US2928360A - Flexural tension framing system and structural unit thereof - Google Patents

Description

E. C. HEINE, JR FLEXURAL TENSION FRAMING SYSTEM AND March 15, 1960 Filed Oct. 16, 1956 STRUCTURAL UNI-T THEREOF 4 sheetshani INYENTOR ATTORNEYS c. HEINE, JR SION FRAMING SYSTEM AND STRUCTURAL UNIT THEREOF March 15, 1960 FLEXURAL 4 Sheets-Sheet 2 Filed Oct. 16, 1956 INVENTOR ATTORNEYS March 15, 1960 E. c. HEINE. JR 2,928,360

FLEXURAL TENSION FRAMING SYSTEM AND STRUCTURAL UNIT THEREOF Filed Oct. 16, 1956 4 Sheets-Sheet 3 FIG.9

' 75 Fl 0. I 0

' INVENTOR ZOLMMA cu gfln *ATTORNEYX March 15, 1960 E. c. HEINE. JR 2,928,360

FLEXURAL TE S ON FRAMING SYSTEM AND STRUC \AL UNIT THEREOF Filed Oct. 16, 1956 4 Sheets-Sheet 4 ATTORNEYS United States Patent FLEXURAL TENSION FRAMING SYSTEM STRUCTURAL UNIT THEREOF Edmund C. Heine, Jr., Arlington, Va.

Application October 16, 1956, Serial No. 616,228 Claims. 01. 108+1) This invention relates to an architectural or structural system for providing anticlastically curved thin shell roofs and compoundly curved-walls and surfaces. The types of tensioned structural units contemplated by the invention are entirely self-contained, in stable equilibrium and adapted to a wide variety of uses in the general building industry. 7

More particularly identified, the system involves the primary concept of initially placing a generally curved peripheral member under tension, thus subjecting it to its inherent forces of expansion, in such manner that the entire unit may be described as substantially a tension system throughout. Such results in the formation of a unit, when viewed either in section, in elevation or in plan, as one comprised of a multitude of contiguous, parabolic, or nearly parabolic, curvatures. broadly descriptive of my invention and prior to a more detailed disclosure thereof, the novel system might be defined as follows: firstly, one made up of a continuous peripheral member so curved in the fiat plane as to circumscribe given area requirements by a series of parabolic curves. This peripheral member is so deformed or deflected normal to, or approximately normal to, such flat plane and in such varying degrees as to obtain a sec ond group of parabolic curves. 7

Secondly, the deformation of the peripheral member is attained by a network'of metal tapes, cables or similar tensionable materials which are primarily and initially secured from a point at or near the respective high points of such peripheral member to a point near or at an opposite point on such periphery. Such tension means, as, for example, steel tapes, thus deflect successive points of the peripheral member in opposite directions roughly normal to a flat plane. They are so crossed with respect to each other as to exert relative compressive forces against each other at their points of contact, or their crossing points. By this system of development of successive paraboliccurves in the peripheral member and throughout its intermediate area, the plane developed will be one approaching various contiguous saddle shaped planes. The depths of these are actually functions of the lengths of the various tape or cable components or, stated differently, are the functions of the amount of tension placed upon the various tension members running from one part of the circumference of the peripheral member to another part thereof. At any rate, the completed unit is one in a permanent state'of stress due to the bending and compressive forces referred to above.

This structural system is unique, over known architectural and engineering forms in that the periphery is under tension, the shape-retaining elements are under tension, and the only forces of compression which are at work are those resulting from the opposed forces exerted at the intersections of the various framework or tension members. The foregoing statement is subject to the qualification that the system of this invention is a tension system in its entirety when lighter weight materials, such as'splastic, etc, .are used, or, in any case, where the ten- As further sion developed in the various components of the system done,.the dead load 'or weight of such fill overcomes the purely tensional aspect of the peripheral member, or its tendency to expand outwardly. Thus, when heavy materials are employed, this member becomes one existing in compression, the tension developed in the tapes, rods, etc. being resisted by the mass of concrete, thus opposing the tensions in these tapes by the natural resistance or compression of the surrounding mass. vWhat is accomplished, in effect, is a freezing of the outward thrust of the original peripheral member into the filler of the surface itself. At auy rate, theso-called load-weight ratio .is not substantially reduced or impaired.

