Study on Vertical Motions by Rocking Responses of Reactor Buildings

Abstract

Earthquake observation records were observed in reactor buildings of Kashiwazaki-Kariwa Nuclear Power Plant Site during the Niigata-ken Chuetsu-oki earthquake in 2007 (NCO). Some studies on the seismic response and simulation analyses were performed to investigate dynamic characteristics of the structures. In particular, it was clarified that the vertical motions of the reactor building of Unit 6 were greater than those of adjacent reactor buildings of Unit 5 and Unit 7. This paper discusses the causes of this by earthquake observation records and simulation analyses of the reactor buildings. In general, seismic response of vertical motions is relatively well-simulated using lumped mass model with stick elements that have vertical stiffness and with the soil spring between the basemat and support ground. However, vertical motions are influenced by rocking motions with horizontal response in some cases. This paper focuses on relationships between the vertical responses and the vertical motions induced by the rocking motions with simulation analyses and observation records during both NCO earthquake and aftershock of NCO. The reasons why the vertical motions of the reactor building of Unit 6 were larger are discussed.

3D FEM Soil-Structure Interaction Analysis for Kashiwazaki–Kariwa Nuclear Power Plant Considering Soil Separation and Sliding

“…Also, Hijikata et al (2011) showed that the SSI results considering the nonlinearity behavior due to the separation and sliding of soil from sidewalls using joint elements could sufficiently explain the recorded seismic data. Kikuchi et al (2012) focused on the vertical motion induced by the rocking motion due to the horizontal motion at the observation points, and clarified that the vertical motion of Unit 6 RB becomes larger than that of the other RBs from the results of simulation analysis from Units 5 to Unit 7 RBs. However, such studies typically included an additional simplification of representing the structure by a LMSM, which does not fully consider the effects of SSI for simultaneous three directional inputs in two horizontal and one vertical directions on the local responses of the maximum acceleration responses in the structure.…”