BEHAVIOUR OF FRP PRISMATIC SECTIONS IN COMPOSITE ACTION WITH CONCRETE N. F. O. Evbuomwan Department of Civil Engineering, University of Newcastle, Newcastle upon Tyne, UK ABSTRACT The use of Fibre Reinforced Plastics (FRP) although an emerging phenomenon in the construction industry, is gradually gaining ground particularly within the research community. This paper presents some of the results obtained in an on-going research program involving the use of FRPs in composite action with concrete. Pultruded Glass Fibre Reinforced (50.82 x 50.82mm) square sections, of 600 and 750mm lengths were used in this research. They were bonded to high strength concrete slabs with the aid of epoxy and/or steel bolts to ensure composite action and then tested in flexure. In general, the composite beams exhibited much higher ultimate failure loads and lower deflections than the plain GFRP beam, particularly for the specimens bonded with epoxy alone. INTRODUCTION The use of FRPs has over the years been mainly restricted to the aerospace and automobile industries. However, within the recent past there has been an increase in the use of FRPs within specialised sectors of the construction industry. For structural engineering applications, particularly in concrete structures, efforts are now being made to explore the potential of using FRPs as an alternative material to steel. This has been necessitated inter-alia by the fact that FRPs do exhibit certain properties that particularly make them attractive to engineers, such as : low weight, high static and fatigue strengths, high tensile strengths, resistance to chemicals and corrosion, high damping capabilities, and so on [1]. Current research activities on the use of FRP with concrete, involves (i) strengthening and rehabilitation of concrete members with CFRP and/or GFRP plates, (ii) the use of FRP rods as reinforcements in concrete beams and (iii) the use of FRP rods as prestressing tendons in concrete beams [2]. Another form of application which has started to generate interest is the use of FRP prismatic sections in composite action with concrete. A number of researchers [3-5] have studied the behaviour of plain prismatic FRP sections, essentially to establish their structural behaviour. Sims et al [3] studied the strength and stiffness (flexural and shear) properties of pultruded glass fibre reinforced plastic box and I beam sections, while Maji et al [4], based on their experimental results concluded that the design principles governing pultruded FRP composites were more critical in stiffness than in strength. Nagaraj and GangaRao [5] also presented experimental and theoretical results based on tests carried out on box and I beams sections. They observed that I sections were stiffer than box sections and that the contribution of shear on deflection was significant in relation to bending deflection. Previous research involving the use of FRP in composite action with concrete placed in the compression zone, has been reported by Deskovic et al who studied both short-term [1] and long-term [6] behaviour, and Saiidi et al [7]. Deskovic et al, who used a combination of both glass fibre and carbon fibre reinforced plastics, found for the short- term behaviour, that there was good agreement between experimental and analytical