US 3708944 A
A stressed arch fabricated from a plurality of prefabricated structural frame members assembled over a flexible strand which is tensioned for causing the frame members to coact and assume an arch configuration and a method of making same are disclosed. Joint members may be added between each of the frame members. A plurality of connected or intersecting arch configurations may be covered by siding and roofing materials and erected simultaneously to provide a complete building suitable for permanent use or for easily disassembled portable use.
Description (OCR text may contain errors)
United States Patent 1191 1 51 Jan. 9, 1973 Miyake I 1541 METHOD OF MAKING AN ARCH  In entor: Minobu Miyak'e, 194 of' 1 Shimoshakuji, Tokyo, Japan 22 Filed: Feb. 20, 1970 21 Appl.No.:13,003
 Foreign Application Priority Data Oct 31, 1969 japan ....44/8739o  v U.S. Cl. ..52/745, 52/86, 52/227  Int. Cl. ..E04b 1/32  Field of Search ..52/74l, 742, 747, 222, 227,
[5.6] Re[erencesCited UNITED STATES PATENTS 2,818,009 12/1957 Steffen ..1...52/302 3,120,682 '2/1964 Reffell.....;.... 3,354,598 11/1967 Nicholson.... 3,401,492 9/1968 MacDonald..
9/1970 Cohen ..52/741 X 1,312,065 8/1919 Wakefield ..52/86 1,976,188 10 1934 Nozawa.; ..52 81 2,733,432 2/1956 D'omaii..... ..52/86 2,874,812 2 1959 Clevett ..52/86 3,057,119 10/1962 Kessler ..52/64 3,333,375 8/1967 Johnston 352 81 Primary Examiner-John E. Murtagh AttorneyFidelman, Wolffe & Leitner  ABSTRACT A stressed arch fabricated from a plurality of prefabricated structural frame members assembled over a flexible strand which is tensioned for causing the frame members to coact and assume an arch configuration and a method of making same are disclosed. Joint members may be added between each of the frame members. A plurality of connected or intersecting arch configurations may be covered by siding and roofing materials and erected simultaneously toiprovide a complete building suitable for permanent use or for easily disassembled portable use.
7 Claims, 24 Drawing Figures 2 PATENIEDJAI 9:975 3.708.944
SHEET 3 [IF 7 v I PATENTEIJJAI ems I 3,708,944
' SHEEIUUF 7.
METHOD OF MAKING AN ARCH FIELD OF THE INVENTION The present invention relates generally to permanent or temporary structural constructions and methods for assembly and erection of the same. More particularly, the present invention relates to prefabrication, assembly and erection of structural components comprising, when erected, a tension arch structure suitable for use as a temporary -or permanent framing for supporting a dwelling or other suitable building. In practice, a plurality of substantially rigid hollow structural componen ts are slidably, serially provided over a flexible wire, strand, cable or rope. Under application of a tension force to the rope, the structural components are forced into abutting relationship. The tension force on the rope causes the structural components to coact and exert mutual pressure and stress upon adjacent abutting structural components. Such coaction results ina stressed tension arch comprised of the coacting structural components. The resulting tension arch may then be erected in a single operation which is greatly simplified since the arch is prefabricated and assembled prior to erection.
BACKGROUND OF THE PRIOR ART hoisting equipment. Furthermore, conventional structural components, when prefabricated, are bulky and relatively fragile causing difficulty in transportation I thereof to the construction site and in precisely locating such components for erection at the site.
BRIEF DESCRIPTION OF THE INVENTION The present invention includes structural components which may be standardized as to shape and dimensions, and which may be assembled together with conventional fastening techniques. Assembly and subsequent disassembly ofthe components may be accomplished quickly and on the ground at the construction site, thereby permitting adjustment or changes in the profile or height of the resultant structural configuration. Further, the arch may be subsequently erected without a need for laboriously assembling the same directly upon its final erection site. Such advantage eliminates the need for auxiliary equipment, such as scaffolds and hoisting apparatus for positioning each cornponentas the construction is formed.
Transportation of the components to the construction site issimplified, since assembly is accomplishedat the site. Additionally,adjustmentand positioning of components for assembly are easily accomplished beforeerection to a final structural configuration.
