Patent Publication Number: US-6668412-B1

Title: Continuous prestressed concrete bridge deck subpanel system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U. S. Provisional Application No. 60/047,891, filed May 29, 1997. 
    
    
     STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     This invention relates to a subpanel system for bridge deck construction, and, more particularly, to a subpanel system that is prestressed in the transverse direction, and continuously connected in the longitudinal direction. 
     A great majority of bridges constructed in the United States utilize a concrete deck slab. A major disadvantage of utilizing concrete slabs is the deterioration of the concrete bridge deck and the need for rapid replacement of the deck. A number of different bridge constructions have been developed over the years for new bridge construction or for rehabilitation of deteriorated bridge decks. 
     A first of these construction systems is a full-depth, cast-in-place bridge deck system. This system involves the casting of the entire bridge deck in place utilizing wood forms constructed at the bridge construction site. The bridge deck is generally cast as a one piece full-depth structure. This type of construction system suffers from numerous serious disadvantages. First and foremost is the speed with which a bridge deck can be constructed. More specifically, creation of wood forms for the pouring of the bridge deck oftentimes is very labor intensive and time consuming. This is especially true in the edge portions of the bridges where an overhang extends beyond the edge of the nearest support girder or beam. In addition, due to the length of time required to install such forms and thereafter pour the concrete, the. forms generally are expensive to utilize. More specifically, they require great labor to set up the form and to thereafter remove the form from the bridge deck. In addition to speed and cost concerns, anytime the entire structure is poured in place, there can become serious questions of the quality of the entire bridge deck. As is apparent, the knowledge and skill of workmen in addition to various weather factors can affect the quality of the concrete poured throughout the transverse and longitudinal sections of the bridge deck. Additionally, such full-depth, cast-in-place systems oftentimes do not offer a realistic approach to rehabilitation of deteriorated bridge decks. 
     A second type of bridge deck system is the full-depth prefabricated deck system. As the name suggests, this involves entirely prefabricated deck panels which are positioned in place above bridge girders to form the deck system. There generally is little or no concrete pouring involved in constructing a bridge deck of this type. The main advantage associated with these prefabricated deck systems is that construction time is reduced, and the forming required for casting is eliminated. However, again, this type of system has serious drawbacks. First of all, because the entire depth is a prefabricated item, adjacent decks of the system are riot easily adjusted with respect to one another. Additionally, to create a smooth upper surface, substantial amounts of grinding are required between adjacent panels to increase the ride and quality of the bridge structure. Further, oftentimes it is necessary to longitudinally post-tension the prefabricated structures to control transverse joint cracking. Still furthermore, support beams and girders must have a special type of shear connector arrangement to fit into the pockets formed on the underside of the prefabricated bridge deck panels. 
     A still further type of bridge deck construction system involves a combination of a cast-in-place deck and a stay-in-place precast concrete panel. More specifically, most of these systems involve providing a thin solid precast prestressed panel to rest on top of the support beams or girders and to operate as a form for a cast-in-place layer placed on top of the prestressed panels. The panels are generally three to four inches in thickness and are produced in four to eight feet widths depending upon the available transportation and lifting equipment. The precast panels that form the base layer of such structure are butted against one another without any continuity between them. More specifically, nothing is utilized to connect the panels together as they rest adjacently on the reinforcing beams in both the transverse and longitudinal direction. This combination bridge If deck system suffers from numerous drawbacks. Although this system offers advantages in the form of prestressing in the individual panels themselves, the system still suffers from serious disadvantages. More specifically, because there is no way to support a prestressed concrete panel adjacent an edge girder to form a bridge overhang, it is still necessary to use forming structures adjacent the bridge edge to form such overhangs, thus resulting in the cost and labor intensive practices associated with such forms. Additionally, constructing a bridge deck can require the placement of numerous precast prestressed panels. More specifically, it could be required to place as many as three to four panels to transverse the width of the bridge structure with additional transverse rows necessary to cover the longitudinal length of the bridge. Each of these panels must be placed with precision, thus increasing the labor hours and costs of placing the panels. Additionally, a problem associated with precast prestressed concrete subpanels is reflective cracking during use. More specifically, it has been found that after travel over a bridge deck, cracks develop in the upper cast-in-place topping which outline the subdeck prestressed concrete panels. The reflective cracking is generally due to the lack of continuity in both the longitudinal and transverse directions. It has further been found that because of the lack of continuity between layers, if a bridge is to fail under loads, it will often fail adjacent a support girder or beam due to the shear stresses associated at such locations, caused by lack of continuity of the steel reinforcement at such locations. 
