US20050108978A1

US20050108978A1 - Segmented cold formed joist

Info

Publication number: US20050108978A1
Application number: US10/721,610
Authority: US
Inventors: Michael Strickland; Lei Xu
Original assignee: Best Joint Inc
Current assignee: Best Joist Inc; Best Joint Inc
Priority date: 2003-11-25
Filing date: 2003-11-25
Publication date: 2005-05-26
Also published as: CA2667892A1; CA2667892C; WO2005042869A1

Abstract

A joist comprised of at least one cold-formed elongated chord member; a cold-formed web having a plurality of web members and means for securing said web to said chord member.

Description

FIELD OF INVENTION

This invention relates generally to a joist and particularly relates to floor and roof joists for building construction and more particularly to methods for producing concentric top chord bearing cold form joists for composite concrete and non-composite joist conditions for the construction industry.

BACKGROUND OF INVENTION

Joists are commonly used in the construction industry to span a distance and provide a surface for a floor, roof or the like. Joists can be comprised of a variety of materials including wood and metal.
Metal or 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 by hot-roll structural sections namely the upper and lower chord members and the webs. The webs typically can be comprised of hot-rolled steel rods, which are zig-zagged and welded to the upper and lower chords. The webs are open in the sense that there is a space between the rods longitudinally along the central web section that can receive utilities such as wires or air ducts that are installed by other trades.
Open web joists can be concentric, that is they are symmetric about the web in cross section, or eccentric.
The joist industry has introduced various types of composite concrete noncombustible floor and roof systems for the construction industry. Examples of composite joists can be found in U.S. Pat. Nos. 5,941,035, 4,741,138, 4,454,695, U.S. Publication No. 2002/0046534 A1 and 2002/0069606 A1. A composite joist design permits the top chord member of a joist to be designed ith less steel in comparison with non-composite systems since the concrete slab hen properly bonded to the upper steel joist acts as the top chord of 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 joists because legislation exists in various jurisdictions which relate to federal safety laws requiring that structural members cannot have objects extending above a structural floor member that will encumber the walking path of a worker.
Generally speaking the details for providing sheer bond capacity 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 were typically the web resists the cambering process.
Furthermore joists are erected in a “top chord bearing condition” where they hang passively vertical during and after erection from its top or upper chord at the support ends. Alternatively joists can be “bottom chord bearing” where the bottom chord supports the joist.
Moreover, hot-rolled open web joists are typically coated or finished with a primer that can be coloured grey or red. 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.
Furthermore open web joists technology is dependent on skilled labour and in many instances set the critical path schedule on many construction projects during busy construction season periods when skilled labour is in highest demand.
Joists can also be produced by cold-formed steel structural designs and have been used in floor and roof joists in the building construction trade for some time. However prior art cold form steel joists are widely used for wall and floor framing in residential homes and non-load bearing wall framing where the span of the joist is not excessive. The cold form technology presently has limitation in span lengths for floor and roof members to be widely used.
Unless cold form materials can be used in the thin applications, the use of these materials is cost prohibitive since hot-rolled pre-finished steel coil material typically used in forming comes in at much greater cost than the hot-rolled shapes used for the open web industry as described above. Furthermore, cold-formed joists presently used only provide limited span lengths and are not very cost efficient to provide for spans greater than 24 feet.
Joists produced by cold-forming from a single piece of sheet metal is predominately used for bottom chord bearing conditions and these members generally have an eccentric nature about the “Y” Axis. Other examples of cold rolled constructions are shown in U.S. Patent Publication Nos. 2002/0020138 A1 and 2003/0084637 A1.
