Advances in Seismic Design Methodologies - Earthquake Engineering for Structural Design - page 391

Advances in Seismic Design Methodologies 391

to the inhabitants of their facilities beyond the minimum required by the society
(Krawinkler, 1996, 1997).
“Performance-based seismic design implies design, evaluation and construction of
engineering facilities whose performance under different earthquake levels responds
to the diverse needs and objectives of owners, users and society” ( Krawinkler, 1999 ).
The new performance-based seismic design procedures intend to design structures
which perform at appropriate levels for all earthquakes. By defining various
performance levels, performance-based seismic design allows business interruption
losses after a seismic event to be controlled and, when appropriate, minimized. With
the development of this new methodology, building owners now have choices which
were never available before.
“Building owners can now tailor the performance of their structure to their
needs” (Poland and Hom, 1997).
For instance, hospitals, where the functionality of the facilities after a major seismic
event is more important than the actual structures, can use a performance basic level to
attain a higher performance level than the one for life safety. Production companies,
such hi-tech manufactures, as well as important banks, where the values of the business
is more important than the value of the buildings themselves, are able to design and
upgrade their facilities to maintain continued operations, even after a major earthquake.
In order to implement the performance based seismic design, it is necessary to select
the performance objectives. A performance objective is a simple statement of the
desired building behavior, giving that it experiences earthquake demands of specified
severity. The important parameters for owners and users include the potential loss of
life, the cost of repairing any sustained damage, as well as the amount of time during
which the building is out of service while it is repaired or, in extreme cases, replaced.
A most practical approach would seem to be the adoption of a limited series of
standard behavioral states, from which the design performance objectives could be
developed. The Vision 2000 projects (SEAOC, 1995, Hamburger, 1996) have
identified the following series of standard behavioral state definitions with the
appreciation of the service disruption time (Giuliano et al, 2004):
- Fully operational . Only very minor structural or non-structural damage occurred.
The building retains its original stiffness and strength. Non-structural components
operate and the building is available for normal use without any service
interruption. Repairs, if required, may be done at the convenience of the building
users. The risk of life threatening injury during the earthquake is negligible.
- Operational . Only minor structural damage occurred. The building structure
retains nearly its original stiffness and strength. Non-structural components are
secured and, if utilities are available, most of them would function. Life safety
systems are operational. Repairs may be done at the convenience of the building
users. The risk of life threatening injury during the earthquake is very low. The
service interruption is less than 3 days.