Patent Publication Number: US-8522381-B1

Title: System and method for bridge pier replacement

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of priority under 35 U.S.C. Section 119(e) to U.S. Provisional Application Ser. No. 61/380,670, filed Sep. 7, 2010, entitled “SYSTEM AND METHOD FOR BRIDGE PIER REPLACEMENT,” which is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a system and method for replacing existing deteriorated piers of bridges which carry railroad or other types of traffic without interruption to traffic flow or temporary intermediate piers. 
     2. Description of the Related Art 
     Typical railroad or other type bridge construction involves the use of bridge girders, which are oriented in the general direction of the axis of the railroad or road which is supported by the bridge. The bridge girders are typically supported at each end by a pier, which provides support into the earth for the bridge and the applied load. The existing bridge piers are generally constructed of reinforced concrete, masonry, structural steel, or a combination thereof, often comprising two or more columns or column-like members connected at their top-most ends by a cap, strut, or other member holding them in their correct positions. Conventional methods for replacing existing deteriorated piers of bridges require the interruption to traffic flow. 
     SUMMARY OF THE INVENTION 
     The system and method of the present invention comprises installing new drilled shaft columns outside (wider than) the existing pier or bent. Integral to these columns will be support brackets or embedded support beams. Temporary girders are installed on these support brackets or beams, and the load is transferred from the existing bent to the temporary transverse girders. With the bridge girders supported by the temporary transverse girders, the existing deteriorated bent can be removed, and a new cast in place pier cap can be constructed on the new drilled shaft columns. The load can then be transferred to the new cap and the temporary support brackets or beams and transverse girders can be removed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of one embodiment of the present invention prior to the installation of the new pier cap. 
         FIG. 2  is an overhead plan view of one embodiment of the present invention illustrating the new pier cap in place. 
         FIG. 3  is a side view of one embodiment of the present invention with the new pier cap in place. 
         FIG. 4  is a cross-sectional view of a new support column illustrating the temporary support brackets attached to the column using tension rods and shear keys. 
         FIG. 5  is a cross-sectional view of another embodiment of the present invention prior to the installation of the new pier cap. 
         FIG. 6  is an overhead plan view of another embodiment of the present invention illustrating the new pier cap in place. 
         FIG. 7  is a side view of another embodiment of the present invention with the new pier cap in place. 
         FIG. 8  is a cross-sectional view of a new support column of another embodiment of the present invention illustrating the temporary support beam embedded in the column. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As illustrated in  FIG. 1 , a typical railroad or other type bridge construction involves the use of bridge girders  20 , which are oriented in the general direction of the axis of the railroad or road which is supported by the bridge. The bridge girders are typically supported at each end by a pier or bent  22  which provides support into the earth for the bridge and the applied load. The bridge piers  22  are generally are constructed of reinforced concrete, often comprising two or more columns or column-like members connected at their top most ends by a cap, strut, or other member holding them in their correct positions. The pier or capping structure  22  will often have an elongated rectangular footprint with the long axis of the footprint oriented transverse to the axis of the bridge girders  20 . When a bridge pier  22  becomes deteriorated to the point that it is no longer serviceable, in order to maintain the integrity and use of the bridge structure, it is desirable to provide a replacement support structure without interruption of the use of the bridge structure. 
     As illustrated in  FIGS. 1 ,  3  and  4 , in one embodiment, the present method and system preferably involves the installation of new permanent drilled shaft columns  24  preferably of a round configuration, outside of the existing pier  22 , preferably one at each end of the pier  22  with centerlines oriented along the pier footprint axis, transverse to the axis of the bridge girders  20 . Once the new drill shaft columns  24  are installed, they are each fitted with at least one temporary support bracket  26  which preferably extends from each new support column  24  in a direction along the bridge girder axis. 
