Patent Publication Number: US-9834945-B2

Title: Concrete form tie assembly for monolithic slabs bearing on masonry stem walls

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Pursuant to 35 U.S.C. §119(e), this application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/010,326, filed on Jun. 10, 2014, the entire contents of which are incorporated herein by this reference. 
    
    
     BACKGROUND 
     (1) Technical Field 
     This invention relates generally to concrete form brackets, and more particularly to tie assemblies for the forms of monolithic concrete floor slabs bearing on masonry stem walls. 
     (2) Background 
     A common residential construction method involves the construction of a monolithic concrete floor slab that is supported by, and bears upon, masonry stem walls. The stem walls are made of masonry units, such as concrete blocks having two voids in them. In past construction methods, bracket members were inadequate to place the concrete forms in a substantially co-planar orientation with respect to the exterior face of the stem walls. Thus, the bearing area of the floor slab did not extend across the entire top surface of the stem walls. This configuration can cause instability or a weakened interface between the stem wall, floor slab, and even the structural wall bearing on the floor slab. 
     Another prior construction technique called for notched header blocks, where the notch was sized to receive the monolithic floor slab. This notching is an extra construction step and adds complexity to the construction process. The notched header blocks are non-standard, and they must be aligned properly to accommodate construction of the stem wall and floor slab interface. These extra steps are time consuming, and the extra materials can be expensive. 
     The present tie assembly promotes efficient construction of the monolithic slab and the use of standard masonry blocks by providing a structure to hold and retain concrete form members in place without requiring non-standard notching or other alternation of the header blocks or masonry stem walls. 
     SUMMARY OF THE PREFERRED EMBODIMENTS 
     The tie assembly disclosed herein is used to brace the forms used during construction of monolithic cast-in-place concrete floor slabs bearing on one or more masonry stem walls. Generally, the tie assembly comprises a retaining member, an extension member, and a slotted tab member. One embodiment of the retaining member comprises a shank connected to a bend. The retaining member is connected to the tab member by the extension member. The tab member is attached to the extension member at or near the end of the extension member opposite the end near which the retaining member is attached. The tab member comprises a slot configured to receive and removably retain a wedge stake, which braces the form member. The interface between the extension member and the tab member comprises a release mechanism for disconnecting the tab member from the extension member. 
     In use, the bend of the retaining member is placed under the header block, and the extension member extends across the top of the header block such that the tab member is cantilevered past the exterior face of the stem wall. The form member is seated on the cantilevered tab member. The wedge stake is then inserted into the slot, and the wedging action causes the wedge stake to firmly brace the form member against the lateral forces caused by the wet concrete of the floor slab. 
     A mechanical fastener is then driven through the wedge stake and through the form member to protrude from the interior face of the form member. Reinforcing members are connected to the protruding ends of the mechanical fasteners, and they act as the edge reinforcing of the floor slab. 
     After the concrete is cured, the mechanical fasteners are removed, the wedge stakes are removed, and the form members are stripped from the floor slab. The tabs are removed by striking the tabs with an impact force, which causes the tie assembly to fracture at the release mechanism. 
     Another embodiment of the retaining member further comprises a lip connected to the bend at a location distal from the connection point of the shank, such that the gap between the shank and the lip forms a throat. The throat is sized such that an outside wall of the header block is snugly seated in the throat. In this configuration, the lip provides a greater anchoring force against pullout or uplift caused by the forces acting on the tie assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross section of a typical interface between a masonry stem wall and a monolithic slab, showing placement of an embodiment of the tie assembly having tab with a single slot. 
         FIG. 2  is a cross section of a typical interface between a masonry stem wall and a monolithic slab, showing a form spacer and showing the placement of an embodiment of the tie assembly having tab with two slots. 
         FIG. 3  is an isometric view of a section of a stem wall, showing the tie assembly installed. 
         FIG. 4  is an isometric view of a section of a stem wall, showing the wedge stake installed into the tab member of the tie assembly. 
         FIG. 5  is a top view of one embodiment of the tab member, extension member, and retaining member stamped out of a flat sheet of metal before being bent into proper form for installation. 
         FIG. 6  is a flat view of one embodiment of the tab member, extension member, and retaining member bent into proper form for installation. 
         FIG. 7  is a rear view of one embodiment of the tab member, extension member, and retaining member bent into proper form for installation. 
