Civil Engineering Reference
In-Depth Information
where
im
=
intensity measure (e.g spectral acceleration, duration, etc.);
dm
=
damage measure (e.g. physical condition and consequences/ramifi ca-
tions);
edp
engineering demand parameters (e.g. peak/residual drift ratio,
acceleration, local indices, etc.);
dv
=
=
decision variable (e.g. loss, functional-
ity, downtime, casualties, etc.);
mean annual frequency of occurrence
of a decision variable
dv
;
G
(
a
|
b
) is the conditional probability of exceed-
ance
a
λ
(dv)
=
a
0
given
b
. Each component of Equation (11.1) needs to be deter-
mined probabilistically. Currently, the method has been implemented in
ATC-58 (2011) and ATC-63 (FEMA_P-695 (2011)), and also in other coun-
tries. For instance, in China, PBD has been added to the new version of the
code 'Seismic Design for Building Structures' (GB50011-2010), to design
tall buildings and innovative systems, while the majority of buildings could
be designed with traditional response spectrum analysis.
There are several aspects that are not covered by the current PBD:
>
portfolio assessment;
community assessment.
The concept of PBD can be applied to describe the behaviour of a single
building or structure, but the performance of an individual structure is
governed not only by its own performance, but interacts extensively with
the performance of other entities within the same community. A clear
example of these interdependencies between the building and the com-
munity is a hospital, which will not be able to perform without electricity
and water even if the structure has no structural damage. Another example
of the limitations of PBD was demonstrated in the 2009 L'Aquila earth-
quake, during which the small town of Castelnuovo was completely
destroyed, except a single housing unit that was standing after the earth-
quake and suffered minor damage (Cimellaro
et al.
, 2010a). According to
PBD the building would satisfy the requirements, but in RBD, the housing
unit would not be operational, because it is not able to interact with other
entities inside the same community (e.g. a housing unit with minor struc-
tural damages without water, electric power and roads connecting it to the
rest of the world can satisfy the PBD requirements, but it will not satisfy
the RBD requirements). The reason for these limitations is because PBEE
in its original formulation was never intended to be applied at a community
level; rather, it was developed to permit engineers to better match the build-
ing performance to expectations of the owner or architect, which usually
require more than the fundamental goal of life safety.
11.3 Towards resilience-based design (RBD)
Nowadays, designers and engineers approach a structure as if it stands
alone, without considering the interaction with the community, which
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