# Composite Slabs

Composite slabs are a slab supported on steel decking. These can be modelled as a solid slab with adjustment to the in-plane () and bending () thickness. For a unit width the area of slab is concrete () and steel () are known as are the second moments of area ( and ) and the values ( and ).

Referring back to the concrete as the primary material the effective area is

And the effective thickness (in-plane) is

Give the centroid of the concrete () and steel decking () the centroid of the composite section is then

and the effective second moment of area () is

And the effective thickness in bending is