CA1103877A

CA1103877A - Tension structure

Info

Publication number: CA1103877A
Application number: CA321,069A
Authority: CA
Inventors: Mamoru Kawaguchi
Original assignee: Taiyo Kogyo Co Ltd
Current assignee: Taiyo Kogyo Co Ltd
Priority date: 1978-03-06
Filing date: 1979-02-07
Publication date: 1981-06-30
Also published as: GB2016070A; BR7901332A; DE2908653A1

Abstract

Abstract of the Invention:
A tension structure having a curved surface comprises a group of metal strips to form the curved surface and each of the strips is pre-stressed under tension for stabilizing the structure. The tension is produced in the strips by a group of tension members generally having a curvature opposite to that of the strips, the strips and tension members being arranged to effect tension indirectly on each other through an intermediate means such as a group of inter-mediate members disposed therebetween or air serving as the intermediate means or directly. In some instances, the ground surface regarded as having an indefinite radius is utilized as equivalent to the tension members. The erection of the structure is available by the application of tension and the conventional scaffold usually required may be omitted.

Description

TENSION STRUCTURE

The present invention is related -to a tension s-tructure and, particularly -to a tension s-truc-ture having a curved metal surface comprlsing plural me-tal s-trips each of which is pre-stressed and ac-ts as a resis-ting member of the s-tructure.

It has been practiced to employ a tension structure to cover a large space such as a gymnasium, exhibiting pavilion9 assembly hall9 plant9 cooling tower, or large roof and/or wall the examples of which are disclosed in "Tension Structures and Space Frames" by Y. Yokoo et al published in 1972 by -the ~rchitectural Institute of Japan.
In constructing such a large space s-tructure, roof or wall, it has been customary -to ins-tall panel members over a braced grid or network structure compris_ng tension members such as wire ropes9 steel frames) etc. Sometimes9 a membrane may be stre-tched over such base frames as listed above.
However9 aerial operation and/or a large scaffold have been necessary to erect such a braced grid or network structure which resulted in the drawbacks in safety and efficiency regarding the aerial operation and expensiveness regarding the necessary sca~fold. Further9 as -touched upon above9 an additional opera-tion of installing panels or stretching a membrane is required after the erection of the frame structure.
Also9 for almost the same purpose as that of the structures touched upon above~ a pneumatic membrane structure has been employed such as disclosed in "Pneumatic Structures"

: .

7~7 by Frei Otto in Vol. 1 of "Tensile Structuresi' published by IJllstein Verlag GmbHI Frankfur-t/M-Berlin. The erection of such a pneumatic struc-ture requires neither a large scaffold nor an additional operation for installing panels or the lil~e e~cep-t for supplying pneumatic pressure to keep the pressure di:ft`erence between the inside and the outside of -the s-tructure. The materials employed in -the pneumatic struc-ture are generally canvas 9 woven synthetic ~ibers or woven glass ~ibers coated with synthetic resin and they are used as membranes and such membrane is stretched to form a desired shape by applying pneumatic pressure and maintaining the in-ternal pressure above t~le a-tmospheric pressure. The woven materials referred to above are generally combustible or inflammable and -the glass :Eibers are easily fusible under high temperature. Therefore 9 the materials conven-tionally used for the pneumatic membrane structures are inferior against ~ire or flying sparks. Also~ -they de-terio-ra-te under natural conditions, such as e~posure to ultra-violet rays and, the materials made of or comprising high polymers are subject to so-called "creep"9 and so they are not suitab].e for maintaining s-table shapes and mechanical properties There~ore9 the conventional pneumatic struc~
tures have never been suitable for permanent or se~i-permanent constructions.
Accordin~ly, it has been desired to have a structure which is ~ree from the above drawbacks.

