Abstract:
A bearing is provided for use in connection with expansion joint systems. The structure of the bearing permits improved motion of, and provides improved support for, the components of the expansion joint system that are supported on or engaged with the bearing. The bearing is particularly useful for expansion joint systems in roadway constructions, bridge constructions, and architectural structures.

Description:
BACKGROUND  
       [0001]     The present invention relates to a bearing structure. The present invention more particularly relates to a bearing structure for an expansion joint system and an expansion joint system including the bearing structure.  
         [0002]     An opening or gap is purposely provided between adjacent concrete structures for accommodating dimensional changes within the gap occurring as expansion and contraction due to temperature changes, shortening and creep of the concrete caused by prestressing, seismic cycling and vibration, deflections caused by live loads, and longitudinal forces caused by vehicular traffic. An expansion joint system is conventionally utilized to accommodate these movements in the vicinity of the gap.  
         [0003]     Bridge constructions are also subject to relative movement in response to occurrence of thermal changes, seismic events, and vehicle loads. This raises particular problems, because the movements occurring during such events are not predictable either with respect to the magnitude of the movements or with respect to the direction of the movements. Gaps or openings in the bridge deck are provided for accommodating these movements, and expansion joint systems are often installed in the gap. In many instances, bridges have become unusable for significant periods of time, due to the fact that traffic cannot travel across damaged expansion joints.  
         [0004]     Prior art expansion joint systems include various types of bearings for absorbing loads applied to the expansion joint system and for supporting the various expansion joint system components. However, many of the bearings used in expansion joint systems cannot absorb the increased loads and rotations that are demanded by the roadway and bridge designs. Therefore, a need still exists in the art for an improved bearing structure that can accommodate increased loads and an expansion joint system including an improved bearing that can accommodate movements that occur in the vicinity of a gap having an expansion joint between two adjacent roadway sections, for example, movements that occur in longitudinal and transverse directions relative to the flow of traffic, and which are a result of thermal changes, seismic events, and deflections caused by vehicular loads.  
       SUMMARY  
       [0005]     A bearing structure is provided, said bearing structure comprising a bearing substrate and an upper bearing portion disposed on a portion of said bearing substrate, said upper bearing portion including concavely curved side walls.  
         [0006]     According to certain embodiments, the upper bearing portion includes curved side walls, a substantially curved upper bearing surface, and a flat seat region.  
         [0007]     An expansion joint system is further provided for a roadway construction wherein a gap is defined between adjacent first and second roadway sections, said expansion joint system extending across said gap to permit vehicular traffic, said expansion joint system comprising transversely extending, spaced-apart, vehicular load bearing members, elongated support members having opposite ends positioned below said transversely extending load bearing members and extending longitudinally across said expansion joint gap, first means for accepting ends of said longitudinally extending elongated support members for controlling the movement of said ends of said support members within said first means for accepting longitudinally extending elongated support members, second means for accepting opposite ends of said longitudinally extending elongated support members for controlling the movement of said opposite ends of said support members within said second means for accepting longitudinally extending elongated support members, and bearing means disposed between said ends of said longitudinally extending elongated support members and said first and second means for accepting ends of said longitudinally extending elongated support members, said bearing means comprising a bearing substrate and an upper bearing portion disposed on said bearing substrate, said upper bearing portion including concavely curved side walls.  
         [0008]     According to certain embodiments, the bearing includes an upper bearing portion having curved side walls, a substantially curved upper bearing surface, and a flat seat region.  
         [0009]     In another embodiment, an expansion joint system is provided for a roadway construction wherein a gap is defined between adjacent first and second roadway sections, said expansion joint system extending across said gap to permit vehicular traffic, said expansion joint system comprising transversely extending, spaced-apart, vehicular load bearing members, elongated support members having opposite ends positioned below said transversely extending load bearing members and extending longitudinally across said expansion joint, means for movably engaging said longitudinally extending, elongated support members with at least one of said transversely extending, spaced-apart load bearing members, and bearing means disposed between lateral sides of said longitudinally extending elongated support members and surfaces of said means for movably engaging at least one of said longitudinally extending, elongated support members with said transversely extending, spaced-apart load bearing members, said bearing means comprising a bearing substrate and an upper bearing portion disposed on said bearing substrate, said upper bearing portion including concavely curved side walls.  
