Useful tips for reinforcing slabs will be an empty sound if you do not study and understand the basic principles of reinforcement. Any reinforcement scheme for hollow or solid slabs is based on these principles. We will show you how to properly make reinforcement for different types of slabs.
Content
Purpose of floor slabs
A common reinforced concrete product intended for the arrangement of floors between floors or between the basement and the 1st floor are the slabs.
To give strength to the production of this type of products use hard and lightweight concrete reinforced with reinforcement. In the process of reinforcing a monolithic slab, the product acquires improved qualities: resistance to loads, fire resistance and durability. The lifetime of the reinforced slab plate reaches several decades.
In addition to construction, existing types of reinforced concrete floor slabs are used for the construction of heating mains and communication panels.
Reinforcement schemes, types
During installation, the floor slabs can acquire the position of the support along the contour, free support, or have a pinch on the supports. In any case of installation it is necessary to calculate the reinforcement of the slab.
The design reinforcement schemes are designed for beam and multi-span floors.
For beam plates and forces acting in one direction, the following schemes are used:
• cantilever (pinched plate in one edge)
• single-span cuts
• multi-span.
According to the normative documents, rectangular flat evenly loaded slabs are used for girder slabs. The support of the plates can be along the contour, along two opposite sides or on the jammed 3-4 sides, depending on the ratio of the span.
For multi-span continuous slabs there are their own design reinforcement schemes that meet the requirements of regulatory documents:
• SNiP 52-01-2003 "Concrete and Reinforced Concrete Structures"
• SNiP 3.03.01-87 and GOST R 52086-2003.
To calculate the definition of the type of reinforcement, payloads and length of plates use special graphs and tables.
To calculate the reinforcement schemes, there are special software calculation complexes (LIRA). It is rather difficult to calculate such a scheme without the basic knowledge of the calculator.
Plates of overlap, what kinds exist
marking
To distinguish the category of overlapping slabs allows standard marking, which is the main criterion in the choice of the product. Semantic abbreviation denotes the type of product:
• Overlapping plate (PC)
• Internal flooring (HB)
• Lightweight plank (SPO).
The figures following the letter abbreviation indicate the overall dimensions of the plate, indicated in decimeters.
kinds
There are the following types of slabs:
• solid (monolithic)
• hollow (hollow)
• Special purpose.
Solid reinforced concrete slabs (P) are used in the creation of floors in residential and general construction. For example, a plate P-48-12-22-8AT5 with a thickness of 220 mm with a weight of 2.65 tons. Due to its large mass, a monolithic slab plate provides the necessary sound insulation for installation.
Hollow (PC) slabs have voids of round or oval shape. In plates with voids round, the standard height is 220 mm. Hollow plates are produced in the following sizes: width 100, 120, 150 mm.
Here is the designation of the most commonly used slab: PK45-12-8 weighing 1.58 tons.
Basic scheme of plate reinforcement
The reinforcement scheme depends on the type of reinforced concrete product, but the general principles and the basic reinforcement scheme should be laid. This is due to the identical method of operation of all reinforced concrete structures - the load occurs from above and is distributed downwards to the entire area of the slab of the coating. The main workload of the reinforcement is the lower, and the upper part has a compressive load. The lower part of the armature experiences considerable tension.
The basic standard reinforcement of plates consists of the elements:
in the lower part
• working rods of the armature
at the top
• working rods, stands for wire rod, redistribution reinforcement.
For reference: the diameter of the working rods for both parts is the same.
mandatory reinforcement
We will show that the following are obligatory for reinforcement:
• middle of the plate
• Halos of accumulation of loads
• places of contact of the plate with supports
• places of contact with process holes.
reinforcement rules
Reinforcement of slabs is carried out according to technological requirements:
• Strong mesh plate
• spans that have a length of more than 8 m.
joints
When using hollow core slabs as the diaphragm of rigidity, special attention is paid to joints joints. Reinforcement plays an important role and does not allow plates to move horizontally. Joints along the length of the plate perceive shear forces.
Longitudinal joints exist between the edges of the hollow plates and the beams running parallel to the overlap. For longitudinal joints, shear force transfer is typical in the overlap plane. The conclusion is, how correctly to do reinforcement in sophisticated schemes?
We make the reinforcement of the plate monolithic
Reinforcement measures are carried out after the construction of the formwork. Between the reinforcing mesh (upper and lower) lay vertical dividers. To do this, hooks or loops are used, which are reinforced with G or U-shaped elements in the places where the floor is supported. Strengthening is performed throughout the entire contour of the slab, with the main load being transferred to the lower layer.
Therefore, the lower layer of the reinforcement should be more powerful. The upper belt of the reinforcement should be reinforced, and the lower one in the middle, subject to the continuity of the core carpet. Over the whole area fix forks for laying bolts. Then the rails are laid out on racks with guide rails and retainers, on which the horizontal sheathing will be located and the installation of wooden fences.
The educated system should exclude the content of gaps or gaps. The resulting gaps fill with mounting foam. Small cracks after the concrete filling will be filled with crushed stone.
Reinforcement of a hollow (multi-hollow) plate
The reinforcement of hollow-core plates begins with the creation of a visual drawing. The reinforcing frame is made of steel wire and rod reinforcement, in some cases ropes are used.
Strengthening is carried out according to a scheme similar to the reinforcement of a monolithic plate, almost like in this video.
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