Bond properties of steel angles in concrete filled steel tubes

The performance of concrete filled steel tubes (CFSTs) in tensile actions can effectively be improved by inner steel L-profiles embedded in the core concrete. In order to investigate the bond properties between the steel angle and core concrete, 24 pull-out specimens with variable bond length and cross-section area were tested. The results suggest that the peak value of the pull-out load increases with the bond length and the cross-section area when the peak load is reached before yielding and the average bond strength and the average residual strength are not dependent on the two parameters referred to. A formula is proposed to calculate the characteristic pull-out resistance of steel angles embedded in CFSTs, and the bond-slip constitutive relationship is obtained based on the analysis of interfacial bond stress and slipping. Further comparisons with previous studies illustrate that the circumferential constraint provided by the steel tube can effectively increase the residual bond strength and the bond ductility. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study focuses on the bond properties between steel angles and core concrete in CFSTs, proposing a formula to calculate the characteristic pull-out resistance. It is found that peak pull-out load increases with bond length and cross-section area, while average bond strength and residual strength are not dependent on these parameters. The study also shows that the circumferential constraint provided by the steel tube can effectively increase the residual bond strength and ductility.