Poisson’s ratio is defined as the ratio of the change in the width per unit width of a material, to the change in its length per unit length as a result of strain. Poisson ratio measures the deformation in the material in a direction perpendicular to the direction of the applied force.
Mathematically, poissons ratio is equal to the negative of the ratio of lateral strain and longitudinal strain. Therefore, if the poisson’s ratio is greater than the strength is greater.

Here, the designers gets a natural advantage of using T or L beams in any structure with slab beam construction. It is mainly used in frame type structure. A T-beam or Tee-beam is used in a construction process which is a load bearing structure of a reinforced concrete, wood or metal having T-shaped cross-section. The vertical section (web) of the beam below the compression flange serves to resist shear stress and to provide greater separation for the coupled forces of bending.
Therefore, in any situation of beam-slab we can use T-beam.