Patent Application
20240360665
The invention relates generally to structural posts and more specifically to asymmetric I-posts to address energy conservation in housing.
In building construction, one often uses standard dimensional lumber such as 2″×4″ which are used to frame houses. When the lumber runs horizontally, they are referred to as joists or beams; when they are used vertically, they may be called posts or studs. In construction, a frame is made from plural vertical posts arranged at regular intervals and these are usually termed “studs.” From an engineering perspective, an important difference is that horizontal joists are loaded in bending, putting the top portion into compression and the bottom portion into tension, whereas a vertical post is subject to purely compressive loads. A common failure mode for a post is buckling, which is not relevant to horizontal joists.
I-beams are ideal structures used in horizontal joists because they optimize the material used for those compressive and tensile loads. Such I-beams are not used as vertical posts because there is no such need for optimizing the lumber into compressive and tensile portions. Therefore, posts are usually sold as solid dimensional lumber of regular dimensions, such as 2″×4″, 2″×6″, etc. Dimensions are provided herein in imperial inches, as is commonly used in the construction industry but the inventive principle also holds for metric markets.
The structure of these posts is not optimized for green-build housing. In particular, the solid cross-section of these posts creates a great thermal bridge between the inside and outside of the house. The concept of a thermal bridge is that houses lose most of the heat at those points in the construction where materials with low thermal insulation connect the inside to the outside walls. Therefore, even if insulation is used inside the wall, the studs themselves will provide the thermal bridge to transfer heat.
WO2017011121A1 describes a thermal break wood stud with rigid insulation and wall framing system. This solution requires giving an insulation break within the stud. WO2012114122A2 discloses a construction panel comprising a first frame member and a second frame member that are connected together around their perimeters by one or more connecting members. U.S. Pat. No. 4,852,322A on the other hand discloses a composite structural beam comprising two parallel wooden rails each having a groove and two rectangular pieces of wooden web slotted into the grooves of the rails. These solutions still pose the problem of increasing weight or making the final construction unwieldy for transportation.
Energy costs and building/energy codes are forcing solutions to be found. Thus, there is a need to solve the problem of energy conservation without compromising on the structural integrity of buildings.
In one aspect, the invention provides a structural post having an I-shaped cross section. The structural post comprises a major flange; a minor flange, opposite the major flange, and having a cross-sectional area less than the major flange; and a web portion connected to the major and minor flanges. The difference in the cross-sectional areas of the major flange and the minor flange results in an asymmetrical structural post.
In another aspect, the invention provides a wall frame comprising the structural post as described herein. Some of the key advantages of the structural post of the invention include: strength where it is needed; optimal use of materials for each function; thermally separation improves insulation; dimensionally stability (OSB/diagonals move less during changes in moisture content of framing); interchangeability with standard lumber; composite construction results in consistently straight studs that will not warp; and utilization of shorter and lower grade lumber compared to I-joists (as it is designed for vertical use, the loads are predominantly compression, which allows lumber that is often waste to be converted to usable structural members).
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
The definitions provided herein are to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope of the present disclosure.
As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” encompass embodiments having plural referents, unless the content clearly dictates otherwise.
Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. For example, the common 2×4 lumber refers to a nominal size of 2″ by 4″ even though such dimensions are typically now smaller than that (e.g., 1.5″×3.5″).
As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
In one aspect, the invention is a structural post that has been optimized for vertical loading with enough material to take the compressive load and structured to resist buckling.
In cross-section, each post is constructed of a major flange 12, a minor flange 14, and a web portion 16 between the flanges. These flanges 12 and 14 take the majority of the compressive load while being spaced apart to resist buckling. As the lengths of the web portion and both flanges are all the same and intended to be cut to any length for framing, it is preferably to reference width and depth dimensions of the post, as seen in cross-section or plan view, per
Web portion 16 connects the two flanges 12 and 14 with minimal area between them to reduce the thermal bridge. Therefore, the ideal web portion would have negligible area while maintaining the spaced-apart aspect of the two flanges. The web portion may be a weak structure and is not necessarily capable of being load bearing, but its purpose is to reduce thermal bridging as it is a low profile thermal break. Advantageously, it is made of oriented strand board. The web may run continuously the length of the post for improved strength. In an alternate embodiment, the web portion is a diagonal lattice board of lattice slats between the flanges. Thus one slat is in compression, and the next in tension.
