US2929473A

US2929473A - Structural framework

Info

Publication number: US2929473A
Application number: US561729A
Authority: US
Inventors: Jeffrey B Lindsay
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-01-27
Filing date: 1956-01-27
Publication date: 1960-03-22
Anticipated expiration: 1977-03-22

Description

March 22, 1960 J. B. LINDSAY 2,929,473

I STRUCTURAL FRAMEWORK Fil ed Jan. 27, 1956 5 Sheets-Sheet 1 FIG.

uvwzzvrm JEFFREY a. LINDSA r M M4M A TTORNEYS March 22, 1960 J. B. LINDSAY 2,929,473

STRUCTURAL FRAMEWORK Filed Jan. 27, 1956 s Sheets-Sheet 2 INVENTOR. JEFFREY B. LINDSAY l'il g aep VMJWJ A TTORNEVS March 22, 1960 J. B. LINDSAY STRUCTURAL FRAMEWORK 5 Sheets-Sheet 3 Filed Jan. 27, 1956 IN V EN TOR. JEFFREY B. L INDSAV M Ms M ATTORNEYS Mar

h

22, 19 J. B. LINDSAY 2,929,473

STRUCTURAL FRAMEWORK Filed Jan. 27, 1956 FIG. (9.

5 Sheets-Sheet 4 FIG. /0.

INVENTOR. JEFFREY B. LINDSAY BY A TTORNEYS March 22, 1960 J. B. LINDSAY STRUCTURAL FRAMEWORK 5 Sheets-Sheet 5 Filed Jan. 27, 1956 M m m w. TW 35 M M M m IV A Y B QGPi STRUtZTURAL FRAMEWORK Jeffrey 3. Lindsay, Los Angeles, Calif.

Application January 27, 1956, Serial No. 561,729 1 claim. or. 189-34) The invention relates to structural frameworks and their enclosure.

The need for structural frameworks is fundamental to the entire construction industry. The design of buildings, bridges, fuselages, and chassis of all sorts as Well as specialty structures such as individual architectural forms, bulk storage containers, radar reflectors, etc., is dependent on and to a large extent limited by framing or forming techniques. I have developed a structural element which permits greater design freedom than heretofore possible with conventional methods. The structural element herein described is applicable to frarneworks in general. It is a unique and highly efficient framing facility which is inherently strong, light, simple to produce, ship and assemble. It can be employed equally well to achieve frameworks of any overall shape or form.

The building element of my invention comprises an axle and a peripheral rim, and means interconnecting the opposite extremities of the axle and the rim.

A framework built in accordance with the invention comprises a plurality of structural elements which are interconnected in the structure so that adjacent elements have common rim sections.

The exterior appearance of the structural framework in accordance with the invention is that of a gridwork of substantially regular polygons. A plurality of compression members define a polygonal peripheral n'm around an axle. Tension members connect the axle to the peripheral rim. The framework whether plane, curved, faceted, etc., is preferably a series of contiguous, substantially regular polygons composing a grid whose successive compression member components do not lie in a continuous straight line in any section of the grid. The lack of such straight line patterns precludes inherent fold or failure lines in the structure.

Preferably the framework comprises short lengths of compression members approximately the length of the edges of the polygons of the grid. A connector orients these compression members at all juncture points of the grid.

As mentioned above, the invention is equally applicable to frameworks of plane configuration or to frameworks of simple and compound curvature configuration such as cylinders, cones, domes, parabolic or hyperbolic surfaces,v

. ZtiZfAi? Patentedfviar. 22, 196% structure was 70' in diameter and 32' high and supported the skinning material plus 30 pounds per square feet live load over the entire area of 5400 square feet.

The theoretical factors contributing to the inherent structural efliciency of the invention are: complete separation of tension and compression functions in components; a system for establishing sectional depth in the frame; a system for establishing the over-all tension throughout the framework; a non-redundant repetitive element; three compression members per joint in the preferred configuration (which is the simplest pattern of the least number of members that will define a continuous surface); a contiguous arrangement of elements in a configuration which rapidly deploys stresses and interlocks the sectional depths of the individual elements, inducing over-all sectional depth throughout the framework.

The benefits of the structural strength that the invention imparts apply equally to all structures built in accordance with the invention.

Selection of an appropriate grid for any particular structural framework is arbitrary. For example, a contiguous hexagon pattern or an octagon-square pattern could be employed. Both are preferred configurations as there are three members per joint in each case; however, any pattern of any polygons is permissible.

The grid pattern is best determined by using a scale model representing the desired form. A grid pattern of contiguous polygons is drawn on the surface of the model. Preferably the polygons are substantially regular so that the number of different lengths of component members necessary for any given structure is held to a minimum.

