Many occasions arise where a small torsional force is present in an I section or any other open section, and the beam fails due to this torsional force.

The user has to check whether that torsional force is real or not.

The torsional force would be produced by the shear transmitted by the slab (or other beam) to the edge of the flange multiplied by the distance to the web. If the steel beam lies within the slab or below it, the torsional forces do not really exist, as the slab does not really end at the edge of the flange. It would only end at the edge of the flange if the section were to be a closed section and at the same elevation of the slab or other beam.

Increasing the section of the steel beam does not solve the problem, as the distance to the web is increased. The solution consists in substituting the I section by a closed section with the equivalent inertia and check it does not fail.