Cyclic lateral behavior of NLFEA heat-damaged circular CFT steel columns confined at the end with CFRP composites

In this study, the nonlinear finite element analysis (NLFEA) method has been adopted to prove the CFRP's effectiveness in restoring the performance of heat-damaged CFT circular steel columns and controlling the columns' failure mode. The simulated CFT column model was firstly checked for validity using previously-conducted experimental research. Then, the model was extended to investigate the impact of the number of CFRP layers (0, 5, 6, 7, 8, 9, and 10 layers) and elevated temperature (20 °C, 200 °C, 400 °C, and 600 °C). Therefore, this study provides an NLFEA of twenty-eight models for CFT circular steel columns wrapped with various layers of CFRP composites at its end region, which represents the critical location in terms of the lateral load capacity. Also, wrapping the specimens' ends helps prevent the occurrence of outward local buckling, resulting in enhancing the specimens' strength, enlarging net drift, and increasing energy dissipation. The study results showed that using five to ten CFRP layers significantly improved the performance of the NLFEA CFT circular steel column models. Nevertheless, using nine or ten CFRP layers had almost the same impact of using eight layers. The NLFEA results showed that the external repairing of heated damaged CFT column with CFRP composite enhanced the cyclic performance, and the efficiency of CFRP composite increased with the heat damage level.