     As illustrated in  FIG. 4 , the temporary support brackets  26  may be attached to the new support column  24  using tension rods  36 , shear keys  38  embedded in the new support column  24 , or a combination of tension rods and shear keys. As is known by those of ordinary skill in the art, tension rods  36  may be installed through the column  24  as illustrated in  FIG. 4 , or, alternatively, tension rods  36  may be tied to a nut embedded in the new support column  24 . 
     As illustrated in  FIGS. 1 and 3 , the temporary support brackets  26  are configured to receive and support a temporary girder  28 , which spans between the temporary support brackets  26  on both of the new drilled shaft columns  24  along an axis transverse to the axis of the bridge girders  20 . 
     As illustrated in  FIGS. 1 and 3 , a temporary support post  30  may be installed on the upper surface of the temporary girder  28  underneath each existing bridge girder  20 , to provide support for the existing bridge girders  20  at a point on the girder inside from the point where the deteriorated pier  22  currently supports the girder  20 . In this manner, the temporary support post  30  or other suitable supporting device may be jacked into position in order to transfer the load from the deteriorated pier  22  to the transverse girders  28  supported by the temporary support brackets  26  on the new support columns  24 . The existing bridge girder  20  may be fitted with a temporary bearing stiffener  32  to provide local reinforcement of the bridge girder  20  to adequately transfer the bridge load to the temporary support post  30 . 
     As illustrated in  FIGS. 1 and 3 , this arrangement allows the load on the bridge girder  20  to be adequately supported by the temporary support post  30  and transverse girder  28  such that the upper portion of the existing pier  22  may be removed to allow the installation of a new cast in place concrete pier cap  34  or replacement of the deteriorated portion of the pier, while the continued existing use of the bridge structure is maintained. 
     As illustrated in  FIGS. 1 ,  2  and  3 , once the bridge girder  20  is supported by the temporary support post  30  and transverse girder  28 , the new support columns  24  may be fitted with a new cast in place concrete cap  34 , which extends between the columns  24  over the area previously supported by the deteriorated pier  22  such that the new columns  24  and cap  34  may replace the load bearing function for the bridge girder  20  of the deteriorated pier at the same location on the bridge girder  20 . The new pier cap  34  is of sufficient dimensions and materials to provide support between the new columns  24  such that even in the absence of any support from the deteriorated pier  22 , the bridge will be supported. The new pier cap  34  is installed in substantially the same location and above the deteriorated pier  22  so that the original support locations on the bridge girders  20  are employed. Once the cap  34  has attained adequate strength, the bridge load from the bridge girders  20  may be transferred from the temporary support post  30  and transverse girder  28  to the new concrete cap  34 . Then, if desired, the temporary support brackets  26 , temporary support posts  30  and transverse girders  28  may be removed. 
     As is known and appreciated by those of ordinary skill in the art, other suitable structures may be used in place of a pier cap for spanning between the new columns  24  for supporting the bridge girders  20 , including structural steel beams, girders, or trusses. 
     In summary, a detailed description of the steps of a method of employing one embodiment of the preferred invention is as follows:
         Install one or more, preferably round drilled shaft columns in the earth on opposite sides of the existing pier to be replaced transverse to the axis of the bridge girder.   Install at least one temporary support bracket on each of the new columns.   Install a temporary transverse girder onto the support brackets of two or more columns.   Install temporary support posts on the transverse girder.   Once the columns have attained adequate strength, transfer the load from existing deteriorated pier to the temporary transverse girder using the temporary support post.   Remove the existing pier or bent down to an elevation as necessary to allow installation of a new cast in place cap.   Construct a new cast in place cap.   Once the cap has attained adequate strength, transfer the load from the temporary transverse girders and temporary support posts to the new cast in place concrete cap.   Remove the temporary transverse girder, temporary support posts and temporary support brackets.       

     As illustrated in  FIGS. 5 ,  7  and  8 , in another embodiment, the present method and system preferably involves the installation of new permanent drilled shaft columns  24  preferably of a round configuration, outside of the existing pier  22 , preferably one at each end of the pier  22  with centerlines oriented along the pier footprint axis, transverse to the axis of the bridge girders  20 . When the new drill shaft columns  24  are formed, at least one temporary support beam  40  is embedded through each new support column  24  oriented in a direction along the bridge girder axis. 
