Behavior of CFRP strengthened columns damaged by thermal shock

 In the last two decades, using of Carbon Fiber Reinforced Polymers (CFRP) in strengthening of deficient reinforced concrete structural elements has been increased due to their ease of installation, low invasiveness, high corrosion resistance, and high strength to weight ratio. Strengthening damage structures is a relatively new technique. This paper presents a nonlinear finite element analysis (NLFEA) results of reinforced concrete columns confined externally with carbon fiber reinforced polymers (CFRP) subjected to thermal shock impact. After reasonable validation of NLFEA with the experimental test results of companion columns, NLFEA was expanded to provide a parametric study of eighteen columns that correlates the ultimate axial stress of CFRP-confined RC columns to number of CFRP layers and damaged thermal shock. Thermal shock has a significant impact on the behavior of CFRP-confined circular RC columns. The increase in ductility is directly related to a decrease of compressive strength due to thermal shock. Also, the confinement effectiveness in terms of ultimate load was decreased with the increase in concrete compressive strength (un-damaged). The influence of the number of CFRP layers on the ductility, energy absorption, and ultimate load improvement percentage is significant. There will be no further significant increase in the ductility and ultimate load of the column after a certain volumetric ratio, while significant increase in its stiffness continues to occur.