Internally trussed monolithic structural members
A prefabricated, monolithic, structural building panel of box-like configuration includes face, side and end members, all constructed of fiber reinforced concrete, the panel having a plurality of internal truss members, also constructed of fiber reinforced concrete, extending angularly between the panel face members. Forms for the casting of the structural components making up the panel are fabricated from a light weight, insulative material that is left in place within the panel after casting to provide heat and sound insulation.
This application claims the benefit of U.S. Provisional Patent Application No. 61/063,637 filed on Feb. 5, 2008, and the benefit of U.S. Provisional Patent Application No. 61/069,734 filed on Mar. 17, 2008.
BACKGROUND OF THE INVENTION1. Technical Field
This invention relates generally to internally trussed, structural members constructed of glass fiber reinforced concrete and to methods for fabricating those structural members.
More specifically, this invention relates to light weight, unitary, structural members such as building panels and beams that are fabricated entirely of fiber reinforced concrete with a plurality of integral truss members of the same fiber reinforced concrete extending between faces of the structural member to divide the spaces between those faces into compartments.
This invention further relates to methods for manufacturing the structural members and for incorporating insulating materials that fill the compartments therein.
2. Description of Related Art
It is common in the industry to employ either hollow core or solid concrete building panels to form walls, floors and roofs of structures. Solid concrete panels with steel reinforcement are ordinarily used in weight-bearing applications as well as in those requiring substantial structural strength to withstand high wind loading and the like. Such solid panels are extremely heavy, are poorly insulating, and are expensive and energy intensive in their production and transportation from the manufacturing facility to the job site.
Prefabricated hollow core panels in which part of the interior concrete is replaced by void space or insulating fill material are often presented as an alternative to solid panels, and examples of such panels are described in U.S. Pat. Nos. 5,966,896 to Tylman, U.S. Pat. No. 6,718,712 to Heath, U.S. Pat. No. 6,898,908 to Messenger et al, and to U.S. Pat. No. 6,955,014 to LeJeune et al. Each of the insulated or hollow core panels described in the patents have inherent disadvantages as do all other such panels known to the inventor. Among common disadvantages in the manufacturing of such panels are problems in maintaining structural strength of the panel after attaching an outer panel face to its mating inner face through a void space or fill material, difficulties in maintaining the fill or insulating material in proper position during casting, and the requirement for use of metal reinforcing or to employ special expensive cements in order to obtain sufficient strength in tension. Prior art panels and other structural members commonly require multiple complex elements, and a plurality of different materials, have unnecessary weight, use connecting means that transmit heat energy through the panels, and require complicated fabrication procedures. Also, many such panels lack structural or shear strength along one or more axes.
The invention described in this application provides light weight, high strength, monolithic structural members and a simple and novel method for their fabrication.
SUMMARY OF THE INVENTIONA monolithic structural member, such as a beam or a panel, includes a pair of generally parallel face members that are spaced apart and connected by means of truss members extending between the two faces. A pair of side panels, together with a pair of end panels, complete the structural member. All structural components, face members, trusses, and side and end panels, are fabricated entirely of fiber reinforced concrete to form a unitary monolithic unit. In a preferred embodiment, the truss members extend angularly between the face members and, optionally, between the end panels as well. The components of the structural member are shaped by pouring a slurry of fiber reinforced concrete around a form array that is constructed of a shaped, light weight insulative material, preferably a foamed plastic, and after casting, the forms are left in place to provide heat and sound insulation by filling the compartments or void spaces that would remain after stripping away a conventional form.
This invention comprises a high strength, light weight, internally trussed, and monolithic structural member, such as a beam or building panel, that is cast from fiber reinforced concrete, and further comprises a method for the fabrication of that panel. Portland cement concrete is a relatively brittle material having substantial strength in compression but little strength in tension or shear and thus does not have sufficient strength to be employed in this invention. It has been found that a fiber reinforced concrete mixed to form a castable slurry and containing a sufficient quantity of high-strength reinforcing fibers to impart a significant degree of tensile strength to the resulting composite is suitable for use in the manufacture of the herein described structural members.