     A bridge deck construction is needed which alleviates the problems associated with the prior art as discussed above. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a bridge deck construction which is more cost-effective and simpler to construct. 
     Another object of the present invention is to provide a bridge deck construction which allows for excellent field quality in construction, and, further, offers long-term durability of the bridge deck. 
     A further object of this invention is to provide a bridge deck construction which eliminates the need for field forming to create deck overhangs. 
     A still further object of the invention is to create a bridge construction precast panel system which is able to support paving machine and construction loads in additional to self weight such that there is no need to support an overhang during the casting of a topping slab. 
     A still further object of the present invention is to provide a bridge deck construction which eliminates the need to handle a large number of pieces and the need to precisely position the subdeck panels onto the support beams or girders. 
     A still further object of the present invention is to provide a subdeck system that eliminates reflective cracking. 
     Another object of the present invention is to provide a bridge deck construction that does allow for significant flexibility in placement of shear connectors on beams or girders. 
     A still further object of the present invention is to provide a bridge deck system that has superior performance than conventional prestressed panel systems under cyclic load. 
     Another object of the present invention is to provide a bridge deck system which has immensely increased failure load capacity over the conventional subdeck prestressed panel systems. 
     A still further object of the present invention is to provide a precast panel which can. be crowned during forming such that the crowning will be achieved across the transverse direction of the bridge. 
     Accordingly, the present invention provides for a prestressed concrete panel for bridge construction including a first section having at least one tension member extending therethrough. A second section is spaced from the first section and forms a gap therebetween. The tension member extends through the second section and across the gap. The gap is adapted to be aligned above a support beam. At least one compression member extends between the first and second sections in such a manner as to maintain the gap against the tension forces of the, tension member. 
     The present invention further provides for a connecting assembly adapted to connect adjacent panels of a bridge deck construction. Each panel has a reinforcing member therethrough with at least one exposed end. The assembly includes a splice member overlapping the exposed end of each reinforcing member of the adjacent panels. A locking member surrounds a splice member and the exposed end. 
     The present invention still further provides a method of producing a crowned prestressed concrete panel, including putting an elongated member into tension, thereafter deforming the elongated member from a linear path, thereafter pouring a concrete mixture around the tension elongated member and into a form that generally follows the deformed path of the elongated member. Thereafter, allowing the concrete mixture to cure and releasing the tension on the elongated member. 
     Additional objects, advantages, and novel features of the invention will be set forth, in part, in a description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top perspective view of a bridge deck construction according to the present invention, parts being broken away to reveal details of construction; 
     FIG. 2 is a cross-sectional view taking generally along line  2 — 2  of FIG. 1; 
     FIG. 3 is a top plan view of the forming of a panel according to the present invention, showing the positioning of tension members, compression members and longitudinal reinforcing members within the panel, prior to concrete being poured into the form to form a panel; 
     FIG. 4 is an enlarged view of the area generally designated by the numeral  4  in FIG. 6, and shows the construction of a pocket along a transverse edge of a panel; 
     FIG. 5 is a cross-sectional view taken generally along  5 — 5  in FIG. 3 showing the forming of the transverse channel of the panel and also the connecting pockets of the panel, concrete having already been poured into the form shown in FIG. 3; 
     FIG. 6 is a top plan view of a subdeck panel according to the present invention after it has been formed, but prior to placement on bridge support members; 
