2021 Volume 21 Issue 5 Pages 5_161-5_183
When creating input ground motions based on the response spectrum in the seismic design for nuclear facilities in Japan, for horizontal components, simulated ground motions, which are composed of two mutually orthogonal components, are to be created using one target response spectrum. In this case, the characteristics of two ground motions are distinguished by the randomness of the phase angle given by the uniformly distributed random numbers and/or the difference in the phase characteristics of the two different components of the observation records. On the other hand, according to the US Nuclear Regulatory Commission standards, when performing seismic response analysis for nuclear facilities using the method of simultaneous input of three earthquake ground motion components, it is stated that the three components should be shown to be statistically independent of each other, and an absolute value for correlation coefficient which was proposed by Chen (1975) is introduced as a criterion. In this paper, focusing on the correlation coefficient by Chen (1975), we analyzed the correlation coefficients between two orthogonal components of strong-motion records observed in Japan after 2000, and performed statistical analyses of these correlation coefficients and analyzed the impact of various earthquake-related parameters upon them. In addition, we actually created simulated ground motions via a common practice based on the response spectrum, and analyzed their correlation coefficients.