A first embodiment of this invention, comprising a building panel, is shown in
Although truss member 16 may be a simple rectangular plane, it is preferred that it be configured as is illustrated in
A unique feature of this invention is the use of a shaped, light weight insulative material to construct a form assembly, or structured array, for the casting of the structural components making up a structural member such as panel 10. After casting, the form assembly is left in place, thereby simplifying the construction of the forms, avoiding the step of stripping the forms from the cast composite, and providing heat and sound insulation by filling some, or all, of the compartments or void spaces that would remain after conventional casting in which the forms are stripped. The insulative material from which the form arrays are constructed need have only sufficient compressive strength to support the weight of the fiber reinforced concrete making up the panel, which allows the use of a variety of materials for the fabrication of the forms. Preferred form materials include foamed plastics such as those of polystyrene, polyurethane, and isocyanurate, and light weight mineral aggregates such as perlite or vermiculite in a concrete or other adhesive matrix. Selection of a particular form material is governed, at least in part, by the properties that are desired or required in the finished panel. Relevant properties may include the panel weight, the level of thermal insulation or sound absorption desired, and the fireproofing and toxicity requirements of a particular installation.
The thickness of spacers 37 and their placement on the billet faces determines the dimensions of each individual truss member or rib 23, best shown in
Fabrication of a structural member, such as the building panel that has been described, may be accomplished by use of a simple, open-topped, box mold sized to the desired length and width of the structural member and having a depth equal to the member thickness. A layer of fiber reinforced concrete is then poured into the mold box and is leveled, as by vibration, to form a first, or bottom, panel face. Mold assembly 30 is then placed atop the panel face layer and additional fiber reinforced concrete slurry is poured into the mold to fill the channels between billets and spacers and to form side and end panels from the spaces at the ends and sides of the mold assembly as well as to cover the top of the mold assembly to form a second, or top, panel face. It does not matter whether the entire panel is poured in one step or if the various segments are poured sequentially so long as the delay between sequential pours is sufficiently brief as to preclude any significant degree of curing of the first poured batch It is often advantageous to subject the mold box to vibration during the casting process as that tends to increase the homogeneity of the resulting casting and reduces the possibility of voids remaining around the mold assembly. The resulting structure is then allowed to cure, resulting in a single piece, monolithic panel having the mold assembly encased therein.
Structural members of this invention, such as the described building panels, require far less concrete than do concrete structural members of conventional design and construction while equaling and often exceeding the strength of those conventional members. In preferred embodiments of this invention, the total volume taken up by the mold assembly greatly exceeds the volume of the fiber reinforced concrete making up the remainder of the structural member. Because of the very low specific gravity of foamed plastics and like materials from which the mold assembly is made as compared to concrete, there is a corresponding and generally equivalent reduction in weight of the resulting structural member. In most cases, the volume of the mold array will exceed 75% of the total volume of the structural member, reducing the weight of the resulting structural member by approximately the same amount as compared to a structural member of conventional construction. In many applications, the volume of the mold array may exceed 85% of the total volume of the structural member while at the same time equaling or exceeding the strength and performance of the conventional structure that it replaces. Important savings are thereby realized in materials cost through lessened concrete use, and substantial savings in transportation costs are also realized in the shipment of fabricated structural members from a production site to a use site.
Because the fiber reinforced concrete used in this invention is impervious to corrosion, the reinforcing fibers may be laid at, or even concentrated at, the panel surface to provide high tensile strength at those panel areas that are most highly stressed under flexural loading. Ordinary concrete, on the other hand, has insufficient tensile strength to withstand flexure stress while steel reinforcement cannot be placed near the surface of a concrete member because of its vulnerability to corrosion.
