BRIDGE BEARING TYPES (BRIDGEWIZ)

                                                                                                                                                        
           
                                                          

 AASHTO-LRFD (METRIC)

FUNCTION OF BEARINGS: Bearings are typically placed at the interface of substructure and superstructure. Functions are:

1.-Transmit load (self-weight, traffic loads and many more) between the substructure and superstructure.

2.- Allow relative movement (translation and rotation) between the superstructure and the substructure. These movements can develop due to temperature, creep, shrinkage and more.

                                                                                

                                                                                                              

 BEARINGS ARE MAINLY IN TWO  CLASSES:

1.-ELASTOMER  BASED BEARINGS: This deformable type bearings are typically allow  deformations in many cycles and design is governed by gradual deterioration rather than sudden failure under single load. Common type is reinforced elastomeric bearing. These bearings usually carry low vertical load.

2.-METALLIC BEARINGS: These bearings do not allow much mistakes in installation and can fail suddenly under a single load or displacement. These bearings can carry high vertical load. Common types are rocker bearings, spherical bearings, nad pot bearings.

SELECTION OF BEARINGS: In selection of bearings, the following items need to be known  under service and strength limit state:

1.- loads such as vertical and horizontal

2.-movements such as transnational or rotational

3.- construction tolerances

4.-maintenance cost

TYPICAL BEARING CAPACITIES FOR COMMON TYPES

Most data is gather from Bridge Engineering Handbook, CRC Press and experience gained thru bridge projects

TYPE - LOAD RANGE ( kN)- TRANSLATION RANGE(mm)- ROTATION (rad)- INITIAL $-M$

    A        200 TO 3500                         0-200 mm                                  0.04 rad              LOW      LOW

    B      1,200  TO 10000                    0-200 w/slider                            0.02 rad               MOD    HIGH

    C      1,200  TO  10000                    0>200w/slider                           >0.04 rad             HIGH    MOD

    D             0  TO  10000                    25-200                                            0                       LOW   MOD

    A=STEEL REINFORCED ELASTOMERIC  BEARING

    B= POT BEARING

    C= SPHERICAL BEARING

    D= PTFE SLIDER

PARTS OF A ELASTOMERIC  BEARING

PARTS OF METALLIC  BEARINGS

EXAMPLE:

THE SAME BRIDGES USED IN THE EXAMPLE WILL BE EVALUATED FOR THE BEARING SELECTION

SUPER STRUCTURE WEIGHT PER UNIT METER:

EXAMPLE:

SUMMARY OF VERTICAL BEARING FORCES  (kN)