Flexural behaviour of two-way spanning reinforced concrete slabs strengthened using externally-bonded steel reinforcement

Abstract

Reinforced concrete elements may need to be strengthened during their life span. This might be because of a number of reasons, such as due to a change of use which involves additional loads or due to the need for repair because of some form of deterioration. Several methods exist, which are capable of strengthening reinforced concrete elements, such as Concrete Jacketing, Concrete Replacement, Externally Bonded CFRP/GFRP Reinforcement, Externally- Bonded Steel Plates and Externally-Bonded Steel Mesh Fabric Reinforcement. The primary objective of this research study is to consider the use of externally-bonded steel plates and externally-bonded steel mesh fabric reinforcement in order to strengthen existing reinforced concrete slabs. The advantage of such an approach is the relative ease of installation of the externally-bonded steel reinforcement to the underside of the slab and also the possibility of building up a new cover by means of rendering over the steel reinforcement. A total of four tests were carried out involving two different configurations of externally bonded steel flat bar reinforcement as well as two configurations of square steel round bar reinforcement attached to the underside of two-way spanning reinforced concrete slab specimens. The external steel grids were fixed to the overlying concrete by means of mechanical Rawl Bolts, this study therefore being a conventional method of repair. All of the specimens were tested under simply supported conditions using the four point bending load method. A section analysis was carried out in order to predict the ultimate failure load of all the slab specimens. Eventually, the results were compared using both graphical and analytical means of analysis in order to establish which system had performed best and is therefore worthy of further studies. These slab specimens are nominally identical to slab specimens that were cast by Ciantar (2021), reinforced with CFRP (Carbon Fibre Reinforced Polymer) Strips and CFRP Wrap and tested to failure. In this manner, it was possible to compare the slab flexural strengths with the results obtained in 2021 of the CFRP-reinforced slabs, as well as the control slab which did not include any additional external reinforcement. Lastly, this study presents a number of conclusions as well as some recommendations for future work, presented in the last part of the final chapter.