8/23/2024
Know All About Bridge Bearing
A bridge Bearing is a part of a bridge that provides a resting surface between the bridge piers and the bridge deck.
It is a structural device that helps transmit the load from the superstructure, such as the bridge deck (top of the bridge), to the substructure, such as piers or abutments (supporting the bridge deck). Bridge bearings are designed to control movements and rotations and reduce structural element stresses.
The main purpose of a bridge bearing is to allow controlled movement and reduce the combined stresses. Thermal expansion and contraction, creep, shrinkage, and fatigue, among others, can cause movements on the bridge. In addition, external factors, such as soil compaction and seismic activity increase displacements and rotations. Therefore, in the process of designing structural elements, they must be checked.
In this blog we will understand what are bridge bearings, bridge bearing types, elastomeric bearing in bridges, elastomeric bearing in bridges, why bearings are used in bridges, how many types of bearings are in bridge, bearing plate for the bridge that Deevin Seismic Systems Pvt. Ltd manufactures.
Why are Bearings used in Bridges?
So let’s understand why bearings are used in bridges and what are their functions. Here are some reasons are as follows:
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Bridge bearings allow sideward movements due to changes in temperature, moments in traffic, wind, sliding and shrinkage, movement in foundation, seismic actions, dynamic forces, etc.
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Load transmission to the foundation of the substructure.
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Allows the rotation of the girder
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Supports vertical loads
Now that we have understood why bearings are used in bridges, let’s understand what are bridge bearing types.
Bridge Bearing Types
Let us explore how many types of bearings are in bridge we have.
Bridge bearings are usually made of steel, elastomeric materials, or a combination of both. Bridge bearings help bridge parts to ease pressures that can be formed in the bridge structure by moving them freely.
The bridge bearing type used will depend on several factors, including expected load weights, span length, and available space to access the bearing. The bridge bearing types most often used in modern bridges include elastomeric bridge bearings, Moderna bearings, spherical bearings, rocker bearings, roller bearings, and plain bearings.
Several bridge bearings types are commonly used. The decision to use the appropriate type is based on various factors, including bridge span, load conditions, and performance specifications.
The most traditional bridge bearing type was very simple as it consisted of two bearing plates for the bridge resting on each other. Modern bridge bearings are made mainly of Elastomer.
Another category of bridge bearing type is mechanical bridge bearings. There are several variants of mechanical bridge bearings, for example, Pivot Bearings (which include the rocker bearing and roller bearing) and =Fixed Bearings, which allow rotation, but not other forms of movement.
Elastomeric Bearing in Bridges
The most common bridge bearing type used is elastomeric bridge bearings. Made up of rubber, it does not include any moving components. These bearings are convenient to manufacture and do not require regular maintenance, unlike other types of bearings that incorporate moving parts. Elastomeric bearings in bridges can be reinforced with steel reinforcements if necessary to increase their load capacity.
Laminated Elastomer Bearings
Laminated elastomer bearings can adapt to the movement in any direction and the rotational movement of any axis by elastic deformation. They are usually used where bridges are sensitive to high loads, high translations, and rotations. Alternating layers of steel and rubber are vulcanized together to achieve the desired load capacity. Laminated bearings can be rectangular or circular according to the requirements at the level of the abutments.
Plain Elastomeric Bearing Pads
Plain Elastomeric Bearing Pads are solid rubber blocks without steel reinforcement bearing plates for the bridge. They are usually not used in bridges. They are used mainly where there are low-pressure loads and static conditions.
Plain elastomer bridge bearings are simple and inexpensive rubber separation strips, capable of withstanding compressive loads and providing limited translational motion and rotational capability. They have various applications in prefabricated structures.
Guided Elastomeric Bearing in Bridges
This type of special bearing bushing consists of upper and lower load plates with a guide to limit movement in the required direction. The upper and lower load bearing plate for the bridge are hot vulcanized on the rubber. Anchor bars are also supplied in load plates for anchoring to bridges according to BS standards. Rubber pads can be smooth or reinforced depending on the load conditions in force.
