Some factors may show unwanted movements on the ground or within the building, disrupting the integrity of the building. Dilatation joints and their importance in terms of structure arise from these movements. We can list the most important of these factors as follows:
- The floor does not have a homogeneous structure.
- Irregular groundwater,
- Uneven distribution of loads on the foundation base,
- Different expansion of building elements,
- Earthquake effect.
In order to prevent these factors from damaging the building, dilatation joints that form vertical surfaces are made. These are also called separation joints.
Dilatation joints are generally made in four ways according to their purpose:
Seating and Expansion Dilatation Joints
They are the joints made against the effects of the building from both the ground and the building loads. With these joints, separate blocks are formed in places where the building is expected to have different seating and work separately.
The length of the building blocks separated from each other by dilatation joints is generally 30 m . This length can also be made as 40-50 m in some special cases . The dilatation joint is continued in the same direction from the foundation to the roof or the height of the elements that need to be separated from each other. The width of these joints is 1-3 cm depending on the lengths of the building blocks and 1 cm per 10 m length. For example, a 3 cm wide dilatation joint is left for block lengths of 30 m.
The gap between the dilatation joints cannot be filled in a way to connect the building blocks to each other and is left empty. However, against the harmful effects of water and moisture that may pass through the foundation to the building, asphalt plates, felt, etc. It can fill with insulation materials.
Separate foundation, wall, column, beam etc. for each block on the sides of the dilatation joint. it is necessary to make carrier elements. These joints can give an ugly appearance both in the external appearance of the building and in the passages such as doors and corridors inside the building. To prevent this, joints, plaster etc. should not be closed with. Because in the slightest settlement and expansion, plaster etc. the coating will crack and fall off in places.
Earthquake Dilatation Joints
Apart from effects such as different ground settlements and temperature changes, they are joints between building blocks or existing old buildings and new buildings, only for earthquake effect.
The joint space to be left for the earthquake joint: will be at least 3 cm up to 6 m height. At least 1 cm shall be added to this value for every 3 m height after 6 m. However, this joint gap should be calculated and found according to the principles specified in the Earthquake Code when necessary.
Vibration Dilatation Joints
Factory etc. Work machines that are placed on floors make vibration while working. This vibration can cause bothersome noise and damage to the building. For this reason , a reinforced concrete foundation is made under the machine, leaving a gap of 3-5 cm between the floor and the floor . This gap left in between is called vibration joint and is filled with a waterproofing material against water and moisture. In addition, by applying double foundation, the circumference of the upper foundation is made of rubber, etc. It can also be coated with an effective measure against noise and vibration.
Movement Dilatation Joints
In long bridges made of reinforced concrete or steel, movement joints are left at certain intervals. Thus, it is ensured that the movements on the bridge do not affect the entire bridge and the bridge piers are not strained too much.
In order not to break the edges of the joints, steel brackets are placed on the sides of the joints. If the visible joint is objectionable; The joint is covered with a metal plate.