TRIAXIAL WEAVE FOR THE PRODUCTION OF STIFF STRUCTURAL MANIFOLDS FOR USE IN STRUCTURES AND WEAVING METHOD THEREOF
Woven structures must be made of materials that are sufficiently flexible that they can be woven together. This often results in a finished structure that is also flexible. Thus weaving has long been considered inadequate for the production of buildings and other objects requiring high levels of stiffness. The present invention relates to increasing the stiffness of triaxial-weave woven structural manifolds. The present invention provides for a new type of triaxial weave that allows for structural members of greater diameter and stiffness that are still flexible enough to accommodate the geometry of the weave. The result is structures having approximately eight times the structural stiffness of conventional triaxial-weave woven structures.
This application claims priority to the earlier filed provisional applications having Ser. Nos. 62/406,045 and 62/511,992
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTNot applicable.
MICROFICHE APPENDIXNot applicable.
FIELD OF INVENTIONThe present application claims priority to the earlier filed provisional applications having Ser. Nos. 62/406,045 and 62/511,992, and hereby incorporates the subject matter of the provisional applications in their entirety.
The present invention relates to a pattern and geometry of weaving that produces manifolds with high bending stiffness and strength. A primary application of the new type of weave is the structural framework of buildings.
BACKGROUND OF THE PRIOR ARTWoven objects are known to have high strength-to-weight ratios. This is because the structural material continues essentially unbroken throughout the woven object. Thus, the strength-to-weight ratio of the completed object approaches the strength-to-weight ratio of the material it is constructed of. Objects that are not woven generally make use of fasteners and adhesives to bind the components together into the larger objects. The fasteners and adhesives add weight to the completed object and structural material bonded together with fasteners and adhesives is generally less strong that the original structural material before it is cut.
While woven objects are known to have high strength, they are also known to have low stiffness. In order to weave materials together, the materials must be sufficiently flexible that they are able to be bent over and under each other into an interlocking woven pattern. Thus, the resulting woven manifold also has a high degree of flexibility.
While methods of weaving find difficulty in creating objects with sharp corners because of the stiffness of the material woven, objects with rounded surfaces are created with ease. Wicker furniture is a good example. In contrast, objects made with fasteners and adhesives find difficulty in creating smooth curves, but create straight-sided angular-cornered objects with ease. Consider the logistics of building a wooden staircase with screws as either a straight staircase or a spiral staircase. For these reasons, the woven building concept has a unique synergy with the geodesic domes popularized by Buckminster Fuller. Most everything that makes a Fuller dome more difficult to build with conventional techniques, becomes an asset when the structure is re-envisioned as a woven building. While Fuller domes are structurally efficient, they have been held back by the complexity of building and covering them—too many cuts, odd shapes that create material waste, too many fasteners, too many specialized fasteners and hubs. Joints and fasteners lead to snag points and expansion gaps that make covering and sealing the structure more difficult. The new woven dome takes all of the advantages of the Fuller domes and adds simple and low-cost construction and covering.
Conventional triaxial-weave woven dome buildings use a 1-1 triaxial weave. This weave is shown in
The structural material requires sufficient flexibility to be bent over, under, and around the other structural members or to be repetitively inserted through the appropriate openings in a partially completed woven manifold to create the geometry of the weave. This required flexibility degrades the overall stiffness of the entire structure. And even with extremely flexible building materials, like plastics, the largest allowable size of the structural members lead to a structure that has low strength.
Contrary to all the advantages of weaving, including the reduced amount of measuring and cutting and the reduced need for fasteners and adhesives and the resulting high strength-to-weight ratio, weaving has been found to be unsuitable for objects requiring high degrees of structural stiffness, like buildings. Thus, there is a need in the art for a new type of weaving, that is compatible with stiffer less flexible structural materials that can produce structural manifolds with large degrees of stiffness.
SUMMARY OF INVENTIONThe application will use the following definitions:
“Woven members” are the linear structural elements that comprise the woven object.
“Plainweave” is the most common type of weave in which the woven structural members pass intersecting members on alternate sides. For example, in the weaving of a building, if woven in “plainweave” the structural member will pass one intersection on the interior of the intersecting woven member and will then pass the next intersection on the exterior of the intersecting woven member. This pattern continues alternating each intersection between interior and exterior.
“Basket weave” is a synonym for “plainweave”
“Wave number” defines the number of waves in the unit length and is inversely proportional to wavelength.
“Meander” is the alternating or approximately sinusoidal path taken by a woven member which allows it to pass over and under other woven members in a defined pattern, locking the woven object together.
