Patent Publication Number: US-7716888-B2

Title: Composite decking system

Description:
This is a divisional patent application of U.S. patent application Ser. No. 11/125,655, filed May 10, 2005 now U.S. Pat. No. 7,334,373, which is a continuation application of U.S. patent application Ser. No. 10/269,491, filed Oct. 11, 2002, issued as U.S. Pat. No. 6,912,821, the disclosures of which are hereby incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention is directed to a structural assembly, formed primarily from composite matrix materials having reinforcing fibers in a polymer matrix, which may be used as a decking system or for other applications. 
   The need for alternative materials and configurations for load bearing decks has long been recognized. Conventional load bearing decks, such as for vehicular bridges, have historically been made from steel and concrete. While the construction techniques, and materials employed, have evolved over time for steel and/or concrete bridges, the construction process has proved to be very labor intensive, and the resulting structures have proven susceptible to corrosion and other degradations. 
   Partially in response to these cost and degradation issues, it has been proposed to use decking systems based on polymer composite matrix materials rather than steel and/or concrete. For instance, U.S. Pat. No. 5,794,402, incorporated herein by reference, proposes using a modular structural section formed from a polymer composite matrix to form sandwich-type load bearing deck panels for bridges. The &#39;402 patent proposes using a plurality of polymer composite matrix core members sandwiched between upper and lower facesheets to form modular sandwich panels. The core members are described as hollow tubes, typically with a trapezoid cross-section. While the patent indicates that the tube may be made using a pultrusion process, the actual fabrication of such tubes using pultrusion has proven difficult, primarily because pultrusion of hollow tubes, with a fully enclosed passage, is technologically difficult. In simple terms, pultrusion of such hollow shapes requires the use of floating dies, which are difficult to control during manufacture. In addition, the patent teaches that layers of reinforcing fibers with so-called 45°−45°−90° orientation should be used; however, use of such 45°−45°−90° orientation layers is very expensive. Thus, while the modular and polymer composite matrix approach of the 5,974,402 patent has some theoretical advantages over traditional steel and/or concrete approaches, it has proved difficult to manufacture. 
   Accordingly, there remains a need for alternate composite structural assemblies that are easier and/or less costly to make and use. Ideally, such an assembly should be capable of being used for applications other than a load bearing deck, but this is not strictly required. 
   SUMMARY OF THE INVENTION 
   A composite structural assembly of the present invention includes a baseplate having a plurality of laterally extending open channels and a top plate secured to the baseplate. The baseplate is formed from a first composite matrix comprising reinforcing fibers and a polymer resin, and includes a generally planar base section having first and second sides, a plurality of ribs extending from the first side of the base section, and the plurality of open channels disposed between the ribs and generally bounded by the adjacent ribs and the first side of the base section. In some embodiments, the ribs have a generally T-shaped cross-section and may have laterally extending cap sections disposed distal from and generally parallel to the first side of the base section. The top plate is formed from a second composite matrix of reinforcing fibers and a polymer resin, and is secured to the baseplate so as to generally enclose the channels. Preferably, the top plate is removably secured to the baseplate. Further, in some embodiments, at least one of the base section and the top plate are translucent. 
   The first composite matrix of the baseplate may include a plurality of first strands of reinforcing fibers, with the first strands oriented in a first direction generally parallel to the channels. The second composite matrix of the top plate may include a plurality of second strands of reinforcing fibers, with the second strands oriented generally perpendicular to the first strands. Either, or both, the first and second composite matrixes may optionally include a plurality of layers of matted reinforcing fibers having a random orientation. In preferred embodiments, substantially all the reinforcing fibers in the first composite matrix are either the strands oriented in the first direction or the matted reinforcing fibers having a random orientation. 
   The open channel configuration of the baseplate of the present invention allows for easy access within the channels of the base section, and therefore the sides of the ribs, thereby simplifying manufacture. In addition, the use of singly oriented strands of reinforcing fibers (optionally with the matted layers of random orientation) allows for much lower cost materials to be used. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a perspective view of one embodiment of the composite structural assembly of the present invention. 
       FIG. 2  shows a side view of a baseplate shown in  FIG. 1 . 
       FIG. 3  shows a more detailed view of a portion of the baseplate shown in  FIG. 2 . 