. The system is thus one based upon a theory diametricallyopposed to the usual engineering practices as they are foundrepresentedin such building structures or unitsas the cantilever, the dome, arches, roof trusses, etc. can-- erally speaking, all of these usual types of supporting structures are predicated upon the principlev of compres-- sion of the individual elements thereof. As, a' prime example would be either the do'rne or arch, both of which usually comprise a series of interfitted parts,-compressed with respect to each other, with maximumconipres'sive force exerted downwardly upon whatever base is provided. In the instant case, and subject to the above qualification having reference to the use of materials such as concrete, the only compressive force in this direction is the mere Weight of the unit itself; the supporting structure, having a periphery which is under tension throughout, is selfsupporting and independent of any forces of compression around that periphery. w 7

It is here to beobserved that, in speaking of common forms of structures such as the truss, cantilever, dome, etc., it is true that in each of same there are certain forces of both tension and compression at work; however, the important thing is that these forces are not utilized to the greatest advantage. For example, in a given factory shed, a large number of trusses may be used but, at the same time, stresses developed within each individual truss are not utilized in conjunction with the forces of tension and compress-ion employed throughout the re maining structure; Y instant invention.

In known architectural devices utilized as basic frameworks in roofs, bridges and -building structures generally, reliance upon compression force's has imposed a definite limitation upon the maximum load-bearing capacity which is obtainable as compared with or in ratio to the weight of such units. As an aspect of the instant invention, it is estimated that the load-weight of unit ratio is far in excess of that heretofore obtainable. The phrase *loadweight ratio is here to be understood as being the ratio ;.between the load-bearing capacity of the system and the weight of the system itself. It is estimated in this aspect of the invention that certain units following this system will support loads of up to one hundred times the actual weight of the unit. This is due to the fact that;the' .peripheral member, restrained by tension, exerts an outward thrust which is causedby'the stress within igand which resists thebending, gravity and compression vreactions resultant from the dead load of substances comnris h m ne Sup or e by uch p ph a mainer.

Structural units as they-are generahy loyga w architectural field are designed for more or less ific uses and purposes. The instant invention p esenrs'a system and structural unit which is almost universal in .its application and subject to fabrication out of almost Such is not true of structures of the any type of ordinary building material, including metals, concrete, plastics and evenafabrics. Whatever may be the basic material that is utilized, the ultimate completed structure with its warped,zparabolic surfaces, is"one that is self-contained, stable, self-supporting and1free=of s econdaryreactionsQ 'Although'heretofore considered structurally. impossible without secondary. bracing or re-inforcing, by thepractice of my.invention, it is possible toIachieve almost limitless variations of "useful surfaces and shapes. The system completely eliminatesthe need for a,built-up formwork of any kind,.a factor that has heretofore been a principal deterrent ,to',the execution of any but the. simplest types of shell structures, particularly those of concrete form, due to cost consideration. It is,.accordingly, a primary object 'of this invention to tprovide a self-supporting and self-contained structural unit and a system or method of fabricating such unit a more specific description of the invention will be found and wherein:

that :is predicatedup'on the principle lof rnaintaining a closed. periphery under constantlstress, either tensional or compressional... 1,1; e I I:

,It is a'further'objectof the invention to provid'ea unit of. the described, type. wherein "structural strength, flexibility ofdesign and ease of. fabrication and erection all flow,.from the basic concept .thatif a continuous curved periphery is subjected to forces'that place it'yout of plane and compel the formation of contiguous para- .bolic curves inboth plan and section, the" result will be a self-contained, and self-supportingunit. of'a strength andadaptability far superior to building units and designs heretofore known. it 3 Another object of the invention is .the provision of a building structurewhich is: not only of esthetically pleasing appearance, but is also readily adaptable. tomass production, techniques by panelization procedures, and

havingparticular reference to sizeorvolume requirements, these being accomplished without any encroach- .ment onfreedom of planning. 7

It is an additional object of the invention to provide a structure wherein the outward,forces,loraforces of ex-' pansion of a deformed. continuous peripheral. member is utilized to sustain, and stabilize a warped, parabolic surface for which the peripheral member is theboundary.

A further object of the invention is the'provision of a building unit which eliminates the requirement of ad- ,ditional framework when the erection thereof involves .certain building, materials such as concrete, perlite, gyp- ;,sum,, or, similar aggregate mixes..,In this connection, the

tension members which havebeen referredto, be they wires, ,tapes, cables orjrods, canbe utilized as the reinforcing and supporting means for the positioning of panels, fabrics, paper-backing or many variant types of lathing. It follows that, these. inner component members of the membrane will be suitable for any type of plastic or synthetic sheets or-films which may be provided as decking, or for protective or insulative purposes.

