Study on the Method of the Design Loads for Ultra Large Container Ship
- Siyu Wang (Harbin Engineering University) | Hui Li (Harbin Engineering University) | Kaihong Zhang (Harbin Engineering University) | Hexing Song (Harbin Engineering University) | Zheng Yang (Harbin Engineering University)
- Document ID
- International Society of Offshore and Polar Engineers
- The 28th International Ocean and Polar Engineering Conference, 10-15 June, Sapporo, Japan
- Publication Date
- Document Type
- Conference Paper
- 2018. International Society of Offshore and Polar Engineers
- indirect time-domain, nonlinear, Hydroelasticity, design loads
- 0 in the last 30 days
- 10 since 2007
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Large container ships have very flexible hulls resulting in low natural frequencies, causing the hull vibrations stimulated more easily when sailing. So the elastic effect of wave loads is obvious. And because of the large flare of bow, slamming occurs frequently. Hence, the non-linear effect of wave loads is significant. An indirect time domain method based on 3D nonlinear hydroelastic theory is used to calculate the design loads, which includes the nonlinear and elastic effect. The method is applied to the calculation of a 21,000 TEU ultra large container ship, and the results are compared with that obtained by the method of UR S11A given by IACS and linear frequency domain. Then, the characteristics of the design loads are analyzed. And based on the results, the sea conditions that influence the design load most are filtered.
The coupling effect between elastic deformation of hull and fluid has drawn the people’s attention because large container ships have very flexible hull with enlargement of principal dimension and high strength steel is widely used in recent years. The nonlinearity load is more obvious generated from the slamming phenomenon in severe sea condition. In addition, it is appalling that the container ship, MOL Comfort, suffered a crack amidships in severe weather about 200 nautical miles off the coast of Yemen and eventually broke into two pieces after hogging in 2013. Hence, the design loads of large container ships is very important to guide the ship structural design. However, the relevant classification society rules about elasticity and the nonlinear loads is not yet considered completely, and the applicability of the rules for ultra large container ship is not yet clear. It is necessary to study the design loads for ultra large container ship.
The classical approach to determine ship motions and wave loads is based on the assumption that the ship hull acts as a rigid body. However, the approach is not reliable enough for ultra large ships due to interaction between the wave load and structure response. Bishop and Price (1979) establish the hydroelastic theory based on the unified strip-beam theory. The ship hull is simplified as a beam Timoshenko beam and the fluid force is determined by the strip theory. With the improvement of the hydroelastic theory, the wave-induced loads determined by a 3D potential theory is imposed to the elastic 3D structural models. Xia (1998) studied the wave loads of the ship based on the hydroelasticity theory in time domain. Chen (2003) developed a three-dimensional second-order hydroelasticity analysis program for mooring buoys. On the basis of this research, Tian (2006) further considers the influence of velocity and non-uniform steady-wave flow field on hydroelastic response. With the development of computer, three-dimensional nonlinear hydroelastic method has entered a new stage.
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