Shear Behaviour of BFRP Strengthened RC T-Beams

Abstract

Deterioration in reinforced concrete structures is a major issue faced by the infrastructures and bridge industries all over the world. Since complete replacement of these structures requires high investment, strengthening has become the suitable solution to modify and improve the performance of the structures. Previously steel plates were used as external reinforcement to strengthen deficient RC structures, but in the last fifteen years or so on, FRP composites have been used to replace steel because of their superior properties. RC T-section is the most common shape of beams and girders in buildings and bridges. Shear failure of RC T-beams is identified as the most disastrous failure mode as it does not give any advance warning before failure. The shear strengthening of RC T-beams using externally bonded (EB) FRP composites has become a popular structural strengthening technique, due to the well-known advantages of FRP composites such as their high strength-to-weight ratio and excellent corrosion resistance. This study explores the result of an experimental investigation for enhancing the shear capacity of reinforced concrete (RC) T-beams with shear deficiencies, strengthened with Basalt
Fiber Reinforced Polymer (BFRP) sheets which are a relatively new and economic alternative to more expensive fibers commonly used in strengthening of RC beams. A total of 22 numbers of concrete T-beams are tested and various sheet configurations and layouts are studied to
determine their effects on the shear capacity of the beams. One beam of the beams is considered as control beam, while other beams are strengthened with externally bonded BFRP sheets/strips.
To accommodate essential services like electricity cables, natural gas pipes, water and drainage
pipes, air-conditioning, telephone lines, and computer network transverse web opening are necessary in modern building construction. Hence, the present study investigates the shear behaviour of RC T-beams with different types of transverse web openings. The various
parameters investigated in this study included BFRP amount and distribution, bonded surface, number of layers of BFRP, fiber orientation, transverse web openings of different shape (i.e., circular versus square versus rectangular) and end anchor. The experimental results demonstrated that the use of the new mechanical anchorage scheme comprising of laminated composite plates increases the shear capacity of the beams significantly by preventing the debonding of BFRP sheets, so that the full strength of the BFRP sheets get utilized. An analytical study is also carried out to validate the experimental findings.