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Here we will discuss what can be the types of hollow core slab.
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Types of Hollow Core Slab
It is a kind of precast slab through which cores are run. Not exclusively do these cores decay slab self-weight and increment primary proficiency yet additionally go about as administration conduits. It is appropriate for situations where quick developments are wanted.
There is no limitation on the range of the hollow core slab units, and their standard width is 120mm and profundity goes from 110mm to 400mm.
The slab units are usually introduced between radiates utilizing cranes and the holes between units are loaded up with tirades. It has been seen that a hollow core slab can uphold 2.5 kN/m over a 16m range. It is reasonable for offices, retail or vehicle leave advancements.
Introduction to Hollow Core Slab
The old-fashioned hollow-core slab has figured out how to stay perhaps the most well-known floor and roof slabs throughout the long term. We asked underlying designing professional Lasse Rajala, Business Unit Director at Sweco, to clarify the mystery behind its prosperity.
The adaptable item for some reasons
Hollow-core slabs are precast slabs of pre-focused cement ordinarily utilized in the development of floors in multi-story private, business, office, and mechanical structures. It is additionally conceivable to utilize hollow-core slabs in vertical or level establishments as dividers or clamor barriers. The slab has been particularly well known in Northern Europe, where the accentuation of home development has been on precast cement. There are various types of hollow-core slabs. Generally, the standard width is 1,200 mm.
Reserve funds in cement
The profoundly streamlined and efficient utilization of material makes hollow-core slabs quite possibly the most manageable items in development.
The precast solid slab has rounded voids running the full length of the slab, making the slab a lot lighter than a monstrous strong solid floor slab of equivalent thickness or strength.
In the cross part of hollow-core slabs, concrete is utilized just where it is really required. Zones where solid acts just as counterbalance are supplanted with hollows. For example, in 200-mm hollow-core slabs, 49.9 percent of the cross-segment comprises voids. In 400-mm hollow-core slabs, this rate might be pretty much as high as 55.6. This acquires investment funds solid material expenses, too reserve funds in vertical constructions, establishments, and support.
Pre-focused on hollow-core slabs won’t break under help loads. This diminishes avoidances contrasted with structures with fortified cement because the whole hollow-core slab segment adds to opposing heaps. When breaking is killed, fortification will be better shielded from erosion, empowering a more extended life expectancy for the design.
Opportunity for singular plan
At the point when a structure with hollow-core slabs is planned, the lightweight, long-range arrangement offers more prospects contrasted with customary enormous limited capacity to focus. At the point when hollow-core slabs are utilized in private structures, the segment dividers inside pads can generally be non-load bearing. This allows the individual plan of pads, just as for changes during the structure’s lifetime.
In business and public structures, long-length hollow-core slabs have empowered agreeable vehicle parks to be worked without columns, with fast and simple access and exit.
Sound protection for requesting necessities
There are high necessities for sound protection in current multi-story private structures in numerous nations. Hollow-core slabs meet this necessity well, particularly against airborne sound transmission. With standard hollow-core slab arrangements, the prerequisite R’w ≥ 55 dB against airborne sound transmission can be effortlessly accomplished.
WHAT IS A SLAB?
They are structural elements made of reinforced concrete or prefabricated materials, with a full rectangular cross-section, or with holes, of little thickness and covering a considerable surface area of the floor. They serve to form floors and ceilings in a building and are supported by beams or walls. They can have one or more continuous sections.
Perimeter-supported slabs are those that are supported on beams or walls on their four sides and therefore work in two directions, unlike slabs in one direction that structurally only support two ends. The flat slabs are those that rest directly on the columns, without any interlock between column and column.
TYPES OF SLABS:
- Solid slab
- Type t
- Vault joist
A solid slab is one made of reinforced concrete that covers rectangular or square boards whose edges rest on beams or walls, to which they transmit their load and these in turn to the columns and/or the walls and these to the foundation and is on the ground.
- It is the horizontal flat surface of a building, preferably a mezzanine and a roof.
- Inside it is made up of concrete and a kind of “net” or mesh called a grill, made up of rods tied together by annealed wire.
- The rods that are placed in both directions go from No. 3 to higher denominations, according to the characteristics of weight and of course that to be covered, they can also have 45º bends
The materials necessary for the construction of solid slabs are:
- reinforcing rod
Uses and clear:
The solid slab is used mainly in houses, in short spans, since in long spans it tends to hang, so it is advisable to use another type of slab, for example reticular.
Clear: the clearings are usually of different sizes, this type of slab is not recommended for large spans
It is made up of concrete and steel in its structural sections, but also of lightening agents such as baroque block, caissons, polyurethane.
It is similar to that of a ribbed slab, but in this case, the materials are drowned or embedded in the slab and are not visible due to the final finish.
Formed by concrete nerves separated from each other approx. 50 cm. They have filling elements of various materials. These slabs are built in different thicknesses such as 15, 20, 25, 30, and 35 cm, depending on the calculation span.
The concrete liner is generally 5 cm. They are used with small and medium lights, with low to moderate overloads.
