System Reliability of Ship Hull Structures Under Corrosion and Fatigue

Abstract

System reliability of ship hull girder structures is evaluated considering uncertainties in ultimate bending capacity and sea loads. Lifetime structural deterioration models are developed at the system level. Time-variant random functions associated with corrosion and fatigue cracking are formulated to estimate the ultimate bending moment capacity. Still water and wave-induced bending moments are computed by using design-oriented and simplified direct methods. For sagging and hogging moments, structural performance in the intact hull condition is investigated considering different sea states as well as different ship operating speeds. The approach proposed is illustrated on a ship hull girder structure.

Risk-informed life-cycle optimum inspection and maintenance of ship structures considering corrosion and fatigue

“…(11)) equals 3 and the annual ship operation rate is 0.75 (Kwon and Frangopol, 2012). The fatigue scenario and parameters (e.g., stress intensity factor) associated with fatigue crack analysis for this specific ship are based on the work that has been done by the second author of this paper (Kwon and Frangopol, 2012). The similar approach has also been used by Kwon and Frangopol (2012) and Akpan et al (2002).…”

“…For the specific ship considered in this illustrative example, the material constant (i.e., m in Eq. (11)) equals 3 and the annual ship operation rate is 0.75 (Kwon and Frangopol, 2012). The fatigue scenario and parameters (e.g., stress intensity factor) associated with fatigue crack analysis for this specific ship are based on the work that has been done by the second author of this paper (Kwon and Frangopol, 2012).…”

“…For sagging and hogging conditions, the computed mean values of M sw are 3763 MN-m and 5371 MN-m, respectively. Within this illustrative example, the ship's wave load is obtained based on data presented in Kwon and Frangopol (2012). The expected wave load is 1161 MN-m for both sagging and hogging conditions.…”

“…Inspection and maintenance of aging ship structures are needed to ensure satisfactory structural performance during their life-cycle (Kim and Frangopol, 2012;Kwon et al, 2013;Zhu and Frangopol, 2013a;Zhu and Frangopol, 2013b). In general, the most significant strength deterioration mechanisms associated with ship structures are corrosion and fatigue (Guedes Soares and Garbatov, 1999;Kwon and Frangopol, 2012). Therefore, it is essential to mitigate the adverse consequences associated with structural failure under corrosion and fatigue.…”

Maintenance and safety of deteriorating systems: a life-cycle perspective

“…Polar representations of system reliability for different sea states and heading angles were presented. Additionally, an approach to account for the time-dependent corrosion and fatigue effects on the reliability of ship hull structures was provided in Kwon and Frangopol (2012).…”