Safety Assessment And Optimization Design Of Ship Structure Under Falling Objects And Explosion Load

In order to meet the drilling and production requirements,a moon-pool is set in the middle of a certain type of natural gas hydrate drilling and production ship hull,accounting for about one-third of the main hull width,which greatly weakens the longitudinal strength of the hull and reduces survivability in the extremely terrible sea conditions.During the operation of drilling,the explosion caused by the blowout accident and the accidental load generated by falling objects will do damage to the hull structure,affecting operation and sailing safety.Therefore,it is necessary to carry out structural safety assessments under the effects of explosions and falling objects.This paper aims to study the structural safety of the deck under the load of falling objects and the dynamic response of the moon-pool area structure under the explosive load during the course of practical operation.Based on the above studies,this paper analyzes the hull girder ultimate bearing capacity under the influences of falling objects and explosion and provides an optimized design scheme based on bearing capacity analysis.The main tasks completed in this paper are:1.From the perspectives of analysis methods,contact algorithms and basic collision theory,the numerical simulation technology of structural collisions is studied.According to the falling object scene analysis of the target ship,the falling object simulation working conditions are set,and the falling object problem is modeled by finite element.The explicit analysis method of ABAQUS is used to analyze the impact effects of different types of falling objects,and the impact position and angle of impact on the structural damage of the falling object area are studied.Based on the research of collision parameters,the safety assessment of the deck local structure in the dangerous falling object condition is completed.2.From the perspectives of air explosion theory,explosion numerical simulation theory and coupling method,the near-field explosion numerical simulation technology inside the moon pool is studied.The influence of the Euler grid size on the calculation accuracy is analyzed.The finite element model of the moon-pool area structure is established.Combine the equivalent TNT equivalent method and the ideal gas state equation,and refer to the requirements of the API(American Petroleum Institute)specification,multiple calculation conditions with different explosive source TNT equivalent and explosive source height are set up.The explosive shock pressure distribution of the Euler domain inside the moon pool is analyzed.The coupling of Lagrangian and Euler grids is established based on the general coupling method.The dynamic response and energy absorption of the moon pool structure under various working conditions are analyzed,and the safety assessment of the moon pool area structure is carried out on this basis.3.Non-linear finite element method is used to calculate and analyze the ultimate bearing capacity of hull girder and to study the influence of falling objects and explosion loads on the ultimate bearing capacity of hull girder.Based on the direct optimization method,the hull girder model under the action of falling objects and explosive loads is used as the optimization object,the hull girder ultimate strength check criterion is used as the optimization constraint,and the lightest structure weight is used as the objective function,a structure optimized designs based on the hull girder bearing capacity are formed.Finally,the lightest structural weight optimized design on the basis of ensuring the hull girder bearing capacity within the safety limit is formed.