Simple or compound curvatures may be subdivided in accordance with known mathematical systems into smaller areas compatible with the structural concept of the invention. On the Orderly Subdivision of Spheres by Duncan R. Stuart appearing in the student publication of the School of Design, North Carolina State College, volume 5, No. 1, exemplifies one guide to the subdivision of spherical surfaces. The subdivision of all forms and surfaces usually requires that the regularity of polygons forming the grid of the structure be modified to achieve the approximation of the desired form. Use of publications similar to the one above, and experience in the field of art of the invention allow the number of lengths of component members of different polygons to be held to a minimum in order to facilitate production and assembly problems. The approximation of any form can also be achieved by constructing the required framework in a series of facets each comprising a number of coplanar structural elements.

Preferably the polygons of the elements are defined by a straight compression members. The compression members are held to the connectors of the structural element by the compressive force imposed on them by the tension members extending between the angles of the compression rim and the centrally located axle of the element.

In effect, the axles are suspended within the confines of the peripheral rim formed by the compression members. The suspended axle gives sectional depth to the element and when these elements are suitably integrated so that the compression member grid follows a zig zag line, then sectional depth is induced in the entire framework.

be attached either within the structural framework or applied externally to the framework, as specifically required.

The structures generally employ high performance materials. The inherent structural efiiciency of the invention permits such economy of these materials that strong, light-Weight frames are easily achieved. For instance, a dome shaped framework built in accordance with the invention and made of aluminum alloy tubes and cast aluminum connectors or joints, and held together with stainless steel tension straps, weighted 1200 pounds. The

Should it be required to amplify this framework sectional I depth, auxiliary structural members or straps may be included to join the ends of the axles on one or both sides of the framework. 7 Length of the compression members and the distance between fastening holes in the tension straps are pref cisely calculated from the orderly subdivision of'the required framework configuration into an appropriate stru'c: tural grid. Y Tension throughout the framework can be slightly varied byinserting shims at suitable points. Such a process-will distort the framework as specially required or vary the resiliency of the framework.

Extreme changes in direction in part of the configuration-of -a desired structure may require individual ole-- mentssto'be, cranked so that the peripheral-rimof the element is non-planar. configuration, or the subdivision of the configuratiompermits use of an element comprising an axle and a periph eral rim lying substantially in a plane passing through the mid-point of the axle and substantially normal to the axle. In either situation tension members interconnect the axle and the rim.

However, in most structures the Further advantages and features of the invention will be apparent from the following detailed description and drawings in" which:

Fig. 1-is an elevational. view of the preferred struc-- Fig. 4 is a sectional elevation taken along line 44 of Fig. 3;

Fig. 5 is a fragmentary sectional elevation of the joint between the tension members and an axle and taken along line 55 of Fig. 2;

Figs; 6' and 7 are fragmentary schematic representations of planar configurations in accordance with the invention;

Fig. Sis a fragmentary plan view of a structure having an inner skin, and an outer covering partly'in place;

Fig.9 is a fragmentary sectional elevation taken along 7 line 9-9 of Fig. 8; and

Fig ll) is a fragmentary sectional view taken along line ill-10 of'Fig. 8.

Referring now to Figs. 1 and 2, a structural element 10 is'illustrated ashaving a plurality ofcompression.

members 11 forming a hexagonal polygon about an axle 12. The compression members bear on a spherical zone connector .or joint 13 at each angle of the hexagon. Compression members 11A also extendfrom the joints so thatthree compression members bear on each joint.

Tension straps 15 extend from. one. end of the axlexto each'joint and then back to the other end of the axle. Each angle formed by the junction of two compression members is substantially bisected by a tension strap. The whole structural element appears to be an hexagonal wheel, having spokes running from its axle to each spherical joint.

The axle 12 is approximately the same vlengthas each ofj'the compression members. The. proportions of the element thus achieved lessens the number of lengths necessary for each element, since the axle is substantially identical to the compression members. Lengthening or shortening of the axle of the element reduces or increases the cross-element tension and increases, or reduces, the section depth of the element and hence of the. framework.

A plurality of auxiliary structural strapslfi extend from each end of axle 12 to the like ends of adjacent axles.

4 in Fig. 4 the extent of the spherical joint is greater on one side of the major diameter of the sphere than it is on the other. This provides for complete seating of the compression members when they angle from the major diameter plane of the joint to provide curvature in the general configuration of the grid.