       FIG. 4  shows a partially exploded side view of the composite decking system of  FIG. 1  employed in a bridge application. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   One embodiment of a composite structural assembly of the present invention is shown in  FIG. 1 , and generally indicated at  20 . The assembly  20  includes a baseplate  30  and a top plate  80  secured to the baseplate  30 . As shown in more detail in  FIGS. 2-3 , the baseplate  30  includes a base section  40 , a plurality of ribs  50 , and a plurality of channels  60 . The base section  40  may be a generally flat, preferably rectangular, member with a top side  42  and a bottom side  44 . The ribs  50  extend up from the top side  42  of the base section  40  and may advantageously be of a generally T-shaped configuration with a column section  52  and a cap section  54 . The column section  52  extends generally perpendicularly away from the base section  40  and may have a generally rectangular cross-section, or tapered as desired. The joint between the column section  52  and the top side  42  of the base section  40  may be configured to reduce stresses and/or to simplify manufacturing, such as by being appropriately radiused. The cap section  54  is formed on the end of the rib  50  opposite the joint with the base section  40  such that the cap section  54  is spaced from the base section  40 . The cap section  54  may advantageously take the form of a generally flat element disposed generally perpendicular to the column section  52  of the rib  50  and generally parallel to the base section  40  of the baseplate  30 . Again, the joint between the column section  52  and the cap section  54  may be preferably configured to reduce stresses and/or to simplify manufacturing, such as by being appropriately radiused as shown. The cap sections  54  may include a plurality of holes  56  on their top sides for accepting fasteners (see  FIG. 4 ), as discussed further below. The ribs  50  are preferably spaced from one another a uniform distance, with the end ribs  50  being spaced a half-spacing from the respective ends of the baseplate  30 . 
   Between each pair of adjacent ribs  50  is a laterally extending open space referred to herein as a channel  60 . When viewed endwise, these channels  60  may be conceptually divided into two sections, a cavity  62  and a gap section  64 . The cavity  62  is disposed closest to the base section  40 , and is generally defined by the walls of the adjacent ribs  50  and the intervening portion of the top side  42  of the base section  40 . The gap sections  64  are the areas between the distal end portions of the ribs  50  and connect their respective cavities  62  to the area above the ribs  50 . Like the ribs  50 , the channels  60  advantageously run laterally from one edge of the baseplate  30  to the opposite edge. 
   The top plate  80  may take the form of a generally flat rectangular member of relatively thin thickness when compared with the height of the baseplate  30 . The top plate  80  may advantageously include a plurality of counter-sunk screw holes  82  aligned in rows to correspond with the distal ends (e.g., cap sections  54 ) of the ribs  50  of the baseplate  30 . The top plates  80  may have peripheral edges that are generally perpendicular to their main faces; however, one or more of the peripheral edges of the top plates  80  may alternatively be angled to create an overlapping joint when top plates  80  are abutted. 
   When the top plate  80  is secured to the baseplate  30 , the top plate  80  bridges the gap sections  64 , thereby enclosing the channels  60  in the baseplate  30 . Thus, the combination of the baseplate  30  and the top plate  80  may form a modular panel section with what may be referred to as a “sandwich” construction, with the top plate  80  and the base section  40  forming generally parallel surfaces, and the ribs  50  extending therebetween. 
   The main body of the baseplate  30  and the top plate  80  are formed from a composite matrix that includes reinforcing fibers in a polymer resin. For information about the reinforcing fibers and polymer resin matrix, attention is directed to U.S. Pat. No. 5,794,402. In the baseplate  30 , the composite matrix is formed from a plurality of strands  100  of reinforcing fibers that are disposed so as to be generally parallel with the channels  60 . Thus, in  FIGS. 2-3 , only the ends of the strands  100  are shown. The resin  120  forming the matrix surrounds the strands  100 . In addition, in order to simplify the manufacturing process, there may be a layer of reinforcing fiber “mat”  102  between each layer of strands  100 , or between each second layer of strands  100 , or each third layer of strands  100 , etc. The mat  102  consists of reinforcing fibers of the same or a different type that are randomly oriented rather than oriented in one, or only a few select, directions. 
   Likewise, the polymer composite matrix of the top plate  80  is formed from a plurality of reinforcing fiber strands  110  in a resin matrix, with optional layers of “mat”  112 . 
   The baseplate  30  and the top plate  80  may be formed by a process known in the art as pultrusion. In somewhat over-simplified terms, the pultrusion process involves the pulling of a plurality of strands (e.g., strands  100  or strands  110 ) through a shaping die where resin is added. The resulting product has a cross-sectional shape corresponding to the die. For the present invention, the baseplate  30  may be formed by pultrusion in the direction of the channels  60 , so that the strands  100  are aligned in the direction of pultrusion. The strands  100  in the baseplates  30  may be evenly distributed therein. However, it may be advantageous to have a non-uniform distribution of strands  100  within the baseplate  30 . For instance, it may be advantageous to have the density of strands  100  vary as a function of distance from the neutral axis of the baseplate  30 , as the strands  100  nearest the neutral axis do not add significantly to the bending strength of the baseplate  30 , but do add cost. Thus, the column section  52  of the rib  50  may have a lower density of strands  100  than the base section  40  and the cap section  54 . 