         [0010]     According to certain embodiments, the bearing includes an upper bearing portion having curved side walls, a substantially curved upper bearing surface, and a flat seat region.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is an exploded perspective view of the bearing structure.  
         [0012]      FIG. 2  is a side view of the bearing structure in an uncompressed state in the absence of a load.  
         [0013]      FIG. 3  is a side view of the bearing structure in a compressed state in response to the application of a load to the bearing.  
         [0014]      FIG. 4  shows a top perspective view of the expansion joint system including the bearing structure  
         [0015]      FIG. 5  is a side view of an illustrative support bar member.  
         [0016]      FIG. 6  is a rear view of the means for permitting transverse movement of the support bar members.  
         [0017]      FIG. 7  is a side view of an illustrative support bar member inserted into means for permitting transverse movement of the support bar member.  
         [0018]      FIG. 8A  is a side view of the means for permitting longitudinal and vertical movement of the support bar member.  
         [0019]      FIG. 8B  is an end view of the means for permitting longitudinal and vertical movement of the support bar member.  
         [0020]      FIG. 9A  is a side view of a portion of the expansion joint system including an end view of the yoke assembly for maintaining the support bar member in proximity to the bottom surfaces of the load bearing beams of the expansion joint system.  
         [0021]      FIG. 9B  is an enlarged fragmentary side view of a portion of the expansion joint system including an end view of the yoke assembly for maintaining the support bar member in proximity to the bottom surfaces of the load bearing beams of the expansion joint system. 
     
    
     DETAILED DESCRIPTION  
       [0022]     An improved bearing structure is provided. Without limitation, the bearing can be utilized in connection with an expansion joint system in roadway constructions, bridge constructions, tunnel constructions, and other constructions where gaps are formed between spaced-apart, adjacent concrete sections. The expansion joint system may be utilized where it is desirable to absorb loads applied to the expansion joint systems, and to accommodate movements that occur in the vicinity of the expansion joint gap in response to the application of the applied loads to the expansion joint system.  
         [0023]     The bearing structure includes a bearing substrate and an upper bearing portion that is disposed on, or otherwise fitted over, a portion of the bearing substrate. The upper bearing portion of the bearing includes curved side walls and a curved upper bearing surface.  
         [0024]     The bearing structure will now be described in greater detail with reference to the FIGURES. It should be noted that the bearing structure is not intended to be limited to the illustrative embodiments shown in the FIGURES.  
         [0025]      FIG. 1  shows an exploded side view of one embodiment of the bearing structure  10 . Bearing structure  10  comprises a substrate  11  that is manufactured from a resilient material. According to the embodiment shown in  FIG. 1 , bearing substrate  11  is shown having a substantially cylindrical shape. The bearing substrate  11  includes a top surface  12 , bottom surface  13 , and side walls  14  that extend between top surface  12  and bottom surface  13 .  
         [0026]     Bearing structure  10  also includes an upper bearing portion  15 . Upper bearing portion  15  includes a top bearing surface  16  and side walls  17  extending downwardly away from top bearing surface  16 . The side walls  17  of upper bearing portion  15  include oppositely facing inner  18  and outer  19  surfaces. The top bearing surface  16  and curved side walls  17 , together, form a cap-like structure having an inner volume  20 .  
         [0027]     Now turning to  FIG. 2 , the bearing structure  10  is shown with upper bearing portion  15  engaged with the bearing substrate  11 . Upper bearing portion  15  is engaged with bearing substrate  11  by disposing or otherwise fitting upper bearing portion  15  over a portion of bearing substrate  11 . The upper bearing portion  15  is fitted over the top surface  12  of bearing substrate  11 , and the side walls  17  of upper bearing portion  15  extend over a portion of the side walls  14  of the bearing substrate  11 .  
