Unitary steel joist

A unitary steel joist includes a generally vertical web, a generally horizontal bottom flange, a generally horizontal top flange, a bottom wing, a bottom web portion, a top wing and a top web portion. The generally horizontal bottom flange extends outwardly on each side of the web. The bottom flange is made of two pieces of steel. The generally horizontal top flange extends outwardly on each side of the web. The top flange is made of two pieces of steel. The bottom wing extends outwardly from the web. The bottom web portion extends between the bottom flange and bottom wing. The top wing extends outwardly from the web. The top web portion extends between the top flange and the top wing. The unitary steel joist is made from a unitary piece of steel.

FIELD OF THE INVENTION

This invention relates to steel joist and in particular steel cold rolled steel joist constructed from a unitary piece of steel with stiffening wings and snap-in-place bridging.

BACKGROUND OF THE INVENTION

In the past many innovative joist solutions have been created to improve the performance of floor joists for residential buildings.

Today house framing in North America is predominantly wood construction. The wood industry provides an I-Wood section that has the predominant market share in North America. The I-Wood joist is typically comprised of solid wood chord members that are adhered to a web that is a laminated chip board type member. Wood joists have a cost advantage over steel because the installation price for wood is less than steel. When housing construction is slow in North America the price for wood products goes very low, so it becomes very hard for steel to compete with wood for non rated floors based on cost.

Steel floor joist construction is gaining popularity now, the Light Steel Frame (LSF) industry has spent the last several years training framers, engineers, architects and contractors about steel framing. Today the market is predominantly cost based; owners and contractors typically build the cheapest way possible. For steel there have been many innovations improving the method of installation and the provision for follow up trades based on using various C-Shape designs. Although there have been considerable improvements, the use of steel joists has not reached a point wherein they are considered a mainstream method for building. In North America I-Wood joists have predominant market share in the framing market because the site laborers are typically trained for building with wood and because the required tools are on hand. For steel joists Standardized Connectors and Snap-in bridging assist with simplifying installation so that steel can be more competitive with wood. Where I-Wood is most competitive, at spans 16 ft and less for non rated floors, up until the present invention steel beam options have not presented cost efficient alternatives.

For fire and acoustic rated floors, I-Wood joists do not perform as well as solid wood joists or steel joists in certain situations. I-Wood joists face increasing criticism from Fire Officials in North America because installed joists have not performed well under real fire conditions. These I-Wood joist floors have caused injuries, and sometimes fatalities to fire fighters in North America every year where they have fallen through the floors when the joists have failed without warning during a fire. This faulty performance has resulted in calls from Fire Officials to sanction the I-Wood joists or improve their structural performance in fire. As can be seen in theFIG. 1showing a chart titled ‘Compare Results of ULC-S101 (Full-Scale Fire Resistance Tests), the I-Shaped steel joists (sold under the trademark iSpan™) outperformed the I-Wood joists in these fire tests. This better performance is significant to Fire Officials since the failure mode of the I-Shaped steel joist is typical of what they have experienced with solid wood joists in the past.FIG. 2shows the structural members that were compared. Specifically (a) shows the I-wood joist; (b) the C-shaped steel joist; (c) the I-shaped steel joist sold under the trademark iSpan™; and (d) the solid wood joist. Note in the chart the rapid failure to carry load for the tested I-Wood joist and the more gradual failure of the tested I-Shaped steel joist.

Accordingly, an I-Shaped steel joist that performs well in a fire and is cost competitive would be advantageous for competing in short span wood applications.

SUMMARY OF THE INVENTION

The present invention relates to a unitary steel joist unitary steel joist comprising:

a generally vertical web;

a generally horizontal bottom flange extending outwardly on each side of the web, the bottom flange being made of two pieces of steel;

a generally horizontal top flange extending outwardly on each side of the web, the top flange being made of two pieces of steel;

a bottom wing extending outwardly from the web;

a bottom web portion extending between the bottom flange and the bottom wing;

a top wing extending outwardly from the web;

a top web portion extending between the top flange and the top wing;

and whereby the unitary steel joist being made from a unitary piece of steel.

The bottom wing and the top wing may be on the same side of the web.

The bottom wing and the top wing may be on opposite sides of the web.

The web may further include a plurality of utility holes formed therein. Each utility hole may have a lip around the perimeter thereof.

