Basic characteristics of FRP strand sheets and flexural behavior of RC beams strengthened with FRP strand sheets

When attaching continuous fiber sheets on concrete members on site, bonding defection of the continuous fiber sheets likely happens. FRP strips could solve the problem associated with the continuous fiber sheets, though they also have demerit due to less adhesion property caused by small adhesive area. To solve these problems, we have developed advanced FRP strand sheets which consist of bunch of individually hardened continuous fiber strands. The FRP strand sheets can be easily attached on the surface of concrete members with a single adhesive. Thus, the advanced strand sheets assure better construction quality and enable to cut down on application time and/or costs. Series of tensile, lap splice, and bonding tests were conducted in order to evaluate the material characteristics of CFRP strand sheets. Bending test of RC (Reinforced Concrete) beams was also conducted to evaluate strengthening effect of the CFRP strand sheets. In each test, specimens strengthened with CFRP strand sheets, with ordinal carbon fiber sheets or with CFRP strips were prepared. In the bending test, it was observed that both bending stiffness and capacity of RC beams were increased by strengthening with CFRP strand sheets. It was also observed that ultimate load, which was determined by delamination of strengthening material; of specimen strengthened with CFRP strand sheets was the greatest among all the specimens. Furthermore, the influence of concrete strength and depth of cover concrete on flexural strengthening effect of the FRP strand sheets were investigated.