University of Qom Civil Infrastructure Researches 2783-140X Articles in Press 2026 02 17 Investigation of Structural Behavior in Base Plate Connections of Cruci-form-Shaped CFST Columns under Cyclic Loading Investigation of Structural Behavior in Base Plate Connections of Cruci-form-Shaped CFST Columns under Cyclic Loading 4211 10.22091/cer.2026.14489.1664 FA Sepideh Rahimi Department of Civil Engineering, No.C., Islamic Azad University, Noor, Iran 0000-0002-5194-8841 Journal Article 2025 11 12 Base plate connections are critical elements in structural systems, ensuring reliable load transfer and stability under lateral and seismic actions. In cruciform concrete-filled steel tubular (CFST) columns, the combined interaction of steel and concrete, along with the geometric complexity of the section, makes their design and analysis particularly demanding. This study presents a parametric investigation of the seismic behavior of base plate connections in cruciform CFST columns under cyclic loading. A finite element model was developed in Abaqus, incorporating nonlinear material properties, slip contact interactions, and explicit modeling of anchor bolts and steel–concrete interfaces. Three parameters were examined: base plate thickness (30–50 mm), anchor bolt diameter (20–30 mm), and axial load level. Overall, the findings highlight that base plate thickness is the most influential parameter for stiffness and strength enhancement, anchor bolt diameter primarily improves energy absorption and damping, and axial load ratio contributes to confinement and cyclic stability. The optimized combination of parameters is recommended to achieve superior seismic performance of CFST base connections with nonstandard geometries. Base plate connections are critical elements in structural systems, ensuring reliable load transfer and stability under lateral and seismic actions. In cruciform concrete-filled steel tubular (CFST) columns, the combined interaction of steel and concrete, along with the geometric complexity of the section, makes their design and analysis particularly demanding. This study presents a parametric investigation of the seismic behavior of base plate connections in cruciform CFST columns under cyclic loading. A finite element model was developed in Abaqus, incorporating nonlinear material properties, slip contact interactions, and explicit modeling of anchor bolts and steel–concrete interfaces. Three parameters were examined: base plate thickness (30–50 mm), anchor bolt diameter (20–30 mm), and axial load level. Overall, the findings highlight that base plate thickness is the most influential parameter for stiffness and strength enhancement, anchor bolt diameter primarily improves energy absorption and damping, and axial load ratio contributes to confinement and cyclic stability. The optimized combination of parameters is recommended to achieve superior seismic performance of CFST base connections with nonstandard geometries.