周方向欠陥を有する配管の地震荷重に対する破壊評価

概要

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Deformation of piping system subjected to dynamic seismic load is restricted by many supports, and it may not deform as large as total elongation even if excessive dynamic seismic load acts on it. This tendency was verified based on many experimental results, and limitation on primary stress was removed and fatigue evaluation was only required for dynamic seismic loads in revised aseismic design codes (JEAC4601-2008). Thus, structural integrity evaluation method for unflawed pipes has been clear, but that for flawed pipes is not established until now. This paper describes the examinations on the fracture assessment method in case dynamic seismic load acts on the pipes having circumferential cracks. If plastic deformation occurs in piping elements, increase of response stress in the elements will decline compared with elastic condition, but response displacement does not decline greatly. That is, the response of piping system subjected the dynamic seismic load is close to deformation control conditions. This aspect was checked by using the finite element analysis for some piping elements and piping systems, and the fracture assessment methods of pipes having circumferential flaws subjected to dynamic seismic loads was proposed.