Abstract:
A support element for use with shotcreting to line tunnel walls with cement includes four rods secured to outer surface portions of quadrilateral reinforcement members. The longitudinal axis of pairs of adjacent rods each lie in a plane such that adjacent planes are normal to one another. Optionally, side braces may be secured to an outer surface or to an inner surface of adjacent rods.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims the benefit of Provisional Application Serial No. 60/354,541 filed Feb. 5, 2002, in the name of James E. Marianski for “Box Lattice”. Provisional Application Serial No. 60/354,541 is hereby incorporated by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a support girder or support element used to help resist underground construction loads during tunneling and, more particularly, to a box lattice support element having four rods secured in a predetermined relationship to one another by quadrilateral reinforcement members and, optionally, including side braces.  
           [0004]    2. Brief Description of the Prior Art  
           [0005]    In the New Austrian Tunneling Method (NATM), lattice girders or lattice support elements serve some of the basic functions as steel arch supports. More particularly, after the preparatory work is completed, the support elements are built in to support the roof and/or walls of the tunnel. The support elements, in general, include a plurality of spaced elongated metal rods held in spaced relationship, usually by welding or wiring the rods to stiffening members or spiders. For extended lengths of support elements, the ends of the support elements are secured together by flanges provided at the ends of the support elements and securing them together, e.g., by a nut and bolt assembly, to form a lattice grid. Cement is applied to the walls of the tunnel through the support elements and to the support elements by a technique known in the art as shotcreting.  
           [0006]    The support elements provide a more efficient bond with the shotcrete strength because they essentially have no shaded areas. More particularly, the shotcrete passes through the support elements readily reducing the possibility of unconsolidated shotcrete areas behind the support element which provides for a more even and essentially void-free concrete layer. Examples of prior art support elements are disclosed in U.S. Pat. Nos. 4,335,556 to Arnold and 5,054,964 to Salzmann et al.  
           [0007]    The Arnold patent, in general, discloses a support element having three or more exterior rods arranged in a polygon cross section and connected to one another by stiffening elements. Each stiffening element includes a number of cross struts bent in their centers and inclined with respect to the rods. The Salzmann patent, in general, discloses a support element having three exterior rods arranged in a triangular cross section. Each of the three rods is connected by a triangularly-shaped stiffening element, with each of the three rods connected to a corresponding corner of the triangularly-shaped stiffening element. A limitation of the presently available support elements, e.g., of the type disclosed in the Arnold and Salzmann patents, is the complexity of the stiffening members.  
           [0008]    As can be appreciated by those skilled in the art, it would be advantageous to provide a support element that has less complicated stiffening members joining the exterior rods.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention relates to an article, e.g., a support element, having a plurality of longitudinal members, e.g., from rods such as round stock or rebar, secured in special relationship to one another by one or more reinforcement members, hereinafter also referred to as “quadrilateral reinforcement member” or “QRM”.  
           [0010]    The first rod, second rod, third rod, and fourth rod of the support element are preferably spaced apart from one another with the first rod and the second rod each lying in a first imaginary plane, the second rod and the third rod each lying in a second imaginary plane, the third rod and the fourth rod each lying in a third imaginary plane, and the first rod and the fourth rod lying in a fourth imaginary plane. In one non-limiting embodiment of the invention, the support element has at least one set of opposed imaginary planes parallel to one another, e.g., the first and third imaginary planes or the second and fourth imaginary planes parallel to one another. In another non-limiting embodiment of the invention, the support element has both sets of opposed imaginary planes parallel to one another, e.g., the first and third imaginary planes and the second and fourth imaginary planes parallel to one another. In a further non-limiting embodiment of the invention, the first imaginary plane is spaced from and substantially parallel to the third imaginary plane; the second imaginary plane is spaced from and substantially parallel to the fourth imaginary plane; and the first and third imaginary planes are each substantially perpendicular to the second imaginary plane and the fourth imaginary plane. With the foregoing arrangement, the support element may have a trapezoidal, a rectangular, a square, or other cross-sectional shape having one set or two sets of parallel imaginary planes or sides.  
