The natural frequency F is calculated using the formula

where K is the measured dynamic stiffness of the bearing at a pre-determined load and m is the mass carried by the bearing. Bearings are made from natural rubber because of its superior dynamic properties and excellent fatigue behaviour. The dynamic evaluation of the bearing material has been carried out by independent test laboratories. (Rubber Consultants - MRRDB a unit of the Malaysian Rubber Research and Development Board, Hertford.)

From tests, the Damping Ratio has been measured as 0.028 and Loss Factor has been measured as 0.056 for SKV bearings. Recommended temperature operating range: -30 to +70 degrees C.

BS 6177 gives engineers useful information when considering the installation of bearings for anti-vibration purposes. Items such as fail safe devices, wind loading restraint, fire protection, replacement, etc., are also covered.

Bearings are always used in groups rather than one large 'area' of bearing material. This ensures the optimum performance is gained together with other advantages such as ease of installation. For example, a pile cap with a vertical load of 8000 kN would require 16 bearings of 250mm square plan dimensions. The pile head may therefore have to be flared to give sufficient area for bearings, fail safe devices and dowel bars for side restraint.