Structural Bearings and Expansion Joints for bridges [Eng.CiviL]

All bridges are subjected to movements due to temperature expansion and elastic strains induced by various forces, especially due to traffic loads. In former times our bridges were built of stones, bricks or timber. Obviously, elongation and shortening occurred in those bridges, but the temperature gradients were small due to the high mass of the stone bridges. Timber bridges were small or had natural joints, so that the full elongation values were subdivided into the elongation of each part. On the other hand, the elongation and shortening of timber bridges due to change of moisture is often higher than that due to thermal actions. With the use of constructional steel and, later on, of reinforced and prestressed concrete, bridge bearings had to be used. The first bearings were rocker and roller bearings made of steel. Numerous rocker and roller bearings have operated effectively for more than a century. With the development of ageing-, ozone- and UV-radiation-resistant elastomers and plastics, new materials for bearings became available. Various types of bearings were developed with the advantage of an area load transmission in contrast to steel bearings with linear or point load transmission, where elastic analysis leads theoretically to infinite compression stresses. For the bearings the problems of motion in every direction and of load transmission were solved, but the problem of insufficient durability still exists. Whilst it is reasonable to assume the life of steel bearings to be the same as that of the bridge, the life of a bearing with elastomer or plastic parts can be shorter.

Author Günter Ramberger
Publisher IABSE, 2002
ISBN 3857481056, 9783857481055
Length 86 pages