報告書番号

U02018

タイトル（和文）

鉄筋コンクリート製地中構造物の耐震性能照査法の高度化（その２） --密な乾燥砂地盤・構造物連成系解析における地盤非線形モデルの適用性評価--

タイトル（英文）

Development of Advanced Earthquake Resistant Performance Verification on Reinforced Concrete Underground Structure Part 2-Verification of the Ground Modeling Methods Applied to Non-linear Soil-Structure Interaction Analysis-

概要 （図表や脚注は「報告書全文」に掲載しております）

本研究では，数値解析手法によるRC地中構造物の耐震性評価で使用する地盤のモデル化手法の適用性について，振動台実験のシミュレーションによって検証した．構造物はトリリニアのＭ－φ関係を有する梁要素でモデル化した．地盤については，地盤剛性のひずみ依存性と初期拘束圧依存性のみを考慮したモデル化およびそれらに加えて震動中の拘束圧の変動による剛性の変化や地盤のダイレイタンシー特性も考慮したモデル化の2種類の手法を採用し，地盤のダイレイタンシーによる影響について検討した．水平一方向加振の実験における鉛直加速度の増幅や地表面の鉛直変位，さらには構造物の側壁に作用する特殊な動土圧は地盤のダイレイタンシーを考慮した場合のみ再現可能であったが，この種の地中構造物の耐震性を評価する上で重要となる構造物頂版に作用するせん断力の評価については，いずれのモデル化手法も適用可能であった．

概要 （英文）

In order to develop an advanced verification method for earthquake resistant performance on reinforced concrete underground structures, the applicability of two different types of soil modeling methods in numerical analysis were verified through non-linear dynamic numerical simulations of the large shaking table tests conducted using the model comprised of free-field ground or soils and a reinforced concrete two-box culvert structure system. In these simulations, the structure was modeled by a beam type element having a tri-linear curve of the relations between curvature and flexural moment. The soil was modeled by the Ramberg-Osgood model as well as an elasto-plastic constitutive model. The former model only employs non-linearity of shear modulus regarding strain and initial stress conditions, whereas the latter can express non-linearity of shear modulus caused by changes of mean effective stress during ground excitation and dilatancy of ground soil. Therefore the elasto-plastic constitutive model could precisely simulate the vertical acceleration and displacement response on ground surface, which were produced by the soil dilations during a shaking event of a horizontal base input in the model tests. In addition, the model can explain distinctive dynamic earth pressure acting on the vertical walls of the structure, which was also confirmed to be related to the soil dilations. However, since both these modeling methods could express the shear force on the upper slab surface of the model structure, which plays the predominant role on structural deformation, these modeling methods were applicable equally to the evaluation of seismic performance similar to the model structure of this study.

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