Bridges – Transportable
Reexamination Certificate
2001-04-27
2003-05-06
Hartmann, Gary S. (Department: 3671)
Bridges
Transportable
C014S078000
Reexamination Certificate
active
06557201
ABSTRACT:
RIGHTS OF THE GOVERNMENT
The invention described herein may be manufactured and used by or for the Government of the United States for all governmental purposes without the payment of any royalty.
BACKGROUND OF THE INVENTION
The present invention relates generally to the structure and manufacture of modular bridges, and more particularly to modular bridge structures comprising fiber reinforced plastic (FRP) composite in a monocoque construction.
Conventional pedestrian bridges have typically been fabricated of steel, concrete, and wood. Existing composite bridge structures use truss designs in which pultruded composite members are linked together such that each member takes compression or tension similarly to comparable steel construction. Certain composite vehicular bridge structures use non-winding fabrication methods, each structure having many individual parts making up the load carrying substructure and the dead load contributing superstructure (side walls, railings and roofs) fastened together using fabrication processes which are very labor intensive. The resulting structure is typically capable of withstanding the structural load, but is not efficient in load carrying capability. One such structure requires that truss-built sides be transported to the bridge site and assembled with composite floor deck members using standard assembly methods and mechanical fasteners. These fasteners generate stress concentration sites. Because these structures are site specific and can be only partially factory fabricated, substantial disruption of traffic flow at the bridge site may result during bridge assembly.
Substantial improvements in modular FRP bridge structures are described in Bowman, United States Statutory Invention Registration H-1,872, published Oct. 3, 2000 (commonly owned with the invention described herein), the teachings of which are incorporated by reference herein, in which a method for fabricating a fiber reinforced composite bridge module includes in a preferred embodiment the steps of selecting a cross-sectional shape for the bridge module defined by an outer substantially tubular shell having a top side and a bottom side, and a floor deck near the bottom side and at least one keel beam beneath the floor deck and extending lengthwise of the outer shell, the outer shell, floor deck and keel beams defining a plurality of passageways along the module length, winding fiber and impregnating material on mandrels in a plurality of tubular sections defining the plurality of passageways, joining the sections in side-by-side relationship in an assembly substantially defining the selected cross-sectional shape of the module, winding fiber and impregnating material around the assembly to preselected thickness for the outer shell, and curing the fiber and impregnating material.
The present invention provides further novel improvements in composite bridge structures and fabrication methods by providing a low cost FRP composite bridge structure that includes a stressed skin (monocoque) structure, exploits the high specific strength and stiffness of FRP materials, omits nonstructural wall and roof members that add unnecessary weight, has a minimum number of mechanical fasteners and fewer potential structural failure sites, may be fabricated and assembled in modules of various cross sectional shapes, thereby avoiding weather conditions that may hamper installation at the bridge site or may compromise tolerances, and can be transported to the site completely assembled or in modules and installed with minimal disruption of traffic flow.
It is therefore a principal object of the invention to provide an FRP bridge structure and fabrication method.
It is a further object of the invention to provide an inexpensive, strong, lightweight, fatigue resistant and corrosion resistant bridge structure.
It is another object of the invention to provide a monocoque composite bridge structure.
It is yet another object of the invention to provide a method for fabricating a monocoque FRP composite bridge structure.
It is yet another object of the invention to provide an FRP bridge structure that can be fabricated in modular form in various cross sectional shapes and assembled to a desired length.
It is another object of the invention to provide a factory fabricated and assembled bridge structure for installation at a bridge site with minimal interruption of traffic flow.
It is yet another object of the invention to provide a bridge structure requiring substantially lower maintenance during bridge lifetime as compared to previously existing bridge structures.
These and other objects of the invention will become apparent as a detailed description of representative embodiments proceeds.
SUMMARY OF THE INVENTION
In accordance with the foregoing principles and objects of the invention, a monocoque fiber reinforced plastic composite modular bridge structure and fabrication method are described in which, in a preferred embodiment, one or more bridge modules of selected length and cross-section are fabricated by applying composite fabric over a mandrel of substantially the intended shape of the module, enclosing the mandrel and composite in a vacuum bag, infusing the fabric with resin, preferably utilizing the vacuum assisted resin transfer molding process, allowing the resin and fabric to cure, and applying finishing operations to the module for installation at a bridge site.
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Bowman Keith B.
Mollenhauer David H.
Hartmann Gary S.
Kundert Thomas L.
Scearce Bobby D.
The United States of America as represented by the Secretary of
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