Structural Reliability of Monopods Under Storm Overload

Abstract

The structural reliability of a generic caisson under storm overload is investigated using typical Australian North West Shelf (NWS) environmental data. The bending moment due to the hydrodynamic loading is shown to increase in proportion to the fourth power of the wave height in certain critical cases, rather than the more usual exponent of α≈2. Combined with the steep wave height return period curve on the NWS, this may lead to low structural reliability, as much as two orders of magnitude smaller than more typical structures in other locations. The wave height exponent α varies with water depth and environmental force type (e.g. shear or bending moment) and increases rapidly near water line. This nonproportional nature of the loading is not addressed in design codes of practice or in traditional pushover analysis.