US3534750A

US3534750A - Stressed building structures

Info

Publication number: US3534750A
Application number: US789438A
Authority: US
Inventors: Arpad Kolozsvary
Original assignee: American Velcro Inc
Current assignee: American Velcro Inc
Priority date: 1968-01-10
Filing date: 1969-01-07
Publication date: 1970-10-20
Anticipated expiration: 1987-10-20
Also published as: GB1257733A; DE1900657A1; FR2000129A1; BE726762A; DE1966234A1

Description

United States Patent [72] Inventor Arpad Kolozsvary Mountain Lakes, New Jersey 211 App]. No. 789,438 [22] Filed Jan. 7, 1969 Continuation-impart of application Ser. No. 715,454, Jan. 10, 1968, now abandoned. [45] Patented Oct. 20, 1970 [73] Assignee American Velcro Incorporated This application Jan. 7, 1969, Ser. No. 789,438

[54] STRESSED BUILDING STRUCTURES 23 Claims, 30 Drawing Figs.

[52] US. Cl 135/1 [51 Int. Cl E04b 01/342 [50] Field ofSearch 135/1, 3. 3(E). 4. 5. 7. 7. l 52/63. 80

[56] References Cited UNITED STATES PATENTS 2,167,219 7/1939 Sankey 135/1 2,961,802 11/1960 Mongan et al. 135/1X 2,963,031 12/1960 Carroll 135/7.1X 3,146,784 9/1964 Silver 135/1 3,215,153 11/1965 Huddle... 135/1X 3,255,467 6/1966 Kowalski 135/5X 3,273,574 9/1966 Huddle 135/1X 3,388,711 6/1968 Huddle 135/1 Primary Examiner-Peter M, Caun Att0rneyPennie, Edmonds, Morton, Taylor and Adams Patented Oct. 20, 1970 Sheet l of '7 R m m m Arpcld Kolozsvory ATTORNEYS Patented Oct. 20, 1970 Sheet 62 I 52 73 INVENTOR.

Arpcld Kolozsvury 39 ATTORNEYS Patented Oct. 20,, 1970 Sheet v INVENTOR. 2 I Arpad Kolozsvory 44M, W, MW

ATTORNEYS Patented Oct. 20, 1970 Sheet 1 of? VINVENTOR. By Arpod Kolozsvury w ma ATTORNEYS Patented Oct. 20, 1970 Sheet 5 of 7 INVENTOR. Arpod Kolozsvory ATTORNEYS Patented Oct. 20, 1970 Sheet 6 of? INVENTOR Arpod Kolozsvor y BY wfia ATTORNEYS Patented Oct. 20, 1970 3,534,750

Sheet Z of '7 INVENTOR Arpud Kolozsvury BY ATTORNEYS STRESSED BUILDTNG STRUCTURES BACKGROUND OF THE INVENTION This application is a Continuation-in-Part of mypreviously 'filed application Ser. No. 7l5,454, tiled Jan. 10, 1968 now abandoned.

1. Field of the invention The field of the invention relates to tension-stressed membrane shells having a fabric-covered skeleton frame, adapted for quick erection, disassembly and portability.

2. Prior Art in order to satisfy the need for portability, simplicity, economy and versatility in use, building structures in recent years have been constructed of a skeleton framework covered by a fabric wherein the overall structure assumes the configuration of a hyperbolic paraboloid, more popularly termed a saddle surface. in order to form the saddle surface above described, the essential framework of the structure generally consists of a pair of inclined parabolic arches pivotally connected to a supporting member and maintained in a noncoplanar position relative to one another. A fabric which is stretched over this framework will necessarily take on the shape of a saddle surface. Such a surface has opposite curvatures in opposite directions which work against each other thereby making the surface inherently stable. Furthermore, a saddle surface is a minimum surface in that its mean curvature is zero and therefore it cannot change its shape without stretching or destruction. Utilizing a pretensioned saddle roof surface in a building structure substantially eliminates aerodynamic flutter, a severe and often desctructive effect of wind on tents, suspended roofs, and other similar light structures.

