Jumat, 01 Februari 2013

Elastomeric Bearing Pads

Elastomeric Bearing Pads are devices which transmit the load from the superstructure to the substructure and to accommodate movements and displacements. Bearings are built to withstand loads and simultaneous deformation in any direction, while also allowing for minor rotations in any of the bearing's axes. Gada Bina Usaha bearings can be made entirely of rubber or can be reinforced with special sheet steel to increase capacity and transversal strength.

Types of Elastomeric Bearing Pads :
1.Plain Elastomeric Bearing Pads containing no steel plate.
2.Laminated Elastomeric Bearing Pads 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 Bearing 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 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 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.

Gada Bina Usaha can produce elastomeric bridge bearings in accordance with all of the following international standards: American AASHTO, The elastomer used in the moulding process can be polychloroprene (neoprene), natural rubber or SBR depending on specification requested

Test Equipment For Elastomeric Bearing Pads
Tensile Test Machine
Oscillating die Rheometer
Hardness Tester
Compression set apparatus - deflection
Specific Gravity Balance
Thickness Gauge : 5mm and 25mm range
Hot air Oven (250°C)Following tests can be performed at our laboratory
Hardness
Compression Set
Tensile Strength
Bonding Strength
Elongation at break
Load V/S Deflection test
Material tests can be done and Certificates issued based on test values.