Flexural behaviour of hollow reinforced concrete T-beams strengthened or retrofitted with carbon-fibre-reinforced laminates: Experimental and numerical investigation

Abstract

This study investigates the effect of longitudinal rectangular openings on the flexural behaviour of reinforced concrete (RC) T-beams strengthened or retrofitted with external carbon-fibre-reinforced polymer (CFRP) laminates. Eight RC T-beams, with one solid and one hollow beam in each of four groups, were analysed using a three-point bending test. The CFRP laminate used in each beam was similar, and the beams had an identical longitudinal reinforcement ratio. The ultimate load capacity of the strengthened hollow RC T-beams showed a 9% decrease compared to that of the strengthened solid RC T-beams, while retrofitted hollow RC T-beams with 100% preloading exhibited a 24% decrease in ultimate load capacity compared to that of retrofitted solid RC T-beams. In addition, the CFRP laminate had a positive effect on reducing strain in hollow RC T-beams as compared to that of solid RC T-beams. The flexural behaviour of the CFRP-strengthened hollow RC T-beams with a 5% cross-sectional hollow core area was similar to that of strengthened solid RC T-beams. However, after preloading, the retrofitted hollow RC T-beams exhibited a decrease in flexural efficiency compared to the retrofitted solid beams. A validated numerical model was developed using ABAQUS to accurately simulate the behaviour of the hollow RC T-beams. Subsequently, a parametric study was conducted using the validated model to investigate the effects of varying the position and size of the hollow section on the response of the RC T-beams.