Finite element simulation and parametric study of exposed column base plate connections under axial compression and Bi-directional lateral loading

This study numerically investigates the structural performance of exposed steel column base plate (CBP) connections subjected to combined axial compression and bi-directional lateral loading. Unlike traditional approaches that primarily consider uniaxial forces, this research addresses the combined impact of multi-directional forces, which more accurately represent seismic loading conditions. The research employs a comprehensive methodology that integrates experimentally validated finite element analysis (FEA) using ABAQUS. Laboratory tests were conducted on four CBP specimens with varying base plate thicknesses, bolt layouts, and grout thicknesses to capture critical failure modes and hysteretic behavior, in a companion study. The FEA models, validated against those experimental results, successfully simulate the non-linear moment-rotation response, pinching effects, and stiffness degradation under cyclic loading. Parametric studies are performed to explore the influence of key design variables, including axial load magnitude, base plate thickness, anchor bolt layout, bolt diameter, and grout properties. The results reveal that higher axial loads enhance moment capacity but reduce ductility, while bolt layout and diameter significantly influence energy dissipation capacity and failure mechanisms. This research highlights the differences in connection stiffness under unidirectional and bidirectional lateral loading and their impact on the behavior and response of CBP connections. The findings provide a foundation for improving design codes and optimizing the seismic performance of steel-framed structures.