Turner Beam Centrifuge

The Turner Beam Centrifuge facility at Cambridge has a balanced beam configuration that can carry a payload of 1 tonne and can accelerate it to 150g’s (150 g-ton machine). The working radius of the centrifuge is 4.125 m and the platform dimensions are approximately 1.0mx0.95m.

The earthquake actuation system on the centrifuge is the Stored Angular Momentum (SAM) based earthquake actuator. The capabilities of the SAM earthquake actuator are as follows:

  • 100 gravity operation;
  • strong earthquake motions (up to 0.4g at bedrock level);
  • earthquake frequency of choice in the range of 1 to 5 Hz or a frequency sweep from 5 Hz to 0 Hz (equivalent prototype frequency);
  • 0 to 1000 sec earthquake duration (equivalent prototype scale);
  • specialist model containers in the form of Equivalent Shear Beam or laminar model containers;
  • capabilities to model soil layers up to 40 m depth;
  • both saturated and dry models can be tested to enable study of liquefaction or Soil Structure Interaction problems.

The Turner Beam Centrifuge facility at the University of Cambridge

Foundations of special structures, both on-shore and off-shore, are tested with monotonic loading, cyclic loading or dynamic loading (earthquake loading in particular). The Schofield Centre plays a major role in disseminating standardised methods of centrifuge model making, particularly in the area of dynamic centrifuge modelling. New facilities are being developed to carry out model saturation using high viscosity pore fluids that are required to satisfy the scaling laws in dynamic centrifuge modelling.

The centrifuge facility has many in-flight and laboratory floor devices that were developed over a long period of time for soil characterisation. In-flight CPT’s have been used for in-flight soil characterisation and determination of boundary effects. Specialist calibration equipment has been developed and maintained in-house to guarantee the highest standards of instrumentation for high quality data retrieval. An automatic sand pourer has been commissioned to prepare sand models of specified density and soil stratification.

Hydraulic consolidation rigs have been added to the centre’s facilities to prepare clay soil samples of high quality with fully known stress history and user desired strength profiles. In addition, the hydraulic slip rings of the beam centrifuge and the electrical slip rings have been recently upgraded. A new fibre optic slip ring with very high bandwidth has been added to enable high speed communication between on-board computers and the control room. This enables high speed digital imaging to be carried out in-flight for the Particle Image Velocimetry for analyses of digital images and the deduction of the displacement and strain fields in soil models.

The centrifuge is supported by a mechanical workshop that maintains the centrifuge model packages and makes specialist equipment on a test-specific basis, by an instrumentation workshop that maintains existing instruments and by an electronic workshop that maintains and develops data acquisition systems and signal conditioning junction boxes.

Further, a 2D robotic actuator can apply horizontal, vertical and moment loads on structures in-flight. However, this actuator can only be used in non-earthquake tests at the present time.

Highlights

What's next

Series logo small   SERIES Concluding Workshop
  Joint with US-NEES "Earthquake Engineering Research Infrastructures

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