Experimental study on shallow H-shaped steel column under combined loading condition

Abstract

When moment-resisting frames resist the horizontal forces, the columns are subjected to axial force with bending moment (i.e., under combined loading conditions). The lateral-torsional buckling shall be considered when the H-shaped steel columns are subjected to major axis bending. The collapse modes that will dominate the H-shaped steel column capacity are in-plane instability (caused by Pδ effects), out-of-plane instability (i.e., lateral-torsional buckling: LTB), and local buckling. If the column is expected to form a plastic hinge, that column shall guarantee sufficient ductility to prevent the building collapse. Moreover, the collapse mode that will determine the ultimate limit state should be informed. In the previous study, structural performances of the steel column were evaluated; however, the classification of the collapse modes was not studied sufficiently due to the limit of image recording equipment. Moreover, the structural behaviour reported in the previous study was based on monotonic loading, and the observed results from the cyclic loading were not sufficiently gathered. Cyclic loading may significantly impact the in-elastic behaviour of the H-section section column due to the potential of LTB. The difference in loading sequence must be clarified when the design rules are compiled. In this paper, the test results of different axial force ratios and lengths of members are reported. Sets of specimens are prepared for direct comparison of the loading sequence differences. The difference of collapse modes and the influence on the structural performances (such as max bending moment and plastic deformation capacity) is shown. Finally, comparing the monotonic and cyclic loading condition results, the effect of loading condition on the structural performances are also shown with the derived evaluation formula.