| Subsea structures such as Christmas tree and subsea manifold are important components of subsea production system.During trawling operation,trawlboard may impact subsea structure,which seriously affect operation of subsea production system.The main function of the subsea protection sturcture is to protect subsea structures from the damage caused by trawling and falling objects.At present,the load design and damage assessment of the subsea protection structures in China are based on the European standards.Due to the difference of fishing vessels in China and Europe,the European standards cannot accurately predict the impact energy between trawlboard and protection structure and the damage degree of during the impact.Based on the information of fishing boats in the target area,the size,weight and operating speed of the trawlboard in the target area are determined,and the impact energy of the trawlboard on the subsea structure in the target area is calculated accordingly.Based on ABAQUS,a multivariate coupled finite element analysis model for the subsea protection structure of subsea structure considering the interaction of pile and soil was established.Firstly,the effects of the thickness of the subsea protection structure panel,the quality of the trawlboard and the trawl speed on the damage of the subsea protection structure of subsea structure were studied.Secondly,the damage degree of the subsea protection structure of the underwater structure with and without consideration of the pile-soil interaction is compared and analyzed.Based on the energy variation of the trawlboard,the energy absorbed by the subsea protection structure in the collision process was analyzed.Finally,based on the theory of composite analysis,this thesis explores the influence of FRP panel thickness on the damage and energy absorption of the subsea protection structure.The results of this thesis show that the maximum weight of the trawl board in the target sea area is 2.5t,and the maximum impact energy of the trawl board on the subsea structure obtained by theoretical calculation and numerical simulation is 9.2k J and 8.4k J,respectively.When the kinetic energy of the trawlboard is constant,the residual kinetic energy of the trawlboard is less and the energy absorbed by the subsea protection structure is more with the increase of the thickness of steel and FRP subsea protection structure panels.The effect of pile-soil interaction on the damage of the subsea protection structure is mainly reflected in the later period of impact interaction.The seabed soil has a better inhibition effect on the vibration of the subsea protection structure,and the energy absorbed by the subsea protection structure can be converted into the energy of the soil,thus reducing the damage and deformation of the subsea protection structure.Compared with steel panels,FRP has obvious advantages in lightweight and the subsea protection structure absorbs less energy in the collision process of the trawlboard.When FRP panels are used,the frame of the subsea protection structure needs to be optimized to adapt to the characteristics of large deformation of FRP in the collision process. |
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