Deformation capacity of RC piers wrapped by new fiber-reinforced polymer with large fracture strain

Abstract

One of the major drawbacks of structure strengthening by fiber reinforced polymer wrapping using materials such as CFRP and AFRP, whose strength and stiffness are high, is the brittle nature of failure mode, which is caused by fracture of the fiber due to low fracturing strain. A series of experiments were conducted to investigate the efficiency of using two new types of fibers, polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) fiber, for seismic strengthening of RC piers. These fibers have the properties of low stiffness and high fracturing strain. Specimens strengthened by PET and PEN fiber sheets wrapping showed considerable improvement in shear capacity and ductility compared to the control specimen. Both PET and PEN showed no tendency to fiber breakage before the pre-defined ultimate deformation. Pier behaviors such as shear deformation and strain development in both fiber and steel shear reinforcement, and the piers, ultimate failure modes, were carefully examined. Shear deformation increases rather rapidly after peak load and concrete shear capacity decreases with the increase in shear deformation. Stiffness of fiber affects the development of shear deformation and the descending branch of the load–deformation curve after the peak load. A simple model to predict the piers deformation capacity, based on the experimental results, was proposed.