A thin shell composite panel having a concrete slab, and sheet meta! reinforcing studs, partly embedded in the slab at spaced apart locations, each sheet metal reinforcing stud having a sheet metal web, a plurality of web main openings formed at spaced intervals and ribs and rib openings at the ends of each rib, rib flanges around the rib openings, web flanges formed around each main web opening, and characterised by reinforcing channels formed along opposite sides of the web main openings, side flanges formed along each side of the web, an embedment strip formed along one side flange, and concrete flow openings in the embedment strip.