Seismic safety is one of the major key issues of nuclear power plant safety in Japan. It is demonstrated that nuclear piping possesses large safety margins in the various piping ultimate test reports. But it is appeared that there still remain some technical uncertainties about the phenomenon when both piping and supports show inelastic behavior in the extremely high seismic excitation level. In order to obtain the influence of the inelastic behavior of the support to the whole piping system response, and the subsequent interaction when both piping and supports show inelastic behavior, the following two tests have been started. • Support element test: Load-displacement characteristics of the support system including U-bolt, support itself and concrete anchorage are obtained by the forced displacement test. • Seismic proving test of piping system: The small bore piping and support system consisted of three dimensional piping, supports, U-bolts, and concrete anchorages will be excited on the table by the extremely higher seismic level. This paper introduces the major results of seismic proving test of piping and support system. The support element test results is presented in the paper of part 2, and the simulation analyses of these tests are summarized in the paper of part 3 [1, 2].

In this paper, we focused on small-bore piping with a diameter less than 4 inches including support equipments on base concrete, with the purpose of verifying a sufficient seismic design margin. The support element tests were designed to obtain the relationship between force and displacement at piping, when the seismic force loaded on piping support equipments consisting of a U-bolt, support element, base plate, anchorage on a base concrete by confirming the behavior of the equipments as it reaches its failure. The support element tests are the part of inelastic seismic test program [1, 2] and aimed to obtain the following basic data on small-bore piping support equipments: • Relationship between force and displacement at piping; • Failure capacity of piping equipments; • Ductility ratio of piping equipments. Our results can be separated into 4 categories based on the relationship between piping force and displacement and failure mode. Tested failure capacity was higher than the designed allowable force for all failure by a factor of 1.5 to 23, indicating a margin of failure capacity. Cantilever support type have a low ductility ratio when there is the snap of expansion anchor or U-bolt and a high ductility ratio when there is significant plastic deformation of the support. Like their cantilever type counterparts, frame support type have a low ductility when there is the snap of expansion anchor and a high ductility ratio when there is significant plastic deformation of the support and U-bolt, even with brittle failure.

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Seismic safety is one of the major key issues of nuclear power plant safety in Japan. It is demonstrated that nuclear piping possesses large safety margins through the small bore piping and support system test, consisted of three dimensional piping, supports, U-bolts, and concrete anchorages, using the E-defense vibration table of National Research Institute for Earth Science and Disaster Prevention, Hyogo Earthquake Engineering Research Center at Miki city, by the extremely higher seismic excitation level [1, 2]. A simulation analysis for the piping system is described with a focus on the inelastic behavior of the support to the whole piping system response, and the subsequent interaction when both piping and support shows inelastic behavior. The analysis for the inelastic response of the piping seismic test was conducted using the FEM program ABAQUS. It requires a large amount of time to carry out a strain behavior analysis of the localized piping element and also calculate the dynamic inelastic response of the whole piping system, simultaneously. Therefore the following two steps analysis method is proposed. (Step 1) Seismic response analysis of the piping system. (Step 2) Evaluation for local strain of elbows. The simplified piping system model is adopted to solve the non-linear dynamic response both of the supports and elbows of the piping system in (Step 1). On the other hand, the piping system model with partially detailed elbow shell elements is applied to evaluate local strain behavior of the elbow in (Step 2).