Experimental Study of Post-heated Steel Reinforced Recycled Concrete Columns Repaired with CFRP

Abstract

The mechanical and thermal properties of steel reinforced concrete columns with CFRP reinforcement were examined after exposure to a high temperature of 500 oC. The concrete made with normal and recycled coarse aggregate (RCA) was fabricated and three different RCA replacement ratios (0, 50%, and 100%) were investigated. The fatigue properties of steel reinforced concrete with RCA and CFRP reinforcement were tested for two million cycles at a frequency of 2.5 Hz. The test results show that the failure of strengthened specimens is mainly caused by rupture of CFRP jacket and buckling of inner section steel reinforcement. However, for the unstrengthened specimen, both of inner steel buckling and core concrete cracking are the main contributors to the damage. The load-bearing capacity, deformation and energy dissipation of the specimens during the fatigue test could be strengthened greatly by CFRP reinforcement. However, the CFRP reinforcement has little influence on the improvement of the stiffness of the specimens, which may be caused by a plastic damage accumulation during the early cycles of fatigue tests. Finally, a static test was conducted on the post-fatigue specimens, the results showed that a large decrease in stiffness was observed for the specimens subjected to high temperature and fatigue, and the fatigue loading had a higher influence on the specimens than the high temperature.