Eccentric compression behaviour of raw coal gangue CFST slender columns

Raw coal gangue concrete-filled steel tubular (RCGCFST) member is proposed to expand the application of RCG concrete in structural members. However, research on RCGCFST members has primarily focused on axial compression and bond behaviour. This paper explores both experimental and numerical analyses of the behaviour of RCGCFST slender columns subjected to eccentric compression. Twenty-one slender columns were tested to obtain the failure modes, load versus mid-height deflection responses, and load versus strain relationships. Key parameters studied included the raw coal gangue (RCG) replacement rate, steel tube diameter and thickness, slenderness ratio, eccentricity ratio, and water-to-cement ratio of concrete. The test results indicated that incorporating RCG had a moderate influence on the eccentric compression behaviour of the specimens. In addition, a finite element (FE) model was established and benchmarked against the test data. A parametric study employing the FE model was performed to evaluate the effects of the RCG replacement level, steel tube diameter, slenderness ratio, eccentricity ratio, steel ratio, and material strength on the eccentric compression performance of RCGCFST slender columns. Finally, several existing design methods for normal CFST columns were evaluated for their applicability to RCGCFST columns.