Axial performance of UHPC-filled steel tube composite columns

This study presents a comprehensive finite element investigation into the axial compressive performance of Ultra High Performance Concrete-filled steel tube (UHPC-FST) composite columns. A numerical model is developed using ABAQUS, incorporating nonlinear constitutive models for both steel and UHPC materials. The model is validated using experimental data, demonstrating a strong correlation in terms of load-displacement behavior and ultimate strength. Extensive studies are conducted to evaluate the influence of key design parameters on the axial capacity of UHPC-FST columns. Increasing the steel yield strength from 450 MPa to 750 MPa led to a 1.21-fold increase in axial load capacity. Similarly, raising the UHPC compressive strength from 110 MPa to 190 MPa enhanced the capacity by approximately 1.43 times. A twofold increase in the thickness of the steel tube yielded a modest improvement of about 1.15 times. In contrast, changing the column diameter from 400 mm to 600 mm had the most significant effect, resulting in a 1.97-fold increase in axial capacity. The study also investigates the stress distribution, confirming that the UHPC core and steel shell act synergistically to delay local buckling and failure. The findings demonstrate the significant potential of UHPC-FST composite columns for high-performance structural applications and provide useful insights for future design guidelines.