The present invention provides for a new type of weave, which is a triaxial 2-2 weave, that together with properly chosen woven members of an appropriate material and thickness, can produce structural manifolds of high stiffness, including double-curved manifolds that are suitable for a greater variety of applications requiring high levels of compressive force and structural stiffness such as the structural framework for a building.
The structural members of the preferred embodiment of the present invention pass alternately over two and under two other structural members. With the same weave density and structural member thickness (diameter assuming structural members with a circular cross section), the maximum curvature required of the structural members is approximately 35% of the value required in the corresponding 1-1 weave. One might initially think that the diameter of the structural members could be increased by a factor equal to the inverse of 0.35 (or approximately 2.8) before the elastic limit of the material is reached. But a greater diameter requires a meander of greater amplitude to pass over and under the larger intersecting members. The larger diameter simultaneously reduces the maximum curvature of the members. Thus, the allowed increase in diameter is not a factor of 2.8 but the square root of the same. Bending stiffness increases with the fourth power of diameter, thus bending stiffness of the building's wall is increased by a factor of 8 by replacing the 1-1 weave with a 2-2 weave and taking full advantage of the allowed increase in the diameter of the structural members.
Strength is also increased by a factor equal to the increase in cross-sectional area of the woven members or approximately 2.8. For most dome structures, stability is a more significant structural issue than strength, and thus the factor 8 increase in wall stiffness, which increases the stability of short wavelength deformations, is of high value. Stiffness in tension and compression (resistance to length change) is increased by a factor equal to the increase in cross-sectional area of the structural members and for double curved manifolds, this increases structural stiffness for long wavelength deformations.
In attempting to make a woven building using the common 1-1 “plain weave” it quickly became apparent that the required stiffness (for the overall strength of the building) and required flexibility (to allow the woven members to bend over and under each other) were mutually exclusive. Biaxial weaves exhibit bias shift and are therefore inappropriate for buildings for the lack of dimensional stability. Thus, the need in the art for a new type of weave that requires less flexibility of the woven members and is thus suitable for buildings requiring higher levels of strength and stiffness was clear.
Weaving is a method of joining flexible linear structural elements together to form a two-dimensional or three-dimensional structure. Weaving generally accomplishes the joining by frustrating the desire of the linear structural elements to remain straight by forcing them to meander over and under each other. The tendency of the structural elements to be straight creates contact forces where they intersect with other structural members. These contact forces together with friction creates some traction between the structural members. This traction accumulated over the many intersections throughout the length of the structural member substitutes for adhesives or fasteners and holds the entire structure together. The economic advantages of weaving stems from its ability to use the linear structural members in full length, without cutting, the reduced need for fasteners and adhesives, and the ability of the continuous length of structural material to transport forces great distances through the object created.
Fabrics, textiles, and all woven objects can be characterized by the number of axial directions present in the woven pattern. The vast majority of woven materials are biaxial. This means that there are fibers representing two axial directions. In conventional woven fabric, the fibers representing the two axial directions are called the “warp” and “weft” respectively. The warp is parallel to the original direction of manufacture on a loom but is otherwise equivalent to the weft. The warp and the weft are mutually perpendicular. Biaxial weaving is common for its simplicity. Two axial directions are the minimum number required to bind the woven members into a single object. Biaxial fabrics and textiles demonstrate an instability in their dimensioning diagonal to these two axial directions. These diagonal directions are often referred to as the “bias”. This dimensional instability in the bias direction can in some cases be advantageous. For in the production of clothing there is often a need for the fabric to “stretch and move” with the subject and these bias directions in the fabric can accommodate such changes in dimension. To prevent these instabilities in the fabric, a minimum of three axial directions are needed, and triaxial fabric and textiles are the simplest that meet this requirement. Buildings that shift and move are undesirable, and thus woven buildings should use a triaxial weave. There are little or no fabrics produced with triaxial weaves for the extraordinary complexity of the machine that would be required to automate their production.
The best-known method of constructing the woven building of the present invention is to weave the structural members together by hand. The building can initially be woven in a two-dimensional form, flat on the ground, and then forced into a three-dimensional shape after the topology of the weave is correct. For example, ropes and winches can be used to contract the circumference of a flattened building to bring it into a three-dimensional shape.
The woven buildings can be secured to the ground by means of attaching a fabric cover to ground anchors and tightening those attachments. This tension force in the cover squeezes the building into the ground and the resulting friction holds the building in place.
A fastener can be used to bind the intersections together more tightly to prevent the woven members from sliding against each other under structural load. Appropriate fasteners could be screws, cable ties, and rope or twine.