     FIG. 7 is a top plan view of two subdeck panels placed on a bridge support structure and connected together, prior to a topping slab being poured; 
     FIG. 8 is a top plan view similar to FIG. 4, showing an intermediate step in connecting subpanels longitudinally together; 
     FIG. 9 is an enlarged view of the area designated generally by the numeral  9  in FIG. 7, showing the longitudinal connecting structure between adjacent panels, prior to the pouring of the topping slab; 
     FIG. 10 is a cross-sectional view taken generally along line  10 — 10  of FIG. 9; 
     FIG. 11 is an enlarged view of the area designated generally by the numeral  11  in FIG. 10; 
     FIG. 12 is an enlarged view of the area designated generally by the numeral  12  in FIG.  7  and showing the positioning of the subpanel gaps above the support members of the bridge construction; 
     FIG. 13 is a cross-sectional view taken generally along line  13 — 13  of FIG. 12; 
     FIG. 14 is a top plan view of the bridge deck construction of FIG. 1, parts being broken away to reveal details of construction; 
     FIG. 15 a  is longitudinal cross-sectional view taken generally long line  15   a — 15   a  of FIG. 3 showing an elongated member in the form of an arc; 
     FIG. 15 b  is an enlarged view of the area designated generally by the numeral  15   b  in FIG;  15   a  showing the bridge subdeck panel and a crowing feature of the panel; 
     FIG. 15 c  is transverse cross-sectional view taken generally long line  15   c — 15   c  of FIG. 15 a  showing the degree of curvature of a concrete panel; 
     FIG. 16 is a cross-sectional view taken generally along line  16 — 16  of FIG. 6; 
     FIG. 17 is a cross-sectional view taken generally along line  17 — 17  of FIG. 6; 
     FIG. 18 is a cross-sectional view taken generally along line  18 — 18  of FIG. 6; 
     FIG. 19 is a cross-sectional view taken generally along line  19 — 19  of FIG. 7; 
     FIG. 20 is a view similar to FIG. 3 showing the position of an alternative prestressing arrangement utilizing an encircling spiral in the overhang section of a panel; 
     FIG. 21 is a partial cross-sectional view taken generally along line  21 — 21  of FIG. 20, but showing the overhang section having been poured and formed, and further showing an alternative pocket structure and end surface; 
     FIG. 22 is a sectional view taken generally along line  20 — 20  of FIG. 21; 
     FIG. 23 is a cross-sectional view taken generally along line  23 — 23  of FIG. 20; but showing a panel poured and formed; and 
     FIG. 24 is a view similar to FIG. 13, but showing an alternative grout barrier arrangement. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings in greater detail, and initially to FIGS. 1 and 14, a bridge deck construction designated generally by the reference numeral  20  is shown. Bridge construction  20  includes a plurality of prestressed precast concrete panels  22  and a cast-in-place concrete topping  24 . Panels  22  form the subdeck of the bridge construction and are positioned on top of the beams or girders  26  in a manner that will be more fully described below. Topping  24  forms the roadway surface upon which vehicles will travel. With reference to FIGS. 6 and 7, each panel  22  is formed such that it extends across the entire width of the bridge construction. At the girder positions of the bridge, full length gaps  28  are provided. Gaps  28  allow accommodation of shear connectors  30  which extend upwardly and are fixedly attached to girders  26  as best shown in FIGS. 12 and 13. As can be best. seen in FIG. 12, a plurality of shear connectors  30  are aligned along girder  26  and, further, extend into the respective gap  28  above girder  26 . 
     Each panel  22  is pretensioned from end to end utilizing a plurality of wire strands  32  as best shown in FIGS. 3,  6  and  16 - 18 . Strands  32  are provided in two layers through the height of panel  22  and are uniformly spaced across the width of panel  22 , as best shown in FIGS. 3,  6  and  18 . Each strand  32  extends substantially the full length of each panel  22 , including the distance across gaps  28 . Strands  32  provide for pretensioning of panels  22  in a manner as will be described below. Extending across each of the gaps  28  is also a plurality of compression bars  34 . Bars  34  are embedded in adjacent concrete sections of panels  22  and serve to transmit the prestressing force from one section to another section over the gaps  28 . Bars  34  are also positioned in two layers, as best shown in FIG.  18 . Other compressive structure could be used in addition to or in place of bars  34 . For example, concrete pillars extending across gaps  28  could be used as compressing members. 
     As shown in FIGS. 6, and  7 , each panel  22  has three different sections. More specifically, there is a middle section  36  and overhang sections  38  on each end. Sections  38  form the overhang portion of a bridge deck. The prestressing strands  32  extending throughout the length of the panel  22  allows the supporting of overhang sections  38  in a cantilevered fashion from the nearest support girder. Thus, as is apparent, the need for utilizing expensive forming structures to construct overhang sections is avoided. 
