Shear capacity and failure behavior of DFRCC repaired RC beams at tensile region

Many shear dominant structural members in existing concrete structures have been evaluated as below serviceable standard requiring strengthening and/or repair. In order to repair these aged reinforced concrete (RC) structures, a section replacement method of removal and replacement of old concrete and/or steel reinforcements of damaged sections with new concrete and/or steel reinforcements are commonly used. However, this repairing method is used without understanding the complicated structural behavior such as shear behavior of RC structures. Also, the materials commonly used for repairing are concrete and cement mortar. In order to implement the material superiority of newly developed cement based material and to complement the disadvantages of cement-based construction materials such as brittleness of failure, Ductile Fiber Reinforced Cementitious Composite (DFRCC), a high performance cementitious composite with superior strain capacity, is currently being used as a repair material. However, the composite behavior between old substrate and new repair material is not clearly understood at present. In order to effectively apply DFRCC as repairing material on RC structure, the interface, the weakest part in the repaired system where most failures occur, must be studied in depth. In this research, the composite behavior of a RC flexural member repaired using the superior tensile capacity of DFRCC on the tensile face of a RC specimen is studied. Two types of DFRCC repaired RC specimens are tested, one is without shear stirrups and the other is with shear stirrups. By comparing these two types of DFRCC repaired specimens, the failure mechanism and interface debonding behavior as well as repairing capacity can be effectively studied.