The present invention provides a light, strong, economical structural construction which-isv readily. adapted for meeting the structural static and dynamic considerations required of permanent installations for general use, such as aircraft hangers, warehouses and factory buildings. Such a construction according to the invention departs from the past concept of immovable structures, since the invention is suitable for disassembly into easily transportable structural components while satisfying commercial requirements of permanent general use type buildings when erected.
In practice, a plurality of prefabricated, elongated hollow frame members of standardized construction are serially and slidably assembled over a strand of flexible wire, cable or rope with intervening joint forming members between adjacent frame members being also provided slidably over the strand. 7
Spaced anchors are provided at the construction site. One end of the strand is secured fixedly to one anchor, and the strand of the other end is passed through an apertured portion of another anchor. A suitable force applying machine, such as a winch, applies tension forces to the strand forcing the frame members to assume a stressed arch configuration, hereafter also referred to as a unit member, which configuration is especially determined by properly positioning frame members of selected shapes and dimensions in the assembly. The frame members if desired may be joined to the joint members by conventional fastening techniques subsequent to erection of the stressed arch configuration resulting in a permanent installation. If joining is not desired for ease in disassembly, tension may be maintained on the strand after erection of the resulting arch. To construct a complete frame suitable for supporting building panels or other siding and roofing materials suitable for a building, a plurality of arches must be provided. Such arches, or unit members, may be secured together by rigid spanning frame members supported between joint members provided on adjacent unit members. If desired, the joint members may be dispensed with, in which case, the frame members and spanning members may be connected directly to one another, again by suitable conventional fastening techniques. Additionally, the adjacent arch configurations may be intersected without a need for the spanning members. i
OBJECTS OF THE INVENTION An object of the present invention is to provide a simplified erectable structural construction fabricated from a plurality of standardized components adapted for assembly prior to erection of the resultant structural construction and a method ofmaking the same.
Another object of the present invention is to provide a simplified construction of readily assembled and disassembled structural components resulting in a permanent or temporary structural construction.
Still another object ofthe present invention is to providea plurality of structural components serially over a flexible strand such that upon application of tension forces to the strand, the components coact to form a tension arch. I
A further object of the invention is to provide a plurality of structural components which are light, strong, easily transported, adapted for assembly and disassembly with conventional fastening techniques and Other objects and. attendant advantages of the present invention will become apparent from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a preferred embodiment of the invention illustrating a plurality of structural components in an initially assembled condition and also inan erected unit member or stressed arch configuration subsequent to assembly;
FIG. 2 is aschematic view showing exemplary intermediate positions attained by the embodiment shown in FIG. 1 during erection thereof;
FIG. 3 is a side elevation similar to FIG. 1 of another preferred embodiment of the present invention utilizing a movable anchor and shown illustrated in an as sembled condition and in an erected condition;
FIG. 4 is a schematic illustration, similar to FIG. 2 of exemplary intermediate positions assumed by the embodiment shown in FIG. 3 during erection thereof;
, FIG. 5 is a side elevation illustrating another preferred embodiment of the present invention shown in two ofany number of erected configurations;
FIG. 6 is a side elevation of a unit member, formed "with a plurality of frame members without any joint members, and with parts shown partially in section to illustrate particular details of construction and further showing a mode of operation in the practice of the invention;
FIG. 7 is a side elevation ofa unit member fabricated from frame members and intervening joint members illustrating a mode of operation in the practice of the invention',
FIG. 8 is an enlarged fragmentary view illustrating in detail, and with parts shown partially broken away and in section, exemplary frame members utilized on the embodiment shown in FIG. 6;
FIG. 9 is an enlarged fragmentary elevation with parts partially in section to illustrate in detail an exemplary frame member of the embodiments illustrated in FIGS. 1-5 and 7;
FIG. 10 is an enlarged fragmentary elevation with parts partially in section to illustrate in detail another exemplary frame member;
FIG. 11 is an enlarged fragmentary elevation of an exemplary joint member utilized, for example, in the preferred embodiments shown in FIGS. 1-5 and 7;
FIGS. 12 and 13 are enlarged fragmentary elevations of modified exemplary joint members of the one shown in FIG. 11;
FIG. 14 is an enlarged-fragmentary elevation of an anchor showing the particular details and operation thereof;
FIG. 15 is a side elevation, with parts partially broken away, to illustrate a completed structural installation fabricated from a plurality ofjoined unit members such as those shown in FIGS. 1-4, 6 and 7;
FIGS. l6, l7 and 18 are side elevations with parts partially broken away to illustrate modifications of the completed structural installation shown in FIG. 15; and
FIGS. 19-24 illustrate various embodiments of joint members as applied in the embodiments shown in FIGS. 1548.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. I of the drawings, the basic operation principles of the present invention are illustrated. A pair of spaced, anchors or base members R (having a pedestal 35 thereon) are fixedly secured at points X to the ground or to any suitable planar base surface A, at a construction site. A plurality of straight elongated hollow prefabricated frame members 22 or 23 are serially assembled over a flexible strand 1 (FIGS. 1, 5-8) with joint members 31 interposed between adjacent frame members. With the strand 1 in itially secured to the anchors R and under no tension forces, the assembled frame members 22 (23) and joint members 31 comprise structural elements which as sume a random relaxed configuration, such as the one particularly shown at I (FIGS. 1,2). However, when tension forces are applied on the strand 1 by utilizing a machine (not shown in FIG. 1, but shown as R in FIG.
