AU2008201614A1 - Lower chord bearing cold-formed steel joists - Google Patents

Description

APR.11.2008 00:42 0397290046 CHRYSILIOU LAW #0322 P.003

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O oi 0 0 0i Australian Patents Act 1990 Regulation 3.2 Complete Specification Standard Patent Divisional Divisional of AU 2004286000 filed 28 October 2004 and claiming priority from US 101721,610 filed 25 November 2003 Invention Title: Lower chord bearing cold-formed steel joists The following statement is a full description of this invention, including the best method of performing known to me: COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2008 00:42 0397290046 CERYSILIOU LAW #0322 P.004 1 a

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00 0 O LOWER CHORD BEARING COLD FORMED STEEL JOISTS Divisional This application is a divisional of Australian standard application No.

2004286000, the entire contents of which are incorporated herein by reference.

Field of Invention This invention relates to lower chord bearing cold-formed steel joists and to assemblies of such joists to provide structural support for floors and roofs in the building construction industry, such as support including fire rated steel-concrete composite structures.

N 1o Background of Invention

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00 O The following references to and descriptions of prior proposals or products are 0 not intended to be, and are not to be construed as, statements or admissions of common general knowledge in the art. In particular, the following prior art discussion does not relate to what is commonly or well known by the person skilled in the art, but assists in the understanding of the inventive step of the present invention of which the identification of pertinent prior art proposals is but one part.

Joists are commonly used in the construction industry to span a distance between opposing walls and provide a structural support for a floor, roof or the like. Joists can be comprised of a variety of materials including softwood, wood based laminates, and metal, particularly steel.

Steel joists can be constructed in an open web configuration, which generally consists of spaced apart upper and lower chord members which extend longitudinally thereof and are fastened together by a zig-zag web. Such open web joists are typically manufactured from hot-rolled steel structural members namely the upper and lower chords and the webs. The webs typically can be comprised of hot-rolled steel rods, which are formed into a zig-zagged pattern and welded to the upper and lower chords. Integral parts of the web are the end angled supports that connect the ends of the lower chord to the upper chord to counter load stresses at the ends of the joist. Open web joists are normally top chord bearing meaning that they are supported by the underside of the top chord, so that the top chord extends longitudinally beyond the bottom chord and the end angle supports to provide bearing interface with the opposing walls.

Open web joists are by their nature highly customizable in terms of their load bearing capabilities. Both chords and the zig-zag web can be made from different thickness of steel, and the members constituting the zig-zag web can vary in thickness along the length of the joist. The webs are open in the sense that there COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.200B 00:42 0397290046 CHRYSILIOU LAW #0322 P.005 2 00 0 is a space between the rods longitudinally along the central web section that can N receive utilities such as wires, pipe work, air ducts or the like. Open web joists can be concentric, meaning that the load being supported exerts forces that substantially pass through the centres of gravity of the joists. If the joists are loaded otherwise, they are termed eccentric.

The joist industry has introduced various types of composite steel-concrete non- Icombustible floor and roof systems for the construction industry, in whch the top o chords are embedded into a concrete slab, such a slab having both load bearing 00 10 and fire resistant properties. Examples of composite joists can be found in U.S.

oPatent Nos. 5,941,035, 4,741,138, 4,454,695 and U.S. Publication No.

200210069606 Al. A composite joist design permits the top chord member of a joist to be designed with less steel in comparison with non-composite systems since the concrete slab when properly bonded to the upper steel joist provides additional load support for the floor or roof system.

Generally speaking, for a structural joist member to be composite it must have means to mechanically interlock with the concrete to provide sheer bonding. It is generally difficult and costly to design steel and concrete composite floors using steel joists. Simply affixing vertical studs to the top chord is forbidden by safety regulations in many jurisdictions which state that structural members cannot have objects extending above a structural floor member that will encumber the walking path of a worker.

The methods for providing sheer bonding between the joist and the concrete in a composite joist are generally expensive to produce in the prior art.

Furthermore, camber (defined as a slight arch added to the joist) has been introduced into the open web joist technology to offset the deflection associated with dead loads such that only the live load deflection of the joist needs to be accounted for in designs of the joist. However large machines or jigs are needed to impart the camber to the chords of the joist where typically the web resists the cambering process.

COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.200B 00:42 0397290046 CHRYSILIOU LAW #0322 P.006 3 00

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N Moreover, hot-rolled open web joists are typically coated or finished with a Ccoloured primer. Steel joists manufacturers typically use large tanks of paint into which completed welded joist assemblies are dipped to receive a coating of primer paint. However, the process has become more expensive due to environmental considerations when using dipped tanks containing volatile solvents.

O Furthermore construction with open web joists is dependent on skilled labour 00 io which in many instances sets the critical path schedule on many construction 0 oprojects during busy construction season periods when skilled labour is in highest Cdemand. Because both the manufacture and usage in construction are labour intensive, open web steel joists are costly, so that their use is viable only in larger commercial and industrial structures requiring spans near 40 feet and above.

An alternative approach to the open web steel joist is the cold-formed steel joist.

Cold-formed steel structural designs have been used in floor and roof joists in the building construction trade for some time. However prior art cold-formed steel joists have found limited application due to the high costs of construction assembly, and are not cost effective for span lengths much above 24 feet usage is restricted to single and multi-family housing, and to commercial low rise structures.

Provided that light gauge steel is used, cost effective mass manufacture of coldformed steel joists is practical because highly automated cold forming operations such as roll-forming are commercially available. Joists in the prior art are produced by cold-forming a single piece of sheet metal into a joist comprising a top chord, a web and a bottom chord forming a continuous single structure, and are predominately used in bottom chord bearing conditions. These joists are generally eccentric in that the load forces do not pass through the centre of gravity of the joist. The most common example from prior art is the C-shaped joist which has a cross sectional profile like the letter C. Other examples of cold rolled COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2006 00:42 0397290046 CHRYSILIOU LAW #0322 P.007 4 00 O constructions are shown in U.S. Patent Publication Nos. 2002/0020138 Al and (N 2003/0084637 A1.

Composite fire rated floor structures constructed using cold-formed joists are commercially available. Examples are Hambro D510 and Speed Floor both of which have end attachments that are welded, bolted or screwed onto a single strip cold-formed section to provide a top chord bearing joist. However these IsO provide only limited load capacity due to the nature of the localized connection of o the end attachments to the cold-formed joist member. Further, they are costly to 00 10 produce. Cold-formed joist manufacturers provide holes longitudinally along the Scentral web section that are sized to receive utilities for follow-up trades. Since (N cold-formed joist material can be pre-finished the coils of steel can be galvanized or painted) the manufacturing process is less harmful to the worker and environment than the open web coating process described above.

