A Risk-Informed Approach to Performance Assurance - Structural Integrity of Offshore Wind Turbines - page 72

member-based; any treatment of system effects is hidden in the member
safety-checking equations in the form of effective length factors, strength
or ductility factors, and similar simplifications of complex structural sys-
tem behavior.
TRANSITION FROM PRESCRIPTIVE
TO PERFORMANCE-BASED REGULATIONS
The performance of civil infrastructure systems, unlike that of many other
common mass-produced engineered (for example, automotive and avia-
tion) systems, is governed by codes, standards, and regulatory guidelines
that represent judgments by the professional engineering community
based on experience. These documents are key tools for structural engi-
neers in managing civil infrastructure risk in the public interest, and the
traditional structural design criteria they contain address the risks in struc-
tural performance as engineers have historically understood them. For the
most part, these criteria have been based on judgment. This approach
to performance assurance generally has served society reasonably well
because construction technology has evolved slowly. As in the case of civil
infrastructure, the design and construction of marine vessels date back
thousands of years, and the development of design codes, standards, and
practices has been gradual and deliberate. Historically, these regulations
have been prescriptive, consisting of detailed, experience-based require-
ments and formulations that must be satisfied to prove compliance.
In recent years, however, innovation in technology has occurred rapidly,
leaving less opportunity for learning through trial and error. New tech-
nologies have taken form not only in new concepts, materials, and manu-
facturing techniques but also through more sophisticated analysis and
optimization tools that enable the design of more efficient structures. The
public furor caused by recent disasters has made it clear that approaches
to risk management based on judgment may not be acceptable and are dif-
ficult to justify after the fact. Standards for public health, safety, and envi-
ronmental protection now are often debated in the public arena, and
societal expectations of facility performance have increased.
Over the past several decades, regulations pertinent to the civil
and marine industries have begun shifting from empirical or prescrip-
tive formula-based (experienced-based) to performance-based (goal-