A concave wall 20 closes and reinforces one face of the spherical zone joint. This wall has three circular holes 21 near its outer edge and a fourth hole 22 at its center. The three holes provide for joint drainage and the center fourth hole provides convenient attachment points throughout the entire framework. The other face of the joint has a large opening-23. This opening gives access to three

carriage bolts

24, 25,26 that extend outwardly through radial

rectangular holes

27, 28, 29 respectively, in the spherical zone joint. Two of the holes are elongated rectangles to compensate for the changing angles of the tension members caused by dimensional variations in the polygons of required grids. The other hole is square to initially orient the joint. Generally, the bolt passing through the square hole is inserted and attached first. The bolts are spaced approximately 120 apart, approximately mid-way between the compression membersbearing on the joints.- Each of the bolts support a bushing 39. The bushing has a recessed face 31 which gives the bushing a -U-shaped cross section. Bolt 24 passes through a hole 32 in the bushing (see Fig. 3).

The squared portions 33 of the carriage bolts match the

rectangular holes

27, 28, 29 in the spherical joint so that each'bushing may be pulled towards the joint by turning a nut 34 on the end of a'bolt without the bolt turning -in' the joint: The

shoulders

35, 36 defining the re ce'ssed face 31 in the bushing are shaped at their surface adjacent-to the spherical joints to match the outerspherical curvature of the joint. Therefore, when the bushing is cinched against the surface of the joint, the shoulders .of ,the bushing are seated along their entire length'a'gainst'the joint. k

The recessed face 31 of the bushing provides a smooth curved surface around which each tension strap can pass and comfortably change direction. Each tension strap has a hole. 40 located at the approximate mid-point of the length of the strap and a hole 42 (Pig. 5) near each (not shown) of contiguous structural elements. The.

structural straps amplify the section depth of any frameworkicomprising the elements and are particularly desirable' in substantially planar structures.

Referring now to Figs. 3 and'4, eachend of reach com pgcssion member has a cap 17 pressed onto the compres-- sionmember. The cap has a concave outer surface 13.

with a drawn rim 19 which encircles the ,end of the. com-.

of curvature is substantially the same as thatgof the;

concavity of thecompression member caps- As viewed of its ends. through the central-hole of the respective strap which is seated on the recessed face of the bushing and out through the hole in the bushing. Nut 34 on the bolt completes this assembly. i

As illustrated in Fig. 5, at each end of an axle, ma-

chine bolt 43 passes through the end holes of the tension straps 15. A'nut 44 secures the straps against the bolt head and the threaded end of the bolt then centers and pins the assembled straps to the cap end of the axle.

Fig. 5 illustrates one axle With tension straps attached in a fashion typical for all axle ends of all framework elements'. For handling purposes, the strap group can be unpinned from the axles and concentrically folded fiat together.

Referring again to Fig.3, tension strap 15A is shown, seated against the recessed face of the bushing. Straps 15B and 15C in thefigure are also seated against the recessed face of their respective bushings and the bushings are cinched against the sphericalv joint. Nut 34 must be turned further on the threaded .portionof carriage bolt, to draw the bushing up to the spherical zone joint.

Fig. 3 also illustrates the preferred configuration of the:

inventionfor typicaljointing throughout the entire frame-. work. The. tension straps, are attached by means, of carriage bolts which automatically slide into a radial position inthe rectangular holes of thejoints. The spherical zone face of the jointand' the concave end-compressionmembersactlike a ball and socket joint. Automatic angling of .the. compression members is induced, by the v forceot-thetensionstraps.. As there. ar only three com: pressiommernbers per jointin the preferred system-and.

Each carriage bolt passes through the joint, 7

as their attendant straps approximately bisect the'three angles between the compression members, length tolerances are completely resolved through structural nonredundancy in the tension induced rotation of the spherical zone joint. All component dimensions are precisely predetermined from the overall configuration of the required framework grid and fabricated accurately, thus avoiding any such adjustment during assembly. All members are numbered and color-coded to facilitate assembly according to the framework design.

In Fig. 4 the illustrated compression member deviates approximately 4 from the plane axis of the joint. This and much larger degrees of deviation can be made through connector modification such as increasing the spherical surface of the joint so as not to impair the seating of the compression members. It is conceivable that should the form of the required framework include a severe bend as when an element is cranked due to the configuration, it would be necessary to use such modified joints in order to provide continuity in the over-all structural pattern. In such cases the plane of the structural polygon elements would be noticeably cranked and the axle accordingly canted so that it would remain normal to the tangent of the bend of the framework.