14), such as a winch, the assembled components coact to form a stressed arch, as shown at Ill (FIGS. 1,2). The particular arch configuration arises from a proper selection of the lengths of frame members 22 (23) and joint members 31 utilized and the spacing chosen for the fixed anchors R.
FIG. 2 shows in schematic the exemplary progressive positions of the frame members 22 (23) and joint members 31 as tension forces are progressively applied to the strand 1. Thus, when relatively little tension is on the strand 1, the assembled components may assume the initial position I (FIGS. 1 or 2). As additional tension forces are applied on the strand 1 by a wi'nchtnot shown), for example, the frame members 22 (23) and joint members 31 will be forced into abutting contact with one another, coacting and exerting mutual pressure and stress upon adjacent abutting structural components 22 (23) and 31. Accordingly, the effective length of strand 1 over which the components 22 (23) and 31 are assembled progressively decreases, forcing the components 22 (23) and 31 to arrange themselves in an intermediate, partially erected arch configuration as shown at II (FIG. 2). Tension is further progressively applied to the strand 1 until the assembled components 22 (23) and 31 assume a fully erected arch configuration as shown schematically at III (FIG. 2).
FIG. 3 illustrates a modification ofthc preferred embodiment of FIG. 1, wherein one of the anchors R is movably mounted, for varying the shape of the finally erected arch configuration, or for a modified technique in erecting the arch configuration.
Accordingly, the Figure shows a fixed base member or anchor A provided with a force applying machine such as a-winch (not shown), and fixed at point X. Another base member R is movably mounted at point X. A strand 1 secured to the anchor at X extends to he fixed anchor R at point X and is operatively connected to the winch (not shown). Structural components, including frame elements 22 or 23 and joint elements 31, are shown serially assembled over the strand 1. In operation, the winch (not shown) applies a desired degree of tension to the'strand l causing the assembled components 22 (23) and 31 to coact, as heretofore explained, and assume a relatively flat arch configuration as indicated at II in FIG. 3. With the tension maintained on the strand 1, the movably mounted anchor R is moved from right hand point X to the left cordingly, themovable base member R may be utilized to select the shape of the finally erected arch configuration or as an alternatelte'chnique for erecting the structural components 22 (23) and 31 to a desired arch configuration. v
To more particularly illustrate the erection technique, reference will be made to FIG. 4, wherein the movableanchor at X is provided with unstressed structural components 22 (23) and 31 which assume a random configuration such as the one indicated at I. Tension forces are applied to the strand 1 'until a desired level of tension is attained, causing the structural components 22 (23) and31 to coact, as described hereinbefore, and form a relatively flatarch configurais moved progressively toward an adjacent relationship to the fixed anchor X, the arch configuration changes height. and shape, as indicated at III and IV (FIG. 4).
Thus, the movable anchor technique isused advantageously to erect or, to adjust the final shape of the desired archco nfiguration. I
FIG. 5 further emphasizes the change in shape of the arch configuration uponmoving the movable anchor R. In the Figure, left hand X indicates the initial positionof the movable anchor R with the initially stressed structural components assuming an arch configuration shown at l (FIG. 5). Upon moving the anchor R to a position right hand in adjacent relationship to the other fixed anchor R, the archco nfiguration may be caused to vary from relatively flat to circular.
