What is a bridge expansion joint?
A bridge expansion joint is a construction that spans the movement joint in a bridge, viaduct or road deck. It sits between the abutment and the bridge deck or between two bridge decks. Its purpose is to let traffic cross the joint safely while the structural parts can move relative to each other. In Dutch it is called a voegovergang.
Why do bridges move?
- Temperature: concrete and steel expand when warm and contract when cold. On long bridge decks this adds up to many centimetres.
- Shrinkage and creep: young concrete still shrinks and deforms under load in its first years.
- Traffic loads: axle loads, braking and vibrations make the structure move slightly.
Without an expansion joint, these movements would lead to cracks, pushed-up edges or damage to the bearings.
Types
- Rigid expansion joints: made of steel, concrete or plastic. Well-known types are the finger joint (interlocking steel fingers) and the modular joint (several steel beams with rubber profiles between them) for large movements.
- Flexible expansion joints: made of an elastic, bituminous compound in the asphalt. Suitable for small movements.
- Rubber profiles: a steel edge profile on each side with a rubber seal between them, for medium movements.
Points of attention
- Watertightness: leaking joints carry water and de-icing salt to the bearings and the concrete below. This is a common cause of damage.
- Noise: rigid expansion joints can make a banging noise when driven over. Low-noise versions exist.
- Maintenance: dirt, loose bolts and worn rubbers must be dealt with in time. Expansion joints are inspected periodically and have a shorter service life than the bridge itself.
Related terms
- Finger expansion joint
- Expansion joint
- Thermal expansion
- Abutment
- Viaduct
- Roller bearing
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