Bearings of bridge | Types of bearings | Bridge Engineering | Transportation Engineering

 Bearings are the device which are provided on the top of abutment and piers to allow free expansion, contraction and deflection of bridge superstructure.

Function of bridge:-

• To allow or longitudinal movement due to the change in temperature.
• To distribute to the load received through the ends of bridge girder.
• To resist horizontal forces developed due to the application of brakes to the vehicles. 
• To take a vertical movement due to the sinking of the supports.
• To simplify the procedure in design. 

Types of bearing for RCC industrial Bridge.

1. Fixed Bearing:-

The bearing which does not permit any longitudinal movement of the bridge girders is known as the fixed bearing.

These bearings usually allow angular moment of deflection of the girder.

Fixed bearings are classified as:-

A. Shallow and fixed plate bearing:-

       This is the simplest type of bearing consists of a flat rectangular steel plate attached to the under slide of the lower flange of the bridge girder. 

B. Deep cast base bearing:-

       This is a modified form of fixed plate bearing, this type of bearing is consist of a sole plate that is attached to the underside of the girder.

 Suitable for a span up to 20 m of steel girder. 

C. Rocker Bearing:-

      This type of bearing consists of a top shoe and a bottom shoe and in the middle of the rock pin is inserted. 

Suitable a span exceeding 20m.

2. Expansion Bearing:-

       The bearing which allows longitudinal movement of the bridge gi is known as expansion bearings.

Expansion bearings are classified as:-

A. Slide plate bearings:-

       This is the simplest type of bearing consists of a sole plate attached to the underside of the bridge girder which is free to slide over the wall plate. 

 Suitable for span 12 to 20m.

B. Dip cast base with curved plate bearing:-

         This type of bearing consists of a sole plate which is connected to the bottom edge of the end of bridge girder. 

Suitable for span 12 to 20m.

C. Rocker bearing with curve base:-

       The bottom shoe is provided with a curved bottom which offer minimum resistance to the longitudinal movement of the bridge girder. Thus this type of bearing allow for deflection and expansion of bridge girder with a reduced horizontal force.

D. Rocker and roller bearing:-

        This type of bearings consists of a Rocker bearing having its bottom shoe registering on the number of steel roller which in turn roll on honey combined bed plate, anchored to the top of masonry or concrete abutment.

 Suitable for span more than 20m.