Although cold-formed joists possess superior surface finishes, and can be mass manufactured in a cost-effective manner because there is very little dependency on manpower involved relative to the open web joist technology, current state of the art cold-formed joist technology does not fully exploit the inherent strength to mass ratio of steel, nor does it optimize material usage throughout the length of the joist. The same thickness of steel is used in both of the chords and the web, this thickness being constant along the length of the joist. Eccentric designs have a tendency to be unstable under load due to a mechanical moment about the longitudinal axis. Consequently substantial bracing is required between joists to counteract this effect.

These properties compare unfavourably with the open web steel joist where the chords and the web may be of different thickness and the web member thickness may be varied over the span length in response to loading requirements.

Accordingly, a joist and method of producing said joist that can utilize the beneficial attributes while avoiding the drawbacks from each of the open web joist technology and cold-formed joist technology is desirable. Further, it is desirable COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2008 00:43 0397290046 CHRYSILIOU LAW #0322 P.008 0o to manufacture the joist using automated cold-forming methods as opposed to Othe labour intensive welding and handling methods employed in open web steel joist construction. It is also desirable to have cost effective fire rated composite floors and roofs based on cold- formed steel joists integrally attached to a concrete slab.

Also both open web and cold-formed steel joist floor and roof structures normally require bridging systems, comprising steel members spanning the gap between joists in a floor or roof assembly, to stabilize the assembly from any lateral o o movement or rotational movement about the longitudinal direction in response to 0O applied loading. It is common practice to weld bridging in place between open oweb joists, while cold-formed joist systems have bridging structures that N commonly use screws or welding for fastening. Consequently a cost effective means to provide bridging between joists is highly desirable.

Summary of the Invention it is an aspect of this invention to provide a lower chord bearing joist comprising a lower elongate chord member being cold-formed from a unitary piece of sheet steel, the lower elongate chord member having a flange portion and a web receiving portion orthogonal thereto, the web receiving portion having two web receiving tabs and a pair of inner flange portions each extending outward from one of the web receiving tabs respectively; an upper elongate chord member, wherein the upper chord member is generally the same length as the lower chord 2s member; and a generally planar steel web attached to the web receiving portion of the lower elongate chord member between the two web receiving tabs and attached to the upper elongate chord member.

It is another aspect of this invention to provide a lower chord bearing joist comprising a lower elongate chord member, each chord member being coldformed from a unitary piece of sheet steel, the lower elongate chord member having a flange portion and a web receiving portion orthogonal thereto, the web receiving portion having two web receiving tabs; an upper elongate chord COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2008 00:43 0397290046 CHRYSILIOU LAW #0322 P.009 6 00

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member, wherein the upper chord member.is generally the same length as the lower chord member; and a generally planar steel web attached to the upper chord member and the web receiving portion of the lower chord member between the two web receiving tabs and the web having a plurality of web members attached together.

It is another aspect of this invention to provide a supporting system for use ID between opposing walls that comprises a plurality of lower chord bearing joists, o each joist having lower and upper elongate chord members, each of the lower 0O i0 and upper elongate chord members being cold-formed from a unitary piece of 0 osheet steel, each chord member having a flange portion and a web receiving portion orthogonal thereto and the web receiving portion having two web receiving tabs; and a generally planar steel web attached to the web receiving portion of the lower and upper chord members between the two web receiving tabs of each chord member; and wherein the joists are supported by and spanning a separation between opposing walls. Without any limitation to this invention, such a support system may form part of a composite floor system.

It is a further aspect of this invention to provide a composite floor system comprising a plurality of metal lower chord bearing joists, each joist including a lower elongate chord member and an upper elongate chord member, each of the upper elongate chord member and the lower elongate chord member formed from a unitary piece of cold-formed steel and having an inner flange portion and the upper chord member having a concrete engaging portion extending upwardly therefrom and the concrete engaging portion having two thicknesses of steer, the upper chord member being generally the same length as the lower chord member; a generally planar steel web attached to the lower elongate chord member and the upper elongate chord member; a deck resting on the upper chord member; and a concrete slab disposed on the upper chord member of the plurality of joists and the deck with the concrete engaging portion of the upper chord member embedded in the concrete slab to define the composite floor.

COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2008 00:43 0397290046 CHRYSILIOU LAW #0322 P.010 7

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O It is a further aspect to this invention that the said web may be replaced by a c'i segmented web, comprised of segments which may be cold-formed from different thicknesses of sheet steel fastened together.

i Another aspect of this invention is to provide bridging means comprising bridging members and receiving holes in the lower chord bearing joists such that said members may be snap fastened to the said joists without the use of tools.

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OAnother aspect of this invention resides in a method of producing a lower chord 0 10 bearing joist comprising the steps of: cold-forming a lower elongate chord 0 member from sheet metal, the lower elongate chord member having a flange Nportion and a web receiving portion orthogonal thereto, the web receiving portion having two web receiving tabs and a pair of inner flange portions each extending outward from one of the web receiving tabs respectively; cold-forming an elongate upper chord member, wherein the upper chord member is generally the same length as the lower chord member; forming at least one web member from sheet metal; and fastening the web member between the two web receiving tabs of the web receiving portion of the lower chord member with mechanical fasteners.

Another aspect of this invention is to provide a method of producing a lower chord bearing joist comprising the steps of: cold-forming an elongate lower chord member from sheet metal, the lower chord member having a flange portion and a web receiving portion orthogonal thereto and the web receiving portion having two web receiving tabs; cold-forming an elongate upper chord member wherein the upper chord member is generally the same length as the lower chord member; forming a web, the web having a plurality of web members each formed from sheet material; and fastening the web members between the two web receiving tabs of the web receiving portion of the chord with mechanical fasteners.

These and other objects and features of the invention shall now be described in relation to the following drawings: COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2008 00:43 0397290046 CHRYSILIOU LAW #0322 P.011 8 00 0 Brief Description of Drawings p^ Fig. 1 illustrates a prior art open web steel joist (OWSJ); Fig. 2 illustrates a prior art cold-formed C-shaped joist; Fig. 3 illustrates one embodiment of the invention, a concentric top chord Sbearing segmented web steel joist; Fig. 4 illustrates segments of a segmented web; 00 C Fig. 5 is a perspective view of a second embodiment of the invention showing a concentric top chord bearing, cold-formed joist having three web segments; Fig. 6 is a side elevation view of Fig. Fig. 7 is a cross sectional view along the line 7-7 of Fig. Fig. 8 illustrates a side-view of a plurality of joists having bridging members; Fig. 9 is a side elevation view of a plurality of joists having both horizontal bridging and crossed bridging members; Fig. 10 is a perspective view of a concentric top chord bearing segmented web cold-formed joist to be used in a composite floor or roof structure; Fig. 11 is a side elevation view of Fig. Fig. 12 is a cross sectional view along the lines 12-12 of Fig. 10 and also showing a concrete slab attached thereto; COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2008 00:43 0397290046 CHRYSILIOU LAW #0322 P.012 9 Fig. 13 is a side elevation view of a composite floor system having a plurality of joists; Fig. 14 and enlargement 14a are perspective views showing a bottom chord bearing version of another embodiment of the invention; Fig. 15 is a perspective view showing a top chord bearing version of another embodiment of the invention; Fig. 16 is a cross sectional view of the web only through line 16-16 of Fig.

