Deflections of composite beams
Modified calculation methods can be used to determine deflections of composite beams, but simpler procedures based on limiting span:depth ratios are often adequate.
Deflections of composite beams can be calculated using the principle of transformed sections. In this the concrete flange is replaced by an equivalent width of steel, in inverse proportion to the Young's moduli for the two materials. This enables the second moment of area of the transformed section to be calculated. The deflection can then be determined as if the beam were composed entirely of steel.
As an alternative, satisfactory deflection performance can be ensured by limiting the ratio of the length of span of the beam to its overall depth.