The expansion joints of the building's outer walls , that is, the expansion joints, refer to a structure that is installed at appropriate locations along the direction of construction joints of buildings or structures in order to prevent building components from cracking or destruction due to climate temperature changes (thermal expansion and shrinkage). Sew. This type of seam set due to temperature changes is called a temperature seam or expansion joint. Expansion joints are divided into two separate parts such as walls, floors, and roofs (excluding wooden roofs) above the foundation, so that buildings or structures can be horizontally stretched in the longitudinal direction.
What is expansion joint
Expansion joints are structural joints that are installed at appropriate locations in the direction of construction joints of buildings or structures to prevent building components from cracking or destruction due to climate temperature changes (thermal expansion, cold shrinkage). Expansion joints are divided into two separate parts such as walls, floors, and roofs (excluding wooden roofs) above the foundation, so that buildings or structures can be horizontally stretched in the longitudinal direction.
Bridge expansion joints GQF-C type, GQF-Z type, GQF-E type, GQF-F type, and GQF-MZL type are all bridge expansion joint products designed using special shaped steel products formed by hot rolling. The GQF-C type, GQF-Z type, GQF-L type, and GQF-F type bridge expansion devices are suitable for bridges with a telescopic amount of 80 mm or less, and the GQF-MZL type bridge expansion devices are composed of edge beams, middle beams, and cross beams. Modular bridge expansion joint device consisting of a linkage mechanism is suitable for large and medium span bridges with a telescopic amount of 80mm-1200mm.
In order to meet the deformation requirements of the bridge deck, it is usually between the two beam ends, between the beam ends and the abutment or bridges.
Expansion joints - main role
Prevents cracks in houses due to climate change. The practice is to reserve gaps at regular intervals along the length of the building to disconnect buildings from above ground, such as roofs, walls, floors, etc. Because the building foundation is buried in the ground due to temperature changes, there is no need to disconnect. The width of the expansion joint is generally 2 to 3 cm. The insulation material is filled in the joints. The spacing between the two expansion joints is clearly defined in the specifications of the building structure.
If the plane dimension of the building is too long, due to thermal expansion and contraction, it may lead to excessive temperature stress in the structure. It is necessary to set the seam at a certain length of the structure to divide the building into several parts. The seam is the temperature seam. For different structural systems, the distance between expansion joints is different, and 8.1 of GB50010-2010, the current Chinese Code for Design of Concrete Structures, specifies this.
Expansion joints - construction process
For both cement concrete and asphalt concrete roads, reverse slotting shall be adopted: reserved slots for stakeouts, cutting expansion joint slots, adjustment of expansion joints, pre-embedded reinforcing bars, removal of notch debris, installation of telescopic devices, elevation check, Lock lashing bar â†’ mold â†’ check pouring concrete.
Expansion Joints - Control Points
1. If the embedded steel bars on the slabs are not in the correct position or are embedded in the leaks, they must be reinforced with the method of rebar insertion.
2, clean after cutting, link anchor.
3, welding rebar welding should be enough, welding should be solid.
4, the surface elevation of concrete should be correct to prevent jumping.
5. The expansion joints are firmly anchored, not loosened, and the stretching performance is effective.
6, concrete curing time is enough, do not open because of lack of maintenance time and traffic.
Expansion Joints - Safe Installation
1. The construction unit is required to lift the expansion joint in place and check whether the centerline and beam seam centerline coincide. If the top surface is the same as the road surface elevation, adjust it in time. The embedded reinforcements and expansion joint anchors are welded firmly and then passed through 12 or 16 horizontal reinforcements. Be sure to remove the expansion joint positioning platen immediately, remove the set screw, and use the angular wheel to remove the welding file and make up the paint. The top seam of the expansion joint is sealed with adhesive tape or wood, and the No. 50 concrete is poured at the notch; the insert vibrator is used to fully vibrate and compact it. Smooth the surface of the excessive section of concrete. Use a ruler to inspect the top and excessive sections of the expansion joint, and try to make it smooth with the road surface. Do a good job of concrete health before opening. The expansion joint with a collision wall and sidewalk structure was used for the above-mentioned installation process.