         [0028]     According to  FIG. 2 , the bearing structure  10  is shown under conditions where no force or load is applied to the top bearing surface  16  of the upper bearing portion  15  of the bearing  10 . The side walls  17  of the upper bearing portion  15  are constructed such that in the absence of a force or load on the upper bearing portion  15  the sides walls  17  of upper bearing portion  15  have a curved shape. That is, the side walls  17  of upper bearing portion  15  remain concavely curved and “bow in” toward the center of the upper bearing portion  15 . A portion of the upper bearing surface  16  includes a flat seat region. The flat seat region of upper bearing surface  16  may be centrally located.  
         [0029]     Turning to  FIG. 3 , the bearing structure  10  is shown under conditions where a force or load (F) is applied to the top bearing surface  16  of the upper bearing portion  15 . Under conditions where a force or load is applied to the upper bearing surface  16  of the bearing  10 , the side walls  17  of upper bearing portion  16  are urged downwardly along the outer surfaces of side walls  14  of bearing substrate  11  and upper bearing portion  16  moves into closer proximity with bearing substrate  11 . As upper bearing portion  15  is urged in a downward direction toward bearing substrate  11 , the shape of the side walls  17  of upper bearing portion  15  undergo a transition from being concavely curved toward the center of the upper bearing portion  15  to a vertical configuration. That is, as top bearing portion  15  is urged downwardly the side walls  17  change configuration from the concavely shaped side walls to a position that is perpendicular to the upper bearing surface  16  of upper bearing portion  15  and top surface  12  of bearing substrate  11 . When an out of level force or load is applied to upper bearing surface  16  at an angle, the upper bearing portion  15  of structural bearing  10  is able to transmit the vertical load such that the bottom surface of the bearing “feels” very minimal eccentricity.  
         [0030]     Distortional stresses in response to the application of a load to a traditional bearing structure often caused damage to the bearing structure. The use of the bearing structure  10  having concavely curved side walls  17  minimizes the distortional stresses below the bearing surface in response to the application of a force or load. The optimized geometric combination of curved side walls, curved top bearing surface, and flat seat region reduces local distortional stresses directly below the applied load, and moves the maximum distortional stress region to below the surface, based on the accepted principles of elasticity.  
         [0031]     It is known that prior art bearing structure stiffness remains nearly constant over the range of applications, as they are compressed in response to the application of a load to the bearing. The use of the bearing structure  10  having an upper bearing portion  15  with concavely curved side walls  17  provides an increasing force versus deflection spring rate. Utilizing the bearing structure  10  having an upper bearing portion  15  with curved side walls  17  permits the bearing structure to be precompressed to a significant degree, thereby mitigating bearing vibration when large vehicular impact loads are applied to the bearing. Additionally, the use of the bearing structure  10  having an upper bearing portion  15  with curved side walls  17  stabilizes large displacements in response to loads applied to the bearing  10 .  
         [0032]     In general, the top bearing surfaces of prior art bearings expand and contract against the support bar of the expansion joint systems in response to an application of a load, which causes significant rubbing and friction between the top bearing surfaces of the bearings and the surfaces of the support bar of the expansion joint systems. In contrast, upper bearing portion  15  of the bearing structure  10  expands upward to contact the surface of the support bar of the expansion joint systems. Under these conditions, less surface rubbing and friction occur between the top bearing surface  16  and the surface of the support bars of the expansion joint system. Because there is less friction between the top bearing surface  16  of the bearing  10  and the surfaces of the support bars, there is a significant decrease in the surface wear of the bearing  10 . Thus, the overall life of the bearing is increased.  
