Research On Performances Design Analysis And Verification Of Ice-resistant Platform Structures

There has been a lot of challenging research about ice-resistant platform structures design in cold regions. In recent years, the economic design of the platform structures is considered increasingly with the pursuit of the maximum economic benefits in oil/gas resource developments. However, the ice-induced vibrations are prevalent phenomenon in those ice-resistant platform structures, resulting in multiple structure failure modes, and even severe ice-induced vibrations may cause performances failure. Therefore, how to meet the performance requirements of ice-resistant platform structures design is worthy of further study.The performances of ice-resistant platform structure constitute a variety of performance requirements.The design process of the ice-resistant platform structures inclues conceptual design, preliminary design and detailed design, and the conceptual design and the preliminary design are to determine the performances of the ice-resistant platform structures, which is necessary to carry on in-depth research. A systematic research on the ice-resistant performance design theory of the platform structures, the local-oscillator theory of the isolation cones and the concrete platform structure with economic performance is presented based on in-situ results of ice-induced vibration and the current progress of ice load.Based on the field test data, the performance design of the ice-resistant platform structures is studied. There has been carried out field tests for many years, and has gained a lot of valuable measurement data. For Bohai Sea as an example, the full-scale field test system of ice conditions and ice-induced vibration responses are introduced, and the recent research progress about monitoring methods, principle and technology is summarized. Based on ice-force mechanism, ice loading model and ice-induced vibration failure, the evaluation index of ice-resistant performances is developed for the platform structures in cold regions. A general analysis about ice-resistant performances evaluation for three typical platform structures is processed according to the performance evaluation index and the field test data in the JZ20-2Seas.The main influence factors of performances design for ice-resistant platform structures are the characteristics and development model of oil/gas resources, static and dynamic properties of platform structures. The performances design theory is met the requirements of security, serviceability and economic performance for ice-resistant platform structures. And the performance design control limits of ice-resistant platform structures are discussed, including the strength design limits of security performance, the ice-induced vibration failure limits of serviceability performance, structure member section design limits etc. Based on the analysis of ice-induced vibration failure and reducing ice-induced vibration methods, the performance-based dynamical design process is proposed for ice-resistant platform structures. A general analysis about conceptual design and structure type for ice-resistant platform structure is processed in the JZ20-2oilfield.The ice-induced vibration reduction of isolation cones is the application of ice mechanical properties and isolation theory. That is, the ice forces is reduced by flexural strength less than compressive strength, and the isolation cones have a major vibration response in order to reduce the ice-induced vibration energy transferred to the platform structure under the dynamic ice forces. The main parameters of the isolation cones are the spring stiffness and the damping coefficient, and the results show that the spring stiffness is the main influencing factor for isolation cone design, the appropriate damping could absorb the ice-induced vibration energy, which is useful for reducing ice-induced vibrations of the platform structures. For JZ20-2MUQ platform as an example, the ice-induced vibration reduction effect of isolation cones is verified by simulation computations.The initial design of the ice-resistant platform structure is studied by case-based reasoning method for JZ20-2oil field, which including the layout design of piles and supporting members for the platform structure, the parameters design of the isolation cones. The comparison of structure parameters and performances is conducted between initial design platform and JZ20-2MUQ prototype platform. The results show that the initial design platform structure meets the ultimate strength limits, and the correctness and feasibility is verified for the performance design theory and process.Finally, the economic comparison between steel platforms and concrete platforms shows that the concrete platform structures are more economic on construction costs, installation and service costs. The ice-resistant platform structures should have the simplicity, mobility and ice-resistant performances during the marginal oil/gas field developments in cold regions. Then a single concrete pile platform with bucket foundations is proposed. Taking JZ9-3WHPB platform as an example, the initial design of the single concrete pile platform instead of the single steel pile is conducted and its ice-resistant performance is verfied. This is also provided a reference for platform structure types during the marginal oil/gas field development.