Bell-ring vibration response of nuclear containment vessel with attached masses under earthquake motion

Abstract There are two types of vibrations, designated as ‘beam-type’ and ‘bell-ring type’ occurring with axisymmetric thin shell nuclear containment vessel. Up to this time, the seismic analysis for such thin axisymmetric shells has mostly been carried out only for the ‘beam-type vibration’ because the response participation factor for the ‘bell-ring type vibration’ under seismic motion is zero when the shell structure is perfectly axisymmetric. However, as with nuclear containment vessels, when the thin axisymmetric shell has several attached heavy masses such as the equipment hatch or the manholes, the resulting seismic response of bell-ring type vibration is unexpectedly large and becomes remarkably more important than the beam-type vibration. For the seismic analysis of bell-ring type vibration an approximate uncoupled analysis using the natural mode shapes of unweighted perfect axisymmetric shell has been advocated on the assumption that the effect of the attached mass on their natural modes might be very small. However, application of this method to some models showed that the response of bellring type vibration calculated was noticeably smaller than the experimental results. In this paper we show the seismic response analysis of the bell-ring type vibration coupled with the beam-type vibration through the attached masses with the new consideration. These results show good agreement between the theoretical calculation and the experiment.