DESIGN ENVIRONMENTAL CRITERIA--WHAT ARE THE CONSEQUENCES OF EXCEEDANCE?

It is standard practice in the offshore industry to design structures to withstand the loads imposed by site-specific environmental extremes that have a very low frequency of occurrence. Typically, extremes that have an average return period of once in 50 years are chosen. The selection of 50 years as the return period is somewhat arbitrary, and during the life of a structure there is a very low probability that it will, in fact, experience environmental conditions that exceed the design conditions, i.e. conditions that have a return period greater than once in 50 years. If a structure is exposed to the environment for 25 years, there is a 39 percent chance that it will experience the 50-year extremes during that exposure and a 22 percent chance that it will experience the 100- year extremes. These percentages are dependent on the laws of probability and are the same for all locations in the world. Therefore, all structures designed using the 50-year extreme environmental conditions have an equal probability of experiencing the 100-year extremes for any given exposure period. What is most certainly not the same for each location worldwide is the difference in environmental loadings between the 50-year and 100-year extremes. This paper expands on this topic and highlights those areas of the world where the potential problem is most serious.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/03093948
• Supplemental Notes:
  • Transactions paper
• Authors:
  • Lynagh, N
• Publication Date: 1990

Media Info

• Features: References;
• Pagination: 5 p.
• Serial:
  • Institute of Marine Engineers Transactions
  • Volume: 102
  • Issue Number: Part 3
  • ISSN: 0309-3948

Subject/Index Terms

• TRT Terms: Design; Environment; Oceans; Offshore platforms; Risk analysis; Storms; Weather
• Uncontrolled Terms: Design criteria; Marine environment
• Old TRIS Terms: Extreme waves; Wave loads on structures; Wind loads on structures
• Subject Areas: Bridges and other structures; Design; Marine Transportation;

Filing Info

• Accession Number: 00661601
• Record Type: Publication
• Source Agency: Maritime Technical Information Facility
• Files: TRIS
• Created Date: Jul 21 1994 12:00AM