The effect of rocking excitation on the dynamic behaviour of a Nuclear Power Plant reactor building with base isolation

Past research has shown that for seismically isolated Nuclear Power Plants (NPPs) rocking has little effects on the peak bearing deformation or axial forces. Recently however, a new class of special buildings has been considered for seismic isolation, namely Generation 3+ and 4 Nuclear Power Plant reactor buildings. The safety issues related to NPPs suggest an assessment of previous results also for these new structures. Since rocking motion can be triggered by earthquake surface waves, this work compares the effects of two different description for earthquake motions through coherency functions on a simplified model of the NPP reactor building set on laminated metal-rubber bearings. The model is subject to synthetic generated accelerograms which satisfy a modified Kanai-Tajimi power spectral density. The laminated metal-rubber bearings are modelled with a non-linear cyclic force-displacement law for the horizontal displacements and are vertically linearly elastic.