泄水建筑物免空化设计的可靠性分析

Reliability analysis in hydraulic design of high-head outlet works without cavitation

本文根据可靠性理论,分析了影响初生空化的各种随机因素的概率分布特性,并给出了以基本变量表达的初生空化极限状态方程,校核了在泄水建筑物常遇水力参数变化范围内,与现行规范规定的安全裕度大致相当的可靠指标β,建议取泄水建筑物的免空化目标可靠指标β_x=1.0—2.0.在基础上,采用国际安全度联合委员会(JCSS)建议的JC方法,进行了泄水构件免空化概率极限设计的计算和分析.实践证明,这一方法有利于设计者全面考察各种随机因素的不确定性影响,有利于科学地确定泄水建筑物的免空化控制标准,优化泄水建筑物的水力设计.

According to reliability theory in this paper, the characteristics of probability distribution of various random factors, which affect cavitation inception, is discussed. The limit state equation expressed by basic variables is derived from the limit condition of cavitation inception. The reliability index β corresponding to safety margin suggested by existing codes is calibrated in the usual hydraulic range of outlet works and the aim reliability index βk equal to 1.0-2.0 is suggested by present reliability analyses. A JC method (suggested by JCSS) is used for calculation of probabilistic limit state design. Analyzed and calculated results indicate that the method is favourable in making synthetic investigation on influence of uncertainties due to various random factors on cavitation inception and favourable in scientifically determinating the control standards of outlet works without cavitation.