Experimental study of the quasi-static axial compressive resistance of pultruded GFRP composite stub columns

This paper presents an experimental investigation on the crushing behaviour of full-section pultruded glass fibre reinforced polymer (pGFRP) profiles with 11 different cross-section geometries, encompassing 6 different shapes (C, I, W, SHS, RHS, L sections). Quasi-static axial compressive tests were conducted on stub column specimens, mitigating second-order and buckling effects. The crushing phenomenon of the pGFRP profiles was investigated regarding the following aspects: (i) influence of end surface flatness, (ii) analysis of load/stress vs. strain behaviour, (iii) definition of relative slenderness thresholds to avoid buckling, (iv) determination of full-section compressive strength for various cross-sections, and (v) correlation of geometrical and mechanical experimental data. The results show that when the relative slenderness was limited to 0.7, no buckling occurred, and the load was uniformly applied across the section of the profiles. Additionally, for the different cross-section geometries, the estimates of resistance to crushing of pGFRP stub columns obtained from compressive coupon tests were non-conservative: in average, the resistance to crushing of full-section stub columns was around 60 % of those estimates. Unlike the coupon tests, the stub columns presented complex failure with multiple damage modes, which were attributed to the non-uniformity of material properties across the section walls. The correlation analysis provided insights into the linear dependency of the full-section compressive strength with geometrical and material properties. Surprisingly, shear strengths were shown to play a more relevant role in the crushing phenomenon of stub columns than compressive strength. The findings of this study will contribute to the drafting of improved design guidelines able to estimate more accurately (and likely more reliably) the compressive resistance to crushing.