Patent Publication Number: US-2011047722-A1

Title: Hoop Truss Bridge

Description:
BACKGROUND OF THE INVENTION 
     Truss bridges are one of the oldest types of modern bridges. The traditional truss bridge comprises a framed structure of connected elements which may be stressed from tension, compression, or sometimes both in response to dynamic loads. Typically the structural members are straight. However, it is the object of the present invention to depart from the traditional structural triangles and rectangles that are common elements of the many types of trusses that comprise bridge designs and employ for bridge construction a type of structure that is more akin to a semimonocoque type of aircraft fuselage without or with only partial skin. 
     SUMMARY OF THE INVENTION 
     The bridge of the present invention constitutes a tubular beam that is defined by a plurality of hoop shaped web members that are disposed diagonally and are antipodally interconnected in the general form of the web members of a Warren truss. The central axis of the hoop truss web members may be a straight line or a horizontally or vertically curved line. The beam-forming web member hoops are additionally interconnected with beam flanges which may be in the form of stringers that are attached to the hoop web members and run parallel to the central axis of the hoops. The beam flanges can also be in the form of a top and bottom skin that overlies and is attached to the hoop members. Depending on the required strength of the tubular truss beam, the flange members can be either or both stringers and skin. A road bed is disposed along the length of the tube in the position of a chord of the hoop shaped web members. For short spans the tube may be self supporting and for longer spans overhead support cables may be employed to supplement the self support of the tubular beam. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a fragmentary perspective view of the hoop truss bridge of the present invention where the skin is broken away to reveal the interior structure and where the center line of the bridge is a straight line. 
         FIG. 2  is a lateral cross-sectional diagram of the bridge shown in  FIG. 1 . 
         FIG. 3  is a fragmentary side elevation of the bridge shown in  FIG. 1 . 
         FIG. 4  is a fragmentary plan view of the bridge shown in  FIG. 1 . 
         FIG. 5  is a diagrammatic plan view of an alternate embodiment of the bridge where the center line is a curve 
         FIG. 6  is a front view of an exemplary hoop where the hoop is constructed of a plurality of chords of a circle. 
         FIG. 7  is a diagrammatic side view of the hoop truss bridge where the truss has a vertical camber and the center line is a curve. 
         FIG. 8  is a side elevational view of a long span version of the truss bridge showing overhead support cables. 
         FIG. 9  is a plan view of the long span version of the bridge shown in  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1-4  illustrate the basic construction of a bridge  2  of the present invention. The tubular structure of the bridge is illustrated in  FIG. 1  where each of a plurality of hoops  4  acts as a former for the tube  14 . In this specification and the accompanying claims the word “tubular” includes cylindrical and tubes of ellipitacal cross section. Accordingly, the hoops forming the tube may be elliptical toroidal, true toroidal, elliptical, or circular in their shape. Furthermore, each of these shapes may be constructed as a unitary element or constructed from a series of interconnected chords  5  of a circle, as shown in  FIG. 6 . As a further lexicographer&#39;s note, although the drawings presented in connection with this specification show the formers  4  as circular in their shape, the generically descriptive words “hoop” or “hoop shaped” in the explanation of the invention and the subsequent claims should be interpreted as including, in the alternative, each of the foregoing closed plane curve structures as comprising the truss web members. The hoops may be constructed of metal or other material appropriate to the stresses and loads being imposed on the hoop truss web members. 
     One of the novel aspects of this invention is that the hoops have a common central axis. which may be a straight or curved line. In all cases, adjacent hoops are angularly disposed with respect to each other and with respect to a vertical cross section of the tube  14  shown in  FIG. 2 . In the embodiment of the tubular bridge where the common central axis is a straight line, every other one of the hoops is mutually parallel. In the straight line version of the bridge, the angles  20  and  22  between adjacent hoops are equal. 
     Every other hoop is interconnected at its antipodal points with the antipodal points on the intervening hoop. The configuration of the web member hoops is similar to that of the diagonal members of a typical Warren type of truss where longitudinal flange members are joined only by angled cross web members, forming alternately inverted triangle-shaped spaces along the length of the truss, ensuring that no individual strut, beam, or tie is subject to bending or torsional straining forces, but only to tension or compression. 
     To complete the total truss structure of the bridge  2 , the hoop shaped members  4  that comprise the web of the truss beam and define the tube  14  are also interconnected with flange forming longitudinal stringers  6  that are disposed parallel to the central axis  16  of the hoops and are connected to spaced apart points around the inside or outside perimeter of the hoops  4 . 
     In addition to or alternative to the foregoing described structure of flange forming stringer members, upper and lower flange-forming skins  10  and  12  may be attached to the hoop web members and applied to portions of the outside perimeter of the tubular bridge structure. 
     The bridge includes one or more load carrying decks  8  that run the longitudinal length of the tube  14  and are positioned as one or more chords of the truss hoops as best seen in  FIG. 2 . In addition to carrying out the structural function of one of the tubular beam&#39;s flanges, the upper skin  10  serves as a protective roof over the traffic deck  8 . 
     Each of the web member hoops  4  has a major axis, or, in the particular case of a circular hoop, a diameter  7 . Antipodal nodes  15  exist at the intersections of the major axis with the top and with the bottom of the perimeter of each of the hoops  4 . In the embodiment of the bridge where the central axis is a straight line, as shown in  FIGS. 1-4 , the hoops abut and are joined at their antipodal nodes  15 . 
     In an alternate embodiment of the bridge as shown in  FIG. 5 , the central axis  16  is curved horizontally. In such a configuration the web member hoops  4  abut and are interconnected at antipodes  13 , which are angularly off set from the nodes  15 . The degree of angular off set depends on the curvature desired. 
       FIG. 7  illustrates a third embodiment of the bridge where the central axis  16  is cambered vertically. The camber is obtained in varying degrees depending on the departure from equality of the angles between adjoining hoops. In the anticline embodiment shown in  FIG. 7  the angle  22  is less than the angles  20 . 
     The tubular configuration of the bridge may take a combination of horizontal curves and vertical camber. 
       FIGS. 8 and 9  illustrate a long span version of the tubular bridge  2 . Diagonally disposed vertical supports  25  anchor one or more supporting cables  27  which attach at their distal ends to the truss hoops or other structural features of the bridge which may be available to support the structure. 
     The foregoing description is only illustrative of the invention. Various alternatives, modifications, and variances can be devised by those skilled in the art without departing from the spirit of the invention. Accordingly, the present invention embraces all such alternatives, modifications, and variances that fall within the scope of the described invention.