In this respect, the length of the patch material was 450, 800, 1300 and 1800mm. All beams were rectangular in cross section. Furthermore, corrosion was simulated by reducing tensile steel cross section by 10% over the length of the patch. To describe the behavior of such RC beams, different material models were used. Concrete damaged plasticity model was used for both concrete and repair material; a linear elastic perfectly plastic model was used for both longitudinal and transversal reinforcing steel while a linear elastic isotropic model was used for FRP material. The interface between concrete and FRP was modeled using a cohesive bond model. Results from numerical investigations show that the proposed FE model is able to describe the overall behavior of reinforced concrete beams patch repaired and strengthened with FRP in terms of crack pattern, load deflection curves, yielding of steel and failure mechanisms as compared to experimental findings obtained from the same specimens. The mode of failure was intermediate crack induced debonding that was initiated at critical cracks under the loading points and propagated towards the plate ends. In addition to that, increasing the patch length increased the energy required for overall damage. iii Generally, results show that numerical approach can be used to investigate deeply the behavior of RC beams patch repaired and strengthened with FRP strips. It was also observed that the approach is able to capture parameters such as damage energy and strain distribution in FRP, which are not easily captured experimentally or analytically.