Research On The Structural Strength Acessment Of Floating Support Platform Considering The Impact Of Living Quarters

Floating support platform is an important project for the development of far-reaching offshore oil and gas resources in the South China sea and the defense to external harassment.The research and development of floating support platform is of great strategic significance.Because of the numerous cabins of the whole platform,the different function and irregular arrangement,dealing with the harsh marine environment,the structure is complicated.Due to the increased high stress area and the hot spot,the difficulties of strength assessment have enlarged.In structural strength evaluation,the selection of analysis methods,the grasp of stress level of the ship,the selection of fatigue hot spots and the fatigue resistance design of dangerous joints are unknown challenges.There are still some technical difficulties to be solved in the nesting of sub-models in hot areas.The key technologies used in this study such as global strength assessment technology for the whole ship,fatigue strength assessment technology for key nodes,submodel nesting technology and so on,are able to carry out strength verification for new structural forms considering living quarters.The verification results have practical reference significance for introducing advanced design concepts and improving structural safety.Based on the three-dimensional linear hydrodynamic theory and the total strength analysis method of BV classification society,this paper establishes a rough finite element structure model for the whole ship of the support platform,and predicts the wave loads on it.under the self-propelled condition and full load operation condition,respectively forecast the wave load of target security platform based on the spectral analysis,to get each design wave under the DLP,and then load into the structure finite element model to make a coarse mesh analysis of the security platform.So we get the whole stress distribution and the high stress area,and then summarize the hull stress changes and structural deformation characteristies of each part,preliminarily summarize the key factors influencing the security platform's overall strength,to get an overall understanding of the strength characteristics of the security platform,which provides guidance for typical fatigue node selection and modeling.Based on the strength theory and validity theory of superstructure,the contribution of the living quarters to the global strength and the mechanics of resistance to total longitudinal bending are analyzed.Considering the proportion of living quarters modules in the total length of the ship,the design requirements of improving lighting and comfort,and the draught limitation of huizhou port,It is necessary to investigate the influence of the living quarter on the overall strength of the ship.Through calculation and analysis for the stress distribution and deformation characteristics of the whole and the different parts of the support platform with or without the living quarter,we can summarize the reduced stress level with the living quarter in the platform.This paper puts forward the concept of effective degree of superstructure participating in the overall strength.Comparing with the calculation results of the effective degree of living quarter's each deck participating in the overall strength by finite element and theory ways,this paper examines the deck strength of total contribution.Based on the fatigue spectrum analysis method.the fine grid model of typical fatigue nodes was established and the fatigue strength was analyzed by using the fatigue node screening technology.The core content of spectral analysis is to obtain the amplitude response transfer function Raos,under each environment through the calculation of fluid-structure interaction.Combined with BV S-N curve,get short-term statistics of fatigue.Referring to wave scatter diagram of work area.the sum of all short-term sea state of fatigue damage values is the value of fatigue cumulative damage.Adopting the submodel nesting technology.calculate the 10 typical nodes' fatigue damage of a self-propelled condition and three operation conditions.and then get fatigue damage regularity.The time distribution coefficient was introduced to calculate the real cumulative fatigue damage of the platform during the whole service period and the plate's thickness and corrosion were corrected.Finally.the fatigue life structure of hot spot structure is optimized for the dangerous nodes obtained.Different optimization schemes are put forward,and the fatigue calculation results of each schemes choose the most suitable design.It provides a reference for the anti-fatigue design of other ships with similar structures.