Axial compression behavior on novel H-shaped composite columns with UHPC-filled steel tube flanges and honeycombed steel webs

Ultra-high-performance concrete (UHPC) has high compressive strength and excellent durability, which make it have great potential in improving the bearing capacity of concrete-filled steel tube (CFST). To investigate the axial compression behavior of a new type of H-shaped composite columns with UHPC-filled steel tube flanges and honeycombed steel webs (STUHCs), the finite element models of 21 STUHC specimens are established by ABAQUS based on the nonlinear theories and concrete damaged plasticity model. The rationality of the models is verified by comparing with the existing experiments, including load–displacement (N–Δ) curves and failure modes. On this basis, the failure mode of the specimens is obtained, and the effects of seven key parameters on the ultimate bearing capacity (N_u), ductility (μ), and initial stiffness (K) are systematically investigated, and the force mechanism is revealed. The results indicate that the failure mode of the specimens is categorized into shear failure with local bulging at the middle section. The N_u increases significantly with the increase of yield strength of steel tube (f_yk) and cube compressive strength of UHPC (f_cu). The increase of constraint effect coefficient (ξ) can effectively improve μ, but the influence of thickness of steel web (t₂) on N_u, μ, and K is not obvious. Moreover, the load–average strain curves of STUHCs can be divided into four stages: the elastic stage, the elastic–plastic stage, the load-drop stage, and the residual deformation stage. The interface between UHPC and the steel tubes is well bonded, and an effective constraint-support cooperative working mechanism is formed. Finally, based on the calculation theory of lattice CFST composite columns, a calculation formula for the axial compression bearing capacity of this kind of STUHCs is established by statistical regression, which can provide a theoretical basis for the application of this new composite columns in practical engineering.