Abstract:
A bridge approach, abutment construction and road widening technique and method using tilt-up panels and lightweight concrete fill is disclosed. A bridge approach ramp is constructed using tilt-up panels, initially supported using tilt form braces, to from a retaining wall perimeter, and subsequently filling the interior with sequential pours of lightweight concrete. The present invention advances the art of bridge construction by providing an improved bridge approach structure that is capable of rapid construction and provides an improved and cost effective structure as compared with prior art teachings.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of provisional U.S. Patent Application Ser. No. 61/220,297, filed on Jun. 25, 2009. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    N/A 
       COPYRIGHT NOTICE 
       [0003]    A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyrights rights whatsoever. 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    The present invention relates generally to the construction of road bridges and more particularly to the construction of bridge abutments and approaches. 
         [0006]    2. Description of the Background Art 
         [0007]    Bridges have become a necessity in today&#39;s industrial age to span valleys, rivers, roadways in order to make transportation more efficient. Most small-spanned bridges are constructed of either precast concrete or concrete that is poured on site. Typically concrete bridges involve abutments constructed using load bearing columns on both sides of a span. The bridge deck is then laid horizontally across the span, the weight of which is supported by the columns. The side walls of the abutments and the bridge approaches are typically constructed of concrete slabs which are either driven into the ground using pilings or stabilized using a large footing. Alternate construction methods include temporary wire walls, sheet piling, embankment, cast-in-place (cip), or mechanically stabilized earth (mes). The side walls of the abutments support the vertical load of the bridge deck as well as the lateral load of the earth which is retained on one side of the wall. A problem which is often encountered by this arrangement is that the load bearing walls must be very thick, require a large footing, or in rare circumstances, must be driven deep into the ground in order to support and hold back the large lateral load of the earthen fill. These requirements increase exponentially as the height of the wall increases. 
         [0008]    Retaining wall structures are often used along the bridge approach. The walls are often comprised of a large slabs or precast blocks which are stacked vertically. Earthen fill is then loaded behind the wall until the desired height of the roadway is reached. Common types of these retaining walls include gravity walls, piling walls, cantilever walls, and anchored walls. The following U.S. Patents disclose the use of facing blocks which are vertically stacked to construct the wall: U.S. Pat. Nos. 3,981,038; 4,045,965; 5,131,791; 5,178,493; and Published U.S. Patent Application 2002/0031406. In U.S. Pat. No. 5,131,791 the blocks are designed so that they can be interlocked with each other. In US APP  2002 / 0031406  the blocks are affixed to each other using reinforcement steel. A common characteristic in all of these inventions is that the backfill behind the walls, which provides a support surface for the roadway, is earthen fill. The backfill is usually an aggregate of soil and gravel which causes it to exert a large lateral earth pressure on the wall. Often referred to as the active and passive pressure on the wall, these forces increase significantly in relation to the density and angle of friction of the backfill material. 
         [0009]    Tilt-up construction, sometimes referred to as tilt-wall construction, is well known in the art for use in constructing buildings. Tilt-up construction generally involves the pre-casting of modular elements (i.e. walls, columns, structural supports, etc.) then raising the element vertically (e.g. by upward tilting) into place using a crane. Once raised the elements, such as walls, are braced to the ground using a tilt-form brace so as to be able to stand freely. Modular elements are attached to other modular elements to form a desired structural configuration. Tilt-up construction is relatively inexpensive and less time consuming when compared to other building construction methods. However, tilt-up construction has been largely limited to in application to building construction because the design of the tilt wall slab only allows it to support a large vertical load and a relatively small lateral load. 
