大型舰船结构的可靠性研究

Reliability analysis for large ship structure

对具有多随机变量的大型船舶结构可靠性分析中的力学模型选取、安全余量建立、安全余量的敏度分析、减缩刚阵和反向节点力的公式推导等问题进行了研究.设结构是空间理想弹塑性梁板体系,以杂交梁元和加筋板格元来模拟三维结构体系,采用随机有限元计算结构系统的响应量;用验算点法计算失效模式安全余量的可靠性指标;用改进的分枝限界法寻找主要失效模式,通过对主要失效模式方程的线性化研究,计算各主要失效模式安全余量之间的相关系数;然后用PNET法计算结构系统的可靠性指标.在可靠性分析过程中,用随机有限元法对安全余量进行敏度分析,在提高可靠性分析效率的同时,也能指导设计,是必要而又十分有效的手段.最后给出了一个船舶的结构的算例,说明分析的有效性.分析表明,这些研究可提高具有多随机变量的大型结构系统可靠性分析的计算精度,为复杂结构系统可靠性分析奠定了一定的理论基础.

Questions such as choice of mechanical models, establishment of safety margin, and sensitivity analysis of the safety margin are researched in the reliability analysis of large ship structure with several random variables. Deduction of formulae of reduced member stiffness matrix and opposite sign of the equivalent nodal force are educed. Given that the structure is a spatial, ideal elastic-plastic girder-pane structure system, three-dimension spatial structure system is established by adopting hybrid girder element and SP panel element. The static response of structural system is analyzed by using the stochastic finite element method, and the significant failure modes are identified by using the advanced branch-and-bound method. The correlation coefficients of failure modes safety margins are calculated by linearization research of safety margin functions of the significant failure modes, and the reliability of structural system is evaluated by PNET method. In the process of the reliability analysis, the sensitivity analysis by using stochastic finite element method can not only improve the efficiency of the reliability analysis, but also direct the structure design, so it is a very necessary and effective means. Finally, a ship structure calculation example is presented to show the validity of this analysis. The result indicates that this research could improve the calculate precision of large structure system with several random variables, and establish theory foundation for the reliability analysis of complicated structure system.