Moreover other manufactures have introduced “top chord bearing” single stripped cold-formed floor joists such as Hambro D510 and Speed Floor which has end attachments that can be welded, bolted or screwed onto a single strip cold-formed section to provide a top chord bearing condition. However these provide only limited load capacity due to the nature of the localised connection to the cold-formed joist member. Accordingly cold-forming production has generally been applied to a single piece of sheet metal since it requires very little direct manpower to produce.
Many cold-forming manufactures provide holes longitudinally along the central web section that are sized to receive utilities for follow-up trades. Since cold-formed joists material can be pre-finished (i.e. the coils of galvanised steel can be galvanised or painted) the manufacturing process is less harmful to the worker and environment than the open web production described above.
Although cold-forming provides superior surface finishes and very little dependency on manpower to produce relative to the open web technology, current cold-forming technology does not satisfy the requirements to optimise material use throughout the length of the individual members of the joist. One of the disadvantages of continuous cold-forming from a single piece of sheet material resides in the fact that material use along the length of the individual members cannot be rationalised or optimised.
Accordingly a device and method of producing the device that can combine the beneficial attributes from each of the open web technology and cold-forming technology is desirable. It is also increasingly desirable to manufacture using cold-forming methods versus open-web welded methods as a means to reduce the need for labour shortages. Further, material optimisation is limited when cold-forming if the section is constant in weight throughout the length.
Also both open web and cold-form structures at times require bridging systems to stabilize the joist about the “Y” Axis. It is common practice to weld bridging in open web joists while cold-forming systems have bridging structures that commonly use screws for fastening.
Furthermore open web steel joists are traditionally assembled in a jig with a weld being applied at the juncture of the individual component parts; which prevents open web technology from using pre-finished materials as the welding process would damage the pre-finish. Furthermore, cold-formed joists are traditionally mechanically fastened which inherently helps prevent damage to the finished part.
It is an aspect of this invention to provide a joist comprised of at least one cold-formed elongated chord member, a segmented cold-form web, and fasteners for securing the web to the chord member. In one embodiment of the invention the web comprises a plurality of web members.
It is another aspect of this invention to provide a supporting surface defined by a plurality of joists, each of the joists comprising spaced cold-formed upper and lower metal chord members, a web comprising a plurality of web members intermediate the upper and lower chord member, and fasteners to fasten the web members to the upper and lower chords where the upper chords define a supporting surface.
It is a further aspect of this invention to provide a composite floor system comprising a plurality of metal joists, with the joists having, an upper chord member formed from sheet metal to present a vertical and horizontal upper cord extension, a lower chord member formed from sheet metal to present a horizontal lower chord extension, a plurality of web segments fastened together to define a substantially vertically disposed web, and mechanical fasteners to fasten the web to the spaced upper and lower chords; a concrete slab disposed on the upper chords of the plurality of joists with the vertical extension of the upper chord embedded in the concrete slab to define the composite floor.
Another aspect of this invention resides in a method of producing a joist comprising the steps of; forming upper and lower chords from sheet metal, forming at least one web member from sheet metal, fastening the web between the upper and lower chord with mechanical fasteners.
These and other objects and features of the invention shall now be described in relation to the following drawings:

BRIEF DESCRIPTION OF DRAWINGS

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.
FIG. 4 illustrates a segmented web.
FIG. 5 is a perspective view of the second embodiment of the invention showing a concentric or symmetrical cold-formed joist having a segmented web.
FIG. 6 is a side elevational view of FIG. 5.
FIG. 7 is a cross sectional view along the line 7-7 of FIG. 5.
FIG. 8 illustrates a side-view of a plurality of joists having bridging members.
FIG. 9 is a side view of a plurality of joists having crossed bridging members.
FIG. 10 is a perspective view of the symmetrical or concentric cold-formed joist to be used in a composite joist.
FIG. 11 is a side elevational view of FIG. 10.
FIG. 12 is a cross sectional view along the lines 12-12 of FIG. 10.
FIG. 13 is a side elevational view of a composite floor system having a plurality of joists.
FIG. 14 is a perspective view showing a top chord bearing condition of the joist.
FIG. 15 illustrates a perspective top chord extension condition.
FIG. 16 is a cross sectional view through line 16-16 of FIG. 6.
FIG. 17 is a cross sectional view along the line 17-17 of FIG. 6.
FIG. 18 is a partial side elevational view of a segmented web.
FIG. 19 is a partial top view of FIG. 18.
FIG. 20 is a top expanded view of region 20-20 shown in FIG. 18.
FIG. 21 is a partial side elevational view of the reinforcing member.
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 another embodiment of the joist.
FIG. 25 is a cross-sectional view of another embodiment of the invention.
FIG. 26 is a cross sectional view of another embodiment of the invention.
FIG. 27 is a cross-sectional view of another embodiment of the invention.
FIG. 28 is a schematic view of a roll forming machine.
FIG. 29 is a partial perspective view of a reinforced chord.
FIG. 30 is a side elevational view of another embodiment of the invention.
FIG. 31 is a partial enlarged view of FIG. 30.
FIG. 32 is a side elevational view of applications of the invention.
FIG. 33 is a chart showing man hours per ton vs joist span.
FIG. 34 is a chart showing percentage weight evaluation vs joist span.
FIG. 35 is another embodiment of the invention.
FIG. 36 a is a top plan view of the flap 82.
FIG. 36 b is a perspective view of a further reinforced flap.
FIG. 37 is a top plan view of a further reinforcing member.
FIG. 38 is another embodiment of the invention.
FIG. 39 is an end view of FIG. 38.