The unitary steel joist may further include a plurality of stitching holes formed in the web.

The plurality of stitching holes may be positioned in one of:

the web between the bottom flange and the bottom wing and wherein the stitching holes also extend through the bottom web portion;

the web between the top flange and the top wing and wherein the stitching holes also extend through the top web portion; and

a combination thereof.

According to one aspect of the invention, one of the bottom wing and the top wing may further include a plurality of holes formed therein.

According to another aspect of the invention, both the top wing and the bottom wing may further include a plurality of holes formed therein.

The unitary steel joist may be a first steel joist and further include a plurality of steel joists to form a steel floor. The unitary steel joist may further include snap-in-place bridging and the snap-in-place bridging may be adapted to engage the holes in the wings and adapted to be positioned between adjacent unitary steel joists.

The snap-in-place bridging may have a generally triangular face, a generally horizontal edge portion on one side thereof, an angled edge portion on another side thereof and a generally vertical portion on the third side thereof. The snap-in-place bridging may include a first generally horizontal piece and an angled piece. The generally horizontal piece may extend between two adjacent unitary steel joists and engage the holes formed in the upper wings of the adjacent unitary steel joists. Further, the generally horizontal piece may also include a plurality of holes formed therein and the angled piece may engage the holes in the generally horizontal piece on one side thereof and engage the holes in the wings of the unitary steel joist on the other side thereof.

Each web of the unitary steel joist may include a plurality of holes in the bottom and the top thereof proximate to the upper and lower wings and one side of the generally horizontal piece may engage the holes in the web and the other side may engage the holes in the wings. The generally horizontal piece may further include a plurality of holes formed therein and the angled piece may engage the holes in the generally horizontal piece on one side thereof and engage the holes in the web of the unitary steel joist on the other side thereof.

In another embodiment, the unitary steel joist may be a first steel joist and further include a plurality of steel joists to form a steel floor, where the unitary steel joist may further include bridging members wherein each bridging member may be adapted to be received in the stitching holes and to span between adjacent unitary steel joists.

Each bridging member may include through tab adapted to extend through the stitching hole. Each bridging member may further include one of side tabs, upper tab and a combination thereof. The unitary steel joist may further include a unistrut pipe hanger attached to the bridging member. The bridging member may be an upper bridging member and may further include a lower bridging member attached between adjacent unitary steel joists and spaced downwardly from the upper bridging member. The unitary steel joist may further include at least one partial blocking panel extending between the upper and lower bridging members. The bridging member may include a full blocking panel. The full blocking panel may have a utility hole formed therein. The unitary steel joist may further include squash blocking.

DETAILED DESCRIPTION OF THE INVENTION

Generally speaking, the systems described herein are directed to unitary steel joists. As required, embodiments of the present invention are disclosed herein. However, the disclosed embodiments are merely exemplary, and it should be understood that the invention may be embodied in many various and alternative forms.

The Figures are not to scale and some features may be exaggerated or minimized to show details of particular elements while related elements may have been eliminated to prevent obscuring novel aspects. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention. For purposes of teaching and not limitation, the illustrated embodiments are directed to unitary steel joists.

FIG. 3(a), (b), (c) and (d) show four alternate embodiments of the unitary joist of the present invention. Unitary joist10is constructed from a unitary piece of steel and is cold rolled into the shape shown herein.

The unitary joist10includes a lower wing12, a lower web portion14, a lower flange16, a web18, an upper flange20, an upper web portion22and an upper wing24. The lower wing12extends outwardly from the web18. The lower web portion14extends generally downwardly from the lower wing12and is generally parallel to and adjacent to the web18. The lower flange16is generally orthogonal to the web18and has a double thickness. Similarly, in one embodiment the upper wing24extends outwardly from the web18on the opposite side thereof from the lower wing12. The upper web portion22extends generally upwardly from the upper wing24and is generally parallel to and adjacent to the web18. In another embodiment, as shown inFIG. 3(d) at25the upper wing24extends outwardly from the web on the same side as the lower wing12.

Unitary joist25offers and alternative wherein the web18has a face that is unobstructed. This allows for the attachment of connectors, squash blocks and stiffeners on the unobstructed face27of the web18. Preferably the utility holes and their stiffening and the stitching connectors are on the opposite side from the unobstructed face27of the web18.