           [0011]    The first QRM preferably has a hollow square cross-sectional shape, but the actual shape of the first QRM is largely dependent on the cross-sectional shape defined by the four rods. The first QRM preferably has a first segment, a second segment connected perpendicularly to one end of the first segment, a third segment connected perpendicularly to one end of the second segment, and a fourth segment joining the other end of the first segment to the other end of the third segment.  
           [0012]    In a non-limiting embodiment of the invention, the first QRM is positioned inside the first, second, third, and fourth rods, substantially perpendicular to the first imaginary plane and third imaginary plane, and preferably at an angle with respect to the second imaginary plane and the fourth imaginary plane. A second QRM may also be provided inside the first, second, third, and fourth rods, wherein the second QRM is spaced away from the first QRM or positioned immediately adjacent to the first QRM. The second QRM is also positioned substantially perpendicular to the first imaginary plane and third imaginary plane, and preferably forms the same angles with respect to the second imaginary plane and the fourth imaginary plane as the first QRM. The first and second QRMs may be defined as a QRM pair or reinforcement group with the distance between the first and second QRMs at the second imaginary plane being different than the distance between the first and second QRMs at the fourth imaginary plane. In another non-limiting embodiment, the second QRM is positioned substantially perpendicular to the second and fourth imaginary planes and preferably form an angle with the first and third imaginary planes.  
           [0013]    Additional QRMs or QRM pairs may also be added, with each subsequent QRM or QRM pair spaced from the other QRM pairs in a repetitious, symmetric manner.  
           [0014]    The QRM pairs described above are preferably bounded by the first imaginary plane, the second imaginary plane, the third imaginary plane, the fourth imaginary plane, the first rod, the second rod, the third rod, and the fourth rod. Although not limiting to the invention, external side braces or support members may also be added to the rods for added strength. For example, a side brace can be positioned parallel to the first imaginary plane and connected to the first rod and the second rod. A second side brace can be positioned parallel to the third imaginary plane and connected to the third rod and the fourth rod. The side braces can be positioned between the first QRM and second QRM in a QRM pair or can overlap the first or second QRM of the QRM pair.  
           [0015]    One advantage of the present invention is that the square or rectangular cross-sectional configuration of the four rods permits forces acting on the support element to transfer through the four rods linearly along the rods and through the QRMs and QRM pairs. The four rod configuration, preferably spaced apart to form a square or rectangular cross section, along with the QRM pairs and, optionally, side braces, provides similar strength symmetry or the same strength symmetry, depending on the support element design, regardless of the orientation of the support element, and is generally a lighter alternative to other commercially available support elements. The present invention can also be constructed from lighter materials, thus making the present invention less expensive to manufacture. Moreover, by adding more QRM pairs, or by adding side braces to an exterior of the four rods, or by overlapping interior QRM pairs with additional exterior side braces, the support element according to the present invention may be modified to resist heavier loads. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is an end view of a non-limiting support element incorporating features of the invention;  
         [0017]    [0017]FIG. 2 is a side view of the support element shown in FIG. 1;  
         [0018]    [0018]FIG. 3 is a top view of the support element shown in FIG. 1;  
         [0019]    [0019]FIG. 4 is an end view of another non-limiting support element incorporating features of the invention;  
         [0020]    [0020]FIG. 5 is a side view of the support element shown in FIG. 4;  
         [0021]    [0021]FIG. 6 is an orthogonal view of the support element shown in FIG. 4;  
         [0022]    [0022]FIG. 7 is an end view of still another non-limiting support element incorporating features of the invention;  
         [0023]    [0023]FIG. 8 is a side view of the support element shown in FIG. 7; and  
         [0024]    FIGS.  9 - 12  are views similar to the view of FIG. 8 showing additional non-limiting features of support elements incorporating features of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]    As used herein, spatial or directional terms, such as “inner”, “outer”, “left”, “right”, “up”, “down”, “horizontal”, “vertical”, and the like, relate to the invention as it is shown in the drawing figures. However, it is to be understood that the invention can assume various alternative orientations and, accordingly, such terms are not to be considered as limiting. Further, all numbers expressing dimensions, physical characteristics, and so forth, used in the specification and claims are to be understood as being modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical values set forth in the following specification and claims can vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Moreover, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range of “1 to 10” should be considered to include any and all subranges between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less, e.g., 5.5 to 10.  
