Effect of Cross-Section Shape on Seismic Behavior of Moment Frames with CFT Columns under Near- and Far-Field Earthquakes

This study examines the effect of cross-sectional shape on the nonlinear seismic behavior of Concrete-Filled Tube (CFT) columns in moment-resisting steel frames subjected to near- and far-field earthquakes. Two-dimensional frames with varying heights were modeled using finite element analysis in ABAQUS, incorporating square, circular, and rectangular CFT columns. Nonlinear dynamic analysis was performed to evaluate seismic performance in terms of displacement, base shear, inter-story drift, and bending moment. Results show that circular CFT columns outperform others in low-rise frames, exhibiting up to 27% lower displacement and reduced drift under far-field earthquakes. In contrast, rectangular CFT columns demonstrate superior performance in mid- to high-rise frames, with up to 59% less displacement and 44% lower base shear under both near- and far-field conditions. Square sections consistently exhibited the poorest performance. Far-field earthquakes induced higher responses, with an average increase of 27-34% in bending moment. These findings underscore the critical influence of cross-sectional shape on optimizing the seismic design of CFT columns in moment frames for earthquake-prone regions.