The reinforcement set out in the table will provide a safe suspended floor or

The reinforcement set out in the table will provide a

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The reinforcement set out in the table will provide a safe suspended floor or roof slab. Professional assistance should be sought on the size and placement of reinforcement for situations other than those described. 7.1.3.2 Joist and block slab 7.1.3.2.1 Types of support Two basic types of support are common: (a) concrete or clay masonry blockwall – see Figure 7-2 ; and (b) metal beam structure – see Figure 7-3 . 7.1.3.2.2 Joists Two types of joist are common: (a) a heavy pre-stressed concrete joist which can span 3.6 m without any temporary support required for completion; and (b) a light concrete bottom base joist which need to be supported every 1.2 m maximum. The length of the joist should be: span + 100 mm minim um. NOTE This type of slab, with concrete joists and different types of blocks is very popular world wide because it is easy to install with a minimum of concrete to be poured on the job site. The dead load of this type of slab depends greatly on the type of block used. 7.1.3.2.3 Block types Many types of blocks exist for the two series of joists. These range from very light Styrofoam blocks to heavy concrete blocks. Blocks can be used independently with either of the two types of joists. Figure 7-4 gives a wide ra nge of possibilities, only one of which is available locally.
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PCTTS 599: 20XX 122 Table 7-1 – Typical reinforcement for two way suspended slabs Maximum span Slab thickness Main reinforcement (2 ways) Top center steel Top edge steel Dia. Space Dia. Spacing Dia. Spacing Slab location Live Load (metres) (mm) (mm) (mm) (mm) (mm) (mm) (mm) Domestic floor 3.00 125 10 150 10 250 10 250 1.50 kN/m2 4.00 125 12 150 12 250 10 250 5.00 150 12 120 12 240 10 250 Office floor 3.00 125 10 150 10 250 10 250 2.50 kN/m2 4.00 125 12 150 12 250 10 250 5.00 150 12 120 12 240 10 250 Small industrial floor and storage 5 kN/m2 2.50 125 10 120 10 240 10 250 3.50 125 12 120 12 240 10 250 4.50 150 12 100 12 200 10 250 Horizontal span Roof 3.00 125 10 200 10 250 10 250 1kN/m2 4.00 125 10 150 10 250 10 250 5.00 150 12 150 12 250 10 250 Note: Steel rods are MS rods and Concrete is Grade "C" Ratio (Slab Leng th / Slab Width) between 0.8 and 1.25 Slab thickness min 125 mm Top center steel length = 2 m (min) 2000 mm (min) Top edge steel leng th = 1.2 m (min) 200mm 1000 mm (min)
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PCTTS 599: 20XX 123 Figure 7-2 Joist and block slab on masonry wall Figure 7-3 Joist and block slab on metal beam.
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PCTTS 599: 20XX 124 Figure 7-4 Joists and blocks products
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PCTTS 599: 20XX 125 7.1.3.2.4 Slab thickness The slab thickness is comprised of the block and the concrete topping. The concrete topping normally varies in thickness from 40 mm to 60 mm. However, to control deflection, the total thickness is limited to: span/22.5. Where services (e.g. electrical conduit) must be installed in the concrete, the topping thickness shall be increased by 25 mm min. EXAMPLE 1 (without services): span = 4.50 m; minimum thickness = 200 mm. This can be made up of 160 mm block + 40 mm topping or150 mm block and 50 mm topping. EXAMPLE 2 (with services): span = 4.50 m; minimum thickness = 225 mm. This can be made up of 160 mm block + 65 mm topping or 150 mm block + 75 mm topping.
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