Thereore~ it is an object of this inven-tion to ~L~ x~r~7 provide a~ economical structure suitable for permanent or semi-permanent usage to completely or partially protect and/or enclose a relatively large space.
It is a further object of -this inven-tion to provide a structure which substantially does not req~lire an aerial operation and/or a large scaffold in cons-truction thereof.
It is another object oP this invention to provide such a structure as stated above wherein the outer sur~ace member is o~ metal sheet stretched easily at the time of construction of the structure without need of further opera-tion for installing panels, etc. constituting wall or roofing members.
It is s-till another objec-t of this invention to pro-vide a structure satisfying the above objects and ~eing able to be erected pneumatically.
According -to the present invention, the above obJects are satisfactorily attained.
The structure constructed according to the present invention employs a group of metal sheets or strips as exterior surface members or skins thereof which are pre-stressed in tension.
The pre-stressed strips act to serve as resisting members, in addition to their ordinary protective surface members, to maintain the rigidity and stability 0~! the structure and to withstand wind9 rain, snow or earthquake.
Tension is applied to each of the surface members or strips in a direction substantially parallel to the longitudinal directio~ of the strip, l.e. -the rolling B~7 direction of the strip. To apply tension to each of the group of metal strips9 there are generally arranged a group of tension members coupled with -the group of strips through in-termediate members disposed therebetween~ The strips9 tension members and the intermediate members are arranged to interac-t with each other to maintain -the s-tressed situa-tion of -the strips9 the tension members being also placed under tensile stress. The strips and the -tension members under the above condition are caused to form a curved outer skin surface the curva-ture of which is generally opposite to that of the group of tension members. When the term "opposite" is employed regarding -the curvature in the present specification and claims it refers to the si-tuation in which the center of curvature is oppositely located regarding the surface or skin. In some of the embodiments of the present invention9 the intermediate members may be omitted.
Further9 the intermediate members may be replaced by pneumatic means ~ air - when -the structure is designed as similar -to a pneumatic membrane structure. Also9 when the pneumatic membrane system is employed9 the tension members may be replaced with another means such as ground having an indefinite radius of curvature ln some instances.
Since the outer surface members or skins are made of metal9 they also provide durability u~der the various weather conditions.
As touched upon above9 each of the strips is plaoed substantially only under tension9 -there is substantially no necessity to join the adjacent strips with each other . .

~3~7 except ~or such case as when the strips themselves are used to seal the pne~atic pressure or there is necessity such as to prevent rain from en-tering inside~ The erection of -the struc-ture according to -the present invention is just to apply the tension -to the strips (and -the tension members) whereby tl1e manu~acturing and erection thereo~ are performed very easily and economically b~ saving materials and eliminat-ing several operations and the large sca~old hereto~ore required in the cons-truction o~ similar structures.
10The objects and advantages of the present invention ; not touched upon in the ~oregoing will be further clari~ied in connection with the detailed description o~ the preferred embodiments of the present invention which ~ollows the brie~ description of -the drawings below.

15Fig. lA is a perspective view of a preferred embodi-ment o~ the present invention 9 FigS~lB and 1~ are fractional illus-tration of portions showing an example o~ means for connecting concerned members of the embodiment shown in F`ig~ lA wherein Fig. lC is a cross section as viewed along the line IC-IC in Fig. lB9 Figs, 2A and 2B show a second embodiment of the present invention in a plan view and a side view9 respectively9 Figs. 2C9 2D and 2E illustrate partially an example o~ practical connections applicable to the structure shown in Figs. 2A and 2B wherein Fig. 2C is a cross section taken along the line IIC-IIC in Fig. 2A and Figs. 2D and 2E are cross sections viewed along the lines IID-IID and IIE-IIE

in Fig~ 2C, respectively9 Figs. 3A and 3B show a third embodimen-t having a curved surface of a saddle shape in a plan view and a side view, respectively 9 Figs. 3C and 3D indicate partially a connection of a strip to a frame as an example for use in the third embodi-men-t wherein Fig. 3C is a cross section taken along the line IIIC-IIIC in Fig. 3A3 Fig. 3D is a view taken along the line IIID-IIID in Fig. 3C9 Fig. 4 is a side view of a four-th embodiment of the presen-t invention which is a tower shape9 Figso 5A and 5B show a fifth embodiment of the present invention in a plan view and a side view9 respectively, u-tilizing pneumatic pressure for tensioning strips9 F`ig. 6 is a side view of a sixth embodiment of the present inven-tion applying negative pressure (i.e. lower than atmospheric pressure) to the closed space9 Fig~ 7A is a plan view of a seventh embodiment of the present invention similar to the fifth embodiment but having a rectangular plan9 Fig~ 7B is a plan view of modification to the seventh embodiment shown in Fig. 7A9 Figs. 8A and 8B show an eighth embodiment of the present invention having a spherical surface in a plan view and a side view9 respectively9 Fig. 8C is a fractional perspective view showing a mechanical means for connecting adjacent strips in the eighth embodiment 9 ~ 3~'7~

Figs 8D and 8E show a plan view and a side view of modification to the eigh-th embodiment shown in Figs. 8A and 8Bo9 and Figs. 8~` and 8G show a plan view and a side view, respectively, of fur-ther modification to the eighth embodi-men-t shown in Figs. 8A and 8B.

