Global buckling capacity of pultruded FRP-I section columns under axial compression

This paper presents an improved closed-form solution to determine the global buckling loads of axially loaded pultruded fiber-reinforced polymer (PFRP) I-section columns based on the original solution recommended by Eurocode 3 (EC3). In this improved solution, a new closed-form equation to determine the reduction factor for global buckling of PFRP I-section members subjected to concentric compression is developed, based on the Ayrton-Perry formula and observed initial out-of-straightness of PFRP struts measured by other researchers. Recognizing that data on initial imperfections may be unavailable, a second new empirical closed-form equation is derived to predict the global buckling capacity of PFRP I-section columns based upon the experimental data. Validation of the two explicit solutions considering the influence of geometric imperfections of PFRP I-sections is performed by both comparison to experimental data and comparison with validated numerical simulations. In addition, compared with the five closed-form solutions available in the literature, the two proposed solutions display higher accuracy in predicting the global buckling loads of concentrically loaded PFRP I-section columns. Parametric studies are further conducted, and the influences of the main parameters on the performance of corresponding solutions are discussed. The two proposed solutions can facilitate the global buckling analysis and design of PFRP I-section members subjected to concentric compression.