Another objectiveof the invention is theprovision of a structural unit that utilizes every component element thereof in at least two ways to the exclusion of secondary bracing or external supporting members, resulting in a design that ,is self-contained, self-supporting and ex ltremely flexible in the sense that it is subject to practically limitless variations of useful architectural surfaces and shapes. Along this line'it is to be further noted that such unit provides complete freedom from obstructive vertical supports of any type whatsoever.

A final objective of the invention is to provide a structural unit that, because of its adaptability and flexibility 'to'the numerous shapes as hereinbefore referred to,-may be applied to a multitude of difierent uses on theone hand and, on the other, may be fabricated of almost [any type of material having'in mindyof course, such relative size, space requirements, purpose of use and other practical limiting factors as are applicable.

Reference will'now be made to the drawings wherein Figure 1 presents a side elevation view, partially in section, ofone embodiment of the invention;

Figure 2 is a plan view, similar to Figure 1 and also partially in section;

Figure 3 is a plan view showing another modification 'of the invention and illustrating the manner of inter-.

weaving the tension members in a four-pointed, approximately square configuration, this view depicting the open lattice-work of the tension members as ,beingfilled with a suitable building material;

Figure 4 is a plan view, similar to'FigureS, but showing the roof broken away and the application of this embodiment of the, invention to practical use-that of an on view taken on the line 6-6 of 'bodiment of the invention adapted, architecturally, for such e'sthetic building structures .as cathedral towers;

Figure 10 .is an elevation view. of a further embodiment of the invention havingg five so-called high points with complementaryparabolic ornear parabolic arches and illustrating theuse of the'inve ntion for a structure of considerable-size; v

- Figure; 11 is a detailed section view of one manner of interconnecting synthetic or plastic tensionmembers to a peripheral member of like material;

Figure 12 is a section view illustrating in detail a manner and means of interconnecting metallic tension members'to aperipheral member of like material;

Figure 13, similar to Figuresll and 12, shows, in section, a tensionmeans which is imbedded in concrete and terminates in a periphery of like material;

Figure 14 is an enlarged detail-and perspective view of a means for rapidly interconnecting a given type of tensionmember to the peripheralframework; and

Figure 15 is a detailed view, in section, showing one form of base support. forinterconnection with the so- .called low points of agiven, structural unit and with consequent overall support of the entire unit.

Having now more particular reference to Figures 1 and 2 of these drawings, it is seen that the form of the inven 'tion here shown is one 'whichin plan is approximately triangular in configurationj Reference. is .here made to the outline of Figure, 2- bordered continuously about its periphery by theperipheral member 10. As seen in sectionin Figure 1, it is to be appreciated that the 'con-,

tiguous curves here shown are each parabolic in form,

-the low points representing the ground contact points and the high points representing the peak of what would be, in the usualcase, a roof structure.

The materials or fabrication involved in the representation in Figure 10 are intended to be commensurate with a structural size of perhaps 50. laterally from high point to high point. In a stiilcture of 'this'sizegthe peripheral member wouldpreferably be of a metal such-as steel or steel tubing of relatively high tensile strength and having a naturallinherent, flexibility or springiness at least sufficently so to exert a constant outward thrust after being placed under" tension by the crossed or interwoven frame work. ,In fabrication of a structure of this type,the contour, before placing the unit under tension and stress, would be somewhat diiferent from that shown in Figure if the amount ofcurvature necessary is predetermined tobejn excess-of the elastic limits. of the materialused. That;is;,in ,planfandviewing the peripheral configurationfrom above, the metahin such a case, isprefrably prebe'nt or preshaped so that the periphery at the socalled low points would extend outward to a greaterdegre'e as shown in Figure :2, or at least to, that degree which would place the periphery under sufficient stress after the tensioningthereof. At any rate, such periphery, placed under stress, provides support for the membrane (of whatever material), the latter effectively locating all points thereof upon or near corresponding points of an imaginary warped plane which yieldsthe minimum possible area within such deflected peripheral member.

As shown in certain of these figures, it is contemplated that the formwork consisting of the many intersecting tension braces or tapes together with the peripheral memher, would be suitably filled with concrete, or like material, in a manner to be further referred to hereinafter, resulting in a structure that is actually steel reinforced.

Prior to this, however, the procedure followed in erecting such a unit would be of this order: the -formwork 19 is initially preshaped to the desired extent, if this be necessary, and subjected to the tensional stress placed upon it by three initial tapes or tension members, namely members 12, 14 and 16. Each of these run from high point to low point of the structure, respectively, and intersect at the center, here indicated at X. They may be subsequently joined together by any suitable media at this point.

