Compressive Membrane Action in FRP NSM strengthened slabs

This paper outlines basalt and carbon fibre reinforced polymer (BFRP and CFRP) strengthening of laterally restrained concrete floor slabs. In-plane restraint has previously been shown to enhance slab capacity due to the development of internal compressive membrane action (CMA), which is generally neglected in codified strength assessments. By installing fibre reinforced polymers (FRPs) using the near surface mounted (NSM) technique, disturbance to the existing structure is minimised. The span-to-depth ratios of test slabs were 20 and 15. These were constructed with normal strength concrete (~40N/mm2) with 0.15% steel reinforcement. A tenth of one percent of FRP (either BFRP or CFRP) strengthening material was used to strengthen samples which were later compared with unstrengthened control samples. Investigations showed that FRP strengthening and CMA are generally separate, with limited overlap in terms of their contribution to capacity increase. Recommendations are then made for designers to better determine the capacity of FRP strengthened restrained slabs.