Experimental Study On Shear Behavior And Behavior At Elevated Temperature Of RC Beams Strengthened With High-performance Ferrocement

It is required to strengthen and repair structures in use which are not serviceable or safe because of various factors. A new kind of strengthening method with high performance ferrocement (HPF) has a lot of superior advantages and the people in structural strengthening domain pay great attention to it and are interested in it more and more.The HPF strengthening method regularly adopts U-type layer to strengthen RC beams, and the layer tends to debond, the strengthened beams tend to collapse brittle since the remarkable reduction of load bearing capacity. Compared with the strengthening method with steel sheets or FRP which uses organic agglutinant, the HPF strengthening method using inorganic bond material has superior fire resistance and elevated temperature resistance, but the thickness of layer is small, so it is necessary to research the fire resistance and elevated temperature resistance in depth.To above issues, the shear behavior of 5 RC beams strengthened with U-type HPF layer and 1 RC beam was researched. The failure mode and debonding failure mechanism were analyzed, the effect of debonding to load bearing capacity was researched. According to the strut-tie model and experiment results, a calculating formula of load bearing capacity considering the debongding factor k was put forward, and the calculating results have favorable accuracy. In addition, the behavior at elevated temperature of 5 strengthened beams and 1 RC beam was examined. The performance of strengthened beams in fire was simulated, the failure mode and failure temperature were investigated, and the fire resistance of strengthened beams was analyzed quantitatively by regarding the failure time as refractory limit approximately, and the detailing requirements about the thickness of HPF considering fire resistance.The construction quality has a strong impact on the shear behavior and fire resistance of strengthened beams. It was regulated that the debonding factor k sampled different values along with different construction quality level. The effect of interfacial bond behavior to fire resistance was analyzed, and the construction technical requirements considering fire resistance was put forward.