         [0033]     The side walls of the prior art bearings bulge outwardly upon an application of a load to the top bearing surface. These bearings, sometimes referred to as parabolic bulge bearings, are bonded on the top and bottom surfaces, and are free to bulge on their sides. These bearings produce very large surface shears at the point where the free edge of the bearing meets the bonded surfaces. In contrast to prior art parabolic bulge bearings, the side walls  17  of bearing  10  are constructed in such a manner that upon maximum compression by a load applied to the bearing, the side walls  17  of upper bearing portion  15  are vertical. This is a significant improvement over prior art parabolic bulge bearings, as shear strains at the point of the bond of the free edge to the bonded edge is minimized.  
         [0034]     An expansion joint system incorporating the improved structural bearing  10  is further provided. The expansion joint system may be utilized in a roadway construction wherein a gap is defined between adjacent first and second roadway sections. The expansion joint system extends across the gap between adjacent concrete roadway sections to permit vehicular traffic. The expansion joint system comprises transversely extending, spaced-apart, vehicular load bearing members. Elongated support members having opposite ends are positioned below the transversely extending load bearing members and extend longitudinally across the gap in the expansion joint from a first concrete roadway section to a second concrete roadway section. According to certain embodiments, the expansion joint system also includes first means for accepting first ends of the longitudinally extending elongated support members for controlling the movement of the ends of the support members within the first means for accepting longitudinally extending elongated support members, and second means for accepting opposite ends of the longitudinally extending elongated support members for controlling the movement of the opposite ends of said support members within the second means for accepting longitudinally extending elongated support members. Bearing structures  10  are disposed between sides surfaces of the opposite first and second ends of the longitudinally extending elongated support members and inner surfaces of the first and second means for accepting ends of the longitudinally extending elongated support members to absorb loads applied to the expansion joint system. The bearing structure includes a substrate and an upper bearing portion that is disposed on, or otherwise fitted over, the substrate. The upper bearing portion of the bearing comprises curved side walls and a curved upper bearing surface.  
         [0035]     According to other embodiments, the expansion joint system includes transversely extending, spaced-apart, vehicular load bearing members, elongated support members having opposite ends positioned below the transversely extending load bearing members and extending longitudinally across the expansion joint, and means for movably engaging the longitudinally extending, elongated support members with the transversely extending, spaced-apart load bearing members. Bearings  10  are disposed between surfaces of lateral sides of the longitudinally extending elongated support bar members and surfaces of the means for movably engaging the longitudinally extending, elongated support bar members with the transversely extending, spaced-apart load bearing members. The bearing structure  10  includes a substrate and an upper bearing portion that is disposed on, or otherwise fitted over, the substrate. The upper bearing portion of the bearing comprises curved side walls and a curved upper bearing surface.  
         [0036]     Now referring to illustrative  FIG. 4 , expansion joint system  30  includes a plurality of vehicular load bearing members  31 - 37 . The vehicular load bearing members  31 - 37  of expansion joint system  30  are positioned in the gap between the adjacent roadway sections (not shown). The vehicle load bearing members are often referred to in the art as “center beams.” While illustrative  FIG. 4  shows seven transversely extending load bearing members  31 - 37 , it should be noted that the expansion joint system  30  may include any number of transversely extending load bearing members, depending on the size of the gap of the particular construction. According to certain embodiments, the load bearing members have a generally square or rectangular cross section. Nevertheless, the load bearing members  31 - 37  are not limited to members having approximately square or rectangular cross sections, but, rather, the load bearing beam members  31 - 37  may comprise any number of cross sectional configurations or shapes. The shape of the cross section of load bearing beam members  31 - 37  is only limited in that the load bearing beams  31 - 37  must be capable of permitting relatively smooth and unimpeded vehicular traffic across the top surfaces of the load bearing beam members, and the load bearing beam members must have the ability to support engaging means that are engaged to the bottom surfaces of the load bearing beam members to engage the longitudinally extending elongated support members. According to certain embodiments, the top surfaces of the load bearing beam members may, for example, also be contoured to facilitate the removal of debris and liquids, such as rainwater runoff.  