     As illustrated in  FIGS. 5 and 7 , the temporary support beams  40  are configured to receive and support a temporary girder  28 , which spans between the temporary support beams  40  on both of the new drilled shaft columns  24  along an axis transverse to the axis of the bridge girders  20 . 
     As illustrated in  FIGS. 5 and 7 , a temporary support post  30  may be installed on the upper surface of the temporary girder  28  underneath each existing bridge girder  20 , to provide support for the existing bridge girders  20  at a point on the girder inside from the point where the deteriorated pier  22  currently supports the girder  20 . In this manner, the temporary support post  30  or other suitable supporting device may be jacked into position in order to transfer the load from the deteriorated pier  22  to the transverse girders  28  supported by the temporary support beams  40  on the new support columns  24 . The existing bridge girder  20  may be fitted with a temporary bearing stiffener  32  to provide local reinforcement of the bridge girder  20  to adequately transfer the bridge load to the temporary support post  30 . 
     As illustrated in  FIGS. 5 and 7 , this arrangement allows the load on the bridge girder  20  to be adequately supported by the temporary support post  30  and transverse girder  28  such that the upper portion of the existing pier  22  may be removed to allow the installation of a new cast in place concrete pier cap  34  or replacement of the deteriorated portion of the pier, while the continued existing use of the bridge structure is maintained. 
     As illustrated in  FIGS. 5 ,  6  and  7 , once the bridge girder  20  is supported by the temporary support post  30  and transverse girder  28 , the new support columns  24  may be fitted with a new cast in place concrete cap  34 , which extends between the columns  24  over the area previously supported by the deteriorated pier  22  such that the new columns  24  and cap  34  may replace the load bearing function for the bridge girder  20  of the deteriorated pier at the same location on the bridge girder  20 . The new pier cap  34  is of sufficient dimensions and materials to provide support between the new columns  24  such that even in the absence of any support from the deteriorated pier  22 , the bridge will be supported. The new pier cap  34  is installed in substantially the same location and above the deteriorated pier  22  so that the original support locations on the bridge girders  20  are employed. Once the cap  34  has attained adequate strength, the bridge load from the bridge girders  20  may be transferred from the temporary support post  30  and transverse girder  28  to the new concrete cap  34 . Then, if desired, the temporary support posts  30  and transverse girders  28  may be removed. 
     Additionally, as illustrated in  FIG. 8 , the portions of the temporary support beam  40  that extend beyond the face of column  24  may be removed. Optionally, a blockout  42  may be formed in column  24  to a depth of approximately 2 inches to facilitate removal of a portion of the embedded temporary support beam  40  below the face of column  24 . After removal of the portion of the embedded temporary support beam  40  from within blockout  42 , the resulting void in blockout  42  may be filled in with grout or other suitable material to produce a uniform surface on the face of column  24 . 
     In summary, a detailed description of the steps of a method of employing such another embodiment of the preferred invention is as follows:
         Install one or more, preferably round drilled shaft, columns in the earth on opposite sides of the existing pier to be replaced transverse to the axis of the bridge girder, each column having a support beam cast-through it.   Install a temporary transverse girder onto the support beams of two or more columns.   Install a temporary support post on the transverse girder.   Once the columns have attained adequate strength, transfer the load from existing deteriorated pier to the temporary transverse girder using the temporary support post.   Remove the existing pier or bent down to an elevation as necessary to allow installation of a new cast in place cap.   Construct a new cast in place cap.   Once the cap has attained adequate strength, transfer the load from the temporary transverse girders and temporary support posts to the new cast in place concrete cap.   Remove the temporary transverse girder and temporary support posts.   Remove the portions of the support beam that extend beyond column face and within the blockout.       

     These examples are provided for the purposes of illustration and the present invention is not limited to them.