Concrete Flat Slab Calculator to AS3600

Verified by the CalcTree engineering team on August 30, 2024
This calculator performs the analysis and design of reinforced concrete two-way spanning slabs supported by columns, i.e. a flat slab. Design actions are calculated using simplified elastic analysis. Flexural capacity and deflection are then checked. 
All calculations are performed in accordance with AS3600-2018.
Calculation  Technical assumptions
Slab Properties 
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RC slab cross-section
Geometry:
﻿﻿B
:1.00 m​
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﻿﻿D
:225 mm​
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﻿﻿Ly
:5.00 m​
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﻿﻿Lx
:4.00 m​
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﻿﻿Ly / Lx
:1.25​
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﻿﻿Slab_type
:Two-way​
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One- or two-way slab
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Concrete Properties:
﻿﻿fc
:32MPa​
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﻿﻿Ec
:30,100​
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﻿﻿Density_c
:25 kN / m^3​
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Reinforcement Properties:
﻿﻿fsy
:500 MPa​
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﻿﻿Es
:200 GPa​
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Reinf in tension zone:
﻿﻿db_st
:16mm​
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﻿﻿s_st
:200 mm​
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﻿﻿c_st
:25 mm​
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﻿﻿d_st
:192 mm​
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﻿﻿Ast
:1,005 mm^2​
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Reinf in compression zone:
﻿﻿db_sc
:10mm​
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﻿﻿s_sc
:200 mm​
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﻿﻿c_sc
:25 mm​
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﻿﻿d_sc
:30 mm​
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﻿﻿Asc
:393 mm^2​
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Loads
Slab Analysis
Flexural (ULS) Design Check
﻿﻿phi
:0.85​
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Capacity reduction factor 
﻿﻿ku
:0.11​
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﻿﻿Check ku
:< 0.36 ✅​
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Ductility check
﻿﻿Ast,min
:430 mm^2​
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﻿﻿Check Ast
:> Ast,min ✅​
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Minimum reinforcement check
﻿﻿α2
:0.80​
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﻿﻿γ
:0.89​
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﻿﻿Mu
:77.8 kN m​
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﻿﻿+M*_max
:38.8 kN m​
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﻿﻿-M*_max
:-54.3 kN m​
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Moment capacity check
﻿﻿Check +M*
:= 39kNm ≤ Mu = 78kNm, OK ✅​
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﻿﻿Check -M*
:= 54kNm ≤ Mu = 78kNm, OK ✅​
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Note
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Deflection (SLS) Check
﻿﻿Slab type
:Ly/Lx = 1.25 ∴ Two-way slab supported by Columns​
 
﻿﻿Span_type
:Simply supported​
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﻿﻿Drop_panels
:Yes​
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﻿﻿k3
:1.05​
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﻿﻿k4
:1.40​
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﻿﻿Lef / d
:26​
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Simplified approach
For total deflection:
﻿﻿Deflection_limit_total
:1/250​
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﻿﻿(Lef / d)_limit
:29​
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﻿﻿Check
:Lef/d ≤ limit ✅​
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﻿﻿Min D
:205 mm​
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For incremental deflection:
﻿﻿Deflection_limit_incr
:1/500​
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﻿﻿(Lef / d)_limit (1)
:27​
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﻿﻿Check (1)
:Lef/d ≤ limit ✅​
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﻿﻿Min D (1)
:217 mm​
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❗Ensure these conditions have been met
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