Referring to Fig. lA, there i5 illustrated one of the preferred embodiments of the present invention in which the structure constructed is utilized as a roof 10 having a generally rec-tangular configuration. The top surface thereof consis-ts of a group o~ sheet metal strips 11 arranged parallel to each other~ The s-trips 11 are9 for example, of steel, stainless steel or aluminum alloy sheet having a desired thickness.
A group of -tension members9 in this case wires 129 having curvature opposi-te to the strips 11 is arranged under the strips 11 and plural intermedia-te members 13 are disposed be-tween the two groups (11 and 12)o The opposite ends of strips 11 are secured to rigid boundary members 149 respecti~ely. Rlso9 the opposite ends of tension wires 12 are secured to plural posts 15 as shown Under such con-struction explained above 9 if tension is applied to either the strips 11 or wires 12 or the both, the strips 11 and wires 12 are caused to have mutual effect on each other through the intermediate members 13 and are pre-stressed to the ex-tent that the whole s-tructure becomes stable and main-tains its shape so as to withstand wind pressure or load 7~

imposed by snow or earth~uake. The tension may be applied to the structure of the roof 10 9 for example 9 by stretchin~
ropes 16 between the members 14 and the ground~ Or7 strips 11 and tensioll members may be securecl to -the members 14 and 15~ respective:Ly~ through appropriate fittings such as turnbllckles whereby -tension is applied by adjusting such ~ittings. In the illustrated embodiment9 wires 13 are employed as tension members 9 however9 it is available to select one from several materials such as wire ropei iron or steel rod9 e-tc. Also9 -the wide selection of materials ~or the intermediate members is available including metals and non-me-tallic materials. Employment of tubes may be helpful to reduce the weight of the structure.
As illus-trated, the length of each o:E the intermediate members is adjusted so as to keep the proper con~igura-tion of the strips 11 and tension members 12 under tension.
The strips 11 may overlap each other along -their edges or may be joined together with mechanical means there. A~y convenient way of joining the members may be used~ ~y way of example9 mechanical joining means is illustrated in Figs.
lB and lC. In these illustrations9 the respective edges of the s-trips 11 are given flanges bent upwardly and -the ~langes are secured together with a covering member lla and the intermediate members 13 by fastening means such as bolts and nuts. Also3 each lower end of the intermediate members 13 is coupled with the corresponding tension member 12 by a plate 13a and ~as-tening means such as bolts and nuts7 the tension member 12 being clamped by the member 13 and the plate 13a. In the jo:ining construction illustrated in ~igs.
lB and lC9 difficulty may be encountered in making the uprlgh-t flan~es o~ the strips :Ll and covering members lla conform to -the curved sur:face as illustrated in l~lg. 1~ and, to elimina-te s~lch a problemt a suitable number o~` cu-touts or corrugations may be provided wi-th an appropriate pitch along the longi-tudinal direc-tion. The covering member lla need not neces-sarily be me-tal and flexible tapes may also be used for the same purpose as the covering member lla. In the illustra-tions9 -the flanges were bent upwardly9 however9 they may be bent downwardly.
In Figs~ 2A and 2B, there are shown a plan view and a side view9 respec-tively9 of another embodiment of the presen-t invention ~hich is applied to a roof 20 of a circu-lar plan. In the roo~ 209 a top surface 21 and lower -ten-sion grid 22 are secured to a circular rigid ring 24 by any suitable means so that they are placed under -tension with each o-ther through a plurality of in-termediate members 23.
The top surface 219 in this embodiment is arranged to comprise a first group o~ strips 21a and a second group of strips 21b9 -the s-trips being parallel in each group bu-t substantially perpendicular to the strips in the other group.
Also9 the tension grid 22 comprises two groups of wires 22a and 22b, -the wires 22a being parallel to the s-trips 21a and wires 22b being parallel to the strip 21b whereby wires 22a are substantially perpendicu.lar to wires 22b. The strips 21a, 21b and the wires 22a9 22b may be secured to the _ ~ ~L$a ~ 7 circular ring 24 by any suitable means. When they are secured through means for applying tension such as turn buckles or combination of bolts and nuts9 they may be stretched easily.
In Figs. 2C9 2D and 2E, several fragmentary views showing one of the examples for joining -the members of the embodiment illus-trated in Figs. 2A and 2B. The intermediate member 23 is shown as a pipe member having stud bol-ts and nu-ts at the opposite ends to be coupled with mounting plates 23a and 23b9 respectively. The plate 23a is secured to the strip 21b by means of stud bol-ts and nuts identified by reference 23cg the s-tud bolts of which may extend through the strip 21b wi-th their heads smoothed so as to facilitate stre-tching the strip 21a overlying on the s-trip 21b. The pla-te 23a may also be a-ttached to -the under side of the strip 21b by a suitable adhesive. While in Fig. 2C3 the strips 21a are illustra-ted so as to be disposecl side by side9 they may be overlapped along the edges. The lower plates 23b are coupled wi-th the crossing wires by means of "U" bolts 23d9 23e and nuts9 as shown. By the joining construction illustrated in Fig. 2C9 the tension may be applied to the top surface 21 and the grid 22 by adjusting the length of opposite ends bolts and nuts of the intermediate member 23.
The roof 21 is supported by9 for example9 a plurality of columns or posts 25 along the ring as illustrated in Fig. 2B.
Although in the embodiment illustrated in Figs. 2A
through 2E9 the roof surface 21 comprises two groups of strips 21a and 21b 9 it may be constructed by a single group ., , 7~

