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Xu D.,Shanghai JiaoTong University | Liu J.,Shanghai JiaoTong University | Liu S.-W.,China Offshore Technology Center
Chuan Bo Li Xue/Journal of Ship Mechanics

Impacts between ships and ice floes often result in high pressures, which require excessive structure reinforcement under elastic design. Although several limit load criteria to obtain limit load from load/deflection curve were proposed in other fields, there is no unanimously adopted limit load criterion in the shipbuilding industry. By using nonlinear FE analysis results of the side structure of an Arctic ship, different limit load criteria were compared and twice-elastic-slope method was determined to be the optimal limit load criterion for polar ships. Furthermore, the rationality of the twice-elastic-slope method was verified by the requirements of the ice class rules. This work can provide a reference for the selection of limit load criterion on strength assessment of polar ships and the findings are expected to contribute to the modification of the current ice class rules. Source

Ji S.,Dalian University of Technology | Di S.,Dalian University of Technology | Liu S.,China Offshore Technology Center
Engineering Computations (Swansea, Wales)

Purpose - In oil/gas exploitations of ice-covered cold regions, conical offshore structures are designed to reduce ice force and to avoid the ice-induced intense vibrations of vertical structures. The purpose of this paper is to investigate the interaction between ice cover and conical offshore structures, the discrete element method (DEM) is introduced to determine the dynamic ice loads under different structure parameters and ice conditions. Design/methodology/approach - The ice cover is dispersed into a series of bonded spherical elements with the parallel bonding model. The interaction between ice cover and conical offshore structure is obtained based on the DEM simulation. The influence of ice velocity on ice load is compared well with the experimental data of Hamburg Ship Model Basin. Moreover, the ice load on a conical platform in the Bohai Sea is also simulated. The ice loads on its upward and downward ice-breaking cones are compared. Findings - The DEM can be used well to simulate the ice loads on conical structures. The influences of ice velocity, ice thickness, conical angle on ice loads can be analyzed with DEM simulations. Originality/value - This DEM can also be applied to simulate ice loads of different offshore structures and aid in determining ice load in offshore structure designs. © Emerald Group Publishing Limited. Source

Hu Y.-H.,Shanghai Maritime University | Tang J.-J.,Shanghai Maritime University | Li Y.-Y.,Shanghai Maritime University | Liu S.-W.,China Offshore Technology Center
Communications in Computer and Information Science

Because of the particularity of liquid cargo transported by liquid cargo ships, traditional ship stability calculation method is not satisfied enough, especially in the respects of matching degree and calculation precision. In order to solve these problems, this paper proposes an optimal method for stability calculation of sea-going liquid cargo ship. Corrections of trimming and free surface are considered, besides, new data preprocessing is adopted. The simulation is demonstrated that this method could satisfy the stability calculation requirements of these liquid cargo ships with good expandability. © Springer-Verlag Berlin Heidelberg 2014. Source

Qi K.-L.,Shanghai JiaoTong University | Liu J.,Shanghai JiaoTong University | Liu S.-W.,China Offshore Technology Center | Wang G.,China Offshore Technology Center
Chuan Bo Li Xue/Journal of Ship Mechanics

New large ships for transportation in the Arctic should be designed to meet the IACS Polar Class Rules. The designs of these vessels bring new challenges to owners, designers, operators and regulators due to the lack of relevant experience. In this study, the complete procedure of evaluation of hull structural strength subject to ice loads is presented. The responses of hull structure are computed with nonlinear static FE analysis to assess the structure strength under different ship/ice interaction scenarios in addition to Polar rule-defined ice loads. Acceptance criteria using limit load concept from load/deflection curve from the results of nonlinear finite element analysis are introduced for shell plating and stiffeners under design ice loads. Linear eigenvalue buckling analyses were carried out to define the critical buckling loads of side stringer for confirming its stability. In this paper, the influence of local fine mesh size on limit load and the reliability of the limit load are discussed to improve the procedure of strength assessment of hull subject to ice loads. Suitable fine mesh size is proposed for the nonlinear finite element analysis procedure. Analyses were carried out for the irregular load/deflection curves which may cause inaccurate estimation of limit loads. These analyses can help estimating limit loads more accurately from those irregular load/deflection curves. Source

Hu Y.,Shanghai Maritime University | Tang J.,Shanghai Maritime University | Xue S.,Shanghai Maritime University | Liu S.,China Offshore Technology Center
International Journal of Naval Architecture and Ocean Engineering

Stability criterion and its calculation are the crucial issue in the application of sail-assisted ship. However, there is at present no specific criterion and computational methods for the stability of sail-assisted ship. Based on the stability requirements for seagoing ships, the stability criterion of the sail-assisted ships is suggested in this paper. Furthermore, how to calculate the parameters and determine some specific coefficients for the ship stability calculation, as well as how to redraw stability curve are also discussed in this paper. Finally, to give an illustration, the proposed method is applied on a sail assisted-ship model with comments and recommendations for improvement. © 2015 SNAK. Source

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