INVESTIGATION ON THE FATIGUE RELIABILITY OF OFFSHORE PLATFORMS

The objective of structural codes is to guide the proper design and construction of offshore platforms meeting functionality, safety and economical aspects. They are closely connected toeach other and an iterative procedure is necessary to achieve an optimal design. The consequences of failure concern the safety of humans, pollution, and the cost of structures and equipment. Therefore, the assessment of the safety of offshore platforms including jack-upplatform become essential. Time-varying nature of environmental loads such as wave and wind will cause fluctuation ofstresses in structural components of platforms. The fatigue damage is a deterioration process,which arises from fluctuation of stress, and should be evaluated before reaching a critical level.Traditionally, fatigue has not been considered as an important problem in jack-up platforms. The main reason was the most platforms were designed in areas with low or moderate environment conditions. Recently, by using jack-up platforms in regions with more severe sea states or aspermanent platforms, the fatigue damage becomes an important factor in evaluating the integrity and safety of the structures [1]. The present study investigates one of important aspect that influence on the fatigue reliability of offshore platforms. It is the bending to membrane stress ratio that can change by far fatigue reliability index.

Keywords:

Fatigue , Reliability , Jack-up , Bending to membrane stress ratio