Experimental and numerical behavior of eccentrically loaded square concrete-filled steel tubular long columns made of high-strength steel and concrete

Abstract

The high-strength materials are increasingly used in the concrete-filled steel tubular (CFST) column to improve its mechanical behaviors. This study aims to evaluate the fundamental behavior of high-strength concrete-filled high-strength square steel tubular (HCFHSST) long columns under eccentric compression. A series of tests were conducted on eccentrically loaded HCFHSST long columns to investigate the mechanical characteristics and failure mechanisms. Numerical investigations were systematically performed to explore the load-carrying performance of the column. Meanwhile, parametric studies were implemented to evaluate influences of several key parameters on the strength increase factor (SIF), P–M, and P/P0–M/M0 curves of the HCFHSST members, respectively. Furthermore, the equations were proposed to predict the peak-loads of HCFHSST long columns under eccentric loading. The experimental and simulated peak-loads were compared with the results of various design codes and recommended equations to assess the feasibilities of those calculation systems. The results demonstrated that the bending moment–curvature curves of the experimental specimens could be categorized into three types considering the second-order effect. Additionally, it was numerically observed that using high-strength steel can enhance the yield load proportion of the column, and the concrete withstands most of the applied load when utilizing high-strength concrete as infill. Based on the peak-load calculations of codes EC4, AISC 360, and GB 50936, it was found that code GB 50936 presented a better result on average while was unsafe for some cases with high e/B ratios. The equations proposed in this study can provide an improved prediction and hence are suggested.