         [0026]    In the following discussion, unless indicated otherwise, like numbers refer to like components.  
         [0027]    With reference to FIGS.  1 - 3 , there is shown a non-limiting support girder or support element  30  incorporating features of the invention. The support element  30  includes rods  32 - 35  arranged in a fixed relationship to one another by a plurality of reinforcement members; reinforcement member  37  is shown in FIG. 1 and reinforcements members  37 - 41  are shown in FIGS. 2 and 3. As can be appreciated, the invention is not limited to the number of reinforcement members used to secure the rods  32 - 35  in their fixed relationship, and the number of reinforcement members is dependent on the length of the rods, the length of the reinforcement members, and the orientation of the reinforcement members and the rods relative to one another. The orientation of the reinforcement members and the rods relative to one another is discussed in detail below. Each of the reinforcement members  37 - 41  has a four-sided configuration, e.g., a trapezoidal, a rectangular, or a square shape. Although in the following discussion the bars are arranged to have a four-sided configuration, the invention is not limited thereto and other configurations, e.g., a circle, oval, or ellipse can be made and used in the practice of the invention.  
         [0028]    With continued reference to FIGS.  1 - 3  as needed, the reinforcement members  37 - 41  each include elongated segments  42 ,  43 ,  44 , and  45  having their ends joined together in any usual manner, e.g., by welding to provide the reinforcement members  37 - 41  with a quadrilateral configuration having corners  50 ,  51 ,  52 , and  53  as shown clearly in FIG. 1. In the following discussion and in the claims, the reinforcement members  37 - 41  may also be referred to as “quadrilateral reinforcement members” or “QRMs”. Although not limiting to the invention, the rod  33  is secured at or adjacent the corner  51  of the QRMs  37 - 41 ; the rod  34  is secured at or adjacent the corner  52  of the QRMs  37 - 41 ; the rod  32  is secured at or adjacent the corner  50  of the QRMs  37 - 41 ; and the rod  35  is secured at or adjacent the corner  53  of the QRMs  37 - 41 . In the non-limiting embodiment of the support element  30 , the QRMs  37 - 41  are arranged in an alternating fashion such that one side of each one of the adjacent ones of the QRMs  37 - 41  are closer together than the opposite side of the adjacent ones of the QRMs  37 - 41 . More particularly and with reference to FIGS. 2 and 3 as needed, the QRM  37  has its member  43  and the corners  51  and  52  between the rods  33  and  34 , and its member  45  and corners  50  and  53  between the rods  32  and  35 ; the adjacent QRM  38  has its member  45  and corners  50  and  53  between the rods  32  and  35 , and its member  43  and corners  51  and  52  between the rods  33  and  34  with the member  43  of the QRMs  37  and  38  spaced a greater distance than the member  45  of the QRMs  37  and  38 . The QRMs  37  and  38  provide a first reinforcement group of the support element  30 . The QRM  39  has its member  43  and the corners  51  and  52  between the rods  33  and  34 , and its member  45  and corners  50  and  53  between the rods  32  and  35  with the member  45  of the QRMs  38  and  39  spaced a greater distance than the member  43  of the QRMs  38  and  39 ; the adjacent QRM  40  has its member  45  and corners  50  and  53  between the rods  32  and  35  and its member  43  and corners  51  and  52  between the rods  33  and  34  with the member  45  of the QRMs  39  and  40  spaced a greater distance than the member  43  of the QRMs  39  and  40 . The QRMs  39  and  40  provide a second reinforcement group of the support element  30 . The foregoing spacing relationship continues for the QRMs  40  and  41  along the length of the support element  30  and any additional reinforcement group that may be added to the support element  30 . In FIGS. 2 and 3, the QRM  41  is a QRM of the third reinforcement group of the support element  30 .  
