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Spiral Duct

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Void Slab Spiral Tube

For the void slab construction, which is one of the general construction methods of R.C. structure, a spiral duct is placed to reduce weight and create a strong I-shaped cross section.

Product Type Product Code
Spiral Duct SP ød

Product Features

  • For the void slab construction, use a spiral duct to reduce the weight.
  • By making a strong I-shaped cross section, the secondary moment is large and it is highly resistant to bending, so that the cantilever structure and span of 4 meters or more without beams are possible.
  • It shortens construction time and reduces construction cost.

Product Uses

  • For slab construction of general buildings, apartments, government offices, public buildings, bridges, overpasses, etc.

Product Specification

Material
Hot-dip galvanized steel sheet (GI/CGI)




Dimension
Diameter(øD) (mm) : 250 ~ 1,000
Thickness(T) (mm) : 0.5 ~ 2.3
Seam Pitch(P) (mm) : 6 ~ 10
Pitch(P)(mm) : 120

* Product with special specifications can be made by order.

Void Slab Overview

Void slab Features

1) It is advantageous for a long span structure.

2) It is possible to create a large space without small beams.

3) Cantilever structure of more than 4m is possible.

4) It is advantageous for a directional building structure because the floor load is transmitted in one direction.

5) It is advantageous for the floor structure of a staircase-type auditorium.

6) The void part of the slab can be used as an air conditioning duct.

7) The overall height of the building can be reduced by reducing the floor height.

8) It has an excellent sound insulation and heat insulation effect.

9) Since a separate insulation ceiling is not required due to its excellent insulation effect, it is advantageous for the slab construction of freezer warehouse.

Void slab thickness

In the case of slab, void slab of about ℓ/32 is appropriate considering the standard that the thickness should be ℓ/32 or more. Moreover, since the void slab is a special slab of the same shape as the ribbed slab, it can be thinned to less than ℓ/32 as long as safety can be ensured.

Economic efficiency of void slab

The structural cost of construction varies depending on the size and design, etc., but in general, in the R.C. structure, it is common to erect pillars with a pitch of about 6m considering economic aspects. However, if a larger span is required due to the purpose of construction and the use value of space, it increases the structural cost.

In the case of using void slab, the structural ratio of a short span is high, but as the size of span increases, the rate of increase in the structural ratio decreases. Therefore, the economic efficiency of a large span of about 10m or more increases.

Function table for calculating the estimated quantity of void slab

Estimated void slab calculation formula (quantity per unit area)

Amount of concrete(ｍ3/ｍ2) V-D-πØ2/4D
Spiral Tube(ｍ/ｍ2) W-1/D
Rebar(KS/ｍ2)

 

Main reinforcement T1=nW1/D
Stirrup T2=W2/P2
Distributing bar T3=2W3/P3

Slab thicknessD(mm) Concrete(㎥) Spiral tube(mm) Types Upper/lower main reinforcement weight(kg) Types Upper/lower main reinforcement weight(kg)
4 5 6 7 8 9 10 4 5 6 7 8 9 10
250 0.198 4.00 D16 25.0 31.2 37.4 43.7 49.9 56.2 62.4 D19 36.0 45.0 54.0 63.0 72.0 81.0 90.0
275 0.209 3.64 D16 22.7 28.4 34.0 39.7 45.4 51.1 56.7 D19 32.7 40.9 49.1 57.3 65.5 73.6 81.8
300 0.217 3.33 D16 20.8 26.0 31.2 36.4 41.6 46.8 52.0 D19 30.0 37.5 45.0 52.5 60.0 67.5 75.0
325 0.226 3.08 D16 19.2 24.0 28.8 33.6 38.4 43.2 48.0 D19 27.7 34.6 41.5 48.5 55.4 62.3 69.2
350 0.234 2.86 D16 17.8 22.3 26.7 31.2 35.7 40.1 44.6 D19 25.7 32.1 38.6 45.0 51.4 57.9 64.3
375 0.242 2.67 D16 16.6 20.8 25.0 29.1 33.3 37.4 41.6 D19 24.0 30.0 36.0 42.0 48.0 54.0 60.0
400 0.250 2.50 D19 22.5 28.1 33.8 39.4 45.0 50.6 56.3 D22 30.4 38.0 45.6 53.2 60.8 68.4 76.0
425 0.257 2.35 D19 21.2 26.5 31.8 37.1 42.4 47.6 52.9 D22 28.6 35.8 42.9 50.1 57.2 64.4 71.5
450 0.264 2.22 D19 20.0 25.0 30.0 35.0 40.0 45.0 50.0 D22 27.0 33.8 40.5 47.3 54.0 60.8 67.6
475 0.271 2.11 D22 25.6 32.0 38.4 44.8 51.2 57.6 64.0 D25 33.5 41.9 50.3 58.7 67.0 75.4 83.8
500 0.278 2.00 D22 24.3 30.4 36.5 42.6 48.6 54.7 60.8 D25 31.8 39.8 47.8 55.7 63.7 71.6 79.6
525 0.284 1.90 D22 23.2 29.0 34.7 40.5 46.3 52.1 57.9 D25 30.3 37.9 45.5 53.1 60.6 68.2 75.8
550 0.291 1.82 D22 22.1 27.6 33.2 38.7 44.2 49.7 55.3 D25 28.9 36.2 43.4 50.7 57.9 65.1 72.4
575 0.297 1.74 D22 21.2 26.4 31.7 37.0 42.3 47.6 52.9 D25 27.7 34.6 41.5 48.5 55.4 62.3 69.2
600 0.303 1.67 D25 26.5 33.2 39.8 46.4 53.1 59.7 66.3 D29 33.6 42.0 50.4 58.8 67.2 75.6 84.0
625 0.310 1.60 D25 25.5 31.8 38.2 44.6 50.9 57.3 63.7 D29 32.3 40.3 48.4 56.4 64.5 72.6 80.6
650 0.316 1.54 D25 24.5 30.6 36.7 42.9 49.0 55.1 61.2 D29 31.0 38.8 46.5 54.3 62.0 69.8 77.5
675 0.322 1.48 D25 23.6 29.5 35.4 41.3 47.2 53.1 59.0 D29 29.0 37.3 44.8 52.3 59.7 67.2 74.7
700 0.328 1.43 D25 22.7 28.4 34.1 39.8 45.5 51.2 56.9 D29 28.8 36.0 43.2 50.4 57.6 64.8 72.0


Supporting bar, Transverse reinforcement Types Supporting bar(kg) Transverse reinforcement(kg)
Pitch @150 @200 @250 @200 @250 @300
D10 3.73 2.0 2.24 5.60 4.48 3.73
D13 6.63 4.98 3.98 9.95 7.96 -