Research On Structural Damage Mechanism Of Typical Offshore Platform Under Falling Accidents

With the rapid development of economic globalization,the marine transportation industry and the marine energy exploration and mining industry are flourishing.However,it also leads to the increasingly close maritime routes and the frequent accidents between ships and offshore platforms,including some accidental accidents such as ship grounding,collision and falling accidents.Taking falling accidents as an example,its consequences often lead to damage to hull structure,or even to heavy losses such as casualties and environmental pollution.Therefore,it is of great significance to study the dynamic response of hull structure under falling accidents,reveal the damage and deformation mechanism and energy absorption mechanism of hull structure,and evaluate the safety design of hull structure based on accident loads.Based on the high-tech ship project of the Ministry of Industry and Information Technology,this paper studies the dynamic response process of stiffened plate structure under the impact of typical box-type and slender rod-type crashes by combining theoretical analysis,numerical simulation and model test,taking the crash accident of ship and offshore engineering as the research background.The structural damage and deformation characteristics and energy absorption mechanism are determined,and the analytical damage prediction method for ship hull slab structure under falling accident is established.The main contents of this paper are as follows:(1)The domestic and international research status and research methods in the field of ship and ocean engineering falling accidents and the dynamic response of related structures under impact loads are summarized,and the main research contents and ideas of the thesis are clarified.(2)This paper summarizes the basic theory and calculation analysis steps of structural impact damage analysis,discusses the common damage and deformation modes of local hull structures under falling accidents and the application of simplified analytical methods,carries out the research of finite element numerical simulation analysis technology,and focuses on the non-linear input method of materials,which lays a foundation for subsequent theoretical prediction and numerical simulation analysis.(3)The falling impact model test of typical hull structure was designed and carried out.The damage deformation and impact load of the structure were obtained.On this basis,the corresponding numerical simulation was carried out to verify and improve the simulation analysis technology and provide a basis for the theoretical prediction of structural damage.(4)The damage mechanism of stiffened plate impacted by slender rod falling objects was studied.Based on the damage and deformation characteristics and failure modes of the whole stiffened plate and the typical components obtained from the falling impact test and numerical simulation analysis,the corresponding theoretical models are established and the analytical prediction formulas are deduced.On this basis,the effects of the rod head type and the falling angle are discussed,and the theoretical prediction formulas of different angle intervals are formed.The engineering application scope and calculation accuracy of the analytical prediction method are improved.(5)The damage mechanism of stiffened plate impacted by box-shaped falling objects was studied.Taking standard containers as typical box-shaped falling objects,accident scenarios and related parameters are analyzed and determined.Based on these,numerical simulation analysis is carried out.Damage characteristics and deformation modes of stiffened plate under two typical accident conditions,vertical drop(surface contact)and inclined drop(liner contact)are obtained.Based on the theory of plastic mechanics,the analytical calculation is carried out and the theoretical prediction formula is deduced.(6)Taking the typical offshore platform cabin structure as the research object,the dynamic response of the cabin structure under the typical crash accident scenario is analyzed and studied based on the simulation analysis technology determined by the research.The safety of the structure is evaluated from the aspects of damage deformation,energy absorption and energy conversion during the crash process.The effects of three typical scenarios of bottom,side and sideline fall on the cabin structure are discussed.Based on the bottom contact,the effects of different components directly impacted at different falling positions on the dynamic response of the cabin structure are studied.