These frame and fabric shelters have many obvious distinctions and advantages over other conventional structures of a more permanent and rigid nature, including ease and speed of assembly, erection and modification, and ease and convenience in being transported in view of their light weight and collapsibility. The aerodynamic shape of the structure reduces deleterious effects of wind and, in addition, the semirigidity or resiliency of such a structural system enables it to absorb uneven impact wind loads without producing the high stresses that would occur in a rigid structure.

One of the disadvantages which have characterized such structures in the past has been associated with the fact that the supporting member connected between the parabolic arch members has been usually rather limited in size. This feature results in a structure whose inner area is only partially usable since the head room adjacent to such supporting members is extremely low and therefore in most cases only the central portion of the enclosure is usable. Furthermore, the limited height of the supporing members permits entry to the structure only through the end portions located beneath the apices of the inclined parabolic arches. Still further, since many of the structures provide a wall fabric which is suspended from the parabolic arches to form side walls of the structure, the only way heretofore of forming an entrance into said structure while at the same time retaining portability has been by providing the side wall fabric with a slit to form a flapped entrance into the structure when not in use. Such a slit is usually sealed by means of a conventional zipper or button-type fastening means. This type of entrance is not only cumbersome and time consuming to use, but also provides only limited access to the structures.

Another disadvantage of these structures is brought about by the fact that oftentimes bulky and difficult to handle in a disassembled condition. in this connection, the various elements of the structure are often required to be packaged into separate crates or boxes before they can be moved to another location as conditions may require, thus limiting the actual mobility such structures are alleged to possess.

Still another drawback of such structures has been associated with the fact that the weakest link is generally centered at the junction between the fabric material and the structural elements of the framework to which it must be secured. The fabrics which are used in these structures generally possess great internal strength and to maintain the integrity of the structure the connection of roof fabric to supporting structure must possess the same strength. in particu lar, since the roof fabric of these structures supplies the entire tensile force necessary to support the arches in an inclined position, it will be recognized that any rupture of the connection therebetween will cause the entire structure to collapse.

in view of the above discussion, it is a primary object of the present invention to provide a building structure which is capable of taking advantage of the unique structural stability of a tensioned saddle surface structure, while at the same time overcoming the disadvantages which characterize similar structures of the prior art, all of which will become abundantly clear by reference to the following portion of the specification.

SUMMARY OF THE lNVENTlON in accordance with the teachings of the present invention, there is provided a selfsupporting building structure, the exterior surface of which comprises, in part, a prestressed roof fabric which imparts to the overall structure the configuration of a hyperbolic paraboloid, more commonly referred to as a saddle surface. The roof fabric is stretched tightly over a supporting framework whose unique configuration is responsible for the utility of the building structure of the invention. The supporting framework consists generally of a pair of spacedapart channel-shaped supporting members on which are supported in pivotal arrangement, a pair of inclined principal arch members. The principal arch members are connected to vertical support members by means of a pivotal assembly and, together with the upper part of the supports, form a closed loop. Each pivotal assembly is so constructed as to permit each principal arch to move pivotally in the vertical direction and, if a three hinge arch assembly is used, it will also permit of the horizontal displacement of the arch bases.

Tension in the saddle shaped roof fabric is maintained by a series of tensioning cables extending between the principal arch members and the supporting members, each tcnsioning cable being equipped with a turn buckle for adjustably urging the principal arches away from each other to create the proper tension in the roof fabric.

The support members include a door thereby providing the primary entrance opening into the structure, said opening being particularly suited for personnel passage to and from the closure. When in disassembled condition, the support memhere, by reason of their particular shape, further serve, in combination, as a crate into which the components of the structure can be packaged and transported from place to place in accordance with the requirements of a particular application.

The framework further includes a pair of secondary arch members which are connected pivotally to the bottom portion of the support members to form a second closed loop defining the lower terminal edges of the structure. These secondary arch members, while not needed for structural stability, are characterized by a unique construction which provides added versatility to the entire structure. Specifically, each secondary arch is adapted to pivot about parallel axes each of which is contained within the planes defined by the secondary arch. Thus, the secondary arches may be selectively raised and lowered about these axes to provide two rather large entrance openings into the enclosure.