By placing a predetermined amount of tension upon these three crossing elements, it is seen that the ultimate high points of the structure are each lifted in this manner, and, having reference to the opposed portion of the approximate triangle or that portion directly opposite each high point, the low points thereof are bowed. These three tension members, 12, 14 and 16, divide the shape of Figure 2 into three diiferent sectors, this feature being mentioned in order to clarify the manner in which the tapes or tension members in each sector overlie or underlie each other, respectively. These three sectors would be as follows: that divided by tape 16, point X, tape 14 and periphery 10 extending between the peripheral points 19 and 20; that circumscribed by tape 16, point X, tape 12 and the periphery 10 extending between the peripheral points 18 and 19; and that bounded by tape 12, point X, tape 14 and the periphery 19 extending between the peripheral points 18 and 2d. The three described sectors, for purposes of illustration, are generally indicated at A, B and C, respectively. Each of the initial three tapes or tension members 12, 14 and 16 are maintained in position at the periphery by some appropriate form of se curing means, here but diagrammatically indicated at the three points 18, 19 and 20.

The tapes or tension elements within each of the three sectors, A, B and C, do follow a definite pattern, as will be demonstrated, in order that their function of placing the peripheral member in tension and the further necessary function of asserting compressive forces against each other to attain the desired parabola in section, is achieved. Accordingly, having reference to sector or area A, the diagonal tapes 21 appear to be parallel to the initial high to low point tension member 14. Actually, and as seen in Figure l, the relationship, because of the bowed effect, is asymptotic. In any event, such diagonal tapes lie, in this sector, on top with the other crossing tapes underneath. However, when these tapes 21 meet the boundary line of an adjacent sector, or sector B, it is seen th'attney then go underneath tape 16 and are placed underneath or, optionally, in between the other intermediate tapes found in that sector. Similarly, and having reference to area B of this triangular configuration, it is seen that the intermediate tapes, here shown as 23, all having an approximately asymptotic relationship to each other and to the initial high to low point tape or tension member 12. These also lie on top of the remaining'tapes in this sector until these tension members 23 "reach the dividing line of the sector represented by tension member 16. They then underlie the respective tapes found in sector A.

proximate 8.

' and 2). the initial Following through with this procedure, the third series of diagonal tapes, with the same relationship to each other and to the initial high to low pointtension member 16" and having particular reference to sector A, may be positioned largely on top of or surmounting the remaining tapes in that third sector until meeting the boundary,

linesdefined by the respective tension members 12 and 14. At this point, these can underlie or be intermediate the other two series of tapes as represented by those shown at 21 and 23 at the crossing points found in sectors A and B.

The result of this rather interwoven assembly of tension members is to permit the high points to rise in the manner graphically illustrated in Figure 1 but, because of the intersecting compressive force of the intermediate tapes, to how these high points, as shown in this figure,

to a configuration that is either parabolic or near para belie in both section as well as in plan.

Illustrated in these two figures '(Figures 1 and 2) is a covering for the tapes, as generally indicated at 35. This may be of such material as concrete and poured into a skin or covering which is affixed to the underneath side of the entire assembly, connected to the peripheral member at its outer edges and following the contour of the lacework represented by the relatively large number of crossing tension members. When set,-this concrete form will be the full counterpart of the tension system herein preserved throughout the section or, in the alternative,

an approximate series of parabolas are formed, the latter perhaps also approaching concoidal, curved formations. These figuresfurther illustrate with great clarity the simplicity of ground anchoring of structures of this type, with only three ground loci necessaryto rigidly maintain the unit in place upon an appropriate flooring 3:8.

The use of the parabolic form (having reference to the curvature assumed by the periphery or the curves found in sectionfrom any direction) permitsthe form to reach a height above ground level that is appreciable and fully adequate for any normal clearances. If it be assumed, as suggested above, that the largest diameter of the structure, in plan, is then the average height of the outermost peripheries illustrated in Figures 7 and 8 willap- Of course, as .will be seen, "the. type of parabolic form employed is determinative of the height of these elevated points. Since geometrically a parabola may be defined as the intersection of a cone with a plane parallel to its side, the height of the structures herein contemplated is easily varied, within the knowledge of those skilled in the art, by calculations derived from the alternate use of the primary structure, the conethe more narrow or pointed the cone, the more extended and narrower the resulting parabolas, with consequent elevation,

of the high points of the tensional system which is herein described.

