Test, simulation and design of square concrete-filled steel tubular stub columns fabricated with high-strength materials under biaxial eccentric loading

Abstract

This work aims to determine the biaxial eccentric performance of high-strength concrete-filled steel tubular (HCFST) stub columns. Ten specimens were tested under combined axial load and biaxial moment to evaluate the failure process, with the parameters of eccentricity ratio and steel ratio varied in the tests. Numerical studies were carried out to explore the working mechanism of the column, and parametric investigations were implemented to confirm the key factors affecting the behavior of the biaxially loaded columns. Codes AISC 360 and GB 50936 were adopted to examine the load-bearing capacities of the column, and a new design model was further proposed, together with the reliability analysis. The results showed that the biaxially loaded HCFST stub column failure exhibits concave regional yielding and concrete crushing. The concave regional longitudinal stress enhances with the eccentricity ratio, while the transverse stress presents an opposite trend before the concave yielding. Furthermore, it is numerically identified that enhancing the steel contribution is beneficial to the high e/B' ratio case. Based on the ultimate load capacity predictions from AISC 360 and GB 50936, it is noted that both codes provide conservative estimations, while the proposed model exhibits a closer prediction with the test results and thus being recommended for design of biaxially loaded HCFST stub columns.