         FIG. 8  is a side view of one embodiment of the wedge stake. 
         FIG. 9  is a partial cross section view of the stem wall interface with the monolithic slab, where the tie assembly comprises a reinforcement holder. 
         FIG. 10  is a cross section view of one embodiment of a reinforcement holder. 
         FIG. 11  is a side view of one embodiment of a reinforcement holder. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the drawings, the tie assembly will now be described with regard for the best mode and the preferred embodiments. In general, the tie assembly disclosed herein is a retaining tie assembly intended for connecting masonry stem walls to the forms for cast-in-place concrete floor slabs. The embodiments disclosed herein are meant for illustration and not limitation of the invention. An ordinary practitioner will appreciate that it is possible to create variations of the following embodiments without undue experimentation. 
     Referring to  FIGS. 1-4 , the tie assembly  1  disclosed herein is used during construction of cast-in-place concrete monolithic floor slabs  50  bearing on one or more masonry stem walls  5 . In one embodiment, the tie assembly  1  connects to one or more header blocks  6  on the stem wall  5 , and the tie assembly  1  is configured to retain a form member  24  in place during the pour and curing period of the cast-in-place concrete. 
     Generally, the tie assembly  1  comprises a retaining member  10 , an extension member  20 , and a slotted tab  21 . Referring to  FIGS. 5-8 , the retaining member  10  is any hook, bend, or other anchor member for retaining the tie assembly  1  in place and securely anchored to the stem wall  5 . One embodiment of the retaining member  10  comprises a shank  11  connected to a bend  12 . In one embodiment of the bend  12 , the bend  12  further comprises an aperture  18  that allows grout or mortar to pass through the bend  12 . Once cured, this grout or mortar provides additional resistance force to pullout of the retaining member  10 . The extension member  20  is an elongate member having a first end and a second end. The extension member  20  is sized to span between the retaining member  10  and the tab  21 , thus providing structural support between the retaining member  10  and the tab  21 . The retaining member  10  is attached to the first end of the extension member  20 . The tab  21  is attached to the second end of the extension member  20  via the release mechanism  25 , as described below. The tab  21  further comprises one or more slots  22  configured to receive and removably retain a wedge stake  23  that braces the form member  24 . The wedge stake  23  has a lower portion  16  in the form of a wedge, and an upper portion  17  configured to abut against and retain the concrete form member  24 . 
     Referring again to  FIGS. 1-4 , the bend  12  of the retaining member  10  is placed under the header block  6  or otherwise attached to the stem wall  5 , and the shank  11  is oriented vertically and parallel to the side of the header block  6 . The extension member  20  extends across the top of the header block  6  such that the tab  21  is cantilevered past the exterior face  7  of the stem wall  5 . The form member  24  is typically a timber plank having a cross section measuring two inches by twelve inches, or some other similar member. In one embodiment, the form member  24  is seated on the cantilevered tab  21 . The lower portion  16  of the wedge stake  23  is then inserted into the slot  22 , and the wedging action causes the upper portion  17  of the wedge stake  23  to firmly brace the form member  24  against the lateral forces caused by the wet concrete of the floor slab  50  that press hydrostatically against the form member  24 . The position of the form member  24  is adjusted such that the interior face  26  of the form member  24  is substantially co-planar with the exterior face  7  of the stem wall  5 . The interior face  26  of the form member  24  may even overlap with and abut against the exterior face  7  of the stem wall  5 . In another embodiment, shown in  FIG. 4 , the form member  24  comprises one or more form slots  29  configured to receive the tab  21  and release mechanism  24  such that at least one slot  22  in the tab  21  protrudes past the outer face of the form member  24  to a sufficient distance to receive the wedge stake  23 . In this embodiment, it is the form slot  29 , rather than the bottom of the form member  24 , that is seated on the extension member  20 , on the tab  21 , or on both. The bottom of the form member  24  extends below the tab  21  along the exterior face  7  of the stem wall  5 . 
     The lateral force of the form member  24  is resisted by the wedge stake  23 . This lateral force is caused by the hydrostatic pressure of the wet cast-in-place concrete of the floor slab  50 . As a result, an axial force is developed in the tab  21 , and that axial force is transferred across the release mechanism  25 , into the extension member  20 , and ultimately resisted by the retaining member  10 . 
