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structural capacity (Panel 4 in Fig. 28.1). For an individual structure, the
assessed damage severity is described by the damage factor d, which is
defi ned by:
DD
DD
−
−
⎡
⎢
⎛
⎜
⎞
⎟
⎤
⎥
DY
δ =
max min
,
10
,
,
[28.12]
C
Y
where
D
D
is the seismic demand variable, and
D
Y
and
D
C
are the yield and
collapse capacity variables of a structure, respectively; these variables are
expressed in terms of maximum inter-story drift ratio and are treated as
random variables. The damage factor d corresponds to no seismic damage,
partial seismic damage, and complete seismic damage for d
=
0, 0 < d < 1,
and d
1, respectively.
The maximum inter-story drift ratio of conventional wood-frame houses
in Vancouver (i.e.
D
D
) is estimated by using probabilistic models developed
by Goda and Atkinson (2011). The structural models of the wood-frame
houses (UBC-SAWS models) are based on SAWS (Seismic Analysis of
Wood-frame Structures) by Folz and Filiatrault (2003) and were calibrated
by researchers at University of British Columbia (UBC) using quasi-static
and dynamic test results for typical wood-frame houses in Vancouver
(Ventura
et al.
, 2002; White and Ventura, 2006). There are four UBC-SAWS
models with different shear-wall characteristics: (i) House 1 has blocked
plywood/oriented strand board shear-walls with exterior stucco cladding
and gypsum wallboard interior fi nish; (ii) House 2 has blocked plywood/
oriented strand board shear-walls with gypsum wallboard interior fi nish;
(iii) House 3 has unblocked plywood/oriented strand board shear-walls with
gypsum wallboard interior fi nish; and (iv) House 4 has horizontal boards
with gypsum wallboard interior fi nish. These four models can be assigned
to individual houses by utilising information on the year of construction. In
this study, a house is classifi ed as House 1, House 2, House 3, and House 4,
if the year of construction is after 1996, from 1986 to 1995, from 1976 to
1985, and before 1975, respectively (Ventura
et al.
, 2005; note this classifi ca-
tion is approximate, as discussed in Goda
et al.
, 2011).
The prediction models of the maximum inter-story drift ratio were devel-
oped by conducting incremental dynamic analysis (Goda and Atkinson,
2011); an estimate of the maximum inter-story drift ratio can be generated
for a given value of spectral acceleration at 0.3 s. Note that the vibration
period of 0.3 s is in the middle of the fundamental vibration periods of
Houses 1 to 4 and spectral acceleration at 0.3 s was adopted as a seismic
intensity measure in incremental dynamic analysis. The distinct features of
the models include careful record selection and scaling based on the con-
ditional mean spectrum (CMS) (Baker, 2011) by considering complex
seismic hazard contributions from different earthquake sources in south-
western British Columbia (i.e. crustal events, in-slab events, and interface
=
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