Abstract:
An anchor having multiple legs for a concrete wall. The anchor has an interface plate with two sides. Disposed on a first side is a stud that is connectable to a bracket. Disposed on the second side of the interface plate are at least two legs. Each of the legs is insertable and secured to a respective hole formed in the concrete wall with epoxy. Once the epoxy cures, the leg attaches the anchor to the concrete wall.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention generally relates to wall anchors for concrete walls and more particularly to a wall anchor with multiple legs that are attachable to a concrete wall using an adhesive.  
       BACKGROUND OF THE INVENTION  
       [0002]     Tilt-up building construction generally consists of concrete wall panels that are precast horizontally on the ground, cured, and then tilted up into place. The roof framing systems of these buildings generally consist of trusses, girders, beams, purlins, joists and stiffeners that can be incorporated into wall tie and diaphragm continuity systems.  
         [0003]     In areas subject to high seismicity, the connection between the walls of older tilt-up buildings and their timber roof framing system is generally inadequate per the currently established seismic design standards. Accordingly, seismic upgrading of such structures is occurring in older tilt-up buildings in order to mitigate these inadequacies. Such upgrades typically consist of the retrofit installation of wall tie systems having many individual components attached to the concrete wall panels and the roof framing systems.  
         [0004]     For example, a flare strut system, as explained in U.S. Pat. No. 6,493,998, can be used to transfer forces between a concrete wall panel and a roof diaphragm continuity element in a building&#39;s roof framing system as part of a seismic upgrade project. The flare strut system comprises a plurality of elongated strut elements that connect between the wall panel and a diaphragm continuity element. For the wall panel, an end connector assembly is attached to the wall. The end connector assembly is typically attached to the wall panel by drilling holes through the wall panel and passing a threaded bolt through an anchor plate located on the exterior side of the wall panel, the hole drilled through the wall panel, and the base plate of the end connector. A nut is then threaded onto the bolt from the interior of the building to secure the anchor plate, bolt and end connector to the building. The use of an exterior anchor plate may detract from the aesthetics of the building or may be very costly to install due to the removal and replacement work of the building&#39;s exterior finish. Furthermore, the installation of an end connector assembly with an exterior anchor plate may be impossible in certain situations (e.g., the presence of an adjacent building).  
         [0005]     Alternatively, the end connector assembly can be attached to a concrete wall using an epoxy anchor if the wall has sufficient thickness. Specifically, a 1 in. diameter threaded rod is installed in a corresponding hole drilled in the concrete wall panel. The threaded rod is secured to the wall panel with epoxy adhesive and the end connector assembly is attached to the threaded rod with a nut. With this type of installation, an exterior plate anchor is not needed.  
         [0006]     In order to provide the necessary strength for the flare strut system using an epoxy anchor, the threaded rod must be embedded into the concrete wall panel at least 5.75 inches, and typically 6.75 inches. Generally, these embedment depths will require that the thickness of the concrete wall panel be at least 7 to 8 inches thick. Because most concrete wall panels are typically 6 inches thick, the maximum anchor embedment depth is generally limited to 4.5 to 5 inches. Accordingly, because of the decreased anchor embedment depth, the capacity of an epoxy anchor is generally found to be insufficient.  
         [0007]     Another problem with epoxy anchors is that when large diameter epoxy anchors are installed in shallow embedments, it is possible the concrete will fail before the anchor, and thus precipitate a brittle failure mode Brittle failure modes are undesirable and should be avoided whenever possible. Brittle epoxy anchor failure modes are avoided by providing a sufficient anchor embedment depth so as to precipitate a ductile failure of the threaded rod element of an epoxy anchor before the concrete experiences brittle failure. However, as previously explained above, it may not be possible to provide a sufficient embedment depth for the epoxy anchor due to the thickness limitations associated with tilt-up concrete wall panels.  
       SUMMARY OF THE INVENTION  
       [0008]     In accordance with the present invention, there is provided an anchor having multiple legs for securing an end connector of a flare strut system, or other connection device, to a concrete wall. The anchor has an interface plate with a first side and a second side. Attached to the first side is a threaded stud which is receivable into the end connector and secured with a nut. Typically, the stud is perpendicular to and positioned in the center of the interface plate. The anchor further includes at least two legs attached on a second side of the interface plate opposite the first side. The legs are evenly spaced on the interface plate and project perpendicular to the second side of the interface plate. The legs are formed from threaded rod and engage threaded holes formed in the interface plate.  