The exterior surface of the structure is further defined by two second fabrics, which are suspended at opposite sides between the peripheral edges of the principal and secondary arch members to form side walls of the enclosure. Both fabrics are removably joined to their respective arch members by a pile-type hook and loop fastening means to provide a strong and durable connection which is characterized by a uniform distribution of stress over the entire surface of the junction. The joining means are further constructed to facilitate rapid and efficient disassembly of the structure.

In the architectural structure comtemplated by this invention, the fabric covering becomes a principal structural element in achieving both static and dynamic stability. In view of this fact. I have discovered that the shape and angular elevation of the principal arch members are extremely critical if maximum material efficiency is to be obtained from the structural elements comprising the framework of the structure. It will be realized that this condition can only be achieved by insuring that the principal arch members are subjected primarily to compression, or compression and tension if trussed, which in turn is dependent upon effective elimination of bending moments therein. For this purpose, the principal arch members are inclined with respect to the horizontal so that the resultant forces of all vertical loads as transmitted by the roof fabric lie substantially in the respective planes of the two arches. Furthermore, to approach the optimum momentless condition of said parabolic arches, when subjected to uniform snow load, the parabolic curvature of said arches is so designed as to follow the shape of the moment diagram caused by such loadmg.

The fabric as it is stretched upon the closedloop defined by the principal arches is formed into a doubly curved shape, which in a typical case is a hyperbolic paraboloid. This is a nondevelopable shape and has the characteristic of being nondistortable unless the material comprising the shape is ruptured or destroyed. The shape, in its perfect form, which is attempted in the preferred embodiment below, comprises both a positive and a negative curvature at all points in the fabric sur face. Since the fabric is secured at all points around the loop and is tensioned thereon, these positive and negative curvatures are maintained, and at each point of the surface the sum of the different curvatures may be considered effectively zero.

The shape described above is inherently stable with respect to wind moving across its surface, in that it minimizes the possible flutter effects that generally develop with fabric covers due to air pressure variations. Any tendency of the fabric to deflect downward is restrained by the tension transverse to the longitudinal lines. The curvatures of this surface also reduce aerodynamic effects of wind, and render the structure stable with respect to gusts and turbulence that would deflect it from its prestretched shape.

In the interests of strength, a supplementary tension cable may be fastened to the hem of the roof fabric and drawn tight to peripherally cap the roof fabric over the principle arch members thereby further increasing the structural stability of the structure under various loading conditions discussed earlier. Furthermore, the roof fabric may be reinforced with supplemental steel cables aligned in the direction of one or both major axes of the loop or, if desired, a safety cable may be extended between cross bars connected transversely to the principal arches to prevent collapse of same should the roof fabric be destroyed. Finally, the principal arches may be trussed.

When the arches are biased to diverge by the adjustable tension cables, this structure becomes securely maintained without any guy wires or other connection to the ground. The only necessary anchoring is from the support members to the ground at or near their base parts. Since external tensioning means are not required to maintain the shape and rigidity of this construction in this fully assembled condition the structure is suitable for air transport with the mere addition of a removably secured truss to maintain the support members in spaced relationship. Also with such a truss the structure could be maintained on water by pontoon supports.

BRIEF DESCRIPTION OF THE DRAWINGS comprising only the structurally essential members of the roof;

FIG. 5 is a perspective view of the skeleton frame of the structure shown in FIG. 1;

FIG. 6 is a fragmentary perspective view of the frame showing the support members and connection of the arches there;

FIG. 7 is a perspective view similar to FIG. 6 showing the inside of the support member and its connections to each arch;

FIG. 8 is a partial perspective view of a pair of support members;

FIG. 9 is a perspective view of support members joined to form a box for enclosing the structure of FIG. 1 in its disassembled condition;

FIG. 10 is a partial plan view of an arch and a connection part;

FIG. 10A is a schematic plan of a trussed principal arch;

FIG. 11 is a partial elevation view taken along line 11-11 of FIG. 10;

FIG. 12 is an exploded perspective view of a second alternate form of assembly of support member to a principal arch linkage assembly;

FIG. 13 is a partial sectional view of a principal arch and two fabrics secured thereto;

FIG. 14 is similar to FIG. 13 with only one fabric secured to a secondary arch;

FIG. 15 is an elevation view showing the structure in a first stage of erection according to one embodiment of the invention;

FIG. 16 is similar to FIG. 15 showing a second stage of erection;

FIG. 17 is similar to FIG. 15 showing a third stage of erection;

FIG. 18 is similar to FIG. 15 showing a fourth and final stage of erection; and

' FIGS. 19-22 are end views respectively of FIGS. 15l8.

