3.4.4 Mechanical actuator

(1) The bumpy road system

The system is one of the mechanical actuator systems which obtains the energy for shaking from the kinetic energy of the rotation of the centrifuge itself. The system, at Cambridge University, involves a track with the desired wave form mounted over a portion of the wall of a pit housing a centrifuge. To commence the simulation, a wheel on the end of the centrifuge arm is quickly pushed outwards so that it will encounter and run along this track. The inward-outward motion of the wheel is translated into circumferential back-and-forth motion at the end of the arm.

B. L. Kutter, Centrifugal Modelling of the response of clay embankments to earthquakes, Ph D thesis, Cambridge University, 1982

F. H. Lee and A. N. Schofield, Dynamic Behavior of the Bumpy Road Shaking Sable System, Geotechnical Testing Journal, Vol. 12, No. 2, pp. 126-134, 1989

(2) The Cam-shaft shaking system

The system consists a cam-shaft and a high-powered motor which generate the vibrations. Figure shows the system shown in the Nikken Sekkei centrifuge. The bracket has an elliptical opening. The width of the opening is identical with the diameter of a bearing attached to the eccentric rod. The amplitude and frequency are controlled by the eccentricity of cam-shaft and rotation speed of the motor. The major capabilities of the system are the maximum payload of 125 kg, the maximum displacement of 0.25 mm and the maximum frequency of 50 Hz.

Ohishi, K., Saitoh, K., Katagiri, M., Katakami, N. and Terashi, M. (1995) : Comparison of embankment behaviors in static tilting and shaking table tests, Proc. of Earthquake Geotechnical Engineering, pp. 1075-1080.

Katakami, N., Saitoh, K., Katagiri, M. and Terashi, M. (1995) : Development of a mechanical shaker using a cam shaft, Proc. of 45th Annual Conf. of JSCE.

Kimura, T., Takemura, J. and Saitoh, K. (1988) : Development of a simple mechanical shaker using a cam shaft, Proc. of CENTRIFUGE 88, pp. 107-110.