Fig. 17 is a cross sectional view of the web only along the line 17-17 of Fig. 6; Fig. 18 is a partial side elevation view of a segmented web; Fig. 19 is a top view of Fig. 18; Fig. 20 is a top expanded view of region 20-20 in Fig. 18 showing a rivet joining two segments of a web; Fig. 21 is a partial side elevation view of the reinforcing member 84 shown in Fig. Fig. 22 is a partial view of Fig 21; Fig. 23 is a partial top plan view of the reinforcing member.

Fig. 24 is a cross-sectional view of further embodiments of the joist wherein the web and the bottom chord are cold-formed from the same sheet of steel; COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.2.1.2008 00:43 0397290046 CPSLO A 02 .1 CHRYSILIOTJ TAW #0322 P.013 00 Fig. 25 is a cross-sectional view of further embodiments of the joist wherein the web and the bottom chord are cold-formed from the same sheet of steel: Fig. 26 and enlargement 26a are perspective views of a bottom chord bearing composite version of another embodiment of the invention; Fig. 27 is a perspective view of a top chord bearing composite version of o another embodiment of the invention; 0 Fig. 28 is a schematic view of an automated assembly line for the manufacture of cold-formed joists; Fig. 29 is across section view through the line 116 -116 of Fig.14;- Fig. 30 is a side elevation view of an embodiment of one end of a bottom chord bearing composite cold-formed joist bonded to a concrete slab and integrated into a side wall; Fig. 31 is a partial enlarged view of Fig Fig. 32 is a cross sectional view through line 112 -112 of Fig. 26; Fig .33 is a side elevation view of a plurality of another embodiment of the 23 invention with horizontal bridging between joists; Fig. 34. is a side elevation view of a plurality of another embodiment with diaphragm bridging; -Fig. 35 is a side elevation view of one end of a bottom chord bearing coldformed joist supported by a foundation wall and supporting a stud wall;, Fig- 36a is a top plan view of the reinforcing flap of figure COMS ID No: ARCS-i 86478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR-hl.200B 00:43 0397290046 CRSLO A 02 .1 CHRYSILIDU LAW #0322 P.014 (N Fig. 36b is a perspective view of the reinforcing flap of figure Fig. 37 shows top and plan views of a further reinforcing flap of figure Fig. 38 is a bottom chord bearing embodiment of the invention illustrating the reinforcing end flaps;

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o Fig. 39 is a side elevation view of Fig. 38; and 00 o Fig. 40 is a cross sectional view of an alternate embodiment of a cold formed joist in a composite floor or roof structure DETAILED DESCRIPTION OF THE INVENTION In the description that follows, like pants are marked throughout the specification and the drawings with the same respective reference numbers. The drawings are not necessarily to scale and in some instances proportions may have been exaggerated in order to more clearly depict certain features of the. invention.

Fig. 1 illustrates a prior art open web joist construction 2 consisting of an upper chord assembly 4 spaced from a lower chord assembly 6. The chords are joined together by a zigzag web B which I's generally connected to the upper and lower chord assemblies 4, 6 by a number of means including welding or the like.

Fig. 2 illustrates a, prior art cold formed joist construction 10 roll-formed from a single strip of light gauge steel, having a web portion 12 having a plurality of holes 14 disposed therethrough for receiving utilities such as wire or the like, and having upper and lower chords 11 and 13 respectively.

Figs. 3 and 5 illustrate two similar embodiments of the invention, namely top chord bearing concentric joists, which comprise ani assembled joist 20 having a first or upper. chord member 22 spaced from a second or lower chord member 24.

COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2008 00:43 0397290046 CRSLO A 02 .1 CHRYSILIOTJ LAW #0322 P.015 '12 00 A steel web member 26 is also disclosed- The web member 26 is fastened to the upper and lower chord members 22 and 24 by fastening means 28. The fastening means can comprise of a variety of fastening means such as bolts and nuts, screws, welding or spot clinches, (not shown) or rivets 30 as shown in Fig7 The upper and lower chord members 22 and 24 are produced from single sheets of steel. The joist can be formed in a concentric fashion as shown in Fig. 7 where IND the upper and lower chord members 22 and 24'are substantially symmetrically o disposed about web 26.

00 0 o In these embodiments the upper chord member 22 is cold-formed to present a Ci substantially flat upper load bearing surface 34 which is formed as shown in Fig.

7 to present lower load bearing wings or extensions 36 and 38. The upper load bearing surface 34 is in contact with the lower load bearing extensions 36 and 38 so as to produce a rigid and structurally solid member which may be fastened together by the spot clinch 32. The spot clinch process is conducted in the manner well known to those persons skilled in the art and generally consists of a mechanism which pushes material by a plunger (not shown) to present a mushroomed head 40 as. shown so as to secure the members together.

The upper load bearing surface 34 and lower load bearing extensions 36 and 38 are disposed in this case symmetrically about the web 26 ,the direction of which defines the axis 27 as shown in Fig. 7. Accordingly, the upper load bearing surface 34 in concert with the lower load bearing extension 36 on one side of the axis 27 defines a horizontal extension 42 while the upper load bearing s 'urface 34 to the right of the Y axis 27 in concert with the lower load bearing extension 38 defines a horizontal extension 44 disposed on the other side of the axis 27. The lower load bearing extensions 36 and 38 are cold-formed spaced apart web receiving tabs 46 and 48 as shown. The upper portion 50 of the web 26 may include a plurality of holes 52 which are adapted to receive the fastening means 28. Fig, 7 shows an example of a fastening means 28 comprising a rivet 30 that fastens the web 26 to the upper chord 22 at the tabs 46 and 48.

COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2006 00:44 0397290046CHYIOLLA#02 P01 CHRYSILIOU LAW #0322 P.016 13 00 The spot clinches 32 in combination with the cold-formed chords connect the two folded portions 34 and 36 and 34 and 38 to reduce the width to thickness ratio of the section to avoid local buckling. The spot clinch 32 in combination with the cold work forming increases the yield strength of the steel part.