The orientation of the major and minor flange can vary depending on the final use case situation.
The post is designed to be asymmetrical, with the major flange 12 being larger than the minor flange 14. It is convenient to design the post's dimensions such that it has the same dimensions as the lumber that is already commercially available. For example, a standard 2×10 post would be replaced by the structural post of this invention of the same overall dimensions (i.e. nominally called 2× 10 but actually 1.5 inches×9.5 inches), notwithstanding that the web portion has substantially less material. Thus, the structural post of the invention can be used in replacement framing, keeping the standard spacing between existing studs (for example, every 16″ or 24″) and able to support window framing. Thus preferably, the major flange has a minor dimension ranging from about 1.3 inches to about 1.7 inches, preferably about 1.5 inches.
One of the key advantages offered by the structural post of the invention includes reduced weight while still maintaining the overall dimensions of an existing standard post. This is achieved through the use of a wooden webbing section whose width may be only ⅓rd of the existing standard post. Thus the webbing thickness may be less than 0.6 inches (<1.3 cm). The reduced weight for the same dimension of the post of the invention in turn facilitates transportation, while reducing weight of the final construction.
The major flange 12 has cross-sectional area sized for off-center compressive load, which renders the structural post 10 optimized for compressive loads. The asymmetrical configuration of the structural post with a thin web 16 connecting two load bearing elements (major flange 12 and minor flange 14), such that the major axes of the two flanges are aligned and parallel with the major axis of the web portion. This configuration facilitates improved load bearing properties in vertical wall constructions, and utilizes timber more efficiently.
The Euler formula for column buckling is Pcr=π2·E·I/L2 where E is the lumber's modulus of elasticity in (force/length2), I is the moment of inertia (length4), and L is the length of the post. I is determined largely here by the flanges' orientation. The present stud is designed with flanges with major axis aligned (in cross-section) that have a lower moment of inertia in the width direction BUT once the post is installed into a housing frame and screwed to a wall sheet (e.g. drywall, OSB or plywood) the system's moment of inertia increases so great that buckling is no longer of concern.
As seen in plan view in
In other embodiments, the web portion could be attached to the major flange and the minor flange through finger joints, interlocking glues, and the like.
The present post is an asymmetrical EWP (engineered wood product) stud designed for use in light wood framed construction. The two main differentiating features from a typical 1-joist are the flange size being asymmetrical and the major axes being aligned with the web axis (in plan view).
The invention overcomes the current problem with the commercially available wooden I-joists that have been optimized for use in horizontal (floor/roof) applications but have no manufacturing support as framing for vertical (wall) use. The structural post of the present asymmetric post is particularly developed for use in structural wall construction to replace standard dimensional lumber, as well as exceeding specifications when extra thick walls are required.
The structural post of the invention is intended to be used for the construction of light wood framed buildings. The asymmetrical nature of the stud optimizes lumber usage by connecting the primary load-bearing flange to a smaller flange by means of an OSB (oriented strand board) or diagonal wood slat web.
Typical construction methods place the primary load-bearing member towards the interior of the structure; however, this isn't required. The primary/larger flange can be oriented to the interior or exterior as needed. The structural post of the invention comprising the two flanges connected by the thin web section is optimal for construction of passive house structures and other low energy structures. The lightweight and dimensionally stable AI-Stud enables site builders and prefabrication facilities to quickly and accurately frame thick walls with minimal thermal bridging.
All the components of the structural post of the invention, including the major flange, the minor flange and the web portion, may advantageously be made of wood. However, it would also be obvious to one skilled in the art that there may be insulation boards fitted to the sides over the web portions to make the overall post rectangular in shape, which may help with installation. This may be, for example, flush facing known to be useful for windows mounting, also sometimes known as side board, which is typically a wood fibre board having little strength, low density, no binders, just heated and pressed wood. The side board though, provides thermal insulation, as it has the same R-value as cellulose.
The structural post of the invention may further comprise thermal insulation in the form of fillers between the studs. An exemplary filler is cellulose, specifically those blown in fibres.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