Woven dome buildings can be built “top down”, where the weave is started at the center of the building (usually the building's highest point) and as the weave is continued outward the roof is lifted with a crane. At some point when the downward curve of the manifold causes the woven members to be perpendicular or nearly so to the ground, they can be bent under the structure and this will often cause the structure to begin to support itself, lifting the weight off the crane. This method involves the expense of a crane. Woven dome buildings can also be built “bottom up”, by beginning the weave at the ground and continuing it upward until finally closing the weave at the center point (usually the highest point). Because the walls of the building do not obtain their stability until the dome is complete, the walls are often too weak to climb on as a substitute for scaffolding during construction. Thus scaffolding is also needed. The buildings can also be woven flat on the ground in a planar arrangement. If this “flat weave” method is chosen, several circumferential woven members around the perimeter cannot be including while still in the planar configuration due to the excessive circumference. Once the weave is complete (except for the circumferential members that cannot be added yet), the building can be erected. To erect the building, ropes are placed around the circumference of the building and winched tight until the circumference of the planar weave lifts off the ground and the whole structure becomes curved upwards at its edges. As it is desired that the edges curve downward instead of upward to lift the roof, the structure is then inverted. With the circumference ropes still in place, several ropes are tied to one edge of the structure and pulled across the structure causing the whole structure to flip over like a pancake being cooked. Now the woven manifold has its edges curved downward and the central area of the manifold is held above the ground by the edges of the manifold. The winches are further tightened to reduce the circumference and lift the roof. As the circumference approaches its planned value, the final few circumferential woven members can be woven into the pattern. Weaving the building flat is the preferred method as it avoids the expense and danger of using a crane or scaffolding. If fastener are used to further secure the intersections, the fasteners in the upper portion of the building can be placed before the winches are completely tightened so that the intersections can be easily reached from the ground without scaffolding.
The woven members can be made of any material that is sufficiently strong and flexible. Polyvinyl chloride irrigation pipe is a good choice given these requirements. The fundamental repeating unit of the weave of the present invention can be placed on the pattern of (inside the triangles of the pattern of) a geodesic dome of any class (class 1, 2, or 3) and any frequency or other patterns where the 5-edge vertexes are placed possibly in a more irregular pattern, with or without a 5-edge vertex in the center of the structure. Negative solid curvature in the manifold (or building shape) can be accommodated by 7-edge vertexes. The 5-edge vertexes are generally placed in areas of positive solid curvature.
If the woven building is spherical or ellipsoidal, it can be truncated at a level that leaves its widest point higher than its lowest point or ground level. This provides headroom to the occupants of the building when they are standing near an interior wall.
Most raw material that can be used as woven members is acquired in limited length and lengths must be joined together using a method that is suitable for that material. For polyvinyl chloride irrigation pipe, a solvent cement and telescoping ends are common and suitable. The lengths need not be joined to achieve the required length at the beginning of the process. Simplicity can be found in weaving only one piece at a time and joining them afterwards. In this way less length of material needs to be pulled through the weave and time and effort can be saved. Sometimes the material is sufficiently flexible that the pieces can be joined to extend the length before being woven and then a loop of the material can be formed to store the extra length until the head of the member can be woven along the appropriate path far enough to consume the added length.
The characteristic U-turn patterns that attach to the bounding member or door opening can be smoothly curved (as in the figures), bent in angular corners, or the members can be terminated without a curve and the dead end of the terminated member can be fasted to the bounding member or door opening. The U-turns must also be fastened to the bounding member or door opening in some way.
Some modes of structural deformation are facilitated by the woven members sliding against each other, and the traction produced by the weave may be insufficient to prevent this sliding movement. Thus for added structural stability, a fastener can be placed at each intersection. Screws, cable ties, rope, and twine are suitable fasteners.
To weave in a new length and thus extend a woven member, the end of the member is taken through the appropriate openings in the existing weave being mindful to pass appropriately over and under in the required pattern of the present invention.
Unlike conventional geodesic domes, the buildings of the present invention are particularly suitable for textile covering because of their smooth snagless surface.
Claims
1. A building material used in construction comprising a 2-2 triaxial weave.
2. The 2-2 triaxial weave of claim 1 comprised of woven members with a circular cross section.
3. The 2-2 triaxial weave of claim 1 where the intersections of the woven members are optionally secured with a fastener.
4. A three-dimensional structural members comprising a 2-2 triaxial weave.
Type: Application
Filed: Oct 10, 2017
Publication Date: Apr 11, 2019
Applicant: Linus Industries, LLC (Tallahassee, FL)
Inventor: Sean Barton (Quincy, FL)
Application Number: 15/729,658