     Although the panel  22  shown in the figures has three sections, any number of sections can be utilized, depending upon the width of the bridge deck and the number of girders needed to support it. For example, a bridge having a width of 44 feet would consist of three 12-foot middle sections plus two 4-foot overhang sections  38 . Such a bridge construction would have four supporting steel girders and four gaps formed with each panel. The width of panels  22  could preferably vary from four feet to twelve feet, depending upon the transportation and lifting, equipment available, although other widths could be feasible. It has been found suitable to form panel  22  with a 4.5 inch height and out of high-strength concrete with a specified concrete release strength of 4.0 ksi, and a 28-day compressive strength of 10.0 ksi. Further, it has been found suitable to utilize one half inch low relaxation strands of 270 ksi as strands  32 . Still further, a suitable spacing for strands  32  is 12 inches, and the minimum concrete cover over the strands with relation to the nearest top or lower surface has been found to be one inch. Additionally, a suitable dimension for gap  28  has been found to be eight inches for a twelve-inch girder. Bars  34  are preferably # 6  reinforcing bars and are generally embedded into the adjacent sections of each panel to a depth of 18 inches. 
     Each panel  22 , in addition to transverse strands  32  and compression bars  34 , has reinforcing longitudinal bars  40 , as best shown in FIGS. 3,  6  and  17 . Bars  40  are equally spaced along the width of each panel  22  and have exposed ends  42  along each edge. Additionally, along each edge of panel  22  is a transverse extending a channel  44  with a generally diamond-shaped cross section, as best shown in FIGS. 16,  18  and  19 . Channel  44  extends from one end of each panel to the other end (as best shown in FIG. 6) and is generally asymmetrical such that the bottom planar surface  46  of channel  44  extends outwardly beyond the upper planar surface  48 . In this manner, a lower transverse edge  50  is formed which juts out beyond the upper transverse edge  52 . 
     Disposed at spaced intervals along both transverse edges of the panel is a plurality of pockets  54 , as best shown in FIGS. 4 and 6. Pockets  54  are formed adjacent the exposed ends  42  of bars  40 . Each pocket  54  is formed of a generally trapezoidal shape which is open at the top and closed at the bottom. The closure at the bottom is formed by a metal plate  56 . Plate  56  is utilized in forming pockets  54  and remains a part of panel  22 . Plates  56  have dovetail or protrusion portions  58  which extend upwardly into the concrete of panels  22  to ensure that plate  56  is attached in position. Plate  56  has a generally rectangular. shape along the bottom surface adjacent the pockets  54 , as best shown in FIGS. 4,  5 . and  17 . The general shape of pockets  54  is such as to form a trapezoidal, three-dimensional figure positioned on its side with a rear wall  60 , bottom wall formed by plate  56 , and an open top and an open front. Exposed ends  42  of bars  40  terminate at a horizontal location that is approximately above lower transverse edge  50 , as best shown in FIG.  4 . 
     The structure of channel  44 , pockets  54 , and exposed ends  42  allow for continuity in the longitudinal direction between adjacent panels  22 . More specifically, as best shown in FIGS. 7,  9 , and  10 , two adjacent panels  22  are positioned next to one another such that their gaps  28  and pockets  54  align. As a result of this positioning, exposed ends  42  of adjacent panels are generally in line with one another, but not touching one another. A connection between the exposed ends of adjacent panels is accomplished by utilizing an expandable spiral connecting member or coil  66  and a splice segment or rod  68 . As shown in FIGS. 9 and 10, rod  68  overlaps both the exposed ends  42  of adjacent panels  22 . Spiral member  66  surrounds both exposed ends  42  and splice rod  68 , and is expanded in aligned pockets  54  such that the ends of the spiral member  66  engage the rear walls  60  of adjacent pockets. Also positioned between adjacent panels  22  is a backer rod  70  made of a foam or rubber-type compressible material. Rod  70  generally is compressed between transverse lower edges  50  of adjacent panels, as best shown in FIGS. 11 and 19. The purpose of backer rod  70  is to provide a seal along the lower ends of adjacent channels  44 , such that when topping  24  is poured along the top surface of panels  22 , the concrete from topping  24  will flow into channels  44  and pockets  54  to surround spiral members  66  and splice rod  68  to create a continuous splice between adjacent panels after the concrete of topping  24  cures. Additionally, the shape of channels  44  serve as a lock against shear forces between adjacent panels. More specifically, the material flowing within the channels extends inwardly to the interior of adjacent panels such that shear forces applied between the panels will be resisted. The general diamond-shape of channel  44  can be conveniently molded, but other shapes that extend into the interiors of the panels along the edge may be appropriate. 