     In one embodiment of the tie assembly  1 , shown in  FIG. 2 , the tie assembly  1  is configured for use with a concrete form spacer  45 . The form spacer  45  is used in application where it is desirable for the slab  50  to overhang the exterior face  7  of the stem wall  5 , such as at the interface between a house and a wooden deck. To accommodate the form spacer  45 , the tab  21  has a second slot  22  for receiving a wedge stake  23 . In this embodiment of the tab  21 , shown in  FIG. 5 , the first slot  22   a  is disposed in the tab  21  at a location closer to the release mechanism  25  than the location of the second slot  22   b . Once the tie assembly  1 , the form spacer  45  and the form member  24  are placed at the top of the stem wall  5  as desired, the wedge stake  24  is inserted into the second slot  22   b  to retain the form member  24  in fixed relation to the form spacer  45  and the stem wall  5 . 
     In one embodiment, shown in  FIG. 9 , the wedge stake  23  has a planar, wedge-like lower portion  16  and an upper portion  17  having a flange  38  and a web  39 . The flange  38  is placed flat against the outside surface of the form member  24 , and the web  39  resists the bending force caused by the lateral force of the form member  24 . A mechanical fastener  27  is inserted through the flange  38  and through the form member  24  so that the tip  40  of the mechanical fastener  27  protrudes from the interior face  26  of the form member  24 . The mechanical fastener  27  is a smooth shank duplex nail, a screw, or other similar member. Reinforcing members  28 , such as reinforcing steel or carbon fiber bars, are connected to the protruding ends of the mechanical fasteners  27 . In other embodiments, reinforcing members  28  could also be wire mesh or other types of structural reinforcement capable of reinforcing cast-in-place concrete against tension cracking. In most instances, the reinforcing members  28  will act as the edge reinforcing of the floor slab  50 . 
     After the tie assembly  1  is placed, the form members  24  are secured, and the reinforcing members  28  are installed. The wet concrete is then poured, typically in a monolithic pour, to form the floor slab  50 . After the concrete is cured, the mechanical fasteners  27  are removed, and the wedge stakes  23  are removed by pulling them upward and out of the respective slots  22  in the tabs  21 . The form members  24  are then stripped from the floor slab  50 . The fascia of the floor slab  50  is substantially co-planar with the exterior face  7  of the stem wall  5 . The tabs  21  remain protruding from the exterior face  7  of the stem wall  5 , while the extension member  20  remains firmly encased between the concrete of the floor slab  50  and the top of the stem wall  5 . 
     The tabs  21  are removed by one of several different methods. In one embodiment, the tabs  21  are removed by striking the tabs  21  with an impact force, which causes the tie assembly  1  to fracture at the release mechanism  25 . This could be accomplished by striking the tabs  21  with a hammer or other impact tool. In this embodiment, the release mechanism  25  comprises a fracture zone area adapted to aid removal of the tab  21  from the extension member  20 . For example, as shown in  FIG. 5 , one embodiment of the fracture zone area of the release mechanism  25  comprises one or more structural features to weaken the interface between the tab  21  and the extension member  20 , such structural features including one or more of a neck, perforation, crease, slot, or other feature. In another embodiment, the release mechanism  25  could be a region between the tab  21  and the extension member  20  that is cut with a metal cutting tool, such as a bolt cutter, saw, or the like. In another embodiment, the release mechanism  25  is a hinge between the extension member  20  and the tab  21 , and the release mechanism  25  is disengaged by removing the hinge pin from the hinge. 
     Referring again to  FIG. 1 , another embodiment of the retaining member  10  further comprises a lip  14  connected to the bend  12  at a location distal from the connection point of the shank  11 , such that the gap between the shank  11  and the lip  14  forms a throat  15 . This throat  15  is sized to snugly receive a wall of the header block  6 , depending on the type of header block. In many applications, the header block  6  is a concrete masonry unit, such as a concrete block or cinder block, with one or more hollowed areas or cores, many of which are available in standard sizes. The throat  15  is sized such that an outside wall of one of these header blocks  6  is snugly seated in the throat  15 . In this configuration, the lip  14  provides a greater anchoring force against pullout or uplift caused by the forces acting on the tie assembly  1 , as described above. 
