Abstract
The behavior of a steel tall building frame under a varying horizontal force was studied experimentally, using cruciform model frames which were fundamental element of inner portion of multi-bay multi-story frames. Test frames were made by welding beams and columns of mild steel wide flange sections. In order to investigate the effects of the axial forces existing in the columns a variety of magnitude were given for the vertical loads. The ratios of column height to the radius of gyration and the beam-to-column stiffness ratios were also varied. A varying horizontal force was applied to a frame model under a constant vertical load on the columns. The experimental and theoretical behavior show as a general characteristic that the restoring force of a frame is reduced by the vertical loads. A fairlly well agreement is seen between the experiment and the two kind of theories which both take care of strain-hardening effects. The experimental frame failure loads, some of which have been presented in the previous papers, are compared with the two kind of ultimate frame strength formulas and these effectiveness are discussed.
