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FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to joints and, more specifically, to expansion joints.  
         BACKGROUND OF THE INVENTION  
         [0002]    Due to weight and size of major components, concrete and steel road bridges are built on-site instead of pre-fabricated off site. On-site construction is expensive and time consuming. This results in traffic delays and safety concerns. Concrete and steel bridges also corrode and deteriorate over time. This requires continuous maintenance and upkeep, as well as costly inspection and repair.  
           [0003]    On the other hand, bridges made of composite material, such as carbon/epoxy or fiberglass do not corrode. Advantageously, composite materials have high fatigue resistance, and high strength and stiffness-to-weight ratios. These characteristics of composite materials result in light-weight components. As a result, composite material components of bridges may be pre-fabricated off-site and easily transported to the site for final assembly.  
           [0004]    The bridge components have coefficients of thermal expansion associated with the composite material from which they are made. The composite deck sections expand and contract according to their coefficients of thermal expansions and variations in temperature to which they are subjected. As a result, an expansion region is provided to accommodate thermal expansion or contraction.  
           [0005]    It is required that such an expansion joint is provided between adjacent composite bridge deck sections. To avoid vertical steps in the surface, expansion joint components are made of the same material as the composite bridge deck sections so the expansion joint and the composite bridge deck section have the same coefficient of thermal expansion. However, there is an unmet need in the art for the expansion joint components to be made from the same composite material as the composite bridge deck sections, and for easy fabrication and assembly.  
         SUMMARY OF THE INVENTION  
         [0006]    Embodiments of the present invention provide an expansion joint for joining adjacent sections of a structure. In one presently preferred embodiment, the structure is a bridge, in which the adjacent deck sections are of composite construction. Advantageously, the expansion joint is preferably made from the same material as the adjacent sections. As a result, the present invention provides an expansion joint that has the same coefficient of thermal expansion as the adjacent sections of the structure and avoids steps in the surface. In composite embodiments of the present invention, the expansion joint is light weight, has high strength characteristics, and is easy to fabricate.  
           [0007]    According to an embodiment of the present invention, an expansion joint is provided for joining adjacent sections of a structure. The expansion joint includes a first generally planar member that is configured to provide sliding support of at least one section of a structure thereon. Second and third generally planar regions are firmly attached to an expanding intermediate section that can slide on the lower main support beam. The second and third members are substantially co-planar with each other and are substantially parallel to the first member. The second and third members are vertically spaced-apart from the first member. The lower region of the intermediate member expands or contracts with temperature changes to allow it to be firmly attached to the adjacent panel members. The intermediate member is firmly attached to the main support structure at the center. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.  
         [0009]    [0009]FIG. 1 is a perspective view of an expansion joint according to one embodiment of the present invention joining adjacent sections of a structure;  
         [0010]    [0010]FIG. 2 is a side view of an expansion joint of the present invention;  
         [0011]    [0011]FIGS. 3A and 3B are partial cutaway, perspective views of a bridge with expansion joints according to the present invention;  
         [0012]    [0012]FIG. 4 is a top plan view of bridge deck sections joined by an expansion joint of the present invention; and  
         [0013]    [0013]FIG. 5 is a side view of an expansion join according to an alternate embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]    By way of overview and referring to FIG. 1, an embodiment of the present invention provides an expansion joint  10  for joining adjacent sections  12  and  14  of a structure  16 , such as without limitation a bridge. The expansion joint  10  and the sections  12  and  14  are supported on a beam  17 . Beam  17  is not necessarily of composite material. The expansion joint  10  includes a first generally planar member  18  that is configured to slide on a first portion  20  of the section  12  and a first portion  22  of the section  14  thereon. Second and third generally planar members  24  and  26  are configured to slidably receive a second portion  28  of the section  12  and a second portion  30  of the section  14  thereon. The second and third members  24  and  26  are substantially co-planar with each other and are substantially parallel to the first member  18 . The second and third members  24  and  26  are vertically spaced-apart from the first member  18  by fourth and fifth members  25  and  27 , respectively. An expansion device  32  is interposed between the second and third members  24  and  26 . The device  32  is attached at its center to the beam  17  and is attached to the panels  12  and  14  away from the beam  17  to allow expansion. The gap  34  is maintained between the sections  12  and  14  to accommodate thermal expansion and contraction.  