     With reference to FIG. 8, the method of installing spiral member  66  and splice rod  68  is shown. More specifically, after one panel  22  is in place on a bridge support structure, a compressed spiral member  66  is positioned along the exposed ends  42  of one edge. Spiral  66  is held in this compressed state by a tie wire  72 . Thereafter, a second panel  22  is lowered adjacent to the panel  22  with compressed spiral members  66 , and a backer rod  70  is placed between the lower edges  50  of the adjacent panels. Thereafter, a splice rod  68  is overlapped over adjacent exposed ends  42  and tied thereto via tie wire  74 . After this is done, tie wire  72  is cut and spiral member  66  expands between the adjacent pockets  54 . 
     It has been found suitable to construct longitudinal bars  40  of a # 4  bar and to construct plate  56  of a 20-gauge, generally square piece of sheet metal. Suitable spacing for the pockets  54  and bars  40  is approximately two feet. Splice rod  68  can also be formed of a # 4  bar. 
     With reference to FIGS. 12 and 13, a leveling device  76  and grout stoppers  78  will be described. To level the panels on the supporting girders  26 , a simple leveling device  76  is utilized. The leveling device consists of a plate  80 , having an aperture therein, to which is welded a nut  82 . A bolt  84  is received through the aperture in plate  80  and through nut  82 . Plate  80  is mounted between the top flange of the girder and the lower layer of bars  34 . At least two assemblies are provided in each gap, and can be utilized to adjust the level of the panel simply by applying a torquing force to bolts  84 . Before panels  22  are positioned on support girders  26 , grout barriers  78  are installed along the girder flange edges, as best shown in FIG.  13 . Grout barriers  78  generally are formed of a light. gauge metal and have a U-shape that extends along the length of gaps  28 . The upper portion of grout barrier  78  is positioned along the lower surface of panel  22 , as best shown in FIG. 13. A standard construction adhesive is utilized to attach grout barriers  78  to both girder  26  and the bottom surface of panels  22 . 
     Once the panels  22  are placed over girders  26  and adjusted with leveling devices  76 , gaps  28  are thereafter grouted with a flowable mortar mixture to about 1.5 inches below the top surface of the panel  22 . The mortar mixture is preferably of a compressive strength of 4.000 psi and 20-day compressive strength. At the time of casting, the mortar provides a compression block needed to resist. negative moment over girders  26  due to loads imposed by concrete paving machines and the self weight of concrete topping  24 . It also provides concrete bearing for panels  22  over the girders because the mortar flows under the girders into the U-shaped portions of grout barriers  78 . 
     After panels  22  have been positioned and connected via spiral members  66  and splice rod  68 , and grout poured into gaps  28  and allowed to set, cast-in-place concrete topping slab  24  is  5  then poured. Prior to the pouring of slab  24 , a wire fabric mesh  86  can be utilized to provide additional reinforcement within slab  24 . It has been found suitable to have slab  24  be approximately 4.5 inches in height and wire fabric  86  to be of an epoxy-coated welded type. As discussed above, as topping  24  is poured, the concrete from the topping flows into channels  44  of adjacent panels, and also around spiral member  66  and splice rod  68  to effectuate a longitudinal joint between adjacent panels. 
     Generally, the construction steps of bridge construction  20  involve first cleaning the surfaces of girders  26 . Thereafter, grout barriers  78  are glued along their lower edges to the top surface flange of girders  26 . Precast panels  22  are then installed and adjusted with the level devices  76  preattached. The backer rod  70  is positioned between adjacent panels to prevent leakage during the casting of the cast-in-place topping slab  24 . Thereafter, gaps  28  are filled with the flowable mortar mix or rapid set nonshrink grout to a height that is approximately 1.5 inches below the top surface of the precast panel. Thereafter, splice rods  68  are installed, and spiral members  66  are released from their compressed position by cutting tie wires  72 . Wire fabric  86  is thereafter installed along the top surface of panels  22  and topping slab  24  is cast in place and cured. 
     General design of bridge construction  20  is accomplished utilizing AASHTO Standard Specifications 16th Edition. The design procedure consists of two different sections: (1) the precast panel, and (2) the composite section. The precast panel is designed to support precast panel self weight, topping slab  24  self weight, a construction load of 50 lbs. per square feet, and the loads provided by the concrete paving machine. The composite section (the subpanels  22  and topping slab  24 ) is designed to support the superimposed dead loads of a two-inch concrete wearing surface, barrier self weight and live loads. An HS25 truckload is considered as the live load. This is equivalent to AASHTO HS20 loading magnified by a factor of 1.25. A New Jersey barrier type, of 330 lbs. per foot self weight, is considered. 
     For the design of precast panel  22 , two stages were considered: (1) release of prestress; and (2) casting of topping slab  24 . At release stage, compatibility and equilibrium equations are applied at the section at the gap to calculate the compressive stresses gained in bars  34 , and tensile stress lost in prestressing strands  32 . Therefore: 
     Where: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 ε 
                 = the elastic strain loss in the gap 
               
