Test on mechanical behavior of pultruded concrete-filled GFRP tubular short columns after elevated temperatures

This paper presents an experimental investigation on the mechanical behavior of pultruded concrete-filled GFRP tubular (CFGT) short columns exposed to elevated temperatures under axial compressive loading. A total of 117 pultruded CFGT short columns subjected to different elevated temperatures and temperature duration were axially tested, including 108 specimens after elevated temperature and 9 specimens at ambient temperature served as the control group. The main variables explored in this paper included the GFRP tube thickness, concrete compressive strength, elevated temperature, and temperature duration. The results obtained from the experiments indicate that the ultimate strength and initial stiffness of specimens decrease remarkably with the increase of the elevated temperature, while the ductility of specimens is enhanced accordingly. Especially, the elevated temperature causes an obvious reduction (about 37%) in the ultimate strength of specimens when it exceeds 200 degrees C. Among the four main variables, the elevated temperature exerts the most significant impacts on the ultimate strength of specimens, the GFRP tube thickness and concrete compressive strength have certain positive effects, while the influence of temperature duration is almost negligible. Based on the experimental results, a parameter formula for the calculation of the ultimate strength of pultruded CFGT short columns after elevated temperatures is proposed, which shows great accuracy and rationality compared with the test results.