Analyzing and updating on the global time-dependent reliability for ageing platforms in ice zones

作者：Chen Tuanhai; Chen Guoming^*; Lin Hong

来源：Acta Petrolei Sinica, 2011, 32(3): 518-523.

• Ageing platform
• Bayesian update
• Failure-rate function
• Ice zone
• Resistance degradation
• Stochastic ice-load process
• Time dependent reliability

Since the number of ageing platforms increased rapidly and ageing effects would imperil the safety and service ability of structures, the present paper brought forward an analysis model for the global time-dependent reliability of ageing platforms in ice zones and investigated update ways of the time-variation reliability based on the Bayesian theory. The ice-load process was simplified to be a pulse sequence with random intensity and intervals and the occurrence number of ice loads was described by the Poisson point process according to probabilistic characteristics of load intervals. The base shear force in the ultimate limit state was taken as a whole resistant index for offshore platforms and a corrosion model with the Weibull function expression was employed to study the resistance degradation of platforms. Based on the conditional probability model and the load-strength interference theory, a probability differential equation of ageing platforms in ice zone was established and analysis models of the global time-dependent reliability and failure-rate function were developed. A method to modify influential factors of the resistance degradation based on the Bayesian approach was given and the reliability update of ageing platforms through the modified degradation model was investigated. Finally, the time-dependent reliability of an ageing platform in an ice zone of the Bohai Bay was taken as an example and evaluated. The results indicated that the global time-dependent reliability of the ageing platform decreased rapidly with service-time due to deterioration and load accumulations. The failure rate at initial stages increased slowly and then quickly as the service time reached at a certain stage, showing the feature of a bathtub-like curve at the two latter stages. Variations in both the reliability and failure-rate function were significantly influenced by the resistance degradation model. With the increase of update, the probability dispersion of resistance degradation functions became smaller and the results of reliabilities and failure-rate functions were more accurate.

• 出版日期2011
• 单位中国石油大学（华东）