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Seismic Behavior and Design of Deep, Slender Wide-Flange Structural Steel Beam-Columns



Piyachai Chansuk, Gulen Ozkula, Chia-Ming Uang, John Harris


Twenty-one W24 hot-rolled columns of ASTM A992 steel with five different sections were tested in Phase 1 of this research program to investigate the effects of slenderness parameters, constant axial load levels, lateral drift loading sequences, and weak-axis bending on the column base responses. It was observed that the webs of these sections with much larger ℎ/ �������� ratios were not as effective in restraining and delaying flange local buckling as those of shallow and stocky (e.g., W12 or W14) columns. Specimens with sections that satisfied the highly ductile requirement in the AISC Seismic Provisions still experienced significant damage and axial shortening due to the interactive flange and web local buckling. An "unusual" failure mode with local buckling coupled with lateral-torsional buckling was also observed for the first time. Based on these tests results, observed buckling modes were classified, and a simplified procedure to predict the governing buckling mode was proposed. Additional 23 columns including W14, W18, W24, and W30 sections were tested to further evaluate the effects of section depths, boundary conditions, and varying axial loads. Test results revealed that findings from Phase 1 testing could be extrapolated to deeper and shallower sections; the proposed procedure predicted very well the buckling mode of Phase 2 specimens. Allowing the column top end to rotate increased the story drift capacity but did not change the buckling mode. Results from varying axial load tests showed that first-story exterior columns behave very differently from the interior ones. W14 column test results showed that classifying a column as deep or shallow based on the nominal section depth may be inappropriate; the "deep column" phenomenon with significant interactive local buckling could develop in W14 columns with relatively slender web and flanges.
Technical Note (NIST TN) - 2169
Report Number


Steel, beam-column, seismic, full-scale testing


Chansuk, P. , Ozkula, G. , Uang, C. and Harris, J. (2021), Seismic Behavior and Design of Deep, Slender Wide-Flange Structural Steel Beam-Columns, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed June 23, 2024)


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Created July 28, 2021, Updated October 14, 2021