ELEMENTS THAT MAKE UP THE SLAB
- Blocks can be made of various materials such as clay, polyethylene, and concrete, and their functions are: Lighten the weight of the slab, Serve as lost formwork to the upper concrete slab, Promote the thermal insulation of the slab acting as air chambers, Serve as a support element for the lower linings.
- Reinforcing steel placed on site
- It is a system known to the staff and easy to install
- Good performance for the placement of
- Moderate construction costs
- Good bonding finishes between the structure and the masonry
- Good anti-seismic behavior.
- Low vibration levels
- Low levels of thermal and acoustic transfer
Double T slabs are a structural element consisting of a 0.05-meter thick concrete plate with two beams with heights from 30 cm to 85 although orders can be made to certain measures and a width of up to 1.22 meters from edge to edge of its wings; It can be produced in lengths ranging from 4.00 meters to 12.50 meters.
- Raised floors and ceilings of buildings
- Gym or stadium bleachers
- Exterior walls
- Galley decks
- Mezzanines for parking
- Retaining walls
- Manufactured in a controlled environment provides better slab quality
- Require minimal use of formwork and scaffolding on site
- They do not require block fillers
- Quick installation; time-saving construction work
- Competitive cost per square meter
- By design they allow ventilation or air conditioning ducts to be installed
- Easy ceiling installation
JOIST AND BOVEDILLA
The beam and vault system is made up of the supporting elements, the reinforced concrete beams, and the vaults as lightning elements.
The joists are produced in different sizes (geometric section) and different reinforcements, likewise the vaults have different sections in length, width, and depth, in such a way that there is a great variety of combinations that can satisfy any need.
- Advantage of building slabs without formwork, because the vaults are supported by the joists.
- The joists rest on the walls or beams, temporarily propping them up. • The vaults lighten the slab and serve as a formwork for the cast-in-place concrete.
- A layer of electro-welded mesh is spread over the entire slab, to serve as a temperature reinforcement and as a compression layer.
- The slab is integrated into the walls and castles with enclosure chains that are cast over the perimeter walls.
- Concrete is poured to fill the ribs and form a compression layer over the lightweight elements (with a minimum thickness of three centimeters).
- The structural efficiency is because structural beams are formed with the joists placed every 75 cm, which together form “T” beams.
- We can assure that up to 6.00 mts. of course. It is the most economical slab system. The joists are manufactured by different methods that can be: casting in multiple metal molds and with extrusion machines.
- The vaults are produced using Vibro-compression machines where the molds for the different types of sections are exchanged, generally using light materials.
Supporting and leveling struts and beams are placed and removed 7 days after casting the compression layer. 4 “x 4” posts are placed at every 1.50m and stringers of the same section at every 1.60m to serve as provisional support for the joists.
Step 2: Joist Placement
Place the joists supported on the load-bearing walls of our slab. The joists are placed manually on the load-bearing walls. Starting from the starting wall, the first joist is placed.
NOTE: It is recommended that the compression layer be cast in conjunction with the fence beams or chains. The joists must rest on the walls or load-bearing elements for at least five centimeters.
Step 3: align joists
Vaults are placed at the ends of the joists to obtain the correct spacing of these, in addition to facilitating the subsequent placement of the other vaults in an aligned manner.
Step 4: Place the Vaults
The vaults are placed taking care that they are well seated and as close as possible. The placement is also done manually.
Step 5: Place Electrical Installations
- The hoses for the electrical installation are placed on the walls and through the holes in the vaults.
- Where an outlet is required for a focus, that vault is removed, the installation is placed, a falsework is placed underneath and then the hole is reinforced with small rods or mesh, then concrete is cast.
- In this way, the hydraulic and sanitary installations that are necessary are also carried out.
Step 6: Place Electro-welded Mesh
- It is presented and cut to the required size and tied with annealed wire to the top rod of the joists and the fence chains.
- The electro-welded mesh is cut into the floor to the desired size, then it is raised to the slab under construction and tied with annealed wire to the upper rod of the joists and the enclosure chains.
Step 7: Casting the compression layer
The holes in the end vaults and/or those that have been cut to adjust the gap are covered.
Joists and vaults are perfectly wetted and 3 to 5 cm of concrete is poured according to the mesh used.
It is recommended to wet the vaults to obtain a better adherence with the compression layer.
The concrete must have a minimum resistance of f ̈c = 200 kg / cm2. This step of pouring the compression layer (concrete layer) must be carried out in a single operation.
In a system based on a structural sheet that is fixed to the primary structure, with a mesh reinforcement that allows anchoring with the concrete and at the same time serves as a formwork. It serves as self-formwork, and the ribbing of the sheets works as a kind of rib.
It is a metal mezzanine system that uses a laminated profile designed to perfectly anchor with the concrete and form the roof slab or mezzanine.
High structural resistance: To resist loads: adequate distribution of reinforcements to cover loads.
It serves as the main steel stress during the life of the slab.
With this sheet, it is possible to place supports with a greater separation than traditional slabs while maintaining high design loads.
- Profiled sheet or sheet
- Steel beam
- Concrete slab
- Reinforcement by temperature based on an electro-welded mesh.
- Shear connectors
The temperature reinforcement is based on an electro-welded mesh, so the SDI recommendation is that the minimum steel area should be equal to 0.00075 times the area of the concrete on the deck.