限界状態関数の4次モーメント標準化による構造信頼性解析

摘要

信頼性設計法では、想定した限界状態に対して適切な信頼性を確保 することが目標となり、破壊確率を効率よく計算することが重要な命 題である。破壊確率を計算するために、一次信頼性解析法（FORM）は一 般的な手法として広く認識されているが、信頼性指標は標準正規空 間における原点から限界状態曲面への最短距離として定義され、限界 状態関数の導関数を求めなければならず、設計点を求める時に局部収 束などの問題点がある。%In order to avoid the difficulties involved in searching the design point by iteration using the derivatives of the performance function, a principle shortcoming of reliability methods based on the first-order reliability method (FORM), an explicit fourth-moment reliability index, which is derived from the fourth-moment standardization of performance function, is presented and investigated in the present paper. The proposed formula is simple, and does not require integration or solve nonlinear equations, which are necessary in current used formulas. Through the investigations of the present paper, it is found that the third-moment method can be significantly improved by the proposed simple fourth moment reliability index and the fourth-moment reliability index has sufficient accuracy as a reliability index based on the fourth-moment standardization of performance function.