A concrete slab is a common structural element of modern buildings. The horizontal slabs of steel reinforced concrete, usually between 4 and 20 inches (100 and 500 millimeters) thick, are most commonly used for building floors and ceilings, while thin sheets are also used for exterior paving. Sometimes these thin sheets, ranging from 2 inches (51 mm) to 6 inches (150 mm) thick, are called mud slabs , especially when used under the main floor slab or in crawl space.
In many domestic and industrial buildings, thick concrete plates, supported by foundations or directly on the soil layer, are used to build the ground floor of the building. This can be either "grounded" or "suspended". The slab is "ground-bearing" if it is located directly on the foundation, if the slab is "suspended". For multi-storey or multilevel buildings, use of several types of concrete plates commonly used (for more types see the Concrete Slab section # Design below):
- Beams and blocks are also referred to as Rib and Block, mostly used in residential and industrial applications. This type of plate consists of pre-stress beams and hollow blocks and is temporarily buffed until adjusted, usually after 21 days.
- Preprinted hollow core slot and mounted on the site with a crane.
- In tall buildings and skyscrapers, thinner, pre-cast concrete slabs are mounted between steel frames to form floors and ceilings at every level. In-situ cast sheets are used in tall buildings and large shopping complexes and houses. These in-situ sheets are thrown on the site using reinforced shutters and steel.
In technical drawings, reinforced concrete slabs are often abbreviated as "r.c.c.slab" or simply "r.c.". Technical drawings are often created by structural engineers who use software such as AutoCad or Revit structures.
Video Concrete slab
Thermal performance
There are two main thermal considerations. The first is the question of installing floor plates. In older buildings, concrete slabs thrown directly to the ground can drain heat from the room. In modern construction, concrete slabs are usually cast on insulation layers such as expanded polystyrene, and slabs may contain heating pipes under the floor. However, there is still use for unopened slabs, usually in outbuildings that are not heated or cooled to room temperature. In such cases, direct plate casting onto rocky substrates will retain plates at or near the substrate temperature throughout the year, and may prevent freezing and overheating.
The second consideration is the high thermal mass, which applies to walls and floors, or wherever concrete is used in thermal envelopes. This is a disadvantage where rooms are heated intermittently and require a quick response, because concrete takes time to warm up, causing delays in the heating of the building. But it is an advantage in the climate with large daily temperature changes, where the plate acts as a regulator, keeping the building cool during the day and warm at night.
Common types of insulated plates are block beams and block systems (referenced above) modified by replacing concrete blocks with expanded polystyrene blocks. This change not only allows better isolation but also helps with light plates that have a positive effect on the walls and foundations of load bearings.
Maps Concrete slab
Design
For suspended plates, there are a number of designs to improve the strength-to-weight ratio. In all cases the top surface remains flat, and the bottom is modulated:
- An orrugated plate is designed when the concrete is poured into a corrugated steel tray, commonly called a decking. This steel tray increases the strength of the plates, and prevents the plaque from flexing under its own weight. Wrinkles swing from side to side.
- A striped slab gives extra strength in one direction.
- The slafle slab base provides additional strength in both directions and looks hollow from the bottom.
Reinforcement design
- A one-way slab requires a moment to hold the gain only in the shortest direction because the moment along the long axis is so small that it can be ignored. When the length ratio of the long direction to the short direction of the plate is greater than 2 then it can be regarded as a one-way slab.
Long direction = ly Short direction = lx
One way slab IF ly/lx & gt; 2
- A two-way slab requires a moment to hold the gain in either direction. If the length ratio of the long and short sides is less than two then the moment in both directions should be considered in the design.
Two-way slabs IF ly/lx & lt; 2
Construction
A concrete slab can be made prefabricated or in place. Precocrete concrete sheets are built in the factory and transported to a location, ready to be lowered into place between steel or concrete beams. They may be pre-stress (at the factory), post-stress (on site), or without pressure. It is imperative that the wall support structures are built into the correct dimensions, or the slab may not be appropriate.
In-situ concrete slabs are built on the building site using formwork - the type of boxing in which wet concrete is poured. If the reinforced plate, reinforcement, or metal bars are positioned inside the formwork before the concrete is poured. Plastic-tipped metal, or plastic bar chair, is used to hold the rebar away from the bottom and the work-side, so when the concrete is completely enveloped the reinforcement. For plates , the form work may consist only of a sidewall pushed to the ground. For suspended plates , the shapes are shaped like trays, often supported by temporary scaffolding until the concrete sets.
Formwork is generally constructed of wooden boards and planks, plastics, or steel. On the site of today's commercial buildings, plastics and steel are more common because it saves manpower. In low-budget sites, for example when installing concrete gardens, wooden planks are very common. Once the concrete has been set the wood can be removed, or left there permanently.
In some cases, formwork is not necessary - for example, a plate surrounded by a brick or block foundation wall, in which the wall acts as the side of the tray and the hardcore action as a base.
See also
References
External links
- BETON BETON A Concrete Practice Guide
Source of the article : Wikipedia
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