Elastomeric bearings have been used in the UK for about 30 years without showing any significant deterioration. They are an economic method of supporting bridges and provide low shear and rotational modulus. This report summarises the results of research on the properties of elastomeric bearings in ambient and low temperature environments. Further research is in hand on the structural effect of changes in bearing stiffness on bridges. Sample sheets of typical elastomers were tested as specified in the UK design code BS 5400: Part 9, to obtain an understanding of the test methods. Also the effect of low temperature stiffening was investigated on sample sheets, full-size bearings and test-pieces cut from the bearings. Large increases in modulus were measured in all cases, but there were differences in behaviour between the three types of specimen. BS 5400: Part 9 specifies compression set measurements for determining the effect of low temperature stiffening. This report recommends that modulus measurements, using samples cut from the body of the bearing, would give a more accurate indication of service performance. The modulus should not increase by more than a factor of three after 24 hours at -25 degrees C. Nine sample vulcanizates were supplied in sheet form by elastomeric bridge bearing manufacturers for testing. Only three were found to comply with all of the requirements in BS 5400: Part 9. However, if the ageing resistance requirement is relaxed five would comply in all the other respects. (A)

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