Influence of Typhoon on Platform

Offshore platform structure is the infrastructure of offshore oil and gas resources development and the foundation of offshore production and life. Every summer, extreme environmental loads such as strong winds and huge waves caused by typhoons and hurricanes will bring challenges to offshore platform structures. Once an accident happens, it will not only bring huge economic losses and social impact to the country, but also cause disastrous marine pollution. Hurricane Katrina caused the collapse of the Gulf of Mexico platform in 2005, which made us realize that the elevation and fortification standards of the platform were low due to insufficient consideration of extreme environmental loads. Moreover, the decline in resistance caused by the aging of the platform made it unable to bear extreme loads, which was an important reason for the massive collapse of the platform in this accident. In order to reduce the design risk of environmental load and understand and master the reliability of in-service platforms, this paper has done the following three innovative works: ● Based on the theory of compound extreme value distribution, the concept of design risk of marine environmental load parameters and the method of solving the elevation of offshore platforms are put forward. The design risks caused by uncertainties in extreme value model, sampling method, sampling interval and parameter solution method are discussed. The multi-dimensional composite extreme value distribution model is used to predict the extreme sea conditions of astronomical tide, storm surge and wave height at the same time, and to determine the platform elevation. ● Unfavorable factors such as component defects, mechanical damage, fatigue and damage accumulation of crack propagation on offshore platforms will lead to the attenuation of the overall resistance of the platform and affect the safety and durability of the structure. Therefore, the risk analysis of offshore platforms based on time-varying reliability theory has more important theoretical and practical significance. In view of the fact that previous studies only paid attention to the time-varying attenuation of structural resistance and neglected the time-varying problem of environmental load, after studying the time-varying analysis of corrosion and marine life's attenuation of platform resistance, a time-varying reliability solution method of marine environmental load based on Bayesian theory and equivalent load method was proposed. Because this method uses the real environmental data during the service period of the structure to update the environmental load parameters, the reliability calculation result is more reasonable. ● Typhoon disasters spread all over the coastal provinces of China from south to north; At present, the proven oil and gas resources in China are distributed in Bohai Sea, Yellow Sea, East China Sea and South China Sea. Due to the differences in geographical location and marine environment, the meteorological characteristics and disaster-causing factors of typhoons in different sea areas often show great differences. In order to make the research results of marine environmental conditions better serve the marine industrial planning and resource development, it is an inevitable trend to construct the marine environmental condition parameter zoning. Based on the self-developed "double nested model of typhoon disaster zoning and fortification standards", this paper studies the zoning of China's sea areas, that is, comprehensively considers the intensity and frequency of typhoons in various sea areas and the mechanism and probability characteristics of inducing various disasters, and based on this, constructs the typhoon disaster zoning of various sea areas in China.