         [0015]    Referring now to FIGS. 1 and 2, features of one presently preferred embodiment of the expansion joint  10  will be set forth in further detail. The sections  12  and  14  are panel sections of the structure  16 . Given by way of nonlimiting example, the sections  12  and  14  are load carrying bridge deck sections. The sections  12  and  14  have upper surfaces  36  and  38 . The upper surfaces  36  and  38  each provide a surface suitable for surface traffic. For example, the surfaces  36  and  38  may be included among the surfaces of a bridge deck upon which vehicles or pedestrians travel.  
         [0016]    The sections  12  and  14  are suitably made of composite material, such as without limitation carbon/epoxy or fiberglass. In this case, the expansion joint  10  is also made of similar composite material as the sections  12  and  14 . Advantageously, this permits the expansion joint  10  and the sections  12  and  14  to have the same coefficient of thermal expansion. Alternately, the sections  12  and  14  may be made of other suitable materials, such as without limitation other materials having the same effective expansion characteristics, as desired for a particular application. The expansion joint  10  in this case is also made of the same material as the panel, such that the expansion joint  10  and the sections  12  and  14  have the same coefficient of thermal expansion. The spring material of component  32  need not be of the same material as the panels  12  and and  14 . Regardless of the materials chosen for the expansion joint  10  and the sections  12  and  14 , when the expansion joint  10  and the sections  12  and  14  are made of the same materials the expansion joint  10  and the sections  12  and  14  have the same coefficient of thermal expansion.  
         [0017]    The expansion joint  10  advantageously permits the sections  12  and  14  to abut each other with an expansion gap on the first member  18  instead of overlap each other on the expansion joint  10 . This enhances symmetry and enhances ease of assembly and individual removal from the structure  16 . To that end, lower faces  40  and  42  of the upper surfaces  36  and  38 , respectively, are allowed to slide on top of the first member  18 . Advantageously, in this embodiment, both of the sections  12  and  14  abut each other across a gap where the lower faces  40  and  42  are supported on the first member  18  and define the expansion gap  34 . As such, the sections  12  and  14  advantageously do not overlap each other. Instead, the sections  12  and  14  present a smooth traveling surface. Further, when load from a vehicle or traveler (not shown) is presented across the expansion gap  34 , advantageously the load is presented onto the expansion joint  10  at the first member  18  and is evenly distributed by the expansion joint  10  to the beam  17 .  
         [0018]    The expansion gap  34  is defined between ends of the sections  12  and  14  at the first portions  20  and  22 , respectively. The expansion gap  34  may have a width that accommodates thermal expansion and contraction of the sections  12  and  14 . The expansion gap  34  may be selected as desired for a particular application.  
         [0019]    The sections  12  and  14  have lower faces  44  and  46 , respectively. The lower faces  44   28  and  30  are received on the second and third members  24  and  26  at recesses  48  and  50  that are defined in the second portions  28  and  30  of the sections  12  and  14 , respectively. At portions of the sections  12  and  14  other than the second portions  28  and  30 , the lower faces  44  and  46  are received upon the beam  17 .  
         [0020]    Holes  52  and  54  are used to connect sections  28  and  30  of the sections  12  and  14 , respectively to sections  24  and  26  of connector  18  and line up axially with the holes  52  and  54 . Suitable fasteners (not shown), such as bolts, are received within the axially lined-up holes  52  and  56  and the axially lined-up holes  54  and  58 . This fastens the sections  12  and  14  to the expansion joint  10 . However, sections  12  and  14  remain unfastened to the beam  17 .  
         [0021]    In one presently preferred embodiment, the connecting device  32  is an expansion spring. The expansion spring has elasticity to allow the required expansion with sufficiently low stress levels to avoid fatigue failure. The spring is suitably corrugated for this purpose. The corrugated member  60  suitably defines peaks  62  and  64  and a trough  66  interposed between the peaks  62  and  64 . A hole  68  is defined in the trough  66 , and a hole  70  is defined in the beam  17 . The holes  68  and  70  are axially aligned with each other. A suitable fastener, such as a bolt  72 , is received within the axially-aligned holes  68  and  70  and is secured with a nut  74  or the like. This secures the expansion joint  10  to the beam  17 .  