FIG. 23 is an elevation view showing the structure of erection procedure B in a first stage of erection;

FIG. 24 is similar to FIG. 23 showing a second stage of erection;

FIG. 25 is similar to FIG. 23 showing a third stage of erection;

FIG. 26 is similar to FIG. 23 showing a fourth stage of erection;

FIG. 27 is a fragmentary view of FIG. 26 showing a suggested means for performing the step of erection shown in FIG. 26;

FIG. 28 is similar to FIG. 25 showing the fifth and final stage of erection;

FIG. 29 is a perspective view of an alternative embodiment of the structure of this invention.

DETAILED DESCRIPTION OF THE DRAWINGS As shown in FIG. 1, the building structure of this invention indicated generally at 30, assumes the configuration of a saddle surface and is defined generally by support members 33, principal arches indicated by dotted lines, secondary arch members also indicated by dotted lines, and side wall and

roof fabrics

32 and 31 respectively. The support members 33 define a substantially channel-shaped member which also includes an entrance passageway and a door 49.

The basic framework for the structure is shown most clearly in FIG. 4 and 5 and, as shown therein, comprises a pair of space apart support members 33 and a pair of principal arch members 40 connected to each other by a pivotal linkage assembly which, in turn, is carried by the upper portion of the support members, said arches defining between them a closed loop 41. Each principal arch member includes a closed end portion 42, spaced apart legs 43 extending from and forming a continuation of the end portions, and terminal portions 44. Each principal arch has a substantially parabolic shape and lies in a plane which is inclined upward with respect to a horizontal plane. A safety cable 46 may be secured between the end portions of the arches for maintaining the inclined positions of each prior to attachment of the fabric. After attachment, the safety cable may be slackened and retained in that condition as a safety feature to prevent the roof arches from collapsing in the event the roof fabric is torn open.

As shown in FIG. 5, the utility of the building structure of this invention may be further enhanced by the inclusion therein of cross bars 47 which extend transversely of the principal arch members and are connected at their terminal ends to the legs of each principal arch member approximately half way between the end portion and the apex. An auxiliary supporting cable 46 extends longitudinally between the cross bars and can be utilized, for example, as a support to enable the suspension of heavy concentrated loads within the enclosure.

The cross bars serve as the primary means for stiffening and strengthening the principal arch primarily to resist the effects of wind load. In this connection, the principal arch members may be still further strengthened by forming them of trussed sections 40 which is shown in FIG. A.

Referring to FIG. 8, the supporting members 33 are basically rigid components, each comprising a horizontal base member 20, a vertical member 70 connected to the base member, and triangular side walls 51 connected perpendicularly to both the vertical member 70 and the base member 20. These members may be constructed of aluminum, wood, steel or any other suitable material having the necessary strength characteristics. The upright member 70 includes a door 49 for ingress and egress to the tent-like structure and the triangular side plates 51 of the support members 33 provide lateral stability to the entire structure thus permitting it to withstand large forces to which it may be subjected by snowfall or high velocity winds, or both.

Mounted on each side of the support members 33 near the base member is a hook 62 shown in FIG. 6. Each principal arch leg 43 is connected to the base member by a tension cable 63. The tension cable includes at the lower end a turnbuckle 64 which is connected to the hook 62 for permitting length and tension adjustment of the cable. The upper end of the tension cable is releasable secured to the principal arch leg 43 at joint 65. It should be noted that for particularly large structures where mobility in assembled condition is not a primary concern, the tension cables may be secured directly to the ground or foundation, instead of to the supporting member. for increased uplift resistance.

