Objectives In this study, a lightweight design method and optimal vehicle deck structure design scheme are proposed for a Ro-Ro ship based on the most hazardous working conditions under special vehicle load characteristics.

Methods First, the hazardous working conditions of the vehicle deck under special vehicle loads are obtained by direct finite element calculation and parametric modeling. Second, based on the mixed-integer sequence quadratic programming algorithm, a lightweight design method for a vehicle deck structure that satisfies local strength is proposed. Finally, the optimal design scheme for the vehicle deck structure under the most dangerous loading conditions is obtained.

Results The proposed optimal design scheme reduces the weight by 25.88% compared with the initial scheme, while the number of fatigue life cycles of the vehicle deck is 87 096 and the local strength stability and fatigue strength meet the specification requirements.

Conclusions The results of this study show that the reasonable arrangement of vehicles can significantly reduce the structural stress level of the vehicle deck, and the optimization of deck plate thickness is the most effective solution for reducing its weight. The proposed lightweight design method can provide useful references for the optimal design of vehicle decks for the same type of Ro-Ro ship.