o strips. However9 double layered strip construction illustrated and explained in connection with Figso 2A
through 2E is preferably employed when -the boundary frame is symmetrical with respect to the two or-thogonal axes of -the :~rame.
In Figs. 3A through 3D, a third embodiment of the present invention is illus-trated. A roof 30 of this embodiment is given a saddle shape and comprises a boundary frame 34, a group of strips 31 and a group of strips 32, -the strips 31 substantially transversing the strips 32~
In this embodimen-t9 intermediate members are omitted and the strips 31 and 32 effect -tension directly on each other.
For installing the strips 31~ 329 it is preferable to first dispose the group of strips 31 sO that each end of the strips 31 is secured to the frame 34 in a manner approximating the final saddle shape of the roo~ 30~
Then the group o~ strips 32 is mounted in the frame 34 sO
that -the strips are s-tretched over the group of strips 31, applying tension on themselves as well as on the strips 31.
When the strips 31 and the strips 32 are tensioned enough, the structure of the roof 30 becomes stable. The roof 30 is supported9 in a manner similar to that shown in Fig. 3B, by plural columns or posts 35~ By the construction of the third embodiment9 the intermediate members required in the t?irst and third members are eliminated to transmit the tension on each other between the upper members and the lower members.
One of the examplesof -the joining and stretching 3`~7~

the end of the strip 32 to the frame 34 is illustrated in Figs. 3~ and 3D~ The end Of the strip 32 is clamped between a pair of pla-tes 32a and fastened together therewith by a sui-table number of bol-ts and nut,s. ~-t -the center of the plates 32a9 another pair of plates 32b is provided so as to ~`asten ~n end rod 32c at the opposi-te end. The end rod 32c is extended -through the frame 34 and arranged to be pulled outwardly by rotating a nut 32d orl the rod 32c.
In Fig. 49 there is shown a tower 40 as a fourth embodiment according -to the present invention9 the cur~ed surface of which being a hyperboloid of one sheet. In this -tower 409 the intermediate members are also eliminated and a group of strips 41 are prestressed. rrhe opposite ends of the strips are secured to an upper frame 44a and a lower frame 44b9 respectively. A plurality of concentric rings 42 are disposed on the outerside of the strips 41 so that the rings are in the planes each perpendicular to the vertical axis of the -tower 40. The respective diameters of the rings 42 are na-turally different to conform -to -the hyperboloidal surface and retained in the respecti~e posi-tions by suitable retainers, such as fittings on the surface of the strips so as not to be displaced down or up due to the tension applied on the strips 41. There are several ways to apply tension on -the strips 41 as w211 as on the rings 42. For instance9 if the upper and lower frames 44a9 44b are initially positioned as shown in Fig. 4 by a post 45 to maintain their relationship9 the s-trips 41 may be easily secured at opposite ends to the frames 44a and 44b ', '''' ' ' , .

