報告書番号

N10007

タイトル（和文）

構造物の耐震裕度と地震リスクの対応関係に関する研究－構造耐力～リスクダイアグラムの提案－

タイトル（英文）

Study on Structural Seismic Margin and Probabilistic Seismic Risk -Development of a Structural Capacity-Seismic Risk Diagram-

概要 （図表や脚注は「報告書全文」に掲載しております）

本報告書では，説明性および合理性が高い耐震裕度を提案すると共に，地震リスクとの関係を明らかにするダイアグラムを提案する。次に構築した方法を用いて，全国4地点を対象に構造耐力～リスクダイアグラムを計算した。得られた主な成果を以下に記す。
(1) 地震動強度を指標とした耐震裕度の方が，応答に基づく耐震裕度よりも汎用性かつ，理解され易さという観点から優れていると考えられるため，地震動強度を指標とした耐震裕度を用いることを提案する。
(2) 目標とするリスクレベルが与えられた場合，構造物の損傷度の不確実さの大きさが不明な場合でも，確定論的な安全性評価で十分か，詳細なリスク解析が必要かを容易に判断することが可能である。
(3) 構造耐力～リスクダイアグラムは地点により大きく異なる。これは，対象地点の地震ハザードの地域性がダイアグラムに強く影響するためである。また，所与のリスクレベルを満たすために必要な構造耐力は，不確実さβの影響を受けにくい。

概要 （英文）

Seismic margin is extremely important index and information when we evaluate and account seismic safety of critical structures, systems and components quantitatively. Therefore, it is required that electric power companies evaluate the seismic margin of each plant in back-check of nuclear power plants in Japan.
The seismic margin of structures is usually defined as a structural capacity margin corresponding to design earthquake ground motion. However, there is little agreement as to the definition of the seismic margin and we have no knowledge about a relationship between the seismic margin and seismic risk (annual failure probability) which is obtained in PSA (Probabilistic Safety Assessment). The purpose of this report is to discuss a definition of structural seismic margin and to develop a diagram which can identify a relation between seismic margin and seismic risk. The main results of this paper are described as follows:
(i) We develop seismic margin which is defined based on the fact that intensity of earthquake ground motion is more appropriate than the conventional definition (i.e., the response-based seismic margin) for the following reasons:
-seismic margin based on earthquake ground motion is invariant where different typed structures are considered,
-stakeholders can understand the seismic margin based on the earthquake ground motion better than the response-based one.
(ii) The developed seismic margin-risk diagram facilitates us to judge easily whether we need to perform detailed probabilistic risk analysis or only deterministic analysis, given that the reference risk level although information on the uncertainty parameter beta is not obtained.
(iii) We have performed numerical simulations based on the developed method for four sites in Japan. The structural capacity-risk diagram differs depending on each location because the diagram is greatly influenced by seismic hazard information for a target site.
Furthermore, the required structural capacity corresponding to the given risk level is not affected by the uncertainty parameter beta.

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