Abstract
In the recent years, interest has been expressed towards incorporating Structural Health Monitoring (SHM) systems to ship hulls in order to transition from preventive to predictive maintenance procedures. In this work, an initial approach is undertaken to investigate the capabilities of a model-based method treating damage identification as an optimization problem solved using a genetic algorithm. An idealization of the hull structure is considered based on hull girder theory that allows for lab scale experimental testing. Specifically, a box girder is considered with a circular discontinuity as the generalized damage that causes extensive stress redistribution, replicating the effect of hull damage modes of interest. A three-point bending load case is considered to emulate still water bending loads. Damage is considered to exist, and the goal of the proposed strategy is to provide a prediction on its location and magnitude (level 2 SHM). This is achieved using strain measurements obtained from sensors located on theoretical zero-strain directions as inputs to the optimization scheme treating the damage identification problem. Results from both assessment strategies highlighted the influence of measurement-related uncertainties on the method’s predictive capabilities.
Highlights
Maintenance procedures for ship structures are currently dictated by a set of rules and guidelines imposed by the International Maritime Organization (IMO), the International Association of Classification Societies (IACS) as well as individual classification societies
The above highlight that the integration of Structural Health Monitoring (SHM) systems for ship hulls can provide a viable solution to these shortcomings, something which is echoed
An idealized representation of the hull structure as a box-girder is theorized, following the example proposed by Anyfantis [9] and based on the principles of hull girder bending theory
Summary
Maintenance procedures for ship structures are currently dictated by a set of rules and guidelines imposed by the International Maritime Organization (IMO), the International Association of Classification Societies (IACS) as well as individual classification societies These are set around a strict schedule of visual inspections, known as surveys, where experts focus their attention on specific locations of the hull, which are considered susceptible to certain critical modes of damage [1]. To simulate still water sea-going and loading/ unloading (time invariant conditions) encountered during the ship’s operational life, a three-point bending load case is considered This choice enables an experimental assessment of the proposed SHM strategy, which utilizes an established combined FE-optimization scheme for damage identification [8], in which static strains are used as damage sensitive features, in the manner proposed by Preisler et al [10]. Assessment is first performed on modelbased input data and on data obtained from laboratory tests
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