DETAILED DESCRIPTION OF THE INVENTION

In the description that follows, like parts are marked throughout the specification and the drawings with the same respective reference numbers. The drawings are not necessary 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 zig zag web 8 which is generally connected to the upper and lower chord assembly 6 by a number of means including welding or the like.
FIG. 2 illustrates a prior art cold formed joist construction 10 having a web portion 12 having a plurality of holes 14 disposed there through for receiving utility such as wire or the like.
FIG. 3 illustrates one embodiment of the invention which comprises an assembled joist 20 having a first or upper chord member 22 spaced from a second or lower chord member 24. A 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 (not shown), welding, rivets 30 or spot clinch 32 (FIG. 7).
The upper chord member 22 can be produced from a sheet of sheet metal. The sheet metal can be formed in a concentric fashion shown in FIG. 7 where the upper and lower chord members 22 and 24 are symmetrically disposed about web 26 or in an eccentric fashion shown in FIG. 25.
In one embodiment the upper chord member 22 is formed or bent to present a 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 is 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 symmetrically about the web 26 which defines “Y” axis 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 surface 22 to the right of the Y axis 27 in concert with the lower load bearing extension 38 defines a horizontal extension 44 disposed to the right side of the axis 27. The lower load bearing extensions 36 and 38 are bent to form to spaced apart web receiving tabs 46 and 48 as shown. The upper portion 50 of the web 26 includes a plurality of holes 52 which are adapted to receive the fastening means 28. FIG. 7 shows a fastening means 28 comprising a rivet 30.
The spot clinches 32 in combination with the cold-formed chords connect the two folded portions 34 and 36 and 38 and 44 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 extensions 56 and 58 symmetrically disposed about axis 27. The lower chord 54 in combination with the lower chord extension 56 and 58 define lower chord horizontal extensions 60 and 62 symmetrically disposed about the web 26. The 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 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. Furthermore, the holes 72 can include a lip 74 as shown in FIG. 16. The holes 72 lighten the total weight of the joist 20 while the lip 74 adds rigidity to the web structure 26 particularly in the “Y” axis.
The web 26 also includes a plurality of stiffening means 80 to stiffen the rigidity 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 26 being bent to form a stiffening tab 82 which is disposed at approximately a 90 degree angle from the web 26. The second stiffening means 84 generally consists of a hollow rib structure 86 as best illustrated in FIG. 21.
The hollow rib structure 86 can be produced by a variety of means and in one example 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 100 in a manner to be more fully particularized herein.
Furthermore, the web 26 can comprise of a plurality of web segments 104, 106 and 108 as shown in FIG. 4. Although only three segments are shown in FIG. 4 any number of segments can be used. Each of the web segments 104, 106 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 of sheet metal flaps which are bent at substantially 90 degrees from the web material 26. The first stiffening flaps 82 include a plurality of holes 110 which are adapted to receive fasteners such as rivets, nuts and bolts, or spot clinches to secure the plurality of web segments 104, 106, and 108 together to form a web 26. The web segments 104, 106, and 108 also include second stiffening means 84.
The web segments can either all have the same thickness or can 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 load-bearing load is greater at the ends than in the middle.
The joist shown in FIG. 5 can include angled end members 140 to secure the ends of the lower chord 24 and upper chord 22. Furthermore rigidifying members 150 may be added so as to present one end 152 fastened to the lower chord 24 and another end 154 fastened to the stiffening tab 82 as shown in FIG. 7.
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 floor or the like. Each of the joists 20 comprises of spaced cold-formed upper and lower chord members 22 and 24 and a web 26 intermediately upper and lower chord members 22 and 24. Fasteners 28 are utilised to fasten the web to the upper and lower chords; where the upper chords 22 define the supporting surface.
A plurality of bridging members 1700 may be used to connect adjacent joists 20 together as shown so as to stiffen the joist 20 in the “Y” axis. Parallel bridges 170 may be used as shown in FIG. 8 along with criss-crossed bridges 172 that are appropriately fastened at 174 as shown in FIG. 9.
The bridge members 170 can comprise of L-shaped sheet metal. Bridging member 170 can be made from sheet material which is bent 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 172 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. In particular, the upper chord 22 can be formed 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 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 the concrete 200, a very solid composite floor system is produced. The vertical extension 194 can also include a generally horizontal concrete engaging extension 202 which runs along the length of the chord 22. Since the horizontal concrete engaging extension 202 runs along the length L of the chord 22, the possibility of snagging a worker's foot or pant trouser 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 is increased by using rivets spot clinches 32 or the like to increase the surface area of contact.
FIG. 24 illustrates another embodiment of the invention which includes an upper cold-formed chord 22 fastened to a web 26 by fasteners 30. In the embodiment shown on FIG. 25, the bottom chord 24 is formed so as to present one horizontal extension 250 which is doubled upon itself and hole clinched; while the other horizontal extension 252 presents a single section of sheet metal.
A further embodiment of the invention is shown in FIG. 25 where the lower chord member 24 is a bent extension of the web 26.
FIG. 26 illustrates another embodiment of the invention where the upper chord 22 has a single layer of sheet metal which is bent to produce the horizontal extensions 42 and 44 spaced apart to accommodate the end 50 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.
FIG. 27 illustrates a further embodiment of the invention whereby the lower chord 24 is a bent extension of the bottom of the web 26.
