In the engineering education, effective experiments are necessary to understand the phenomena in addition to the theoretical learning. Also in the earthquake engineering, it is difficult to understand the theory of the soil and building vibration without appropriate experiments due to its complexity including the concept of time and frequency. Thus the effective teaching materials are necessary for the architectural education.
In this study, a new shear vibration model using permanent magnets and ball bearings was developed. The model is constructed by stacking the layer consisting of the wooden board and permanent magnets via ball bearings alternatively. The restoring force appears as the horizontal component of the magnetic interaction between the magnets lower and upper the bearings. The model has the stable performance and the long natural period enough to visually recognize comparing to existing materials. Additionally, the model has a lot of features: inexpensiveness of materials, variable natural period, visible shear wave propagation, multiple applications to represent soil and building structures, and so on.
In this paper, basic characteristics of the model are revealed by the theoretical analysis, the static and dynamic tests, and the vibration experiment. The results obtained are as follows:
1) The restoring force shows almost linear and nonlinear characteristics for small and large relative story displacement, respectively. This is the same tendency as the actual soil and buildings. The stiffness of the model varies with the size of the bearing, the arrangement of the magnets, or the number of the magnets. High toughness is realized by using iron ball bearings, since they are magnetized between the lower and upper magnets due to high magnetic permeability.
2) The damping ratio of the model is almost constant with respect to the displacement amplitude. This is the same tendency as the actual soil and buildings, similarly to the restoring force characteristics. However, the effect of rolling resistance of the bearings becomes dominant for small displacement amplitude, causing the increase of the damping ratio.
3) By constructing the multilayered model simulating the high-rise building or the shear soil column, it becomes possible to visually observe the shear wave propagation in the model.