As shown in Fig- 7 the lower chord 24 is similarly constructed by forming sheet metal to present a lower chord surface 54 bent so as to present lower chord V.0 extensions 56 and 58 symmetrically disposed about axis 27. The lower chord 54 O with the lower chord extensions 56 and 58 define lower chord horizontal 00 io extensions 60 and 62 in this case symmetrically disposed about the web 26. The O lower chord extensions 56 and 58 present two spaced apart web receiving tabs 64 and 66 which are adapted to receive the lower portion 68 of the web 26. The lower chord is also fastened to the lower part of the web 28 by rivets or other means The web 26 can include a plurality of utility holes 72 which provide an access for utilities such as electrical wires, air ducts or the like. The holes 72 as shown are circular although any Configuration can be produced including square holes or the like. Furtherrrore, the holes 72 can include a cold-formed lip 74 as shown in Fig.

16. The holes 72 lighten the total weight of the joist 20 while the cold-formed lip 74 adds rigidity to the web structure 26 particularly in the direction of the "Y 1 axis 27.

The web. 26 may also include a plurality of stiffening means 80 to stilfen of the web member 26.

The stiffening means 80 comprises a first stiffening means 82 and a second stiffening means 84. The first stiffening means 82 generally consists of the ends of the web segment 26 being bent to formn a stiffening tab'82 which is disposed at approximately a 90 degree angle from the web 26. The second stiffening means 84 may consist of a hollow embossed rib structure 86 as illustrated in Fig. 21.

COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2008 00:44 0397290046CHYIOT LA#02 P.7 CHRYSILIOU LAW #0322 P.017 14 00 o The hollow rib structure 86 can be produced by a variety of means and in one 0example is produced by a punch (not shown) which pushes the web material 26 to present the stiffening structure 84 .The stiffening structure has two spaced side walls 88 and 90 as well as upper and lower walls 92 and 94 and stiffening front wall 96. The stiffening front wall 96 has stiffening holes 98 which are adapted to receive bridging members 170 and 171 in a manner to be mare fully particularized herein.

Furthermore, the web 26 can comprise a plurality of web segments 104, 106 and 00 1 108, as shown in Fig. 4, in which, as an example, three segments are shown.

0 Each of the web segments 104106 and 108 are adapted to be fastened to one another. In particular, the web segments 104, 106, 108 include a first stiffening means 82 which comprise sheet metal flaps which are bent at substantially degrees from the web material 26. The first stiffening flaps 82 may include a plurality of holes 110 which are adapted to receive fasteners such as rivets, nuts and bolts, or may receive spot clinches to secure the plurality of web segments 10D4, 106, and 108 together to form a web 26. The web segments 104, 106, and 108 also include second stiffening means 84, shown in figure 3.

201 The web segments can either all have the same thickness or have different selected thickness. For example the web segments can be thicker at the ends of the joist than segments in the middle of the joist since the shear stresses Under load are greater at the ends than in the middle.

The joist shown in Figs. 3 and 5 include angled end support members 140 that secure the ends of the lower chord 24 and upper chord 22.

A structural assembly comprising a plurality of joists 20 partially shown at Figs. 8 and 9 can define a supporting surface 160 to support a platform 162 such as a roof or floor. Each of the joists 20 as shown in cross section comprises spaced apart cold-formed steel upper and lower chord members 22 and 24 and a steel web 26 intermediate between upper and lower chord members 22 and 24.

COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2008 00:44 0397290046 CHRYSILIOU LAW #0322 P.018 00 o Fasteners 28 are utilised to fasten the web to the upper and lower chords and the C( top surface of upper chords 22 define the supporting surface160.

d< A plurality of bridging members 170 and 171 may be used to connect adjacent joists 20 together as shown so as to stiffen the said joist assembly. Parallel bridges 170 may be used as shown in Fig. 8, or may be accompanied by crisscrossed bridges 171 that are appropriately fastened to the horizontal bridges 170 IND at 173 as shown in Fig. 9. The fastening of the bridges 170 to the joists o through holes in the embossed features 84 is shown in greater detail in Figs.21, 00 10 22 and 23, effectively creating a snap in place connection without the use of Stools.

The bridge members such as 170 may be formed in an L-shaped cross section from sheet steel to produce a first surface 172 and a second surface 174. The second surface 174 is slotted at 176 as shown, and the width W of surface 174 is less than the depth D of the hole 98 to permit the end 178 of the bridging member 170 to be inserted into the hole 98 and then rotated so as to lock the edges of the slot 176 against the reinforcement face 96 adjacent the hole 98. Criss-crossed bridging members 171 may then be added and fastened as shown in Fig. 9.

Figs. 12 and 13 illustrate another embodiment of the invention defining a composite floor or roof structure. In particular, the upper chord 22 can be coldformed so as to present horizontal extensions 190 symmetrically disposed about the central web 26 and presents spaced apart vertical extensions 192 and 201 adapted to receive the top portion 50 of the web 26 to define a vertical extension 194. A rivet 196 may be utilized to fasten the upper chord 22 to the web 26 as shown.

A steel deck 198 is adapted to rest on the top surface of the horizontal upper chord extensions 190 as shown in Figs. 12 and 13. A wire mesh 205 is added.

Thereafter concrete 206 can be poured onto the deck 198 so as to produce a floor or ceiling. Since the vertical extensions 194 are embedded into and bonded with the concrete 200, a very solid composite floor system is produced. The COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 SAPR.11.2006 00:44 0397290046 CHRYSILIOU LAW #0322 P.019 16

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o vertical extension 194 can also include a generally horizontal concrete engaging N extension 202 that runs along the length of the chord 22. Since the horizontal concrete engaging extension 202 runs along the length of the chord 22, the possibility of snagging a worker's foot or clothing is minimized thereby adding to the safety feature of the joist prior to pouring of the concrete 206 over the deck 198.

The shear bond between the extensions 194 and 202 and the concrete may be oincreased by using rivets spot clinches or the like to increase the surface area of 00 10 contact between the concrete and the top chord. Despite the asymmetry provided by the horizontal engaging extension 202, this embodiment of the joist is 6 substantially concentric since the extensions 194 and 202 are bonded to the concrete and the steel-concrete composite effectively distributes the applied load to each joist through its centre of gravity Fig. 24 illustrates another embodiment of the invention which includes an upper cold-formed steel chord 22 fastened to a steel web 26 by fasteners 30. In the embodiment shown, the bottom chord 24 is a cold-formed extension of the web formed so as to present a horizontal extension 250 and 252 which may be of double thickness as shown and may be hole clinched (not shown) and may be disposed symmetrically or asymmetrically about the plane of the web.

