A method for measurement of global loads on a vessel, using strain measurements from a network of strain sensors and extensive Žnite-element analyses (FEA) with idealistic load cases, is presented. The sensors are attached at carefully selected locations at a cross section amidships, where the most signiŽcant loads have their maximum values. The Žnite-element (FE) strain values are used in precalculations to reduce the computational effort to solve a set of linear algebraic equations in real time. The method has been successfully tried out on the full-scale surface effect ship (SES) KNM Skjold (47 m, 270 tons, and 50 knots) instrumented with a network of Žber optic Bragg strain sensors. The seakeeping tests were performed in the North Sea (1999) in sea states 3, 5, and upper 6. Other parameters that were varied during the test program were the heading, forward speed, and on/off-cushion. The loads measured during the tests were the sagging/hogging moment, the horizontal bending moment, and the longitudinal twisting moment. The measured loads were compared with respective dimensioning loads based on DNV rules (HSLC) (1996). The results showed that when the vessel is subjected to bow flare slamming impacts, the sagging moment exceeded the DNV dimensioning value by a factor of 1.6, indicating that the HSLC rules do not provide conservative global loads when these extreme events occur. However, the peak loads were well within the design limits.

Keywords:
longitudinal, load case, downhole sensor, sea state, strain response, strain value, vertical shear force, forward speed, shear force, Completion Monitoring Systems/Intelligent Wells
Subjects:
Completion Monitoring Systems/Intelligent Wells, Downhole sensors & control equipment, Information Management and Systems, Well Monitoring Systems/Intelligent Wells
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2001. The Society of Naval Architects and Marine Engineers
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