Joist shoe for steel joists

Abstract

A joist shoe for a steel joist is provided. The shoe comprises a top plate, an upstand, a backspan and a vertical load transfer plate. The back span that is planar with a rear portion fastenable to a top chord of the steel joist and a front portion extending past the end of the steel joist. The upstand is fastened to an end of a top side of the front portion of the top plate and is substantially vertical. The backspan is fastened to a bottom side of the top plate and extends downwardly and is fastened to a web on the steel joist. A front edge of the backspan is adjacent to the bottom side of the front portion of the top plate and tapers down to a bottom edge of the backspan such that the front edge and bottom edge of the backspan form a corner that would be substantially adjacent with the web of the steel joist. The vertical load transfer plate is fastened to the bottom side of the front portion of the top plate and the tapered front edge of the backspan. The vertical load transfer plate is fastened substantially perpendicular to the tapered front edge of the backspan.

Description

JOIST SHOE FOR STEEL JOISTSFIELD OF THE INVENTION

[0001] The present invention relates to a novel joist shoe which enables cold formed steel roll formed joists to be top chord bearing.BACKGROUND OF THE INVENTION

[0002] Joists are predominantly used in the construction industry to span a distance and provide a surface for a floor, roof or the like. Cold rolled steel joist are designed to be used as bottom chord bearing joists.

[0003] Due to their relatively simple design, unitary steel joists can be mass produced but are not designed to be used as top chord bearing joists. As such, being able to convert unitary steel joists into top bearing steel joists that can appropriately increase end reaction load capacity capabilities would be a significant advantage.

[0004] The current methods in the field involve manufacturing steel joists which are top chord bearing, but this method involves redesigning the joists themselves.

[0005] Other methods involve attaching a shoe to a joist, but current methods have several pitfalls, including the use of welding to distribute stresses throughout the connection in current shoes. This presents a variety of problems, such as inconsistent welds, issues with welding thinner steels and the like.

[0006] The problems with welding can be overcome by mechanical fastening, by using rivets, bolts or similar methods, which is advantageous due to easier and more consistent implementation, particularly when fastening to galvanized sheet steel. For thinner steels, this has presented a problem as the strength of the fastener is significantly less than welding.

[0007] In order to create a top chord bearing joist, the top of the joist must extend outward toward the support. This extension invariably results in bending I rotation of the shoe, which significantly amplifies the forces that must be resisted by the fasteners in the web of the joist.

[0008] In order to allow the mechanical fastener to be feasible, a truss like configuration has been created with a novel shoe assembly. This reduces rotation of the shoe and the amplification effects rotation has on the stresses at the mechanical fastener.SUMMARY

[0009] The present disclosure relates to a joist shoe to be fastened to a cold rolled steel joist allowing the steel joist to become top chord bearing. The joist shoe has a top plate which is planar with a rear portion fastened to a top chord of the steel joist and a front portion extending past the end of the steel joist. The front portion of the top plate has an upstand positioned at the end of the front portion of the top plate and extends vertically from the top side. A backspan is fastened to a bottom side of the top plate and extends downwardly and is fastened to a web on the steel joist such that the front edge of the backspan is adjacent to the bottom side of the front portion of the top plate and tapers down to a bottom edge of the backspan such that the front edge and bottom edge of the backspan form a corner that is substantially flush with the web of the steel joist. The vertical load transfer plate is fastened to the bottom side of the front portion of the top plate and the tapered front edge of the backspan such that the vertical load transfer plate is fastened substantially perpendicular to the tapered front edge of the backspan.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The embodimentswill now be described byway ofexample only, with reference to the accompanying drawings, in which:

[0011] Figure 1 is a perspective view of a joist framed flooring system;

[0012] Figure 2 is a perspective side view of the joist shoe installed on a cold rolled steel joist;

[0013] Figure 3 is a schematic showing layer slippage in non-composite bending systems;

[0014] Figure 4 is a rear view of the joist shoe installed on a cold rolled steel joist;

