Deformation capacity of concrete beams reinforced by partially unbonded composite bar
Gao Xiang1,2 Sun Zeyang1 Sun Yunlou1 He Xiaoyuan3 Wu Gang1
1. Key Laboratory of C&PC Structures of Ministry of Education, Southeast University, Nanjing 211118, China；
2. Tsinghua University, Beijing 100084, China；3. School of Civil Engineering, Southeast University, Nanjing 211118, China
Abstract：The steel-fiber-reinforced polymer (FRP) composite bar (SFCB) consists of an inner steel bar and an outer fiber composite material, and has the advantages of high durability and controllable post-yield stiffness. Owing to the relatively low ultimate elongation rate of FRP, the ultimate state of SFCB-reinforced concrete members is typically determined by the fracture strain of FRP. To improve the deformation capacity of SFCB-reinforced concrete beams, this study experimentally investigated SFCB. reinforced concrete beams with a varying unbonded length. The displacement field of the concrete beams was measured using the digital image correlation (DIC) technique, and the influence of the unbonded length on the deformation capacity and bearing capacity of the SFCB-reinforced concrete beams was investigated. The results reveal that, as the unbonded length increased, the crack height, width, and interval of the SFCB concrete beams gradually increased, and the concrete in the compression zone collapsed earlier. The ratio of the post-yield stiffness to the post-crack stiffness of the SFCB beams was relatively stable, that is, approximately 22%. The average strain of the concrete surface at mid-span still obeyed the plane-section assumption when the unbonded section was set at mid-span. Appropriately setting the unbonded length is beneficial in reducing the strain of the mid-span tension-bars and improving the flexural bearing capacity and deformation capacity of SFCB concrete beams.