         [0010]    Accordingly, there exists the need for bridge components which require minimal construction time and effort without compromising strength. In addition, there exists the need for a bridge abutment, approach ramp, and bridge widening construction technique that is stronger and more durable than conventional abutments, approaches or widening. It is, therefore, to the effective resolution of the aforementioned problems and shortcomings of the prior art that the present invention is directed. In view of the bridge abutments and approaches and methods of construction of said components in existence at the time of the present invention, it was not obvious to those persons of ordinary skill in the pertinent art as to how the identified needs could be fulfilled in an advantageous manner. The instant invention addresses this unfulfilled need in the prior art by providing a bridge approach and abutment structure as disclosed herein. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention is directed to a bridge approach and abutment construction and method using tilt-up panels and lightweight concrete fill. In accordance with the present invention a bridge approach ramp is constructed using tilt-up panels, initially supported using tilt form braces, to from a retaining wall perimeter, and subsequently filling the interior thereof with sequentially poured layers of lightweight concrete. The present invention advances the art of bridge construction by providing an improved bridge approach structure that is capable of rapid construction and provides an improved and cost effective structure as compared with prior art teachings. 
         [0012]    Accordingly, it is an object of this invention to provide a method of constructing a bridge approach and abutment structure using modular tilt-up elements. 
         [0013]    Another aspect of the present invention is to provide a method of constructing a bridge approach and abutment structure using modular tilt-up elements and a lightweight concrete fill. 
         [0014]    It is also an object of this invention to provide an easy and less time-consuming method for producing a bridge approach and abutment. 
         [0015]    It is also an object of this invention to provide a bridge abutment and approach that allows for a reduction in materials, the use of heavy equipment, reduction in carbon emissions, traffic, exposure, and construction time, thereby significantly reducing related costs. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0016]    Preferred embodiments of the invention will now be described in further detail. Other features, aspects, and advantages of the present invention will become better understood with regard to the following detailed description and accompanying drawings (which are not to scale) where: 
           [0017]      FIG. 1  is a partial perspective cut-away view depicting portions of an anterior wall and wing wall for a bridge approach and abutment generally constructed in accordance with the present invention; 
           [0018]      FIG. 2  is a panel layout plan view depicting the anterior wall and wing walls of a bridge approach and abutment construction in accordance with the present invention; 
           [0019]      FIG. 3  is a cross-sectional elevation view illustrating the layers of engineered fill material contained within the anterior wall and wing wall structure taken along line  3 - 3  in  FIG. 1 ; 
           [0020]      FIG. 4  is a cross-sectional side elevation view of a bridge abutment construction in accordance with the present invention; 
           [0021]      FIG. 5  is a cross-sectional side elevation view of a bridge approach ramp construction in accordance with the present invention; and 
           [0022]      FIG. 6  is an enlarged cross-sectional side elevation view of a bridge approach ramp construction or road widening in accordance with the present invention. 
       
    
    
       [0023]    A better understanding of the invention will be obtained from the following detailed description of the preferred embodiments taken in conjunction with the drawings and the attached claims. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    With reference now to the drawings,  FIGS. 1-6  depict a preferred embodiment of a bridge approach and abutment construction in accordance with the present invention. The construction structure and methods disclosed herein are particularly suited for the construction of bridge approaches and abutment structures, but also suitable for bridge widening and road widening projects. The construction and method involves the use of tilt-up panels, initially supported using tilt form braces, to from a retaining wall perimeter that is subsequently filled with sequentially poured layers of lightweight concrete. Each tilt-u 
         [0025]      FIG. 1  is a perspective view depicting a bridge approach and abutment construction, generally referenced as  10 , in accordance with the present invention.  FIG. 2  depicts a plan view of a tilt-up panel peripheral retaining wall structure of a bridge approach and abutment construction in accordance with the present invention. The retaining wall structure includes an anterior wall, generally referenced as  12 , and opposing wing walls, generally referenced as  14  and  16 . A first aspect of the present invention involves constructing walls  12 ,  14 , and  16  using a plurality of pre-cast, tilt-up wall panels (a/k/a tilt-wall panels). Each wall panel comprising a pre-cast monolithic structure having a top edge, a bottom edge, and opposing side edges running between said top and bottom edges. In the example depicted in  FIG. 2 , anterior wall  12  is formed by nine (9) panels, referenced as  12   a - 12   i , and opposing wing walls  14  and  16  are each formed by twenty (20) panels, referenced as  14   a - 14   t  (and  16   a - 16   t ). Each wall panel is preferably fabricated to a standard width dimension (e.g. 24.0 feet), and terminates at a top edge at a predetermined height and slope depending on the approach dimensions at the location wherein each panel will be erected. As more fully discussed herein, walls  12 ,  14 , and  16  are generally erected using conventional tilt-up fabrication and bracing techniques such that the panels are set in generally vertically disposed, side-by-side relation. The tilt-wall panels  12 ,  14 , and  16  may be cast on site, or pre-cast off-site and shipped to the site. The tilt-wall panels  12  are hoisted into place by a crane or some other construction mechanism Once the retaining wall structure is formed it is back filled in accordance with a second aspect of the present invention. The top surface of the fill is represented reference numeral  20  in  FIG. 2 . 
