Design Rules of Elastomeric Bridge Bearings

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Design Rules of Elastomeric Bridge Bearings

Elastomeric bearings are laminated products that are reinforced internally with one or more steel plates and are chemically bonded during the vulcanization process. Elastomeric bearings are designed to meet all the relevant provisions mentioned at EN1337-3 at the ultimate limit state.

At the ultimate limit state, the strength and stability of bearings shall be adequate to withstand the ultimate design loads and movements of the structure. The Performance and durability of bearings designed according to this standard are based on the assumption that tolerances given in clause 6 of EN1337-3 are complied with.

 

Functional requirements

• Elastomeric bearings shall be designed and manufactured to accommodate translational movements in any direction and rotational movements in any axis by elastic deformation.
• Although elastomeric bearings are designed to accommodate shear movements, they shall not be used to provide permanent resistance to a constantly applied external shear force.

Sizes and shapes of laminated bearings

Bearing types are rectangular or circular but, for particular applications elliptical or octagonal (approximating to elliptical) shapes are acceptable.

Bridge bearing schedule according to EN 1337-3/ Table E.1

The purpose of a bridge bearing schedule is to list the information normally required for the design of the bearings for a particular structure.

This information should ensure that bearings are designed and constructed so that, under the influence of all possible actions, unfavorable effects of the bearing on the structure are to be avoided.

All designed bearings shall meet the following requirements:

1. Maximum design strain
2. Maximum tensile stresses in reinforcing plates
3. Stability criteria

They shall be evaluated after taking into account of the following points:

– Stability regarding rotation.
– Stability regarding buckling.
– Stability regarding sliding

4. Forces, moments, and deformations exerted on the structure

They shall be evaluated after taking into account the following points:

– The pressure at the contact surface between bearing and the structure.
– The force exerted on the structure by the bearing resisting translational movement.
– The force exerted on the structure by the bearing resisting translational movement
– The restoring moment due to the bearing resisting rotational movement
– Vertical deflection due to the vertical load.

Author

Salma Nassar
Technical Office Engineer
Ataya Construction Products,
New Cairo-Egypt.