Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering ConferenceShanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Experimental Study on Non-Linear Wave Loads of a Ship Modelwith Variable Cross-section Backbone in Irregular Waves
Ziwen Zhang1,2,3, Ning Ma1,2,3, Yuan Lin4, Xiechong Gu1,2,3, Qiqi Shi1,2,3
1. State Key Laboratory of Ocean Engineering, Shanghai, China;
2. School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai, China;
3. Institute of Marine Equipment, Shanghai Jiao Tong University, Shanghai, China;
4. Jiangnan Shipyard (Group) Company Limited, Shanghai, China
Shanghai, China

happens when the encounter frequency is several times as natural
frequency. When slamming happens, the transient pressure on the ship
hull may lead to local and global effects. According to the definition byFaltinsen (2005), the global effect is so-called whipping. In a word,
springing is regarded as steady resonant motion, while whipping is a 2node vibration
caused by transient slamming pressure.
So far, many efficient experimental and numerical methods have beendeveloped to simulate hydro-elastic phenomena. Among them, thesegmented model test is considered a valid way to study wave loads andimpact forces. In the aspect of testing ship models (ITTC, 2017; ITTC,2021), both segmented and non-segmented testing models are kept
developing in recent years. Segmented models with backbones weredescribed by Maron and Kapsenberg (2014), Jiao et al. (2016), Houtaniet al. (2018) described a non-segmented flexible container ship model
without backbones where the vertical bending and torsional vibration
modes are replicated. Jiao et al. (2017) developed a tank testing system
to simulate ship motions and loads in a real sea state. As to springing andwhipping responses, the previous research mainly paid attention to thevertical bending in head waves (Ding et al. 2015, etc.). In recent years,
there is also an increased focus on oblique wave impact.
In this paper, an experimental study on wave loads and hydro-elastic
responses of a very large container ship has been described. A 1:64
segmented ship model of a 10000 TEU very large container ship withvariable cross-sections backbone was designed to meet elastic similarity
conditions of vertical, horizontal and torsional stiffness at the same time,and stiffness can be varied along the ship length to simulate the realsituation of real ships. Powered by the arrangement method of a series ofsensors, vertical bending moments, horizontal bending moments, torsion
moments, and vertical shear forces were recorded and analyzed
independently in time series. Both head wave and oblique wave
conditions were adopted in irregular wave tests, and the influence of
three different loading conditions was taken into consideration. Impact

ABSTRACTThis paper presents an experimental study on wave loads and hydroelastic responses of a very large container ship in irregular waves. A
segmented ship model with variable cross-sections backbone is newly
designed to meet similarity conditions of vertical, horizontal andtorsional stiffness at the same time, and stiffness can be varied
lengthwise. Both head wave and oblique wave are adopted in irregularwave tests. High-frequency wave loads, which have a significant effecton the springing phenomenon, are found in both head wave and oblique
wave test conditions through frequency spectrum analysis and accountfor the larger proportion in oblique waves. The non-linear wave-induced
sag/hog ratio of vertical bending moments may also result from the highfrequency component. Bow flare slamming is most important to the10000 TEU container ship in full load condition, while the stern and stem
slamming become more significant when the draft gets smaller. Stiffness
seems to have little impact on the frequency of slamming occurrence.
However, the mean slamming pressure and loads caused by slamming ismuch more severe when the stiffness decreases.

KEY WORDS: Springing; whipping; wave loads; asymmetricslamming; segmented ship model
INTRODUCTION
With the enlargement tendency of container ships in recent years, therelative stiffness of container ships has become weaker, resulting in moresignificant wave-induced vibration and non-linear springing/whipping
phenomena, which should be paid more attention to. As stiffness isreduced, the natural frequency has become closer to the encounterfrequency, resulting in linear springing. Meanwhile, nonlinear springing

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