         [0022]    In summary, the sections  12  and  14  are fastened at the second portions  28  and  30 , respectively, to the expansion joint  10  at the second and third members  24  and  26 . However, the sections  12  and  14  are not fastened to the beam  17 . Instead, the expansion joint  10  is fastened to the beam  17 . The first portions  20  and  22  of the sections  12  and  14  are slidably received on the first member  18  and define the expansion gap  34  therebetween. As the sections  12  and  14  thermally expand or contract, the first portions  20  and  22  slide along the first member  18 . To this end, the expansion gap  34  advantageously accommodates thermal expansion of the sections  12  and  14 . Further, as the sections  12  and  14  thermally expand or contract, the expansion or contraction causes the second and third members  24  and  26  (that are attached to the sections  12  and  14  via fasteners through the second portions  28  and  30 ) to move toward each other or move away from each other. However, the device  32  allows movement of the second and third members  24  and  26 . As a result, the expansion gap  34  varies with temperature. Because the expansion member  18  and the sections  12  and  14  have the same expansion characteristics, sections  12  and  14  remain in horizontal alignment. The expansion or contraction is substantially the same for the expansion member  18  and the sections  12  and  14 .  
         [0023]    Referring now to FIGS. 3A, 3B, and  4 , a bridge  16  advantageously is constructed using several of the expansion joints  10 . A plurality of the beams  17  are supported on a plurality of supports  76 . The expansion joints  10  are placed on top of the beams  17  perpendicular to the beams  17  and are fastened to the beams  17  with the fasteners  72  as described above. The sections  12  and  14  are fastened to the second and third members  24  and  26  with fasteners through the holes  52  and  54  as described above.  
         [0024]    [0024]FIG. 5 shows an expansion joint  110  according to an alternate embodiment of the present invention. It will be appreciated that like reference numerals are used to refer to components or items previously described with reference to the expansion joint  10  (FIGS. 1-4). The expansion joint  110  is configured to join overlapping sections  112  and  114  of a structure  116 . The structure  116  is similar to the structure  16  (FIGS. 1-4). The sections  112  and  114  panel sections, such as panel bridge deck sections, and are suitably constructed similar to the sections  12  and  14 . An upper surface  136  of the section  112  abuts an upper section  138  of the section  114  across a gap at first portions  120  and  122 , respectively to define the expansion gap  34 . An overlapping portion  121  of the section  112  extends beyond the upper surface  136  and is able to slide on the first member  18 . The bottom of the first portion  122  slides on top of the overlapping portion  121 . As a result, load is distributed by the sections  112 ,  114 , and the expansion joint  110  when weight transitions between the sections  112  and  114 .  
         [0025]    The first, second, third, fourth, and fifth members  18 ,  24 ,  25 ,  26 , and  27  are constructed as set forth for the expansion joint  10 . However, an expansion device  132  suitably includes an expansion member  160  that performs the same function as the expansion device  32 . The member  160  advantageously has a simple shape that is easy to fabricate.  
         [0026]    The second and third members  24  and  26  define the holes  56  and  58  that axially line up with the holes  52  and  54  that are defined in the sections  112  and  114 . A hole  180  is defined in the beam  17  and is axially aligned with the holes  52  and  56 . A suitable fastener (not shown) fastens the section  112  and the expansion joint  110  to the beam  17  via the holes  52 ,  56 , and  180 . Another suitable fastener (not shown) fastens the section  114  to the expansion joint  110  via the holes  54  and  58 , but not to the beam  17 .  
         [0027]    While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment.

Summary:
An expansion joint is provided for joining adjacent sections of a structure. The expansion joint includes a first generally planar member that is configured to allow sliding of a first portion of at least one section of a structure thereon. Second and third generally planar members are configured to allow sliding of a second portion of at least one section of the structure thereon. The second and third members are substantially co-planar with each other and are substantially parallel to the first member. The second and third members are vertically spaced-apart from the first member. An expansion device is interposed between the second and third members. The expansion device accommodates expansion and contraction due to thermal effects of the second and third members and maintains horizontal alignment. Each surface panel may be removed independently for replacement or repair.