The evolution of Navy ships is directed toward lighter and faster surface ships that are pushing the abilities of current structural design methods to ensure acceptable performance over the vessel's life. Wave loadings at high speeds result in pressure fields that challenge local and global structural integrity to a degree not supported by traditional Navy or commercial design approaches.This is particularly true of light-weight aluminum structures. The lack of knowledge results in either overly conservative, and thus, heavy designs or structural designs that pose a risk of failure over the life of the structure, resulting in reduced ship availability or mission failure. Current approaches do not include degradation of the material and structure due to environment. Such degradation can reduce strength by 10 percent or more and is not accounted for in current reliability or vulnerability assessments.
Development of a structural reliability-based toolset and decision criteria to ensure structural integrity of high-speed vessels over their lifetime will require development and maturation of global strength, local strength and fatigue strength prediction models, as well as seaway global and local loads models. Such an approach will need to account for material and structural degradation and availability of degradation and load effect data and information, particularly for real-time analysis as required for a structural health monitoring system.
Structural performance assessment of high-speed vessels is dependent upon knowledge of structural response to seaway loads of innovative ship structures at speeds beyond the operational experience of the Navy Technical Authority and Class Societies. Current knowledge is insufficient to assure acceptable structural failure risk mitigation over the life of the ship and provide for an efficient, light-weight structure. Structural response of light-weight, advanced structure to these loads (strength, deflection, fatigue) will be studied to determine resistance to the effects of secondary pressures, or wave slap, and primary bending loads. Decision criteria will be developed based on the probability of structural damage.
Current structural integrity models for metallic structures do not account for degradation over time. Development of new models that account for corrosion, material degradation (sensitization, fatigue cracking) and deformation are required for life prediction and life-cycle management of platform structures. These models will be developed given the available load information, material and structural condition (due to life degradation, production methods, repair methods) and will allow structural system performance prediction at any time during the platform life.