Recently, various strengthening methods have been utilized to enhance the structural performance and extend the life cycle of RC structures. However, the existing strengthening methods still have some drawbacks especially in the durability aspect. In this study, with the outstanding properties of UFC (i.e., high strength, ductility, and durability), a new flexural strengthening method using precast UFC panels was used to strengthen the RC beams. However, to obtain greater strengthening effect and durability, PC strands were pre-tensioned to the panel and this panel was subjected to a heat curing procedure to supplement a hydration procedure and eliminate the effect of shrinkage. Using this novel technology, this research was conducted to investigate the flexural enhancement and corresponding behavior of RC beams strengthened by pre-tensioned UFC panel. Five pre-tensioned UFC panels and eight strengthened RC beams were prepared and investigated using the bending test. Two different experimental parameters, i.e., prestressing level and amount of PC strands, were used. The undercut anchor bolts were applied for sufficient bonding between interfaces. The bending results of panels were investigated to compute the exact prestressing level in order to determine the calculation of prestressing losses. The results of the strengthened beams revealed that the pre-tensioned UFC panel drastically enhanced the loading capacity of RC beams, and each variable parameter affected the different structural characteristics. To ensure compatibility along a cross-section of the strengthening system, the compatibility along panel specimens and strengthened RC beams was investigated. Finally, the strain compatibility was satisfied at the mid-span of beams where the calculation of load-carrying capacity in strengthened beams could be carried out by using conventional flexural section analysis.
2016 Japan Society of Civil Engineers