Effect of Elevated Temperatures on the Web Crippling Behavior of Pultruded GFRP I-Section Profiles

Abstract

Pultruded glass fiber–reinforced polymer (GFRP) profiles can serve as purlins and beams, replacing traditional steel profiles in corrosion-resistant industrial buildings. However, these GFRP members may exhibit web crippling behavior under transverse concentrated loads, especially at elevated temperatures, a phenomenon that is not sufficiently understood. To narrow this knowledge gap, web crippling experiments were conducted on pultruded GFRP I-section profiles across seven target temperatures (20°C, 40°C, 60°C, 100°C, 140°C, 180°C, and 250°C) with different bearing lengths (25, 50, and 100 mm) using the interior two-flange loading configuration. During the experiments, failure was dominated by local crushing at the web–flange junction, accompanied by local bending, kinking, and delamination. The web crippling capacity was severely degraded by elevated temperatures; for instance, the capacity of specimens with a 100-mm bearing length was reduced to 65.6% at 40°C and merely 6.3% (7.8 kN) at 140°C compared to that at room temperature, yet their failure modes demonstrated a degree of deformability. The degradation of the web crippling capacity was consistent with the reduction in the transverse compressive strength of the GFRP composites, suggesting that the web crippling capacity was mainly dominated by high-temperature transverse compressive strength. The capacity was reduced by 32.5% and 51.7% when the bearing length was decreased from 100 to 50 and 25 mm, respectively, at ambient temperature, although the extent of this reduction was considerably more severe at elevated temperatures. Furthermore, the current design equations and existing models were assessed in predicting web crippling capacity at elevated temperatures. A straightforward model governed by transverse compressive strength was developed to predict the web crippling capacities at elevated temperatures.