On the Vertical seismic Response of the Floor Mounted Motorized Non-Structural Components

Seismic design guidelines for non-structural components typically do not account for the potential interaction between the vibrations of these elements and the deflections of the host structure, especially in the vertical direction. This paperexamines critical seismic scenarios, such as the simultaneous vibrations from operating motorized devices (like chillers) and earthquake-induced movements, by considering the short-period spectral characteristics of vertical ground motioncomponents in near-fault regions. To address this, the amplification factor of non-structural components installed in low-rise and mid-rise steel moment-resisting frame structures was assessed using nonlinear time history analysis. The evaluation showed that the amplification factor of vertical acceleration for non-structural components with vertical mode periods below ۰.۵ seconds ranged from ۱ to ۴, depending on the number of floors in the host structure and whether the motor was operational. The operation of the chiller's motor on the roof during an earthquake increased the vertical acceleration amplification factor by ۱۰% to ۵۰%. These findings suggest that the current seismic code approaches, which overlook the vertical mode frequency of structural and non-structural elements, need to be reconsidered, especially in near-fault areas.

Keywords:

Seismic vertical component , Non-Structural elements , operating motorized devices , Near-Field Earthquakes