With reference now being made to FIG. 6, there is' 6 frame members 61 will abut, as shown in FIG. 6, in complementary engaging relationship without stress concentrations due to irregular engaging surfaces. Such .a construction is further advantageous, since no intervening coupling members 31 between-adjacent frame members 22(23 is required. A roof B is shown applied to the arch in FIGS. 6, 8
As shown m FIGS. 9-14 and 19 -24,addlt ional frame members, modifications, of the frame members 21, are illustrated at 22' (FIGS. 9', 11-13, 1547, 19-22 23' and 24 (FIGS. 10, 1143), respectively. Each end of each frame member 22', 23' br 24 is provided with flanges 62. Each flange 62 may be formed integrally with the respective frame member 22, 23', 24 or, as
more particularly shown in the drawings, provided on one end of a separate relatively short tube' 6 ma'tingly engaging the respective frame member 22', 23 or 24. Each flange 62' is preferably perpendicular to the longitudinal axis of its respective framemernber 22', 23, 24, although other orientations of each flange 62 may vary as desired. Each flange 62 may be provided with reinforcing ribs 6a (FIG. 9)'and a central'opening 5 (FIG. 9, 10) aligned with the hollow cross-section of its respective frame member 22' or- 23' 'to permit passageentirely through 'the flanged frame and 4a (FIGS. -l0, 14).Each flange 62is provided with apertures 5 which communicate with the hollow interi ors of the tubes4, 4a to permit passage of a strand 1 therethrough. In operation, as shown in FIG. 14, each tube 4, 4a is provided with a separate strand 1 I vided with a single ratherthan a pair of tubes 6.- The i An important structuralcomponent utilized in practice of the preferred embodiments include elongated hollow frame members 22 (23) adapted to be serially slidably assembled over the strand 1 as shown in FIG. 6. The frame members 22 (23).are'preferably of metal, synthetic resin, bamboo or similar materials which are rigid, resistant to crushing under pressure and or rela-'' tively highs'trength. Although a tubular cross'section is most commonly used in practicc,. it should be unde rstoo'd that other hollow cross-sectional shapes may be utilized. The particular material selected for .the frame member 22 (23) is based upon considerations of structural strength and conditions under which the members 22(23)are'subjected during use. The frame member 22 (23) is more particularly shown in FIG. 8 with certain prefabricated features.
v form an 'arch configuration, the ends 61 of adjacent flange 62 seats on an inclined'surface of agenerally trapezoidal interposer or adapter pedestal 35 ofhollow interior construction. The interposer 35 (FIG. 14) rests on one leg of a generally, U-shapedbase oranchor R the other legof which is fixed to the construction site ground A or other suitable surface. On the base of and between the legs of the U-shaped member R is mounted a tension applying machine such as a pulley or winch R,,.. The two strands'l extend through the adapter pedestal 35 (FIG. 14) and through one leg and base ofthe U-shaped member to ,operatively engage the winch R,,.. Upon operation of the winch R the strands l are placed in tension so that aplurality offrame members, similar to the doubleframemember 23' and. shown in FIG. 14, coactto produce a stressed arch con flguration'as heretofore described.
