Composite steel-wood floor structure

Abstract

Disclosed is a floor structure comprising: an upper surface arranged in parallel to a lower surface; and one or more channels disposed vertically between upper and lower surfaces and longitudinally extending along the upper and lower surfaces, each of the one or more channels having a top and a bottom.

Description

BACKGROUND OF THE INVENTION

A structural, weight-bearing floor system is constructed by laying a floor deck across a number of underlying, supporting joists or beam members. The deck may be made of a variety of different materials, however generally the deck will be constructed of wood, such as wood panels set to lie across foundation walls or beam members, so as to replace the use of subfloor panels set upon underlying wood joists.

In designing a floor structure system, a number of factors are important, notably that the combination of the wood panels and underlying joists create a strong, stiff floor. The floor should also have other important features, for example, it should be relatively easy to install as well as be capable of accommodating building services such as HVAC, plumbing, as well as fiber optics and other communication cables. Yet another important factor that has been insufficiently addressed in past floor structures is that the floor structure should be compatible with potential floor coverings to be used over it.

Particularly desirable is a floor structure that is integrated as a single piece unit that can be lifted by a crane and installed in place. By preparing the floor in this manner, it needs only to be installed (rather than assembled) once it is delivered on site. Accordingly, because the floor does not have to be assembled on site, it can be manufactured in a plant, which allows greater realization of economies of scale, more rigorous quality control, and means that production of the floor structure is not interrupted by inhospitable weather. Accordingly, there is a need in the art for a floor structure that is integrated into a single unit capable of being prefabricated and mass produced.

Several prefabricated floor structures have been proposed in the past. For example, U.S. Pat. No. 6,244,008 discloses a pre-assembled floor composed of layers of steel, insulation and cement. While this floor is capable of being pre-assembled it has a number of drawbacks, notably a lack of workability, difficulty of use and a general incompatibility between its cement surface and floor coverings to be installed on this surface.

Another structural panel is proposed in U.S. Published Patent Application No. 2002/0059757. This published patent application discloses a modified stress-skin panel (a type of prefabricated structural panel). These panels include spaces for components such as heater ducts. However, these panels are not really applicable for forming floors, they are actually meant to form wall panels and in most cases would be inapplicable for forming floor structures.

Accordingly there remains in the art a need for a floor structure that is capable of being pre-fabricated or preassembled, is compatible with desired floor coverings, and relative to comparable structures is easy to set in place and install.

BRIEF SUMMARY OF THE INVENTION

The present invention includes a floor structure comprising: an upper surface arranged in parallel to a lower surface; and one or more channels disposed vertically between upper and lower surfaces and longitudinally extending along the upper and lower surfaces, each of the one or more channels having a top and a bottom.

DETAILED DESCRIPTION OF THE INVENTION

All parts, percentages and ratios used herein are expressed by weight unless otherwise specified. All documents cited herein are incorporated by reference.

As used herein, “wood” is intended to mean a cellular structure, having cell walls composed of cellulose and hemicellulose fibers bonded together by lignin polymer.

By “laminated”, it is meant material composed of layers and bonded together using resin binders.

By “wood composite material” or “wood composite component” it is meant a composite material that comprises wood and one or more other additives, such as adhesives or waxes. Non-limiting examples of wood composite materials include oriented strand board (“OSB”), laminated veneer lumber (LVL), oriented strand lumber (OSL), structural composite lumber (“SCL”), waferboard, particle board, chipboard, medium-density fiberboard, plywood, and boards that are a composite of strands and ply veneers. As used herein, “flakes”, “strands”, and “wafers” are considered equivalent to one another and are used interchangeably. A non-exclusive description of wood composite materials may be found in the Supplement Volume to the Kirk-Othmer Encyclopedia of Chemical Technology, pp 765-810, 6^th Edition, which is hereby incorporated by reference.

In most construction a floor is typically built upon a conventional foundation (for the first story), which supports a floor comprised of a series of parallel, spaced apart floor I joists, with a wood decking fastened upon them. In the present invention, however, the floor is not built on site, but instead is built in floor structure segments elsewhere (such as in a manufacturing plant or similar facility) and transported to the construction site where it is lifted into place and installed by use of a crane during construction of a building. The structural components of the floor system are combined in the unit, such that no floor joists are required to hold up the structure. This floor structure has yet additional advantages as well because it is capable of accommodating the infrastructure to hold a variety of building services such as HVAC ducts, plumbing pipes, and conduits for fiber optic cables as well as other types of communication cables.