   The top plate  80  may also be formed by pultrusion. For the top plate, the direction of the strands  110  should also be in the direction of pultrusion. Note however, that strands  100  and strands  110  will ultimately be disposed in perpendicular orientations with respect to each other in most embodiments of the present invention, as described further below. 
   While pultrusion has been proposed before for bridge decking components, for instance in U.S. Pat. No. 5,794,402, the cross-sectional shapes employed have proved to be difficult to make. This is due to the fully enclosed nature of the proposed cross-sectional shapes. For instance, the “tubes 46” of  FIG. 3  in the &#39;402 patent have central passages that are fully enclosed by the surrounding walls. Such fully enclosed cross-sections are difficult to manufacture, particularly using a pultrusion method. In sharp contrast, the open channel configuration of the baseplate  30  of the present invention allows for easy access to the top side  42  of the base section  40 , thereby simplifying manufacture. 
   By way of illustrative example, the assembly  20  of the present invention may be employed as part of a vehicular traffic bridge. Various structural supports of a bridge, such as pillars and beams  12 , are installed using any conventional approach. Referring to  FIG. 4 , the relevant beams  12  in this example are oriented in the traffic flow (or longitudinal) direction  18 . The assembly  20  described above may then be installed over the beams  12 , with each baseplate  30  and top plate  80  preferably on the order of four feet by fifty feet, or more preferably eight feet by fifty feet. Before installing the structural assembly  20 , the top of the relevant beams  12  are preferably prepared with L-shaped clips (not shown) added to the edges of the beams  12  and optionally caulked on their upper surfaces. The space between the L-shaped clips and the top of the beam is eventually filled with grout  14 , with the weight of the decking system bearing on the beams through the grout  14  when the grout  14  has set. This approach to preparing the beams  12  is commonly referred to in the industry as “variable haunch,” and is well understood by those of ordinary skill in the art. 
   Thereafter, the baseplate(s)  30  are affixed to the beams  12  by any known method. For instance, each baseplate  30  may have suitable holes drilled or otherwise formed therein at suitable intervals for so-called Nelson studs  16  to be installed into the beams  12 . If used, the top of each Nelson stud  16  should extend up through the hole and into the corresponding cavity  62  of the baseplate  30 . Grout  14  is then pumped in to fill the cavity  62  around the Nelson stud  16 . Preferably, some non-load bearing dividers are added inside the channels  60  on either side of each Nelson stud  16  so that the grout  16  surrounding the Nelson stud  16  forms a small grout pocket, and does not fill the entire channel  60 . In addition, the grout  14  flows downward around the Nelson stud  16  and into the space between the baseplate  30  and the beam  12 . It should be noted that induced vibration of the structure may advantageously be used to aid in the flow of the grout  14  so that the grout completely fills the space between the baseplate  30  and the beam  12 . The adjoining baseplate  30  is then likewise installed, and so forth. The adjoining baseplates  30  are joined together, such as by using connecting plates  34  secured in place by suitable fasteners  36  seated in corresponding tapped holes in the edges of the baseplates  30 . While not shown, the connecting plates  34  may, if desired, rest in corresponding recesses formed along the edges of the baseplates  30 . At this point, the baseplates  30  are joined together and secured to the beams  12 . The top plates  80  are then secured to the baseplates  30 , with the reinforcing strands  110  of the top plates  80  oriented in the direction  18  of traffic flow and perpendicular to the strands  100  in the baseplates  30 . The top plates  80  may be glued to the cap sections  54  of the ribs  50 , but are preferably removably secured thereto by suitably spaced bolts. It may be advantageous to seal and/or install expansion joints between adjacent top plates  80  using any known technique. Finally, an additional layer of wear surface  81  may then be applied over the top plates  80 , if desired. Note that it may also be advantageous to apply some or all of the additional wear surface  81  to the top plates  80  during manufacture, prior to transporting the same to the installation site. 
