Numerical Analysis and Resistance Design of UHPC- and UHTCC-Encased Rectangular Steel Tubular Columns Subject to Axial Compression

Ultra-high performance concrete (UHPC) and ultra-high toughness cementitious composite (UHTCC) offer superior mechanical properties compared to normal concrete, with UHPC excelling in compressive strength and UHTCC in tensile ductility and crack resistance. This study focuses on UHPC/UHTCC-encased steel tubular (UEST) columns, establishing finite element (FE) models to simulate the axial behavior of UEST columns, conducting parametric studies on stud number, encasement thickness, steel yield strength, and width-to-thickness ratio, and developing a theoretical model considering thin-walled steel buckling to calculate the axial resistance of UEST columns. The proposed theoretical model predicts axial resistance with an average error of 3.4%, providing a reliable design method for engineering applications.