The size of the wings12and24may vary. As shown inFIG. 3(c) unitary joist26may include truncated lower wing28and upper wing30. Further, as shown inFIG. 3(b) the lower web portion14and the upper web portion22are each fastened32to the web by way of welding, spot welds, screws, rivets, clinching, stitching.

Preferably upper wings24and lower wings12have a plurality of holes34formed therein as best seen inFIGS. 4 and 9. Holes34may be in the shape of slots as shown herein, however they may also have other shapes. Holes34are adapted to receive snap-in-place bridging40or other accessories that may also be snapped into place. In addition the web18may have a plurality of holes38formed therein as shown inFIG. 11which are adapted to receive an alternate embodiment of snap-in-place bridging75. Holes38are formed in the top and the bottom of the web18proximate to the upper24and lower12wings.

Web18may be provided with a plurality of utility holes41as shown inFIGS. 7,911, and12. Utility hole41has a lip43around the perimeter thereof that extends outwardly. Utility hole41allows for easy passage of pipes, wires and other cables. Lip43serves to reinforce the web.

It will be appreciated by those skilled in the art that the upper12and lower24wings provide stiffening. As well where the steel is doubled in the upper20and lower16flanges and the upper web portion22and lower web portion14stiffening is provided. With doubling material on the top and bottom of joist the effective web height may be shortened. As well the doubling of material provides additional capacity against web crippling for thin materials.

As shown inFIGS. 4,5and11, the unitary steel joist10of the present invention may be positioned over centre supports42(FIG. 4) or supported by a wood header44(FIG. 5). Adjacent joists10may have a connector46to attach adjacent joists together. As well centre support connectors48may be used to connect joist10to centre supports42. Preferably centre support connectors48are snap-in-place connectors connectable to the plurality of holes34in the wings. Adjustable connectors50may be used to connect joist10to wood headers44.

Joists10are designed to be used with snap-in-place bridging40. Three different embodiments of snap-in-place bridging are shown herein and will be described below. Referring toFIGS. 6 and 7, snap-in-place bridging40includes a generally a generally triangular face52, a generally horizontal edge portion54on one side thereof, an angled edge portion56on another side thereof, and a generally vertical edge58on the third side thereof. Snap-in-place teeth60extend from one side of the generally horizontal edge54and a spacing/fastener tab62extends from the other side thereof. As well, snap-in-place teeth extend from the generally vertical edge58. Snap-in-place teeth60are adapted to be received into holes34in upper24and lower wings12. Face52may have a utility hole64formed therein. The snap-in-place bridging40may be positioned such that generally horizontal edge54is at the top as shown inFIG. 7(a) alternatively it can be positioned such that it is along the bottom as shown inFIG. 7(b). As a further alternative a pair of snap in place bridging40may be placed adjacent to each other as shown inFIG. 7(c). In this latter embodiment the two snap-in-place bridging40serve as structural blocking.

An alternate embodiment of snap-in-place bridging65is shown inFIG. 9. Snap-in-place bridging65includes a generally horizontal piece68shown inFIG. 8(b) and an angled piece66shown inFIG. 8(a). Top piece68has snap-in-place teeth60on each end thereof and a plurality of holes70. Angled piece66has bridging teeth72on each end thereof. Bridging teeth72are adapted to engage the holes34in unitary steel joist10at one end thereof and holes70in top piece68at the other end thereof as shown inFIG. 9.

An alternate embodiment of snap-in-place bridging75is shown inFIG. 11. Snap-in-place bridging75includes a generally horizontal piece76shown inFIG. 10(b) and an angled piece74shown inFIG. 10(a). Top piece76is similar to top piece68but it has snap-in-place teeth60on one end thereof, extensions80on the other end thereof and a plurality of holes78. Angled piece74has top bridging teeth82on one end thereof and lower bridging teeth84on the other end thereof. Extensions80are adapted to extend through holes38in web18of unitary steel joist10on one side thereof and snap-in-place teeth60are adapted to engage holes34in wings of unitary steel joist10. Top bridging teeth82are adapted to engage the holes78in top piece76and bottom bridging teeth84are adapted to engage holes38in web18as shown inFIG. 11.

As shown inFIG. 12a plurality of unitary steel joists10may be used to create a floor.