Fig. 25 illustrates another embodiment of the invention, similar that shown in fig.

24 where the upper chord 22 has a single layer of sheet metal which is bent to produce the horizontal extensions 190 spaced apart to accommodate the end of web 26 so as to define an upper vertical extension 194 having a horizontal concrete engaging extension 202. The horizontal concrete engaging extension 202 can include a plurality of hole clinches to further strengthen the bond between the concrete and the upper chord 22 and thereby increase the shear strength of the.composite. Clearly different further embodiments are possible wherein the bottom chord, being a cold-formed extension of the web, may have different forms being symmetric or asymmetric about the web axis, and in parts being of different multiples of the web thickness.

COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.J.1.200B 00:44 0397290046 CRSLO A 02 .2 CHRYSILIOTJ LAW #0322 P.020 17 00 (N In the following, methods to locate and affix the joist to the opposed supporting walls are described. The joist 20 can be supported along the bottom chord 24 as shown in Figs. 30 and 31 illustrating a bottom chord bearing composite joist -s embodiment 20 supported by the bottom chord 24.

In particular the ends 400 of the joist are disposed within the lower stud wall 402 INC and upper stud wall 404 as shown. The lower stud wall 402 includes a stud wall o track 406 which is generally a flat piece of sheet steel 408 bent at its ends so as 0010 to present a solid surface to the joist. The upper stud wall 404 includes a similar 0 stud wall track 406. The stud walls 402 and 404 also includes a floor joist track 412 adjacent the end 400 of joist The view of the joist 20 seen in Fig. 30 can have a number of configurations as described in the context of the composite joist including that shown in Figure 12.

The composite joist is constructed in the manner previously described. An erection clip 414 can be utiliz ed so as to locate the joist 20 prior to pouring the concrete to produce the composite joist. In particular the erection clip 414 comprises a general J-shaped clip in cross-section which is secured to the bottom of the stud wall track 406 and extension 202. Once the concrete 200 is poured, the composite cold formed steel joist is supported by the bottom chord 24 at the ends 400 of the joist Fig. 35, together with the enlargements depicted in Figs. 36a and 36b, illustrates another bottom chord bearing embodiment of the Invention supported by the foundation walls and suppbirting the stud walls in a residential home.

In particular the joist 20 rests on a foundation 401 having a bearing support 410.

The end 400 of the joist 20 includes a reinforcing flap 82, which provides support against the compressive forces arising from loads applied through the stud wall 404, and is further particularized in Fig. 36a and 36b. In particular the flap 82 is cut along cut lines 600, 602 and 604 so as to present portions 620 and 622. In particular portions 620 and 622 are folded along fold lines 606 and 608.

COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR,.11.2009 00:41 0397290016 NYIOUL*02 P.2 CHRYSILIOU LAW #0322 P.021 00 o Thereafter portions 520 and 622 are further folded along fold lines 621 and 623 ci so as to present wing portions 624 and 626 which are adapted to contact respectively the lower surface of upper chord member 22 and upper surface of rower chord member 24 as best shown in Fig. 35. Fastening means may be utilized to fasten the reinforcing wings 624 and 626 to upper and lower chord members 22 and 24 so as to further rig idify and strengthen the joist Wooden or metal backing plates 412 are also utilized as shown in Fig. o Wooden pieces 414 may also be disposed as shown. The upper chord 22 0010 provides a support surface for supporting plywood 416 or the like.

0 (N Further end reinforcing members 700 may be utilized which comprises an elongated section of sheet metal having web contacting portions 702 and rigidifying portions 704 extending generally perpendicular to the web contacting portions 702. The ends of the rigidifying portions 704 are bent at 706 and 708 and adapted to contact the upper chord 22 and lower chord 24 respectively.

Furthermore fastening means may be utilized to fasten the rigidifying section 700 to web 26 and upper and lower chords, 22 and 24.

Moreover Fig. 38 illustrates an embodiment of a bottom chord bearing coldformed joist utilizing the reinforcing structure 700 shown in Fig. 37.

Fig. 28 generally illustrates a method of producing the said embodiments of the cold-formed joist. The upper chord 22 can be produced by unrolling a coil of 21 sheet steel 112 along path 114 to a roll forming machine 116 such as sold by Samee machinery located in Toronto, Canada. The roil forming machine 116 can include a station to flatten and cut a selected length of the upper chord member 22. Similarly, the lower chord member 24 can be produced by unrolling a coil of sheet steel 118 and flattening same along a path 120 to a roll forming machine 116 and then cutting to the desired length. Furthermore, the web 26 can also be produced by unwinding a coil of sheet steel 122 and flattening same at flattening station 123. A shear 125 can be used to shear the web member 26 to its desired COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2008 00:45 0397290046 CHRYSILIOU LAW #0322 P.022 19 00

O

length. Thereafter, the web 26 approaches stiffening section 128 so as to Nproduce the first and second stiffening means 82 and 84 as described.

The shear 125 can be used to produce the plurality of segmented webs 104, 106 and 108. Each web segment 104, 106, 108 can have the left hand and right hand stiffening flaps 82 produced by stiffening station 130 and 132. An appropriate punch 133 is used to produce the second stiffening means 84 as described IN above in a drawing operation. As well, punch 133 is used to produce holes 72 and area embossments 184.

ci 0 0 The sheet steel at stations 112, 118 and 122 can be galvanized or painted as C desired prior to the forming process. Furthermore the roll forming machine 116 may include punches to punch the appropriate holes 52 in the upper and lower chord members 22 and 24 so as to accommodate the appropriate fastening means 28.

Alternatively the roll forming machine 116 can include apparatus to spot clinch 32 the members together.

Accordingly the joist fabricated herein can be coated with a variety of paint colours which are painted prior to fabrication so as to produce a variety of joists having different colours and avoiding the dip painting characteristic of open web joist construction. The invention as described herein presents a number of advantages over the prior art. For example, many open web steel joists in the prior art include a cambering of the upper and lower chords 4 and 6 so as to present a slight arch to increase load bearing capabilities of the joist. Such prior art cambering techniques required working against the web during the cambering process. Applicant's invention on the other hand presents an advantage since the upper and lower chord members 22 and 24 can be cambered individually and separately from the web 26. Once the upper and lower chord members 22 and 24 are cambered they can be attached to the web 26 as described since the depth of the said camber is adequately contained within the web receiving tabs 46, 48 of the upper chord and 64, 66 of the lower chord as depicted in Fig.7. Since the COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2008 00:45 0397290046 CHRYSILIOU LAW #0322 P.023 00 o web 26 is not part of the upper and lower chord members 22 and 24 during the Cl cambering process there is substantially less resistance to the cambering.

p Alternate versions of the invention are shown in Figs. 14 and 14a, Fig.15, Figs.

d< 29 representing bottom and top chord bearing versions; and Fig 26 and 26a, and Fig. 27, representing bottom and top chord bearing versions of a composite joist.

