Domed membrane structure and method of erecting it
BACKGROND OF INVENTION 
     This is a &#34;Continuation-in-Part&#34; of my application Ser. No. 576,101, now known as U.S. Pat. No. 4,036,244, entitled, &#34;Vertical Arch Shelter&#34;, filed June 12, 1975, which is a Continuation-in-Part of my application Ser. No. 399,333, filed May 8, 1973, now abandoned, which was a Continuation-in-Part of the parent application Ser. No. 93293 filed Nov. 27, 1970, now abandoned. 
    
    
     This invention was conceived while working with arch supported membrane shelters having both inclined and/or vertical arches as described in the above applications and such patents of mine as U.S. Pat. Nos. 3,215,153, 3,338,711, 3,802,450, 3,909,993, 3,958,588, 3,961,638, 3,990,194 and others, all of which have arch supported membranes in double curvature to enable the membranes to carry heavy external loads which decreasing membrane vibration and, at the same time, increasing the shelter stability by opposing arch deflection. 
     While the structures described and illustrated herein have inherent features of my other patents listed here, new shapes, new combinations of components along with new methods of assembly and erection are included in this application that are not apparent in the prior patents. 
     SUMMARY OF INVENTION 
     The principal object of this invention is to provide a domed membrane structure that uses lightweight arches and/or semi-arches, that are stabilized by tensioning the membrane in a double curvature configuration thus enabling the structure to carry heavy imposed loads of wind, snow, or ice. 
     Another object of the invention is to provide a much more economical domed structure by the use of strong membranes that are fabricated to curve sufficiently inward, between curved arches or curved bights of semi-arches, to enable the membrane to &#34;capture&#34; the arch or a section thereof, thus opposing arch deflection and restraining arch movement within the elastic limits of the tensile strength of the membrane. 
     Another object of this invention is to provide a domed membrane structure in which membrane vibration is greatly decreased or eliminated by a tensioned configuration of the membrane. 
     Another object of this invention is to provide a domed membrane shelter that has a frame consisting of semi-arches that are &#34;bowed&#34; to the shape desired during erection from straight members to facilitate shipment and handling prior to erection. 
     Still another object of this invention is to provide easy and simple methods of erection for pre-curved semi-arch members. 
     Another object of this invention is to provide an erection procedure whereby straight members are &#34;bowed&#34; and securely retained in this configuration after the membrane is tensioned between the &#34;bowed&#34; semi-arches. 
     Still another object of this invention is to provide a method of tensioning the membrane between the arches by separation of the arches. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective of a typical arch supported domed structure or shelter. 
     FIG. 2 is the plan view of FIG. 1. 
     FIG. 3 is a side elevation of FIG. 1. 
     FIG. 4 is a cross-section through the semi-arches and the membrane at about midpoint, taken at line 4--4 of FIG. 1. 
     FIG. 5 is another cross-section through the semi-arches and membrane near the base, taken at line 5--5 of FIG. 1. 
     FIG. 5a is a cross-section as in FIG. 5 with the addition of illustrating a membrane &#34;pocket&#34; attachment to a semi-arch. 
     FIG. 6 is an illustration of an attachment of semi-arches at the apex. 
     FIG. 7 is a cross-section of FIG. 6, at line 7--7. 
     FIG. 8 illustrates attachment of tubular preformed semi-arches at the apex. 
     FIG. 9 is a cross-section of illustration FIG. 8, taken at lines 9--9. 
     FIG. 10 illustrates a sleeve to interconnect two segments of a semi-arch. 
     FIG. 11 illustrates an interconnection of rod type segments of a semi-arch. 
     FIG. 12 illustrates an adjustable connection of a semi-arch to a base. 
     FIG. 13 illustrates a connection of a semi-arch to a base or to the ground. 
     FIG. 13a is a side view of FIG. 13. 
     FIG. 14 illustrates connections of pre-formed semi-arches spaced radially at the apex. 
