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Expansion joints, settlement joints and anti-vibration joints are three common types of joints in construction.

1. Expansion joints

1. Terminology Explanation

Expansion joint: When the building is long, the deformation joint is set to avoid cracks in the structural components caused by thermal expansion and contraction of the building.

2. Need to set seams

①The length of the building exceeds a certain limit;

②The architectural scheme is complex and has many changes;

③ The structure types of buildings vary greatly.

3. Set principles

Expansion joints are usually set vertically for a certain distance, or the structure varies widely along the length of the building. All building elements above the foundation are disconnected and separated into independent elements that can be freely stretched horizontally. part. Since the base section is less affected by temperature changes, it is usually not necessary to disconnect it.

4. Seam spacing

The maximum spacing of expansion joints should be determined according to the structure of different materials. For more information, see Design Code for Concrete Structures (2002). Table 9.1.1 on page P112 lists the maximum spacings for expansion joints for various masonry and reinforced concrete structures.

5. Seam construction

The width of the expansion joint is usually 20-40mm, usually 30mm.

6. Other requirements

In terms of structural treatment, the brick-concrete structure can adopt a single-wall scheme or a double-wall scheme. The frame structure can adopt the double-column double-beam scheme or the cantilever scheme.

①Wall expansion joint structure:

Wall expansion joints are usually made as flat joints. When the wall thickness exceeds 240mm, staggered seams, tenon and groove seams, etc. can also be made.

The deformation joints of the outer wall are usually filled with elastic waterproof materials, such as hemp silk asphalt, foam strips, ointment, etc., and the gaps are covered with galvanized iron sheets, colored thin steel plates, etc.; The sheet metal is covered with seams.

② Floor type telescopic structure:

The joints of floor expansion joints are usually filled with hemp asphalt, foam strips, grease, etc. for sealing, and covered with movable coverings such as metal, concrete or rubber. Its structural treatment needs to meet the ground requirements of leveling, leveling, waterproofing and sanitation.

Ceiling expansion joints need to be combined with upholstery. Usually, the seams are covered with sheet metal, wood or rubber plastic, etc. The cover seam plate can only be fixed on one side to ensure that both sides of the seam can be freely expanded and deformed in the horizontal direction.

③Roof expansion joint structure:

There are two main positions of roof expansion joints: the roof height on both sides of the expansion joint is the same, and the roof on both sides is staggered. When the height of the top plates on both sides of the expansion joint is the same and the top plate of the main board is the same, the water injection treatment is usually carried out by filling the joint with waterproof grease. When it is a non-sovereign roof, add half-brick low walls on both sides of the joint, and make the roof waterproof and moisture-proof. The requirements are the same as the roof waterproofing and water injection structure. On top of low walls, the traditional method uses galvanized iron to cover the joints. In recent years it has become more and more popular to cover seams with coloured sheet steel, aluminium sheets or even stainless steel skins.

2. Settlement joints

1. Terminology Explanation

Settlement joint: This is a deformation joint used to prevent uneven settlement of the building due to the different bearing capacity of the foundation or the large difference in the load of each part of the building.

2. Need to set seams

① Buildings are built on different foundations, and it is difficult to ensure uniform settlement;

② When the foundation shape, width and burial depth of adjacent parts of the same building are different, uneven settlement is likely to occur;

③ When the height difference between adjacent parts of the same building is large (generally greater than 10m), the load difference is large, or the structural form changes, etc., it is easy to cause uneven settlement;

④ When the plane shape is complex and the connection of each part is weak;

⑤Between the original building and the new or expanded building.

3. Set principles

When setting settlement joints, the building foundation, wall, floor, roof and other parts must be vertically disconnected, so that each part forms an independent rigid unit that can settle freely.

4. Seam structure

Settling joints can double as expansion joints. The width of the settlement joint is related to the foundation conditions and the height of the building.


Treatment of foundation settlement joints: The foundation of settlement joints should also be disconnected. Structural treatments include masonry and frame structures. The strip foundation under the brick-concrete structure wall usually has three treatment methods: double-wall eccentric foundation, cantilever foundation, and column cross arrangement.

② Wall, floor, roof settlement joint structure: Wall joints are usually used for covering joints such as galvanized iron sheets, aluminum alloy sheets, and non-ferrous thin steel sheets. The cover joint treatment of ground, floor and roof settlement joints is basically the same as the structure of expansion joints. The direction of deformation should be fully considered in the treatment of roof joints to minimize the influence of uneven settlement.

3. Shockproof seams

In an area with a fortification intensity of 7-9 degrees, if there is one of the following situations, a shock-proof joint should be installed:

1. The height difference between adjacent houses is greater than 6m;

2. The floors of the house are separated, and the floor height difference is large;

3. The stiffness and mass of the structures adjacent to the house are completely different.

The width of seismic joints is usually 50-100mm, but for multi-layer and high-rise reinforced concrete structures, the minimum joint width should meet the following requirements:

1. When the height does not exceed 15m, the width of the gap is 70mm;

2. When the height exceeds 15m, increase the joint width according to different fortification strengths:

In the 6-degree area, for every 5m increase in building height, the joint width increases by 20mm;

In the 7-degree area, for every 4m increase in building height, the joint width increases by 20mm;

In the 8-degree area, for every 3m increase in building height, the joint width increases by 20mm.

In the 9-degree area, for every 2m increase in building height, the joint width increases by 20mm.

Seismic joints should be installed over the entire height of the building. Normally there is no need to separate the foundation, but when the plane is more complex, the foundation should also be separated.

Generally, double walls or double columns should be set on both sides of the joint to enhance the overall rigidity of the house on both sides of the seismic joint.

Seismic joints in walls, floors and roofs have essentially the same structure as settlement joints. In addition, care should be taken not to make the wrong mouth, tongue and groove of the anti-vibration joint, so as not to lose the function of the anti-vibration joint.

Post time: 27-04-22