I The particular frame member embodiments utilized are prefabricated and are thus able to be selectedupon' a consideration of the planned mode ofconstruction, structural strength requirements. and condition'ssubjected to during use. Any of the frame member embodiments are; compatible for use with the pedestal-35 shown inFIG. 14. V
With reference to FIGS. 11 through 13, one embodiment of a prefabricated joint member 31 is shown. As
heretofore explained, a joint member 31 is selectively interposed'between adjacent frame members 22, 23, 22, 23', or 24in the stressed arch configuration. With reference to FIGS. 11-13, a joint member 31 isshown interposed between adjacent frame members 22' or 23'.- Each joint'm'ember 31 rnaylor may not be selected ofthe same material as the-frame'members 22, 23, 22,
23, 24 and are conveniently utilizedfor attaching the .spanning frame members 8, (FIGSL'IS, l9.), between adjacent arch ,configurations. Eachjoint member is generally of hollow interior trapezoidal configuration with vertically inclined side wall surfaces .71 (FIGS. 11-13), each of which wall surfaces 31 is appropriately FIG. 22 illustrates another modified prefabricated joint member, indicated at 31' andincluding a plurality of flat bearing" sidewalls 71 mutually arranged in a hollow interior 41 polygonal configuration. Each sidewall 71 is abutted by -a frame member 22' and. is provided with an aperture 51 to permit passage therethrough ofa strand 1,for a purpose heretofore described. It is noted that two of the shown abutting frame members 22'. are
not directly opposite other frame members 22. Such frame members 22 are thus included in segmented stressed arch configurations which terminate at the joint-member 31'. Accordingly, in the formation of apertured asshown at 51 (FIG. 12) topermit passage therethrough of a strand 1' for a purpose heretofore described. The pitch of the inclined wall surfaces 71 may be selected for controlling the radius of curvature desired in the final arch configuration formed when the fram e'members 22' or 23 and. the interposed joint members 31 coact in abutting, relationship. Thus, the wall surfaces provide bearing surfaces of adjustable pitches for the abutting frame members 22,-23 as such segmented configurations, the strands l associated therewith is secured, by any well-known technique, tothe. joint member 31', rather than to an anchor R, as heretofore described with regard to nonsegmented configurations. The remaining end (not shown) of the segmented configuration isassociated '-with an'anchor R and a tension. applying means R (FIG. 14), asdescribed, to, result'in the arch configuration, segmented because of its attachment to the joint member 31'. Alternatively, the segmented configuration' rnay'be fabricated'With a single-strand I-as shown .in FIG. ,lL thereby controllingthe iheh aridh of a the frame members 22l,'23 in the arch configuration and-thus the radius ofcurvature of thearch configuration,
Further details-of thejo'int member31 are shownin FIG 19;,Withreference thereto, the hollow interior of the joint member 31 is shown at 41 .provided for accommodating.aspanningframe-member 8 in the form of a rigid, ,bar, of rectangular cross-section. The spanning frame member 8 may be secured to the joint. member 31 by a threadably'driven fastener 81 engaged in the spanningmember 8 to securelylock the spanning member 8 and the joint member 31 together. v v
As heretofore describedythe invention'may be prac-.
ticc'd wit'hout using interposing joint members 31. Ac-.
cordingly, with referencejto FIG. 6, a plurality of spanning members 8 may be secured by' conventional fastening techniques directly tothe': frame members 22 (.23,)', either at the-midpoints '82 of member 22 (23), as shown, or to otherportionsas desired.
With reference to FIGS. 20 and 21, a modified prefabricated joint" member 31 .is shown with four inclined wall surfaces 71 arranged in, a generally rectangular configuration about a hollowinterior portion'41. The joint member 31 is thus used for-connecting four frame members 22" or 23 coverging from difdescribed forthesegmented arch shown in FIG. 21.
FIG. 16 shows a practical application of the joint member 31", wherein aplurality of arch configuration intersect in a lattice'buildin'g structure including a plu-' rality, of'seg'mented arch configurations intersecting and terminating at ajoint member 31. I 'FIGS. 18, 23' and 24 illustrates 1 a modified prefabricated joint member 31'-", interposed between adjacent frame members 24'and provided with a plurality of bearing sidewalls 71 (FIG. 24) arranged mufigurations. Merely selecting thedistances bet ween ferent direction's' and included in arch configurations Y which intersectat the joint member 31. j j
- As shown in FIG. 20, the strand! is passed through holes 51 in opposite sidewalls 71,,wh ereas in FIG. 21, thevstrands 1 'are'pa'ssed through adjacent holes 51' in sidewalls 7l, .to result inan arch'configuration which is notplanar, butsegrriented andmultiplanar with the differentsegment planesthereof intersecting at the frame member 31'.
FIGS; Hand 12 particularly illustrate practical ap plications for the joint member 21 (FIGS; 20, 21)
wherein building panels or similar building structural wall-and roof surfaces B are supported by a plurality of arch configurations'which"intersect, with-joint members 21' (FIGS-20, 21) being provided at the intersections thereof.