In Fig. 14 and Fig. 29 a top chord 22 and a bottom chord 24 are attached by web receiving tabs to a generally planar web 26 that defines a Y-axis 27 of the joist by IND self piercing rivets 30 or other fastening means such as screws or rivets. Said 0 web has longitudinally spaced holes 72 formed therein each with a cold-formed O 0o lip 74 for increased rigidity under load to allow the routing of pipes, wiring, ductwork and such of other trades. Further web stiffening may be provided by

C

cold-formed area embossments 184 as shown disposed along the length of the web at locations chosen to counteract applied loads or may be provided by vertical stiffening embossments such as 84 as previously described. Further stiffening at the ends of the joist are provided by embossed plates 101 attached by fasteners 130 to the end portions of the web, and are sized to counter both compressive and shear stresses near the ends of the joist. Such embossed plates may be fastened on both sides of each end of the joist, and may terminate longitudinally in cold-formed flaps 182 that provide increased stiffness and provide a means of attaching joists at their ends.

As shown in Fig.29, the construction of the top chord 22 and the bottom chord 24 of this embodiment may be simplified compared with previously described embodiments. However additional features to those shown previously in Fig.7 say are disclosed. In particular the web receiving tabs 46 and 48 of the top chord are shown extended and cold-formed to provide outward protruding inner flanges and 47 respectively disposed generally orthoganally to the web 26. Said flanges contribute to the overall strength of the joist; and said flanges are formed with holes 198 regularly spaced along the length of the chord and designed to receive snap-in bridging members as shown in Figs. 33 and 34. The bottom chord 24 also shows inner flanges 65 and 67 as cold-formed extensions to the receiving tabs 64 and 66. Without loss of generality, Fig. 29 also serves as a COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.12..200B 00:41 03972900456HY LO A 02 .2 CERYSILIOU LAW #0322 P.024 21 00 cross section view of a top chord bearing version of this embodiment shown in perspective in Perspectives of bottom and top chord bearing composite joist versions of this embodiment ame shown in Figs. 26, 26a and Fig.27, and a cross section view through line 112-112 is shown in Fig. 32. In Fig.32, top chord 22 is attached to the web 26 by fastening tabs 192 and 201 of vertical section 194 by self piercing IND rivets 196 or other means. The double thickness of steel forming horizontal o extension 202 are fastened by rivets 199 as shown or by other fastening means, 00 10 with the head of said rivet disposed above the top surface of extension 202 in o order to increase the surface area on the top surface of extension 202 and so enhance shear bonding with concrete. The bottom chord inner flanges 65 and 67 are formed with regularly spaced holes 198 to receive snap-in bridging members as shown generally in Figs. 33 and 34.

An alternate embodiment is shown in figure 40 which is similar to the embodiment shown in figure 12. In this embodiment the joist 700 only includes a top chord 22 and does not include a web or a bottom chord. It will be appreciated by those skilled in the art that this joist would only have application in relatively short spans. Joist 700 includes a concrete engaging extension 202 which includes a vertical extension 194 that extends upwardly from horizontal upper chord extensions 190. As described above steel deck 198 is adapted to rest on the top surface of the horizontal upper chord extensions 190. A wire mesh 205 is added and thereafter concrete 200 is poured onto the deck 198.

A structural assembly comprising a plurality of joists 20 partially shown at Fig. 33 can define a supporting surface 160 to support a platform 162 such as a roof or floor. Each of the joists 20 as shown in cross section comprises of spaced coldformed steel upper and lower chord members 22 and 24 and a steel web 26 fastened between upper and lower chord members 22 and 24. A plurality of bridging members 170 is used to stiffen the assembly 20, said bridging members being disposed parallel to the support surface; and said flanges may be connected to adjacent joists at the holes 198 provided by the inner flanges COMS ID No: ARCS-i 86478 Received by IP Australia: Time (Him) 11:52 Date 2008-04-11 Afl.12..2001 00:15 0397290046 ORSLO A 02 .2 CHRYSILIOTJ LAW #0322 P.025 22 00 o and 47 of the top chord 22 and by the inner flanges 65 and 67 of the bottom Cl chord 24. Bridging members may be constructed from a length of steel of angled cross section terminated at each end by a feature 270 that fits the holes 198 and allows the bridging member to be snap fastened to inner flanges of adjacent joists.

A further aspect of this invention is illustrated in Fig. 34 partially showing a INO structural assembly of joists 20 defining a support surface 160 supporting a o platform 162 such as a floor or roof when-both parallel-and criss-cross bridging is Nl io required. Such combined bridging may be provided by a diaphragm assembly 0 370 comprising a steel plate 470 affixed by fasteners 670 to upper and lower bridging members 170 each terminated by a snap-in feature 270 at either end.

Said steel plate may provide a hole 570 having a cold-formed lip to allow the passage of wiring, pipes and ducling from other trades. Diaphragm assembly 370 i providing both parallel and criss-cross bridging may be snap-fastened to adjacent joists by engaging the snap-in feature 270 with the holes 198 provided in the inner flanges of the upper and lower chords.

The snap-in bridging illustrated in Figs. 33 and 34 advances the prior art by substantially reducing the labour and cost involved in the manual assembly of bridging on the construction site. And although Figs. 33 and 34 refer to conventional floor or roof structures, the same bridging means may be used without any loss of generality to the construction of composite steel-concrete floors and roofs.

The support structures described in this invention can be utilized either as floor joists or roof joists for single family residential, multi-family residential, commercial or industrial building construction. Further it will be appreciated by those skilled in the art that the system described herein may be used as a slay in place forming system. Analysis and testing of said structures demonstrate that the prior art is advanced in several regards including: -more economical bottom chord bearing cold-formed steel joists with spans up to 40 feet COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.200B 00:45 0397290046 CHRYSILIOU LAW #0322 P.026 23 00 O more economical top chord bearing joists capable of mass manufacture C( and customization C- more effective and economical composite floor and roof structures.

Although the joist embodiments as well as the manufacturing operations and use in construction have been specifically described in relation to the drawings, it should be understood that variations in these embodiments could be achieved by IO a person skilled in the art without departing from the spirit of the invention as Sclaimed herein.

