Anchorages For FRP

C ommercially available fiberbased reinforcement for concrete is made of carbon, aramid, or glass filament fibers impregnated in a resin. Some aramid fiber reinforcement consists of aramid filaments without a resin matrix. For general applications, the most important feature of fiber-based reinforcement is its resistance to corrosion, which makes it ideal for reinforcing concrete exposed to high saline environments. A companion paper by the authors' in this issue reviews the general advantages of fiber-based non-metallic reinforcement compared to steel, and describes the products available commercially. Fiber reinforced plastic (FRP) reinforcement has already been used in more than fifteen pedestrian and roadway bridges in Europe and JapanP They have been used to reinforce ground anchors, masonry walls, railway sleepers, pontoons, barges, rehabilitation projects, and special structures.4•7 They have also been proposed for verylong-span cable-stayed bridges. g Tensile and bond strength ofFRP reinforcement is generally equal to or superior to steel reinforcement. However, when used in prestressed concrete, particularly posttensioned concrete, the main challenge is to enlist an anchorage system that will ensure full development of the FRP reinforcement strength. FRP reinforcement's high ratio of axial tensile strength to lateral compn;ssive strength, approximately 20 to I, introduces serious problems to the various anchorage techniques available and to those under development. The current conventional systems used for steel tendons cannot ensure a reliable anchorage system for FRP tendons and could result in premature failure at the anchorage zone. A well-designed anchorage system attempts to develop uniform contact stresses along the anchored tendon length, avoiding stress singularities either at the entry point or at the end of the anchor. Each type of FRP reinforcement available on the market today has unique characteristics, and, to date, there is no single anchorage scheme that can ensure optimal prestressing load transfer for all of them. Most of the systems developed so far have been grout and wedge-type anchorages, the exception being some non-resin impregnated aramid tendons. Many of the producers are' attempting to supply both grout and wedge-type anchors for their products. One disadvantage of grout-type an(A)