Ductility and Shear Strength Enhancement by Fiber Sheet with Large Fracturing Strain

Recently the authors have developed a jacketing method with fiber sheet whose fracturing strain is higher and stiffness is lower than those of commonly used fiber; carbon aramid and glass. The fiber is Polyethylene Terephthalate (PET) and Polyethylene Naphthalate (PEN). In this paper results of series of experiments on ductility and shear strength enhancement are presented. Fifteen specimens, which are a model of typical bridge pier, with PET and PEN sheet jacketing were tested under reversed cyclic loading until the ultimate ductility was attained. The stiffness of PET and PEN sheet is smaller than that of carbon sheet to achieve a similar ultimate ductility. For investigating the shear strength enhancement two specimens were tested and showed higher shear strength and more ductile manner than a companion specimen with carbon fiber sheet. A good control of shear deformation by the un-fractured sheet is a primary reason to enhance the ductility and shear strength. Ductility and shear strength enhancement cannot be predicted by existing formula derived from test results with carbon and aramid fiber. Because of those good features together with less cost, the jacketing with PET and PEN sheet is adapted as a seismic retrofitting method for railway structures in Japan.