         [0029]    With the above arrangement and as shown in FIG. 1, the rods  32  and  35  each lie in a first imaginary plane IP 1 , the rods  32  and  33  each lie in a second imaginary plane IP 2 , the rods  33  and  34  each lie in a third imaginary plane IP 3 , and the rods  34  and  35  each lie in a fourth imaginary plane IP 4 . As shown in FIG. 1 but not limiting to the invention, the first imaginary plane IP 1  is spaced from and substantially parallel to the third imaginary plane IP 3 , the second imaginary plane IP 2  is spaced from and substantially parallel to the fourth imaginary plane IP 4 , and the first imaginary plane IP 1  and the third imaginary plane IP 3  are each substantially perpendicular to the second imaginary plane IP 2  and the fourth imaginary plane IP 4 . The reinforcement members  37 - 41  each lie in a plane that subtends an angle α with imaginary planes IP 1  and IP 3  as shown in FIG. 3 in the range of greater than 0° to 90°, and a right angle with imaginary planes IP 2  and IP 4 . The angle α is not limiting to the invention and may be the same or different for each reinforcement member  37 - 41 . Although not limiting to the invention, the angle α is in the range of greater than 0° and less than 90°, preferably in the range of 30° to 60°, and more preferably 45°. As is appreciated by those skilled in the art, the angle α has a complementary angle on the other side of the reinforcement member.  
         [0030]    Although any side of the support element  30  may be used to support a load, the support element  30  has a higher load capacity with the rods  32  and  33  (IP 2 ), and rods  34  and  35  (IP 4 ) supporting (IP 2  and IP 4  normal to) the load than with the rods  32  and  35  (IP 1 ), and  33  and  34  (IP 3 ) supporting (IP 1  and IP 3  normal to) the load.  
         [0031]    The rods  32 - 35  and the reinforcement members  37 - 41  are preferably rigid, solid rods made from a structurally stable material, such as metal, e.g., steel, coated steel, fiberglass reinforced plastic, aluminum, or laminated wood. In the practice of the invention, the rods  32 - 35  are preferably made of steel round stock and the reinforcement members  37 - 41  are preferably made of rebars because rebars have a patterned surface for the cement to adhere. In the instance when the support element is used in a corrosive, e.g., damp, environment, the support element may be coated with epoxy and/or zinc-iron to prevent rusting of the rebars. As can be appreciated by those skilled in the art, the invention is not limited to the material or surface of the rods and/or reinforcement members, and the rods  32 - 35  and/or the reinforcement members  37 - 41  may be made of solid bars having a smooth or patterned surface and/or structurally stable hollow bars having a smooth or patterned outer surface. Although the invention is not limiting to the number of QRMs used to maintain the rods in a fixed relationship to one another, a sufficient number of QRMs should be used for ease of handling the support elements, e.g., at least two QRMs, to minimize flexing of the rods  32 - 35 .  
         [0032]    As can now be appreciated, the invention is not limited to the dimensions of the rods  32 - 35 , of the QRMs, or of the segments  42 - 45  of the QRMs. More particularly, the length of the support element  30  should be sized such that the support element  30  is manageable during transportation and moving into position to support a load. Lengths of 12 to 15 feet (3.65 to 4.57 meters) are usually manageable. Consider now the structural stability of the support element  30 . As the load on the rods  32 - 35  increases, and the material of the rods and the dimension and material of the QRMs and the position of the QRMs to the rods is maintained constant, increasing the cross-sectional area, e.g., diameter of the rods  32 - 35 , increases the load bearing capabilities of the support element  30  and vice versa. As the load on the rods  32 - 35  increases, and the dimension of the rods and the dimension and material of the QRMs and the position of the QRMs to the rods is maintained constant, increasing the structural stability of the material of the rods  32 - 35  increases the load bearing capabilities of the support element  30  and vice versa. The invention is not limited to the cross-sectional area of the rods or the structural stability of the material of the rods, however, as can be appreciated by those skilled in the art, the cross-sectional area and structural stability of the material should be sufficient to support the maximum expected load to be supported. As the load on the rods  32 - 35  increases, and the dimensions and material of the rods and the material of the QRMs and the position of the QRMs to the rods is maintained constant, increasing the length of the segments  43  and  45  while keeping the length of the segments  42  and  44  constant, or decreasing the length of the segments  42  and  44  while keeping the length of the segments  43  and  54  constant, increases the load bearing capabilities of the support element  30  and vice versa. As the load on the rods  32 - 35  increases, and the dimensions and material of the rods and the dimension of the QRMs and the position of the QRMs to the rods is maintained constant, increasing the structural stability of the material of the segments of the QRMs increases the load bearing capabilities of the support element  30  and vice versa. As the load on the rods  32 - 35  increases, and the dimension and material of the rods and the dimension and material of the QRMs is maintained constant, decreasing the distance between the QRMs, e.g., the distance between sides  45  of the QRMs and the distance between sides  43  of the QRMs, increases the load bearing capabilities of the support element  30  and vice versa. In regards to the angle α, decreasing the angle α while keeping the distances between the rods constant, increases the length of the reinforcement members and increases the distance between the sides of the reinforcement members, e.g., sides  43  of the reinforcement members  37  and  38  shown in FIGS. 2 and 3. Therefore, decreasing the angle α reduces the number of reinforcement members securing the rods together and decreases the load bearing capacity of the support element  30 .  
