A Study on Design Method for strengthening of Existing Concrete Structures using Advanced Reinforcing Materials

This study is carried out to develop the design method for strengthening of exsisting concretestructures using FRP sheets and FRP tendons. Results in this study are summarized on the followingthree points(1)Long term properties of reinforcing materials2 . Ultimate capacity and deformation of concrete members retrofitted with FRP sheet，(3)Ultimate capacity and deformation of concrete structures retrofitted with FRP tendons.(1)Long-term Properties of Reinforcing Materials The relaxation ratio represents The naturalcharacteristics of每个FRP tendon and varies in proportion to the logarithm of time throughout theentire loading time range. The tensile strength and bond strength of FRP sheet not reduced evenafter FRP sheet is soaked in 10% sulfuric acid solution for six months.(2) Ultimate Capacity ofDeformation of Concrete Members Retrofitted with FRP Sheets .它是如何Concrete strength，刺激FRP sheets affect the bond mechanism of FRP sheet. the bond strength equation wasproposed. FRP sheet which is attached to a lower face in a beam as flexuralreinforcement not occur，bending capacity and deformation of the beam can be predicted by the layr-by-layr procedure. Forfailure mode with peeling of FRP sheet along a shear crack，the model of predicting the shear reinforcing effect of FRP sheet was proposed.(3) Ultimate Capacityand Deformation of Concrete Structures Retrofitted with FRP Tendons The flexural behavior ofexternally prestressed beams can be estimated by a precise calculation method considering thecompatibility of deformations and changes in location of cables. FRP ultimate strengthtendons at deviators becomes less then the uniaxial tensile strength. the rate of reduction differsfor different type of FRP tendons. When a cable tensile force was within the range of 40 to 50% ofthe nominal breaking load for AF rope, failure did not occur during the the 2,000,000-cycle loading。

This study is carried out to develop the design method for strengthening of exsisting concrete structures using FRP sheets and FRP tendons. Results in this study are summarized on the following three points ; (1)Long term properties of reinforcing materials, (2)Ultimate capacity and deformation of concrete members retrofitted with FRP sheet, (3)Ultimate capacity and deformation of concrete structures retrofitted with FRP tendons.(1) Long-term Properties of Reinforcing Materials・The relaxation ratio represents the natural characteristics of each FRP tendon and varies in proportion to the logarithm of time throughout the entire loading time range.・The tensile strength and bond strength of FRP sheet were not reduced even after FRP sheet is soaked in 10% sulfuric acid solution for six months.(2) Ultimate Capacity of Deformation of Concrete Members Retrofitted with FRP Sheets・It was clarified how concrete strength, and stiffness of FRP sheets affect the bond mechanism of FRP sheet. The bond strength equation was proposed.・When peeling of FRP sheet which is attached to a lower face in a beam as flexural reinforcement does not occur, the bending capacity and deformation of the beam can be predicted by the layr-by-layr procedure.・For failure mode with peeling of FRP sheet along a shear crack, the model of predicting the shear reinforcing effect of FRP sheet was proposed.(3) Ultimate Capacity and Deformation of Concrete Structures Retrofitted with FRP Tendons・The flexural behavior of externally prestressed beams can be estimated by a precise calculation method considering the compatibility of deformations and changes in location of cables.・The ultimate strength of FRP tendons at deviators becomes less then the uniaxial tensile strength. The rate of reduction differs for different type of FRP tendons.・When a cable tensile force was within the range of 40 to 50% of the nominal breaking load for AF rope, failure did not occur during the the 2,000,000-cycle loading.