The configuration of the floor structure is illustrated in FIG. 1. The floor structure 2 comprises an upper surface 5 arranged in parallel to a lower surface 8. One or more channels 14 are disposed vertically between the upper surface 5 and lower surface 8 and these channels extend longitudinally along the length of the upper surface 5 and lower surface 8 as shown in FIG. 1. Each of the one or more channels have a top 17 (attached to the upper surface 5) and a bottom 20 (attached to the lower surface 8).

The upper surface 5 and lower surface 8 of the present invention will typically be constructed of one or more wood composite floor panels. For example, the entire top surface may be composed of one piece of OSB that is 20 feet long by 4 feet wide. The bottom panel would also be one piece of the same length and width as the top surface. Alternatively panels of other dimensions may be used. The wood composite is preferably OSB material, but known wood composite materials as mentioned above may be used also. For reasons that are discussed in greater detail below, there is a sufficient amount of reinforcement in the lower surface due to the arrangement and reinforcing effects of the channels, that the wood composite boards which form the lower surface 8 can be made thinner than the wood composite boards which form the upper surface 5. The wood composite boards which form the lower surface 5 have a thickness of about ⅜ inch to about ⅞ inch, preferably about ½ inch to about 23/32 inch, while the wood composite boards which form the upper surface 8 have a thickness of between ½ inch to about 1 inch, preferably about 19/32 inch to about 23/32 inch.

The present floor structure also includes one or more channels 14, which are meant to accommodate a variety of different building services such as HVAC equipment, telecommunication cables and wiring, plumbing and other important building services. In one embodiment, the channels have stiffeners 29 spot welded to the end of each channel, with holes formed in the stiffeners 29 to allow the passage of the cables, wiring, and plumbing along the length. The channels may have formed openings in the sides to accommodate the passage of cables, wiring, and plumbing along the floor's width.

When assembled together, the width of the floor structure is from about 12 inches to about 96 inches, preferably from about 24 inches to about 48 inches, while the length of the floor structure is about 96 inches to about 300 inches, preferably from about 120 inches to about 240 inches.

The channels 14 illustrated in the present drawing are shown with sloped walls forming a U cross section, however, the shape of each of the channels can vary according to the specific design necessary for implementation of the floor structure. So in addition to the channels having a U cross section, the channels may also be formed in a rectangular cross section or a V cross section, or some other suitable shape. FIG. 1 shows one embodiment of the present invention with channels 14 made from curved, bent galvanized steel, 10 gage to 20 gage, preferably 12 gage to 18 gage. The channels may optionally be fitted with stiffeners along their length to reinforce the channels. The stiffeners may be made from stamped galvanized steel 10 gage to 20 gage, preferably 12 gage to 18 gage and shaped to fit snugly inside the area of the channel at 2 foot to 8 foot intervals (preferably 4 foot intervals) and at the supporting ends. As mentioned above, these channels, and the spaces between the channels, are useful for accommodating HVAC ducts, plumbing pipes, and fiber optic cables as well as other types of communication cables.

Additionally, interlocking cams 35 may optionally be placed along the longitudinal edges of the floor structure in order to provide a better mechanical grip between adjacent and adjoining floor structure units. An additional optional feature shown in FIG. 1 is a blocking member 11, which is disposed vertically between the upper surface 5 and lower surface 8, and permanently affixed thereto. The blocking member may be a piece of solid wood lumber, a manufactured I-joist, a wood composite material or some other suitable material.

A particular advantage of the present invention is that the disclosed floor structure allows for the disentanglement of the building services, which have relatively shorts life spans (e.g., 10 years) from the floor and building itself, which should have a much longer life span (e.g., over 100 years). Utilizing the presently disclosed floor structure allows for the building services to be easily upgraded in the future when necessary or when more sophisticated equipment becomes available.

Yet another advantage of this arrangement as found in the present invention is that it also increases the strength performance of the floor structure because the larger footprint of the channel on the lower wood composite board 5 acts to reinforce the floor structure in the area where the high tension forces make the floor structure more likely to fail (i.e., the lower wood panels that form the lower surface of the floor structure) than at other areas of the floor structure.

