報告書番号

N12

タイトル（和文）

ダムゲートの応力照査に関わる不確実性と管理基準値の検討

タイトル（英文）

Discussion on Uncertainty and Desired Maintenance Criteria in Structural Stress Assessment of Existing Dam Gates

概要 （図表や脚注は「報告書全文」に掲載しております）

ダムゲートの維持管理における普遍的な応力照査上の管理基準値に関する検討を行い，信頼性理論に基づいて管理基準値を試算した．
まず，ラジアルゲート25地点，ローラゲート32地点での実測応力をもとに，設計計算式，FEM解析，実測による各応力が持つ不確実性を定量化した．設計計算応力，FEM解析応力の不確実性は，実測応力との差として評価した．実測の不確実性は，実測荷重条件から応力照査を行う荷重条件までの外挿によって生じる差と定義して，実測荷重から照査荷重への外挿比率により整理した．
次に，これらの不確実性ならびに部材強度の不確実性を考慮した信頼性解析を実施して，設計計算式による応力照査で確保される安全性を評価した．この安全性が満足されるという条件のもと，FEM解析，実測応力に対する管理基準値を試算した．
以上の結果，適切なFEM解析の実施あるいは実測荷重を照査荷重に近い荷重条件として外挿比率を制限することにより，現行の許容応力度を超える管理基準値により応力照査が行える可能性を示した．

概要 （英文）

CRIEPI studied desired maintenance criteria in structural stress assessment of existing dam gates and estimated the criteria based on a reliability theory.
First, uncertainties of stress obtained from design calculation method, finite element analysis and measurement were quantified by using the field measurements at 25 radial gates and 32 vertical lift gates. In the quantification, the uncertainty of the calculation was determined as the difference between the calculated stress and the measured stress. On the other hand, an extrapolation of the stress measurement was defined as multiplying the measured stress value by the ratio from the load condition at the field measurement to the assessment load condition, and the uncertainty within the extrapolation was evaluated as the uncertainty in the measurement.
Then, based on the reliability theory, the safety level guaranteed in the stress assessment was computed by using design calculation stress as a structural response and design allowable stress as a criterion of the assessment. In the computation, the uncertainty of the calculated stress and the strength of structural member of the gates were considered. Meeting the safety level for the design based stress assessment, the stress criteria were derived for both of the stress assessment with the finite element based stress and the assessment with the extrapolated stress of the measurement.
Finally, the result showed that the stress criteria beyond the design allowable stress value was applicable in the stress assessment of the existing dam gates when the appropriate finite element analysis or the extrapolation under around the assessment load was conducted.

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