Turning now to
In a preferred embodiment of this invention, areas 57 comprise generally rectangular billets fabricated of a light weight insulative material, preferably a foamed plastic. Fabrication of the panels 50 may be accomplished in the same general fashion as described in the fabrication of panel 10, employing an open-topped box mold sized to the desired panel length and width and having a depth equal to the panel thickness. A layer of fiber reinforced concrete is put down on the mold floor to form a first, or bottom, panel face. Billets 57 are then placed atop the concrete layer in a regular parallel pattern with the spaces between billets defining the dimensions of the side and end panels and the thickness of the vertical ribs 52. Additional fiber reinforced concrete slurry is then poured into the mold to fill the spaces between and at the ends and sides of the billets and to form a second, or top, panel face. The resulting structure is then allowed to cure, resulting in a unitary and monolithic panel having the insulating mold billet members 57 encased therein.
Ribs 52 act as internal trusses along the longitudinal axis of the panel and impart great rigidity to the panel across its axial span. The panel is able to bear large facial and axial loads as well as high longitudinal shear loads but, unlike panel 10, is unable to bear large shear loads across the panel width, or perpendicular to the panel longitudinal axis.
In a preferred embodiment, ribs 52 are configured as shown in
Referring now to
This same general approach taken in the fabrication of panels is equally applicable to the construction of internally trussed beams and columns as is illustrated in
As can readily be appreciated from this view, the internal truss system that is obtained according to this invention provides high strength and rigidity along every axis of the resulting structural member.
A further illustration of a building panel of this invention and of its fabrication is set out in the following example.
EXAMPLEA full-size, structural building panel conforming to the invention embodiment of
The fibers that may be employed to reinforce the concrete used to manufacture the building panel of this invention include all of those that are stable in the strongly alkaline concrete environment and that impart sufficient strength to the composite. Exemplary fibers that are suitable for use in this invention include alkali resistant (zirconia) glass, corrosion resistant metal fibers, graphite, and the like. Of these various fibers, zirconia glass fibers are presently preferred. The fiber level, or concentration in the concrete, will ordinarily be in the general range of 1% to 5% by volume, but that can vary depending upon the desired characteristics of the resulting concrete.
Panel surfaces, both exterior and interior, may be textured and/or pigmented to provide a decorative finished appearance to the panel surfaces. That capability allows the modular construction of finished commercial and residential spaces when both exterior and exterior surfaces are so treated.
Many other variations in the designs and fabrication techniques that are set out in this disclosure will become apparent to others skilled in this art, and such variations are specifically included within the scope of this invention.
Claims
1. An internally trussed, unitary, structural member comprising:
- a first and a second face member, each said member consisting essentially of fiber reinforced, Portland cement concrete, said face members being generally planar and parallel one to the other;
- a first and a second edge member, each said member consisting essentially of fiber reinforced, Portland cement concrete, said edge members extending between the face members at a border thereof to define an enclosed space; and
- a plurality of truss members extending between said first and second face members, each said truss member consisting essentially of fiber reinforced Portland cement concrete.
2. The structural member of claim 1 including truss members that extend between said first and second edge members.
3. The structural member of claim 1 wherein the combined volume of said face members, said edge members, and said truss members is less than 25% of the volume of said enclosed space.
4. The structural member of claim 1 wherein the volume that is not occupied by said face members, edge members, and truss members comprises a light weight, solid material shaped to form a mold assembly that defines said truss members.
5. A unitary mold assembly for fabrication of an internally trussed structural member manufactured entirely of fiber reinforced, Portland cement concrete comprising:
- a plurality of form billets arranged in a planar and parallel relationship to create a form assembly, all of said billets having the same shape and size, each said billet connected to the next adjacent billet through a plurality of spacer means, said spacer means arranged on the billet surfaces to define a plurality of channels, each said channel extending from one side of said form assembly to its opposing side.
6. A method for fabricating a structural member comprising:
- providing an open-topped box mold sized to the desired length and width of the structural member, said mold having a depth equal to the thickness of said structural member;
- pouring a slurry of fiber reinforced Portland cement concrete into said box mold and leveling said slurry in the box mold bottom to form a first member face;
- placing a form assembly atop the first member face, said form assembly comprising a plurality of form billets, all of said billets having the same shape and size, each said billet connected to the next adjacent billet through a plurality of spacer means, said spacer means arranged on the billet surfaces to define a plurality of channels, each said channel extending from one side of said form assembly to its opposing side;
- adding additional concrete slurry into said mold box to fill the channels between billets, to cover the mold assembly, and to form a second member face; and
- allowing the concrete to cure to thereby produce a single piece, unitary structure having the mold assembly encased therein.
