Assessment of externally bounded fibre reinforced polymer strengthening reinforced concrete beams at elevated temperature using finite element modelling

Abstract

Over the years, fibre reinforced polymer (FRP) had been found as one of the structural rehabilitation methods that widely used in infrastructures and buildings to strengthen and retrofit the reinforced concrete (RC) structural elements such as RC beams. However, the mechanical properties of FRP such as strength and stiffness as well as the bonding interface between FRP and concrete will be badly deteriorated when exposed to high temperature. This study is to assess the thermal-structural behaviour of insulated FRP strengthened RC beam exposed to elevated temperature using numerical modelling ABAQUS. The proposed numerical model of 200mm x 300mm RC beam subjected to 2 hours standard fire time-dependent curve (ISO 834) had been validated with the experimental test data carried out by previous study. The validated numerical model then is used in parametric study to investigate the behaviour of fire damaged normal strength concrete (40MPa) and high strength concrete (60MPa)of reinforced concrete beam strengthened with FRP using various fire insulation thickness of 0mm, 12.5mm, 25mm and 40mm respectively. The result of steel characteristic strength reduction factor is compared with analytical using 500?C Isotherm methods. The parametric studies indicated that the fire insulation layer is essential to provide fire protection to the CFRP strengthened RC beams when exposed to elevated temperature. The insulation layer thickness of 25mm had been found to be the optimum thickness to be used as it is able to meet the criteria in term of temperature distribution, displacement requirement and retention of beam mechanical properties regardless the use of normal or high strength concrete. In conclusion, the numerical model developed using the FE software (ABAQUS) in this study is able to carry out assessment on the thermal-structural behaviour of the insulated CFRP-strengthened RC beams at elevated temperature.