STRUCTURAL APPLICATIONS OF COMPOSITES IN INFRASTRUCTURE
also being used in combination with concrete slabs to develop and test new model bridges by M. Saiidi and F. Gordaninejad at University of Nevada, Reno. Since the 1930's, glass fiber reinforced plastic (GFRP) has been considered a good substitute for steel as a reinforcement ofconcrete or to create an initial state ofcompressive stress in concrete by prestressing GFRP tendons~ Reinfofcement and prestressing of concrete are common ways to miti.gate the lo\v tensile strength of concrete in order to take advantage of its high compressive strength~ In fact, reinforced concrete is a fiber reinforced composite material in '''hieh the advantageous properties of the constituents are high tensile strength of the rebars (steel or FRP) and the high compressive strength of the concrete matrix.. Surface protection of certain types of continuous glass fibers, particularly E..glass fibers, from attacks by the environment or alkaline reaction with concrete has been accomplished by coatings, including resins. For example, a typical continuous E..glass fiber reinforced plastic rebar has a 55% glass vol.ume fraction enlbedded in a matrix ofv'inylester or isophthalic resin~ These thermoset resin systems have ex~ ceHent resistance to corrosion a.nd impact, are good electrical and thermal insulators, are easy to manufacture, and are cost effective~ Thermoplastic rebars, which are more expensive than thermosets, have a potential for reshaping and \velding in the field which motivates current investigation oftheir potential applications in constnlction# Aramid fibers (e.g#, DuPont's Kevlar® 29, 49, 149) with higher tensile strength (3~62 GPa) and stiffness (124 G·:Pa for Kevlar@ 49) than glass fibers are being used to devel.op high strength rebars and cables by DoS. and Japanese manufac~ turerso AraIuid fibers have good chemical resistance to sol .. vents, dilute ac...i.ds~ and bases, as well a..1O) excellent fatigue strength and low relaxationo Carbon fiber reinforced plastic rebars and seven wire strands (cables) \vith higher stiffness than glass or aramid fiber rehars are also manufactured as reinforcing or prestressing eleluents for structural appHca~ tions, Ho\vever, carbon fiber rebars and cables are even more expensive than aramid or glass rebars, Chopped fiber rein-· forced plastic rods are being manufactured by extrusion~ 'fhesr.
Bending and bond behavior and design of concrete beams reinforced with fiber-reinforced plastic rebars
The use of non-corrosive fiber reinforced plastic (FRP) rebars in lieu of mild steel rods is investigated. The present work cover experimental testing of twenty seven concrete beams reinforced with FRP rebars subjected to bending , twenty four cantilever specimens subjected to bond forces, and twelve straight pull-out specimens. The following response of concrete beams reinforced with FRP rebars were investigated: preand post-cracking behavior, load-deflection and stress variations, elastic and ultimate load carrying capacities, crack widths and patterns, bond stress and embedment length, and modes of failure. In order to take advantage of the high tensile strength of FRP rebars (80 to 130 ksi), high strength (610 ksi) concrete in lieu of regular strength concrete ( 4 ksi) is used. The use of sand coated FRP rebars in addition to high strength concretes improved the overall behavior of the beams. It is shown that a 90% increase in ultimate moment capacity is achieved over beams reinforced with steel rebars for the same area and strength of concrete. Theoretical correlations with experimental results are conducted in terms of elastic and ultimate bending moment, crack width, post cracking deflection, and bond and development length. Simple design equations for structural design applications are developed with similarities and parallels to current ACI 318-89 code equations. A step by step design example is presented based on the above design equations.
Fiber Composite Bar for Reinforced Concrete Construction
Behavior of concrete beams reinforced with Glass-Fiber-Reinforced-Plastic (GFRP) bars was experimentally investigated. Two types of reinforcements were considered; longitudinal or flexural reinforcement and transverse or shear reinforcement. For each of the two types of reinforcements, three concrete beams were tested to failure. The behavior of each beam was characterized by its load-deflection response to failure. The study was mainly focused on experimentally determining the feasibility of GFRP bars as reinforcement for concrete structures. The results indicated that the plastic bars performed reasonably well in the beams tested.