Mounted near the bottom of each side of each support member 33 is a horizontal axis hinge 52 for pivotally joining the secondary arch member 45 to the supporting members, said secondary arch members in combination with the supporting members forming a second closed loop 4!. The lower secondary arches are not essential for structural stability but are intended, in part, as an anchorage to which the lower extremities of the wall fabrics 32 can be secured. Each secondary arch member, in addition, serves as a gate for effecting a full-width opening into the structure which, depending on the overall size of the structure, may be suitable for vehicular entry and exit to and from the structure. For this purpose, each secondary arch includes an arcuate section 72 the terminal ends of which are connected pivotally to leg members 73. The leg members are, in turn, pivotally connected to the supporting members 33 by hinge 52 in the manner described above. Lifting of the arcuate section 72 to an inclined position as shown in FIG. 2 can be accomplished, for instance, by pulling cable 35 attached to said arcuate section about pulley 36 which may be attached to the principal arch member 40 as shown in FIG. 5 thereby causing the arcuate section 72 to pivot about points 38. For particularly large structures, the lifting of arcuate section 72 can be facilitated by using two or more cables at spaced apart locations. Alternatively, if conditions so require, the entrance opening can be fashioned by lifting the entire secondary arch member 45 to the position shown on FIG. 3. For this purpose, the cables can be merely attached to the leg members 73 of the secondary arch members and lifted in the same manner as described above thereby pivoting the entire secondary arcli about pivot points 39. It will be recognized that the entrance opening formed in this manner provides considerably more headroom which may be advantageous when a particularly large object must be moved into the enclosure.

As will be seen later, two methods of erection are shown which differ because of corresponding changes to the attaclrment of the linkage assembly 50 to the support members 33. In their alternate forms these methods will be referred to as erection methods alternates A and B.

In alternate A form of construction (FIGS. 7, 10, II) the top of each support member above the door 49 is adapted to carry the linkage assembly 50 which connects together the leg portions of the principal arches into a closed loop. The linkage assembly 50 comprises a connector bar 54 having spaced apart collar members 56 which are rigidly connected to the bar 54. As shown in FIG. ll, each collar member 55 further comprises a cylindrical sleeve 55A which is welded to a bifurcated member 55B. which, in turn, is provided with opposed holes 55C for receiving a bolt. The collar members as shown most clearly in FIG. 7 are constructured so that the bifurcated member 558 straddles the top portion of each support and is secured thereto by bolts extending through aligned holes 57A in the support member. In alternate B form of construction shown in FIG. I2 the linkage assembly 50' has rigidly attached at each end thereof an angle 55'. The angle 55' is adapted to fit snugly against the rear and side of support member 33 and will be bolted to the top of said member 33 after elevation of the roof arches as will be explained.

Each linkage assembly 50 and 50' further includes a vertical hinge 59 or in case ofa three hinged principal arch (FIG. 10) a horizontal hinge 60 as well, together with swivel joint mechanism, indicated generally at 58, which extends outward from each end of the connector bar 54 for pivotally connecting the end portion of one leg of a principal arch thereto. As shown in FIGS. 10 and 11, each swiveljoint mechanism is constructed so as to permit the principal arch 40 to move in a substantially horizontal plane about pivot pin 60 and in a substantially vertical plane about pivot pin 59. In case ofa three hinge principal arch. an additional horizontal hinge connection 61 is provided at the close end of each principal arch to provide additional flexibility as conditions may demand. It will be recognized that the combination of

horizontal hinges

60 and 61 permit lateral contraction or divergence of the principal arch legs without attendant strain thereto. Vertical hinge 59 permits vertical rotation of the principal arches for assembly purposes and for proper tensioning of the roof fabric.

An important feature of this invention resides in the particular means for fastening the roof fabric and side wall fabric to the principal arches 40 and the secondary arches 45. The upper portion of the side wall fabric and the outer periphery of the roof fabric are secured around the full perimeter of the loop 4t defined by the principal arches 40. Attachment of these fabrics is normally achieved in a variety of ways, usually by the use of adhesive or mechanical means; however. it is a principal object of this invention that the structure be suitable for simple and rapid assembly and disassembly without the need for special tools. equipment. or scaffolding. For this purpose, a separable hook and loop fastening means has been found to be particularly satisfactory and as such constitutes an important feature of this invention.

