Study On Structural Damage Of K Type Oil Derrick Based On Dynamic Analysis

The oil derrick is important equipments of the petroleum drilling system. Because in the long term bad outside environment that the derrick produces partial or whole harm, They are hidden danger of the safety in production. At present, methods of the stress test and the computer simulation have a definite limitation. Research a sort of scientific test method is very important on theory and application to enhance evaluating the carrying capacity of oil derrick and safety evaluation method.The damage detection method based on dynamic is widely studied by scientists: as a hot topic. With the development of modal analysis method, the damage detection method based on dynamic has get a lot of results. For large-scale structures it is very difficult to simultaneously identify the location and extent of element-level damage by using the finite element modal measurements, which often leads to wrong results of damage identification. The methodology,which is composed by the global identification and local identification, is an effective approach to identify the structural damage in complex structures. And then the local damage identification of beam-like structures is studied with modal measurements based on local vibration. The main contents of the dissertation are listed as follows.In this paper after a brief overview of the development of structural damage identification, the connotation of structural damage identification is pointed out in an extended sense. Actuality of damage identification for structures is expatiated and comments are made on the methods of them. These methods include curvature model, strain modal shape, vibration modal, flexibility matrix, stiffness matrix and wavelet analysis etc..Based on the basic structure and force characteristic of JJ160/41-K type oil derrick, Solid model of JJ160-41 K type oil derrick with similarity theory and analyse the solid model been make. The result indicates that when structure of derrick model changes partly, the holistic natural frequency of derrick synchronously changes. Dissertations based on frequency finger mark curve of JJ160/41-K type oil derrick, local damage localization based on dynamic signatures is Presented. The applicability of three dynamic signatures based frequency data are studied, and the numerical simulations of different damage cases are carried out. The results demonstrate that the normalized change ratio of frequency is stable as changing the damage location and extent. Therefore, the normalized change ratio of frequency is selected as dynamic signature of oil derrick structures based on local vibration. The effectiveness of the damage localization by using of the proposed dynamic signature is illustrated by a numerical example.