         [0026]    With reference to  FIG. 3 , there is a cross-sectional elevation view of the fill structure, generally referenced as  20 , contained within the retaining wall structure formed by anterior wall  12  and wing walls  14  and  16 . A significant aspect of the present invention involves the use of a lightweight fill material, in lieu of conventional earthen fill. In accordance with this aspect of the present invention, an Engineered Fill (hereinafter “EF”) comprising a lightweight cellular concrete is used as the fill material. EF, which is sometimes referred to as foam concrete, consists generally of Portland Cement, water, foaming agent, and compressed air. The mix may comprise other additives such as fly ash and fibers in order to customize the fill to a desired compressive or flexural strength, or density. EF is a relatively lightweight construction material due to the trapping of air bubbles within the concrete. As a result the fill structure comprised of Engineered Fill weighs significantly less than a fill structure comprised of conventional earthen fill. Accordingly, the stress placed on the anterior wall and wing walls is significantly reduced. 
         [0027]    As illustrated in  FIG. 3 , the EF fill structure  20  is poured in layers, referenced as  20   a - 20   h . Once a layer has cured, the next layer is poured on top. Additional pour layers may be poured until a desired height is reached. In the preferred embodiment, each pour layer has a depth of approximately 3.0 feet. A 3.0 ft. pour depth has been found to be suitable due to the fact that the pre-cured EF mixture is formed with compressed air and a foaming agent, and pours in excess of 3.0 ft may tend to increase the density of the lower portion of the pour as the weight of the material forces air out of the mixture. It should be noted, however, that any suitable pour depth is considered applicable to the present invention. EF has a relatively low viscosity and low density thus exerting a small lateral load on the tilt-wall until it becomes hardened. It should be noted that in the bridge abutment application of this invention, the bridge piles and pile caps are preferably already installed prior to the EF being poured. The bridge deck may be laid either before or after the EF is poured. Once the EF is layered to a desired height the roadway base and pavement are installed according to local state department of transportation standards. 
         [0028]      FIG. 4  is a cross-sectional view of the bridge approach and abutment structure at the anterior wall  12 . As best illustrated in  FIG. 4 , tilt-wall panels  12  rest vertically on concrete footings  24 , and laterally secured by a curb  25 . Tilt-wall panels  12  are affixed to each other with joints formed on the vertical edges of adjacent panels. In the preferred embodiment, the concrete footing  24  is approximately 1.0 ft. thick and formed of 3000 PSI concrete. Furthermore, in the preferred embodiment the tilt panel joints are approximately ¾″ wide and may be filled with EF or a suitable filling material. Additional tilt-wall panels are lifted, braced, and affixed to each other until the form for desired perimeter wall is complete. Once all the tilt panel walls are in place the lightweight concrete mixture is poured in approximately 3.0 ft. lifts, referenced as  20 . Additional stability may be provided by a secondary pour of concrete which lines the exterior of the tilt-wall panels along their bases to form a curb  25 . The secondary pour may be secured to the footing using reinforcement bars (not shown). In the preferred embodiment the secondary pour is of an approximately 8 inch by 8 inch square cross section, is formed of 4000 psi concrete, and uses #4 imperial bar size reinforcement steel dowels. 