     FIG. 15 illustrates how the semi-arches in FIG. 14 fold into a parallel relationship for erection. 
     FIG. 16 illustrates a plate connection of arches or semi-arches at the apex. 
     FIG. 17 illustrates the lifting of a multiplicity of semi-arches attached to the apex with the membrane on top of the semi-arches. 
     FIG. 18 illustrates &#34;bowing&#34; of the semi-arches during erection. 
     FIG. 19 illustrates anti-sway tension members installed between semi-arches. 
     FIG. 20 is a cross-section of a tension ring and membrane attachment. 
     FIG. 21 illustrates a ventilation device in apex of structure. 
     FIG. 22 is a cross-section illustrating one of many methods by which the membrane can be attached to the semi-arches. 
     FIG. 23 is a cross-sectional view of another membrane attachment means to the semi-arches. 
     FIG. 24 schematically illustrates attachment of semi-arches to an apex assembly of an oval shape. 
     FIG. 25 schematically illustrates the arch attachment configuration of semi-arches and arches to elongated apex assembly plates. 
     FIG. 26 schematically illustrates how arch separation can tension a domed membrane. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIG. 1 the assembled structure is shown with semi-arches 1 attached indirectly to each other by means of a circular ring 2 at the apex of the structure. These semi-arches can be regarded as radial supports for the membrane cover 3 which can be attached to the sides or underside of the supports 1 or the membranes 3 can cover the supports 1 like a cap. Various closable or open penetrations can be made in the membrane cover for egress such as illustrated by various tension rings such as shown as 4 or 5. The supports 1 can be arcs or a combination of arcs to form the semi-arches or they may have a combination of straight and arc sections. 
     FIG. 2 illustrates the radial configuration of the supports 1 from the apex ring 2 that support the membrane 3. The membrane can have a slight inward curvature at the base as shown by 6 to better carry wind loads near the base or snow drifts around the structure. If such loads near the base are negligible, the membrane can be made without the inward curvature 6 to provide more useable space near the base. Also shown in FIG. 2 is a tension ring 7 that prevents the supports from spreading outward. This may be necessary where the semi-arch ends cannot be securely fastened to a concrete slab, firm ground or another dependable sub-base. 
     FIG. 3 is a side elevation of FIG. 2 which shows the membrane attached directly to the base 8 by use of a member attached to the base or by indirectly by such means as the tension ring member 7 which opposes spreading of the supports 1. The membrane 3 can also be attached to the base by tension rings 9 embodied in the membrane 3 that can be used to urge the membrane downward thus tensioning the membrane vertically and transversely as it is pulled down over the curved supports. Larger openings can be made in the membrane and still keep it tensioned by the use of larger tension rings 10 to provide openings for entrances, exits, or other openings. 
     FIG. 4 illustrates, in cross-section, the inward curvature of the membrane between supports that enables the membrane to carry heavy external loads of wind, snow or ice and also gives the membrane double curvature between curved sections of the semi-arches. This inward curvature also enables the membrane to &#34;capture&#34; the semi-arches sufficiently to oppose deflection of the semi-arches produced by external loads. 
     Strong membranes with 10 to 30 times the tensile strength of cotton canvas used in old circus tents, are available today that are woven of fibres such as glass, synthetic organic materials -- even inorganic polymers are under development -- can be regarded and should be recognized as dependable and safe structural components, at least comparable to the fabric membranes that hold our automobile tires together. When such fabric membranes are used with these structures, they can add to the structural integrity of the structure as a whole, rather than just to support line roof loads such as snow, ice or wind, between the semi-arches. When such strong membranes are given deep inward curvature between curved semi-arches they can &#34;capture&#34; the semi-arch, or at least the curved bight section of the semi-arch, and by its tensile strength oppose deflection or permit limited deflection within the elastic limits of the membrane. The tensioned membrane can control arch flexing depending, of course, on several factors such as the weave of fabric membranes, the angle or steepness of the inward curvature as it sweeps inward away from the arch and, among other factors, the tensile strength of the membrane. With the right choice of such factors, the stability of the semi-arches can be greatly improved and where conditions permit more flexibility of the semi-arches (to flex like aircraft wings under stress) the strength of the semi-arch can be greatly reduced making it possible to reduce the size, weight and cost of the semi-arches as well as related costs of handling, transportation and erection of the structure. The stability inherent with the deep inward membrane curvature design is somewhat comparable with the spokes of a wheel capturing the wheel rim, except that the hub of the wheel would be wider -- depending on the membrane sweep angle inward, from the arch, and the depth of the inward curvature. 
