Effects of Ground Motion Parameters and Cyclic Degradation Behavior on Collapse Response of Steel Moment-Resisting Frames

This paper examines the collapse response of Japanese low- and medium-rise steel moment-resisting frames, which may suffer stiffness degradation and strength deterioration after column buckling in severe earthquake shaking. The ground motions used were artificial accelerograms with an identical Fourier amplitude spectrum. The maximum scale for artificial accelerograms not to collapse the systems and the corresponding energy-based velocities were investigated. This study has confirmed that far-field ground motions induced smaller plastic deformations when compared to near-field ground motions, thereby allowing the systems to absorb more energy before collapse. The results from comparing the scale indicated that in moderate degradation the maximum intensities for far-field ground motions not to collapse the systems were larger than those for near-field ground motions. This trend increased with intensive degradation but reversed with slight degradation. Moderate degradation was selected to further validate the real records and damping effects. This study has provided an insight into the collapse response with respect to the type of earthquake wave and to the extent of structural degradation.