         [0009]     A series of holes are drilled in the concrete wall in order to attach the anchor thereto. The holes are drilled in the same pattern as the legs are attached to the interface plate. In this respect, each hole corresponds to a respective one of the legs on the interface plate. Furthermore, the diameter of each hole is formed slightly larger than the outer diameter of each leg.  
         [0010]     In order to attach the anchor to the concrete wall, epoxy is injected into each hole. Then, the legs are inserted into corresponding holes formed in the concrete wall. Once the epoxy has cured, then the anchor is securely attached to the wall and the end connector of the flare strut system can be attached to the stud.  
     
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0011]     These, as well as other features of the present invention, will become more apparent upon reference to the drawings wherein:  
         [0012]      FIG. 1  is a cross-sectional view of an installed wall anchor with flare strut;  
         [0013]      FIG. 2  is an elevational view of the wall anchor;  
         [0014]      FIG. 3  is a cross-sectional view of the wall anchor;  
         [0015]      FIG. 4  is a plan view of the wall anchor; and  
         [0016]      FIG. 5  is a cross-sectional view of the wall anchor with a threaded center stud hole. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]     Referring now to the drawings wherein the showings are for purposes of illustrating a preferred embodiment of the present invention only, and not for purposes of limiting the same,  FIG. 1  illustrates an installed wall anchor  10  attaching a flare strut system  12  to a concrete wall panel  14 . The flare strut system  12  has a strut element  16 , an interface plate  18 , a pipe element  20 , and a coupler element  22 . The details of the flare strut system  12  can be found in Applicant&#39;s issued U.S. patent entitled “Flare Strut System” (U.S. Pat. No. 6,493,998), the contents of which are incorporated herein by reference. Typically, the coupler element  22  attaches to an end connector  24  through the use of a connection bolt or pin  26 . The end connector  24  has a base plate  28  and two connection plates  30  welded thereto. The two connection plates  30  are welded perpendicular to the base plate  28  and parallel to each other such that each connection plate  30  has a matching hole  32  formed therein for receiving the connection bolt  26 . In this respect, the two connection plates  30  are welded to the base plate  28  such that the holes  32  formed in each connection plate  30  are linearly aligned to accept the connection bolt  26 .  
         [0018]     The base plate  28  further includes a hole  34  for insertion of a threaded stud  36  from the wall anchor  10  and is secured to the wall anchor  10  with a nut  38  threaded onto the stud  36 . Specifically, the stud  36  protrudes through the hole  34  such that the nut  28  can be threadably engaged onto the stud  36 . In this respect, the nut  28  is tightened on the threaded stud  36  to abut the base plate  28  in order to attach the end connector  24  the wall anchor  10 .  
         [0019]     The wall anchor  10  secures the end connector  24  and hence the flare strut system  12  to the concrete wall  14 . Referring to  FIGS. 2 through 4 , the stud  36  is attached to an interface plate  40 . The interface plate  40  is typically a rectangular section of 3/4 inch thick steel. The size, thickness, and configuration of the interface plate  40  can vary depending upon the application. In the preferred embodiment, the shape of the interface plate  40  is an 8 inch by 8 inch square. It is also possible for the interface plate  40  to be octagonal, circular, hexagonal, etc. . . .  
         [0020]     The threaded stud  36  is plug welded at the center of one side of the interface plate  40 . In this respect, an aperture  46  is formed in the center of the interface plate  40  and the stud  36  is inserted into the aperture  46  and welded to the plate  40 . In the preferred embodiment, the stud  36  is a 1 inch diameter×2.5 inch long threaded rod made from steel.  
         [0021]     Alternatively, the threaded stud  36  can be inserted into a threaded aperture  46  of the interface plate  40 . Referring to  FIG. 5 , a cross-sectional view of the interface plate  40  is shown. The aperture  46  has threads  48  matching the threads of the stud  36 . In this regard, the stud  36  is threadably engaged to the interface plate  40 . The threads  48  of the aperture  46  can be formed in such a manner so as to prevent the stud  36  from being further turned after the stud  36  has been fully inserted (i.e., seated) in the threaded aperture  46  when the nut  38  is being tightened. It will be recognized by those of ordinary skill in the art, that by threadably engaging the stud  36  to the interface plate  40 , it is possible to remove and exchange the stud  36  easily when needed. This may be advantageous during installation when a different length of stud  36  is needed.  
