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Reinforced concrete slabs on steel girder bridges on the Tokyo Metropolitan Expressway are generally strengthened by installing additional stringers or attaching steel plates. However, it is difficult to apply such methods to strengthening work in confined box girders or where there are obstructions. Carbon FRP plates (CFRP) have been selected as strengthening materials for their applicability to strengthening work in confined spaces, and because they can be bonded in lattice forms, allowing for bonding condition inspection on the lower faces of the slabs. The aim of CFRP strengthening is to reduce the reinforcing bar stress caused by excessive wheel loads. In Part 1, investigations are conducted on CFRP applicability to strengthening work through static loading and work efficiency tests. Reinforcing bar tensile stress intensity was reduced by 38 to 56 percent of the unstrengthened specimen. The loads at which the tensile stress intensity is 140 MPa (allowable reinforcing bar load) are around 1.3 times that of an unstrengthened specimen. It can be concluded from the preceding that reinforcing bar stress intensity can be reduced, confirming the possibility of strengthening.

Part 1 of this study concluded that reinforcing bar stress intensity can be reduced, thereby confirming the possibility of strengthening. In Part 2, CFRP is bonded by various methods on the lower faces of reinforced concrete slabs. To determine bonding methods in detail, CFRP is studied with respect to the confirmation test and strengthening design methods. Strengthening design and measurement plans are then made for reinforced concrete slabs on an existing bridge. In strengthening design, the main reinforcing bars are strengthened with three to five layers. It is confirmed that the reinforcing bar tensile stress intensity is reduced around 120 to 130 MPa. CFRP may be used as a strengthening material for reinforced concrete slabs. Measurements will be conducted in 1993. Bending resistance will be confirmed directly during existing bridge strengthening operations.

Recently, a non-metallic reinforcement is developed using new synthetic fiber, such as carbon, aramid and vinylon fiber in Japan. The fiber is made into a FRP rod. This material has advanced properties, for example, corrosion free, light weight and high strength, and are expected to apply for the practical structures. However, it is important to study engineering properties and design method in many fields theoretically and experimentally. In present paper, the bond characteristics are discussed because the expansion coefficient of non metallic fiber is different from conventional concrete. The results from the pull-out tests are, (l)the bond strength of FRP rod is ensured for the concrete structures, and (2)the deterioration of bond property is not appeared in CFRP, GFRP and VFRP however a little reduction is observed at AFRP rod.

Lateral confinement of concrete members by means of spirally wrapping fiber-reinforced-plastic (FRP) composites onto the concrete surface may increase compressive strength and ultimate strain (pseudo-ductility). It may also provide a mechanism for shear resistance, and inhibit longitudinal steel reinforcement buckling. Lateral confinement of concrete members as a strengthening/repair technology is expected to have an impact in the rehabilitation/renovation of buildings and infrastructure. Structures that have been damaged, or need to comply with new code requirements, or are subjected to more severe usage are the primary targets. In this project, an experimental and analytical study of concrete strengthened with FRP lateral confinement I conducted using compression cylinders (300 and 600 mm in length) and l/4 scale column-type specimens. The latter specimens have a circular cross section and given longitudinal/transverse steel reinforcement characteristics. Column-type specimens are subjected to cyclic flexure with and without axial compression. When an aramid FRP tape is used as the lateral reinforcement, the variables are tape area and spiral pitch. In the case of filament winding with glass fiber, the thickness of the FRP shell is varied. The limited experimental results obtained at this stage of the research program indicate that lateral confinement significantly increases compressive strength and pseudoductility under uniaxial compression.

This paper reports on the effects of improvement in flexural characteristics and deformability(ductility) when using unbonded CFRP(Carbon Fiber Reinforced Plastic) tendons in prestressed concrete (PC) beams and bending fatigue characteristics of bonded type PC beams with CFRP tendons. Based on the results of flexural loading experiments, with PC beams using unbonded CFRP tendons, failure modes shifted from CFRP tendons rupture type to concrete crushing type. while deformation at the ultimate stage was also changed greatly for the better. It was also succeeded in ascertaining that effective prestressing force, and tensile reinforcement quantity and variety are influential as factors increasing deformability at the ultimate stage. Further, as the result of bending fatigue tests of bonded type PC beams with CFRP tendons, it was confirmed that reduction in ultimate flexural loads of bonded type PC beams due to repetitive loading was not seen and bending fatigue properties were favorable.