For the previous 10 years the SAM actuator had been utilised for all dynamic centrifuge tests and despite still performing well, it has limitations in terms of earthquake input motions that can be generated. The SAM actuator is not capable of firing earthquakes with multiple frequency components, nor can the acceleration magnitude be varied within a single earthquake event. Hence there was a requirement to develop a new 1-D actuator capable of firing more realistic representations of historic earthquakes recorded in the field such as El Centro motion or Kobe motion. The servo-hydraulic shaker uses a very fast acting servo valve to control the release of oil, stored at high pressure (280 bar) in accumulators, to drive the actuators connected to a shaking table. A hydraulic power pack and high pressure slip rings allow the accumulators to be recharged after each earthquake so that multiple earthquakes can be fired without having to stop the centrifuge.
By October 2010 the new shaker was ready to undergo initial tests in the Centrifuge and by the start of 2013 it is hoped the shaker will be fully operational. Further details are described in:
Madabhushi, S.P.G., Haigh, S.K., Houghton, N.E. and Gould, E., (2012), Development of a servo-hydraulic earthquake actuator for the Cambridge Turner Beam Centrifuge, accepted by International Journal of Physical Modelling in Geotechnics, Thomas Telford, London.