Comparative analysis of flexural performance of old full-scale hollow slab beams reinforced with fiber composites

•TRC and TRECC have good mechanical and durability properties.•The flexural performance of old full-scale hollow slab beams is explored.•A quantitative reinforcement comparison is made between TRC, TRECC and CFRP plates.•The effect of the axial stiffness and local stress distribution of the beam was evaluated. To address the problems of inadequate load carrying capacity, deformation and deflection of the main beams of in-service reinforced concrete (RC) bridges, the flexural performance of old full-scale hollow slab beams was investigated based on four-point bending tests in the field, and a qualitative and quantitative comparison was made between innovative solutions (TRC, TRECC) and conventional solutions (prestressed CFRP plates). The results show that the three fibre composite reinforcements increase the load carrying capacity of the hollow slab beams by 9.09% to 21.2% and the stiffiness by 0.4% to 46%, and that the deflection is effectively controlled and limits the development of cracks, while the ductility is reduced. The prestressed CFRP plates are more beneficial in delaying the stiffness degradation under service loads, and the deflection values of their reinforced beams are smaller; while TRECC shows better performance in controlling the crack width. On this basis, the effect of the axial stiffness of the reinforcement on the overall performance and local stress distribution of the beam was evaluated by load calculation and numerical simulations, and showed good agreement between the experimental and theoretical results. The effect of external reinforcement on the beam depends more on the axial stiffness than on the nature of the reinforcement material, and the effect of external reinforcement on the tensile side of the beam is mainly concentrated on the plastic phase.