Also known as a movement joint, expansion joints allow an assembly to expand or contract when exposed to heat, absorb any forms of vibrations as well as allow movement which may occur in pavements due to ground settlements or earthquakes. Expansion joints are present in several applications all over the world, from pavements and railway tracks to roads, buildings and several other structures. The purpose for these joints is to allow the structure that they are being applied to, to safely expand or absorb any other movements without breaking or deforming under the pressure. The primary function of expansion joints is to allow heat-induced expansion and contraction that occurs in structure in the various states of weather. The joint can be a simple caulk filled area that would allow space it to expand when exposed to heat or some type of interlocking metal device which allows the teeth that are present in the joint to move accordingly in response to the changes in the weather. The location of these joints is placed strategically in a construction at regular intervals, allowing room for expansion without weakening the overall structure. The most common structures affected by heat expansion which are present in everyday life are sidewalks, bridges and piping systems amongst several other structures. If these structures were to crack under the stress induced due to heat expansion, it could affect daily routines for many people. Thus, it is important to have the expansion joints to allow these constructions to expand when there is a need.
In the case of railway tracks, if expansion joints are not used, railway tracks that are exposed to direct sunlight would expand in the presence of heat and without an expansion joint will crack or deform. This can be very dangerous as, if a train is operating on that track, it could derail when it passes the deformed point along the track. This implies the importance of the expansion joints in the track, as the joint would allow the track to expand without breaking or deforming. This would also save the railway’s resources. In piping systems, the role of expansion joints is also similar as the joint would allow for the proper function of the piping system. Sidewalks and pavements are also routinely fitted with expansion joints which provide the structure with room to expand when exposed to heat. Many roads in deserted unoccupied areas would have bulges popping out from them, with cracks on top. This is the result of expansion in the road in the absence of expansion joints. Control joints are different as compared to expansion joints as they allow cracking in a road or bridge to occur in a controlled fashion. These joints are cut in the concrete or asphalt on roads at regular intervals and these joints can be sealed with hot tar or cold sealant.
Expansion Joints Accessories
Liners can be used inside expansion joints to protect metallic bellows from erosion or reduce the turbulence across the bellows. Liners can only be used together with purge connectors. The joints can also have external covers that protect the internal bellows from damage. These covers can also provide insulation to the bellows, while either being a permanent or temporary accessory. Limit rods, as their name would suggest, are used in expansion joints to limit the axial compression or expansion in expansion joints. These devices allow the expansion joint to move over a range and stop according to where the nit stops are placed along the rods. The purpose of these accessories is to prevent the expansion joint from over expanding.
Expansion joints can be installed manually following the right procedures that a manufacturer would have provided in an expansion joint accessory.