The basic principle of the invention can be varied to.

find application to innumerable forms, all tensioned, however, in approximately the same manner. Generally speaking, the triangular formation of Figures land 2, by its very nature, necessitates for proper performance at east three sets of tension members. once to Figure 3, it is seen that a square, or four-pointed configuration in plan, is shown.

In the construction of thefunit of Figure 3, therebefing an even number of high points and an even mmb'eror low points (in contrast to the modification of 1 However, by referquadrangle, roughly stressing by way of tension accornrants which run at right angles thereto.

The result is to pull the four cornersof the structure 7 plished by buttwo sets of tension members, the individual elements of each set being right-angularly disposed with respect to each other; In" this instance, also, having referenceto the initial stress placed upon the peripheral member, the resilience or spring-back quality of the peripheral member can be prejudged by those skilled'in the art and such may be prebent to that degree sufiicient to exert the desired degree of outward thrust after the complete formwork has been placed under tension. 7 Here, the initial stresses are obtained by the two longest of the several tension elements, namely elements 49 and 48 which, respectively, run from high point to high point of the peripheral member, here shown at 40, and which intersect at the center of the unit or at the point generally indicated at O. t e

a As with respect to the modification of'Figures 1 and 2, and having reference to the interlacing or positioning of the series of tension elements, it is seen that in-this case the total area in plan may be divided into quadrants represented by the four areas generally indicated atlD, E, F and G. For purposes of explanation, Figure 3 has been bisected bytwo dividing lines 5-5 and RR. The quadrant D is thus found to define an area bounded by RR, point, 0, 55 and with, of course, an outer boundary or peripheral member 40 which extends between the peripheral points 42 and 44. Likewise, quadrant E is an area within the peripheral member defined by 5-5, point 0, RR, and the outer boundary which extends between the peripheral points 44 and 45. The quadrant F lies within the area defined by the line RR, point 0, the line 55, with an outer boundary between the peripheral points 45 and 46. The quadrant G, as will be seen referring to Figure 3, lieswithin the lines 5-5, point 0, the line R'R, and the peripheral points 46 and 42. Thequadrants F and G are, respectively, within RR, point 0 and 55, on the one hand, and 55, point 0 and RR, on the other.

' All of'the intermediate tension members (although in the plan view appearing parallel to either the central ten sion tape 48 or its counterpart 49) are actually in approximately asymptotic relationship to each other. Within a given and particular quadrant, such tensional members running across points of elevation to a central point 0 are on top of the crossing tapes. For example, and having reference to quadrant D of Figure 3, it is seen that the tension member of whatever type and here designated at 50 (as here viewed) approximately runs parallel to the tension member 49 and between the two low points on each side of the quadrant, both located at the supporting positions 42 and 44. In normal practice,

the tension members between these two low points, or from ground point to ground point,,would first be added with the other overlying tension tapes, Within a given quadrant, being added simultaneously or in sequence. Again, having reference to quadrant D, it is seen that the tapes adajcent to tension member. 50 and progressing towards the center 0 of this quadrant, all lie on the vide contiguous curves approaching the parabolic in form and in shape.

As a practical exe'mplification of the structure of Fig.

' structure can be enclosed by side walls following the curved contour of the roof, fitted with door 61 and other compartments, as generally indicated at 65, to meet the requirements" of any given housing problem of this type; The shape is peculiarly adaptable to airplane storage as indicated bythe graphic illustrations of planes, one of which is located in each of the four corners of this quadrant structure. a p a This embodiment of the invention is further represented in Figures 5 and6 which, are section views taken onzthe section linesof Figure 3. The practicality of thisvaria'tion of the invention is at once apparent from. a consideration Qf*:SlJCh sectionswhere it is seen that despite the relative simplicity of fabrication and erection of a unit of considerable size, there is ample height and surface coverage to accomplish the purposes of this type of building structure. In addition, the all-important factor is still present that with the quadrangular type of unit, only four anchoring points are necessary; extraneous of these, the shelter or housing construction is entirely self-sufiicient, eliminating the need of any further buttressing elements or other supporting members.

