Effect of Column Base Fixity on the Compressive Strength of Axially Loaded Steel Columns

This study investigates the influence of rotational stiffness of column base connections on the axial compression strength of steel columns. Utilizing recently validated models to estimate the rotational stiffness of exposed column base connections, a series of 792 axially loaded columns were analyzed. The analysis incorporated a wide range of variables, including column cross-sections, slenderness ratios, boundary conditions, and commonly used base connection details. The coupling between base rotational fixity and applied load was resolved to calculate column strength. Results show that column strength, determined using realistic rotational stiffness values, can be up to twice as high as estimates based on pinned base assumptions and closely approaches values derived from fixed-base assumptions. This effect arises because, under pure axial loading, base plate stiffness is governed by footing deformations rather than anchor elongation or base plate bending, leading to high stiffness. The impact of column configuration on these findings was modest. The results suggest that incorporating accurate base stiffness in axial force design may significantly reduce conservatism, which is particularly beneficial for adaptive reuse scenarios in existing buildings. Limitations of the study are discussed.