Research On Damage Diagnosis Of Jacket Offshore Platform Based On Modal Analysis

At present,more and more offshore platform is in the mid-late service,because of the special working conditions,the platform structure is easy to generate different types and different degrees of damage,the local damage may result in instability of the overall architecture of the offshore platform,damage,reduce the structure bearing capacity of the offshore platform,threatening the normal work of offshore platform.In order to avoid the structure damage of the offshore platform in service,an effective damage diagnosis method is necessary,which is of great significance to guarantee the life safety of the platform staff and protect the Marine environment.In view of the problem that it is difficult to quantitatively diagnose different types of damage in the current dynamic damage diagnosis methods for offshore platforms,this paper takes the Ringhorne offshore jacket platform in Norway in the North Sea as the research object.Based on the modal analysis method in the detection method of global damage,A damage diagnosis method combining Curvature Mode and Strain Mode(CM&SM)is proposed,which provides a reference for the quantitative diagnosis of different types of actual damage during the service of jacket platform.In order to solve the problem of damage localization and damage degree diagnosis of the offshore platform at the same time,the jacket offshore platform is simplified into several beam structures in this paper.First,the damage location is located through the difference of curvature mode values of each node.Secondly,based on the strain mode theory,the damage index is calculated and the damage degree is quantitatively described.Then,the correlation between damage index and damage characteristics was studied,and the relationships among actual crack length,dent damage depth coefficient and damage index were established by ABAQUS simulation combined with literature data.Finally,taking the jacket offshore platform as a numerical example,the diagnosis effect of multiple damage cases of single component and multiple components is evaluated by numerical verification method.Numerical simulation results show that the present CM&SM diagnosis method is convenient and quick to fixing the jacket offshore platform structure damage,quantitative estimate damage degree damage location,and the jacket platform in the crack,the two different types of injury of circumferential crack length and quantitatively estimate collision concave depth,to ensure the accuracy.