Experimental and numerical study of resistance of multi-cell L-shaped concrete-filled steel tubular stub columns under biaxial eccentric compressive loading

This study aims to understand the cross-sectional resistance and develop practical resistance equations for multi-cell L-shaped concrete-filled steel tubular (ML-CFST) stub columns under biaxial eccentric compressive loading based on experimental testing and numerical analysis. Eighteen specimens were firstly tested to investigate experimentally their failure modes, nonlinear structural behavior, and the influence of different loading angles (& theta;) and eccentricities on the load-carrying capacity. Secondly, detailed nonlinear finite element models were developed and validated against test results, and further used for parametric analysis to explore untested scenarios. This facilitated the construction of a failure surface, which was interpreted as a family of Mx-My interaction curves under a variety of axial compression ratios (n), where Mx and My are the bending moments about the minor and major axes, respectively. Results showed that MLCFST specimens exhibited favorable structural performance, and n and & theta; had a considerable influence on the normalized Mx-My interaction curves, compared to other geometric and material strength parameters (i.e., depth-to-width ratio of section limb, steel-to-concrete area ratio, steel yield strength and concrete compressive strength) studied. To facilitate engineering use, a dimensionless interaction equation for normalized Mx-My was developed in good agreement with experimental results.