Flexural stability of pultruded glass fibre-reinforced polymer I-sections

Abstract

An extensive experimental and analytical study investigating the stability of pultruded glass fibre-reinforced polymer (pGFRP) I-sections subject to flexure is reported. To investigate flange local buckling (FLB), specimens with flange slenderness ratios (b/2t) from 4 to 12 were tested. Lateral torsional buckling (LTB) was investigated in specimens having slenderness (Lb/r) ranging from 24 to 52. Through a comparative study with the experimental results, existing standards and the established closed-form mechanics-based equations were found to underestimate the critical FLB moment capacities of pGFRP I-sections. The finite-strip method is demonstrated to predict critical FLB moments with satisfactory accuracy. It is shown that the interaction between FLB and/or web local buckling and global LTB may lead to a reduction of critical FLB moment capacity. Such interaction tends to occur in sections having small flange slenderness ratios as well as large longitudinal lateral slenderness ratios. On the other hand, the predictions of LTB capacity were generally found to be non-conservative when compared with experimentally determined results. Such discrepancies between experimental and analytical results tend to become more significant for sections having relatively large flange slenderness ratios as well as small longitudinal lateral slenderness ratios. This underestimation of LTB moment capacity is found to result from the interaction between local and global buckling behaviours of pGFRP I-sections.