~ ~ ~J~

lea-~ing slack in each strip. Thereafter, at the respective heigh-ts9 the rings are tigh~ened properly by such as using turnbuckles until the tensile stress reaches a proper amount in each of the s-trips 41 which also effects -tension on each of the rings 42. Alternately, -the up~er frame L~4a may be a-t first place~ in a lower position and the strips 41 and the ring~, are all lns-talled in that position. Then, if the upper frame L~4a is raised to a predetermined heigh-t, the strips 41 and the rings are stressed. In the construction of the fourth embodiment, the intermediate members are not employed to apply the tension on the strips and the tension members, i.e. the rings in this case.
In the foregoing, -the group of members forming the curved surface and the group of tension members are applied with tension mechanically in such a manner -tha-t both groups have effec-t on each other through intermediate members or direct contact therebetween.
In the embodiments hereinafter to be explained9 fluid is employed as means for transmitting tension from Z0 one group to the other group and vice-versa.
In Figs. 5A and 5B, a fif-th embodiment according to the present invention is illus-trated as a roof 50. The construction of the roof 50 is somewhat similar to that of the roof 20 sho~n and described as the second embodiment o~
the present invention. The top surface 51 comprises two groups of strips 51a and 51b which are arranged and secured to a boundary frame 54 in a manner similar to tha-t of the top surface 21 of the second embodiment shown in Fig~ 2A.

_ 14 _ The lower surface 52 is constructed in the same way as -the upper surface 51 and comprises two groups of strips 52a and 52b. In Fig. 5B~ a section of the roof 50 is illustrated.
As shown in Fig. 5B, an airtight envelope 56 preferably o~ synthetic material is disposed and when pne~a-tic pres-sure is appl;ied ~rom a pneumatic pressure source 57, such as a blower or compressor~ to a space 53 between the sur~aces 51 and 52, -the space 53 being the inside of the envelope 56 in this case, the envelope 56 is inflated until it substantially and uniformly pushes out the surfaces 51 and 52 to their ~inal shapes and the tension is applied on the strips 51a, 51b and 52a, 52b -thereby the roof 50 becomes stable by the pre-stressed strips. The envelope 56 may be eliminated if an appropriate sealing means is applied betweeen the frame and strips and also between each adjacent strip so that the sealing may not interfere with the movement of strips upon applying the pneumatic pressure into -the space 53. Such sealing means may be an elastic packings disposed between each of the strips and between the frame and the strips. Also, alternately, if the internal pressure is maintained by constantly supplying compressed air from the source, the envelope 56 or the sealing means may be omitted depending on -the overlapping condition of the strips and the connection at the frame.
As shown in Fig. 5A, the strips 51a and 51b are arranged parallel in the same groupJ respectively, but the direction of each group transverses that of the others.
This is the same in the groups of the strips 52a and 52b.

, .

