Experimental Investigation On Flexural and Shear Behaviour Of Reinforced Concrete Beams Using GFRP Reinforcement

Abstract

New types of materials are always a matter of research interest. Researchers have attempted improvement different properties of structural members by using different types of innovative materials and techniques. Improvement in flexural, shear properties and durability for beams is one of the important aspects related to overall behaviour for structures. FRP is a material which withstands higher tensile strength as well as having other advantages like non-corroded and nonmagnetic. FRP reinforcement is one of the most innovative solutions to replace a conventional steel reinforcement partially or fully. Hence, an attempt has been made hereby to check comparative performance of RC beams using various combinations of conventional and FRP rebars. FRP rebars have been used as tensile and shear reinforcement for beams. Replacement of conventional reinforcement of HYSD rebars has been tried with FRP rebars for RC beams in the present investigation. Total twelve beams having cross sectional dimensions 150mm x 200mm with effective span of 2.1 m are cast in experimental programme. Variations has been employed in study by changing main reinforcement for RC beams. Total six categories of beams have been divided assuming two beams as identical in each category to take an average results. First three category of beams consist main reinforcement as HYSD rebars, combined HYSD and GFRP rebars, and third category has been consists of GFRP rebars only. All beams in first three categories have been used mild steel stirrups respectively. Another three categories of beams have same main reinforcement GFRP stirrups have been used. Different parameters like moment capacity, failure load, crack pattern, strain and deflection have been measured experimentally for all beams. Design for RC beams has been done and relevant checks have been made. Different codal provisions have been used for design of beams using IS 456:2000 and ACI 440.1R-03 respectively. Moment capacities for different beams have been computed. It has been observed that failure load obtained for RC beams with minimum FRP reinforcement can give comparable results for beams with higher amount of HYSD reinforcement. IV Tensile testing of GFRP as well as HYSD bars have been conducted under universal testing machine. Here GFRP bars show good amount of strength compared to HYSD bars. Testing of beams have been conducted using two point load. Comparable failure loads and moment capacity has been observed for RC beams with FRP rebars and conventional HYSD rebars. RC beam with combined rebars have performed better compared to all other beams in terms of load and moment capacity. GFRP stirrups have exhibited superior performance compared to mild-steel stirrups in failure loads and moment capacities for all RC beams. As per theoretical as well as experimental evaluation, shear strength of RC beams with conventional reinforcement proves better compared to RC beams with GFRP reinforcement. Experimental shear strength higher of RC beams with combined reinforcement has been observed higher compared to all other beam specimens. Higher magnitude of deflection and strain has been observed for RC beams with GFRP rebars compared to RC beams with conventional rebars. RC beams with GFRP stirrups have exhibited lower deflections compared to RC beams with mildsteel stirrups. GFRP rebars have ruptured suddenly, compared to conventional HYSD bars. FRP stirrups also have been failed suddenly with loud noise compared to mild steel stirrups. Thus, it can be concluded that GFRP rebars have proved better material to replace conventional HYSD bars because of comparable strength and other benefits like light in weight, non-corrosive, non-magnetic etc. Partial replacement of conventional HYSD bars with GFRP rebars has exhibited higher strength and capacity for RC beams. However, more experimental and analytical investigations are required in this area for generalizing use of FRP rebars in Structural Engineering applications.