Behaviour of gfrp retrofitted rectangular rc beams with small web openings under torsion: experimental study

Abstract

Provision of utility and service ducts are important part of modern building construction. To facilitate fast and uninterrupted progress the layout of these ducts are planned in advance. Their positions are decided considering the head room provisions in buildings, aesthetic look etc. without jeopardizing the strength,stability and serviceability of the structures. To fulfil these aspects many times ducts have to pass through main load bearing elements like beams. Web openings in a beam adversely affect its strength and stiffness resulting in excessive deflections which may lead to unpleasant appearance and the collapse of the structure. Therefore, such beams are required to strengthen to restore their strength. The newly developed technique of jacketing the deficit beam with layers of Fiber Reinforced Polymer has proven to be very efficient in restoring and increasing the strength of the beams. Since 1980 extensive research has been carried out on beams with rectangular and circular openings under the most commonly encountered loading case of shear and flexure. The behavior of beams with openings under torsion and its combination with shear and flexure has not been explored much. Hence the aim of the present work is to explore the behavior of rectangular RCC beams with small circular and rectangular openings under torsion. The torsional capacity of beams with openings are extracted experimentally .The study is extended by retrofitting the beams with four layers of bidirectional woven GFRP fabric applied following three different orientations scheme 90/90/90/90 ,45/45/45/45 and 90/45/90/45. The restoring torsion capacity, crack patterns are observed.