Research On Damage Identification Of Offshore Platforms Based On Strain Energy

Jacket offshore platform has been widely used in offshore oil and gas exploration.Due to the complexity of the marine environment,the platform will inevitably be damaged during its service life,so the health monitoring of the platform structure plays an important role in ensuring the safety of offshore operation.At present,damage identification techniques based on structural dynamic response can be divided into parametric and nonparametric methods.In parametric methods,modal parameters and their derived parameters are usually used to obtain damage sensitive features.However,there are still some challenging problems in the practical application of parametric method,such as inaccurate identification of modal parameters leading to low accuracy of damage identification.The purpose of nonparametric(data-driven)method is to extract damage sensitive features directly from measured data.For data-driven method,the key is to find out which index is sensitive to structural damage.It is found that once the structure is damaged,the strain at the damage location will change.Therefore,this paper studies the damage identification method based on the structural strain change,improves and proposes new damage identification method and damage index,and verifies them through simulation and experiment.The results show that the two damage indexes proposed in this paper can effectively identify the location of structural damage,and can accurately predict the damage degree,which improves the effect of structural damage identification.The specific research contents are as follows:(1)In this paper,firstly,the parametric and nonparametric methods of structural damage are briefly introduced.The nonparametric method is compared with the traditional damage identification methods.It is concluded that the nonparametric method has the advantages of fast identification speed and high damage sensitivity,so it has greater advantages in the application of structural damage identification.Then,this paper deduces the method of strain time history data identification based on power spectral density,explains the theoretical principle of damage identification,and finally gives the calculation flow chart,and uses the finite element simulation software to simulate the structural damage of jacket offshore platform,which verifies the effectiveness of the method in non-noise and noise environment to locate the structural damage location,as well as for the micro structure The effect of damage identification.(2)At the same time,based on the theory of structural strain energy dissipation,this paper uses the time history data of the three principal strains of the intact structure and damaged structure to construct the damage identification index,which can accurately identify the damage severity of the structure.Meanwhile,in the simulation of damage identification of jacket offshore platform,the different types of non-noise and noise-bearing damage conditions are simulated to verify the damage conditions.The main response is found Variable data driven damage identification method can be used as a feasible and effective method for damage location and damage severity estimation of marine structures.(3)In this paper,the factors affecting the damage index and how to improve the accuracy of damage identification are studied according to the two damage indexes constructed by the time-domain data of strain.At the same time,experiments are designed to verify the reliability of the method.