Numerical Simulation Of Marine Structure–level Ice Collision Based On The Cohesive Element Method

With more human activities in the polar regions,accurate prediction of ice loads is of great significance for keeping these activities safe.Collision between marine structures and ice sheet is one of difficult research issues,because collision is a nonlinear problem and sea ice has complex physical properties.Based on the brittle behavior of sea ice during the interaction,this paper uses Cohesive Element Method(CEM)to simulate fracture and failure process of ice sheet.In the numerical model,the ice is set as a mixed-mode fracture model with cohesive elements and hexahedra bulk elements,and the water foundation effect is considered as a buoyance simplified model with rigid-material-bottom assumption used in the references and a parametric buoyance model with user defined subroutine in LS-DYNA which is advanced by author.As a preliminary step,the ice model is run with a series of parameters and the sensitivity analysis is carried out.The results show that the failure strain of bulk elements and shape of the plastic stress-strain curve have great effects on impact forces,while the value of fracture energy affects response of both types elements in ice model.In order to verify the accuracy of the simplified buoyancy model with user defined subroutine,the ice floating motion is performed.Then simulation results under different ice thickness and two simplified buoyancy models are discussed.The deformation,formation and accumulation of ice fragments which are successfully captured indicates CEM is capable to deal with plasticity and fracture.In addition,computational impact forces are analyzed.The results show the simplified model with rigid-material-bottom assumption has a little larger impact forces then the parametric buoyance model with user defined subroutine and the impact forces are linearly increasing with thickness of ice which fits empirical formulas well.