What is dilation?
Expansion profiles are a general term for profiles used in structures to create flexible areas in structural voids called expansion joints, allowing the building to function more elastically during its use. The word "dilatation," derived from French, means to dilate or expand. Expansion profiles are the entirety of profiles attached to both sides of the structure and the elastic systems between them, designed to elastically bridge these expansion gaps.
In general, while expansion joint profiles initially consisted of two steel angle profiles filled with elastic material in between, the development of production methods, advancements in earthquake regulations, and the resulting increase in expansion joints have led to a rise in the use of aluminum profiles, EPDM gaskets, soft PVC gaskets, and thermoplastic elastomer gaskets in expansion joint profiles. Similarly, in line with changes and developments in building materials, the use of stainless steel in expansion joint profiles has also increased significantly.
Especially since the last quarter of the 20th century and the beginning of the 21st century, large-scale projects have involved structures occupying very large areas. Some of these structures are high-rise buildings connected to lower-rise buildings. Although they may not attract much attention from people who are not engineers or architects, expansion joints are used in many projects we see around us today, such as shopping malls, airports, business centers, public buildings, and hospitals, to separate floor, wall, and ceiling coverings, in wet areas and terraces, and to provide comfort to the user in large-scale structures used together in parking lots. Expansion joints should not be considered as a standalone solution; they must meet the needs of the structure before and after construction to fulfill the demands of the projects.
-Passing through the expansion gap with a certain range of motion.
-Compatible with waterproofing solutions when required.
-The structure must be able to withstand dynamic loads (pedestrian traffic, vehicle traffic, forklift, etc.) appropriate to its purpose.
- Fully compatible with side panel heights.
-It can meet requirements such as fire insulation when needed.
-The structure must be compatible with and suitable for coordination with the construction method.
Generally, the gaps where expansion profiles will be applied start from a minimum of 30 mm, and a value is reached where the larger of the expansion gap calculated according to the earthquake regulations and the minimum gap ratio derived from constructive principles is used.
Depending on the rigidity of the building's load-bearing system, the choice of reinforced concrete system, the seismic zone classification of the area where the building is constructed, and the building's height, expansion joints are currently left with dimensions of 3.5, 10, 15, 20, 25, 30, and 40 cm. In newer generation buildings with seismic isolators, these gaps can sometimes reach 150 cm or even 200 cm.
Steel and rubber joint systems are used in these types of gaps. An important point here is that even if the gaps are calculated with fractional measurements, they should be rounded up to the nearest value, considering the building application and construction of the project. For example, in a structure where the largest opening calculated is 137 mm, the project engineer rounds it up to the closest value, 150 mm, and designs the project accordingly. Otherwise, significant problems will arise in terms of material supply during the construction phase, both in terms of application and in creating the expansion gap.
In multi-functional buildings, especially those consisting of many blocks, while a portion of the building is used for parking, areas on the upper floors can be used as restaurants, communal restrooms, or connecting corridors.
Since each of these types of spaces has different needs, the expansion joint solutions also differ. In areas with different expansion joint solutions, the use of different expansion joint profiles becomes inevitable.
Therefore, during the project phase, the project engineer meets with representatives of the expansion profile manufacturers to determine the project's needs. It has been proven in international fire reports that expansion gaps of 10 cm and above can create a chimney effect during a fire. Furthermore, waterproofing in these areas needs to be thoroughly examined and its continuity ensured, separate from field applications.
When selecting expansion profiles, cladding heights, cladding types, and corner details must be carefully considered, and the intended use of the structure must be taken into account. For example, in an industrial building, the primary priority might be the load-bearing capacity of the profile, while in a healthcare facility, hygiene and user comfort might be the top priorities. In parking garage applications, models made of rubber + steel or rubber + aluminum, suitable for vehicle traffic and silent operation, can be chosen.
Once all types have been selected, expansion profiles are installed as the coatings are applied, in accordance with the project's work schedule.
An important aspect here is the correct selection of bedding material used when bringing the expansion profile to the required level and the anchoring materials used to connect the expansion profile's feet to the ground. Steel and chemical anchors are mostly used in heavy-duty profiles, while epoxy mortar or grout mortar is used as bedding material.
When installing expansion profiles, care must be taken to prevent the profile from pressing into the gap, and it should not be mounted as a cantilever. If the expansion gap is larger than the clear opening of the selected profile, the profile type and opening should be changed, and an expansion profile with a larger size and opening should be used.
Expansion profiles are generally produced in lengths of 3 to 4 meters, while gaskets are produced in lengths of 15-25 meters to ensure gasket continuity.
Considering seasonal effects, a gap of at least 3 mm should be left every three meters along the expansion joint in exterior facade expansion profiles to prevent longitudinal undulation in hot weather.
PVC-based gaskets should absolutely not be used on exterior facades. PVC material expands and contracts in hot and cold temperatures, and hardens in cold temperatures. Therefore, thermoplastic-based gaskets should be used in such areas.
The thermal expansion coefficient of aluminum is C 23 x 10⁻⁶ .
The general formula for elongation in thermal changes is:
ΔL=L.(T2-T1).C
Here, L stands for profile length.
C: Coefficient of elongation of the material
T2 : The highest temperature observed.
T1 : Lowest temperature recorded.
According to this formula, if a place where the temperature can be -5 °C in winter can reach a maximum temperature of 37 °C in summer;
ΔL=3000. (37-C-5). 23x10 -6
ΔL=2.89 mm = 3.00 mm.
We hope this article provides readers with a general overview of expansion joint profiles. In our next article, we will share more information on fire protection and isolation methods for expansion joint profiles.
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