Abstract
Many reinforced concrete (RC) members, such as bridge slabs, are periodically subjected to repeated loads and therefore require strengthening to extend their service life. The near-surface mounted (NSM) technique has recently emerged as one of the most effective methods for flexural strengthening. This study investigates the fatigue behaviour and flexural load-carrying capacity of one-way RC slabs strengthened with NSM steel, CFRP, GFRP, and BFRP bars. A total of ten slabs were tested: five under static loading and five under cyclic loading. The fatigue group was subjected to one million cycles at 50% of the ultimate static load of their respective controls, followed by static loading to failure. Performance parameters examined included crack development, failure modes, ultimate load, mid-span deflection, residual strength, ductility, energy absorption, and deformability. The results demonstrated that NSM strengthening significantly improved slab performance. The slabs were strengthened using carbon fibre-reinforced polymer (CFRP), glass fibre-reinforced polymer (GFRP), basalt fibre-reinforced polymer (BFRP), and steel bars, designated as FCR, FGR, FBR, and SR, respectively. The maximum load-carrying capacities increased by 122.5%, 49.1%, 61.35%, and 21.77%, respectively, compared to their corresponding control slabs. Residual bearing capacity also improved, with CFRP- and BFRP-strengthened slabs (FCR and FBR) achieving 11.26% and 8.17% gains over their static counterparts. These findings confirm the effectiveness of the NSM technique in enhancing fatigue resistance and post-fatigue serviceability of RC slabs, with CFRP bars providing the greatest strength improvement among FRP options, while steel bars offered a balanced combination of strength and ductility.