Further illustrative of' the wide variety of structural shapes and configurations that canbe obtained with the system comprising this invention are the graphic repre: sentations found in Figures 9 and 10 hereof, definitive of the extremes which maybe reached in practicing this architectural system.. In Figure 9, the continuous parabolic configuration. is geometrically and theoretically based upon a cone of acute angularity with respect to t the apex; in Figure 10, the opposite is true-the parabolas and concoidal curves. there represented (are based upon the geometric planes cutting through the surfaces of cones having .sides' of relatively obtuse angularity with respect to the apex. In each instance, the ground securing medium, here represented at and 75, respectively, is attached to the so-called low point of such curved structure. In the representationof Figure 9 is found a more decorative architectural unit, applicable particularly to cathedral construction. The structure of Figure 10, although flatter? in overall dimension, is

somewhat similar to the embodiment of the invention top of the tapesrunning normal thereto. However, as

they meet the dividing line 5--5 or the dividing line R-R of this quadrant, these tapes then progress underneath the adjacent tapes which are normal thereto.

This system is followed throughout quadrants E, F and G, 'where a similar statement is applicable with respect to tension members 52, 54 and 56, respectively.

Thus it is seen that within eachquadrant the tapes or tension members exerting compression forces on the crossing tapes are overlying to that point delineating the particular involved quadrant; beyond that boundary they progress underneath adjacent tapes of the adjacent quadrepresented in Figures 3 and 4 to equal points of maximum height; the further result of this method of interlacingthe tapes in this assembly is to bow these elevated points, by the crossing tension members, to profound in Figures 3 and 4 but here representing a fivepointed construction or one having five high points and the same number of "corresponding low points.

It is to be understood that, the systems of the types herein referred to may be developed which are asymmetrical in formation, e.g., one elevation of the structure may be higher than the rest in the series, or with respect to a view in plan, one raised point may occupy a greater area, or be projected further, than the others of the series. In any event, the same system, described above, of creating the required curve in section and in plan would" be followed.

As stated, not only does the system of the instant invention lend itself to variation in size and application of uses but, most significantly, it is of the type that permits utilization .of practically any material for its construction. In Figures 11 to 15, inclusive, are illustrated cer tain details of construction, particularlyfwith reference to the manner of .affixation of the tension members to the peripheral element where the involved problem of i use of different construction material is disclosed.

' For example, in Figure 11, it is contemplated that an entire unit could be fabricated of plastic or equivalent synthetic materials. Here, the hollow tube is representativeof a plastic peripheral member which, either by being inflated or filled or because of its inherent structural strength, exhibits the property of resilience or neeessary outward thrust after the application of "tension thereto; Tension is applied by constructing the member 88- with interior flange's- 8'1 and 82- which may be either continuous along the inner side of the member 80 or spaced to appropriately receive'the spaced tension members. At any rate, the space between these two extensions or flanges 81 and 32 is adapted to receive the end of a tension membrane 8 5-, here shown as also being of plastic. Such synthetics are easilybonded together and, in actual construction of this type of unit, after the member 8% has been brought into its desired flexed position, the tension means 85 is placed in between the flanges 81 and 82- and bonded thereto in awell-kno'wn manner. A plastic Web or membrane of desired curvature is thus obtained. Similarly, the plastic sheeting 85 can be replaced by fabric, which will function in the same manner.

This plastic form of interconnection has high utility in another respect: if the inner rings 81 and 82 are continuous, then by application of an additional plastic sheet, indicated at 87 in dotted line, a double-walled membrane is formed. Obviously such a double Wall provides a dead air space, effective as insulation and effective also as a sound-proofing construction.

Figure 12 is representative of a unit fabricated of high quality metal such as structural steel where the periphery or flexed member 90 may be tubular in formation. If desired, and after stressing of the entire unit in the manner described, this peripheral member can be corniced in any usual manner as by means of the angular enclosure 92, shown in this figure. Steel tapes 94, running from high point to high point, as described, are aflixed to the peripheral steel tubing 95) by butt welding, asat 3. These tapes are, of course, crossed by and interwoven with, in the described manner, tapes as.

In this form of the invention it is contemplated that plastic sheets could be used to form the entire web or membrane, when appropriately affixed to the tension members. Accordingly, as indicated in Figure 12, such tension members can be bonded as by a cement 98 to synthetic sheets 104, 105 located on each side of the elements 94 and 95. Furthermore, and interspersed throughout the web, a usual type of clip 100 may be employed to additionally secure adjacent sheets of this material together. The resulting plastic membrane. is then surmounted by any form of suitable sheeting or covering 102, to prevent deterioration of the membrane structure. It is to be here observed that a continuous film of plastic or fabric will achieve the same effect as a series of tension members. Such constitutes, in effect, an infinite number of tension elements, and will function in the same way so long as the film follows the same planes developed by the system of tapes herein described.

