Conventional estimating method of earthquake response of mechanical appendage system installed in the nuclear structural facilities

In a previous paper, the statistical characteristics of the maximum response of the appendage system were estimated by using a simplified coupled model and many typical earthquake records. Attention was particularly focused on the least feasible condition for the appendage system where the fundamental natural period of the appendage system (Tsub(a)) coincides with that of the supporting system (Tsub(s)) and a conventional estimating method for such an extreme case was presented. This method is developed for general case where Tsub(a) does not coincide with Tsub(s) in this paper. The response properties of the appendage system are represented by the 'Floor Response Amplification Factor' (FRAF), the ratio of the maximum response of the appendage system to the response spectrum for the supporting system. The expected values of the FRAF are estimated taking mass ratio γ, damping ratio of the appendage system hsub(a), Tsub(s) and Tsub(a)/Tsub(s) as parameter. Under the condition of Tsub(a)/Tsub(s) <= 1.5, the fluctuation of the FRAF with respect to Tsub(s) has become very small for fixed values of γ, hsub(a) and Tsub(a)/Tsub(s). Then it is desired that the FRAF can be obtained only through γ, hsub(a) and Tsub(a)/Tsub(s). The expected values of the FRAF for any realistic case can be represented in tabular form. They are also shown by a tripartite diagram from which the FRAF for acceleration, velocity and displacement can be estimated simultaneously. (orig.)