Input Motion Scaling for Seismic Evaluation of Rocking Components in Canadian Nuclear Power Plants

The rocking response of a freestanding rigid block depends on two parameters: its size and slenderness. In nuclear power plants, seismic qualification test reports for one component (the reference) can be utilized to seismically qualify another (the candidate) component by following item equivalency procedures based on form, fitness, and function of the candidate component. However, such item equivalencies for seismically qualified components are subject to the criterion given in the Canadian nuclear standards that does not allow more than 10% variation in mass and stiffness of the reference and the candidate component. While this rule works well for single or multi-degree-of-freedom mass-spring-dashpot systems, it should not be applied to rocking blocks because the dynamics of the two systems are fundamentally different. A large freestanding rigid structure, such as a scaffold, is difficult to test on a shake table due to its size. Testing a reduced scale model requires appropriate scaling of the excitation. All such applications demand scaling of the reference block excitation that suits the candidate block. Also, the concept of self similarity can be useful in determining the fragility excitation of a candidate component based on that of a reference component. This study investigates determination of seismic qualification excitation of a candidate component from that of a reference component based on self similarity.