Shear Strengthening by Externally Post-tensioning Steel Rod in Fire-Damaged Reinforced Concrete (RC) Beam

The purpose of this study is to discuss the applicability, strengthening effect and improvements when an externally post-tensioned steel rod system is applied to a fire-damaged reinforced concrete (RC) beam. A total of twelve specimens were prepared in three groups and tested to fail. Group one was not heated, and group two and group three were heated to 700C and 1,000C, respectively. In each group, one beam without externally post-tensioned steel rods was designated as a control beam and three beams had the externally post-tensioned steel rods of 18 mm, 22 mm or 28 mm in diameter. The initial effective tension of about 2,000 was applied to the steel rods. Test results indicated that this can be applied to fire-damaged RC because externally post-tensioning increased the load-carrying capacity by more than 67%. However, additional reinforcement is required in the part where the deviator and anchorage are installed since the concrete surface is weakened by moisture evaporation at high temperatures.