Bi-directional strengthening of two-way spanning reinforced concrete slabs using fibre reinforced polymer composite materials

The use of fibre reinforced polymer (FRP) systems as externally bonded reinforcement has become very popular for the repair and strengthening of reinforced concrete (RC) structures. It is an alternative to the traditional techniques, due to well-known advantages of FRP composites such as high strength- and stiffness-to-weight ratios, corrosion resistance and ease of transportation and installation. In this thesis, experimental and numerical investigations were conducted on estimating the behaviour of two-way spanning reinforced concrete slabs strengthened using FRP composite material. The experimental programme comprises eight medium-scale specimens that are designed and constructed. The first slab is control specimen without strengthening while in each of the other seven slabs different types of strengthening are applied. The specimens were subjected to monotonic static load. The FRP application procedure, different strengthening configuration and loading device are described in detail in this study. Deflections, strains and crack patterns are monitored during the loading process until failure and the structural response of the the strengthened specimens is compared with the control specimen. The experimental results are analysed and the most important conclusions as the result of the investigation are offered. The effectiveness of utilising externally bonded CFRP plates for improving the performance of RC slabs in terms of ultimate load capacity was observed. CFRP additional anchoring can further increase the performance of the strengthening schemes adopted. Furthermore, nonlinear finite element models using ANSYS were created to obtain a further insight into the behaviour of the selected tested specimens. In the finite element analysis, a full bond assumption is made between the concrete and both reinforcing steel bars and the strengthening FRP material. Both experimental and numerical results were compared. Having calibrated finite element results, optimisation study on the effect of distance between CFRP plates is conducted