Definitions

• This invention relates to a concrete and steel deck system used for bridge super-structures supported by beams. More specifically, this invention relates to a bridge deck system which utilizes the concept of post-tensioning in combination with a unique deck section design to achieve a significant weight reduction in the bridge deck and which provides adequate load carrying capacity.
• Concrete and steel structural combination bridge decks have been used for many years in an attempt to overcome the disadvantage of the low tensile strength of concrete and improve performance.
• Many of these concrete-steel composite bridge decks include a steel grid which is filled and/or covered with concrete.
• these decks use a large quantity of concrete which increases the material cost and weight of the deck.
• many of these bridge decks require reinforcing bars or expanded metal to strengthen the concrete. While these reinforcing members may help strengthen the concrete, they are also susceptible to corrosion which contributes to structural failures.
• a bridge deck including a concrete component having downwardly projecting protrusions.
• Structural support bars extending only longitudinally to bridge deck sections are partially embedded in the concrete component.
• Post-tensioning ducts are oriented perpendicular to the structural support bars, i.e. , lateral to the bridge deck sections, and extend through the concrete component.
• the post-tensioning ducts extend parallel to the downwardly projecting protrusions.
• Post-tensioning tendons are located in the post-tensioning ducts.
• the method of manufacturing includes precasting or casting-in-place deck panels or sections.
• the method includes depositing concrete around structural support bars and post-tensioning ducts such that the structural support bars and the post-tensioning ducts are embedded in the concrete and that a lower portion of the deck panel or section includes downwardly extending concrete formations and void sections free of concrete located between the formations.
• the post-tensioning ducts of adjacent deck panels are aligned and structurally coupled to form continuous coaxial ducts. Tendon members are positioned within the aligned ducts.
• the deck is post-tensioned after the concrete is permitted to substantially cure.
• Figure 1 is a general plan view of the post-tensioned structural support- concrete bridge deck system of the present invention
• Figure 2 is a detailed plan view of the post-tensioned structural support- concrete bridge deck system of Figure 1 ;
• Figure 3 is a vertical section taken through A-A of Figure 2;
• Figure 4 is a vertical section taken through B-B of Figure 2;
• Figure 5A is a vertical section of a post-tensioning duct and structural supporting bar connection
• Figure 5B is a vertical section of an alternate embodiment of a post-tensioning duct and structural supporting bar connection.
• the deck of the present invention is depicted in Figure 1 and is generally represented by reference numeral 10.
• the primary application of deck 10 is for, but not restricted to, bridge super-structures including beams of structural steel, concrete or wood.
• Bridge deck 10 includes a plurality of longitudinally spaced panels or sections 12 which rest upon and transfer forces to structural beams 14.
• structural beams 14 extend parallel to the roadway.
• the plurality of panels or sections 12 includes an end panel or section 12e at one end, at least one intermediate panel or section 12i, and an end panel or section 12e at the other end.
• panels or sections 12 include provisions so that bridge deck 10 may be post-tensioned by post-tensioning devices in the direction of arrows 15 to provide additional strength to deck 10.
• deck 10 yields many benefits.
• One such benefit is the ability to reduce the amount of concrete used in deck 10, since areas 17 on the lower portion of deck 10 are not filled with concrete.
• the invention allows deck 10 to maintain adequate strength while reducing material costs and weight. This necessarily reduces the dead load forces transferred to structural beams 14.
• each panel or section 12 includes a concrete component 18 and a skeletal frame.
• Skeletal frame includes a plurality of spaced steel structural support bars 16, schematically shown in Figure 2 by their center lines, oriented substantially pe ⁇ endicular to structural beams 14 and post-tensioning ducts 20 which extend through and are oriented pe ⁇ endicular to structural support bars 16.
• structural support bars 16 include holes 22 therein permitting the insertion of post-tensioning ducts 20 pe ⁇ endicular thereto.
