Jumat, 05 April 2013

Bridge Bearing Pad

Bridge Bearing Pads

Bridge Bearings Pads are devices which transmit the load from the superstructure to the substructure and to accommodate movements and displacements. Bearings Pads are built to withstand loads and simultaneous deformation in any direction, while also allowing for minor rotations in any of the bearing's axes.Rubber bearings pad can be made entirely of rubber or can be reinforced with special sheet steel to increase capacity and transversal strength.
Types of Elastomeric Bearings
Plain Elastomeric Bearing containing no steel plate.
Laminated Elastomeric Bearing containing steel plate laminated bonded to rubber.
Laminated bearings are recommended for most cases since they give more reliable performance and better stability.
Plain pad and strip bearings are suitable only for low loads and small shear strains.


The Function of Elastomeric Bearings Pads
Structures are subjected to imperceptible displacements and rotations that have to be accommodated to protect the structure and surrounding infrastructure. The most common causes of movement being:
Temperature changes
Traffic movement and braking
Wind
Shrinkage and creep
Foundation movement
Post stressing
The function of the bearing pad is to safely accommodate the various movements and rotations as well as supporting the weight of the structure and to transmit the load through to the structures foundation.
Elastomeric Bearings Pads are designed to accommodate three types of movement
Vertical
Shear
Rotation
To transfer the load from the superstructure (both vertical and horizontal) to the substructure. Bridges with span less than 10m do not normally require any bearings.

To accommodate translational movements (expansion and contraction) e.g. movement due to temperature (can be large in steel bridges, up to 300mm); due to dead load & live load especially sloping road; shrinkage and creep etc.

To accommodate rotational movements of deck girders. Rotation occurs as the deck deflect under load. Also, some relative rotations occur in composite section due to different properties of concrete and steel. Differential settlement may also cause some rotational movement.

To limit forces transmitted to the substructures by suitable design.

To provide damping of vibrations and minimize effects of impact loading in case of elastomeric bearings.

1 komentar:

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