Abstract: An improved composite, pre-stressed structural member and method of forming such a member of the type provided by upside down forming which includes connecting the steel beams of the composite member to the upper side of a mold so that a parallel deflection of the mold and beams occurs as the mold is filled with concrete. The improvement comprises utilizing a steel beam having a flange at or near the neutral axis with respect to a vertical deflection of the support member. After the composite structure is formed, the flange is away from the neutral axis with respect to a vertical deflection of the composite structure. This flange, therefore, significantly increases the section modulus of the composite structure while not adding significantly to the resistance to bending of the beam during pre-stressing. Stacked and welded I-beams are an example of a support in accordance wth this invention.