87'7 However, it will be apparent that there is no need to consider the direction of the groups between -the surfaces 51 and 52 for the pneumatic type shown in Figs. 5A and 5B
though the gro~lps of upper sur~ace and the lower surface are illus-trated in parallel and orthogonal in Fig. 5A.
The structure of -the ~ -th embodimen~ may be referred -to as a pneumatic metal membrane type.
In Fig. 6, a sixth embodiment of the present invention which may be a roo~ 60 of a pneumatic metal membrane type.
An upper surface 61 and a lower surface 62 are almost the same as the sur~aces 51 and 52 in construction, respectively.
For instance, the upper sur~ace 61 comprises two groups of strips 61a and 61b orthogonally arranged with respect -to each other and -the lower surface 62 comprises two groups of strips 62a and 62b also or-thogonally arranged each otherO
However, they are mounted on a ~rame 64 having a certain height as shown in Fig. 6. In this embodiment, the portions between -the adjacent strips are sealed and the po~tions connecting the strips to the frame are also sealed so as to make an inside space 63 of the roof 60 airtight. When the inside space is connected to a vacuum source, i.e. if the inside pressure is lowered below the atmospheric pressure, the strips in the upper and lower surface are tensioned thereby stabilizing the shape and rigidi-ty o~ the roo~ 60.
If the negative pressure o~ the inside space 63 is constantly maintained by using such as a vacuum pump, the sealing touched upon above may be partially or entirely eliminated.
In this case also, fluid under negative pressure within the ~L~3~7 space 63 serves as an intermediate medium to transmit the ~orce between the group of upper strips and the group of lower strips.
A seventh embodimen-t o~ the presen-t invention is :illustrated as a roof 70 having a rec-tang~llar shape as illustra-ted in Fig. 7A. In this embodiment, a group o~
strips 71 forming the upper surface and a group of strips 72 forming the lower surface are arranged to be parallel to the shor-ter edge of the rectangular shape. If the frame is square9 the upper strips and the lower strips may be orthogonally arranged with respect to each other. Further, in such case, the upper surface may be constructed as a double layer similar -to that shown in Fig. 2A or Fig. 5A~
Also, in Fig. 7B9 a modification of the roof 70 is illustrated as a roof 70' -the four corners of which are trimmed off.
This trimming makes it easy to employ a double layered surface in the upper and lower por-tions9 respectively. The same reference is given to the members similar to that shown in Fig. 7A except with adding prime thereto, respectively and the double layered strips are given additional reference "a" and "b" in a similar way to that shown in Fig. 5A.
In the roof 70' 9 the direction of the strips may be made in orthogonal arrangement as shown.
Figs. 8A and 8B show an eighth embodiment of the presen-t invention in a plan view and a side view, respec tively. This embodiment is also of a pneumatic metal mem-brane type constructed as a part of spherical shape.
In this spherical structure 809 each of the strips 81 is joined at the opposi-te ends to a circular ground member 8L~a and a top disk member 8L~b9 respectively, so that a group o:E strips 81 are radially arranged as shown in Fig. 8A.
~e~ore applying -the internal pressure, the structure may be laicl down in nearly :~lat sta-te on -the ground due to the thinness o~ the strips 81. Wh~le in such state, there is preferably disposed an airtigh-t membrane 86 underside the structure 80, the membrane being suitable to conform to the shape of the erec-ted structure 80. With the arrangement aboveg each of the strips 81 is stressed substantially in the longitudinal direction thereof to stabilize the structure when the membrane 86 is gradually infla-ted by applying pneumatic pressure from a source 87 such as a blower or compressor. The longitudinal edges of the s-trips 81 may be mechanically joined with the edges of the adjacent edges.
Such mechanical means is illus-trated in Fig. 8C. The opposite edges of the strip 81 are provided with upright flanges 81a9 respectively, and the adjacen-t flanges 81a are brought together over which a pre-formed stringer member 85 is placed to sandwich the two flanges 81a and fastened together by means of bolts or rivets.
Since the surface of the completed structure 80 is given a curvature resembling part of a sphere, the stri~ger member may be given cutouts 85a or wrinkles 85b with an appropriate pitch along the longitudinal direction thereof so that the stringer easily conforms to the completed shape of the structure. The stringers 85 may be installed to the structure after the internal pressure is applied9 however~ they may be installed when the structure is in a nearly flat s-tate preferably around -the central area thereof before applying the pne~atic pressure, since such pre-installation saves necessity of a huge scaffold. In the range such as easily accessible from the ground, the installation of the stringers 85 is preferably e~fected after the structure is pressuriæed and stabilized. The stringer 85 may be prepared in a suitable length and extended to a desired leng-th by longitudinally joining two or more. The connection between the disk 84b and the strips 81 may be made similar to that illustrated in Fig~ 8C
by providing the upright flanges for the both.
At the time of installing the mechanical joining means such as illustrated in Fig. 8C, sealing material may be applied to the mating surfaces of the flanges 81a and/or between the flanges 81a and the stringer 85. The stringer 85 may be replaced with a flexible tape. If this sealing material is applied, the membrane 86 may be removed after erec-tion is completed.
The structure 80 is conveniently provided with a gate 88 in which a movable barrier is preferably arranged to maintain the internal pressure while permitting going in and out. An example of such ~arrier is a revolving door 89 or at least two doors arranged in series in the passage through the gate for al-ternately opening and closing the gate 88.
The ground frame may be made o~ reinforced concrete with suitable fi-ttings to connect the ends of the strips 81.

~ ~v In -the foregoing explanation9 the membrane 86 is explained as means for inllating -the structure to its final shape and tensioning the strips even -though the membrane may be removed, ~owever, -the membrane is not necessarily required. For instance, if the sealing means is applied to the por-tions of the structure such as along the adjacent longitudinal edges o~ the strips and the portions connected to the disk 84b and the ground frame 84a, the membrane may be unnecessary Such sealing may be accomplished by apply-ing deformable sealing material such as rubber3 plasticmaterial or the li~e at the respective junctions of the members concerned.
The sealing referred to above may preferably be omitted par-tially or entirely if the capaci-ty o~ the pres-sure source is enough to main-tain the internal pressure.
This may also enable to eliminate a ventilation system which is required in case the sealing is perfect and the inside space is utilized by human beings.
The strips 81 radially mounted may also overlap each other along the longitudinal edges. Also, the shape of the structure is explained as a part of a sphere 9 however, t is not limited to geometrical sphere but includes a strus-ture having a cur~ed surface somewha-t resembling the spherical surface.
In the structure 80, the ground sur~ace serves as a member equivalen-t -to a tension member or members explained regarding the embodiments shown in Figs. 5A, 7A and 7B.
The shape of the structure 80 explained referring .
' .

