Different types of bearings used in bridge structures
Bridge bearings stand for structural equipment or devices which are set up among bridge substructure and superstructure with the purpose of transmitting the functional load together with earthquake loads; wind loads; traffic loads; and superstructure self-weight.
Bridge bearings also allow for relative movements among superstructure and substructure, as for example, rotation movements and translational movements in horizontal and transverse direction.
Bearing is employed in building up the bridge structure. It is categorized as expansion bearings and fixed bearings. The first one allows for both translational and rotational movements while the second one allows for rotational and limited translational movements.
There are several types of bridge bearings which are frequently utilized in bridge construction. The details are given below :-
Various types of bearings for bridges: Sliding bearings, Rocker and pin bearings, Roller bearings, Elastomeric bearings, Curved bearings, Pot bearings, Disk bearings
Sliding Bearings for Bridges: Sliding bearing is made of two metal plates, generally stainless-steel plates, which slide corresponding to each other and therefore allows room for translational movement and lubricating material among them.
A friction force is produced in sliding bearing and it is enforced on substructure, superstructure and sliding bearing itself. So, it is necessary to arrange lubricant like polytetrafluoroethylene (PTFE) to reject generated friction.
As per guidelines by ASSHTO, the bridge span should be less than 15m to use sliding bearing in bridge structures. It is due to sliding bearing is not fully applicable if there is rotation movement in bridge.
While using sliding bearing, this span limitation can be avoided if it is employed in conjunction with other bearing types.
Rocker and Pin Bearings for Bridge Structures: Rocker stands for an expansion bearing that contains curved surface at the bottom. It adjusts translational movement and a pin at the top takes rotation movement into consideration.
Both rocker and pin bearings are vital parts of steel bridge structure. Rocker and pin bearing are taken into account when the bridge movement is suitably known and defined, because such bearings can allow for both translational and rotational movements in one direction only.
These bearings are susceptible to deterioration and corrosion, so inspection and maintenance should be performed on regular basis.
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