1. INTRODUCTION
Nowadays, strengthening by post casting concrete, steel plate jacketing, fiber reinforcements such as carbon, aramid, and glass are utilized as seismic strengthening methods for concrete structures. Recently, a seismic strengthening method by wrapping continuous fiber sheets has often been used, since the constructibility and durability is superior. However, materials using continuous fibers are expensive. On the spread of seismic strengthening for buildings and infrastructures in future, simple methods of strengthening with low cost should not only be suggested, but also seismic behaviors should be cleared.
In this study, a new, inexpensive, and simple strengthening method for concrete structures is discussed and suggested in order to improve future seismic strengthening. This method using short fibers with vinyl ester is a new combination of materials as seismic strengthening. Chopped short fibers of carbon and glass with vinyl ester resin are sprayed in place on the concrete structures. It is called "Sprayed FRP (Fiber Reinforced Polymer)." Benefits of using vinyl ester resin in this strengthening method are that it takes shorter time to harden the resin than epoxy resin. In addition, the mechanical properties of vinyl ester resin are the same as the one of epoxy resin.
In this paper, the outlines of sprayed FRP strengthening method and the results of column and T-shape beam test under the anti-symmetrical loading are reported. In addition, the bond behavior between FRP and concrete, and anchoring behavior using slit (groove) filled by sprayed FRP are reported.