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reflects the structure's usefulness, and particular demands for "building users"' and "building owners";
"generality" reflects universal and compulsory demands for the society. It is clear that if "generality" is
not satisfied, "individuality" will be not accepted.
FUZZY PERFORMANCE CRITERIA
In performance-based design method, "individuality" is paid more attention to. "Individuality" results
from various aspects of earthquake-resistant performances demands from "building users" and
"building owners". In accordance with clients' demands, engineers must determine design
earthquake-resistant performances of each particular structure, and then establish technical design
criteria and the design values corresponding to each performance level, as well as required structural
strength levels to satisfy the technical design targets. It is necessary to clarify and identify what level
of performance is required to meet each objective in the design stage.
Classify clients' demands
The ground motion uncertainty can be described by seismic hazard analysis. Consequently, to assure
structural target performance levels, each design criteria must be determined in according with clients'
demands for performances either in small earthquake (frequent occurrence), or in intermediate
earthquake, or in large earthquake (infrequent occurrence). Then, to classify clients' demands will help
us to make assessment to these demands.
For each identified probability of earthquake occurrence, the following aspects need to be known from
"building users" and "building owners":
(1) Severity of hazard to human life (safety of human life)
Select one of the following levels of injury: 1) no injury, 2) slight injury, 3) injury of fracture, 4)
serious injury, and 5) death; which should be the minimum performance that the structure should
provide.
(2) Extent of loss of property value
Select one of the following levels of loss: 1) no loss, 2) small loss, 3) middle loss, 4) large loss, and 5)
almost total loss can not be avoided; which is the state in which the property value in structure is
deemed to be preserved.
(3) Required function of structure
Select one of the following levels of function: 1) keep overall function, 2) keep main function and
nonstructural damage can not be avoided, 3) keep essential function and partial repair is necessary, 4)
keep limited function and can be used after repair, and 5) guarantee for life safety and it is necessary to