Structural Dynamic Response Analysis Of Offshore Platform Jacket Under Extreme Conditions Of Impact And Earthquake

The marine environment where the jacket platform is located is very harsh.In addition to the long-term effects of working loads and environmental loads such as wind,waves and currents,it will also be subjected to extreme loads such as sea ice,ship collisions and earthquakes.At present,the dynamic response of jacket platforms under environmental loads such as wind,waves and currents is the main research direction,while there are relatively few studies on extreme loads such as sea ice,ship collisions and earthquakes.Compared with conventional environmental loads,although extreme loads have a lower frequency and a shorter duration,once they occur,they will greatly affect the strength and overall bearing capacity of the structure.Therefore,accurate and effective analysis of the dynamic response of the jacket platform under extreme loads is of great practical significance to the structural design and safety assessment of the platform.Based on a jacket platform in the Bohai Sea,this paper systematically carried out the dynamic response research of the jacket platform under extreme loads such as sea ice,ship collision,and earthquake.The main work completed in this article includes:(1)According to the relevant parameters and basic assumptions of the jacket platform,the finite element pre-processing software Hyper Mesh is used to perform the finite element modeling of the jacket platform and the pile foundation structure,and the pile-soil nonlinear interaction is considered.The load capacity of the pile foundation under the working load mainly based on the mooring force is checked under different working conditions.(2)Analyze and comb the action mechanism of the three modes of quasi-static vibration,steady-state vibration and random vibration of the jacket platform under the action of sea ice,and establish the calculation model of the jacket platform under the rapid compression of sea ice,According to the characteristics of the Bohai Sea ice speed,focus on the dynamic response of the platform structure under random vibration.(3)Select the supply ship as the collision ship,determine the collision scenario of the ship and the jacket platform from the aspects of collision area,collision speed and attached water quality,and consider the strain rate sensitivity of DH36 marine steel to set the failure criterion of the material.The dynamic response of the platform structure is analyzed in terms of forces,stresses,strains,and motion states.(4)Based on the relevant content of "Code for Classification and Construction of Offshore Fixed Platforms",using time-history analysis method,taking the acceleration time-history curve of amplitude-modulated Tianjin wave as the load input condition,respectively studied the seismic intensity of jacket platform at seven,eight,nine degrees of typical member displacement,velocity,acceleration response and stress-strain responses.