As mentioned above, the channels 17 must be securely attached to the upper and lower wood 5, 8 composite boards, with nails, screws, adhesive glue, or other permanent fasteners as described above. The channels 17 may additionally have extending tabs 23 (See FIG. 2a) to facilitate attachment of the channels to the upper surface 5. Fasteners may be selected from readily available nails and fasteners such as the Primeguard Plus™ exterior screws available from PrimeSource Building Products, Inc., Carrollton, Tex.

In addition, an adhesive may also be used to ensure that the channels are sufficiently fastened to the upper and lower composite boards so that the channels can bring strength reinforcing properties as described above. This adhesive is typically applied in beads of a typical width of ¼ inch, but wider or thinner depending on the specific individual needs. The adhesive resin used to from the bead in the present invention may be selected from a variety of different polymer materials such as epoxies, phenolic, resorcinol, acrylic, polyurethane, phenolic-resorcinol-formaldehyde resin, and polymeric methylenediisocyanate (“pMDI”). The selection will largely depend on the cost and performance targets specified. Some examples of specific resin systems that are suitable for use in the present invention include ISOSET® UX-100 Adhesive, available from Ashland Specialty Chemical Company, Columbus, Ohio. ISOSET is a two-part resin system, based on a 100-percent solids polyurethane adhesive, blended with conventional ISOSET adhesive. This system offers faster strength and faster complete cure times, while providing excellent strength performance. Particularly preferred is PL® Premium subfloor adhesive available from PL Sealants and Adhesives, Mentor, Ohio.

Additional options or features can be added to the wood board as well. For example, tongue and groove surfaces (not illustrated in figures) can be added to the edges of the floor structure to ensure good, tight fits with adjacent floor structure pieces. Similarly, interlocking cams (not illustrated in figures) can be formed on the longitudinal edges to pull the panels tight during assembly. Also four machined holes (not illustrated in present FIG. 1), two holes at each panel end, may be added to the lower panel as a means of easily attaching cables for lifting and lowering the panel into place with a crane.

When the floor structures are fully assembled so that the webstocks are disposed between the upper and lower levels (thereby interconnecting the panels) and the channels are disposed in the space between the upper and lower levels, then the overall thickness of the floor structure will be about 8 inches to about 24 inches, preferably about 10 inches to about 14 inches.

The invention will now be described in more detail with respect to the following, specific, non-limiting examples.

EXAMPLE 1

Present Invention

Floor structures were prepared according to the present invention as follows. The floor structures were four feet wide, 20 foot long, and 9.5 inches thick. The upper and lower composite wood boards were 23/32″ AdvanTech boards. Between the upper and lower composite wood boards were arranged three channels, cross sectional illustrations and dimensions of these channels are shown in FIG. 2. The channels themselves were 20 feet long, and stiffeners at each end and along the channels at a longitudinal spacing of one stiffener for every four feet.

Screws were inserted every 8-inches as indicated by in FIG. 2 to fasten the metals channels to the upper and lower composite wood boards. The screws used were Primeguard Plus™ exterior screws. As can be seen the metal channel in FIG. 2b is in the shape of an isosceles trapezoid, with the top of the channel 14 having a length of seven inches, the height of the trapezoidal channel 14 being 8 inches, the non-parallel sides of the trapezoidal channel form a 78° angle with the base 45 of the trapezoidal channel. The extending tabs 23 are approximately 1.5 inches long.

Shown in FIG. 2b is a stiffener 29 to be placed inside the channel 14, with a hole 45 (as described above) placed in the exact center of the stiffener 29.

Additionally, to further secure the channels to the composite wood boards a ¼ inch bead of PL premium adhesive was used on each of the tabs shown in FIG. 2, and additional three ¼ inch beads were applied to the bottom of the channel contacting the lower wood board as shown in FIGS. 1 and 2. All of these beads ran the entire length of the floor structure.

EXAMPLE 2

Prior Art

A conventional floor structure was built with concrete foundation walls made according to size and set at the proper spacing. The 2×4 plate was bolted down to the top of the concrete supports, and the rimboard was placed on the plate and attached thereto with nail fasteners, at an industry-wide standard spacing for nails of every 12″, I Joists were installed on the rimboard and AdvanTech floor sheathing was fastened to the I Joists with a continuous bead of polyurethane construction adhesive. The I joists were made from ⅜ inch OSB webstock and solid wood lumber flanges that were 1.5 inch by 2.5 inch.