Further modification of the spherical zone joint is desirable in certain instances. The Wall of the joint may be slotted from the edge of the drainage holes to the radial rectangular holes to permit insertion of the carriage bolts into the rectangular holes after the tension strap, bushing, bolt and nut have been assembled. The shape of the drainage holes can be changed to permit passage of the carriage bolt head through concave wall 20 at the same time that the shank of the bolt is trav- 1elrsing along the modifying slot to enter the rectangular ole.

With reference to Fig. 2, it is apparent that the inward force applied to each of the joints by the tension straps towards the central axle exerts a compression force on the compression members. Therefore, any force tending to unseat the concave end compression member from hearing on the convex joint is opposed by the strength of the tension straps.

The balance of force Within a structural element is such that the increasing of tension in any one strap results in the increasing of tension in all the straps of the element. Therefore, the last strap whose bushing is tightened determines the force in all tension straps and hence in the compresison members. This characteristic proves that the element is non-redundant and that there is a total economy of structural components which results in a high efficiency framework.

It is theoretically propititious to design the tension straps so that the sum total of their tensile strength projected to the plane of the compression members, is exactly equal to the sum total of the strength of compression members defining the surface of the frameworkand that the individual axles be designed to provide sufiicient over-all section depth to the framework and to resist the compressive load induced in the axle by the full tension load of the straps. For example, in the aforementioned structural framework 70' in diameter and 32' high which employs the preferred structural configuration, the tension straps are full hard stainless steel & x /2"; the compression members and axles are approximately 3' long tubes of 1 /2" OD x .049"'Wall 6061T6 aluminum alloy tubing; bolts are of standard 4" diameter steel.

Fig. 6 illustrates a fragment of a planar structure constructed in accordance with the invention. The structure comprises a plurality of axles 51, each surrounded by a peripheral rim formed of six compression members 52. Tension members 54 extend between the joints 53 and the axles, suspending the axles symmetrically within the confines of a hexagonal polygon like hexagon 55 formed by the compression members.

Hexagons

56, 57, 58 adjoin d hexagon 55 and each has in common one compression member with hexagon 55. Likewise, hexagon 56 has a compression member in common with hexagon 57 and

hexagons

57, 58 also share a common compression member.

Each of the hexagons of the structure of Fig. 6 is a structural element similar to the structural element of Figs. l5 inclusive. Together the hexagons form a grid in which there are only three compression members bearing on each joint. In a planar structure the polygons of the grid (hexagons in the illustrated embodiment) may be regular. The compression members will all be of identical length and the axle may be substantially identical to the compression members. Therefore, a planar hexagon grid structure could require compression members and axles of only one length and tension straps of only one length.

Fig. 7 illustrates another preferred frame work grid configuration of the invention in which the polygons are octagons and squares. An octagonal structure element 61 has a peripheral rim made up of eightcompression members 63. Adjacent to the octagonal structural element 61 are four

octagonal elements

64, 65, 66, 67. Only part of element 67 is shown. Four

square elements

68, 69, 70, 71 are adjacent to octagonal element 61. Octagonal element 61 has one compression member in common with each of the polygonal elements 64-7 1 inclusive. Structural elements, both square and octagonal have axles, tension straps and compression tubes arranged in a similar fashion to the element of the structure of Fig. 6. Inasmuch as the configuration is planar, all of the tension members are of equal lengths in the elements that are similar and all the compression members are of equal length.

Both frameworks in Figs. 6 and 7 may be provided with auxiliary structural straps similar to auxiliary straps '16 of Fig. l.

Figs. 8 through 10 illustrate fragmentarily a structure provided with skins to enclose the volume defined by the structure. The skins may be of different types depending upon the use of "the structure and the nature of protection that the skins are to provide. In the illustrated embodiment a structure 75 (shown fragmentarily), comprisedof a plurality of structural elements such as element 76 (Fig. 8) is provided with an inner skin 77. The skin may be a woven fabric or a woven fabric coated with plastic for waterproofing or may be a plastic film material. Depending upon the nature of the skin material, a protective cover to shield the skin and enclosure from damage by sunlight and radiation and the impact of airborn missiles, radio active particles or vandalism, etc. may or may not be desirable. Figures 8 through 10 illustrate a structure having a light -weight plastic skin protected by an outer covering. The

inner skin is suspended from the framework of the structure by means of eye bolts such as the eye bolts 79 shown in Fig.9. These eye bolts have a shank 80 that projects'through the tension straps and into the axle of the structural element of the structure. The eye bolts replace the machine bolts 43 illustrated in Fig. 5. Loop 81 of each eye bolt has a flexible chain 82 fastened to it so that an end of the chain depends below the axle. The lower end of the chain passes through skin 77 and through a hole in a circular support plate 83 placed against the underside of the skin. A pin 84 is passed through the lower link of the chain to hold the support plate on the chain. In like manner, a multiplicity of points on the skin are suspended from the inner ends of the axles by means of the chains and eye bolts. The hole in the skin through which each chain passes may be waterproofed by means of suitable resilient sealing compounds packed around the juncture of the chain and the skin.

