Abstract
The inelastic dynamic analysis of one-story single-bay unbraced and braced steel space frames with H-shaped columns is performed. The frame is idealized as a three-degree-of-freedom system with rigid floor and beams, and subjected to one-directional or two-directioal excitation. Sinusoidal waves are selected for the base acceleration. The restoring force of the column can be obtained by the numerical analysis shown in the previous paper (part 1), in which the deformable portion of the column is assumed to be concentrated near the ends. The restoring force of the brace is determined by the formulae presented by others. Results of the analysis are as follows : (1) The maximum responses of the frame under the two-directional excitation generally agree with those under the one-directional excitation, if the slenderness ratio and the axial force of columns are both small. The horizontal displacement responses about the weak axis in some of the unbraced frames increase with increasing slenderness ratio and axial force, although those frames are still stable under the one-directional excitation. (2) In some cases of the braced frames under the two-directional excitation, the increase in the rotation angle as well as in the horizontal displacements are observed. (3) In the case of an unbraced frame with H-shaped columns being arranged to have identical stiffness and strength in both directions, the responses are stable.
