Alternative Design Philosophies for Achieving Target Safety Levels in Fixed Offshore Structures

This paper explores two alternative design philosophies for achieving target safety levels in fixed offshore structures. The first uses a Working Stress Design format, and examines the relationship between the return period of the metocean design criteria and the configured structural reliability. The second uses a Load and Resistance Factor Design format, and considers suitable environmental partial load factors required to achieve acceptable safety levels. An example case study of two unmanned structures demonstrates the importance of local environment and structural configuration in determining reliability. The results indicate that for certain combinations of structural configuration and environment, previously recommended design approaches appear inadequate. This study proposes more appropriate design criteria for two specific configurations on the North West Shelf of Australia.