               
                   
                 f pi   
                 = tensile stress in the strands just before release 
               
               
                   
                   
                 = 0.75 × 270 = 202.5 ksi (1396 MPa) 
               
               
                   
                 A, 
                 = the cross section area of the reinforcing bars 
               
               
                   
                   
                 = 28 × 0.44 = 12.32 in 2  (7948 mm 2 ) 
               
               
                   
                 A p   
                 = the cross section area of the prestressing strands 
               
               
                   
                   
                 = 16 × 0.153 = 2.448 in 2  (1579 mm 2 ) 
               
               
                   
                 E, 
                 = the Modulus of Elasticity of the reinforcing bars 
               
               
                   
                   
                 = 29,000 ksi (200 × 10 3  MPa) 
               
               
                   
                 E p   
                 = the Modulus of Elasticity in the prestressing strands 
               
               
                   
                   
                 = 28,000 ksi (193 × 10 3  MPa) 
               
               
                   
                   
               
            
           
         
       
     
     Therefore:              ɛ   =                  2   ,   448   ×   202.5         12.32   ×   29   ,   000     +     2.448   ×   28   ,   000                     =                1.164   ×     10     -   3                       in   .     /            in   .                             
     Compression stress in the reinforcing bars 
     
       
         =ε( E ,) 
       
     
     
       
         =(1.164×10 −3 )(29,000)=33.76 ksi (233 MPa) 
       
     
     Tensile stress in the prestressing strands 
     
       
         =f pi −ε( E   p ) 
       
     
     
       
         =202.5−(1.164×10 −3 ) (28,000) 
       
     
     
       
         =169.91 ksi (1171 MPa) 
       
