報告書番号

U00025

タイトル（和文）

現場計測データに基づくアーチダム－岩盤－貯水系の3次元時刻歴応答解析法の適用性検討

タイトル（英文）

Verification of a Nonlinear Finite Element Method Considering the Joint Opening Behavior and Dam-Reservoir-Foundation Interaction - Theory and Comparison of the Numerical Results with In-situ Test Results -

概要 （図表や脚注は「報告書全文」に掲載しております）

本研究は、アーチダムのジョイント部における非線形挙動や、岩盤及び貯水の相互作用を考慮した3次元有限要素モデルにより、川浦ダムの起振実験のシミュレーションを行い、本解析手法の適用性について明らかにしたものである。本解析手法により、固有振動数やモード形状等の計測値が概ねシミュレートでき、貯水位の変化に伴うダムの固有振動数の変化についても、ダムを連続体とした従来の線形解析モデルより、計測値と一致する結果が得られた。また、解析結果より、貯水位が高い場合、ダム軸方向の圧縮力によりジョイント部は密着し、貯水位が低下するにつれて、固有振動数が高周波数側に変化してくことがわかった。さらに、川浦ダムでは、貯水位が常時満水位の７５％程度以下になると、ダム軸方向の圧縮力が減少し、ジョイント部に剥離・接触挙動が発生する領域が現れ、貯水位の低下に伴い、固有振動数が減少していくことがわかった。

概要 （英文）

Arch dams usually have vertical contraction joints and the seismic response of arch dams may be influenced by the joint opening behavior. In order to evaluate the earthquake safety of arch dams, it is essential to develop reliable analytical procedures for computing the earthquake response of arch dams including the nonlinear effects of the contraction joint opening. The objectives of this study are: (1) to validate the applicability of a newly developed computer program for the earthquake response of arch dams, including both the effects of dam-water-foundation rock interaction and the nonlinear behavior of the contraction joints; (2) to examine the effects of the contraction joint opening on the dynamic response of an existing arch dam. For these particular problems, numerical simulations of the forced vibration response of an existing dam were executed using the computer program. The results computed from the conventional linear analysis, that assumed the dam body to be a monolithic structure, are also presented for reference and comparison. The measured and computed results are compared for resonant frequencies, vibrational mode shapes of the dam, and the frequency response functions for the dam crest displacement and dynamic water pressure. The computed results including the nolinear effects of the contraction joint opening were more consistent with the trend found in the test results than those obtained from the linear analysis. Based on both test and computed results, it is found that the arch action due to higher hydrostatic pressure under almost full reservoir condition, tightened the contraction joints, and caused the overall dam body to behave more like as a continuous structure. According to the computed results, it is concluded that the contraction joints open and close during the shaking, under less than 75% of the full reservoir condition, and such a varying tightness of the contraction joints really did affect the resonant frequencies of the symmetric vibrational mode.

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