2. Before installation, check whether the expansion joints have the factory certificate, operating instructions, etc., and invite the supervision, design, and related personnel to inspect and inspect the appearance and geometric accuracy of the expansion joints. Draw and cut on the bridge: according to the design position, release the middle line of the expansion joint, measure the boundary of the concrete protection zone of the expansion joint from the midline position according to the design dimension, and use the concrete cutting machine to cut the bridge surface asphalt concrete according to the drawn edge line. In order to ensure that the cutting edge is not damaged, it can be cut twice. The first kerf distance is set 5cm away from the edge of the protective tape. Before the concrete is poured, the second cut along the exact edge is performed. The slits are required to be straight and accurate. Care should be taken not to damage the deck waterproof layer when cutting, and to protect the waterproof layer from being rolled up.
3. Clean up and fill gaps on the bridge deck in a timely manner: Manually work with the air compressor to remove the asphalt concrete in the cutting range, remove the loose concrete, and clean up the debris in the seam. The width of the seam must meet the design width requirements. After cleaning, the expansion joint is plugged with benzene board. Restore the embedded anchorage, and reserve the number of reinforcements to be in accordance with the design drawings. If they do not match, repair welding in time. Clean again with air compressor. In order to prevent the welding flower from burning out the foam board during the installation of the expansion joint, the foam board may be covered with steel plates or metal sheets on both sides.
4. When the expansion joints to be installed are lifted in place by cranes, the hooks of the cranes should be inspected to prevent the hooks from being disengaged. When hoisting, cranes should be hoisted in strict accordance with the manufacturer's reserved lifting positions, and the steel bars should be tied and rolled according to the design drawings. In the fixing process, the midline and straightness of the telescopic device are controlled by the method of pulling wire, and the I-beam or aluminum alloy steel with sufficient rigidity greater than 3m is placed on both sides of the expansion joint to control the elevation. The I-beams are placed along the direction of the vertical expansion joint at a distance of 1m, and are pressed on both sides of the joint. The expansion joint steel is leveled with a wooden wedge, and then the self-made small gantry is accurately leveled and adjusted with a 3m ruler. Steel wedges should be used in the flat process. After the expansion joint is in place, the midline and elevation of the expansion joint should be adjusted. The elevation is determined according to the actual road surface elevation within 5m on both sides of the joint.
Expansion Joints - Precautions
1. Due to the limitation of the length of transportation, the telescopic device can be manufactured in sections and spliced â€‹â€‹on site. The retractable devices stored on the site shall be placed in parallel and shall not be piled up to prevent deformation.
2. At the time of shipment from the factory, the connecting fixture is only for convenience of transportation, and the gap is not a fixed position. When the telescopic device is installed, it should be performed under the approval of the supervising engineer. As stipulated in the design documents, it is based on the provisions of the bridge design documents.
3, before the telescopic device is lifted into place, the concrete in the reserved tank should be beaten and cleaned. When installing, the width a of the telescopic device along the bridge should be symmetrically placed on the gap of the expansion joint, and the top surface of the expansion device should be leveled with the design elevation and then flattened. After that, the balance horizontal reinforcement is put on and the expansion device is put on. The anchor steel bar and the welded steel bars on both sides of the embedded reinforcement (to increase the number of welding points and welding length to extend the service life of the telescopic device), relax the fixture, make it free to expand and contract, at this time the telescopic device has entered the working state.
4. After completing the above steps, install the necessary template to prevent the mortar from flowing into the expansion joint and then carefully clean it with water. Pour more than C50 concrete into the reserved concrete tank. Concrete measures shall be taken when pouring concrete, vibrating and compacting.
5. After the initial setting, remove the template and promptly remove the foreign materials inside the expansion joints and in the profiled steel tape dispenser.
Editor's summary: The relevant information about what the outer wall expansion joints are and the expansion joint installations and precautions are introduced here. I hope this article will be helpful to everyone. If you still have something you don't understand, you can leave a message to Xiaobian at the bottom. We will answer your questions as soon as possible.
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