Patent Publication Number: US-11643783-B2

Title: Simplified steel orthotropic deck bridge panel

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates to steel orthotropic deck panels used in building bridges. 
     BACKGROUND OF THE DISCLOSURE 
     Currently, orthotropic deck panels for constructing bridges are fabricated by welding a series of steel ribs to the underside of a flat steel deck plate so that the ribs extend parallel to one another in a longitudinal direction of the deck panel. The prevailing use for current orthotropic designs is on high traffic volume, long span bridges (i.e. bridges having a span of 140 feet or more), where a reduction in deadload is the focus. This convergence of designing for high-volume roads and a focus on least weight creates complex fabrication requirements. For example, to prevent fatigue cracking of rib to deck plate welds, strict quality control measures are necessary during welding and subsequent inspection. Nevertheless, an orthotropic deck fabricated from steel is an economically efficient system for reducing deadload weight on long span bridges, and has longer life span compared to concrete bridges. 
     By contrast, the short span bridge market (i.e. bridges having a span less than 140 feet) is defined by cost sensitivity, minimization of structural depth, and ease of construction. The complex geometries, tight tolerances, and detailed welding procedures for fabricating orthotropic decks make them economically unviable for short span bridges, where competing structure types such as concrete slab and box beam decks offer better overall economics. The Average Daily Traffic (ADT) for short span bridges is 7,533 vehicles per day, whereas the ADT for long span bridges is 22,245 vehicles per day. 
     In current orthotropic decks, the ribs are fabricated using a press brake to form longitudinal bends in a length of steel sheet material. For example, in the case of a closed trapezoidal rib, a pair of parallel longitudinal bends are formed by the press brake to define a bottom wall and a pair of side walls extending from opposite sides of the bottom wall. This current fabrication technique has shortcomings. One shortcoming is that the overall length of commercial press brakes is limited, so the overall rib length is limited to about 60 feet. Another shortcoming is that camber cannot be induced during the press brake operation. Camber adds extra structural support and is used with the purpose of counteracting deflection due to load. Finally, use of a press brake to form the rib segments means that additional manufacturing steps are needed to bend and to introduce camber into the ribs. In these conditions the manufacturing cost makes the steel press brake rib financially non-competitive with the similar concrete products. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure provides a cost-effective orthotropic deck bridge panel which is capable of being standardized to facilitate the use of orthotropic decks on short span bridges. 
     The inclusion of a concrete deck is a notable difference between the orthotropic deck panel of the present disclosure and known orthotropic deck designs. Inclusion of a concrete deck simplifies fabrication details, thereby increasing the economic viability of the disclosed orthotropic deck panel in the short span bridge market. 
     The present disclosure also overcomes the shortcomings in rib fabrication mentioned above by using a cold roll-forming process instead of a press brake to form the longitudinal bends in the sheet material. Both press brake forming and cold roll-forming provide straight bend lines. During brake forming, the cross section is changed along the full length of the product during one instant impact inducing major stresses in the bends and their nearby vicinity. Cold roll-forming, however, is a progressive process. While one end of the strip is flat, the other end is completely formed; so, limited to non-existent stresses are introduced. As a result, each rib can be made as a unitary (i.e. one-piece) part of much greater length than is currently available using a press brake, thereby avoiding end-to-end welding of shorter rib sections. The raw material supply and the final product (rib) may be any length up to the maximum length allowed for shipping transport, estimated between 90 and 110 feet. Camber can be introduced in a controlled manner during the cold roll-forming process. Moreover, the inner radius of each roll-formed bend can be about 1½ to 2 times the material thickness, which is much less than the inner radius possible with a press brake. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING VIEWS 
       The nature and mode of operation of the present disclosure will now be more fully described in the following detailed description taken with the accompanying drawing figures, in which: 
         FIG.  1    is a perspective view of an orthotropic deck panel manufactured in accordance with an embodiment of the present disclosure; and 
         FIG.  2    is a partial cross-sectional view thereof. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS.  1  and  2    show an orthotropic deck panel  10  manufactured in accordance with an embodiment of the present disclosure. Deck panel  10  may be used in constructing a short span bridge. 
     Deck panel  10  generally comprises a flat deck plate  12 , a plurality of elongated ribs  14  welded to an underside of deck plate  12 , and a concrete deck layer  15  applied to a topside of deck plate  12 . 
     In the depicted embodiment, deck plate  12  is formed of ½-inch thick steel plate, for example ASTM A709 Grade 50 or ASTM A709 HPS70W steel plate. Other thicknesses and steel grades may be used to form deck plate  12 . The illustrated deck plate  12  may be 120 inches (10 feet) wide, and may have any suitable length. Due to shipping limitations, any length up to 90 feet is commercially viable. Other length and width dimensions may be used for deck plate  12  to suit the needs of the bridge deck design. 
