COLD FORMED JOIST
The present invention provides a cold formed joist that can be used in a variety of construction applications. The present cold formed joist consists of three elements, each formed from sheet metal: an upper chord, an intermediate web, and a lower web. These three elements can be produced in different dimensions. The upper chord further consists of a downwardly facing receiving channel adapted to receive the upper edge of the intermediate web, and two upwardly facing channels. The lower chord consists of an upwardly facing receiving channel that is adapted to receive the lower edge of the intermediate web.
1 . An upper chord for a cold formed metal joist having an upper chord, a lower chord and a web portion disposed therebetween, the upper chord comprising:
a first longitudinally extending downwardly opening channel formed therein sized and shaped to receive thereinto an upper edge of said web portion;
at least one second longitudinally extending upwardly opening channel arranged parallel to said first channel;
a flange portion to provide said upper chord with a substantially horizontal load engaging surface.
2 . The upper chord of claim 1 wherein said second channel is formed to mechanically interlock with a hardenable fluid received thereinto for restraining vertical separation between said upper chord and said fluid upon the hardening thereof.
3 . The upper chord of claim 2 wherein said first longitudinal channel is formed along said chord's longitudinal centre line.
4 . The upper chord of claim 3 wherein one of said second channels is formed to either side of said first channel.
5 . The upper chord of claim 4 wherein said flange portion extends laterally outwardly from each of said second channels.
6 . The upper chord of claim 5 wherein said flange portion comprises a first horizontal portion and a second projecting portion.
7 . The upper chord of claim 6 wherein said projecting portion is bent at a predetermined angle relative to said horizontal portion.
8 . The upper chord of claim 7 wherein said projecting portion is bent upwardly relative to said horizontal portion.
9 . The upper chord of claim 7 wherein said projecting portion is bent downwardly relative to said horizontal portion.
10 . The upper chord of claim 2 wherein said second channel has side walls and an interconnecting bottom wall, wherein at least one of said side walls is formed with a bulge therein for mechanically interlocking with said fluid following the hardening thereof.
11 . The upper chord of claim 10 wherein said bottom wall has a plurality of horizontally spaced apart perforations formed therethrough.
12 . The upper chord of claim 11 wherein each of said horizontal portions of said flange portion includes horizontally spaced apart indentations formed therein.
13 . A cold formed metal joist for use in composite and non-composite construction applications, the joist comprising:
a longitudinally extending upper chord;
a longitudinally extending lower chord; and
a web portion disposed therebetween;
said upper chord comprising a first longitudinally extending downwardly opening channel formed therein sized and shaped to receive an upper edge of said web portion thereinto, a second longitudinally extending, upwardly opening channel disposed on each side of said first channel and a flange portion providing said upper chord with a horizontal load engaging surface, said lower chord comprising a first longitudinally extending upwardly opening channel formed therein sized and shaped to receive a lower edge of said web portion thereinto, said upper and lower edges of said web portion being fixedly connected into said first channels of said upper and lower chords, respectively for a strong load resistant connection thereto.
14 . The joist of claim 13 wherein the metal along said upper and lower edges of said web portion is folded over to increase their thickness.
15 . The joist of claim 14 wherein said web portion further includes a plurality of longitudinally spaced apart cold formed stiffening ribs extending vertically from adjacent said upper folded over edge to adjacent said lower folded over edge.
16 . The joist of claim 15 wherein said web portion additionally includes a plurality of longitudinally spaced apart openings formed therethrough, said openings being located between said upper and lower folded over edges of said web portion.
17 . The joist of claim 16 wherein said openings each have reinforced edges, said reinforced edges being cold formed.
18 . The joist of claim 17 wherein said reinforced edges are semi-elliptical in cross-sectional shape.
19 . The joist of claim 18 wherein each of said upper and lower chords and said web portion are each cold formed from a unitary piece of sheet metal.
20 . The joist of claim 13 wherein said second channels are formed to mechanically interlock with a hardenable fluid received thereinto for restraining vertical separation between said upper chord and said fluid following the hardening thereof.
21 . The joist of claim 20 wherein said second channels have sidewalls and an interconnecting bottom wall.
22 . The joist of claim 21 wherein said bottom wall has a plurality of longitudinally spaced apart perforations formed therethrough.
23 . The joist of claim 21 wherein at least one of said sidewalls is formed with a bulge therein for mechanically interlocking with said hardenable fluid following the hardening thereof.
24 . The joist of claim 23 wherein said lower chord is substantially identical to said upper chord.
25 . A method of interconnecting a metal joist for construction applications, the joist having longitudinally extending upper and lower chords and a web portion disposed therebetween, to a hardenable fluid, the method comprising the steps of:
forming said upper chord to have one or more upwardly opening longitudinally extending channels therein, and forming each of said channels to mechanically interlock with a hardenable fluid poured thereinto to prevent vertical separation between said upper chord and said fluid following the hardening thereof.
26 . The method of claim 25 wherein each of said one or more channels has opposed spaced apart side walls and a lower interconnecting bottom wall.
27 . The method of claim 26 including the additional step of forming at least one of said sidewalls with a longitudinally extending bulge therein for mechanically engaging said hardenable fluid.
28 . The method of claim 27 including the additional step of forming into said bottom wall a plurality of longitudinally spaced apart perforations for the escape of air during the pouring of said hardenable fluid into said channels, said hardenable fluid being concrete.
29 . The method of claim 28 wherein said upper chord is at least partially embedded in said concrete.