[0015] Figure 5 is a worm’s eye view of the joist shoe installed on a cold rolled steel joist;

[0016] Figure 6 Is a front view of the joist shoe installed on a cold rolled steel joist;

[0017] Figure 7 is a side view of the joist shoe installed on a cold rolled steel joist;

[0018] Figure 8 is an alternate side view of the joist shoe installed on a cold rolled steel joist;

[0019] Figure 9 is a bird’s eye view of the joist shoe installed on a cold rolled steel joist;

[0020] Figure 10 is a perspective side view of an embodiment of the joist shoe installed on a cold rolled steel joist;

[0021] Figure 11 is a perspective view of an embodiment of the joist shoe having stops installed on a cold rolled steel joist;

[0022] Figure 12 is a cross-sectional view of the flooring assembly;

[0023] Figure 13a is a perspective view of an embodiment of the joist shoe installed on a cold rolled steel joist having a first embodiment of stops;

[0024] Figure 13b is a perspective view of an embodiment of the joist shoe installed on a cold rolled steel joist having a second embodiment of stops;

[0025] Figure 13c is a perspective view of an embodiment of the joist shoe installed on a cold rolled steel joist having a third embodiment of stops; and

[0026] Figure 13d is a perspective view of an embodiment of the joist shoe installed on a cold rolled steel joist having a fourth embodiment of stops.DETAILED DESCRIPTION

[0027] Figure 1 shows a perspective view of a joist framed flooring system 2. The joist framed flooring system 2 comprises a series of joists 6 which provide support to the floor between load bearing walls and structural beams (shown as reference character 3 on Figure 1). A joist shoe 10 is fastened to the ends of the joist as shown in Figure 2. The shoe 10 is used to fasten the joists 6 to the load bearing wall or structural beam 3. A deck 4 is fastened on top of the joists 6 to provide a base of support for a concrete floor 8.

[0028] The floor joist system described herein is advantageous in that it creates a composite action between the system components. Composite action occurs when different materials are sufficiently connected as to act as a single unit from a structural point of view. If the structural slab were placed on the steel joists without sufficient connection, the slab would act as a dead weight on the joist but not contribute to the system’s overall strength or stiffness. By sufficiently connecting the joist and the slab together, the strength of the composite joist and concrete system is stronger and stiffer than the joist alone, leading to improved performance and reduced cost of construction. After the deck 4 is fully installed on the joists6, concrete 8 is placed over the deck and cured. The concrete 8 encases the shoe 10 above the joist 6. Once cured, the shoe 10 is anchored into the concrete 8. When different layers in a floor bend, the layers tend to slip along their interface as shown in Figure 3. Given that the shoe is connected to the joist and anchored into the concrete, the system resists the slippage between layers of construction (see Figure 3), thereby making the materials work together compositely.

[0029] With reference to Figures 2, and 4 to 9, the shoe is shown generally at 10. The shoe 10 comprises a top plate 16, which is further comprised of a rear portion 12 and front portion 14, which allows for support of a deck atop a steel joist to be continuous over the top of the shoe. The rear portion 12 may be prefabricated with one or more holes (12a, shown in Figure 9), which assist in securing the shoe 10 to the top chord of the joist. The shoe can be fastened to the joist by any suitable method including, but not limited to, riveting, screwing, welding, self drilling screws, and power actuated fasteners. The front portion 14 may further comprise one or more holes for coupling the front portion 14 to a supporting member, such as a beam. In a preferred embodiment, bolts or screws are used to fastened the front portion 14 to the support member, however, it can be appreciated that other suitable fastening methods would be known to a person skilled in the art.

[0030] An upstand 18 is connected to the end of the front portion 14 and is generally vertical. The upstand 18 may be prefabricated with one of more holes 18a, which assist in installation of accessory components such as shoe extensions. The upstand 18 may be a separate component that is affixed to the front portion 14, for example by welding, or may be an extension of the top plate 16 that is mechanically bent into the desired position. The upstand 18 at end of top plate 16 functions to restrain horizontal slab shear and assists in creating composite action between the joist and the concrete slab that is placed on top of the joist.

