Bridge bearings are structural devices installed between bridge substructures and superstructures. They transfer loads while allowing for movement. There are two main types: expansion bearings, which allow translational and rotational movement, and fixed bearings, which allow limited translational and rotational movement. Common bearing types include sliding, rocker and pin, roller, elastomeric, curved, pot, and disk bearings. Each has distinct structures, materials, and abilities to accommodate different load types and movements. Regular inspection and maintenance are important due to risks of corrosion and damage over time.

1. Bridge Bearings
Types of Bearings for Bridge Structures
And
Details

3. Bridge bearings are structural equipment or devices installed between bridge
substructure and superstructure to transfer the applied load including earthquake loads;
wind loads; traffic loads; and superstructure self-weight.
Bridge bearings also makes rooms for relative movements between superstructure and
substructure, for instance, rotation movements and translational movements in
horizontal and transverse direction.
Bearing used in the construction of bridge structure is divided into two major categories
namely expansion bearings and fixed bearings. The former permits both translational
and rotational movements whereas the latter allow rotational and limited translational
movements.

4. There are several types of bridge bearings which have been employed in bridge
construction which are discussed below.
Types of Bridge Bearings
and their Details
Different types of bearings for
bridges include:
a) Sliding bearings
b) Rocker and pin bearings
c) Roller bearings
d) Elastomeric bearings
e) Curved bearings
f) Pot bearings
g) Disk bearings

5. Sliding Bearings for Bridges
Sliding bearing consist of two metal plates, commonly stainless-steel plates,
that slide relative to each other and hence makes room for translational
movement and lubricating material between them as illustrated in Figure-1.
A friction force is generated in sliding
bearing and it is imposed on
substructure, superstructure and
sliding bearing itself. So, it may be
required to provide lubricant such as
polytetrafluoroethylene (PTFE) to
decline generated friction.It is specified by ASSHTO that sliding bearing cannot be used unless the bridge
span is smaller than 15m. This is because sliding bearing cannot be purely used
if the bridge experiences rotation movement.
However, the span restriction for sliding bearing utilization can be disregarded
when it is used in combination with other bearing types.

6. Rocker and Pin Bearings for Bridge Structures
Rocker is an expansion bearing composed of curved surface at the bottom,
which accommodate translational movement and a pin at the top makes room
for rotation movement as illustrated Figure-2 and Figure-3 in detail.

7. Pin bearing is a fixed bearing that make room for rotation movement through the
application of steel pin. It has similar structure and component like rocker
bearing apart from the bottom of pin bearing which is flat and fixed to the
concrete pier, as can be observed in Figure-4.

8. Both rocker and pin bearings are mainly employed in steel bridge structure.
Rocker and pin bearing should be considered when the bridge movement is
adequately known and described, since such bearings can make rooms for both
translational and rotational movements in one direction only.
These bearings are likely to suffer deterioration and corrosion, so it is necessary
to conduct regular inspection and maintenance.

9. Roller Bearings for Bridges
Roller bearing can be used in the construction of reinforced concrete and steel
bridge structure. There are two main configurations including single roller
bearing which is composed of one roller placed between two plates and multiple
roller bearing that consist of several rollers installed between two plates.
The former as shown in Figure-5 can accommodate both rotation and translation
movement in longitudinal direction and it is cheap to manufacture but its vertical
load capacity is limited.
In contrary, the latter as shown in Figure-6 can make room for translation
movement only and rotation movement can be accommodated if rollers are
combined with pin bearing. Multiple roller bearings are expensive and support
considerably large vertical loads.
Regular inspection and rehabilitation should be conducted since roller bearing
are susceptible to corrosion and damages.

10. Multiple Roller Bridge BearingSingle Roller Bridge Bearing

11. Elastomeric Bearings for Bridge Structures
It consists of elastomer manufactured from synthetic or natural rubber and can
take both translation and rotation movements through elastomer deformation.
The ability of elastomer to carry large vertical loads is because of reinforcement
provision that prevents lateral bulging of elastomer.
There are number of elastomeric bearing pads classified based on types of
reinforcements used. For example, steel reinforced, plain, fiberglass reinforced
and cotton duck reinforced elastomeric bearing pads.
Strength and response of each type is different, steel reinforced elastomeric bearing is
the strongest one and plain elastomeric pad is the weakest.
Elastomeric bearing is neither expensive nor requires considerable maintenance, that
is why it the most desired bearing type. Figure-7 show details of elastomeric bearing
and its application in bridge structure.

14. Elastomeric Bearing with Outer Steel Plates

16. Curved Bearings for Bridges
It consists of two curved plate that match each other as shown in Figure 8. If
curved bearing is cylindrical, then it only accommodates rotation movements.
However, both rotation and translational movements can be dealt with if
curved bearing is spherical.
Due to the fact that both gravity loads and curved geometry generate lateral
resistance against and consequently lateral movement would be limited, that is
why polytetrafluoroethylene (PTFE) slider is adhered to the bearings in order
to make rooms for lateral movements. Details of curve bearings can be seen
in Figure-8.
Spherical Bearing for Bridges

17. Pot Bearings for Bridge Structures
As shown in Figure-9, pot bearing consists of elastomeric disk confined in a pot,
steel piston that is properly tailored into the pot wall and flat sealing rings which
keeps elastomeric inside the pot.
Pot bearing can support considerable vertical loads and it is commonly
transferred through steel piston to the elastomeric disc which is almost
incompressible. As far as lateral load is concerned, it is transferred as the steel
pistol moves toward pot wall.
Translational movement is limited in pure pot bearing that is why PTFE are
introduced to the sliding surface to make rooms for translation movement.

19. Disk Bearings for Bridges
Different components of disk bearing are shown in Figure-10 in detail. Rotation
movement is accommodated through the deformation of elastomer whereas the
translation movement is considered through the application of PTFE slider.
The utilized elastomer should be
adequately hard to support vertical
loads without suffering large
deformations and sufficiently
flexible to allow rotational
movement.
Both vertical loads and lateral
loads are supported by
elastomeric disk and metal ring in
the center of the bearing
respectively.