Flexural Behavior of Hollow-Core Slabs Strengthened with Prestressed Basalt FRP Grids

Abstract

Numerous studies have been conducted on strengthening techniques using prestressed fiber-reinforced polymer (FRP) laminates, bars, and tendons. However, to date, no technique has been developed for prestressed FRP grids, which are an attractive solution for strengthening slabs, walls, and tunnels. In this paper, a novel waveform anchor is proposed and verified by tensile tests to be capable of feasibly and effectively anchoring the basalt FRP (BFRP) grid. Five hollow-core slabs, including one control slab and four strengthened slabs, were tested to failure to investigate the flexural behavior of slabs strengthened with prestressed BFRP grids. The effect of the anchorage system and prestressing force on the flexural performance of the slabs was studied. The test results showed that the failure mode of the prestressed BFRP grid–strengthened slabs was rupture of the BFRP grids, and no end peeling was observed. At increasing prestressing force in the BFRP grid, the failure mode changed from sequential rupture to essentially simultaneous rupture of the longitudinal bars. Thus, the flexural capacity of the strengthened slabs increased with the prestressing level of the BFRP grids. Improved cracking behavior of the slab could be obtained by prestressing the BFRP grid, and the crack width remarkably decreased as the prestressing force in the BFRP grid increased. However, the ductility of the strengthened slabs decreased with increased prestressing force in the BFRP grid.