Assessment of the static and impact resistance behavior of flexurally strengthened RC beams by bonding medium-elasticity CFRP sheets

Fiber-reinforced polymer (FRP) sheet bonding methods are used in practice as a way of strengthening reinforced concrete (RC) structural members under static and quasistatic loading. The applicability of RC members under impact loading has been investigated since 1990. Generally, carbon FRP (CFRP) sheets and aramid FRP (AFRP) sheets have been used in Japan as strengthening materials for FRP sheets in RC infrastructure. Although only one material is normally used for an AFRP sheet, three types of materials are used for a CFRP sheet: high strength, medium elasticity and high elasticity. Usually, a high-strength sheet is applied for strengthening RC members because it has the largest fracture strain of the three types, and medium- and high-elasticity sheets are used for steel members because their Young’s modulus values are more than twice those of steel members. In this work, static and drop-weight impact loading tests for flexurally strengthened RC beams with medium-elasticity bonding (Beam ME) were conducted to investigate the applicability of this sheet to flexurally strengthened RC beams. RC beams with high-strength (Beam HS) bonding sheets of similar axial stiffness to Beam ME and without the bonding FRP sheet (Beam N) were also tested to compare the load-carrying behavior of the RC beams. The results are as follows: Beams ME and HS fail by sheet rupturing and debonding, respectively, under static loading and impact loading; Beam ME can assure the calculated load-carrying capacity statically; however, this beam reaches the ultimate state under a lower impact energy than Beam HS does.