• Post- tensioning ducts 20 may be made of plastic or metal and are attached to structural support bars 16 by a suitable method. For example, if ducts 20 are metal, they may be welded to structural support bars 16, as shown in Figure 5A. Another suitable method for attaching ducts 20 to bars 16 is to configure holes 22 to be web slotted and crimped, as shown in Figure 5B, so that a mechanical fit is achieved when duct 20 is inserted therein.
• These attachment methods are merely illustrative and those skilled in the art will recognize other methods and devices for attaching ducts 20 to structural support bars 16.
• Post-tensioning ducts 20 of adjacent sections 12 are coupled together to form continuous coaxial ducts which extend between both end sections 12e.
• Ducts 20 are coupled by a suitable coupling device, schematically indicated in Figure 3 by reference numeral 24.
• Coupling device 24 can take the form of duct tape and/or a pipe section which has an interior diameter slightly larger than the exterior diameter of ducts 20. However, other appropriate methods or devices could also be used. It is preferable that any coupling device 24 create a wate ⁇ roof seal which prevents water or concrete from entering the interior of duct 20.
• Concrete component 18 is shaped in a manner which results in deck 10 having a significant weight reduction over other bridge decks.
• concrete component 18 includes a smaller profile or thickness 26 throughout a significant portion of the deck 10 and includes haunches or downwardly depending protrusions 28 in other areas of deck 10.
• the elimination of concrete in the areas 17 between downwardly extending protrusions 28 amounts to a significant weight reduction and a significant reduction of dead load forces.
• many existing bridge decks weigh up to, or in excess of, 100-pounds per square foot while bridge deck 10 of the present invention weighs approximately 56- pounds per square foot.
• structural support bars 16 include an intermediate section 30 having outwardly extending lips 32. Lips 32 provide a supporting surface for pans 34 which are inserted between adjacent structural support bars 16 for providing a lower supporting surface for concrete component 18 until it cures. While, pans 34 are shaped to form the lower contour of concrete component 18, including downwardly depending protrusions 28, one in the art would recognize that other supporting elements and techniques could be used to support concrete component 18 until it cures.
• Structural support bar 16 also includes a lower horizontal section 36 and an upper section 38. Upper section 38 extends laterally outward from inte ⁇ nediate section 30 and includes lower horizontal surfaces 40. When concrete component 18 is poured, concrete extends under lower horizontal surfaces 40, and upon curing, forms a mechanical lock to prevent vertical separation between concrete component 18 and structural support bar 16.
• tendons 42 which may be high strength steel wires, strands, rods, or other highly stressable elements, are positioned within post- tensioning ducts 20. Tendons 42 are tightened, as described hereinafter, so that an already hardened concrete component 18 is pre-compressed. The ends of tendons 42 are anchored to post-tensioning anchorage elements 44. During the post-tensioning, deck 10 also shortens with respect to structural beams 14 because of the stressing of tendons 42. The post-tensioning prevents transverse, i.e. , transverse to beams 14, cracking of concrete component 18. The post-tensioning also eliminates the necessity for shear connectors between bars 16 and concrete component 18.
• Deck 10 is also mechanically connected to structural beams 14 to transfer shear forces thereto.
• Connectors 46 are affixed to beams 14 and vertical slots or holes 48 in concrete component 18 should accommodate connectors 46.
• holes 48 are filled by concrete to provide a mechanical lock between beam 14 and concrete component 18, via connectors 46.
• the type, number, and placement of connectors 46 can vary according to the size of bridge deck 10, spacing and material of beams 14, and numerous other factors.
• seals 50 may be placed between beam 14 and concrete component 18 to prevent the egress of concrete during this secondary operation.
• deck 10 To maximize the performance of deck 10, the prestressing force should be evenly distributed as much as possible along the width of the deck. This requires an end-zone area 52 of solid concrete with appropriate length and reinforcement. Deck 10 is most economical when the number of end zone areas 52 is kept to two. For multi-span structures, this results in a preference for continuous structures and uninterrupted decks.
