Theoretic failure modes map for GFRP SHS columns under compression with experimental validation

Although pultruded glass fibre reinforced polymer (GFRP) columns under compression have been investigated in the last two decades, results on square hollow sections (SHS) are still limited. In general, three failure modes are categorized: compressive failure, local buckling and global buckling. In this paper, the critical loads for different failure modes of GFRP SHS columns are analysed. Analytical formulations for the boundaries of different failure modes are received, with quantifications of the effects of column slenderness (non-dimensional slenderness, X) and plate slenderness (width-thickness ratio, b/t). It demonstrates that local buckling will occur on GFRP columns if the b/t is greater than a critical value; compressive failure will occur if b/t is less than the critical value; global buckling will occur if X is greater than 1 and b/t less than a critical value. Furthermore, a failure modes map against X and b/t is formed. Based on this approach, the failure mode of a GFRP column can be determined with knowing its geometric parameters X and b/t, and therefore the corresponding load capacity can be determined accordingly. The failure modes map and load capacities of GFRP SHS columns are well validated by experimental results with different X and b/t.