00 to 00 SAs used herein, the terms "comprises" and "comprising" are to be construed as c being inclusive and opened rather than exclusive. Specifically, when used in this specification including the claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or components are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

It will be appreciated that the above description related to the invention by way of example only. Many variations on the invention will be obvious to those skilled in the art and such obvious variations are within the scope of the invention as described herein whether or not expressly described.

COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11

Claims (44)

1. A lower chord bearing joist comprising: a lower elongate chord member being cold-formed from a unitary piece of sheet steel, the lower elongate chord member having a flange portion and a web receiving portion orthogonal thereto, the web receiving portion having two web receiving tabs and a pair of inner flange portions each extending outward from one of the web receiving tabs respectively, 4N an upper elongate chord member, wherein the upper chord member is o fo generally the same length as the lower chord member; and 00 a generally planar steel web attached to the web receiving portion of the lower elongate chord member between the two web receiving tabs and attached Cl to the upper elongate chord member.

2- A lower chord bearing joist as claimed in claim 1 wherein the flange portion of the lower chord member has two thicknesses of steel and is generally orthogonal to the web receiving portion.

3. A lower chord bearing joist as claimed in one of claim I or 2 wherein the upper chord member further has a flange portion and a web receiving portion orthogonal thereto, the web receiving portion having two web receiving tabs and a pair of inner flange portions each extending outward perpendicularly from one of the web receiving tabs respectively and wherein the generally planar steel web is attached intermediate to the web receiving tabs of the lower and upper chord 2_ members between two web receiving tabs of .the upper and lower chord members,

4. A lower chord bearing joist as claimed in one of claim 1 or 2 wherein the web and the upper elongate chord member are cold formed together, A lower chord bearing joist as claimed in any one of claims 1 to 4 wherein the lower chord member has a generally planar bottom surface. COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.200B 00:45 0397290046 CHRYSILIOU LAW #0322 P.028 00 o 6. A lower chord bearing joist as claimed in claim 5 wherein the lower flange Cr extends outwardly from one of both sides of the web and one side of the web.

7. A lower chord bearing joist as claimed in any one of claims 1 to 6 wherein S 5 the upper chord member has a generally planar top surface. 1-

8. A lower chord bearing joist as claimed in any one of claims 1 to 7 wherein \O the upper elongate chord member includes a concrete engaging portion Sextending upwardly and laterally from the flange portion, and the concrete 00 10 engaging portion is adapted to bond to concrete when the joist is used as a Scomposite joist.

9. A lower chord bearing joist as claimed in claim 8 wherein the concrete engaging portion is generally an inverted L-shape having a generally vertical Is portion and a generally horizontal portion and wherein the concrete engaging portion has two thicknesses of steel. A lower chord bearing joist as claimed in any one of claims 1 to 9 wherein each inner flange portion of the lower chord member has a plurality of spaced apart holes formed therein.

11. A lower chord bearing joist as claimed in any one of claims 1 to 10 wherein the web includes a plurality of web members attached together.

12. A lower chord bearing joist comprising: a lower elongate chord member, each chord member being cold-formed from a unitary piece of sheet steel, the lower elongate chord member having a flange portion and a web receiving portion orthogonal thereto, the web receiving portion having two web receiving tabs; an upper elongate chord member, wherein the upper chord member is generally the same length as the lower chord member; and a generally planar steel web attached to the upper chord member and the web receiving portion of the lower chord member between the two web receiving COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2008 00:46 0397290046 CHRYSILIOU LAW #0322 P.029 26 00 0 tabs and the web having a plurality of web members attached together. S13. A lower chord bearing joist as claimed in one of claims 11 and 12 wherein the web members are web segments and at least one web segment has a different thickness than the other web segments.

14. A lower chord bearing joist as claimed in any one of claims 11 to 13 IND wherein the web members at opposed ends of the joist have a greater thickness Sthan the web members therebetween. 0 I A lower chord bearing joist as claimed in any one of claims 1 to 14 wherein C the web further includes stiffeners.

16. A lower chord bearing joist as claimed in claim 15 wherein the stiffeners include a plurality of shapes embossed therein wherein the shapes are chosen from a group consisting of vertical ridges and shapes having horizontal and vertical dimension.

17. A lower chord bearing joist as claimed in claim 16 wherein the web includes a plurality of segments and wherein the stiffeners include stiffening tabs being elongate tabs at either end of each segment.

18. A lower chord bearing joist as claimed in any one of claims 1 to 17 further including a pair of generally L-shaped end plates each attached to opposed ends of the joist wherein a first leg of each L-shaped end plate is attached to the web of the joist, and a second leg of L-shaped end plate is attachable to a second joist.

19. A lower chord bearing joist as claimed in claim 18 wherein the L-shaped member is sized to withstand both compression loads and shear loads near the end of the joist. COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2008 00:46 0397290046 CRSLO A CHRYSILIOU LAW #0322 P.030 27 00 A lower chord bearing joist as claimed in any one of claims 1 to 19 wherein the joi1st is cambered.

21. A lower chord bearing joist as claimed in any one of claims 1 to 20 wherein the joist is configured to be loaded concentrically.

22. A lower chord bearing joist as claimed in any one of claims 1 to 21 wherein the web has a plurality of holes formed therein. 00in

23. A lower chord bearing joist as claimed in claim 22 wherein each hole has a 0 lip extending around the periphery thereof

24. A lower chord bearing joist as claimed in any one of claims 1 to 23 wherein each chord member and each web is coated with coating material. A rower chord bearing joist as claimed in any one of claims 1 to 24 wherein the web is attached to each chord using one of rivets, self piercing rivets, bolts and nuts, screws, welding and spot clinches.

26. A supporting system comprising a plurality of lower chord bearing joists as claimed in claims 1 to 25 supported by and spanning a separation between opposing supporting members.

27. A supporting system as claimed in claim 26 wherein the supporting members are walls.

28. A supporting system as claimed in claims 26 or 27 further including a plurality of bridging members between adjacent joists and attached thereto. 3o 29. A supporting system as claimed in'claim 28 wherein the plurality of bridging members are adapted to snap in place. COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2008 00:46 0397290046 CHRYSILIOU LAW #0322 P.031 28 00 o 30. A supporting system as claimed in claim 29 wherein the lower chord 0bearing joists include a plurality of holes formed in the inner flange portions and 4 wherein the bridging members have ends formed therein adapted to engage the Sholes in the inner webs such that the bridging members are snapped in place by s the ends engaging the holes.

31. A supporting system as claimed in any one of claim 28 to 30 wherein the Sbridging members include at least one top bridge attached to the inner flanges of the upper chord member of the joists adjacent thereto and at least one bottom 00 0 bridge attached to the inner flanges of the lower chord member of the joists 0 Sadjacent thereto.

