Do you ever wonder how these tall buildings withstand powerful earthquakes or soil settling?
It’s because of expansion joints, which allow tall and heavy structures to withstand powerful earthquakes or soil settling. The expansion joints are the structures that lay between the slaps to relieve stress on the building or the structure. Let us see the key factors, applications, and uses of expansion joints in concrete buildings or structures.
What is an Expansion Joint in the Building?
Expansion joints are installed in high-rise buildings and large-area structures to withstand natural calamities. Due to the changes in climatic conditions such as overheating or high cooling, the building facades, slabs, and pipelines can expand and contract. While constructing a building, these expansion joints are placed both inside and outside of the structures to withstand changes caused by seasonal variations. The four different types of movement that affect the building or the structure are:
- Thermal
- Wind sway
- Soil settlement
- Seismic activity
The expansion joints are used to accommodate the above four movements.
Types of Expansion Joints
The major types of expansion joints used in commercial construction are as follows:
- Horizontal
Horizontal expansion joints act as a protective barrier. These precompressed foams are easy to accommodate and install and are known for their longevity.
- Vertical
Vertical expansion joints also come as precompressed foams. You can cut them open and seal them. However, it should be handled with proper care when working at high elevations. Safety measures are required for installing this type of foam.
- Seismic
These joints are particularly used for areas greatly affected by seismic activity. They come with a special plate that is anchored to the concrete. Epoxy is used while installing these foams.
- Fire-rated
Fire-rated expansion joints are specially made to withstand fire. They can be used in buildings that have more than four floors.
- Compressed seal
The precompressed seals are used in joint openings. They compresses and expand along with concrete due to their viscoelasticity. They regain their shape and size during every compression and expansion. They are extremely soft and effective expansion joints that can be used for joint widths.
- Strip seal
These seals are locked into the concrete and are known for their high water resistance and durability. These can be widely used in bridges, heavy traffic areas, parking decks, etc.
- Inflated
These rubber seals are known for their strength in accommodating the concrete for compression and expansion. Rubber seals are used for sealing industrial structures.
- Rubber gland
These rubber glands are used for high water resistance but require more maintenance and manpower to install compared to other types.
Key Considerations of Expansion Joints
If you build a structure without using expansion joints, it may lead to cracks in the building. Before the installation process, you have to verify the quality of the expansion joint you will use in your construction project. Visual inspection is crucial for checking any defective parts. The factors to be considered before choosing expansion joints are as follows:
- Vertical vs horizontal
These types of expansion joints are used in heavy foot traffic areas, water drainage, and areas that face changes in weather conditions. They also reduce sideways movements as well as high earthquake movements.
- Traffic-rated or non-traffic-rated
Special joints should be used in high-traffic areas. It may be a pedestrian crossing area, vehicle area, or locations that have more machinery/tools.
- Covered or non-covered
An expansion joint cover may help to provide a covered transition across the opening of the joint, unaffected by the movement of two slabs. It may be covered or uncovered according to the location.
- Chemical resistance
In some cases, corrosion-proof expansion joints are used for water resistance. They may be used in swimming pools or any other industrial area.
- Filler type
The most preferable joints are silicone sealants, which are flexible to both vertical and horizontal movements.
- Fire codes
You have to choose the expansion joints that are fire resistant too. In large high-rise buildings, this type of fire-rated expansion joint is used.
Filling areas and procedure of expansion joints
Filling Areas:
Expansion joints help buildings handle movement by creating gaps that allow different parts to shift without cracking. These joints separate concrete sections in areas like:
- Floor to floor
- Floor to wall
- Wall to wall
- Ceiling to ceiling
- Ceiling to wall
- Roof to roof
- Roof to wall
Generally, expansion joints may not be needed on floors unless specific conditions require them. Some expansion joint systems are designed to be waterproof, while others are not. Properly filling and sealing these joints ensures that parts of the building can expand and contract safely, protecting it from damage due to temperature changes, settling, or other movements.
The procedure for installing expansion joints is as follows:
Installing expansion joints requires teamwork and following clear steps to ensure everything works correctly. Here’s an easy-to-understand process:
General Guidelines:
- The project team works together to install the joints and fill any gaps based on the specific requirements.
- Only trained workers should do the installation, while making sure to follow all safety rules.
Checks to Do Before Installation
Initial Inspection:
- Check the expansion joint for any dents, rust, or dirt. It should be in good condition.
Preparation:
- Clean the sealing surfaces on the flanges to make them smooth.
- Confirm that the gap between the pipelines matches the size needed for the expansion joint.
- Ensure the ends of the pipeline are clean and ready for welding, if needed.
Making Sure Everything Fits
- Check that the pipeline is in the correct position according to the design.
- Make sure the expansion joint fits well with the pipeline length.
- Confirm that the pipeline is properly supported and anchored to prevent movement.
- For joints that move sideways (lateral expansion joints), ensure the tie rods are properly installed.
Installing Guides and Anchors
- Install anchors and guides according to the EJMA (Expansion Joint Manufacturers Association) standards:
- Avoid placing the pipeline’s weight directly on the expansion joint.
- Follow these spacing guidelines:
- The first guide: ≤ 14 times the pipe diameter.
- Remaining guides: ≤ 21 times the pipe diameter (or closer, if necessary).
Points to remember while installing expansion joints:
Keep the Joint Safe:
- Use a welding blanket devoid of chloride to protect it against welding sparks.
- Prevent the bellows from accidentally arcing.
- Protect against building waste, such as mortar.
Installation Specifics:
- If it has an inner sleeve, align the flow arrow with the system flow.
- Hinge pins for angular expansion joints should be positioned correctly.
- To align bolts, do not twist the joint.
- Maintain the integrity of all parts, such as hinges and tie rods.
- Use bolts cautiously and refrain from using tools that could harm the bellows.
- To avoid material interfering with bellows movement, use a lagging cover while adding insulation.
Final Verification:
- Perform a visual assessment before system testing.
- Take off all of the temporary devices that have black or yellow tape on them.
- Make sure everything is set up to avoid problems during operation and testing.
Do’s and Don’ts of Expansion Joints
The do’s and don’ts of expansion joints in concrete buildings are as follows:
| S.No | Do’s | Don’ts |
| 1. | Identify the joints early in the designing process | Don’t forget about the joints |
| 2. | Considering building shape is important | Don’t use joints in unnecessary places |
| 3. | Calculate the structural frame of the building according to the expansion joint | Make sure to find the concrete crack before the installation of the filler |
| 4. | Consider the temperature changes while constructing a building. | Don’t forget to check the changes in expansion joints |
Conclusion
On the whole, expansion joints are used to relieve the stress of the concrete buildings while movements take place. For each structure, unique expansion joints are used to fill the gap and withstand the building against seasonal variations.
FAQ’s
The major types of expansion joints in the building are as follows:
Horizontal
Vertical
Seismic
Fire-rated
Compressed seal
Strip seal
Inflated
Rubber gland
The expansion joints are used to withstand the changes caused by climatic conditions such as thermal, seismic, high wind, and soil settlement.
It prevents the building or the structure from falling or collapsing due to natural calamities.
Yes, they are necessary for tall buildings or structures, but not for small residential homes.