Bending strength of composite beams
Calculation procedures can be used to determine the bending strength of a composite beam; simpler methods can be used to estimate beam sizes.
The bending strength of a composite beam is dependent upon the strength and dimensions of the concrete slab and the steel beam.
A good estimate of the ultimate bending strength of the composite beam, Mu, is given by:
Mu = py . As (D + hc) / 2 (1)
where py is the design strength of the steel beam,
As is the cross-sectional area of the steel beam,
D is depth of the steel beam,
hc is the thickness of the slab.
The total depth of the composite beam can be estimated by assuming a span:depth ratio of about 15. Thus
(D + hc) = L / 15 (2)
Given the thickness of the slab, it is then possible to select a Universal Beam section which satisfies both (1) and (2) providing a reasonable first estimate for the composite beam prior to a more rigorous calculation.