Examples 1 and 2 were then tested to measure the stiffness of the flooring structures and assess whether they are sufficiently stiff as to avoid undesirable vibrations. A drop weight apparatus was used to apply a repeatable dynamic loading to the floor systems. Two accelerometers and two linear variable displacement transducers (LVDTs) were installed at the center spans, one at the center of the width, and one at one edge. The drop weight apparatus was placed at the center of the floor at mid-span.

The fundamental frequency and averages for each test performed on the concepts were measured as follows. Averages were taken over three samples.

	TABLE 1
		Fundamental	Deflection at 318 lb
	Concept	Frequency	Total (in)
	Example 1	10.93	0.07
	(Present Invention)
	Example 2	14.00	0.07
	(Prior Art)

As can be seen in table I, the present invention performed comparably to the prior art, with a vibration performance that was only slightly lower but still comparable to the prior art—higher fundamental frequency measurements are indicative of a better “feel” to the floor. It is likely that the fundamental frequency could be increased by using stiffer panels or stiffer channel sections. Deflection under 318 lbs is another measure of the stiffness and firmness of the floor. The deflection of the present invention was very similar to the deflection experienced by the prior art, another indicator of comparable stiffness performance.

Each set of the above floor structures were then subjected to static bending tests using a universal test frame from Measurements Technology Inc., Roswell, Ga. following the test protocols outlined in ASTM D 198 (“Standard Test Methods of Static Tests of Lumber in Structural Sizes”) and ASTM D 5055 (“Standard Specification for Establishing and Monitoring Structural Capacities of Prefabricated Wood I joists”).

The static bending tests were performed on small specimens of the floor sections, specifically, 8-ft long and 11-in wide sections of the floor structure of the present invention was fabricated as per above and each with two different gauge thicknesses (12 gauge and 18 gauge) of the steel channels. Also, two 8-ft long and 11-in wide sections of conventional floor structure were made according to the prior art, one with I joists made from solid wood Lumber, the other with I joists made from LVL. The specimen was loaded on a three-point load test frame at a rate of 0.3 in/min. The load and deflection data were recorded and the EI calculated. The results are set forth below in Table 2, below.

TABLE 2
                        Tested EI (Billion
Construction            lb*in*in/ft width)
Present Invention       5.35
(using channels made from 12 gauge steel)
Solid wood Lumber Joist 4.60
LVL Joists              5.50

As can be seen in Table 2, the floor structures made according to the present invention had comparable stiffness as prior art floor systems made of LVL joists. And further, floor structures made according to the present invention actually had higher stiffness than a floor system section of solid wood lumber I-Joists.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims

1. Floor structure comprising:

a. an upper surface arranged in parallel to a lower surface; and

b. one or more channels disposed vertically between the upper and lower surfaces and longitudinally extending along the upper and lower surfaces, each of the one or more channels having a top and a bottom.

2. The floor structure according to claim 1, wherein the one or more channels are composed of metal.

3. The floor structure according to claim 2, wherein the metal is selected from the group comprising aluminum and steel.

4. The floor structure according to claim 1, wherein at least one of the one or more channels are of a U cross section.

5. The floor structure according to claim 1, wherein the upper surface and lower surface each comprise a plurality of wood composite panels.

6. The floor structure according to claim 1, further comprising an adhesive applied between the top of the one or more channels and the upper surface and the bottom of the one or more channels and the lower surface.

7. The floor structure according to claim 6, wherein the adhesive is selected from the group comprising: epoxies, phenolics, resorcinols, acrylics, urethanes, phenolic-resorcinol-formaldehyde resins, and methane diisocyanates.

8. The floor structure according to claim 1, wherein the plurality of wood composite panels are oriented strand board.

9. The floor structure according to claim 1, further comprising a blocking member, the blocking member disposed vertically between the upper surface and the lower surface and permanently affixed thereto, wherein the blocking member is selected from the group comprising, lumber, I-joists, or wood composite material.

10. The floor structure according to claim 1, further comprising interlocking cams.