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defined target. Performance-based seismic engineering is the best target available, and we need to
focus on it."
Now, five years later, the idealistic target has moved closer to reality. We still have a long way to go,
but we hope to have laid the groundwork, established a framework, and provided basic tools that make
PBEE realizable and an attractive alternative to conventional analysis and design. In particular,
significant progress has been made in establishing performance metrics and developing procedures for
a rigorous performance assessment that combine seismological, engineering, financial (e.g., $ losses)
and societal (e.g., life safety) considerations. This paper tries to summarize the approach developed by
PEER researchers for this purpose.
One concern needs to be expressed, and one notion needs to be dispelled, up front. The concern is that
the proposed approach relies heavily on the availability of seismological, engineering, and financial
data (e.g., construction costs after an earthquake). Much of the needed data is of questionable
reliability at this time. This is not a drawback of the approach, but points out an urgent need for data
acquisition and modeling. The notion to be dispelled is that the future will consist of complex
probabilistic approaches in routine structural design. This should be an option at the discretion of the
engineer or owner, but should not be necessary for routine designs. The main objectives of the
development is to
• Facilitate decision making on cost-effective risk management of the built environment in areas
of high seismicity
• Facilitate the implementation of performance-based design and evaluation by the engineering
profession, and
• Provide a foundation on which code writing bodies can base the development of performancebased
provisions.
The latter should result in relatively simple but more transparent and risk consistent provisions than are
contained in present codes and standards.
COMPONENTS OF PERFORMANCE ASSESSMENT APPROACH
This paper is concerned with performance assessment of buildings. The assumption is that all relevant
building systems, i.e., the soil/foundation/structure system as well as the nonstructural and content
systems, are given. The components of the performance assessment approach are summarized here (in
part from Cornell and Krawinkler, 2000) and illustrated in Fig. 1, and are elaborated on in later
sections.
By definition, PBEE is based on achieving desired performance targets. The latter are of concern to
society as a whole or to specific groups or individual owners. Performance targets are of the type
expressed in the first column of Fig. 1. The metrics of specific interest in the PEER research are life
safety, dollar losses, and downtime (or loss of function), and it is postulated that a performance target
can be expressed in terms of a quantifiable entity and, for instance, its annual probability of
exceedance. The quantifiable entities on which performance assessment is based, are referred to as
Decision Variables, DVs. For instance, X s (y), the mean annual frequency 1 (MAP) of the loss
exceeding y dollars, could be the basis for a performance target. Alternatively, a performance target
could be that the expected annual loss should be less than x dollars. In the assessment methodology
1 The MAP is approximately equal to the annual probability for the small values of interest here.