         [0037]     The load bearing beam members  31 - 37  are positioned in a spaced apart, side-by-side relationship and extend transversely in the expansion joint gap relative to the direction of vehicle travel. That is, the load bearing members  31 - 37  extend substantially perpendicular, relative to the direction of vehicle travel across the expansion joint system  30 . The top surfaces of the load bearing beam members are adapted to support vehicle tires as a vehicle passes over the expansion joint. Compressible seals (not shown in  FIG. 1 , but shown in  FIG. 9 ) may be placed and extend transversely between the positioned vehicular load bearing beam members  31 - 37  adjacent the top surfaces of the beam members  31 - 37  to fill the spaces between the beam members  31 - 37 . The seals may also be placed and extend in the space between end beam member  31  and edge plate  38  and to extend between end beam member  37  and edge plate  39 . The seals are flexible and compressible and, therefore, can stretch and contract in response to movement of the load bearing beams within the expansion joint. The seals are preferably made from a durable and abrasion resistant elastomeric material. The seal members are not limited to any particular type of seal. Suitable sealing members that can be used include, but are not limited to, strip seals, glandular seals, and membrane seals.  
         [0038]     Still referring to  FIG. 4 , the expansion joint system  30  includes elongated support bar members  40 - 43 . Support bar members  40 - 43  are positioned in a spaced-apart, side-by-side relationship and extend longitudinally across the gap of the expansion joint, relative to the direction of the flow of vehicular traffic. That is, the support bar members  40 - 43  extend substantially parallel relative to the direction of vehicle travel across the expansion joint system  30 . The support bar members  40 - 43  provide support to the vehicle load bearing beams  31 - 37  as vehicular traffic passes over the expansion joint system  30 . Support bar members  40 - 43  also accommodate transverse, longitudinal and vertical movement of the expansion joint system  30  within the gap.  
         [0039]     Opposite ends of the support bar members  40 - 43  are received into suitable means for accepting the ends of the support bar members, and several means for accepting the support bar members are disposed, or embedded in portions of respective adjacent roadway sections in the roadway construction. The expansion joint system  30  can be affixed within the “block-out” areas between two adjacent roadway sections by disposing the system  30  into the gap between the roadway sections and pouring concrete into the block-out portions or by mechanically affixing the expansion joint system  30  in the gap to underlying structural support. Mechanical attachment may be accomplished, for example, by bolting or welding the expansion joint system  30  to the underlying structural support.  
         [0040]     In accordance with the invention, provision is made for particular types of movement of the support bar members  40 - 43  within the separate means for accepting the ends of the support bar members. In one embodiment, the means for accepting the ends of the support bar members comprise box-like structures. It should be noted, however, that the means for accepting the ends of the support bar members may include any structure such as, for example, receptacles, chambers, housings, containers, enclosures, channels, tracks, slots, grooves or passages, that includes a suitable cavity for accepting opposite end portions of the support bar members  40 - 43 .  
         [0041]     Still referring to  FIG. 4 , the expansion joint system  30  includes first means  50  for confining the first ends of the support bars  40 - 43  against longitudinal movement within the first means  50  for accepting, but permitting transverse movement of the first ends within the first means  50  for accepting. Therefore, the expansion joint system  30  includes first means for accepting first ends of the longitudinally extending elongated support members which include means for substantially restricting longitudinal movement within the first means for accepting, but permitting transverse and vertical movement within said first means for accepting.  
         [0042]     The expansion joint system  30  includes second means  51  for accepting opposite ends of the support members  40 - 43  for confining the opposite ends of the support bars  40 - 43  against transverse movement within the second means  51  for accepting, but permitting longitudinal movement and vertical movement within the second means  51  for accepting. Therefore, the expansion joint system  30  includes second means for accepting ends of said longitudinally extending elongated support members which includes means for substantially restricting transverse movement within said second means for accepting, but permitting longitudinal movement within said second means for accepting.  
