Patent Publication Number: US-2007098503-A1

Title: Precast concrete bridge assembly

Description:
Background of the Invention  
      The present invention relates to precast concrete culvert or bridge assemblies or systems such as disclosed in U.S. Pat. Nos. 4,993,872 and 6,854,928 which issued to the assignee of the present invention and the disclosures of which are herein incorporated by reference. In a culvert or bridge assembly as disclosed in the &#39;872 Patent, a plurality of one-piece and open bottom culvert or bridge units or sections are precasted of concrete with reinforcement and include parallel spaced side walls integrally connected by an arcuate top wall. Curved surfaces connect the inner surface of the arcuate top wall to the opposing inner surfaces of the side walls, and the outer surface of the top wall form angular corners with the outer vertical surfaces of the side walls. The construction of an open bottom precast concrete culvert or bridge section as disclosed in the above &#39;872 Patent is satisfactory and usable up to a span between the side walls of about forty eight feet. However, it has been found that there is a need for one-piece open bottom precast concrete bridge sections each having a span significantly above forty-eight feet, for example, a span of sixty feet.  
     Summary of the Invention  
      The present invention is directed to an improved precast concrete bridge assembly and which is formed by a plurality of one-piece precast concrete bridge sections each having a span greater than fifty feet and capable of supporting the substantial loads of the compacted soil surrounding the bridge assembly as well as the loads of a roadway extending above the bridge assembly and the motor vehicle traffic on the roadway. In accordance with one embodiment of the invention, each of the precast reinforced concrete bridge units or sections includes parallel spaced side walls integrally connected by an arcuate top wall, and the opposing inner surfaces of the side walls define a span between fifty and seventy-five feet. The arcuate top wall of each section has a radius of curvature between sixty-five and eighty feet, and the rise between the bottom surfaces of the side walls and the inner top surface of the top wall is between ten and fourteen feet. The substantially vertical outer surfaces of the side walls have a height between five and nine feet, and curved surfaces connect the inner surfaces of the side and top walls and have a radius of curvature between five and seven feet.  
      Other structural features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of a precast concrete bridge assembly constructed in accordance with the invention and with intermediate bridge sections removed to illustrate an indefinite length for the assembly; and  
       FIG. 2  is an end view of each bridge section shown in  FIG. 1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring to  FIG. 1 , a precast concrete bridge assembly  10  includes a plurality of aligned open bottom precast concrete bridge units or sections  15  each of which is reinforced, for example, by steel rebars and/or steel mesh as disclosed in above-mentioned U.S. Pat. No. 4,993,872. Each of the one-piece bridge sections  15  includes parallel spaced side walls  18  having substantially vertical outer surfaces  17  and inner surfaces  19 , and the side walls are integrally connected by an arcuate top wall  20 . The span S ( FIG. 2 ) define between the inner surfaces  19  of the side walls  18  is greater than fifty feet and less than seventy-five feet, for example, fifty-four feet or sixty feet. The rise R of each bridge section  15 , as defined between the bottom surfaces of the side walls  18  and the top of an inner surface  22  of the top wall  20  is greater than ten feet and less than fourteen feet, for example, about eleven feet for a span S of fifty-four feet and about twelve feet for a span S of sixty feet. The height H of the outer surface  17  of each side wall is within the range of five feet and nine feet, for example, six feet.  
      The inner surface  22  of the arcuate top wall  20  of the bridge section  15  has a radius of curvature R 1  which is greater than sixty five feet and less than eighty feet, for example, on the order of seventy feet. The thickness T 1  of the central portion of the top wall  20  is greater than twelve inches and preferably greater than thirteen inches and less than sixteen inches, for example, fourteen inches. The arcuate top surface  23  of the top wall  20  continues with a substantially uniform radius on each side of a center reference plane P and through an angle A of about twenty-four degrees and then continues with an outer flat surface  26  having a length L 2  of about three and one half feet.  
      The radius R 1  of the inner surface  22  of the top wall  20  is uniform through an angle B of about seventeen degrees on each side of the center plane P and then continues with a smaller radius of curvature R 3 , for example, thirty-three feet, through an angle C of about twelve degrees. The inner surface  19  of each side wall  18  connects with the inner surface  22  at the top wall  20  by a curved surface  28  having a radius of curvature R 2  greater than five feet and less than seven feet, for example, six feet. The radius R 2  extends through an angle D of about sixty degrees to form a corner thickness T 3  of about three feet. The lower portions of the side walls  18  have a thickness T between fifteen and nineteen inches, for example, on the order of sixteen inches to eighteen inches, and the surface  26  at each end of the top wall  20  forms a corner angle E of about  113  degrees with the outer surface  17  of the corresponding side wall  18 . The length L ( FIG. 1 ) of each bridge section  15  is on the order of four feet.  
      From the above dimensions and range of dimensions for each bridge section  15 , it is apparent that the radius R 1  of the arcuate top wall  20  is at least five times the rise R, at least seven times the height H of the side walls  18  and at least eleven times the radius R 2  of the inner curved surface  28 . By constructing each underground bridge section  15  with the configuration shown in  FIGS. 1 &amp; 2  and with the angles and dimensions within the ranges set forth above, it has been found that the bridge assembly  10  provides not only for supporting the compacted soil back-filled around the bridge assembly, but also provides for a distinctive and aesthetically pleasing appearance.  
      While the form and profile of the bridge assembly herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form and profile and that changes may be made therein without departing from the scope and spirit of the invention as defined in the appended claims.