Abstract:
A connection node for a double layer grid or truss system has at least one diagonal flange receiving a pair of diagonal framing members having surfaces that lie in a single diagonal plane parallel to the flange(s). Use of co-planar diagonal members that can be at various diagonal angles or vertical, simplifies node connections and permits variations in bay spacing to produce interesting architectural effects and to provide greater member density where structural loads are greater.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to connections designed for joining linear, structural elements that comprise double-layer-grids, three-dimensional trussed structures and braced planar truss systems. The most common application of such connections is in double-layer-grids. Therefore, the connection hereof is named after the acronym for double-layer-grid—the DLG Connector (DLGC).  
         [0003]     2. Background Art  
         [0004]     Current connections designed for double-layer-grids receive linear, structural elements that are either round or square in cross-section.  FIG. 1  illustrates a conventional connector for square cross-section framing members. Note that the adjacent diagonal members at the connection reside in different planes.  
         [0005]     Bolted connections are easily effected using these systems that accommodate square linear, structural elements. The use of a square cross-section for the framing is advantageous since the fabrication of the framing member consists simply of drilling or punching holes at both ends after the member is cut to length. Ball-node systems are designed for the use of round cross-sections (pipes) in double-layer-grids and involve a more expensive design and fabrication process.  
         [0006]     A double-layer-grid is understood to be a structure with a horizontal, square grid of framing elements that serves as the top chords and is the top “layer.” Similarly, there are the bottom chords with the same square grid that is offset horizontally by one-half the bay width in both directions. This bottom “layer” is also offset downwardly from the top “layer” by a set distance and is held in position by the use of diagonal framing elements.  FIGS. 2, 3  &amp;  4  show a typical double-layer-grid six bays long by five bays wide. There are several disadvantages of the connection systems of the prior art when applied to double-layer-grids as described with square cross-section framing elements. First, these systems are restricted to square, double-layer-grids only. Second, these systems can only produce flat double-layer-grids. Third, contoured (free-form) footprints are difficult to design and construct. Fourth, vertical sidewall and/or end wall framing is difficult to design and construct. These disadvantages are resolved with the DLCG design.  
       SUMMARY OF THE INVENTION  
       [0007]     The DLGC takes advantage of natural planes formed by the double-layer grid. When studying a double-layer-grid the observer will see in  FIG. 4  that the diagonal members in each half-bay all lie in the same plane. As long as the diagonal framing elements have flat surfaces, such as square/rectangular tubes, angles, channels and I-beams (wide flanged sections as in steel construction), these framing elements can be rotated to be parallel to the diagonal plane. Once the member rotation is oriented so that the flat surface(s) are in plane with the diagonals, the problem of attachment is immensely simplified. In current systems as shown in  FIGS. 1, 5 ,  6  and  7 , opposing diagonal elements have their major axis residing in the vertical plane. The DLGC system makes adjacent diagonal elements have their surface features co-planar. When these surface features are oriented in the same plane, they become parallel to the plane defined by the row of diagonal elements. Once this is accomplished, adjacent diagonals can be connected to the joint by the same structural plates. Sharing structural plates at the connection as seen in  FIGS. 8, 9  and  10  creates the simplified connection. The members comprising the horizontal grid attaching to the diagonal elements can also be connected together with plates following the direction of the diagonal plane. This allows for a system of plate flanges with parallel centerlines that is ideal for fabrication as aluminum extrusions or welded steel plates that comprise the joint (see  FIGS. 11, 12  and  13 ). Current systems cannot do this but must provide separate out-of-plane connection flanges for diagonal elements.  
         [0008]     The DLGC can be made of any structural material such as, but not limited to, aluminum, steel, fiber-reinforced polymers (FRP) and plastics. Fabrication of the DLGC can use any process suitable to the material used such as extruding or casting aluminum and welding steel plates. Linear members connected by the DLGC can be made of any structural material such as, but not limited to, aluminum, steel, FRP, plastic or wood.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The aforementioned objects and advantages of the present invention, as well as additional objects and advantages thereof, will be more fully understood herein after as a result of a detailed description of a preferred embodiment when taken in conjunction with the following drawings in which:  
         [0010]      FIG. 1  is a photograph of a prior art node connection using convectional connection technology where the diagonal members lie in different planes in order to maintain their respective vertical orientations;  
         [0011]      FIGS. 2, 3  and  4  illustrate isometric, plan and side views, respectively, of a double layer grid that is six bays long and five bays wide;  
         [0012]      FIGS. 5, 6  and  7  illustrate isometric, bottom and plan views, respectively, of a conventional node connection in a double layer grid;  
         [0013]      FIGS. 8, 9  and  10  illustrate isometric, bottom and plan views, respectively, of a node connection of a double layer grid according to a conceptual embodiment of the present invention;  
         [0014]      FIGS. 11, 12  and  13  illustrate isometric, bottom and plan views, respectively, of a first embodiment of a DLGC node connection of the invention;  
         [0015]      FIGS. 14, 15  and  16  illustrate isometric, bottom and plan views, respectively, of a wide-flange aluminum member version of the invention;  
         [0016]      FIGS. 17, 18  and  19  illustrate isometric, bottom and plan views, respectively, of a back-to-back angle member version of the invention;  
         [0017]      FIG. 20  is an illustration of a connection of the invention which incorporates a mullion/rafter system for glazing with glass, polycarbonate or acrylic sheets;  
         [0018]      FIG. 21  is an isometric view of the connector of  FIG. 20  with a glass sheet shown on one side only;  
         [0019]      FIGS. 22 and 23  show side and isometric views, respectively, of a DLG in arch or vaulted shape;  
         [0020]      FIGS. 24, 25  and  26  illustrate isometric, plan and bottom views, respectively, of an extruded aluminum node of a vaulted DLG; and  
         [0021]      FIGS. 27, 28 ,  29  and  30  illustrate isometric, top, side and end views, respectively, of a DLG with variable bay spacing in one direction.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]      FIGS. 5 through 7  illustrate the existing convention for member orientation in double-layer-grids. A wide-flanged member was chosen for these examples to help visualize member orientation. As seen in  FIG. 5 , the diagonal member in the foreground has the web oriented vertically as do the others.  FIG. 6  shows a joint along the bottom chord in plan view. The intersections of the diagonals trace a cruciform which indicates that the flat surfaces of the diagonals are in separate planes.  FIG. 7  is a close-up of a joint from  FIG. 4 . This illustrates that the flanges of the members are not parallel to the plane defined by the row of diagonals in each half-bay.  