     
     Similar analysis at the midspan between the girder lines needs to be conducted to determine the tensile stresses in the prestressing strands at that location. This is needed for the positive moment design. Calculations show that this value is in the range of 191 ksi. 
     Reinforcing bars  34  and gaps  28  must be adequate to satisfy two design criteria: (1) preserve as: much prestress in the strands as possible; and (2) transfer the prestresses to the adjacent concrete without too much stress concentration. The first criterion was already covered above. Satisfaction of the second criterion is not totally clear to the inventors. A conservative approach is to use the tension development length as the minimum required embedment into the concrete. However, this may be an “overkill” as the bars are expected to be predominantly in compression and the end bearing is totally ignored. The suitable 18-inch embedment mentioned above is not too wasteful in terms of the overall cost of the system. The buckling length of bars  34  at the gap is also checked to protect these bars from buckling. 
     At topping slab  24  casting stage, three sections are checked: (1) maximum positive moment section between girders  26  under the self weight of precast panels  22  and topping slab  24  and construction load; (2) maximum negative moment section at interior supports under the self weight of precast panel  22 , topping slab  24 , and the construction load; and (3) maximum negative moment section at the exterior support under the self weight of precast panel  22 , topping slab  24 , the construction load, and the concentrated loads provided by the concrete paving machine. For the maximum positive moment section the service concrete stresses and the ultimate flexure capacity of precast panels  22  are checked. For the maximum negative moment sections, the ultimate flexural capacity was checked. 
     With reference to FIGS. 3 and 5, the forming of panels  22  will be generally described. Wood forms  88  can be used to form the general shape of panels  22 , and, further, to form channels  44  in the transverse edges of panel  22 . Polystyrene foam  90  and plate  56  are utilized to form pockets  54 . Additionally, polystyrene foam or wood forming can be used to form gaps  28  between adjacent sections of each panel  22 . It should be noted, however, that in commercial production, steel forms may be preferable to form all the above structures. The production sequence of panels  22  is first to assemble wood side forms  88  to form the shape of panels  22 . Thereafter, the lower layer of strands  32  are installed and tensioned to 0.8 fpu. (Note that 0.05 fpu is considered for jacking losses). The lower layer of bars  34  is then installed. Thereafter, longitudinal bars  40  were installed at the pocket locations through polystyrene foam forms  90 . Metal plates  56  were then installed in their position adjacent each pocket  54 . The upper layer of strands  32  is then installed and tensioned to 0.8 fpu. Thereafter, the upper layer of bars  34  is installed. Concrete is then cast and vibrated and the top surface of the panel is roughened utilizing a silk brush to a height of approximately 0.5 inches. The concrete is cured using wet burlap for ten continuous days. A torch cut is utilized to release strands  32 . It is believed that smooth surfaced strands  32  may be desirable to avoid possible cracking upon release of the tension utilizing the torch cut. Additionally, symmetrical release of the forces using torch cut could also be advantageous in eliminating potential cracks. 
     Testing of bridge construction  20  under a cyclic load has revealed that the structure will have much less cracks than the conventional stay-in-place panel system which is not connected in the transverse and longitudinal. direction. Additionally; reflective cracking in the bridge construction was virtually nonexistent through testing, thus eliminating a flaw in conventional systems that is considered the main reason for corrosion of reinforcing steel and deterioration of a bridge deck slab. Testing of the bridge construction  20  under ultimate load revealed a very ductile behavior of the bridge construction even after failure. Comparison of the behavior of system  20  with conventional stay-in-place panel systems reveals that system  20  has almost double the capacity of the conventional system, has a much more ductile behavior, and has much less deformation. Testing revealed that connecting the panels transversely and longitudinally prevents the steel reinforcement in the cast-in-place topping from corrosion and leads to a better distribution of live load stresses throughout the system. 
     Bridge construction  20  offers substantial advantages over prior continuous stay-in-place precast prestressed panel. systems, and full-depth cast-in-place systems. More specifically, bridge construction  20  clearly eliminates the need for forming deck overhangs, thus eliminating costs and labor intensive operations that were required in prior art structures. Further, during rehabilitation of bridge decks, construction  20  saves the time needed to rearrange the shear connectors on girders  26  because of the optimized spacing between the reinforcement and the gaps over the girders. The present system further saves substantial amounts of time and labor because panels  22  cover the entire width of the bridge, thus, eliminating the need to handle a large number of pieces as in the case of conventional stay-in-place precast panels. Still further, because panels  22  are designed to support paving machine loads and construction loads, in addition to the self weight and topping slab  24  weight, there is no need to support overhang sections  38  during casting of topping slab  24 . 