         [0043]      FIG. 5  shows an illustrative support member  60  of the expansion joint system  30 . The support member  60  is shown as an elongated bar-like member having a square cross section. It should be noted, however, that the support member  60  is not limited to elongated bar members having square cross sections, but, rather, the support member  60  may comprise an elongated bar member having a number of different cross sectional shapes such as, for example, round, oval, oblong and rectangular. The support bar  60  includes opposite ends  61 ,  62 . Illustrative support bar  60  includes a hole  63  communicating from one side  64  of the support bar  60  to the other side  65 . According to this embodiment, the hole  63  is adapted to receive a securing means. End  62  of the support bar  60  having the hole  63  therein is adapted to be inserted into first means  50  for permitting transverse and vertical movement, but substantially restricting longitudinal movement of the support member  60  of the expansion joint system  30  within the means  50 .  
         [0044]      FIG. 6  shows a side view of means  50 , which according to the embodiment shown is a substantially rectangular box structure, and which permits transverse and vertical movement of support bars  40 - 43  of the expansion joint system  30  in response to movement within the expansion joint. The transverse and vertical movement box  50  includes top  52  and bottom  53  plates, side plates  54 ,  55  and back plate (not shown). According to this embodiment, the securing means  56  is an elongated, substantially cylindrical guide rod to which a support bar  40 - 43  is engaged. The securing means  56  is substantially centrally disposed within box  50  may extend across box  50  from side plate  54  to side plate  55 . The securing means  56  may be held in place by holding plates  57 ,  58 , which are attached to the inside wall surfaces  59   a ,  59   b  of side plate  54  and side plate  55 , respectively. The securing means  56  is inserted into the hole  63  in order to secure the support bar  40 - 43  within means  50 . The securement means  56  can be any means which permits pivotable movement of end  62  of the support bar in the vertical direction within means  50 , while further permitting transverse movement of end  62  of the support bar along the axis of the securement means. Thus, the securing means  56  substantially restricts longitudinal movement of the support bars  40 - 43 , but permits transverse and vertical movement. While the securing means  56  is shown in  FIG. 6  as a cylindrical guide rod, it may, for example, include differently shaped rods, bars, pegs, pins, bolts, and the like.  
         [0045]      FIG. 7  shows one end  62  of the support bar  60  inserted into means  50 . Bearing means  10  are disposed between the top surface of support bar member  60  and the inner surface  52   a  of top plate  52  of box  50  and between the bottom surface of the support bar member  60  and the inner surface  53   a  of bottom plate  53 . The rigid bearing substrate  11  of bearing structure is positioned adjacent to inside surface  52   a  of top plate  52  and top bearing surface  16  of upper bearing portion  15  may contact top surface of support bar member  60 . A second bearing means  10  is positioned within box  50 . The rigid bearing substrate  11  of the second bearing structure is positioned adjacent to inside surface  53   a  of bottom plate  53  and top bearing surface  16  of upper bearing portion  15  may contact bottom surface  64  of support bar member  60 .  
         [0046]      FIGS. 8A and 8B  shows longitudinal movement support box  51 . Box  51  includes means for permitting longitudinal and vertical movement of the support bars  40 - 43  within box  51 , and means for substantially preventing transverse movement of support bars  40 - 43  within the box  51 . Preferably, the upper  71  and lower  72  bearing means maintain the vertical load on the support bars perpendicular to the axis of the support bars and, permits slidable movement of the support bars in the direction of vehicular traffic flow (longitudinal movement). Upper and lower bearing means  71 , 72  are the constructed like bearing structure  10  described in  FIGS. 1-3 . As shown in  FIG. 8B , side bearing means  73 ,  74  substantially prevent transverse movement of support bars  40 - 43  within box  51 , while not inhibiting or otherwise preventing longitudinal and vertical movement. According to the embodiment shown, side bearing means  73 ,  74  are provided in the form of bearing plates that are disposed adjacent the inner surfaces of box  51 .  
