English

Abstract

SUMMARY As modern container carriers become larger, certain parts of the existing prescriptive rules may pose increased uncertainty due to a lack of service experience. For example, questions concerning the envelope of wave-induced saghog moments may be raised as to whether the nonlinear effects due to the hull form or forward speed are properly reflected. The direct calculation methods are often used by ship designers to apply the ship motion and sea loads calculated from nonlinear seakeeping theory, then the finite element structural analysis is carried out to assess the structural integrity of the vessel. Although many advances have been made in the nonlinear hydrodynamic tools used for design reviews of the large container carriers, systematic validation of the wave loads and structural performance of these vessels in real operational conditions have not been reported. A comprehensive full-scale measurement system was developed to measure the wave environment, ship motions and structural loads. The complete system consists of the hull stress monitoring system, onboard wave monitoring system and voyage optimization system. The hull stress monitoring system employs ten long base strain gauges to measure the hull girder bending moments and torsional moment. The onboard wave monitoring system, which is based on the X-band radar signal, is used to monitor and display the significant wave height, periods and direction. Data from the vessel operation and navigation are obtained from the onboard voyage optimization system. The system was installed on an 8063 TEU container carrier in 2006, and the measurement campaign is currently underway. This paper presents the design of the onboard measurement system, installation and testing of the system. A description of the methodology to derive the torsional moment from the strain gauge signals is also included.