     Still further, the longitudinal continuity of the panels via pockets  54 , spiral members  66 , and splice rod  68  result in longitudinal continuity which results in minimization of reflective cracks at the transverse joints, such cracks being the major reason for failure in prior art systems. The system further provides for superior performance than conventional stay-in-place panel systems under cyclic load, and also has almost double the capacity of conventional stay-in-place panel systems. 
     With reference to FIG. 15, a novel crowning feature of the present invention is shown and will be described. More specifically, during forming of panel  22 , it may be desirable to attempt to have the middle more elevated than the edges in a gradual manner such that water will flow toward the end edges of the panels. This can be accomplished by deforming strands  32  prior to pouring panels  22 . With reference to FIG. 15, a deforming structure  92  is shown. More specifically, to form a crown structure, a crowned wood form is first built. Thereafter, a strand  32  is put in tension and is deformed at any one of a plurality of locations such that tension strand  32  generally follows the path of the crowned wood form. Deforming structure  92  is attached to fixed structures  96  outside of wood form  88  to allow the deformation. A bolt  94  can be used to adjust the deformation of strands  32 . After strands  32  generally follow the crowned path of form  88 , concrete can then be poured therein and allowed to cure. The crown structure with the prestressed strands therein will maintain its crown shape because the strand is advantageously positioned in the center of the cross section of the panel. Contrary to instinctive belief, so long as the strand is properly positioned in the cross section, the panel will not attempt to straighten out, and will perform very favorably when put under load. As is apparent, this crowning feature can be utilized in any type of subdeck system, not just the one described above with respect to construction  20  having gaps  28 . Deforming structures  92  can be left in the formed panel and cut from the supporting structure  96  utilized outside the wood frame  88 . 
     With reference to FIGS. 20-23, an alternative structure for reinforcing strands  32  is shown. In particular, in the overhang sections  38  of panel  22 , it may be desirable to encircle each of the pairs of strands with a spiral member  100  which extends generally the entire width of section  38  from gap  28 ; to the edge of overhang section  38 , as best shown in FIG.  20 . FIG. 20 shows the encircling spiral arrangement prior to the pouring of concrete to form section  38 . It has been found advantageous to utilize spiral  100  around strands  32  to increase the tensioning force of the strands adjacent the edges of the overhang sections  38 . In particular, in the past, it was found that utilization of the pairs of strands  32  without the coil resulting in a less tensioned area of concrete adjacent the outer edge of overhang  38 . The encircling of strands  32  by spiral  100 , as shown in FIGS. 21 and 23, has been found to increase the pretensioning in the edge portions of section  38 . Coil  100  is preferably a 3-inch outside diameter spiral. 
     With reference to FIGS. 21 and 22, an alternative pocket structure  102  is shown. In particular, pocket  102  is generally rectangular-shaped and formed by blockout plates  104 . Blockout plates  104  extend on the back wall of pocket  102 , the side walls of pocket  102 , and the bottom wall of pocket  102 . Blockout plates  104  can be made of any suitable material, for instance, metal, and can all be formed together in the desired pocket shape. Blockout plates  104  can be positioned in a form prior to forming of a panel and remain in place after such forming. Blockout plates  104  aid in the forming of pockets  102 . 
     With reference to FIGS. 21-23, an alternative to channel  44  is shown. In particular, in place of channel  44 , a ridged surface  106  can be utilized. Ridge surface  106  can extend the entire width of each panel  22 . Ridge surface  106  serves the same function of channel  44 . In particular, when two. panels are butted against one another, topping  24  is poured into the gap formed between the two panels. Once topping  24  hardens, the shape of ridge, surfaces  106  helps resist vertical movement between adjacent panels. As is apparent, ridge surface  106  may be more conveniently formed than channel  44 . 
     With reference to FIG. 24, an alternative grout barrier  108  is shown. Grout barrier  108  includes dual pieces of an angle iron structure,  110 , which generally extend in a parallel relationship along the edges of girder  26 . Pieces  110  are connected together via a plurality of braces or supports  112  which are spaced at locations along the longitudinal length of pieces  110 . Each piece  110  has a slot or equal structure  114  which can be utilized in conjunction with threaded surfaces  116  and nuts  118  of brace  112  to adjust the height to which piece  110  extends above the top surface of girder  26 . In particular, each brace  112  holds the pieces  110  in their relative relationship on top of girder  26 . To ensure that the engaging surfaces  120  of piece  110  engages the bottom surface of a panel, slots  114 , threaded surface  116 , and nuts  118  can be utilized to move each of the pieces  110  upward to ensure engagement. As is apparent, this provides an easy adjustable structure to prevent grout from flowing between the girder  26  and the panel  22 . It has also been found that it is not necessary to utilize any sort of adhesive or glue to secure grout barriers  108  in position adjacent their girders or the panels. 
     From the foregoing, it will be seen that this invention is one well-adapted to obtain all the needs and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative, and not in a limiting sense.