Civil Engineering Reference
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dynamic analysis curves for the wooden house with plywood shear-walls
and GWB interior fi nish; in the fi gure, individual incremental dynamic
analysis results, which correspond to selected and scaled ground motion
records, are shown with thin lines with grey colour in background, while the
median and 16th/84th percentile curves are shown with thick black lines
(solid line for the median and broken lines for the 16th/84th percentiles,
respectively). By generating a sample of the maximum inter-storey drift
ratio for the scenario (SA at 0.3 s is 0.698
g
), the maximum inter-storey drift
ratio is obtained as 0.0079 (minor damage) by taking the inverse of the
empirical cumulative probability distribution function or the fi tted lognor-
mal model. A scatter of the maximum inter-storey drift ratio for the given
SA at 0.3 s is highlighted in Fig. 1.8a.
By repeating the same analysis for all scenario earthquakes in a synthetic
catalogue, PSRA is performed for two wood-frame houses with different
shear-wall features: one is with plywood shear-walls and GWB interior
fi nish, while the other is with horizontal boards and GWB interior fi nish;
the former is more resistant against earthquake loading than the latter (see
White and Ventura, 2006, and Goda and Atkinson, 2011). These houses are
located at soft soil sites (
V
S30
200 m/s) in Vancouver. The obtained seismic
risk curves in terms of maximum inter-story drift ratio are compared in Fig.
1.8b. The results indicate that the maximum inter-storey drift ratio for the
house with horizontal boards is consistently greater than that for the house
with plywood shear-walls (which is expected). The difference between these
two curves can be interpreted as the benefi t that is derived from a stronger
lateral force resisting system. Moreover, it is noticed that the slope of the
seismic risk curve for the house with horizontal boards tends to become
fl atter, as the annual occurrence probability level becomes smaller (near 2
×
=
10
−4
); this is because the structural system gradually approaches its ulti-
mate capacity (i.e. near collapse).
1.4
Conclusions and future trends
PSHA is an essential tool for current earthquake engineering practices and
performance-based seismic design methodology. It addresses key uncertain-
ties in earthquake occurrence and ground motion, and provides fundamen-
tal information on earthquake hazard (i.e. occurrence time, location,
magnitude, wave propagation, site effects, and ground motion intensities).
The direct outputs from PSHA, such as uniform hazard spectra and seismic
hazard deaggreation, facilitate modern seismic design provisions and prac-
tices for buildings and infrastructure. Importantly, PSHA can be enhanced
by extending its model components (e.g. nonlinear site response analysis,
near-fault motions, and aftershock hazard), and can be incorporated into
more advanced earthquake engineering analyses, such as liquefaction-
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