• Deck 10 has the capability of being assembled with precast panels 12 or manufactured with sections 12 cast-in-place. If it is desired to manufacture deck 10 from precast panels, two end panels 12e and the required number of intermediate panels 12i are typically formed off-site. Panels 12 are formed by first assembling a skeletal unit. Structural support bars 16 are cut to a length preferably equal to the width of the bridge. Bars 16 are bored or stamped creating holes 22 to receive the post-tensioning ducts 20 and are bent to accommodate the vertical alignment of the deck, if necessary. Ducts 20 cut into lengths equal to the width of panel 12 are then mechanically attached to structural support bars 16 in a manner previously described.
• the duct-structural support bar connection should be reasonably rigid to hold until the concrete is poured and subsequently cures. Once the concrete has cured, the connection has no further structural pu ⁇ ose. Pans 34 are positioned on lips 32 of bars 16 and concrete is poured thereon.
• Precast panels 12 are then transported to the site and are arranged on structural beams 14 with ducts 20 of adjacent panels in horizontal alignment and with shear connectors 46 and vertical holes 48 in vertical alignment. Ducts 20 are then coupled. Post-tensioning tendons 42 are inserted through the continuous ducts 20. Concrete or grout is poured in a keyway, not shown, located between adjacent panels 12 and is permitted to substantially cure. Upon substantial curing of the concrete, tendons 42 are tightened and anchored to end panels 12e via post-tensioning anchorage elements 44. Then holes 48 are filled with concrete or grout.
• bridge deck 10 If it is desired to form bridge deck 10 using panels with a cast-in-place construction, a number of skeletal units are formed off-site, as described above. If the length of structural support bars 16 either exceeds 60.0-feet or is curtailed by transportation regulations, field splicing of the bars should be considered.
• the duct- structural support bar connection should be reasonably rigid and should hold during transportation and construction, however, as previously described, once the concrete has cured, the connection has no further structural purpose.
• the estimated weight of a 60.0-feet x 8.5-feet steel skeletal unit is 3,400-pounds, thus easily transportable by trucks.
• the skeletal units are positioned on the beams with the help of inorganic shims, then the duct-ends are coupled by either duct-taping or other appropriate method.
• Pans 34 are placed on lips 32 to support concrete to be poured and to form downwardly projecting protrusions 28.
• the concrete is poured and vertical edges of concrete component 18 are formed at the sides, in end-zone areas 52, and over beams 14.
• the concrete strength should preferably be at least 4,500-pounds per square inch at 28 days, although the hard-pack overlay is known to produce easily 6,000- pounds per square inch in three days.
• the concrete should preferably be wet-cured for 72-hours and protected by plastic cover for another 120 hours to reduce shrinkage.
• the post-tensioning tendons 42 can be pulled in and prepared for stressing.
• the deck shortens and moves with respect to the beams. If time permits the tendons may be restressed to reduce effective shrinkage and creep.
• the vertical edges of the primary concrete at holes 48 should be preferably smeared with a sand-cement slurry of appropriate mix.
• the secondary concrete should be cured in a manner similar to the primary concrete. Grinding of the concrete surface in the vicinity of the interface between the primary and secondary concretes may be required.
• concrete component 18 does not require reinforcing bars. Specifically, concrete component 18 is void of reinforcing bars above a horizontal plane defined by the top surfaces 54 of structural support bars 16, which is where many existing decks position reinforcing bars.

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• 1995
  • 1995-10-16 AU AU37323/95A patent/AU3732395A/en not_active Abandoned
  • 1995-10-16 EP EP95935227A patent/EP0856087A4/de not_active Withdrawn
  • 1995-10-16 CA CA002234766A patent/CA2234766A1/en not_active Abandoned

Non-Patent Citations (2)

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