At any rate, upon completion of the stressing operation to place the entire structure under tension, and with respect to the interlaced tension members, the upper surface may be covered with any additional suitable material 102. This latter can be in the form of a sheathing, employed for the obvious protective purpose of shielding the underneath tape and plastic structure from the elements.

As another alternative type of construction and one deemed to be most practical in the fabrication of particularly large units, the concrete example of Figure 13 is referred to. Here, the original, supporting peripheral member is but generally and diagrammatically indicated in dotted line at 119. Initial stress is placed upon the periphery in a manner heretofore explained. However, since the structure in its final form is one essentially of reinforced concrete, the tapes or tension members 121 are firmly held in position at their ends by the use of an inverted wedge-shaped lug 120. p I I The metallic lug 120 is thus, after setting, imbedded in concrete as are the; rest of the interlaced tension elements. The shape of suchmetal lugs 120 (that of a 10* wedge) is inverted as shown 'infthisfigure, so that" after the unit has been set in concrete, each wedge-shaped lag (in cross section) resists the forces: of tension placed upon it by the corresponding tension members.-

After prestre'ssihg these tension members 121 to the desired extent, or to that extent to force the unit into its desired parabolic'shape, as discussed above, cross tension elements 122 are fixed in the position indicated; It may then-be desirable to create a form to receive the poured concrete mix and, to this end, a latticework or expanded type of metal 126. is positioned against the tension members 121' and 122 and afiixed thereto in any desirable manner. This last-named metallic lathing 126; or similar type of means, provides support for a number of retaining members 127, such being adapted to hold afi underlying covering, 128 of paper, cardboard, plywood;

etc;, or any material that acts as a closure for the under.-

neath side of the cor'npleted unit. The co'ncret'ei 129 may? then be poured into 'theframe and built-up to the extent indicated to provide relatively smooth, curved surfaces on each side of the structure; it is apparent that the entire unit becomes one of rein forced concrete, the tension members extending from high to low'p'oints and, as well, those interlaced with the former, contacting the metallic reinforcing elements.

The peripheral member, diagrammatically indicated 'at- 119, to which the tension members 121 are initially at= tached for the exertion of stress upon the periphery of the unit, may ultimately be detached and disposed of as sal vage or otherwise, when the concrete has set. Since the a wedge-shaped lugs are then firmly filled in the concrete periphery and the entire structure is rigid and, in effect, reinforced concrete, theperipheral member '119 is no longer needed to. preserve the structural strength of the unit. I a

Means have been provided for simplifying the manner of interconnection of such tension members, as metal tapes, to the continuous peripheral element, as it has been identified above. In Figure'l4, this latter element, here shown at 130, may consist of a steel tubular element, prebent to a predetermined extent so that it will, as stated aforesaid, exert only the desired amount of outs ward thrust or resilience. T he several referred to tapes can be easily attached by the mechanism depicted in this figure. Here, two elements 132 and 134, semi-circular in configuration and having an interior concave shape complementary to' the shape of the peripheral membei, are hinged together by means of a hinge 138, fitted with the" usual hinge pin 139. Each of these members 132,

134 terminate, opposite the hinge point, in extensions 135 which, when disposed in the position shown in this figure, are parallel or approximately parallel to each 'pins 146, the latter pivotally interconnecting these twd bars together. At the end near the tubular element 130, each of the bars is provided with a relatively sharp right angular projection 150, the latter being adapted, under adequate pressure, to tightly engage with or bite into the metal of the flanges 135. It is obvious that suitable depressions may be created in these flanges for the re-f ception of such projections .150 to further assure per: manent fixation of the same.

The opposite end of these parallel, hinged bars 141, and with respect to the inne or facing edges or same, is angled as at 152, these edges thus approaching each other with the same angular deflection. A tape holding wedge 155, having the sides thereof angled complementary to the angle formed between the adjacent Upon setting of the mix,

11" angled'edges of bars 140, 141, when approximately parallel to. each other, terminates" interiorly in an exten-. sion 156, 'the latter, as shown,'having parallel sides. Reference to Figure 14 should make clear the construction of the inner sides of these bars 140, 141, and the complementary shape of the wedge 155. In operation of this system, the tape 160 can be placed completely around the wedge 155, as shown. With the exertion of tension upon the tape 160, the. same is drawn tightly, by the wedge, against the inner sides of these parallel bars. By reason of the hinged relationship of the latter, the opposite ends of these bars, due to the wedge action, are brought together. Hence, the greater the amount of of a dome structure. The main difference from the dome type configuration is t hat the perimeter of the dome and achieving alignment by the continuous, unbroken,

successive curvatures of the perimeter.