         [0023]     The DLGC joint layout shown in  FIG. 8  reveals that the webs of the present invention are not in a vertical orientation.  FIG. 9  demonstrates that opposite pairs of diagonals have a member orientation that makes them co-planar as evidenced by a straight line at the intersection—two intersecting planes make a straight line.  FIG. 10  verifies that the flanges of the members are oriented so that they are now parallel to the diagonal plane. This way of orienting diagonal elements makes the DLGC possible. Joint designs based on this innovation are presented next.  
         [0024]     Shown in  FIGS. 11 through 13  is one embodiment of the DLGC. This connection is designed to be extruded aluminum for the joining of aluminum members and, in this example, square aluminum tubes.  FIGS. 14 through 16  show the connector with wide-flange aluminum shapes.  FIGS. 17 through 19  illustrate a similar connection with back-to-back angles. Similar constructions can be produced in steel with the DLGC consisting of welded steel plates instead of an extrusion. The DLGC also provides for using engineered wood and sawn lumber.  FIG. 20  illustrates that the DLGC can incorporate a mullion/rafter system for glazing with glass, polycarbonate or acrylic.  FIG. 20  is an isometric view with glass shown only on one side for clarity. Additionally, similar attachments can be integrated with the DLGC system that would allow for the batten engagement of sheet metal panels. In all these cases, the cladding engagement mechanism can be produced integrally with the rafters of the top chord in one or both directions. Once the cladding engagement mechanism is made integrally with the rafter, no secondary framing is required to support the cladding. The top chord members can serve as mullions.  
         [0025]      FIGS. 22 through 23  show a double layer grid that is shaped as an arch or vault.  FIG. 22  shows the end view which demonstrates that the diagonal planes are straight and uninterrupted which allows for the use of the DLGC in that direction. Note that the DLGC works easily in a direction at right angles to the direction of curvature for a vault.  FIGS. 24 through 26  show an extruded DLGC aluminum joint used to create the shape of the vault. The joint is designed to create curvature by orienting the horizontal tabs and diagonals at the needed angle—off from the 180 plane used in a flat double-layer-grid. Again, such a joint could be produced with welded steel plates or pultruded FRP. The same joint design can be used throughout the structure with no change to the DLGC profile or bolt patterns.  
         [0026]      FIGS. 27 through 30  show a double-layer-grid with variable bay spacing in the longitudinal direction.  FIG. 30  shows the end view which demonstrates that the diagonal planes are straight and uninterrupted which allows for the use of the DLGC in that direction. However, the bays running at 90 degrees from this view as shown in  FIG. 29  can be set at any regular or irregular spacing. As seen in  FIG. 28 , the grid forms rectangles with the long sides in the longitundinal direction starting from either end. The bay spacing progressively changes going towards the center until the long direction of the rectangles follow the transverse direction. This does not effect any change in the end view, the diagonals all lie in the same plane. Again, the DLGC would be oriented in this direction without change in profile. However, the drilled bolt patterns in the diagonal flanges of the connector would require adjustment in the bolt pattern orientation and the member lengths would change. The last set of diagonals at each end are brought up vertically to form end walls as seen in  FIG. 29 .  
         [0027]     A significant advantage to this feature is that double-layer-grids are no longer forced into square bay spacing which creates modular inflexibility in the structure. This allows the width and length of the double-layer-grid to be independent resulting in infinitely adjustable lengths versus widths. Also, as seen in  FIG. 28 , interesting architectural effects can be achieved by varying the bay spacing in the one direction. From a structural engineering point of view, this is an easy way to increase the member density in high stress areas of the frame. A variation of this is a tapered 3-sided tower.  
         [0028]     Having thus disclosed various preferred embodiments of the present invention, it will now be apparent that many additional node configurations and grid and truss system configurations can be achieved by virtue of the advantageous teaching provided herein. Accordingly, the scope hereof will be limited only by the appended claims and their equivalents.