Precompression of the box


CDM-CAS box


CDM-CR bearing

CDM-CAS-BOX Pre-Compressed Elastomer Boxes are used to isolate buildings where the required natural frequency is 6Hz to 10Hz. They consist of elastomer pads inside reinforced steel boxes which are pre-compressed to a specified load.
The advantages of pre-compressed elastomers over simple elastomers are as follows:

The elastomers are pre-compressed to a percentage of the overall supported mass (say 80%) therefore minimising deflection during construction (deflection only occurs after the precompression has been exceeded) - this is especially important when low frequency solutions are required as this results in high deflections

The boxes can be neutralised, replaced or inserted after construction. It is essential, however, that all boxes are accessible and this should be considered in the scheme design phase of the building.