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earthquake loads. In the first stage of performance-based design, it is a key step to clarify and simplify
the target performance objectives from the views of protecting "human life", "properties contents" and
"structure function", etc. These demands are generally described by language, need to be transformed
into target performance objectives which structural engineers are familiar with. In the transformation
step, Fuzzy Set Theory is an effective and available tool.
In this paper, the characteristics of performance-based design are described. Because of clients' various
and particular demands, "individual" performance levels is determined by means of Fuzzy Set Theory.
Then, detailed criteria for the performance-based design of specific structure types and performance
levels are developed.
GENERALITY AKD INDIVIDUALITY
Performance-based earthquake-resistant design, which is the modern approach, makes an attempt to
predict structures with desired earthquake-resistant performances that are not only in agreement with
economic and social demands, but also satisfy particular ones from "building users" and "building
owners". Therefore, there should be two types of target performance levels, which reflect the
"generality" and "individuality" of the design, respectively.
"Generality" roots in the codes for earthquake-resistant design, and is described by means of a series
of design parameters, empirical code formulations, limit states, and some disciplines required. Its
objectives such as life safety and collapse prevention, both of which are hi agreement with the
economic and social demands, are used to define the state of every structure subjected to earthquake
load. Therefore, it is a target performance level that every earthquake-resistant structure must be
equipped with. In a word, "generality" is the compulsory performance level that every
earthquake-resistant structure must satisfy.
For "generality", to protect human life safety is the most important, and primary target performance
objective, which promises to produce every structure with desired mere earthquake-resistant
performance that is described by designating the maximum allowable damage state for an identified
seismic hazard. Hence, "generality" is the minimum performance level that every earthquake-resistant
structure must satisfy.
"Individuality" is a unique target performance level of an actual earthquake-resistant structure, which
promise a structure to satisfy some particular demands from "building users" and "building owners",
except for "generality". To emphasize "individuality" in earthquake-resistant design is to consider
particular demands for a structure. Therefore, a performance objective may be chosen in according
with damage states for several levels of seismic hazard, to assure not only "safety of human life",
"prevention of structure collapse', but also "preservation of property" and "maintenance of structure
function". Then, a dual or multiple-level performance objective would be adopted. It is clear that
"individuality" extend target performance level based on "generality", and is enhanced performance.
For an earthquake-resistant structure designed with performance-based design method, "individuality"