Note: Descriptions are shown in the official language in which they were submitted.
7 7
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"
-1
: .
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
-- 4 --
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
-- 5 --
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
77
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
-- 10 --
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~
- 12
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~
- 13 -
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
-- 16 --
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
- 17 -
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
77
- 18 -
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
377
-- 19 --
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
.
' .
- 20 -
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)
- 21 -
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.
