Static structures (e.g. – buildings) – Machine or implement
Reexamination Certificate
1999-06-11
2001-10-02
Stephan, Beth A. (Department: 3635)
Static structures (e.g., buildings)
Machine or implement
C052S002150, C052S309170, C052S359000, C052S749100
Reexamination Certificate
active
06295782
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
This invention relates generally to concrete support structures and in particular, to stay-in-place forms (i.e., composite shells) for forming concrete support structures.
2. Description of the Related Art
Concrete columns are commonly used as upright supports for superstructures. Bridge supports, freeway overpass supports, building structural supports and parking structure supports are just a few of the many uses for concrete columns. Other concrete support members such as beams, walls, slabs, girders, struts, braces, etc. are employed to impart strength and stability to a large variety of structures. These concrete support structures exist in a wide variety of shapes. Typically, these concrete support structures have circular, square or rectangular cross-sections. However, numerous other cross-sectional shapes have been used including regular polygonal shapes and irregular cross-sections. The size of the concrete support structures also varies greatly depending upon the intended use. Concrete columns with diameters on the order of 2 to 20 feet and lengths of well over 50 feet are commonly used as bridge or overpass supports.
Conventionally, some concrete columns have been constructed by filling a cylindrical form having a network of rebar mounted therein with a concrete composition, allowing the composition to cure, and removing the form.
Also, in the past, elongate paper fiber tubes have been used to form concrete columns. The tubes are made by spirally winding several layers of strong fiber paper. The spirally wound paper is laminated along its seams with a special adhesive. The outside of the tube can be coated with hot wax for protection against adverse weather conditions. Concrete is poured into the tube and allowed to harden so as to form a column. After hardening, the tube is stripped away from the concrete column and scrapped.
Rather than paper tubes, reusable steel or wood forms can also be used. Concrete is poured into these forms and allowed to harden. After hardening, the form is removed from the concrete structure and can be used again.
All of these conventional concrete support structures are subject to deterioration of their long-term durability and integrity. Permeability of the exposed concrete by water can cause the concrete to deteriorate over time. When moisture is trapped in the concrete and freezes, cracks typically form in the concrete structural members. In addition, some of these conventional concrete support structures are located in earthquake prone areas but do not have adequate metal reinforcement or structural design to withstand high degrees of asymmetric loading.
More recently, composites have been used to repair and retrofit columns, beams, walls, tanks, chimneys and other structural elements. However, a need exists to use composites in a prefabricated form to strengthen new constructions, protect internal reinforcing steel, provide fiber reinforcement outside of a concrete layer, to provide better appearance features, and to solve the above problems.
SUMMARY OF INVENTION
A stay-in-place composite form in accordance with the present invention provides increased strength and durability to concrete support structures. The stay-in-place form can be used in prefabricated form or can be fabricated at the construction site, to strengthen new constructions.
The stay-in-place form includes a composite shell made up of fibrous fabric layers impregnated with a resin matrix. The composite shell has an inner wall surface defining an enclosure into which concrete may be poured and allowed to harden to form a concrete core. As the concrete is poured into the enclosure, the fibers in the fabric material elongate due to the weight of the concrete. Then, as the concrete dries, the fibers partially shrink back to compensate for shrinkage of the concrete.
In one embodiment of the present invention, the percentage of elongation of the resin matrix is greater than the percentage of elongation of the fibers. Typically, the percentage of elongation of the fibers and resin matrix prevents a gap from forming between the concrete core and the composite shell when the concrete shrinks.
A liner made of a water-impermeable material is affixed to the inner wall surface of the composite shell to protect the composite shell from alkalinity or other chemical products in the concrete core. This liner is in direct contact with an outer surface of the concrete core and either completely or partially surrounds the concrete core.
In one embodiment of the present invention, the stay-in-place form is manufactured using a rigid collapsible tubular member. The exterior surface of the tubular member is wrapped with the liner and then the fabric layers impregnated with resin are applied to the liner. Once the fabric layers cure, the tube is collapsed and removed from beneath the liner. What remains is a hollow stay-in-place composite form.
In yet another embodiment of the present invention, the stay-in-place form is manufactured using a mandrel. In such embodiment, the liner is applied to an exterior surface of the mandrel and then the fabric layers impregnated with resin are applied to the liner. Once the fabric layers cure, the liner and harden fabric layers are separated from the mandrel. Again, what remains is a hollow stay-in-place composite form.
In still another embodiment of the present invention, the collapsible tube or the mandrel is rotated about an axis while the fabric layer and the resin matrix is applied to the liner. Such rotation maintains the form of the tube and composite shell, and ensures that the resin is uniformly distributed. The rotation of the tube or mandrel continues until the resin impregnated fabric layers are fully cured.
These and other features and advantages of the present invention will become apparent by reference to the following detailed description and accompanying drawings which set forth several illustrative embodiments in which the principles of the invention are utilized.
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Glessner Brian E.
Gray Cary Ware & Freidenrich LLP
Stephan Beth A.
LandOfFree
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