to Figs. 8A and 8B, is briefly explained as part of a sphere or similar shape. In -the s~ruc-ture 80~ the prestress applied to each of the strips is substantially -the tension in the longitudinal direction -thereo:E. Ho~æver, if i-t is desired to apply -tension absolutely only in -the longi-tudinal direction, -the curve of such surface is a-ttained by arrang-ing -the shal].owness ratio (A) o:E-the curved surface to be minimum. That isg such condition satisfying the curved surface of revolution (which is free of wrinkles) in the pnewnatic membrane structure is expressed by -~/2 rl sin ~ d ~

2 -~ min, Jo rl cos ~ d wherein rl is a first primary radius of curvature of the curved surface 9 and ~ is an angle between the axis of rotation and the normal to the surface.
It was proved by -the inventor of the present invention that only one i~A77 exists to satisfy -the above condition which is expressed by the followingO
~ r- (3/4) ~ - ~ = 0.5991 4 r (5/4) wherein ~ is a /~'function.
(Bulletin of International Association for Shell and Spatial Structures~ No. 639 1977) The surface satisfying the above condition is not available as an analytically explicit form but it is given by answers in numerical values.
A modification of the spherical structure 80 is illustrated in F`igs. 8D and 8E as a spherical structure 80' and -the same reference ~s that given to each o:f the similar members of -the struc-ture 80 is given in this modified structure 80' with the addition of prime thereto, respec-tively. Since the functions of the members are the same as those withou-t prime in the structure 80, further explanation is omi-t-ted except for the ground frame member 8~a'. In this casey the frame member may be a wire9 rope9 metal rod9 metal -tube, metal sheet9 etc. and -this member is anchored in the ground where it contac-ts the same. Therefore9 the completely circular reinforced concrete may be replaced with anchors arranged at an appropriate interval. In this construction, some skir-t member sealing the inside space may be necessary.
A gate may be provided similarly to that shown in Figs. 8A ar,d 8B.
In Figs. 8F` and 8G9 a structure 80" comprising spherical portions and a cylindrical portion is illustrated.
The system for constructing the structure and applying the internal pressure is substantially the same as the structure 80 or 80' explained above except for a ground frame 84a~1 which is formed in an oval shape having a pair of parallel side portions at the center thereof and a semicircular portion at the opposite ends and strips are different in shape at the center and the ends, so fur-ther detailed ~ 22 -description is omitted and the same reference is given to each of the members with addition of the double prime, respec-tively as -those in Figs. 8A9 8~ and 8D, 8E though the s-trips 81" are given different shapes at the opposite ends and the center portions.
~ s explained in the above 9 the present invention provides several s-tructures u-tilizing me-tal sheets as their important me~bers in the form of strips substantially as they are produced or requiring only slight trimming or forming, so -the cost in construction is greatly reduced in combination wi-th o-ther advantages such as no necessity for a large scaffold~ Also 9 the metal strips may be joined or may no-t be joined each o-ther. In joining them, other means not specifically explained hereinabove such as welfling, rivetting may be used.
In the practical application of the metal strips 9 -the ma-terial, width and the thickness are determined depend ing on the using condition, clima-te of -the place where the structure is erected, si~e of the structure and economical availability of the strips in the marke-t. For ins-tance, the thickness may range from under 1.0 m/m to 10 m/m. In the spherical structure shown in Fig. 8A3 if the diameter is approximately 10 meters, the thickness of the strips would be 0.3 m/m and it increases to 10 m/m when the diameter reaches 200 m. These dimensions are only for examples.
The invention has been explained in detail referring to the specific embodiments 9 however9 the invention is no-t 7~
- 2~ -limited to those explained and the modification and changes would be readily available -to those skilled in the art within -the spri-t and scope of the invention defined in the appended claims.
For example, an insulation layer may be applied on the inner surface of the metal strips -to provide tempera-ture isola-tion be-tween outside and inside of the s-tructure3 Such insulation layer may be applied when the strips are flat or after the erection is over.

Claims

The embodiments of the invention in which an exclusive property or provilege is claimed are defined as follows:

1. A tension structure comprising:
a boundary means;
a group of elongated metal strips arranged side by side substantially without means for transmitting force between the adjacent strips, each thereof being secured at opposite ends in a longitudinal direction thereof to said boundary means; and means for applying tension to each of said metal strips substantially only in said longitudinal direction to form a stabilized continuous curved surface by said strips.

