RELIABILITY OF CORRODED STIFFENED PLATE SUBJECTED TO UNIAXIAL COMPRESSIVE LOADING

摘要

The work is focused on the reliability of corroded stiffened plates subjected to compressive uniaxial load based on theprogressive collapse approach as stipulated by the Common Structural Rules for Bulk Carriers and Oil Tankers, employingthe limit state design. Two different cases have been investigated. In the first model, the corrosion degradation led touniform thickness loss, whereas the mechanical properties were unchanged, as given in the Rules. In the second model,the plate thickness degradation was followed by mechanical properties reduction. The uncertainties related to themechanical properties, thicknesses, and initial imperfections of the corroded stiffened plate were taken into account.Several initial design solutions of stiffened plates, as well as different severity levels of corrosion degradation wereinvestigated. The results show that structural reliability significantly decreases with corrosion development, especiallywhen in addition to the initial imperfections and corrosion plate thickness reduction, corroded plate surface roughness andthe changes in the mechanical properties were considered. The uncertainties, their origins and confidence levels arediscussed. It was found that non-linear time-dependent corrosion degradation accounting not only for the thicknessreduction due to corrosion wastage but also the subsequent decrease of mechanical properties lead to a significant reductionin the reliability index. Additionally, it was defined that the reliability estimate is very sensitive to the uncertainties relatedto the initial thickness and the spread of corrosion degradation as a function of the time. Incorporating the probability ofcorrosion detection into the original reliability model introduces additional information about the validity of structuraldegradation that may lead to a higher beta reliability index estimate compared to the original model.