Toppling of Rigid Electric Equipment during Earthquakes
Date
2018
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Article
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23 p.
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Abstract
This study presents a general formulation for toppling risk assessment of rigid
electrical equipment during earthquakes. The seismic response, toppling fragility
functions and toppling risk were examined for three types of support conditions,
namely: 1) equipment simply supported on the foundation; 2) equipment anchored
to the foundation; and 3) equipment supported on a seismic base isolator. Because
empirical fragility functions for overturning equipment remain insufficient, the
present study relies on numerical analysis and a solid physical background to
compute risk. These results should aid designers in the selection of appropriate
support conditions or mitigation measures for rigid electric equipment in seismic
prone regions.
As an example, the toppling risk methodology is presented using Mexican
seismicity and a set of nine electrical equipment commonly used throughout
Mexican power stations, with heights between 3 and 5 m, covering an ample range
of frequency parameters (1.54 < p < 2.16 rad/s), and block dimensions (1.58 m < R
< 2.49 m). Further, the effects of site-to-source distance for sites located on firm
soil are studied in detail, as the frequency content of these ground motions differ
significantly and play a key role in the toppling vulnerability of the blocks. The
study shows that the reliability index increases monotonically with increasing block
aspect ratio and block size for the nine equipment and the three support conditions
studied. This investigation also demonstrates that the reliability of free-standing
equipment due to near-source ground motions is slightly higher than that of
anchored equipment or base isolated equipment. In contrast, for far-field ground
motions, the reliability for anchored equipment is slightly higher than that of free-
standing or base isolated equipment.
Description
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Citation
Engineering Structures, 2018, v.168, 23 p.
Keywords
Toppling Risk, Rigid Electric Equipment