Assessment of creep rupture and long-term performance of GFRP bars subjected to different environmental exposure conditions under high sustained loads

Abstract This paper presents an experimental investigation and statistical approach to assess the long-term performance and to determine a safe creep-rupture strength value for glass fiber-reinforced polymer (GFRP) bars subjected to different types of environmental exposure. The study sample consisted of 160 bars of various sizes (10 mm, 12 mm, and two types of 15 mm) subjected to different levels of environmental conditioning (unconditioned and exposed to an alkaline solution at 23 °C and 60 °C) and a range of sustained load levels (40% to 90% of the ultimate tensile strength). The test results were analyzed with Weibull statistical analysis to determine the mean and characteristic creep-rupture strengths, and consequently, a safe design value was calculated. Limitations and variations of the strength degradation model for the life-span prediction are discussed. The impact of sustained load on strength reduction was more pronounced than the combined effect of the alkaline solution and high temperature. The GFRP bars with smaller diameters were more susceptible to creep rupture than the larger ones, while the conditioning had more effect on the bars with larger diameters than the smaller ones. The creep-rupture reduction factors prescribed in current design codes are conservative for the GFRP bars in this study.