[0031] A backspan 22 is connected and is perpendicular to the underside of the top plate 16, such that a top edge 22a of the backspan 22 extends across the underside of the rear portion 12 and front portion 14. The tapered front edge 22b of the backspan 22 angles down from the underside of the front portion 14 to the bottom edge 22c of the backspan 22 such that where the bottom edge 22c and the tapered front edge 22b meet is essentially flush with the end of the steel joist. The backspan 22 may be prefabricated with one or more holes 22d that assist in connecting the backspan 22 to the web of the steel joist 30. The backspan 22 functions to restrain horizontal slab shear and assists in creating composite action between the joist and the concrete slab that is placed on top of the joist, as well as transfers vertical stresses into the web of the joist.

[0032] A vertical load transfer plate 20 is fastened to the bottom side of the front portion 14 of the top plate 16 and the tapered front edge 22b of the backspan 22 such that the vertical load transfer plate 20 is fastened substantially perpendicular to the tapered front edge 22b of the backspan 22. The width of the vertical load transfer plate 20 may be the same width or narrower than the front portion 14 of the top plate 16 across its entire length, and may taper in width, such that the top is widerthan the bottom. The vertical load transfer plate 20 functions to provide a mechanism to distribute stress within the top plate 16. The vertical transfer plate 20 further provides additional welding area to transfer stress from the top plate 16 to the backspan 22 then into the web of the joist.

[0033] In some embodiments, such as that shown in Figure 11 , the shoe 10 may comprise a stiffener plate 24 which functions to reinforce shoe extensions in higher load applications. The stiffener plate 24 is fastened to at least the front portion of the top plate 16 generally in the center and is perpendicular to the top plate 16 in orientation. The stiffener plate 24 is also fastened to the upstand 18 generally in the center and is perpendicular to the upstand 18 in orientation, such that the top of stiffener plate 24 is generally parallel with the top of the upstand 18. The stiffener plate 24 may have holes pre-drilled, which allows for the flow through of concrete, providing shear key action that further assists in composite action between the joist and the concrete slab. Further, the holes may be used to allow for the installation of reinforcing steel, which can be used to coordinate with other building requirements, including but not limited to diaphragm reinforcing.

[0034] In a preferred embodiment (shown in Figures 11 to 13d) of the rivetted shoe includes the addition of passive deck stops 26. The stops 26 have a variety of functions including protection of the rivets 28, improved anchorage into the concrete, as well as reinforcement of the vertical stiffener 24.

[0035] As described above, during the erection of joist framed floors, deck 4 must be fastened to the joists 6. Common methods of fastening the deck 4 to the joists 6 include, but are not limited to, self drilling screws, power actuated fasteners, and welding. At the end of the joists 6, in the vicinity of the joist shoe 10, if the deck covered the rivets 28 it is possible that the deck fasteners 30 (shown in Figure 12) could interfere with the rivets 28. This could lead to potential damage of the rivets 28 which could in turn reduce the overall strength of the shoe connection to the joist. The stops 26 create a physical block which prevents the decking from covering the rivets 28, thereby eliminating the possibility that the deck fasteners 30 can damage the rivets 28. In one embodiment, a widened shoe 10 is provided for support of the deck 4.

[0036] Furthermore, the stops 26 provide additional surface area for the concrete 8 to push against during loading of the floor. This has an additional benefit of allowing the shoe assembly to be thinner since the upright portion 18 of the shoe 10 doesn’t need to resist the full amount of slippage between the concrete and the joist. The thinner shoe, in turn, allows the deck to be installed more easily with a reduced step in thickness at the point where it terminates along the joist 6.

[0037] The stops 26 further improve the shoe assembly by reinforcing the stiffener 24. Under typical bending situations, the shoe is bent upwards (as previously depicted in Figure 3). This bending introduces compression into the top of the stiffener. When plates are compressed, they tend to buckle as also depicted in Figure 3. By strategically locating the stops 26 at critical locations, for example the point of buckling, buckling is resisted which in turn increases the strength of the stiffener plate and the overall shoe. As a corollary, a thinner stiffener may be used for the same load when using the stiffening effect of the stops 26.