7. The structural member of claim 1 wherein the fibers employed to reinforce said Portland cement concrete are stable in a strongly alkaline environment.
8. The structural member of claim 7 wherein the fibers employed to reinforce said Portland cement concrete are selected from the group consisting of zirconia glass, corrosion resistant metal fibers, and graphite and wherein the fiber concentration in the Portland cement concrete is in the range of 1% to 5% by volume.
9. The structural member of claim 1 wherein said truss members are disposed parallel one to another, and extend between said face members.
10. The structural member of claim 9 wherein each said truss member includes an upper truss beam and a lower truss beam, each of said truss beams extending the length of said truss member, said upper and lower truss beams connected by a plurality of rib members that extend between said upper and lower truss beams.
11. The structural member of claim 10 wherein alternate ones of said rib members are disposed parallel one to another and extend diagonally between said truss beams to form a triangular rib lattice.
12. The structural member of claim 10 wherein said upper and lower truss beams are integral with said upper and lower face members respectively.
13. The mold assembly of claim 5 wherein said billets and said spacer means comprise a foamed plastic.
14. The mold assembly of claim 13 wherein said foamed plastic is selected from the group consisting of polystyrene, polyurethane, and isocyanurate.
15. The mold assembly of claim 5 wherein said billets and spacer means are fabricated of a light weight mineral aggregate in an adhesive matrix.
16. The mold assembly of claim 15 wherein said light weight mineral aggregate is selected from the group consisting of perlite, vermiculite, and mixtures thereof.
17. The mold assembly of claim 5 in which the mold assembly has a top side and a bottom side and wherein said billets are triangular in cross-section, each billet having a base and two sides, said billets disposed such that a first billet is positioned with its base plane and generally parallel with the mold assembly top side and the adjacent billet positioned with its base plane and generally parallel with the mold assembly bottom side.
18. The mold assembly of claim 17 wherein the cross section of each said billet is in the shape of an isosceles triangle having a base angle ranging from about 30° to about 75°.
19. The mold assembly of claim 18 wherein said base angle ranges from 45° to 60°.
20. The mold assembly of claim 17 wherein said spacer means are triangular is shape, are of uniform size and thickness, and are equally spaced along said billets.
21. The mold assembly of claim 20 wherein the bases of adjacent triangular spacers are shaped such that they fit flush and level with the bases of adjacent billets.
22. The method of claim 6 wherein said form billets are triangular in cross section, each billet having a base and two sides that meet at an apex, said billets being disposed such that a first billet is positioned with its base plane and generally parallel with the bottom of said box mold, and the next adjacent billet positioned with its apex plane and generally parallel with the top of said box mold.
23. The method of claim 22 wherein said spacer means are triangular in shape, are of uniform size and thickness, and are equally spaced along said billets to form channels of uniform cross section.
24. The method of claim 23 wherein the total volume of said mold assembly is more than half of the total volume of said structural member.
25. The method of claim 23 wherein the total volume of said mold assembly is more than three-quarters of the total volume of said structural member.
26. The method of claim 6 wherein the fibers employed to reinforce said Portland cement concrete are stable in a strongly alkaline environment.
27. The method of claim 6 wherein the fibers employed to reinforce said Portland cement concrete are selected from the group consisting of zirconia glass, corrosion resistant metal fibers, graphite, and mixtures thereof, and wherein the fiber concentration in the Portland cement concrete is in the range of 1% to 5% by volume.
Type: Application
Filed: May 5, 2008
Publication Date: Aug 6, 2009
Inventor: Michael P. Gembol (Reston, VA)
Application Number: 12/151,188
International Classification: E04B 1/00 (20060101); E04G 11/06 (20060101);