         [0033]    As previously discussed, the support element  30  has a higher load bearing capacity with the rods  32  and  33 , and  34  and  35  supporting the load, i.e., planes IP 2  and IP 4  normal to the load, than having the rods  32  and  35 , and  33  and  34  supporting the load, i.e., the planes IP 1  and IP 3  normal to the load. Shown in FIGS. 4, 5, and  6  is support element  56  having load-bearing capacity with any one of the pair of rods supporting the load, i.e., with any one of the imaginary planes normal to the load. With reference to FIGS.  4 - 6  as needed, the rods  32 - 35  are held in a fixed relationship by a plurality of reinforcement members arranged in a sequence having the adjacent reinforcement member rotated 90°. More particularly, the reinforcement members  37 ,  39 , and  41  are mounted between the rods  32 - 35  as previously discussed and shown in FIGS. 2 and 3. The reinforcement members  38  and  40  are replaced with reinforcement members  59  and  60 . The reinforcement members  59  and  60  are similar in construction to the reinforcement members  38  and  40  with the difference being their orientation relative to the adjacent reinforcement members and the rods.  
         [0034]    The reinforcement members  37  and  59  are a first reinforcement group of the support element  56 . The reinforcement members  39  and  60  are a second reinforcement group of the support element  56 . The reinforcement member  41  is one of the reinforcement members of the third reinforcement group of the support element  56 . As can now be appreciated, the invention is not limited to the number of reinforcement groups used to maintain the rods  32 - 35  of the support element  56  in spaced relationship to one another.  
         [0035]    Each of the reinforcement members  59  and  60  includes elongated segments  62 - 65  joined at their ends to form corners  68 - 71 , as shown in FIGS.  4 - 6 . More particularly, the segment  63  is connected to the segment  62  at the corner  69  and to the segment  64  at the corner  70 , and the segment  65  is connected to the segment  62  at the corner  68  and to the segment  64  at the corner  71 . The segment  62  and corners  68  and  69  are between the rods  32  and  33 , and the segment  64  and corners  70  and  71  are between the rods  34  and  35 . As shown in FIG. 6, the reinforcement members  37 ,  39 , and  41  each lie in a plane that is normal to the imaginary planes IP 2  and  1 P 4  and at the angle α to the imaginary planes IP 3  and IP 1 . The reinforcement members  59  and  60  each lie in a plane that is normal to the imaginary planes IP 1  and IP 3  and at an angle B with the imaginary planes IP 2  and IP 4 . As can be appreciated, the invention contemplates that the angles α and B may be equal to one another or different from one another. In the practice of the invention, it is preferred, although not limiting to the invention, that the angles α and B are equal to one another. In this manner, the support element  56  has essentially the same load capacity regardless of what imaginary plane is normal to the load.  
         [0036]    As can now be appreciated, the concepts of the support elements  30  and  56  can be combined. In one non-limiting embodiment and with reference to FIGS. 2 and 5, the reinforcement member  59  can be positioned between the reinforcement members  37  and  38 ; the reinforcement member  60  can be positioned between the reinforcement members  38  and  39 ; and a reinforcement member similar to the reinforcement members  59  and  60  can be positioned between the reinforcement members  39  and  40  and between reinforcement members  40  and  41 . In another non-limiting embodiment of the invention and with reference to FIG. 5, one of the reinforcement members  59  or  60  may be rotated clockwise 90° as viewed in FIG. 5 to provide a spacing relationship and orientation similar to that shown in FIG. 3.  