As may be seen in Fig. 9, the skin tends to depend between support chains in a catenary curve. It may be necessary to vent the skin at the support plates to allow The escape of, water vapor.

sidepressure duringhurricane windsjto prevent blowout.;of the structure. The same protectivemethod. is advantageous to neutralize variation between outside and inside "pressures of structures duringbombblasts.

The. outer covermentioned with respectto :Figs.v 8 1 through 10 is preferably composed of 1 a plurality of triangular aluminum panels 85. Each panel covers .a:

space defined by a pair oftension straps and one of the rim segments or compression members defining the polygonallstructural-elements ,of the framework. For

ins tance,,,in Fig.8 a panel SSAsubstantially covers .the space between the outer portions of tension straps 87 and 88 extending from axle 89 to the spherical joints Fig, 9).

Each of the outer covering panels is similar with the remaining panels, so a descriptionof one will sufiice.

for all. As viewed in the plan-viewof Fig. 8, four of the six spaces. defined by thetension straps and compressionmembers of structural element 76 are covered.

by panels. Fragments of the panels covering. adjacent structural elements are also visible in this view. Onesuchpanel 85B is adjacent panel 85A, of structural element 76. Thebasesof each of these panels arebentupwardly see Fig. 9) to butt against the compressionmember 92andare further bent inthe direction of the panel'apex to form a lip 93. The lips on adjacent panels project oppositely. A-cover strip 94 having opposed inwardly opening grooves ,yokes the --lips of the adjacent panels tosecure the .basesof-the triangular panels againstthe compressionmember.

An edge 95 of each panel is bent downwardly and inwardly to form a first groove havinga depth equal to half the 'widthof a tensionstrap. Opposite edge96 of each panel is bent upwardly and inwardly to :form a second groove of similar depth.

.Each panel is applied by sliding'the panel base first along the tension straps toward the compression memher or outer rim of the structural element until the grooves of the panel edges engage the tension straps.

At this point the bent portion of. the base of the panel should be in contact with the compression member.-

Each tension strap supports an edge, of two adjacent As illustrated in enlarged-detail in Fig, 10, the 1 pan ls edge 95 of panel 85A is bent downwardly and inwardly around tension strap 87 while the adjacent edge'of panel 7 85 is bent upwardly and inwardly with respect to that panelaboutthe tensionstrap, Thus, each .panel overlaps its adjacent panel-by the-width of the tension strap. The bases of the panels of adjacent structural elements 7.

are secured by means of coverstrip94.

The apexesof the triangles. are truncatedso that an opening is leftabout each-axle to permit installation of 1 the interior waterproof-skin after the outer covering is' in place. It maybe advisable to place acap over this opening to insure complete protectionof' theskin;

Vents may be specifically designed to,.-equalize high relative inside pressure with cut 90, 91 at the ends ofcompres sion member 92 (see' A structurein accordance ,with the invention supports The inner skinmay be multiple for waterproofing, insulation, vapor either. or both inner and outer skins.

barriers or acoustical purposes. Use of specific outer coverings or skins will vary with the use of the structure. 'The exterior cover described in conjunction with Fig. 8 functions to protect or armour the inner skin and its ,panelspmay be colored by anodizing or enameling and assembled so that the outer surface of the structure is distinctively patterned. The principles of skin and cover support are applicable to many types of structure covers.

The merit of the invention is that it makes possible structural frameworks which are comprised of nonredundant structural elements composed of very few types of components, each made of commercially availrality of straight compression members having concave ends, -spherical connectors linking the compression memhers-to form a unitary grid of hexagonal polygons defined by the compression members, each polygon having a'compression member in common with each adjacent polygon and each axle being disposed symmetrically within the confines of a polygon, and tension members linking the spherical connectors of each polygon to its respective axle so that the compression members defining the polygon form a peripheral rim lying substantially in a plane passing through the mid-point of the respective axle and substantially normal to the axle.

References Cited in the file of this patent UNITED STATES PATENTS 288,319 Edsall Nov. 13, 1883 1,428,484. Lankheet Sept. 5, 1922 1,463,888 Hall Aug. 7, 1923 2,682,235 Fuller June 29, 1954 FOREIGN PATENTS 82,423 Austria. Jan. 25, 1921 436,567 Italy June 10, 1948 7 OTHER REFERENCES Architectural Forum, August 1951, pp. 144-151.