A Study On Structural Response Analysis Of Jack-up Platforms Subjected To Ice Loads

Due to its high efficiency and low cost,jack up platform has been widely used in shallow water area.But there is no specific application in ice area.Native and foreign researchers show strong interest in this field.To ensure the structural safety of jack up platform under ice load is very important.In this paper,based on a general-purpose truss type jack up platform,the truss legs are replaced by cylindrical ones to study the ice load and structural response.In the study of ice load,the static ice load and dynamic ice load time history of vertical and cone structures are determined respectively by referring to relevant codes and well-known research results in the industry.The interaction between the jack up platform and sea ice is discussed.The jack up platform is equivalent to a vertical structure through literature research.Stability is an important performance index of jack up platform in ice area.In this paper,the anti-overturning,anti-sliding and spud can strength of jack up platform are analyzed.The antioverturning performance has a great limit on the application of jack up platform in ice area,which needs to be specially considered in the design.According to the anti-sliding analysis,assuming the typical soil geological conditions,the simplified analysis and numerical simulation are carried out respectively.The results show that the sliding performance can basically meet the operation requirements in ice area.The yield and buckling performance of pile shoes are evaluated.In the case of light ice,some spud can structure fail,so the structure needs to be strengthened.Research on the overall structural strength of the platform has been performed.The lattice legs were equivalent to the cylindrical types,with hydrodynamic and structural equivalence to simulate the design performance of the original platform.The displacement of the upper platform and the structural strength of the pile leg are mainly analyzed.Under light ice condition,the displacement of the structure is large and the stress exceeds the allowable value,so it is necessary to redesign and strengthen the legs when it is used in ice area.The dynamic effect is one of the key issues in this paper.A very large dynamic amplification coefficient is obtained by using the single degree simplification method.However,through the time-domain dynamic analysis,the coefficient is greatly reduced,and the response is only increased about 30% on the static basis.Moreover,when the initial effect gradually decreases,the response is even lower than the structural response under the static time history.The dynamic effect of response is not obvious.The time-domain dynamic analysis method should be used in the design analysis,which can more accurately determine the structural response under the ice load.At present,increasing ice-resistant cone is one of the main methods to reduce the structural response under ice load.In this paper,the effect of ice-resistant cone is discussed by comparing the response before and after adding ice cone.For anti-overturning,anti-sliding ability,acceleration and structural stress response,the performance of jack up platform is improved obviously by adding cone.