Referring now to FIGS. 13 and 14, it will be seen that the fastening means contemplated by this invention comprises a first strip 83 of flexible material having a pile-like surface consisting of a multiplicity of tiny resilient upstanding loops. The strip 83 is attached to the entire outer periphery of each principle arch 40. A second strip 84 of flexible material having a pile-like surface consisting of a multiplicity of tiny resilient hooks adapted to interengage the loops of pile strip 83 is attached to the upper edge of the inner side of the wall fabric 32.

It will be understood that when two strips of this type are placed into face to face contact, their respective loops and hooks interengage one within the other thereby securing said strips into locking engagement. Separation of the two strips requires a force of considerable magnitude within attempting to effect the separation of the large number of hooks and loops at once, but separation may be quite readily effected by progressively peeling the strips apart. The use of this type of fastener permits the fabric to be easily and quickly secured to and removed from the arches, and to be so used through many cycles and under many conditions without substantial weakening. A fastener of this type is commercially identified by the trademark VELCRO and is made by the Velcro Corporation having an office at 681 Fifth Avenue, New York, New York.

In addition, this type of fastener has a very useful capacity in establishing a strong junction between the fabric and the arches which is characterized by virtually a total absence of gaps between points of connection. A fastener of this type will insure that stress loads to which the fabric is subjected will be uniformly distributed thus preventing the development of stress concentrations at any particular point, as would occur with a less than uniform junction. In all other types of connectors, two items must be brought to precise mating at point connections. This is not true of the fastener described above and therefore relatively loose tolerances and greater speed of erection are permitted with the Velcro connector.

The roof fabric 31 is attached in overlapping arrangement with the wall fabric 32 to the principal arch member 40 in the same manner as described above. Thus, a pile strip 83A having the same structure as pile strip 83 is secured to the upper edge on the outer side of the wall fabric 32 and pressed into mating contact with pile strip 84A which has the same structure as pile strip 84, the pile strip 84A being securely attached to the peripheral edge of the roof fabric 31.

As shown in FIG. 14, the lower edge of wall fabric 32 is attached to the periphery of the secondary arch by wrapping it around and under secondary arch 45 and joining it thereto by means of pile strips 83 and 84 which are attached to the contacting surfaces and pressed into mating engagement in exactly the same manner as described above.

Depending on the size of the structure, the subject matter of this invention also contemplates as shown in FIG. 13, in addition to the hook and loop fastening means described above, a

"continuous peripheral tensioning cable 74 inserted into the hem of the roof fabric 31 to relieve part of the stress imparted to the junction shown at FIG. 13. In some instances it may be advantageous to secure the roof and wall fabrics to each other thereby providing a single continuous cover for the entire structure, in which case the

strips

83 and 84 may be arranged accordingly.

As seen in FIG. 4, straps 80 are stitched to the roof fabric 31 in the form of a V" 80'. The straps are adjustably fastened by suitable fastening means to the upright side walls 51 in order to pretension the center section of roof fabric 31 in the transversal direction.

Furthermore, identical hook and loop fastening means are also provided for securing the side wall fabric 32 to the support members 33. In this connection, a pile strip 83 is disposed along the vertical edge of the support member 33 and a hook strip 84 is attached to the wall fabric 32 adjacent thereto. The connection is effected in the same manner as indicated above.

It is a further important object of this invention that all the principal structural elements being easily separable and packaged in such a manner as to be easily transportable from place to place. With this purpose in mind, the principal and secondary arches may be formed of numerous segments such as shown at 37 of FIG. which can be connected together by rigid releaseable joints therebetween. For instance, tapered telescoping-type joints, connector sleeves and bolted or pin joints, have been found to be particularly well-suited for accomplishing this purpose. Various types of hinged connections are also suitable, such as for instance, universal joints, which in the case of those included in the secondary arches, may be locked to become rigid by the insertion of suitable locking pins.

To further enhance the mobility of the disassembled structure, the support members 33 are capable of performing a particularly unique function in that the entire assembly may be dismantled and packaged in a container 66 formed by a simple reversal and fastening togetfiof the support members 33 as shown in FIG. 9. Thus, the entire structure is selfcontained and requires no additional parts either in form of tools or crating members. This feature is particularly important in applications which require a high degree of versatility and portability.

