Drydock Service Life Cost Reduction by Use of Finite Element Analysis
Military Standard 1625 (SH) is currently the principal governing document for certification of floating drydocks which service US Navy ships. In order to maintain their certification, drydock owners must periodically document, evaluate, and repair corroded structural elements according to this standard's specifications. This evaluation and repair process is frequently cost‐prohibitive for some docks that have sustained significant corrosion. As an alternative, a finite element analysis (FEA) may be performed to isolate areas that require repair to maintain the safe operating capacity of the vessel. First, a finite element model of the drydock is created based on corrosion data from ultrasonic testing (UT). The corroded model is then analyzed to evaluate the global strength of the drydock and to isolate specific areas of corrosion that require repair. By isolating structurally critical areas, unnecessary repairs otherwise required, may be avoided. This process may result in considerable cost savings for drydock owners. In addition, wastage rates from historic ultrasonic survey data may be used to predict future corrosion. This paper will summarize the FEA conducted of the floating drydock ADEPT, a US Navy‐owned dock that is leased by Gulf Copper Ship Repair Inc. of Corpus Christi, TX. During the drydock's service life, significant corrosion has developed throughout the vessel's structure. Ultrasonic surveys were conducted to document the existing levels of corrosion and MAESTRO, a FEA program developed by Proteus Engineering, was used to develop a finite element model of the vessel based on the scantlings reported from the surveys. MAESTRO was then used to perform a FEA to isolate areas that require repair. Additionally, results from this analysis were used to calculate wastage rates and predict future corrosion. The FEA was then modified to analyze the future condition of the vessel in order to evaluate the need for future repairs.
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Document Type: Research Article
Publication date: October 1, 2008
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- The Naval Engineers Journal is the peer-reviewed journal of the American Society of Naval Engineers (ASNE). ASNE is the leading professional engineering society for engineers, scientists and allied professionals who conceive, design, develop, test, construct, outfit, operate and maintain complex naval and maritime ships, submarines and aircraft and their associated systems and subsystems.