FRP Based Earthquake Retrofitting of RC Columns

Fiber reinforced polymer (FRP) materials are being used for the last two decades as reinforcement in new concrete structures and prestressing tendons in pretressed concrete structures. In addition, they are being used at large scale in external strengthening and/or retrofitting of deficient structures to restore the strength and stiffness of the structure to the design values or to meet the current code provisions. But, to make such structures capable of resisting the effects of strong earthquake shaking, at least a minimum stiffness, sufficient strength and adequate ductility are to be ensured. FRP laminates and FRP fabric sheets are used in external strengthening to provide the needed stiffness, strength, and ductility by suitably orientating the fibers and creating confinement. These FRP materials possess high tensile strength with moderate stiffness and are non-corrodible; they can be used efficiently for improving performance of structural elements, without increasing the earthquake forces. In this chapter, a unified design approach has been presented for earthquake retrofitting of RC columns; a design example is provided to demonstrate the effectiveness of FRP for seismic strength and ductility enhancements.