Strengthening of Shear Deficient Reinforced Concrete L-Beams Using Glass Fibre Reinforced Polymer Composites

Abstract

Many of the existing reinforced concrete structures throughout the world undergoes deterioration due to many factors like corrosion, lack of detailing, increase in service loads which leads to cracking, loss of strength and stiffness due to ageing, excess deflections and improvement in design guidelines etc., necessitates the urgent need of rehabilitation. The rehabilitation which can be in the form of strengthening, repair or retrofitting. Reconstruction of the structures which requires more amount of cost, labour and takes more time, so rehabilitation is the better way of improving the structurally deficient existing RC structures. Fibre reinforced polymer composites are considered as smart and auspicious material for rehabilitation of existing reinforced concrete structures. Reinforced concrete L-beams which are found in buildings and bridges may fail either in flexure, shear, torsion or combination of any of them. Shear failure of RC L-beam is the most catastrophic failure as it does not give any prior warning before failure. Shear Strengthening of existing reinforced concrete L-beams using externally bonded fibre reinforced polymers has become a popular structural strengthening technique due to familiar benefits of FRP composites such as high strength to weight ratio and excellent corrosion and fatigue resistance and excellent durability.

The present research work assimilates the experimental and numerical investigation of structurally deficient reinforced concrete L-beams strengthened with Glass fibre reinforced polymer composites.

In the experimental study, a total of thirteen beams were tested under symmetrical four point static loading system. All the beams were tested in two series by varying shear span to effective depth ratio. In each series one beam was considered as control beam while other beams were strengthened with GFRP sheets/strips in different configurations and orientations. The various parameters were investigated such as amount and distribution of GFRP sheets, bonded surface number of layers of GFRP sheets/strips, fibre orientation and end anchorage. The experimental results shown that control beam failed in shear whereas failure of strengthened beams were initiated by debonding failure of GFRP sheets/strips followed by brittle shear failure. However, there was a better enhancement in the shear capacity of strengthened beams over control beams. An innovative method of new mechanical anchorage scheme comprised of steel plates with nut & bolt system was used for the prevention of debonding failure of GFRP sheets, as a result full strength of GFRP sheets gets utilized. A numerical investigation has also been carried out in ANSYS to validate the experimental findings.