Experimental Study On Reinforced Concrete Beams Strengthened With Externally Bonded FRP With Fibre End Anchors

Externally bonded (EB) FRP, due to its high strength and low weight, has been increasingly used to strengthen existing reinforced concrete structures and other sturures due to its. However, debonding of FRP is a typical failure mode when EB FRP is used to strengthen concrete structures. As a result, the effectiveness of such strengthening is limited by the premature debonding of FRP. Provisions in most current design codes and guidelines suggest the use of end-anchorage systems to delay or even prevent FRP debonding. Against the above background, anchors made from FRP fiber, which are herein referred to as fibre anchors, are used to enhance the shear strengthening effects of EB FRP in this thesis. The research contents mainly include2parts as follows:(1) A test program on eighteen specially designed small concrete beams was carried out to investigate the influence of fibre anchors on FRP-to-concrete bond behaviour. The beam tests are used to investigate and understand the influence of key factors, such as anchor types, anchor positions, anchor sizes, anchor numbers and FRP plate widths, on the bond behavior. The test results showed that with optimized fibre anchors arranment, the debonding failure can be effectively avoided; as a result, the loading capacity and ductility of the small can be apparently improved.(2) Information obtained from the small beam tests were then used to design/optimize the fiber anchors used in shear strengthening of RC beam, and comparisions were made between shear strengthening EB FRPs with and without fiber anchors. To explore the shear interaction among shear strengthening EB FRP (with and without fiber anchors), concrete and steel stirrups, a total of six full-size RC T-beams with a clear span of3400were prepared and tested. The beams specimens were divided into two groups. Group one consists of three beams without internal steel stirrups:one as control specimen, another one was shear strengthened with bonded FRP U-strips, and rest one was shear-strengthened FRP U-strips with fibre end anchors. The arrangement of three beams in group two was the same as group one (i.e. control beam, and two beams shear strengenthed with EB FRPs with and without fiber anchors) except that in this group, all beams have internal steel stirrups. The test results of T-section beams reveal that end-anchorage with fibers anchors can significantly improve the shear strengthening effects and ductility of EB FRP U strips, particularly for beams with stirrups.