32. A supporting system as claimed in one of claims 31 further including criss- crossed bridges attached to the top and bottom bridges.

33. A supporting system as claimed in any one of claims 28 to 32 wherein the bridging members are diaphragm assemblies.

34. A supporting system as claimed in claim 33 wherein the diaphragm assemblies have holes formed therein. A supporting system as claimed in any one of claims 26 to 35 wherein the upper chord members are adapted to support one of a platform and a deck.

36. A supporting system as claimed in claim 35 wherein the deck supports a composite concrete slab and wherein the deck, the plurality of joists and the concrete slab together act as a stay in place forming system.

37. A supporting system as claimed in claim 36 wherein the flange portion of the upper chord members are adapted to support a deck, and the deck supports a composite slab having a concrete engaging portion embedded therein and wherein the deck, the plurality of joists and the concrete slab together act as a stay in place forming system. COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.200B 00:46 0397290046 CRSLO A 02 .3 CHRYSILIO-IJ LAW #0322 P.032 29 00 o38- A supporting system as claimed in any one of claims 36 and 37 wherein (N the concrete slab has a wire mesh embedded therein.

39. A composite floor system comprising: 5 a plurality of metal lower chord bearing joists, each joist including a lower elongate chord member and an upper elongate cho,'rd member, each of the upper elongate chord member and the lower elongate chord member formed from a IND unitary piece of cold-formed steel and having an inner flange portion and the o upper chord member having a concrete engaging portion extending upwardly N0 10 therefrom and the concrete engaging portion having two thicknesses of steel, the 0 o upper chord member being generally the same length as the lower chord (N member; a generally planar steel web attached to the lower elongate chord member and the upper elongate chord member; a deck resting on the upper chord member; and a concrete slab disposed on the upper chord member of the plurality of joists and the deck with the concrete engaging portion of the upper chord member embedded in the concrete slab to define the composite floor. A composite floor system as claimed in claim 39 wherein the concrete slab 2o has a wire mesh embedded therein.

41. A composite floor. system as claimed in claim 39 or 40 wherein the deck rests on the inner flange portion of the upper chord member.

42. A method of producing a lower chord bearing joist comprising the -steps of: cold-forming a lower elongate chord member from sheet metal, the lower elongate chord member having a flange portion and a web receiving portion orthogonal thereto, the web receiving portion having two web receiving tabs and a pair of inner flange portions each extending outward from one of the web receiving tabs respectively; cold-forming an elongate upper chord member, wherein the upper chord member is generally the same length as the lower chord member COMS ID No: ARCS-i 86478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.11.2008 00:46 0397290046 CHRYSILIOU LAW #0322 P.033 00 O forming at least one web member from sheet metal; and C'N fastening the web member between the two web receiving tabs of the web Sreceiving portion of the lower chord member with mechanical fasteners.

43. A method as claimed in claim 42 further including the step of forming the upper chord member from sheet metal, the upper chord member having a flange portion and two web receiving tab orthogonal thereto and the web receiving tab having two thicknesses of steel. 00 o 10 44. A method as claimed in claim 43 wherein the upper chord member further C includes a pair of inner flange portions each extending outward perpendicularly from one of the web receiving tabs. A method as claimed in claim 44 wherein the flange portions of the lower and upper chord members each have two thicknesses of steel.

46. A method as claimed in any one of claims 42 to 45 wherein the upper chord member further includes a concrete engaging portion extending upwardly from the flange portion.

47. A method as claimed in any one of claims 42 to 46 wherein the web, the lower chord member and the upper chord members are coated prior to the fastening step.

48. A method as claimed in any one of claims 42 to 46 wherein the web, the lower chord member and the upper chord members are coated prior to the forming steps.

49. A method as claimed in any one of claims 42 to 48 further including the step of producing lipped holes in the sheet metal forming the web and for producing regularly spaced holes in the lower and upper chord members. COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11 APR.J.1.2006 00:46 0397290046CHYLO LA#022.3 CHRYSILIOU LAW #0322 P.034 31 00 A method as claimed in any one of claims 42 to 49 including a step of (N forming a plurality of web members fastened together to define a web.

51. A method as claimed in claim 50 wherein the web members are selected with different web thicknesses.

52. A method as claimed in any one of claims 42 to 51 wherein the chord IND members include reinforced sections to accommodate greater Ioads- 00 53. A method of producing a lower chord bearing joist comprising the steps of: 0 codcold-forming an elongate lower chord member from sheet metal, the lower codmember having a flange portion and a web receiving portion orthogonal thereto and the web receiving portion having two web receiving tabs; cold-forming an elongate upper chord member wherein the upper chord member is generally the same length as the lower chord member; forming a web, the web having a plurality of web members each formed from sheet material; and fastening the web members between the two web receiving tabs of the web receiving portion of the chord with mechanical fasteners.

54. A method as claimed in claim 53 further including the step of forming the upper chord member from sheet metal, the upper chord member having a flange portion and a web receiving tab orthogonal thereto and the web receiving tab having two thicknesses of steel. A method as claimed in claim 54 wherein the flange portions of the lower and upper chord members each have two thicknesses of steel.

56. A method as claimed in claim 55 wherein the upper chord member further a concrete engaging portion extending upwardly from the flange portion. COMS ID No: ARCS-i 66478 Received by IP Australia: Time 11:52 Date 2008-04-il APR.11.2008 00:46 0397290046 CHRYSILIOU LAW #0322 P.035 32 00 o 57. A method as claimed in any one of claims 53 to 56 wherein the web, the (lower chord member and the upper chord members are coated prior to the fastening step. s 58. A method as claimed in any one of claims 53 to 56 wherein the web, the lower chord member and the upper chord members are coated prior to the forming steps.

59. A method as claimed in any one of claims 53 to 58 further including the 00 1o step of producing lipped holes in the sheet metal forming the web and for 0 producing regularly spaced holes in the lower and upper chord members. A method as claimed in any one of claims 53 to 59 wherein the web members are selected with different web thicknesses.

61. A method as claimed in any one of claims 53 to 60 wherein the chord members include reinforced sections to accommodate greater loads.

62. A method as claimed in any one of claims 42 to 61 wherein the web member is attached to each chord member by one of rivets, self piercing rivets, bolts and nuts, screws, welding and spot clinches.

63. A lower chord bearing joist substantially as hereinbefore described with reference to Figures 3 to

64. A method for producing a lower chord bearing joint substantially as hereinbefore described with reference to Figures 3 to COMS ID No: ARCS-186478 Received by IP Australia: Time 11:52 Date 2008-04-11