Referring now to FIG. 29. wherein an alternative embodiment of the invention is depicted. it will be seen that the side wall fabric is provided with a series of spaced apart openings window covers may be installed with a minimum expenditure of time and effort by pressing the strips 83' and 84' into mating engagement to effect the desired connection, all of which has been heretofore described in connection with effecting attachment of the wall and roof fabrics to the various components of the framework of the structure. The alternative embodiment depicted in FIG. 29 also contemplates providing the support member 33 with translucent reinforced plastic panels 82 located over the entrance doors 49. This feature is particularly useful in allowing light to penetrate the enclosure.

With reference to FIG. 10A an embodiment of the invention has been schematically illustrated wherein the principal arches 40' are trussed for greater rigidity and strength. In case of a three hinged trussed arch cross-bar 47 is pivotally connecting at the midpoint or apex of each arch.

To facilitate and expedite their erection, and to eliminate the need for shoring, scaffolding or other special erection tools, the structures of this invention can be assembled entirely on the ground and then raised into their final lifted position. The two alternate erection methods differ in the manner of raising the structure after it has been assembled on the ground and in the structure for attaching the principal arches to the connector bar 54 and support members 33.

The first erection procedure (A) as shown in FIGS. l5-22, employs the structure of FIGS. 6, 7, l0 and 11. With this method the support members 33 remain in their generally horizontal initial position, as shown in FIGS. 15 and 19 until the assembly of principal arches and fabric covers has been completed on the ground, at which time the entire structure is raised by tilting up the support members into their final upright positions. The support members are tilted up either both at the same time, as shown in FIGS. 17 and 21, or one after the other. During the raising procedure collar member 55 rotates around connector bar 54 as the support member 33 is tilted into its final upright position.

The structure employed in the second erection procedure (B) as shown in FIGS. 23-28 is to be from that of the first alternate (A) in the disposition of its linkage member 50' only, shown in FIG. 12. To afford greater wind stability during erection, procedure 5 begins with placing the two support members 33 in their final, upright positions and by securely anchoring them by suitable means to the ground or to the foundation. As seen in FIGS. 26 and 27, lifting cables 76 are attached to the linkage assemblies 50' in the manner indicated in FIGS. 26 and 27 and the roof is lifted to a position on top of the support members 33 by means of a suitable winch and pulley assembly and secured thereby by bolts.

Assembly of principal arches and fabric covers is done on the ground with both erection methods. First the principal arches are assembled between support members 33 immediately below their final elevated position, then a cable 46 is connected between the apices 42 and the arches, which necessarily pivots one arch into an inclined position relative to the other. Next the side wall fabric 32 is secured along its periphery to one of the arches and then the roof fabric 31 is peripherally secured to the outside surface of the fabric 32. The next step is shown in FIG. 16 whereby the arch member 40A which is shown in the elevated position in FIG. 15 is pulled downward by the operator 70 thereby causing arch member 408 to rise (shown in FIG. 16) because the two arches are still connected by cable 46. The second side wall fabric is then secured to this second arch while it is in the lower position near the ground, and the roof fabric Bil is then drawn down to the closed end of arch 40A and secured around the entire periphery of the principal arch. FlG. 26 shows the completed assembly on the ground prior to its being raised.

When the structure is in its final erected state its stability is obtained by tightening the four tension cables as which also induce the desired degree of tension in the roof fabric. As the final step of erection the secondary arch members 45 are assembled on the ground and the bottom peripheries of the side wall fabrics 32 are secured thereto in the manner shown in FlG. 14.

The above description of the present invention has been made with reference to the preferred embodiment; however, it is to be understood that various changes may be made thereto without departing from the scope of the invention as set forth in the following claims.

lclaim:

l. A selfsupported building structure comprising:

a. a first and second spaced apart support member each having a substantially channel-shaped configuration;

b. a pair of principal arch members arranged in noncoplanar relationship to each other;

e. means for movably connecting together said principal arch members into a first closed loop, said loop defining the upper terminal edges of said structure, said connecting means being supported by and attached to the uppermost portion of said support members;

. a first and second secondary arch members pivotally connected to the support members so as to form a second closed loop spaced vertically apart from the first closed loop and defining the lower terminal edges of said structure;

a first fabric suspended in tension from substantially the entire perimeter of said first loop to form the roof of said structure, the longitudinal component of said tension being sufficient to retain the principal arch members in substantially noncoplanar relationship to each other; and means for maintaining a controlled tension along the longitudinal axis of said first fabric so that the roof line defined thereby becomes a saddle surface of substantially hyperbolic paraboloid configuration.

