The Dynamic Characteristics Of The Jacket Platform Dynamic Reliability Analysis

With regard to the ocean petroleum industry, developed from shallow water to more complicated and dangerous deep seas, the structural design and analysis for the deep seas platform become more complex. Therefore, the assumptions that consider the platform as rigid body and the wave loads acted on the structures as static or semi-static, is reasonable for the shallow water platform and not adaptable to the deep-sea one. While the working seas deeper, the natural period of the platform increases and the structural resonance become more possible. Considering the remarkable dynamic response of the deep-sea platform, it is necessary to carry out the dynamic response analysis.In the thesis, the mode and stochastic response of the jacket have been studied on the basis of finite element method, the theory of structure stochastic response and investigations carried out home and abroad. In addition, the structural dynamic reliability has also been discussed. The paper mainly contains following parts.Firstly, based on the review of investigative progress, the significance of the theme and the author's idea are presented. Then in Chapter 1, the 6-node triangular shell element, used to simulate the platform deck, is deduced according to the Mindlin assumption. The random wave loads are discussed to calculate the wave forced on the legs of the jacket in Chapter 2. The Airy wave theory and linearized Morison equation are utilized to obtain the wave loads spectrum. The stochastic response of the structure is usually solved in two ways: one is in time domain; the other is in frequency domain. In Chapter 3, power spectral density (PSD) functions are introduced to calculate the stochastic response in frequency domain, which is achieved by programming. Chapter 4 is the main part of the thesis, in which the essential methods of structural dynamic reliability are put forward in details, including passage probability, failure model, failure criteria, etc. In the end, the mode and stochastic response PSD of the jacket are analyzed, and the fatigue reliability under random wave loads is discussed on the basis of the first passage theory and random accumulative damage models.