     Tie assemblies  1  are spaced along the length of the stem wall  5  as needed for the particular application. Typically, the tie assemblies  1  are spaced at intervals of a few feet on center. For ease of fabrication the lip  14 , bend  12 , shank  11 , extension member  20  and tab  21  can be stamped out of a sheet or plate of metal. For example, the foregoing components can be stamped out of a sheet of metal having a thickness of 1/16 of an inch, ⅛ of an inch, or the like. The resulting metal strip is then cold formed by bending the strip at certain locations to form the foregoing components of the tie assembly  1 . These components also could be made from plastic strips of appropriate dimensions. 
     In another embodiment, referring to  FIGS. 9-11 , the tie assembly  1  further comprises a reinforcement holder  30  configured to attach to the mechanical fastener  27  in a manner that supports the reinforcing member  28 . The reinforcement holder  30  is an optional member placed over the mechanical fasteners  27  prior to placement of the reinforcing members  28 . The reinforcement holder  30  comprises a shaft  31  for receiving the mechanical fastener  27 , and a clip member  32  for connecting to the reinforcing member  28 . In one embodiment, the shaft  31  comprises a hollow recess  33  for receiving the mechanical fastener  27 , where the hollow recess  33  has a portion with a first diameter  33   a  and a portion with a second diameter  33   b . In one embodiment, the first diameter  33   a  is larger than that of the diameter of the mechanical fastener  27 , and the second diameter  33   b  is slightly smaller than the diameter of the mechanical fastener  27 . The reinforcement holder  30  is placed over the mechanical fastener  27  such that the recess  33  receives the tip  40  of the mechanical fastener  27 . The mechanical fastener  27  passes through the recess  33  portion with the first diameter  33   a  with relative ease since there is no appreciable friction between the reinforcement holder  30  and the mechanical fastener  27 . The tip  40  of the mechanical fastener  27  is then inserted into the recess  33  portion having the second diameter  33   b , forming a snug fit between the reinforcement holder  30  and the mechanical fastener  27 . 
     The reinforcement holder  30  is pressed over the mechanical fastener  27  until the mouth of the recess  33  contacts the form member  24 , as shown in  FIG. 9 . In one embodiment, the shaft  31  is sized such that when the reinforcement holder  30  is in contact with the form member  24 , the clip member  32  retains the reinforcing member  28  at a predetermined distance from the form member  24  such that the floor slab  50  will have an adequate cover over the reinforcing member  28 . In this embodiment, the reinforcing member  28  is the edge reinforcing of the floor slab  50 , and the cover distance is typically about one and one half to about two inches, although other cover distances could be used as well. In this embodiment, the reinforcement holder  30  functions to greatly increase the speed and ease of construction. The reinforcement holder  30  is quickly and easily placed over the mechanical fastener  27  and pressed until contact with the form member  24  occurs. The reinforcing member  28  is then placed in the clip member  32 , and no other steps are needed to place the edge reinforcing at a proper distance from the form member  24 . Since the length of the shaft  31  is pre-measured, the installing personnel does not have to spend time measuring the distance between the reinforcing member  28  and the form member  24  to ensure adequate cover distances. 
     In one embodiment, the clip member  32  comprises one or more retaining arms  34  defining a cradle  35  for seating the reinforcing member  28 . In one embodiment, retaining arms  34  are flexible, curved members such that the ends of the retaining arms  34  define a neck  37  above the cradle  35 . The ends of the retaining arms  34  comprise outwardly protruding lips  36  for receiving the reinforcing member  28 . The reinforcing member  28  has a diameter greater than the width of the neck  37 . As the reinforcing member  28  is forced toward the cradle  35 , the reinforcing member  28  abuts the lips  36 , thus forcing the retaining arms  34  to flex in an outward direction, thereby widening the neck  37 . When the widest part of the reinforcing member  34  passes the neck  37 , the reinforcing member  28  snaps into the cradle  35 , the retaining arms  34  return to their original unflexed position, and the reinforcing member  28  is snugly seated in the cradle  35  and retained by the retaining arms  34 . 
     The foregoing embodiments are merely representative of the tie assembly and not meant for limitation of the invention. For example, persons skilled in the art would appreciate that there are several embodiments and configurations of the tie assembly components, and other components will not substantially alter the nature of the system. Likewise, elements and features of the disclosed embodiments could be substituted or interchanged with elements and features of other embodiments, as will be appreciated by an ordinary practitioner. Consequently, it is understood that equivalents and substitutions for certain elements and components set forth above are part of the invention described herein, and the true scope of the invention is set forth in the claims below.