Secondary flexural behaviour of reinforced concrete beams strengthened with special-shaped rivet bonded steel plates and prestressed CFRP bars

Special-shaped rivet and glued steel plate reinforcement is an innovative structural reinforcement technology. A riveted glued steel plate primarily relies on the rivet to transfer shear. Prestressed carbon fibre-reinforced polymer (CFRP) reinforcement is a new technique for strengthening concrete structures. These studies focus on the 'primary load', overestimate the ultimate flexural load of the components by neglecting the 'secondary load' of the components in real engineering. In this study, the flexural properties of concrete beams strengthened using special-shaped rivet steel plates and CFRP prestressed bars were studied theoretically and experimentally. The cracking load, ultimate load capacity, and strain of the steel plate, steel bar and CFRP bars were recorded during the tests. In addition, the failure mode of the beams was observed, and the effect of secondary stress on the flexural capacity of the beams was analysed. The failure load of the beams strengthened by CFRP prestressed tendons increased by 67.8% and 46.1% for beams with primary and active secondary loads, respectively. The failure load of the special-shaped rivet and glued steel plate strengthened beam increased by 115.7% and 160.5%, for beams with primary and active secondary loads, respectively. Both methods have a strong guiding significance for engineering practice.