         [0047]     The use of the upper  71  and lower  72  bearings maintain the vertical load on the bearings perpendicular to the sliding surfaces. The upper and lower bearings are capable of absorbing impact from vehicular traffic moving across the expansion joint system.  
         [0048]     The transverse movement box for receiving one end of the support bars is designed to permit transverse and vertical movement of the support bars within the boxes in response to changes in temperature changes, seismic movement or deflections caused by vehicular traffic, while restricting longitudinal movement. Longitudinal boxes for receiving the opposite ends of the support bars are designed to permit relative longitudinal and vertical movement of the support bar within the boxes, while confining the bars against relative transverse movement.  
         [0049]     Means are provided to maintain the position of support bars  40 - 43  relative to the bottom surfaces of the load bearing beams members  31 - 37 . Also, the means permit longitudinal and limited vertical movement of the support bars  40 - 43  within the means.  FIGS. 9A and 9B  show one embodiment of the means, which comprises a yoke or stirrup assembly  80  for retaining the position of the support bars  40 - 43  relative to the bottom surfaces of the load bearing beams  31 - 37  of the expansion joint system  30 . As shown in  FIG. 9B , the yoke assembly  80  includes spaced-apart yoke side plates  81 ,  82  that are attached to and extend away from the bottom surface of the vehicular load bearing beam  31 . Bent yoke plate  83  includes leg portions  84 ,  85  and spanning portion  86  that extends between legs  84 ,  85 . The yoke assembly  80  also includes upper yoke bearing  87  and lower yoke bearing  88 . The yoke assembly  80  utilizes upper  87  and lower  88  yoke bearings to minimize yoke tilt and optimizes the ability of the expansion joint system  30  to absorb vehicular impact from traffic moving across the expansion joint system  30 . While the one embodiment is shown utilizing a yoke or stirrup assembly to maintain the positioning of the support bars  40 - 43 , any restraining device or the like that can maintain the position of the support bars  40 - 43  relative to the load bearing beams  31 - 37  may be utilized.  
         [0050]     Yoke assembly  80  may further include yoke retaining rings  90 ,  91  and yoke discs  92 ,  93 , which are located on the inner surfaces of bent yoke legs  74 ,  75 . The yoke retaining rings  81 ,  82  and yoke discs  83 ,  84  are provided to allow limited vertical and longitudinal movement of the support bars  40 - 43 . Furthermore, the yoke side plates  81 ,  82  are spaced apart at a distance sufficient to permit bent yoke plate  83  to be inserted in the space defined by the inner surfaces of yoke side plates  81 ,  82 .  
         [0051]     The expansion joint system  30  may also include means for controlling the spacing between the transversely extending load bearing beam members  31 - 37  in response to movement in the vicinity of the expansion joint. In one embodiment, the means for controlling the spacing between beam members  31 - 37  maintains a substantially equal distance between the spaced-apart, traffic load bearing beams  31 - 37  that are transversely positioned within the gap in an expansion joint, in response to movements caused by thermal or seismic cycling and vehicle deflections.  
         [0052]     The expansion joint system of the invention is used in the gap between adjacent concrete roadway sections. The concrete is typically poured into the blockout portions of adjacent roadway sections. The gap is provided between first and second roadway sections to accommodate expansion and contraction due to thermal fluctuations and seismic cycling. The expansion joint system can be affixed within the block-out portions between two roadway sections by disposing the system into the gap between the roadway sections and pouring concrete into the block-out portions or by mechanically affixing the expansion joint system in the gap to underlying structural support. Mechanical attachment may be accomplished, for example, by bolting or welding the expansion joint system to the underlying structural support.  
         [0053]     While the present invention has been described above in connection with the preferred embodiments, as shown in the various figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiments for performing the same function of the present invention without deviating therefrom. Further, all embodiments disclosed are not necessarily in the alternative, as various embodiments of the invention may be combined to provide the desired characteristics. Variations can be made by one having ordinary skill in the art without departing from the spirit and scope of the invention. Therefore, the present invention should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the recitation of the attached claims.