Concrete · Slabs & post-tensioning

Composite slab (steel deck) calculator

Positive moment capacity of a composite slab with the profiled deck acting as reinforcement, vs factored moment.

Standard: AS 2327 / AS 3600 rectangular stress block (deck as tensile reinforcement)

Inputs in the worked example

The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.

Input	Value	Unit
Overall slab depth D	150	mm
Average depth for self-weight	130	mm
Deck centroid height above soffit	25	mm
Deck steel area	1500	mm²/m
Deck yield fyp	550	MPa
f'c	32	MPa
Superimposed dead	1	kPa
Live load	3	kPa
Span	3.2	m
Span condition	Simply supported (wL²/8)

Diagram for the worked example

T = Ap·fyp; dn = T/(α2·f'c·γ·b)
Mu = T(d − γdn/2)
Shear-bond (longitudinal shear), construction-stage deck capacity, fire and crack control are not checked: use the deck manufacturer's design data

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Two-way slab — Moments in both directions for a rectangular slab simply supported on four edges.
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Load balancing (parabolic tendon) — Equivalent upward load wp = 8Pe/L², balanced fraction of the permanent load, and average precompression.

For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.