Mechanical behavior of high-strength concrete filled high-strength steel tubular stub columns stiffened with encased I-shaped CFRP profile under axial compression

A new composite column that consists of high-strength square steel tube, high-strength concrete, and carbon fiber reinforced polymer (CFRP) profile with a I-shaped cross section was developed and investigated in this study. This paper experimentally and numerically investigated axially loaded behavior of high-strength concrete filled high-strength steel tubular (HCFHSST) stub column with an encased I-shaped CFRP profile. In the experimental study, axial compression tests were completed on eight specimens to examine the axial load response of the composite column, including the load-displacement curves, failure mode, and strain distribution. Finite element models of the composite column were developed using ABAQUS and validated by comparing numerical results with experimental data. The validated models were used to further investigate the load sharing and transferring mechanism for each component of the composite column. Results showed that the composite column comprehensively used the advantageous merits of concrete, steel tube, and CFRP as a unit to share the applied load at different loading stages: linearly elastic, elastic-plastic, hardening, post-peak descending, and residual plateau stage. Parametric studies were performed that assessed influences of critical design parameters on the axially loaded behavior of the stub column. The examined parameters included the compressive strength of high-strength concrete, yield strength of high-strength steel, and steel ratio. Finally, empirical equations were proposed to determine the ultimate vertical strain and the ultimate axial load capacity of the HCFHSST stub column encased with a I-shaped CFRP profile.