2. The building structure according to claim l. further including a second fabric extending between the first loop and second loop to form side walls of said structure.

3. The building structure according to claim 2 wherein said support members locate the first loop positioned thereon at a level substantially elevated above the base portion of said supporting members.

4. The building structure according to claim 3 wherein at least one supporting member includes an entrance opening therein.

5. The building structure according to claim t further including means for removably joining the contacting surfaces of said fabrics to said principal and secondary arch members and to said supporting members to form an enclosed structure, said means effecting an uninterrupted connection between said contacting portions which is characterized by a uniform distribution of the stress resulting from said tension over the entire surface of the junction formed thereby.

6. The building structure according to claim wherein said joining means comprises a first strip of material defining a female member having a multiplicity of thin resilient loops projecting outward from the surface thereof, and a second strip of material defining a male member having a multiplicity of thin resilient hooks projecting outward from the surface thereof, the'hooks of the male member being adapted to interengage the loops of the female members upon being pressed into contact therewith, said male and female members being interchangeably secured to the contacting surfaces of said first and second fabrics and to the contacting surfaces of said principal arch members and the fabric in contact therewith.

'7. The building structure of claim 4 wherein each principal arch pivots about three vertical axes. thereby rendering said. principal arch member relatively insensitive to lateral movement of said support means.

The building structure according to claim 7 wherein each principal arch member includes means permitting movement about a vertical axis located at the closed end portion near the apex of the arcuate section of said arch member.

9. The selfsupporting building structure according to claim 4 wherein means are provided to pivot said principal arch members about a horizontal axis, said maintaining means comprises at least one substantially inextensible first tension cable secured at one end to one principal arch member and connected at the other end to one of the supporting members, and at least one substantially inextensiblc second tension cable secured at one end to the other principal arch member and connected at the other end to one of the supporting menbers, said tensioning cables biasing the principal arch members to diverge thereby maintaining tension in the roof cover along said longitudinal axis.

ill. The building structure according to claim 4 wherein said principal arch members are trussed.

l'rli. A building structure according to claim 4 wherein at least one secondary arch member includes an arcuate section and two leg members pivotally connected to the terminal ends of the arcuate section whereby said arcuate section is permitted to be raised into an inclined position to provide an auxiliary opening into said structure.

22. The building structure according to claim 4 further including a cross bar connected transversely to each principal arch member, said cross bar serving to strengthen said principal arches.

lift. The building structure according to claim 12 further including a supporting cable attached longitudinally between said cross bars, said cable serving to prevent the collapse of said principal arch members in the event said first fabric becomes torn or destroyed.

lid. The building structure according to claim 4 further including at least one opening projecting through said second fabric at a point intermediate said first and second loops, said opening defining windows for said structure.

id. The building structure according to claim id further including a window cover covering said opening and means for removably joining said cover along the outer edges thereof to that portion of said second fabric which defines the boundary of said opening.

116. The building structure according to claim 15 wherein said joining means comprises a first strip of material defining a female member having a multiplicity of thin resilient loops projecting outward from the surface thereof and a second strip of material defining a male member having a multiplicity of thin resilient hooks projecting outward from the surface thereof, the hooks of the male member being adapted to interengage the loops of the female members upon being pressed into contact therewith, said male and female members being interchangeably secured to the contacting surfaces of said window pane and said second fabric.

ill. The building structure according to claim to wherein said window pane is made of a transparent plastic material.

llbl. The building structure according to claim 4 further including a reinforced translucent panel positioned above said entrance opening for admitting external light into said structure.

lif The building structure according to claim lift wherein said translucent panel is made of plastic.

lift. The building structure according to claim 4 wherein said support members define in combination a packing crate into which the entire structure may be placed when disassembled.

' 12 said principal arch members near ground level for securing said fabric to said first loop.

23. The building structure according to claim 22 wherein the principal arches when lowered are maintained in said coplanar relationship and are pivotable to place one arch at a time near the ground for securing said fabric thereto.