Investigation the Pulse Period Effect on Seismic Damage Distribution Pattern in Special Steel Moment-Resisting Frame Structures

The damage distribution of the steel moment-resisting frame (SMRF) structures is greatly a function of the pulse period of earthquake. In addition of frequency content of earthquake, the deformation demand distribution pattern depends on the seismic intensity more. In this study, the effect of pulse period of near fault earthquakes on the damage index as inter-story drift demand distribution of SMRFs with special ductility is investigated for different performance levels, including Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP) limit states. For this purpose, the seismic response parameters of three SMRFs with special ductility and 3, 9 and 15-story under the effect of 30 near fault earthquake records with different frequency characteristics are evaluated through the implementation of Incremental Dynamic Analysis (IDA). To study the effect of pulse period, the pulse-like near fault records are categorized into three groups of short, medium, and long-period records. Moreover, two numerical variables are defined to quantitatively describe the seismic demand distribution patterns over the height of the sample frames. Based on the results of this study, it is found that the concentration of the damage distribution in the SMRFs for highly nonlinear state of the seismic response, transfers to the lower stories. However, for elastic and near-elastic zones, the short-period pulse-like excitations transmit the seismic demands toward the upper and mid stories.