Structural Damage Identification Of Jacket Platform Based On Wavelet Packet Analysis

As the key place for the exploration and development of offshore oil and gas resources,storage and transfer,production operations and life,the offshore platform has always served in the harsh marine environment,and has been subjected to corrosion by seawater,currents,waves and external loads such as sea ice and ships for a long time,coupled with improper design,use and defects in the material itself,resulting in inevitable damage to the offshore platform.With the generation and accumulation of damage,the service life of the offshore platform and the safety of production operations are seriously reduced.Therefore,it is of great practical significance to detect the damage of the platform in time,to identify,locate and evaluate the damage degree,which is of great practical significance to ensure the safety of the production and operation of the offshore platform.In this paper,the wavelet analysis method is used to identify the model signal of the jacket platform.The specific contents include:1.Perform modal analysis and transient dynamic analysis on the jacket platform.Taking the existing jacket platform model in the laboratory as the research object,the finite element model of the jacket platform is established.The modal analysis is carried out on the finite element numerical model in the non-damaged state and the damaged state,and the natural frequency of the numerical model is obtained.The transient dynamic analysis of the finite element numerical model is carried out in the non-damaged state and the damaged state,and the acceleration response signal of the platform numerical model is extracted.This analysis provides data support and theoretical basis for model correction and wavelet packet damage identification2.Carry out the indoor experiment of the jacket platform model,and correct the finite element model based on the vibration signal.Firstly,the laboratory jacket platform is tested with damage and without damage.The sine excitation method is used to test the damage-free platform model and the damaged platform model respectively.The vibration response signals of the structure in the two states are extracted,and the random subspace is used.The vibration response signal is analyzed by the method to obtain the natural frequency of the jacket platform model.Compared with the natural frequency of the finite element numerical model,the first-order optimization algorithm is used to correct the finite element model to achieve the consistency between the finite element model and the indoor model.3.Use the wavelet packet analysis method to identify the damage of the jacket platform.Firstly,the vibration response signals of the modified finite element model and indoor model are analyzed to verify the applicability of the wavelet packet analysis method.Different types of damage simulations are carried out on the finite element model using the method of reducing the element stiffness of members,including: different degrees of damage to members,damage to different types of members,simultaneous damage to different types of members,and simultaneous occurrence of different types of members.different injuries.The extracted vibration response signal is analyzed by wavelet packet to identify damage.The research results show that the wavelet packet analysis method can well identify the damage of the rod,and through the change of the energy ratio of different nodes,the damage of different types of rod frames can be identified.Therefore,using the wavelet packet method,the damage identification of the jacket platform structure can be realized.