         [0037]    The discussion above regarding the range of degrees of the angle α is applicable for the angle B. Further, the discussion regarding increasing the load bearing capacity of the support element  30  is applicable to increasing the load bearing capacity of the support element  56  and any variations thereof.  
         [0038]    Shown in FIGS. 7 and 8 is support element  75  incorporating features of the invention. The support element  75  includes the rods  32 - 35  arranged in the imaginary planes IP 1 - 1 P 4  in a manner to be discussed below. It should be noted that for ease of discussion, the imaginary planes IP 1 - 1 P 4  of the support element  75  shown in FIG. 7 are made up of the same rods as the imaginary planes of the support element  30  of FIG. 1; the difference is that the rods  32 - 35  and the imaginary planes of FIG. 1 are rotated clockwise 90° as shown in FIG. 7. The rods  32 - 35  are spaced from one another by reinforcement members  78 - 80 . Each of the reinforcement members  78 - 80  includes elongated segments  82 - 85  having their ends joined together to provide the reinforcement members with corners  88 - 91 . The corners  88 - 91  are radiused to illustrate another non-limiting embodiment of the invention. The rods  32 - 35  are secured to the corners  88 - 91  respective in any usual manner, e.g., by welding. The reinforcement members  78 - 80  are secured to the rods  32 - 35  in an orientation similar to the orientation of the reinforcement members  37 - 41  shown in FIG. 3.  
         [0039]    With reference to FIG. 7, to provide additional structural support to maintain the rods in position when the load is normal to the imaginary planes IP 1  and IP 3 , the support element  75  further includes side braces  94  and  95  secured to outer surface portions of the rods  32  and  33 , and  34  and  35 , respectively. Each of the side braces  94 ,  95  has elongated segments  96 - 99  having their ends joined together to provide the side braces  94 ,  95  with a quadrilateral configuration having corners  101 - 104 . The corners  101 - 104  are shown as radiused; however, as can be appreciated, the invention is not limited thereto and the corners may be squares, as shown for the reinforcement member  37  shown in FIG. 1.  
         [0040]    With reference to FIG. 8, the adjacent reinforcement members  78  and  79 , and  79  and  80  are spaced from one another a distance greater than the length of the side brace mounted between adjacent reinforcement members. The side braces may be opposite one another, e.g., secured to the outer surface portion of the rods  32  and  33 , and to the outer surface portion of the rods  34  and  35 , or the side braces may alternate with a side brace on one side of the support member, e.g., to the outer surface of the rods  32  and  33  and no brace on the opposite side, e.g., on the outer surface portion of the rods  32  and  33 . Further, a side brace does not have to be between adjacent reinforcement members, e.g., side braces are mounted between groups of two or more reinforcement members.  
         [0041]    The reinforcement members  78  and  79 , and side braces  94  and  95  are one reinforcement group of support element  75  and reinforcement group  80  is a reinforcement member of the next reinforcement group of the support element  75 . The reinforcement group of the support element  75  is repeated for the length of the support element  75 .  
         [0042]    FIGS.  9 - 12  show additional non-limiting embodiments of support elements having various combinations of side braces and reinforcement members. The end view of the support elements of FIGS.  9 - 12  are similar to the end view of support element  75  shown in FIG. 7.  
         [0043]    In FIG. 9, the support element  110  has the reinforcement members  78 - 80  closer together than the arrangement shown in FIG. 8. The side braces  94 - 96  are arranged between adjacent reinforcement members and alternating from one side of the support element to the opposite side. More particularly, the side brace  94  is in the space between the reinforcement members  78  and  79  and secured to the outer surface portions of the rods  32  and  33 . Moving to the right of the reinforcement member  79  as viewed in FIG. 9, the next side brace  95  is in the space between the reinforcement members  79  and  80  and secured to the outer surface portions of the rods  34  and  35 . Moving to the right of the reinforcement member  80  as viewed in FIG. 9, the next side brace  96  is in the space between the next two reinforcement members (only reinforcement member  80  shown in FIG. 9) and secured to the outer surface portions of the rods  32  and  34 . The reinforcement members  78  and  79 , and side braces  94  and  95  form one reinforcement group of the support element  110 . The reinforcement group of support element  110  shown in FIG. 9 is repeated for the length of the support element  110 . In FIG. 9, reinforcement member  80  and side brace  96  are part of the second reinforcement group of the support element  110 .  
