In the construction industry, why are I beams generally used as support as opposed to solid rectangular beams? What might be an advantage of using a rectangular beam?

Answer:I beams can withstand greater Moment compared to other beams like rectangular beam when given the same stress.

Rectangular beams are better for casting concrete beams, and for making beams of high and low moment of inertia and its centriod is easy to understand.

Explanation: I beams are beams usually used in metal work and in making beams of high moments of inertia.

Rectangular beams are beams whose centroid (the geometric center of a regular rectangular beam) are easily identifiable and they can be built to give high and low moment of inertia. This is one of the advantage of using rectangular beams.