工字型截面构件的船体板架结构可靠性优化

利用有限元方法进行结构分析，建立失效模式的安全余量方程，失效模式的可靠性指标由一次二阶矩法确定，由分枝限界法识别主要失效模式，结构系统和主要失效模式的可靠性指标之间的关系通过ＰＮＥＴ法（概率网络估算法）确定，并依此导出系统可靠性指标相对设计变量的导数。结构的可靠性优化，通过考虑具有工字型截面梁元的稳定性，将设计变量减少一半，降低优化规模，然后，采用最佳矢量法完成两类优化设计：在结构系统可靠性约束下

Reliability-Based Optimum Design of the Ship Grillage Structure with I-Shaped Cross Section Components

The finite element method was adopted for structural analysis, and the safe margin equation was set up for a failure mode. The level 2 method was used for determining the reliability index of a failure mode. The dominant failure modes were identified by the Branch and Bound method. By means of the PNET method, the relation was set up between the reliability index of structural systems and that of dominant failure modes, on which the sensitivity of the reliability index of structural systems to design variables was derived in an explicit form. As for the structural reliability optimization, through taking into account the stability of beam components with I shaped cross section, the number of design variables was half reduced, and the optimization scale was degraded. On the basis of the sensitivity analysis, the two kinds of optimum design were carried out by the best vector method. One is to minimize the structural weight under the constraint on the allowable reliability; the other is to maximize the structural reliability under the constraint on the structural minimum weight. The numerical examples show that the minimizing of structural weight under the allowable reliability is achieved mainly by reducing the size of the component with lower stress level, and the maximizing of the structural reliability under the constraint on the structural minimum weight mainly by enlarging the size of the components with higher stress level. The results demonstrate that the reliability based optimum design based on the PNET method is effective for the reliability optimization of large scale structures.