Strengthening of R/C existing columns with high performance fiber reinforced concrete jacket.

The possibility of strengthening existing R/C columns with a new technique based on the application of a High Performance Fiber Reinforced Concrete (HPFRC) jacket has been investigated herein. Previous researches, carried out by the Authors, shown the effectiveness of the proposed solution applied to beam elements under flexure. In the present paper, the effect of High Performance Fiber Reinforced Concrete jacketing on columns subjected to both axial load and bending moment is analyzed by analytically drawing interaction envelopes. The results will be compared with the response of columns reinforced with a traditional R/C jacket. externally glued steel plates as well as of FRPs may have problems for fire resistance. Furthermore, the use of FRPs mat not satisfy minimum requirements for Serviceability Limit States. Recently, a new technique has been developed for reinforcing beam under flexure (Martinola et al., 2007a; Maisto et al., 2007; Martinola et al., 2007b). This solution is based on the application of a thin jacket in High Performance Fiber Reinforced Concrete (HPFRC) with a high compressive strength and a hardening behavior in tension (di Prisco et al., 2004; Carpinteri et. al., 2007; Naaman & Reinhardt, 2007). The latter property allows to use this material in substitution of the traditional steel reinforcement. Structural effects of a 40 mm thick HPFRC jacket were investigated by testing full-scale beams having a depth of 500 mm and a span of 4.55 m (Fig. 1). Results show a remarkable increase of the bearing capacity coupled with a great stiffness increase (Fig. 2; Martinola et al., 2007a). Particular attention has been devoted to the application technology of the HPFRC jacket. In previous research studies it was demonstrated that a sandblasting giving a roughness of about 1–2 mm allows a