Expansion joint

An expansion joint or movement joint is an assembly designed to safely absorb the heat-induced expansion and contraction of construction materials, to absorb vibration, to hold parts together, or to allow movement due to ground settlement or earthquakes. They are commonly found between sections of buildings, bridges, sidewalks, railway tracks, piping systems, ships, and other structures.

Building faces, concrete slabs, and pipelines expand and contract due to warming and cooling from seasonal variation, or due to other heat sources. Before expansion joint gaps were built into these structures, they would crack under the stress induced.

Control joints (often confused with expansion joints) are cut into the concrete or asphalt, and are different from expansion joints. Control joints are cut into the pavement at regular intervals to allow cracking to occur in a controlled fashion. Road control joints may be sealed with hot tar, cold sealant (such as silicone), or compression sealant (such as rubber).

Bridge expansion joints are designed to allow for continuous traffic between structures while accommodating movement, shrinkage, and temperature variations on reinforced and prestressed concrete, composite, and steel structures. They stop the bridge from bending out of place in extreme conditions, and also allow enough vertical movement to permit bearing replacement without the need to dismantle the bridge expansion joint. There are various types, which can accommodate movement from 30 to 500 millimetres (1.2 to 19.7 in). They include joints for small movement (EMSEAL BEJS, XJS, JEP, WR, WOSd, and AC-AR), medium movement (Etic EJ, Wd), and large movement (WP, Etic EJF/SFEJ).

Modular expansion joints are used when the movements of a bridge exceed the capacity of a single gap joint or a finger type joint. A watertight system, invented by the Swiss company Mageba, is designed on a modular basis and can be tailored to satisfy the specific requirements of almost any structure. Modular multiple-gap expansion joints can accommodate movements in every direction and rotations about every axis. They can be used for longitudinal movements of as little as 160 mm, or for very large movements of well over 3000 mm. The total movement of the bridge deck is divided among a number of individual gaps which are created by horizontal surface beams. The individual gaps are sealed by watertight elastomeric profiles, and surface beam movements are regulated by an elastic control system. The drainage of the joint is via the drainage system of the bridge deck. Certain joints feature so-called “sinus plates” on their surface, which reduce noise from over-passing traffic by up to 80%.

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Wikipedia