2. A tension structure comprising:
a boundary means;
a group of elongated metal strips arranged side by side substantially without means for transmitting force between the adjacent strips, each thereof being secured at opposite ends in a longitudinal direction thereof to said boundary means; and means for applying tension to each of said metal strips substantially only in said longitudinal direction to form a stabilized continuous curved surface by said strips, said means including:
a group of tension members having a curvature opposite to that of said curved surface; and a plurality of intermediate members disposed between said metal strips and said tension members;
said metal strips and said tension members effecting tension on each other through said intermediate members.

3. A tension structure comprising:
a boundary means;

Claim 3 continued .....

a group of elongated metal strips arranged side by side substantially without means for transmitting force between the adjacent strips, each thereof being secured at opposite ends in a longitudianl direction thereof to said boundary means, and means for applying tension to each of said metal strips substantially only in said longitudinal direction to form a stabilized continuous curved surface by said strips, said means including another group of metal strips opposing said first group to provide a space therebetween and pneumatic pressure applied to said space, said strips in both groups being partially overlying each other at their longitudinal edges.

4. A tension structure comprising;
a boundary means;
a group of elongated metal strips arranged side by side substantially without means for transmitting force between the adjacent strips, each thereof being secured at opposite ends in a longitudinal direction thereof to said boundary means; and means for applying tension to each of said metal strips substantially only in said longitudinal direction to form a stabilized continuous curved surface by said strips, said means including another group of metal strips opposing said first group to provide a space therebetween and pneumatic pres-sure applied to said space, sealing being applied between the adjacent strips in the same group, respectively and the portions where the ends of said strips are secured to said boundary means.

5. A tension structure as claimed in claim 3 wherein said strips in each of the two groups are arranged in two layers, the strips in each layer being arranged to be parallel but orthogonal to the strips in the other layer.

6. A tension structure having a curved surface which is a shape comprising entirely or partially a curved surface of revolution the axis of which is vertical, said structure comprising:
a boundary means including a ground frame of a closed figure and a circular or semi-circular sheet metal the center of which is disposed coaxially with said axis of revolution, a group of elongated metal strips arranged side by side substantially without means for transmitting force between the adjacent strips, each of strips forming said surface of revolution being radially disposed around said axis between said sheet metal and said ground frame and secured to said ground frame at one end and to said sheet metal at the other end, each of strip forming the portion other than said surface of revolu-tion being secured at opposite ends thereof to said ground frame; and pneumatic pressure means for applying tension to each of said metal strips substantially only in said longitudinal direction by introducing pneumatic pressure inside between the curved surface and the ground surface to form said curved surface as a stabilized continuous curved surface.

7. A tension structure as claimed in claim 6 wherein said surface of revolution is of such shape as satisfying the follow-ing equation:

min.

wherein .lambda. is a shallowness ratio:
r1 is a first primary radius of curvature of the curved surface; and

Claim 7 continued .....

.PHI. is an angle between the axis of revolution and the normal to the surface.

8. A tension structure as claimed in claim 7 wherein said .lambda. is given the following value;

= 0.5991 wherein is a function.

9. A tension structure as claimed in claim 6 wherein said strips are partially overlapped each other between the adjacent ones at the respective longitudinal edges.

10. A tension structure as claimed in claim 6 wherein sealing is applied to the portions between the adjacent strips and between the ends of the strips and said boundary means so as not to transmit lateral force each other between the adjacent strips.

11. A tension structure as claimed in claim 6 wherein said ground frame is constructed to have two parallel side portions provided with circular curves at the opposite ends of said side portions to complete the closed figure, said strips comprising radially arranged strips at said opposite ends and strips arranged in parallel each other but normal to said side portions, said strips being formed to have a complex curved surface of cylindrical shape at the parallel side portions and a surface of revolution at each of opposite ends when pneumatic pressure is applied to a space between the strips and the ground surface.

12. A tension structure as claimed in claim 6 wherein a flexible membrane or envelope is disposed inside of the structure, the shape and size of said membrane or envelope being such that

Claim 12 continued .....

when pneumatic pressure is applied, said membrane or envelope is inflated to inscribe the metal strips formed to have said curved shape.

13. A tension structure as claimed in claim 12 wherein sealing is applied at the longitudinal edges of the strips between the adjacent ones and at the ends secured to said boun-dary means, said membrane or envelope being arranged to be removable after the pneumatic pressure is applied to fully tension the respective strips.