Predicting Flange Local Buckling Capacity of Pultruded GFRP I-Sections Subject to Flexure

Abstract

Flange local buckling (FLB) of pultruded glass fiber-reinforced polymer (pGFRP) I-sections subject to flexure is investigated in this study. An experimental program, consisting of 62 four-point bending tests that had various constant moment region and shear span lengths, was conducted. It was shown that critical FLB moment capacities increased as the flange slenderness ratios decreased and FLB was the dominant buckling mode for sections that had large flange slenderness ratios. Using classic plate theory and the energy method, an analytical study was carried out and an explicit equation for predicting the critical FLB moments of pGFRP I-sections was proposed. The elastic rotational restraint at the flange–web junction was studied and a modified spring constant, k, was proposed. In addition, the buckling stiffening effect of the test geometry was described through a numerical study. The proposed predictive FLB equation was validated using experimental results from this study and others and was compared with two commonly accepted design guides, Kollár's numeric solution, and finite strip method (FSM) solutions. A good agreement was found between the proposed equation and experimental results and FSM. The proposed equation showed improved predictive accuracy over existing design guides and numeric solutions.