An expansion joint is a form of structural gap that is constructed to ensure the accommodation of the movement of a building in a rather controlled manner. It works for the prevention of damage to both the external and internal finishes of the building. Expansion joints run across the building’s structure. As we go higher up the building, the width of the expansion joint increases. The building movement can cause serious damage to the building in the absence of expansion joint which will make it unsafe.
An expansion joint cover works to provide a covered transition through the opening of the expansion joint and doesn’t get affected by the relative movement of the two surfaces on the sides of the joint. The building enables safe and controlled movement of the building and eliminates the possibility of a tripping hazard that can be cause from the exposed expansion joint.
Types of movements to be expected within a building
The application of expansion joint cover is done over expansion gaps present within a structure at determined locations. They are specifically designed for the absorption of structural movements. These seismic movements can be thermal or seismic. Thermal movement is a result of the change in temperature within a structure. On the other hand the seismic movement in the result of the earthquake activity beneath the structure.
There are four different types of building movements that an expansion joint cover has to mainly deal with.
1. Thermal Contraction or Expansion: It is the form of movement that is caused due to the expansion and contraction of the structure with the change in temperature or shrinking due to getting dried out.
2. Building Settlement: This is the movement caused by the structure’s dead and live loads on supporting foundations.
3. Wind Swaying: This is the form of movement that is caused by the effect of strong winds on the structure of the building. This is more noticeable in buildings that are taller.
4. Seismic Activity: This is a form of movement that is multi-directional and is cause by seismic events. The movement can prove to be significant depending upon the magnitude of the seismic activity.
Usage of expansion joint covers
The expansion joint covers come into use in all large plan buildings. However, every single building has its own specific performance requirements for the expansion joint cover. An example of this would be that in a hospital flush floor finish is required in order to allow wheeled traffic like gurneys and wheelchair, along with rubber seal that would ensure the maintenance of infection control. This is in contrary to the qualities that may be required in the expansion joint covers for shopping centres or airports, where tamperproof, strong and hardwearing joint fully made of metal will be required. In addition to that, fire barriers are also available for most of the expansion joint covers with normally a 1 or 2 fire rating but there are also 3 or 4 hour barriers available.
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