A steel joist member for use in supporting floor structures giving great strength and convenience and improved acoustical performance having a web defining edges, first and second side surfaces and an axis, a edge wall on at least one edge, main openings through the web at spaced intervals therealong, with rounded ends and parallel linear sides, channel portions of the web displaced from the main openings remaining attached integrally to the web by right angle bend lines formed on the first side surface of the main opening along axes parallel to the web axis, and forming reinforcing channels alongside the opposite sides of the main opening.
Also disclosed is a composite joist member made up of two such joist members joined together back to back with their openings in registration.
Also disclosed is a rim member for supporting the composite joists to form a floor structure.
Also disclosed is a method of making such a floor joist member.
Also disclosed is a floor panel system by which floor panels can be prefabricated in a factory and transported to a construction site ready for installation in a building.