     Even a shallow inward curvature between corresponding bights of adjacent semi-arches will make the membrane shorter in length midway between the arches, from the apex to the base, than its length where it is operatively attached to the semi-arches. As the depth of the inward curvature is increased, the difference in length increases and the effectiveness of the membrane to control arch flexing also increases. The membrane can be fabricated with pockets 11 to partially or intermittently enclose the semi-arches to exactly locate the semi-arches or the membranes can be given sufficient inward curvature to position the arches when the membrane is pulled down over them. In some instances, it may be desirable to employ openable pockets that can be closed by lacing, zippers 11a, or other means. 
     FIG. 5 illustrates in cross-section, the membrane contour between the arches near the base with very little inward curvature. Reduced inward curvature can also be used near the apex or along the semi-arches when structures are designed for very low external loads or the span between corresponding arch segments is sufficiently short to prevent overloading of the membrane under design loads. 
     FIG. 5a illustrates in cross-section, the membrane near the base as described under FIG. 5 above but with the added &#34;pocket&#34; 11, means to attach the membrane to the semi-arches 1 which can be openable by a means 11a such as lacing, zipper, etc. 
     FIG. 6 illustrates the use of plates 12 between which semi-arches 1 can be champed by tightening bolts 13. 
     FIG. 7 is a cross-section of the clamping plates showing the semi-arches 1 and clamping bolts 13. 
     FIG. 8 illustrates a channel ring 14a used at the apex to indirectly attach the semi-arches 1 to each other in a manner that permits them to pivot around the bolt 15a and be locked together by the bolt 15b. The locking member 14b can be a flat bar to lock two semi-arches together or be a circular plate(s) to lock all semi-arches together rigidly. Pivoting action of the semi-arches is shown in FIG. 9 and FIGS. 14 &amp; 15. These semi-arches can be pre-curved before assembly to the channel ring. A sufficient number of semi-arches can be attached to the channel ring in a prone position on the base because of the pivoting action to erect most of the frame. 
     In FIG. 10 a method of assembling semi-arch segments is illustrated. Here a hollow semi-arch can be assembled by using internal sleeves 16 to form a slip joint. The membrane 3 will keep the segments from separating. 
     FIG. 11 illustrates an external sleeve joint 17 between two rod or tube segments 1. 
     FIG. 12 illustrates how the end of the semi-arches can be attached to a substantial base 18 by such means as an anchor bolt 19 to a radial support or semi-arch foot 20 which is secured to an adjustable means by which the length of the semi-arch can be made by clamping, or other means, to the semi-arch 1. The device illustrated is a split tube 21 with clamping bolts 22. Such an arrangement is usually desirable when the base is not level or to compensate for discrepancies in fabrication of the membrane and/or the semi-arches. 
     FIG. 13 illustrates a method to indirectly attach the base ends of the semi-arches 1 to the ground by the use of stakes 23 and a means 24 which can be clamped to the semi-arches. FIG. 13 also illustrates the circumferential tension member 7 nested against the means 24 to oppose the outward movement of the semi-arch 1 when the semi-arches are &#34;bowed&#34; from straight segments and/or when an axial load is imposed on the structure. 
     FIG. 13a in cross-section is a side view of FIG. 13 which illustrates one method of anchoring the arch to the base. 