' structural installation.
fixedbas'es A, or the arch terminating framemember 33, to be less than the totaleffective length. ofthe as sembled frame members 22, 23, 22, 23, 24 and joint members 31,31", 31", 31 if any are used, will result in an arch configurationlupon applying and maintaining tension forces to a strand 1jover. which. the members 22,23, 22', 23", 24 and-31, 31, 31-, 31' are assembled. The distance between intersections and the shape and .height ofzthe configuration 'ma'y. be adjusted as desired 'by selection of the anchor spacing effective length ofthe strand 1,-effective lengthsof each and the totaleffective combined frame members 22, 23, 22,
233-24 and jointmembers 31,- 31, 31" 31"" used.
Further adjustments are provided bythe typeof joint member 31,31, 31" used,.th e.pitch selected in the walls of abutting frame members 21.
joint membersidewalls and the inclination of the end .-Tension'forces' applied to the'st'rand 1 are-evenl'y'distributed and transferred to all of theframe members 22, 2 3, .22',-'23', 24and joint members 3l, .31, 31",
31 throughout the progressive arch erection as shown in FIGS. 1-5. Since the members 22, 23, 22, 23, 24 are rigid and are immovably seated at the arch termination points X, the effective length of the arch configuration becomes a .minimum upon reaching a corresponding tension level in the associated strand 1. Accordingly, any increase in tension forces applied to the strand 1, such as by wind loads, will not change the effective length or shape of the arch configuration.
All embodiments of the frame members 22, 23, 22, 23', 24, the joint members 31, 31', 31", 31" and the spanning members 8 are prefabricated with the structural features and standardized dimensions as described. Accordingly, the required structural component may easily be selected for incorporation in a specific arch configuration desired.
All of the intersecting or spanning member 8 (FIG. 15) connected arch configurations which are combined to form a building structural installation may be assembled as described, covered with suitable building sheeting or other siding and roofing material B (H08. 7, 16-18, 15) and subsequently simultaneously erected according to the techniques described, to result in a completed building, such as those shown in FIGS. 15-18. Other techniques may be employed during erection. For example, the arch configuration midpoints may-be temporarily supported by removableupright support poles which are subsequently discarded upon erection ofthe configuration to a final position.
' Other embodiments and modifications of the present invention are within the spirit and scope of the present invention as defined in the appended claims, wherein, what is claimed is:
1. A method of erecting a structural configuration comprising the steps of:
a. serially slidably disposing a plurality of frame members provided with planar surfaces on each ,end thereofon a flexible strand, b. disposing joint members on said flexible strand between adjacent frame members so that a joint planar surface on each joint member is disposed adjacent to a planar surface on an adjacent frame member, c. extending a spanning frame member through said joint member, d. anchoring one end of said flexible strand on a foundation, 0. passing the other end of said flexible strand through an anchor on said foundation in a spaced relationship to said one end of said flexible strand, applying tension forces upon said strand to cause said frame members to assume an erected arch configuration with said joint planar surfaces in h. while one of said contacting planar surfaces'is substantially perpendicular to said frame member and a. moving one end of said flexible strand with respect to the other end of said flexible strand prior to applying said tension forces.
3. The method recited in claim 1 including the step of:
a. fastening said spanning frame member to said joint member.
4. The method recited a. passing said flexible strand through opposed joint planar surfaces.
5. The method recited in claim 1 including the step of:
a. passing said flexible strand through a first joint planar surface on said joint member, and b. then passing said flexible strand through a second joint planar surface on said joint member, which second joint planar surface is disposed at an angle less than about with respect to said first joint planar; surface. 6. The method recited in claim 1 including the step a. providing venting means for said structural configuration inon'e of said joint members.
7. A method for erecting a structural configuration comprising the steps of:
a. serially slidably disposing a plurality of frame members on a flexible strand, each member being provided with planar surfaces on each end thereof,
in claim 1 including the step b. disposing-joint members of said flexible strandbetween adjacent frame members so that a joint planar surface on each joint member is disposed adjacent to a planar surface on an adjacent frame member,
c. extending a spanning frame member through said joint member,
d. anchoring one end of said flexible strand on a foundation,
e. 'passing the other end of said flexible strand through an anchor on said foundation in a spaced relation to said one end of said flexible strand,
applying tension forces upon said strand to cause said frame members to assume an erected arch configuration with said joint planar surfaces in contacting engagement with said adjacent planar surfaces and lies substantially on a radius of said arch configuration, and
g. maintaining the tension forces upon said strand at a minimum level sufficient to maintain the archconfiguration.