FIG. 29 illustrates that a chord member can include a cold-formed reinforcing section 300 which consists of sheet metal that is formed so as to present a lower chord reinforcing section, 302 and an upper chord reinforcing section 304 adapted to embrace a portion of one of the chords 22 and 24 as shown. Alternatively, the reinforcing section 300 may extend along the full length of the chord member 22 and 24 as desired. The reinforcing portion 300 may be utilized to as to increase the strength of the chord member 22 and 24 as a desired position. Generally speaking, the ends of the chord members 22 and 24 may be reinforced as this is where the maximum load bearing stress occurs.
The chord members 22 and 24 extend longitudinally along a Length thereof which presents a first portion 310 having a first thickness FT and a second portion 320 having a second thickness ST.
FIG. 14 illustrates that the ends 300 of the upper chord 22 can include support shoes 302. The support shoes can be comprised of sheet metal which are bent to present horizontal support shoe member 304 and a vertical support shoe member 306 having a plurality of holes 308 aligned with holes presented at the ends 300 of upper chord member 22 so as to fasten the support shoe 302 thereto. The support shoe 302 can be utilized when the joist 20 is supported by the ends 300 of the upper chord member 22. Reinforcing gussets 310 can be formed so as to add strength to the structure.
FIG. 15 illustrates a top chord extension condition whereby a support shoe 302 is spaced from the end 300 of the upper chord member 22 so as to present an extension 312 that can be utilized in a variety of conditions including that of manufacturing and eave structure.
Alternatively the joist 20 can be supported along the bottom chord 24 as shown in FIG. 30 in a bottom chord bearing condition. FIG. 30 illustrates a cold form composite joist 20 supported along the bottom chord 24.
In particular the ends 400 of the joist are disposed within the lower stud wall 402 and upper stud wall 404 as shown. The lower stud wall 402 includes a stud wall track 406 which is generally a flat piece of sheet metal 408 bent at its ends so as to present a solid surface to the joist. The upper stud wall 402 includes a similar stud wall track 406. The stud wall 402 and 404 also includes a floor joist track 412 adjacent the end 400 of joist 20.
The cross-section of the joist 20 seen in FIG. 30 can have any number of cross sections as described in the context of the composite joist including that shown in FIG. 12. The composite joist is constructed in the manner previously described. An erection clip 414 can be utilized 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 is poured the composite cold formed steel joist is supported by the bottom chord 24 at the ends 400 of the joist 20.
FIG. 35 illustrates another embodiment of the invention utilizing concentric cold-formed joists which are bottom chord supporting in a residential home.
In particular the joist 20 rests on a foundation 402 having a support 410. The end 400 of the joist 20 includes a reinforced flap 82 which is further particularized in FIGS. 36 a and 36 b. 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. Thereafter portions 620 and 622 are further folded along fold lines 621 and 623 so as to present wing portions 624 and 626 which are adapted to contact the lower surface of upper chord member 22 and lower surface of lower 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 rigidify and strengthen the joist 20.
Wooden or metal backing plates 412 are also utilized as shown in FIG. 35. Wooden pieces 414 may also be utilized as shown. The upper chord 22 produces a support surface for supporting plywood 416 or the like.
Further 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 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 another embodiment of a load bearing bottom chord utilizing the rigidifying structure 700 shown in FIG. 37.
FIG. 28 generally illustrates the method of producing the cold-formed joist. The upper chord 22 can be produced from unrolling a roll of sheet metal 112 along path 114 to a roll forming machine 116 such as sold by Samco machinery located in Toronto, Canada. The roll 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 roll of sheet metal 118 and flattening same along a path 120 to a roll forming machine 116 and cut to the desired length. Furthermore, the web 26 can also be produced by unwinding a roll of sheet metal 122 and flattening same at flattening station 123. A shear 125 can be used so as to shear the web member 26 to its desired length. Thereafter, the web 26 approaches stiffening section 128 so as to produce 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 in the second stiffening means 84 as described above in a drawing operation.
The sheet metal at stations 112, 118 and 122 can be galvanized or painted as desired prior to the forming process. Furthermore the roll forming machine 116 includes 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 of the prior art joists included a cambering of the upper and lower chords 22 and 24 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 separately. Once the upper and lower chord members 22 and 24 are cambered they can be attached to the web 26 as described. Since the web 26 is not part of the upper and lower chord members 22 and 24 during the cambering process there is less resistance to the cambering.
Furthermore, the composite joist as described herein exhibits excellent resistance to shear forces due to the presence of fastening means 30 and particularly when utilizing spot clinches.
The support structures described herein can be utilized either as floor joists 500 or roof joists 502 as shown in FIG. 32 whether for office, multi-residential, retail or warehouse facilities.
Furthermore FIG. 33 illustrates an example of a comparison between the number of man hours per ton to produce prior art composite open web steel joist (composite OWSJ), a prior art open web steel joist (OWSJ) and applicants concentric or symmetrically disposed cold formed joist (CCFJ) and a prior art C-shaped joist represented by FIG. 2. Savings can be experienced using the invention described herein.
Furthermore, FIG. 34 illustrates a comparison of a prior art OWSJ, prior art composite OWSJ, and a prior art C-shaped joist vs. the invention described herein between applicants concentric cold formed joist and segmented concentric cold formed joist in connection with performance as a percentage of weight of valuation.
Although the preferred embodiment as well as the operation and use have been specifically described in relation to the drawings, it should be understood that variations in the preferred embodiment could be achieved by a person skilled in the art without departing from the spirit of the invention as claimed herein.

