| Summary: | Fibre reinforced polymer (FRP) strengthening materials offer an opportunity to increase existing concrete slab capacities and service lifetimes. Most previous research in this area has focussed on using glass fibre reinforced polymer (GFRP) and carbon fibre reinforced polymer (CFRP), with relatively little on using basalt fibre reinforced polymer (BFRP) as a strengthening material. Previous research has also tended to focus on strengthening simply supported elements and has not considered the beneficial influence of the in-plane lateral restraint imparted from the reinforced concrete building frame. Furthermore, by installing FRPs using the near surface mounted (NSM) technique, disturbance to the existing structure can be minimised. This research considered both the beneficial effects of compressive arching action (CMA) and FRP strengthening on test slabs constructed from normal strength concrete with span-to-depth ratios of 20 and 15 and 0.15% steel reinforcement. 0.10% BFRP and CFRP was used in strengthened slabs, which were compared with unstrengthened control samples. The bond strength of BFRP and CFRP bars was also investigated over a range of bond lengths with two adhesive thicknesses using an articulated beam arrangement in order to establish optimum bond characteristics. Finally, nonlinear finite element analysis (NLFEA) slab models were developed and validated against experimental test results. The research showed that CMA effects occurred in all in-plane restrained slabs, including those strengthened with FRP bars, and that increases in capacity due to arching and FRP strengthening were cumulative but generally separate in nature. Relationships were also established to allow practicing engineers to estimate in-plane restraint stiffness. Comparisons were also made between slab capacity predictions obtained using the Queen’s University of Belfast (QUB) Arching Theory, NLFEA modelling and current design code approaches. These showed that QUB Arching Theory and NLFEA methods were reliable and that current code methods are highly conservative in comparison with other approaches.
|
|---|
