ABSTRACT A vibration isolation system using spring units and visco ...

5. SHAKING TABLE TEST OF THE ISOLATED BUILDING MODEL
5.1 Shaking table test
5.1.1 Model
The model was designed to have the same natural frequency and the same damping ratio as the
real building. The isolation system was composed of six springs and four dampers. The
accelerations at the top and bottom of the frame, and the relative displacement between the
bottom of the frame and the top of the shaking table were measured. Fig. 15 shows the model and
measurement points.
5.1.2 Loading
(1) Sinusoidal sweep excitation
The model was shaken by a sinusoidal sweep wave in the direction of the longer side (X), the
shorter side (Y) and the vertical direction (Z). The acceleration was 20 gal and the range of
frequency was 0.3 Hz - 10.0 Hz.
(2) Seismic excitation
Taft wave, El Centro wave and Hachinohe wave were used for the input of the shaking table. For
each seismic wave the model was shaken in Y direction only, Y and Z directions combined and all
three directions.
5.2 Analytical method
The analytical method of the shaking table test was the same as the one explained already above.
The analysis model is shown in Fig. 16. The upper structure was assumed to be a shear beam
element. The weight of the model was concentrated in two separate masses at the top and the
bottom. The material properties of the analysis model were based on the results of a random noise
test without the isolation system.
4-parameter model
Longitudinal cross section Lateral cross section
Fig. 15 Specimen Fig. 16 Analysis model