Sliding Bridge Bearings
Sliding-type bridge bearings are provided when it is necessary to obtain a higher translation concerning the available surface area in the stop, especially in large shopping malls or airports where the spans are very large and with higher relative translations.
PTFE sheets with mirror-finished stainless steel bearing plate for the bridge are used to achieve the desired result of higher translations. PTFE is chemically bonded or fixed with adhesives on top of the pads.
Plain bearings are fixed against all translations unless they are used with a PTFE sliding surface. The shoe is deformable but almost incompressible, and the pot bearing bridge has a large reserve capacity against vertical loads.
Pot Bearings
Pot bearings are a type of bearing that can support heavy and larger loads, rotations, and translations in compact spaces.
Pot bearings are the most preferred bridge bearings when it comes to supporting rotations that are very large. No matter on which axis the rotation takes place, it can accommodate by deforming the elastomeric bearing.
The bearing consists of a metal piston supported by an unreinforced elastomer disc confined to a metal cylinder to allow rotational movement around any axis in the horizontal plane and to support and transmit a vertical load.
The pot bearing bridge can be equipped with a sliding assembly (with or without constraint in the form of the guide according to a desired direction to be supported and horizontal force transmission) consisting of a stainless steel bearing plate for the bridge fixed to a metal support plate that slides in a horizontal plane on a sliding material confined in recesses on the piston which are to be called sliding/guided bearings.
Depending on the desired degree of freedom, the vase bearings can be of three types as follows:
Fixed Bearing
The fixed bearing is fixed in all directions. Under loads, the elastomer support cushion behaves like an incompressible liquid in a confined space, which allows rotation around any axis.
Free Rolling
The free-sliding ball bearing can move in all directions. The additional PTFE and stainless steel sliding surface between the piston and the sole creates a bearing assembly that allows horizontal movement in both directions.
Guide Support Element
A guide support element with a steel guide edge can only be moved in one direction. The stainless steel and PTFE guide elements further reduce the coefficient of friction and the guide support element is preferable for relatively low horizontal loads.
Spherical Bearings
Spherical bearings consist of a pair of matching concave and convex spherical steel support bearing plate for the bridge connected by a lower friction sliding interface that allows for rotation by sliding in a curve. To provide translation Capacity, bearings are combined with flat sliding elements. Depending on the desired degree of freedom, spherical bearings can be of three types as follows:
Fixed spherical bearing allows only rotations, any longitudinal or transverse movement is limited.
The spherical bearing with an edge steel guide adapts to unidirectional movements.
Free sliding spherical bearing can slide in all directions.
Why choose Deevin Seismic Systems for all your bridge-bearing needs?
Deevin Seismic Systems Pvt. Ltd is a Leading manufacturer of structural bridge bearings and bridge expansion joints, geo-composite and geo straps, and pre-stressing and post tensioning systems.
Deevin Seismic Systems Pvt. Ltd, is an ISO 9001:2015 certified and NABL accredited company, having a state of art corporate office & manufacturing unit of 12,402 sq. Mtr. with an in-house Design and testing laboratory in the Mandideep Industrial area, which is 25 km away from Bhopal, well connected via Road, Rail & Air.
We design, manufacture, and install custom-made heavy mechanical bridge bearings.
We also provide turnkey solutions that save time and money by reducing the number of interfaces between procurement and construction.
We can manufacture bridge bearings on a large scale for extensive projects.
Deevin Seismic Systems Pvt. Ltd has designed and developed a comprehensive catalog of bridge bearings that meet all requirements of our clients. Bearing production can be customized to meet even the most difficult cases.
Pot bearings bear high vertical loads, Elastomeric bearings in bridges are the most economical solution for low vertical loads, Spherical bearings bear high vertical and horizontal loads with high rotational capacity around each axis, and Lead rubber damping ensures seismic isolation with integrated damping.
Our bridge bearings are used worldwide on a large number of prestigious projects due to their innovative and easy-to-use design, reliability, and durability.
In-house Lab for Testing of our Bearings
In-house manufacturing test of every bridge bearing is done in the presence of our highly professional team.
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