   For the installation approach discussed above, it has been assumed that there is a one-to-one correlation between the number and size (area) of baseplates  30  and top plates  80 , with the two components aligned with one another to form a sandwich panel. Within such a panel, the long dimension of the baseplate  30  (e.g., fifty feet) is in the same direction as the long dimension of the top plate  80  (e.g., fifty feet), but strands  100  and strands  110  are oriented perpendicular to one another. However, the present invention should also be construed to cover arrangements where a given top plate  80  is secured to a plurality of baseplates  30 , thereby enclosing channels  60  from more than one baseplate  30 . In addition, some embodiments of the present invention may have the long dimension of the baseplates  30  running in one direction (e.g., transverse to traffic flow  18 ) and the long dimension of the top plates  80  running in a perpendicular direction (e.g., parallel to traffic flow  18 ). Whatever the orientations of the baseplate  30  and the top plate  80 , strands  100  and strands  110  should be oriented generally perpendicular to one another once installed. 
   In addition to bridge installations, the present invention is particularly suited to parking deck applications. The installation in parking decks may be carried out substantially as described above. In addition, the channels  60  may be used to house cables, conduits, utilities, heating elements, drains, and the like, particularly those channels  60  not used for Nelson studs  12 . Indeed, if the matrix of the baseplate  30  and/or the top plate  80  is translucent, then lighting elements may be installed in the unused channels  60 . Further, for the embodiments where the top plate  80  is removably secured to the baseplate(s)  30 , the relevant top plate  80  may be removed to provide access to the lighting, cabling, etc. for repair or replacement, and thereafter re-secured in place. 
   Of course, the structural assembly  20  of the present invention is not limited to bridge or parking deck applications, and may also be used for any applications where a load bearing panel is required or desired (e.g., in offshore oil platforms, floating platforms, etc.). Further, the structural assembly  20  may also be used in non-horizontal applications, such as vertical walls for buildings, noise walls, flood walls, and the like, where the structural assembly  20  is not substantially loaded. 
   By way of non-limiting example, a useful composite deck assembly  20  may be made with a baseplate  30  four feet wide by fifty feet long having a base section  40  of ½ inch thickness, three ribs  50  of seven inch height and spaced at one foot intervals, approximately ½ inch wide rib columns  52 , and four inch wide cap sections  54 . The base section  40  of the baseplate  30  may be made in an alternating layered fashion with four layers of strands  100  of sixty-four yield (a measure of length per unit weight of the reinforcing strand) E-glass at a density of eight strands  100  per inch, and five layers of E-glass mat  102 , both in an isophthalic polyester resin  120 . The column section  52  of the ribs  50  of the baseplate  30  may likewise be made in alternating layered fashion with three layers of strands  100  of sixty-four yield E-glass at a density of four strands per inch, and four layers of E-glass mat  102 , in the isophthalic polyester resin  120 . It should be noted that as understood by one of ordinary skill in the art, the layers of the column section  52  may be “stacked” in a different direction than the layers in the baseplate  30 ; for instance, the layers in the baseplate may be stacked “north-south” and the layers in the column section  52  may be stacked “east-west.” The cap sections  54  may be an alternating layered construction having four layers of strands  100  of sixty-four yield E-glass at a density of eight strands per inch, and five layers of E-glass mat  102 , in the isophthalic polyester resin  120 . The top plate  80  may likewise be four feet by fifty feet by ½ inch thick and made in an alternating layered fashion with four layers of strands  110  of sixty-four yield E-glass at a density of six strands per inch, and five layers of E-glass mat  112 , both in an isophthalic polyester resin  120 . The top plate  80  may be secured to the baseplate by ½ inch diameter bolts at two inch spacings. Both the baseplate  30  and the top plate  80  may be made using a pultrusion process. Such an arrangement should be suitable for supporting a HS-25 loading as defined by the American Association of State Highway and Transportation Officials (AASHTO). 
   The description of the structural assembly  20  given above has assumed that the baseplate  30  is disposed beneath the top plate  80 ; however, the relative positions of the two components may be switched without departing from the scope of the present invention. For example, while it may be less advantageous, the top plate  80  may be disposed below the baseplate  30 , with the ribs  50  extending downwardly. As such, the terms “baseplate” and “top plate” are not intended to be interpreted as implying relative locations, and are not intended to exclude such inverted arrangements. 
   The generic term “strands” have been used to describe the grouping of reinforcing fibers (filaments) indicated at  100 ,  110 . It should be noted that this generic term is intended to encompass what are alternatively known in the industry as “ends,” “tows,” “rovings,” and the like. Such strands may be made from glass fibers (e.g., S-glass, E-glass), aramid fibers, carbon fibers, graphite, and the like. 
   While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only some embodiments have been shown and described and that all changes and modifications that come within the meaning and equivalency range of the appended claims are intended to be embraced therein.