Evaluation of damaged rc beams strengthened in flexure by pre-tensioned ufc panel

Various advanced materials have been applied to repair and strengthen damaged RC structures. Most of strengthening methods are mainly focused on the enhancement of structural capacity, while the consideration of its durability is often neglected in severe environment. Therefore, the new flexural strengthening method was proposed in this study to strengthen damaged RC structures and improve the durability by using the pre-tensioned UFC (Ultra high strength fiber reinforced concrete) panel. With the outstanding properties of UFC, it was adopted to pre-fabricate as the panel which was prestressed by PC strands for obtaining greater strengthening effect and inducing higher durability. The sufficient bonding between a RC beam and the panel was fulfilled by the undercut anchor bolts. To investigate the flexural enhancement, eight strengthened beams were subjected to a bending test. The RC beams were reinforced by different amount of tensile bars for simulating the damage level of beams. Other parameters were varied in the panels: The amount of PC strands and the prestressing level of panel. The results indicated that the influence of pre-tensioned UFC panels drastically increases the capacity of damaged beams. The effect of each parameter significantly improves different structural response: The increasing amount of PC strands can highly affect the loading capacity while the higher prestressing level influences the delay of cracking. The compatibility between RC beam and the panel is ensured in the mid-span section through the calculation; thus, the loading capacity of strengthened beams can be estimated. The comparisons of experimental value and calculation show good agreement in case of flexure-tension failure.