The embodiments of the unitary steel joist of the present invention are made of steel to enhance fire performance. Unitary steel joist are substantially an I-Section because it is an efficient shape structurally, and the joist includes a method for snap-in bridging and modular parts so it goes together easily. This new invention provides an I-Shaped metal joist that includes modular snap-in bridging to simplify site assemble and reduce costs. It uses only a single piece of strip width for the joist section to be produced and therefore it may be cold formed into the shapes described above, so the cost to manufacture is very low.

The wings in an embodiment of the steel joist of the present invention has been developed to specifically increase the flange to web weight ratio, while shortening the effective web height. This method of building a joist allows the structural member to perform in a structurally superior manner while providing the installers with the advantage of having snap-in bridging. The method of manufacturing the new joists shown in this invention will reduce manufacture costs; the unique shape will reduce material use and simplify the site installer's work. The result is a steel floor joist system that is very competitive with I-Wood for spans of 10 ft to 22 ft. This method will also compete more efficiently in the 23 ft to 30 ft span range.

Another advantage of this invention for house framing is that an I-Shaped joist outperforms C-Shape steel joists in a strength to mass comparison, see chart shown inFIG. 13taken from a comparative analysis of I-Shape section properties versus C-Shape section properties. The embodiments of the unitary steel joist of the present invention provide the steel industry with the opportunity to compete with the I-Wood joist market by virtue of outperforming on costing as well as fire performance.

As shown inFIGS. 14 and 15, stitching holes100may be provided in the lower web portion14or upper web portion22as an alternate for attaching bridging members. Stitching holes100may be used in addition to or alternatively to holes34in the wings. Stitching holes100are adapted to receive bridging members. Preferably stitching holes100are constructed by cutting a hole in the web18and then folding the material back. Preferably the material is folded back on the side opposite from the unobstructed face27of the web18.

Referring toFIGS. 16 to 18an alternate bridging member102is shown which is for use in association with stitching holes100. Bridging member102is adapted to pass through stitching holes100. Bridging member102includes through tabs104adapted to pass through stitching holes100. Through tabs104may have various configurations to provide a lock so that bridging member snaps in place. Bridging member102may also have side tabs106and an upper tab108. Side tabs106and upper tab108may be provided with holes110that are adapted to receive a bolt.

Referring toFIGS. 19 and 20bridging members102may be used in association with unistrut members.FIG. 19shows a Unistrut hanger120inserted in the bridging section102.FIG. 20shows a unistrut pipe hanger120attached to a bridging member102.FIG. 20shows a pipe122in pipe hanger120.

Referring toFIGS. 21 to 27, joist25is shown attached to different types of walls and supports. Unitary steel joist25has top24and bottom12wings on the same side of web18. Joist25has an unobstructed face27on one side of the web18. Unobstructed face allows for a full height web stiffener126. Web stiffener126has a plurality of holes128formed therein. Web stiffener126has lips130formed on each side thereof. Since unitary steel joist25has an unobstructed face27, there is provided access to one side of the bottom flange16thereby facilitating fastening to beam or wall therebelow.FIG. 23shows unitary steel joist attached to a wood sill132with a fastener134.

FIGS. 24 and 25show a unitary steel joist25having top and bottom wings on the same side attached to a wall having a wood sill136. The unobstructed face27of web18allows for squash blocking138for platform framing. The squash blocking is generally L-shaped having one side adapted to be attached to unitary steel beam25and the other side attached to vertical rim joist140. Squash blocking138has a plurality of holes142formed therein for receiving fasteners therein. A pair of adjustment slots144are also formed in the squash blocking and are similarly adapted to receive fasteners.

FIGS. 27 and 28show a unitary steel joist having top and bottom wings on the same side attached to a distribution member on a steel frame wall.

FIG. 28is a perspective view of a joist system using an embodiment of unitary steel joist having top and bottom wings on the same side and showing an upper and lower bridging member.

FIG. 29is a perspective view of a joist system using an embodiment of unitary steel joist having top and bottom wings on the same side and showing an upper and lower bridging member similar to that shown inFIG. 28but also showing partial blocking panels.

FIG. 30is a perspective view of a joist system using an embodiment of unitary steel joist having top and bottom wings on the same side and showing a bridging member with a full blocking panel having a utility hole therein.

FIG. 31is a perspective view of a joist system using a plurality of unitary steel joist having top and bottom wings on the same side and plurality of bridging members.

As used herein, the terms “comprises” and “comprising” are to construed as 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.