Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, 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

Research on lightweight design of multi-objective yacht structure based on Isight platform
Xingyu Liu1, Zhiyong Pei2, Wanyin Zhang1, Weiguo Wu2
1.Departments of Ocean Engineering, School of Naval Architecture, Ocean and Energy Power Engineering, Wuhan University of Technology,Wuhan, Hubei, China
2. Green & Smart River-Sea-Going Ship Cruise and Yacht Research Center, Wuhan University of Technology,Wuhan, Hubei, China

ABSTRACT.
Yacht structure optimization is an important pattern to achieve yacht
safety and lightweight design. Based on Isight platform, this paper
establishes the yacht structure optimization platform with the total
longitudinal strength and weight of the yacht as the optimization targets.
Firstly, parametric modeling was carried out for the hull. Then, thelongitudinal plate thickness and aggregate size of the target cabin weretaken as design variables, and the multi-objective optimization
algorithm NSGA-II was used for structural optimization on theoptimization platform. After optimization, the weight of the 212-footcabin is reduced by 4.96%, the maximum stress of the midship section
is reduced by 12.31%. The longitudinal strength of the ship is improvedby using less material, and the lightweight structure is realized.

KEY WORDS: Yacht; Structural optimization; NSGA–II;
longitudinal strength

INTRODUCTION
In the process of yacht structure design, designers mainly design thestructure form and layout of the yacht according to the specification
requirements. The structural performance of yacht determines thereliability and safety of yacht. The structural optimization can reduce
the weight and construction cost of yacht without affecting thelongitudinal strength of yacht. In addition, the use of less steel canimprove the structural performance of the hull is also a reflection of the
improved level of structural design (Shao, 2007).
Many scholars have carried out research and exploration in theoptimization of ship structure, and introduced intelligent optimization
algorithms represented by genetic algorithm, simulated annealing
algorithm, ant colony algorithm and particle swarm optimization
algorithm into the field of structural optimization. (He Xiaoer et al.
2013) introduced PSO into the optimization of complex ship structure,
realized the optimization of complex ship structure by PSO, andcompared with the results obtained by genetic algorithm, verified theeffectiveness of PSO in the optimization of complex ship structure. The
application of proxy model instead of time-consuming finite element
calculation reduces the time needed for optimization, but the validityof its results still needs to be verified by finite element.
In addition to the research expansion of optimization algorithm,optimization methods are also explored in order to reduce the numberof iterations and the calculation time (Han et al. 2021) analyzed thecharacteristics of the buckling utilization factor of double floor lattice,and proposed a fast optimization method suitable for the buckling
optimization of hull plate frame, which was applied to the structure
optimization of a tanker with double bottom. This method greatly
reduces the number of optimization iterations, but it has little reference
for practical engineering application to modify the thickness of eachslab. The research objects above are all part of the hull structure rather
than the whole ship, and the ultimate strength under various working
conditions is taken as the constraint condition.
At present, there are few researches on structural optimization of yachts,
mainly focusing on ultimate strength, and most of them are singleobjective structural optimization aiming at reducing quality (Yao 2015).
Some scholars reduce the weight of the boat by studying the use of newmaterials and topology optimization of the structure (Andric, J. et al2021). More scholars focus on the yacht's hydrodynamic performanceand improve the yacht's hydrodynamic performance by changing thestructural geometry model (Pawłusik, M. et al. 2020; Poloni, C. et al.
2000). Using ultimate strength as constraint can greatly reduce thequality of the structure, but also reduce the strength reserve of the yacht
resulting in a decrease in the safety of the yacht. The longitudinalstrength of the midship section is expressed by the minimum stress. A
multi-objective optimization process with the minimum mass and theminimum mid-ship profile stress as the objective function isestablished through Isight. The NSGA-II algorithm is adopted and theRules for Construction and Classification of Yachts (hereinafterreferred to as the rules) is used as the constraint conditions to optimize
the design and finally the optimization scheme is obtained.

LONGITUDINAL STRENGTH
The research object of this paper is a 212-foot yacht with a length of64.6m, a width of 11m, a depth of 7.2m, a design draft of 3.4m, aservice speed of 18kn, and an offshore class II sailing area. Consideringthat the use of standard method to check the yacht cannot truly express
the overall structure of the yacht and the load variation of eachcomponent. Direct calculation method and Smith's method are to3859