A study of the sensitivity of bridge response to changes in non-geometric parameters was carried out using mainly the El Centro 1940 N-S earthquake component. The response of bridge decks supported on elastomeric or a combination of elastomeric and lead-rubber bearings is computed. The effects of variations in the following parameters on response were studied;
 a) a range of bearing properties,
 b) a range of abutment stiffnesses and abutment weights,
 c) different earthquake records and
 d) the effect of seismic waves propagating at various velocities and angles of attack with respect to the bridge centreline.