- Reinforcement types
- Transverse reinforcement
- Longitudinal reinforcement
- Features of reinforcement of brick structures of a building
You can increase the strength of brickwork with reinforcement. The reinforcement, laid in the seam, allows the load to be distributed over its area. Reinforcement of pillars, partitions, pilasters and other brick structures must be carried out in compliance with regulatory rules. This will give a guarantee of the quality of construction..
The type of reinforcement in brickwork depends on the forces acting on the structure. When the load acts centrally or with a slight deviation from the center of the structure section, transverse (mesh) reinforcement is recommended.
If the load is applied with a sufficiently large offset from the center (eccentricity), then longitudinal reinforcement is required. It will provide the strength of the structure against bending and stretching..
In transverse (mesh) reinforcement, meshes of two types are used: with rectangular cells of the “zigzag” type. They are laid on a mortar bed in the masonry seam. The distance between rectangular nets is allowed no more than 0.4 m in height. This is about five rows of masonry.
a – reinforcement with rectangular meshes; b – reinforcement with zigzag meshes
Zigzag grids are installed in two adjacent horizontal rows, mutually perpendicular to each other. Transverse reinforcement is carried out with the removal of the ends of the meshes beyond the masonry surface by 5 mm in order to control the reinforcement of the structure.
The seam thickness is taken 4 mm more than the diameter of the reinforcement used. For reinforced-masonry structures, the grade of mortar is taken at least 50. The percentage of reinforcement in brickwork by volume determines the amount of reinforcement in it:
- ? = Vand / Vto x 100
For grids with rectangular cells:
- ? = 2fand / cs
- fand – section of reinforcement;
- c is the size of the cells;
- s – distance between grids in height.
For reinforced-masonry structures at high loads, a calculation is made, at low loads, the reinforcement is installed structurally (according to the recommendations). The percentage of reinforcement (?) Must be from 0.1 to 1%.
Longitudinal reinforcement takes on tensile and bending forces arising in brickwork. For their large values, a mandatory calculation is made. Structurally, such reinforcement is used for thin walls and partitions, high pillars for stability, as well as if the structure is affected by vibration.
a – external longitudinal reinforcement; b – external reinforcement in the groove; 1 – clamps; 2 – longitudinal reinforcement
With longitudinal reinforcement, the reinforcement is laid both inside the masonry and outside. For the internal arrangement of the reinforcement, grooves are made in the masonry, the external reinforcement is made in a layer of mortar, the grade of which is allowed at least 50, and the grade of brick is not lower than 75.
Longitudinally mounted fittings are connected with clamps. With external reinforcement, the clamps are placed at a distance of no more than:
- 15 bar diameters in a compressible structure (2-3 rows of masonry);
- 80 bar diameters in tensioned structure (maximum 50 cm).
With the internal arrangement of the reinforcement, the clamps are installed at least through a distance equal to 25 diameters of the longitudinal bar.
The protective layer of reinforcement for rooms with normal operation is 10–12 mm. For wet and damp rooms, it is increased to 30 mm. The protective layer for the clamps is 10 mm.
The step between the longitudinal bars in the walls and partitions should be no more than 8h, where h is the wall thickness. The percentage of longitudinal reinforcement in bars compressed under load is allowed less than 0.1%, in stretched – 0.05%.
For transverse reinforcement, metal meshes made of cold drawn wire V-1, BP-1 (B500) with a diameter of more than 3 mm are mainly used. It is used in meshes and round reinforcement made of steel grade AI (A240) with a diameter of at least 6 mm, if the rods intersect in the seams of the masonry, if not, then at least 8 mm.
Wire and rods in meshes are welded or tied with wire. For rectangular meshes, the mesh size is 3–12 cm. Zigzag meshes are made of wire with a diameter of more than 5 mm.
The diameter of the longitudinal reinforcement is:
- more than 3 mm for clamps and tension rods;
- more than 8 mm for compressed rods.
Bars of class AI (A240), AII (A3300) are used as structural longitudinal reinforcement. In most cases, the number of reinforcement is calculated.
The modern building materials industry produces polymer composite reinforcement, including composite reinforcing mesh. It is a lightweight, highly durable, corrosion resistant and cheaper material. In many respects, composite reinforcement is superior to metal.
For reinforcement, the diameter of the composite reinforcement is taken to be less than that of steel:
- O 6 mm steel – O 4 mm composite;
- O 10 mm steel – O 6 mm composite;
- O 12 mm steel – O 8 mm composite.
Features of reinforcement of brick structures of a building
Transverse reinforcement can be used when the grade of brick or mortar cannot be increased in order to ensure the required strength of the masonry.
Partitions of 1/4 brick, in order to increase stability, are reinforced with a steel strip of 1.5-2.5 mm or rod reinforcement with a diameter of less than 6 mm every 6 rows of masonry. When the thickness of the partitions is 1/2 brick and its length is more than 3 m, the reinforcement is laid in the horizontal seams every 5–6 rows. In this case, the ends of the reinforcement must be sealed into the main walls.
Sometimes partitions or internal walls are built at different times with external walls (pillars) mating with them. In this case, bar reinforcement with a minimum diameter of 6 mm is laid in the structure of the main wall or pillar..
Subsequently, it is embedded in the masonry seams of the partition. The distance between the rods is allowed no more than 2 meters. The same rods are laid at the floor level. The length of embedding of reinforcement into walls and partitions is taken as a maximum of 1 m.
The armature is also used for the arrangement of ordinary jumpers in brick walls. In this case, high-quality filling of all seams is necessary. The height of the lintel is 5-6 rows of masonry, the length is 50 cm on each side of the opening + opening width.
The construction of the lintel begins with the laying of reinforcing bars with a diameter of 5–6 mm or a steel strip. There should be one rod for every half-brick. To the side from the opening, the reinforcement is embedded in the masonry at least 25 cm.
When joining reinforcing meshes, the overlap is from 15 cm.The choice of brick affects the distance between the meshes and is:
- less than 5 rows for ordinary clay bricks;
- less than 4 rows for thick bricks;
- less than 3 rows for ceramic stone.
Constructive (without calculation) reinforcement with meshes, which are laid less often than 45 cm in height, prevents the destruction and delamination of masonry.
Reinforcement of free-standing pillars can be performed using a metal frame, reinforcing bars with their connection with clamps and a protective layer of concrete or mortar.
a – metal clip; b – reinforced concrete cage; c – reinforced plaster; 1 – metal strip 35×5-60×12; 2 – welding; 3 – bar reinforcement Ø 5–12 mm; 4 – clamps O 4–10 mm; 5 – concrete B7.5 – B15; 6 – solution grade 50-100
The reinforcement embedded in the brickwork allows the entire structure to work as a monolith. This increases the strength, stability, durability and reliability of the entire building or structure..