Investigating the influence of analysis parameters in three-dimensional elasto-plastic finite element analysis of a gate-type piping support structure

門型配管支持構造物の3次元弾塑性FE解析における解析パラメタの影響検討

滝藤 聖崇 ; 奥田 幸彦  ; 西田 明美  ; Li, Y. 

Takito, Kiyotaka; Okuda, Yukihiko; Nishida, Akemi; Li, Y.

地震に対する確率論的リスク評価(地震PRA)において、設計上の想定を超える入力地震動を対象とした機器・配管系のフラジリティ評価のための現実的応答解析手法の構築は重要課題の一つである。特に、配管系はプラント固有の複雑な三次元形状を有することから、配管支持構造物の配置や剛性等が、配管系全体の応答特性に与える影響が大きく、配管支持構造物を含めた配管系の地震応答解析手法の開発が必要である。そこで筆者らは、配管支持構造物を含む配管系の弾塑性応答解析手法の確立のため、配管支持構造物の弾塑性解析手法の構築を進めている。そのため本研究では、配管支持構造物の弾塑性解析における解析パラメタの弾塑性変形への影響度の違いを把握するため、解析パラメタに対してパラメタスタディ等を行った。まずは、大変形を想定した門型配管支持構造物の繰り返し載荷試験を対象に、3次元有限要素解析モデルを作成し、試験結果と解析結果がおおむね一致することを確認した。続いて作成したモデルを用いて、降伏応力、二次剛性および要素サイズ等の解析パラメタに対してパラメタスタディ等を行った。その結果、解析パラメタが解析結果に与える影響度の違いを把握できたことから、配管支持構造物の弾塑性解析における適切な解析パラメタ設定のための方法論に見通しを得た。

In probabilistic risk assessment against earthquakes (seismic PRA), one of the important issues is the development of a realistic response analysis method for evaluating the fragility of equipment and piping systems subject to input ground motions exceeding design assumption. Particularly, piping systems have complex plant-specific three-dimensional geometries. The arrangement and rigidity of piping support structures have significant impact on the response characteristics of the entire piping system. Therefore, it is necessary to develop a seismic response analysis method for piping systems, including piping support structures. To this end, the authors have been working on the development of elasto-plastic analysis method for piping support structures in order to establish a realistic response analysis method for piping systems including piping support structures. In this study, parametric studies on important analytical parameters were conducted to understand the influence of the analytical parameters on the deformation in the elasto-plastic analysis of piping support structures. At first, a three-dimensional finite element analysis model was created for cyclic loading tests of a gate type piping support structure assuming large deformations. Using the model, parametric studies were conducted for analysis parameters such as yield stress, secondary stiffness and element size. As the result, the influences of the analysis parameters on the analysis results were quantitatively clarified, which provided insight into the methodology for setting appropriate analysis parameters on elasto-plastic analysis for piping support structures.