Resistance of special-shaped concrete-filled steel tube columns under compression and bending

Abstract

Design procedures for L-shaped and T-shaped concrete-filled steel tube (CFST) columns subjected to bending and compression loading scenarios were developed through parametric study using finite element (FE) models verified by existing experimental results. The finite element study on this special-shaped CFST column subjected to pure bending considered parameters of steel-to-concrete ratio α, steel yield strength fy, concrete strength fck, and column limb width-to-thickness ratio B/tw (H/tw). For their behavior under eccentric compression, additional parameters of section stiffening pattern, loading angel θ, eccentricity, and axial compression ratio were included. Parametric analysis results show that steel-to-concrete ratio α, steel yield strength fy and column limb width-to-thickness ratio B/tw (H/tw) have obvious influences on the flexural resistances of the special-shaped CFST columns, while concrete strength fck has a small effect and can be ignored. The column limb width-to-thickness ratio B/tw, steel to concrete ratio α, steel yield strength fy, concrete compressive strength fck, loading angle θ, eccentricity e and section stiffening type have significant effects on the N-M correlation curves, and the convex portion of the N-M curves has a certain symmetry. The column limb width-to-thickness ratio B/tw and axial compression ratio n have significant effects on the shape of Mx-My correlation curves. Based on the FE analysis results, design formulae for calculating sectional flexural resistances were proposed for special-shaped CFST columns. Besides, simplified formulae were provided to conservatively predict the resistances of special-shaped CFST section and column under eccentric compression based on extensive analysis results of FE models.