         [0022]     In order to attach the interface plate  40  to the concrete wall  14 , the wall anchor  10  has four legs  42   a ,  42   b ,  42   c  and  42   d  extending from a side of the interface plate  40  opposite the stud  36 . In the preferred embodiment of the present invention, each of the legs is formed from 1/2 inch diameter threaded zinc-plated rod. In order to attach the legs  42  to the interface plate  40 , four threaded holes  44   a ,  44   b ,  44   c , and  44   d  are formed therein. Each of the threaded holes  44  is formed by drilling and tapping the interface plate  40  to a size to receive a respective one of the legs  42 . In this respect, leg  42   a  is threadably attached to hole  44   a , leg  42   b  is insertable into threaded hole  44   b , etc. . . . The layout of the threaded holes  44  on the interface plate  40  is configured to equally spread the load between all four legs  42 . The number and location of the legs  42  can vary depending upon the application and is chosen to balance the loading between the legs  42  and provide maximum anchor capacity while minimizing the structural requirements (i.e., thickness) of the interface plate  40 . It will be recognized that by having more than one leg  42 , the diameter of each leg  42  can be reduced thereby reducing the embedment depth of the leg  42  into the concrete wall  14 . Therefore, the use of multiple legs  42  reduces the chances of brittle mode failure of the concrete wall  14 .  
         [0023]     Rods threaded into the interface plate  40  are used as the legs  42   a  in order to not interfere with the base plate  28  of the end connector  24 . It is possible that the base plate  28  would be positioned over the legs  42  when the end connector  24  is attached to the wall anchor  10 . Accordingly, nuts could not be used to secure the legs  42  to the interface plate  40  because the nuts would interfere with the base plate  28 . It will be recognized that other types of attachment means for the legs  42  are possible such as welding the legs  42  so long as the attachment means does not interfere with the base plate  28 . In the preferred embodiment of the invention, the threaded holes  44  are spaced to form a 4 inch by 4 inch square. The threaded rod forming the legs  42  can be cut to the desired length. In the preferred embodiment, the legs  42  are about 5.25 inches long so that after they are threaded into the interface plate  40 , about 4.5 inches can be embedded within the concrete wall  14 .  
         [0024]     Referring back to  FIG. 1 , the wall anchor  10  is attached to the concrete wall  14  with the legs  42 . In order to accept the legs  42 , holes are formed in the concrete wall in a pattern that matches the pattern of the threaded holes  44  of the interface plate  40 . Each hole formed in the concrete wall panel  14  is configured to receive a respective one of the legs  42 . The diameter of the holes formed in the concrete panel  14  are slightly larger than the diameter of the threaded rod forming the leg  42 . Typically, the diameter of the holes are formed about 1/16 inch to 1/8 inch larger than the diameter of the legs  42 . Before the legs  42  are inserted into the holes formed in the concrete panel  14 , an epoxy adhesive is injected into each hole. The gap between the leg  42  and the hole allows the epoxy to distribute around the threaded rod. The type of epoxy being used determines how much bigger the diameter of the holes formed in the concrete wall  14  should be. The threads on the legs  42  aid in the mechanical bond of the epoxy to the legs  42 .  
         [0025]     After the epoxy has been injected into the holes, the wall anchor  10  is pushed up against the concrete wall panel  14  such that the interface plate  40  abuts the concrete wall panel  14  as shown in  FIG. 1 . Once the epoxy has cured, the wall anchor  10  is secured to the concrete wall panel  14 . The end connector  24  of the flare strut system  12  can be secured to the stud  36 . In the preferred embodiment of the present invention, the capacity of the four legs  42  when bonded with the epoxy adhesives currently available is generally sufficient for most all flare strut system installations.  
         [0026]     Additional modifications and improvements of the present invention may also be apparent to those of ordinary skill in the art. For example, the wall anchor  10  may be adapted to attach other types of brackets to the concrete wall panel. Thus, the particular combination of parts described and illustrated herein is intended to represent only certain embodiments of the present invention, and is not intended to serve as limitations of alternative devices within the spirit and scope of the invention.