The Performance Of Pre-Stressed Concrete Beams Reinforced With Fiber-Reinforced Polymer Laminates

Abstract

Strengthening of pre-stressed concrete structures using Fibre Reinforced Polymer (FRP) shows better promise for extending their service life. Knowledge about the actual performance of the strengthened members is an essential prerequisite for an effective application of the technology. The main objective of this research work is to evaluate the static response of pre-stressed concrete beams strengthened with externally bonded Fibre Reinforced Polymer (GFRP) laminates at the soffit of beam. A total of fourteen beams of 3 m length and 150 mm x 250 mm in cross-section were cast and tested in the laboratory. Two unbonded post-tensioned beams served as reference beams and the remaining twelve beams were strengthened with GFRP laminates on their soffit. 7 beams cast with M35 grade concrete were strengthened with three different GFRP laminates having two different thicknesses 3 mm and 5 mm and tested under monotonically increasing loading and manual readings were recorded. Remaining 7 beams cast with M60 grade concrete were strengthened with three different GFRP laminates having two different thicknesses 3 mm and 5 mm and tested under monotonically increasing loading and manual readings were also recorded directly. The variables considered included grade of concrete, type of GFRP laminate and thickness of GFRP laminate. The GFRP laminates also varied in their configuration, viz., Chopped Strand Mat (CSM), Woven Roving (WR) and Uni- Directional Cloth (UDC). Responses of all the beams were evaluated in terms of strength, stiffness, ductility, composite action between concrete and external reinforcement and the associated failure modes for beams tested under static loading. The study parameters considered for this research work included yield load, deflection at yield load, ultimate load, deflection at ultimate load, deflection ductility, deflection ductility ratio, energy ductility, energy ductility ratio, number of cracks and energy absorption.