Chapter10 Reliability Quantification of High-Speed Naval Vessels Based on SHM Data Mohamed Soliman and Dan M. Frangopol Abstract Identification of the structural responses of high-speed naval vessels under normal sea operation is subjected to uncertainties associated with the loading conditions, material properties, cross-sectional dimensions and damage propagation, among others. Probabilistic analyses provide appropriate performance indicators, such as the reliability index, which can simultaneously consider these uncertainties in the prediction of the service life of ships based on the required reliability levels. In this context, structural health monitoring (SHM) can aid in determining the seaway loading conditions and quantifying the structural responses under different operational conditions. As a result, uncertainties associated with the performance prediction can be quantified and some of them (i.e., epistemic uncertainties) can be reduced. In this paper, reliability assessment, based on SHM data, of high-speed naval vessels is performed. Information from SHM is used to estimate the actual structural response associated with the sea states, ship speeds, and wave headings encountered by the vessel. Recorded structural responses are used to establish the time-variant performance profile of the studied cross-sections. This profile can be used to predict the remaining service life and to plan for the appropriate threshold-based inspections and repair actions. The presented approach is applied to a high speed naval vessel. Keywords Structural health monitoring • Uncertainty • Naval vessel • Deterioration • Reliability 10.1 Introduction Evaluation of the performance of ships under normal operational conditions is usually a demanding task. This is mainly due to the presence of uncertainties associated with the sea loading conditions, material properties, and damage initiation and propagation, among others [1, 2]. This is especially true for high-speed aluminum vessels. In these ships, to comply with the speed and load requirements, the designers and manufacturers usually use innovative structural details whose behavior may not be fully understood [3]. As a result, more research is still needed for evaluating the structural performance of high-speed naval vessels. Aluminum naval vessels are subjected to various time-dependent structural deterioration mechanisms such as fatigue and corrosion [4]. Fatigue is one of the most critical deteriorating mechanisms. It occurs at locations with high stress concentration or fabrication defects. Stress fluctuations at these locations during ship operation may cause cracks to initiate and propagate. These cracks, if not inspected and repaired in a timely manner, may cause fracture of the affected components and may lead to catastrophic failures. Corrosion losses, on the other hand, may cause reduction in the hull structural resistance, reduction in the local strength, and/or increase in the fatigue crack propagation rate within the damaged area. Aluminum vessels generally have high corrosion resistance due to the formation of a thin oxide layer which prevents any further corrosion to the core metal. However, aluminum is prone to galvanic corrosion if not properly isolated. Due to these deterioration effects, the structural performance degrades with time as shown in Fig. 10.1. Additionally, due to the aforementioned uncertainties, the predicted structural performance carries inherent uncertainty. Therefore, the performance assessment process must be handled probabilistically [5–7]. M. Soliman ( ) • D.M. Frangopol Department of Civil and Environmental Engineering, ATLSS Engineering Research Center, Lehigh University, 117 ATLSS Drive, Bethlehem, PA 18015-4729, USA e-mail: mos209@lehigh.edu; dan.frangopol@lehigh.edu H.S. Atamturktur et al. (eds.), Model Validation and Uncertainty Quantification, Volume 3: Proceedings of the 32nd IMAC, A Conference and Exposition on Structural Dynamics, 2014, Conference Proceedings of the Society for Experimental Mechanics Series, DOI 10.1007/978-3-319-04552-8__10, © The Society for Experimental Mechanics, Inc. 2014 99
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