Experimental and numerical investigation on the axial compressive behavior of UPVC square tubes

• The constitutive model for UPVC was firstly proposed based on Sherwood 7-term polynomial. • Axial compression tests and refined numeral analysis were conducted on UPVC square tubes. • The failure modes of UPVC square tubes associated with varying slenderness ratios were investigated. • The applicability of existing standards for evaluating the load-bearing capacity of UPVC square pipes was analyzed. UPVC (Unplasticized Polyvinyl Chloride) is a novel construction material. Currently, there is a lack of comprehensive research on the fundamental mechanical properties of this material, particularly regarding UPVC square tubes, for which studies are rarely reported. To investigate the axial compressive performance of UPVC square tubes, static tests were conducted on six sets of UPVC specimens with different slenderness ratios. The failure modes and ultimate bearing capacities of these members were analyzed and compared with the calculation methods outlined in existing national and international standards. The results indicate that as the slenderness ratio of the member increases, the bearing capacity of the UPVC square tube gradually decreases, and the failure mode transitions from local buckling to overall instability. When the slenderness ratio of the member is small, the initial imperfections have a significant impact on the stability coefficient, whereas the thickness of the end plates has no effect on the stability coefficient of the member. As the width-to-thickness ratio is between 6 and 35, its influence on the axial compression stability coefficient of the square tube is relatively small. When the slenderness ratio is either λ < 20 or λ > 80, the yield strength and elastic modulus of the material have minimal influence on the overall stability coefficient. However, when 20 ≤ λ ≤ 80, the overall stability coefficient of the member distinctly increases with the enhancement of the elastic modulus and the reduction of the yield strength.