Flexural behaviour of two-way spanning reinforced concrete slabs strengthened using CFRP

Abstract

The continuous deterioration of materials, such as reinforced concrete has created a significant drive for repairing and strengthening existing concrete structures. While Carbon Fibre Reinforced Polymers (CFRP) prove to be advantageous and very practical over many other traditional methods, premature de-bonding of the strengthening material is a main concern related to such a repair system. Such a drawback is important to consider carefully and overcome, especially if the aim of the CFRP intervention is to achieve a stronger and more efficient structural system. This research study is mainly concerned with the experimental and analytical exploration of two-way spanning simply-supported concrete slabs loaded laterally and strengthened on the tension (bottom) side with two types of externally-bonded CFRP reinforcement products by means of structural adhesive. A total of eight 1800mmx1800mmx75mm two-way reinforced precast concrete slabs were fabricated for this purpose. However, due to time constraints, only four slab specimens were eventually tested in this research study. One slab specimen was tested as a reference control specimen without any CFRP strengthening system, the second and third slab specimens were strengthened with CFRP strips having different geometric plan configurations, whilst the fourth slab specimen was strengthened using a CFRP fabric placed centrally. All types of CFRP strengthening were attached to the concrete substrate at the underside of the slab specimens using epoxy-based structural adhesive. Slab specimens were tested under four edge simply supported conditions. The behaviour of the CFRP strengthened slabs are investigated and compared with respect to the reference control specimen. The load-deflection curves, load–strain curves as well as the failure modes and crack patterns for all slab specimens is discussed and reported. Graphical representations of the experimental results are presented in the results section. A section analysis was developed and carried out in order to estimate the ultimate load carrying capacity for each slab specimen, and the results acquired from the analytical method were found to give a good agreement with the experimental findings. The analytical model developed as well as the experimental values were later compared to previous research literature models as well as with predictions from software program developed by Sika, the manufacturers of the CFRP wrap fabric and strips. Conclusions are made and recommendations for future research work are proposed in the final chapter of this dissertation.