         [0044]    In FIG. 10 there is shown support element  112  having the reinforcement members  78 - 80  and  113 . The reinforcement member  113  is similar to reinforcement member  79  in construction and mounting between the bars. In FIG. 10, the reinforcement members  78 - 80  and  113  are closer together such that a side brace overlays the adjacent sides of adjacent reinforcement members. As shown in FIG. 10, the side brace  95  is secured to the outer surface portions of the rods  34  and  35  and overlays the reinforcement members  78  and  79 ; the side brace  94  is to the right of the side brace  95 , as viewed in FIG. 10, and is secured to the outer surface portions of the rods  32  and  33  and overlays portions of adjacent reinforcement members  79  and  80 ; the side brace  96  is to the right of the side brace  94 , as viewed in FIG. 10 and is secured to the outer surface portions of the rods  32  and  33  and overlays portions of the reinforcement members  80  and  113 . The reinforcement members  78 ,  79 ,  80 , and  113  and side braces  94 ,  95 , and  96  are one reinforcement group of the support element  112 . The reinforcement group shown in FIG. 10 is repeated for the length of the support element  112 . More particularly, side brace  114  overlapping portions of reinforcement member  78  is a part of the reinforcement group of the support element  112  to the left of reinforcement member  78  as shown in FIG. 10, and side brace  115  overlapping portions of reinforcement member  113  is part of the reinforcement group of the support element  112  to the right of reinforcement member  112  as shown in FIG. 10.  
         [0045]    With reference to FIG. 11, there is shown support element  116  having the reinforcement members  78 - 80  oriented and spaced as shown in FIG. 8 with a side brace between adjacent reinforcement members and secured to outer surface portions of the rods  34  and  35 . More particularly, the side brace  95  is between the reinforcement members  78  and  79 , and the side brace  118 , similar in construction to the side brace  95 , is between the reinforcement rods  79  and  80 . The side brace  95  is secured to the outer surface portions of the rods  32  and  33  and the side brace  118  is mounted to the inner surface portion of the rods  32  and  33 . As can be appreciated, because the spacing between adjacent reinforcement members is greater than the length of the side braces, the side braces may both be mounted to the outer surface portions or to the inner surface portions of the rods  32  and  33 . The reinforcement members  78  and  79  and the side braces  95  and  118  make one reinforcement group of the support element  116 . The reinforcement member  80  is a part of the next reinforcement group of the support element  116 . The side braces of the reinforcement groups of the support element  116  may all be secured to the outer or inner surface portions of the rods  34  and  35 , or may be all on the inner or outer side portions of the rods  32  and  33 , or may alternate from the side portions of the rods  34  and  35  to the side portions of the rods  32  and  33 .  
         [0046]    With reference to FIG. 12, there is shown support element  120  incorporating features of the invention. The support element  120  is similar to the support element  112  shown in FIG. 10 with the following differences. The reinforcement group of FIG. 12 has the side braces on the outer surface portion of the rods  34  and  35  and the side brace overlapping the portions of the reinforcement members  79  and  80  at their side closest to one another. The reinforcement group of support element  120  includes the side braces  94 - 96  and the reinforcement members  79 ,  80 ,  113 , and  122 . The reinforcement groups of support element  120  may be repeated along the length of the support element, or the reinforcement group may alternate between the outer surface of the rods  34  and  35  or the outer surface of the rods  32  and  33 , or may have a number of reinforcement groups on the outer surface of the rods  34  and  35  before providing reinforcement groups on the other side of the support member.  
         [0047]    While the invention is described in detail herein, it will be appreciated by those skilled in the art that various modifications and alternatives to the arrangements can be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements described above are illustrative only and are not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.