[0038] The stops 26 may take various forms, as depicted in Figures 13 a to 13d. Stops may be aligned perpendicular or parallel to the joist length. Figure 13a shows the stops 26a as perpendicular to the length of the shoe. Figure 13b shows and embodiment in which the stop 26b includes as series of curves and angles. Stops may be plates or bent into change as shown in Figures 13c and 13d. Figure 13c shows two stops 26c which are parallel to the length of the shoe. The stop 26d of Figure 13d shows a U-shaped stop oriented parallel to the length of the shoe. It can be appreciated that these bends may be curved or angular. Further, stops may have holes in them in order to act as shear keys within the concrete. It should be noted that the figures show examples of stops only and other configurations are possible.

[0039] Preferably, the shoe 10 is constructed from the same metal as the joist, however the joist and shoe 10 can be made from different metals, as long as there is no galvanic corrosion between them.

[0040] Prior to installation of the shoe 10 on a joist, the shoe is prefabricated as described above. The pre-drilled or pre-punched holes in the shoe 10 are aligned with the holes in the joist and is mechanically fastened using rivets, bolts or any other suitable fastener known to a person skilled in the art. This is advantageous due to easier, faster, and more consistent implementation, particularly when fastening to galvanized steel.

[0041] Although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art. Theclaims appended hereto are to be given the broadest interpretation consistent with the specification as a whole and are not to be limited by the specific examples disclosed herein.

Claims

Claims1 . A joist shoe for a steel joist, comprising: a top plate, wherein: the top plate is planar with a rear portion fastenable to a top chord of the steel joist and a front portion extending past the end of the steel joist; an upstand, wherein: the upstand is fastened to an end of a top side of the front portion of the top plate and is substantially vertical; a backspan, wherein: the backspan is fastened to a bottom side of the top plate and extends downwardly and is fastened to a web on the steel joist; a front edge of the backspan is adjacent to the bottom side of the front portion of the top plate and tapers down to a bottom edge of the backspan such that the front edge and bottom edge of the backspan form a corner that would be substantially adjacent with the web of the steel joist; a vertical load transfer plate, wherein: the vertical load transfer plate is fastened to the bottom side of the front portion of the top plate and the tapered front edge of the backspan; and the vertical load transfer plate is fastened substantially perpendicular to the tapered front edge of the backspan.

2. The joist shoe of claim 1 further comprising at least one stop coupled to and extending upwardly from the top plate.

3. The joist shoe of claim 2, wherein the joist shoe further comprises a stiffener plate, wherein the stiffener plate is fastened substantially perpendicular to the top of the top plate and extends at least over the distance of the front portion of the top plate such that the stiffener plate extends to and is fastened substantially perpendicular to the upstand.

4. The joist shoe of claim 3 comprising a series of stops which are perpendicular to a length of the shoe.

5. The joist shoe of claim 3 wherein the stop is parallel to the length of the shoe.RECTIFIED SHEET ( RULE 91 .1 )6. The joist shoe of claim 4 wherein the stop comprises at least two upwardly extending stop members.

7. The joist shoe of claim 3 wherein the stop is comprised of a series of angled sections.

8. The joist shoe of claim 6 wherein the series of angled sections are joined together.

9. The joist shoe of claim 1 , wherein the top plate portion that extends past the end of the steel joist is wider than the top plate portion that is fastenable to the top chord of the steel joist.

10. The joist shoe of claim 1 , wherein the top plate contains at least one pre-drilled or pre-punched hole.11 . The joist shoe of claim 1 , wherein the upstand contains at least one pre-drilled or pre-punched hole.

12. The joist shoe of claim 1 , wherein the backspan contains at least one pre-drilled or pre-punched hole.

13. The joist shoe of claim 6, wherein the stiffener plate contains at least one pre-drilled or pre-punched hole.RECTIFIED SHEET ( RULE 91 .1 )

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