Claims

1. A joist comprised of:

(a) at least one cold-formed elongated chord member;

(b) a cold-formed web having a plurality of web members;

(c) means for securing said web to said chord member.

2. A joist as claimed in claim 1 comprising a first and second spaced cold-formed chord member with said web secured to said spaced first and second chord members.

3. A joist as claimed in claim 2 wherein said securing means comprises fasteners.

4. A joist as claimed in claim 3 wherein said web includes stiffening means.

5. A joist as claimed in claim 4 wherein said web comprises a plurality of web members fastened together.

6. A joist as claimed in claim 5 wherein said web members are segmented.

7. A joist as claimed in claim 6 wherein one of said web members has a different thickness than the remaining web members.

8. A joist as claimed in claim 7 wherein each said web segments includes said stiffening means and said stiffening means comprised a first stiffening means at each end of said web segments, and a second stiffening means disposed intermediate said ends of said web segments.

9. A joist as claimed in claim 8 wherein said second stiffening means include holes adapted to receive bridging means.

10. A supporting surface comprising a plurality of joist, each said joist comprised of:

(a) spaced cold-formed upper and lower metal chord members;

(b) a web intermediate said upper and lower chord members;

(c) fasteners to fasten said web to said upper and lower chord members;

said upper chords disposed in a plane defining said supporting surface.

11. A supporting surface as claimed in claim 10 wherein said web comprises a plurality of web segments, said segments fastened together by mechanical fastening means.

12. A supporting surface as claimed in claim 11 wherein said web segments and upper and lower chord members are coated with a coating material.

13. A supporting surface as claimed in claim 12 wherein at least one of said web segments includes an opening there through, and a stiffening recess for stiffening said web segment.

14. A supporting surface as claimed in claim 13 wherein said stiffening means includes at least one hole adapted to receive a bridging member for bridging adjacent joist together.

15. A supporting surface as claimed in claim 14 wherein one of said web segments has a different thickness than said other web segments.

16. A supporting surface as claimed in claim 15 wherein said chord segments extend longitudinally along a length thereof and said web segments disposed adjacent said ends of said chord members have a greater thickness than said web segments disposed intermediate said ends.

17. A supporting surface as claimed in claim 16 where at least one of said chord members has a length presenting a first portion with a first thickness and a second portion with a second thickness.

18. A supporting surface as claimed in claim 17 wherein said upper and lower chord members each present a horizontal chord extension.

19. A supporting surface as claimed in claim 18 wherein said horizontal chord extensions are disposed symmetrically about said web.

20. A supporting surface as claimed in claim 19 wherein said upper chord member further includes a vertical extension.

21. A supporting surface as claimed in claim 20 wherein said horizontal extensions of said upper chord are adapted to support a deck.

22. A supporting surface as claimed in claim 21 wherein said deck includes composite concrete slab having said vertical said extensions of said upper chord disposed therein.

23. A supporting surface as claimed in claim 22 wherein said vertical extension includes a spot clinch.

24. A composite floor system comprising:

(a) a plurality of metal joist, said joist comprising:

(i) an upper chord member formed from sheet metal to present a vertical chord extension and horizontal upper chord extensions symmetrically disposed about said vertical extension.

(ii) a lower chord member formed from sheet metal to present a horizontal lower chord extension.

(iii) a plurality of web segments fastened together to define a substantially vertically disposed web.

(iv) mechanical fasteners to fasten said web to said spaced upper and lower chords.

(v) a concrete slab disposed on said upper chord of said plurality of joist with said vertical extension of said upper chord embedded in said concrete slab to define said composite floor.

25. A composite floor system as claimed in claim 24 or in said upper and lower chord members and said web segments are painted.

26. A composite floor system as claimed in claim 25 or in said mechanical fasteners comprised rivets.

27. A composite floor system as claimed in claim 26 wherein one of said web segments has a thickness greater than said other web segments.

28. A composite floor system as claimed in claim 27 wherein at least one of said chord members has a first portion with a first thickness and a second portion with a second thickness.

29. A composite floor system as claimed in claim 28 wherein one of said extensions of said upper chord member includes a spot clinch.

30. A method of producing a joist comprising the steps of:

(a) forming upper and lower chords from sheet metal;

(b) forming at least one web member from sheet metal;

(c) fastening said web between said upper and lower chords with mechanical fasteners.

31. A method is claimed in claim 30 wherein said web, and upper and lower chords are painted prior to said fastening step.

32. A method is claimed in claim 31 wherein said web, and upper and lower chords are painted prior to said forming steps.

33. A method is claimed in claim 32 wherein such sheet metal forming said web and upper and lower chords is stamped to produce holes adapted to receive said fasteners.

34. A method is claimed in claim 33 including a step of forming a plurality of web members fastened together to define a web.

35. A method is claimed in claim 34 wherein said web members are selected with different web thickness.

36. A method is claimed in claim 35 wherein said chord members include reinforced sections to accommodate greater loads.

37. A joist as claimed in claim 6 wherein opposite ends of said upper chord are adapted to be load bearing.

38. A joist as claimed in claim 6 wherein opposite ends of said lower chord are adapted to be load bearing.

39. A joist comprised of:

(a) at least one cold formed elongated chord member;

(b) a cold formed web having a stiffening recess

(c) means for securing said web to said chord member.