Performance of T-shaped CFST columns with embedded T-shaped steel skeleton under axial compression

With the proliferation of large-span structures and super high-rise building structures, further requirements have been placed on the bearing capacity and mechanical performance of special-shaped concrete-filled steel tubular (CFST) columns. In an effort to improve the performance of traditional T-shaped CFST columns, a series of axial compression experiments and numerical simulations were conducted on eight middle-long T-shaped CFST columns with embedded T-shaped steel skeleton, with the studied parameters covering diverse T-shaped steel tube confinement index (θ), embedded T-shaped steel skeleton ratio (ρ) and slenderness ratio (λ). The investigation contents include analysis of failure modes, load-mid span deflection curves, load-longitudinal and transverse strain curves, load-average longitudinal curves and parameter analysis. The experimental failure modes for all columns are a combination of local buckling and overall bending. Results demonstrate that the ultimate bearing capacity (Nu) of the columns increases with higher values of θ and ρ while decreases with higher values of λ. As λ increases, the global bending failure of the column becomes increasingly pronounced. Furthermore, finite element analysis (FEA) models were built to simulate the axial compression mechanical performance of middle-long T-shaped CFST columns with embedded T-shaped steel skeleton. The simulation results were then compared with experimental results to validate the feasibility of the FEA models. Finally, simplified calculation formulae for estimating the ultimate load-bearing capacity of middle-long columns were suggested. The calculation results are indicative of notable agreement with the experimental results. •The paper presents an experimental study on T-shaped CFST columns with embedded T-shaped steel skeleton.•The composite columns shows excellent load-bearing capacity, ductility and deformation ability.•T-shaped steel skeleton improves the strength and the ductility capacity of composite columns•A finite element analysis for composite columns is developed.•A simplified calculation formula for composite columns is developed.