Concrete Two-way 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 on four sides by beams or walls. 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 
﻿
RC slab cross-section
Geometry:
﻿﻿B
:1.00 m​
﻿
﻿﻿D
:150 mm​
﻿
﻿﻿Ly
:7.00 m​
﻿
﻿﻿Lx
:6.00 m​
﻿
﻿﻿Ly / Lx
:1.17​
﻿
﻿﻿Slab_type
:Two-way​
﻿
One- or two-way slab
﻿
Concrete Properties:
﻿﻿fc
:32MPa​
﻿
﻿﻿Ec
:30,100​
﻿
﻿﻿Density_c
:25 kN / m^3​
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Reinforcement Properties:
﻿﻿fsy
:500 MPa​
﻿
﻿﻿Es
:200 GPa​
﻿
﻿
Reinf in tension zone:
﻿﻿db_st
:16mm​
﻿
﻿﻿s_st
:250 mm​
﻿
﻿﻿c_st
:25 mm​
﻿
﻿﻿d_st
:117 mm​
﻿
﻿﻿Ast
:804 mm^2​
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Reinf in compression zone:
﻿﻿db_sc
:10mm​
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﻿﻿s_sc
:200 mm​
﻿
﻿﻿c_sc
:25 mm​
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﻿﻿d_sc
:30 mm​
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﻿﻿Asc
:393 mm^2​
﻿
﻿
Loads
Slab Analysis
Flexural (ULS) Design Check
﻿﻿phi
:0.85​
﻿
Capacity reduction factor 
﻿﻿ku
:0.15​
﻿
﻿﻿Check ku
:< 0.36 ✅​
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Ductility check
﻿﻿Ast,min
:248 mm^2​
﻿
﻿﻿Check Ast
:> Ast,min ✅​
﻿
Minimum reinforcement check
﻿﻿α2
:0.80​
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﻿﻿γ
:0.89​
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﻿﻿Mu
:37.3 kN m​
﻿
﻿﻿+M*_max
:15.8 kN m​
﻿
﻿﻿-M*_max
:-21.0 kN m​
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Moment capacity check
﻿﻿Check +M*
:= 16kNm ≤ Mu = 37kNm, OK ✅​
﻿
﻿﻿Check -M*
:= 21kNm ≤ Mu = 37kNm, OK ✅​
﻿
Note
﻿
Deflection (SLS) Check
﻿﻿Slab type
:Ly/Lx = 1.17 ∴ Two-way slab supported by Beams or walls​
 
﻿﻿Edge condition
:Two adjacent edges discontinuous​
 
﻿﻿k3
:1.00​
﻿
﻿﻿k4
:2.65​
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﻿﻿Lef / d
:51​
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Simplified approach
For total deflection:
﻿﻿Deflection_limit_total
:1/250​
﻿
﻿﻿(Lef / d)_limit
:58​
﻿
﻿﻿Check
:Lef/d ≤ limit ✅​
﻿
﻿﻿Min D
:137 mm​
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For incremental deflection:
﻿﻿Deflection_limit_incr
:1/500​
﻿
﻿﻿(Lef / d)_limit (1)
:53​
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﻿﻿Check (1)
:Lef/d ≤ limit ✅​
﻿
﻿﻿Min D (1)
:146 mm​
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❗Ensure these conditions have been met