Unified Theoretical Model for Axially Loaded Concrete-Filled Steel Tube Stub Columns with Different Cross-Sectional Shapes

Abstract

The existing theoretical models for the analysis of concrete-filled steel tube (CFST) columns are mainly limited to circular specimens. This paper is aimed at developing a unified theoretical model which is applicable to CFST columns with different cross-sectional shapes, including circular, square, rectangular and round-ended specimens. CFST columns with different shapes (original columns) were replaced with equivalent circular columns by assuming that they have the same sectional areas of core concrete and steel tube. The difference in the behavior between the original and equivalent CFST columns is attributed to the shape effect, which is indicated and modelled by a confinement effectiveness factor. Then, a unified theoretical model for axially loaded CFST columns with different cross-sectional shapes was developed based on an equivalent circular column with the shape effect considered. A total of 982 CFST columns, including 550 circular columns, 396 rectangular (and square) columns, and 36 round-ended columns, were collected to assess the proposed model. Results suggest that the proposed model is capable of accurately predicting the load-carrying capacity and load-deflection curves of CFST columns with different cross-sectional shapes. Finally, the proposed theoretical model was adopted to develop a unified design model of axial load-carrying capacity.