     Each rib  14  includes a pair of bends  16  extending in a longitudinal direction of the rib, a bottom wall  18  between bends  16 , and a pair of side walls  20  each extending from a respective one of the bends  16  and terminating at a corresponding edge  22 . Bends  16  are formed by passing sheet material through a roll-forming machine including a series of roll-forming stations having rollers which are set up to engage the sheet material and progressively form each bend  16  as the sheet material advances through the roll-forming machine from one station to the next. The sheet material for ribs  14  may be a desired thickness allowing roll-forming, a desired width for achieving the desired rib dimensions (e.g. rib depth, bottom wall width, and bend angles), and the may be cut to a desired length before or after the sheet material is roll-formed into rib  14 . For example, the sheet material for ribs  14  may be ASTM A709 Grade 50 or ASTM A709 HPS70W steel plate having a thickness of 0.5 inches. The inner radius of each bend  16  is at least two time the thickness (e.g., for rib plate having a thickness of 0.5 inches, the minimum radius is at least 1.0 inches). Each bend  16  forms an included angle A between bottom wall  18  and the corresponding side wall  20 . For example, in the illustrated embodiment, included angle A is 97.0°, however the included angle A is subject to design choice and other angles may be used. The rib depth is subject to variation to meet design criteria. By way of non-limiting example, a rib depth on the order of between twelve inches and eighteen inches may be used. 
     Ribs  14  may be affixed to an underside surface of deck plate  12  by longitudinal welds  24  provided along each edge  22  and the underside surface of deck plate  12 . Edges  22  may be beveled to rest in flush surface-to-surface engagement with the underside surface of deck plate  12 . The bevel may be formed, for example, by grinding each edge  22  before, during, or after roll-forming each rib  14  from sheet material. The rib spacing in the lateral (i.e. width) direction of deck panel  10  may be determined based on the total number of ribs  14  needed and the overall width of deck panel  10  so that the ribs are evenly distributed across the underside of deck plate  12 . 
     Concrete deck layer  15  may be coupled to deck plate  12  by a plurality of shear studs  26 , and may include rebar reinforcement  28 . The thickness of concrete deck layer  15  may be the minimum thickness required for mitigating fatigue cracking of the rib to deck plate welds  24 . Determination of a suitable thickness for concrete deck layer  15  may be guided and informed by finite element analysis (FEA) modeling of deck panels  10  having various thicknesses of concrete deck layer  15 . As a non-limiting example, a concrete deck layer thickness on the order of eight inches is contemplated. 
     Deck panels  10  may be manufactured in whole or in part at one or more manufacturing facilities remote from the bridge construction site, and then shipped to the construction site for completion (if necessary) and installation. For example, deck plate  12  may be cut to size, shear studs  26  may be installed on deck plate  12 , ribs  14  may be roll-formed and cut to length, and ribs  14  may be welded to an underside of the deck plate at a steel fabrication facility having the necessary machine tools, cold roll-forming lines, and welding capability and fixtures. Deck panels  10  may be completed at the same or another facility by pouring concrete deck layer  15  to its full specified thickness and curing the poured concrete in a controlled environment. The completed deck panels  10  may then be shipped to the bridge construction site for installation. 
     In a second example, deck panels  10  may be manufactured as described in the first example above, except that the concrete deck layer  15  is partially poured (i.e. poured to a thickness that is a portion of the full specified thickness) and cured at an off-site facility, and then the partially completed deck panel is shipped to the bridge constructions site where the remainder of the concrete deck layer  15  may be poured and cured. 
     In a third example, metal components of deck panel  10  (i.e. deck plate  12 , ribs  14 , and shear studs  26 ) may be fabricated and welded at an off-site facility to form a subassembly, which may then be shipped to the bridge construction site, where the entire concrete deck layer  15  may be poured and cured. 
     As will be understood, the first example described above provides greater control over the entire manufacturing process by removing weather conditions, whereas the second and third examples facilitate shipping by reducing transport weight. 
     The present disclosure advances short span bridge construction by providing simplified steel orthotropic deck bridge panels which avoid costly details and design complexities that are unnecessary for short span applications. Moreover, the present disclosure allows for development of standardized orthotropic deck panels for short span applications, thereby leading to greater uniformity and certainty in costs to owners and contractors. This, in turn, provides opportunity to achieve cost savings from economies of scale. The present disclosure fills the void left by the current lack of “off the shelf” or “catalogue” orthotropic deck designs. In accordance with the present disclosure, standard orthotropic deck designs may be developed so that owners looking for a short span bridge solution or a bridge deck solution will have a limited set of choices. The standard designs may be characterized by predetermined calculations and performance ratings to make the decision process easier and give engineers confidence in the chosen design. 
     While the disclosure has been described in connection with exemplary embodiments, the detailed description is not intended to limit the scope of the disclosure to the particular forms set forth. The disclosure is intended to cover such alternatives, modifications and equivalents of the described embodiments as may be apparent to one of ordinary skill in the art.