         [0029]    A tie back slab  28  comprising regular concrete (e.g. not EF) may be poured between pilings affixed to each tilt-wall panel  12  to secure the tilt-wall into place horizontally using the friction created by the layers once they have been poured and allowed to harden. The tie back slab  28  may be of varying dimensions and may be affixed to the tilt-wall  12  using steel reinforcement bars  29  embedded in the slab and affixed to the panel wall  12 . Furthermore, additional, vertically spaced tie back slabs may be used on each tilt-wall panel depending on the height of the panel. In the preferred embodiment, the tie back slab is approximately 4.0 inches thick, and is secured to the tilt-wall panels using #4 imperial bar size steel reinforcement dowels  29 . Furthermore, a precast cap  30  may be affixed to the top of the tilt-wall panel  12 . Precast cap  30  may be of similar specifications to the concrete mixture which makes up the tilt-wall panels  12 .  FIG. 3  further depicts conventional bridge-related structures including a U.S. Department of Transportation (DOT) approved road base  32 , bridge deck  34 , and pre-cast traffic railing  36 . A series of pilings  37  support a pile cap  38  which in turn supports a plurality of bridge girders  39 . 
         [0030]      FIG. 5  is a cross-sectional view of the approach ramp wall. As previously disclosed, the tilt-wall panels  14  are each raised and secured with a brace  26 . The tilt-wall panels  14  are supported on a concrete footing  24  and are stabilized using tilt form braces  26  that are preferably disposed on the interior of the approach/abutment perimeter. The present invention contemplates that tilt form braces  26  will remain to support panels  12 ,  14 , and  16  during the various stages of construction, particularly during the pours of EF and remain abandoned in place within the approach/abutment structure upon completion of the project and thus providing continuing structural support. Tie back slabs  28   a  and  28   b  and cast-in-place traffic railing  36  are installed in engagement with the top portions of wing wall panels  14  and  16 . Although two tie back slabs are shown in  FIG. 4 , any number of tie back slabs may be used on each tilt-wall panel to best accommodate the panel&#39;s height. The preferred embodiment of the approach ramp uses the same dimensions and specifications as those of the preferred embodiment of the bridge abutment. 
         [0031]    A further advantage of using EF as fill material formed by sequential pours in 3.0 ft. lifts, results from the resulting layered structure. More particularly, there are often utility lines, pipes, conduits, etc. (hereinafter “utilities”), generally referenced as  40  installed within the approach and abutment structure. The use of EF to form a layered fill structure allows for the locating of utilities in one or more predetermined layers. The present invention contemplates the use of a colored dye mixed with the EF to from a uniquely colored layer within the approach/abutment structure for the purpose of identifying the presence of utilities within such layer. 
         [0032]      FIG. 6  is another sectional view through a wing wall structure constructed in accordance with the present invention. A tilt-up wall panel  14  comprises a pre-cast monolithic structure having a bottom  14   a  and a top  14   b . Bottom  14   a  of panel  14  is mounted on a concrete footing  24  and braced from outward movement by a curb  25 . Footing  24  and curb  25  are connected by reinforcing bar  27 . EF fill material  20  encloses a tie-back slab  28  which anchors a reinforcing bar  29  having an end embedded within wall panel  14 . 
         [0033]    While the present disclosure may be susceptible to embodiment in different forms, the drawings show, and herein will be described in detail, embodiments with the understanding that the present description is to be considered an exemplification of the principles of the disclosure and is not intended to be exhaustive or to limit the disclosure to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. It is expressly noted that the constructions and methods disclosed herein are particularly suited for the construction of bridge approaches and abutment structures, but also suitable for bridge widening and road widening projects. Accordingly, the constructions and methods may be employed equivalently in road widening projects wherein wing walls are fabricated without an abutment or bridge span, in bridge widening projects, or any other civil engineering construction wherein a retaining wall and back fill system are desired. Thus, any reference to bridge approach and/or abutment in the claims shall include as an equivalent, road widening constructions and bridge widening constructions. 
         [0034]    The instant invention has been shown and described herein in what is considered to be the most practical and preferred embodiment. It is recognized, however, that departures may be made therefrom within the scope of the invention and that obvious structural and/or functional modifications will occur to a person skilled in the art.