     FIG. 14 illustrates the radial position of pivotal semi-arches around the channel apex ring 14. 
     FIG. 15 illustrates how the pivoted semi-arches can be placed in parallel position on the base for lifting to a vertical position to then pivot to the radial position as illustrated in FIG. 14 to form an erected frame. 
     FIG. 16 illustrates the use of one or more flat plates 25 instead of a circular ring 14 at the apex as a means to indirectly attach the semi-arches to each other. In either case, the semi-arches can be rigidly attached to the plate 25 or to the ring 14 to reduce parts and expense when erection procedure does not require pivotal arches. This is particularly desirable in the erection of small structures, where semi-arches are attached individually to an apex ring, plate or other attachment means as the frame is assembled. 
     FIG. 17 illustrates the lifting of a frame consisting of straight semi-arch members 1 attached to an apex interconnecting ring, plate or other means. These straight sections droop downward toward the base from the apex. The membrane may be placed on the frame near the apex before the frame is lifted. 
     In FIG. 18 the drooping semi-arch members are pulled inwardly by means of a tension member and a device 27 such as a cable jack. When all of the semi-arches are curved downward and/or inward sufficiently, the semi-arch ends are secured to the base or prevented from moving outward by the circumferential tension member 7. The membrane is then pulled down to tension it over the semi-arches and fixed directly or indirectly to the base by tension rings or otherwise. Variations of procedures to tension or attach the tensioned membrane include &#34;over-bowing&#34; the semi-arches, pulling the membrane downward, fixing it there, then &#34;un-bowing&#34; the semi-arches to help tension the membrane. 
     FIG. 19 illustrates a method of installing tension members 28 between semi-arches or between semi-arches and the base 28a to oppose swaying of the structure under high winds with flexing semi-arches. Trans-structure tension members 28b between lower ends of opposite semi-arches may also be desirable. 
     FIG. 20 is a cross-section to illustrate a tension ring 29 embodied in the membrane 3 between the semi-arches in an arc shaped pocket 9, FIG. 3. The membrane may extend below the tension ring 29 by attaching another section 30 to the membrane 3, or just extending the membrane 3. The lower section 30 can be secured to the tension member 7 by a fastener such as VELCRO so that 30 becomes detachable and can be rolled up to provide an opening under the tension ring 29. Usually the detachable section 30 is secured to the membrane along a straight line as shown by 31, FIG. 3. Zipper, VELCRO or other fastening means can be used to close openings around the sides of 30 or at the base. 
     FIG. 21 illustrates how a ventilating device can be incorporated in the apex ring assembly. This can be manually operated as shown or motor-driven with a remote or automatic control. 
     FIGS. 22 &amp; 23 show other methods of attaching the membrane to the underside (FIG. 21) of the semi-arches or at the side (FIG. 22) of the semi-arches. Such attachments have been illustrated in my other patents in detail. 
     FIGS. 24 &amp; 25 illustrate schematically different shapes of the apex assembly wherein the semi-arches are rigidly fixed or otherwise attached to the apex assembly. Many variations of the shape of an interconnecting plate or ring (even square) are possible within the scope of this application. 
     FIG. 25 shows schematically a combination of semi-arches 31 and arches 32 fixed to an elongated plate assembly. The arches 32 can also be two semi-arches fixed to the plate, thus requiring only one semi-arch design. Such a combination can also be used in a circular ring assembly as schematically shown in FIG. 8 or an elongated ring assembly can be used that would be similar in shape to this FIG. 25. 
     FIG. 26 illustrates schematically how an oval type or elongated ring assembly 33 can be used to separate the center arches or semi-arches 32 to tension a membrane cover that is operatively attached to or supported by the semi-arch frame. Adjustable compression members 35 or jacks can force apart the two telescoping members 34 of the interconnecting means. The amount of movement required depends on the stretch of the membrane and the size of the structures.