Comparing the Robustness of Offshore Structures with Marine Deteriorations — A Fuzzy Approach

Abstract

The safety of offshore structures is highly dependent on the marine environment, where the latter could result damages to the structures through the deterioration process. A realistic analysis of the offshore structural performance with marine deteriorations is a challenging task. The traditional probabilistic model is sometimes too biased and could lead to undesirable results since the available information regarding the corrosion process is usually quite imprecise and uncertain. In this paper, the robustness assessment of offshore structures with consideration of corrosion effect is investigated through the fuzzy concept. The fuzzy model is introduced to quantify the thickness reduction associated with the corrosion process. The uncertainty regarding the time varying effect of the ultimate strength is analyzed in the computation to reflect the structural deterioration process. The concept of entropy is used to measure the degree of uncertainties in the input and output of a structural model in the robustness assessment. In order to demonstrate this innovation, this paper selects several similar structural models and compares their performances for the same level of damage imprecision. The results are also compared to the traditional probabilistic assessment methods and the experimental models in the literature. The advantage of applying this concept is shown in the results for comparing the performances of different structural systems with various intensities of imprecision in the input parameter. The comparison also demonstrates different cases while the corrosion process is extended to longer period.