Axial-flexural behaviours of concrete-filled square GFRP tubular columns under low temperatures

This study reported experimental investigations on the axial-flexural behaviours of concrete-filled square glass fiber-reinforced polymer (GFRP) tubular (CFSFT) columns at low temperatures. Twenty CFSFT columns under eccentric loads and two-point loading were conducted to evaluate the influences of low temperatures (T = 20 and -60 degrees C) and eccentricity ratios (e/r = 0.00, 0.25, 0.50, and 0.75). Failure modes, load-displacement behaviours, and load-strain behaviours at low temperatures have been reported. Test results indicated the load-vertical displacement curves of CFSFT columns under eccentric loads exhibited three different stages, i.e., linear, tran-sition, and strain hardening or softening stage. Meanwhile, the bilinear load-deflection curves were observed for CFSFT columns under four-point bending. Based on these test results, the experimental axial load-moment (NT -MT) curves of CFSFT columns were obtained. These curves indicated that decreasing the temperature from 20 to -60 degrees C observably increased both the ultimate axial load (NuT) and ultimate bending moment (MuT) of CFSFT columns. However, the increment of both ultimate axial load and ultimate bending moment gradually decreased with the increasing eccentricity ratios.