As inferred above and again having reference to the wide variety of applications of the principles here set forth, the use of plastic in the execution of the system tension applied, the greater the bite upon the flanges.

135 and the more tightly the tape is held within the connecting assembly represented by these two parallel bars 140, 141. It isthus seen that this interconnection is of the utmost simplicity and oncein place. the amount of tension can becarefully regulated by pulling through the'tape end 161 to the desired extent. Such type of interconnectionis, of course, applicable to almost any variant of this invention and equally appropriate for use with plastic peripheral members and plastic tapes or tension members'when utilization of the same is indicated.

Reference has been made to the fact that the number of ground supports necessary are few in number: actually,.ground contact points are of a number equalling the number of the so-called low points of the system. It follows that the number of ground contact points are the same as the number of high points'of the system. At any rate, one means of ground interconnection with the all-importantmembrane supporting peripheral member, is'found in Figure 15. Here, such peripheral member'isindicated. at .170. It is encased in what might be termed a bearing block, i.e., a two-part element consisting of a top semi-circular cover 172 and a'base member 174 of complementary shape, both being provided with interior, concave surfaces to approximately match the external circumference, of the peripheral member 170.

This so-called bearing member is aflixed in a concrete block 180 by means of two or more bolts 175 that terminate in lateral flanges 176. The latter will assure retention'of the bolts 175 and, hence,the accompanying clamping structure in the block 180 after setting of the mix. This structure in one sense is actually a bearing member because, if desired, the tolerances can be such.

that the holding or retention power is maximum while presents the .art with an inexpensive, light-weight, yet

extremely durable form of structural unit. Such, in fact, can be realized by employing either a plastic or textile film for the membrane. These would constitute units the peripheral member is permitted, to twist and even move longitudinally somewhat to accommodate possible changes in the length or size of the tubular element due, for in'stance,,to temperature fluctuations 'and're'sultant contraction or expansion of the metal.

In summary of the description of the invention, as

rendered above; it is the'essence of this concept that the structural components of the system described will develop warpedsurfaces that are self-contained, stable, selfsupporting and free of secondary reactions. Asindicated,"use' of this system permits achievement of limitless variations of useful surfaces. and shapes hitherto deemed structurally impossible without some form of secondary bracing or reinforcement. The system of this invention I completely eliminates the need fora built-up formwork of any kind, it being generally recognized that such constitutesfthe prineip'al'determent, to the execution of any but the simplest types ,of shell structures inconcrete due to cost consideration."-

of low weight whenused together with a peripheral member'of relatively thin-walled plastic tubing. When suitably patterned prior'to the stressing thereof, the membrane will assume a predetermined warped shape when the peripheral member, is filled with compressed air or with plastic materials under pressurewhich may or may not harden once injected. Conductive to manufacture in rather small sizes, such plastic units can be provided with side curtains following the periphery of the high points, thus providing light weight shelters, useful as tents, which can be very compactly packaged and erected in a minimum of time. For such shelters requiring rather higher degrees of insulation, the area within the peripheral member may be covered by a second membrane 86 (as referred to in the explanation with :,reference toFigure i 11), thus providing a dead air space (or space to receive insulation) between the inner and outer-skin thereof...

As a basic premise for this. entire system, it is thus to be noted that the invention provides a structural unit wherein an exceptionally high degree of use is made out of every one of the several components that enter into it. This sharply distinguishes this system and the structural units derived from it from architectural projects heretofore known where exterior supporting or reinforcing elements are necessary in order to obtain the required load-bearing capacities.

It is obviousthat this invention may be varied in many ways and other expedients employed to accomplish the purposesthereof; however, it is to be understood that the scope of this invention is to be limited only by the scope of the appendedclaimsh a I claim: V

1. In a structural unit, a closed and curved, continuous, peripheral element of resilient material, said element exerting constant outward thrust,.said element being prebent to prevent fracture due to application of stress beyond the elastic limit thereof, means to place said periphery undertensional stress, said means comprising tension members interconnecting one side of said periphery to an opposite side thereof, a second series of tension members positioned angularly to said first tension means and also connecting opposed portions of said peripheral element, said peripheral element being under suspended tension by said series of tension means said element having successive high and low points and having a shape approximating contiguous parabolic curves both in sec:

Having'particularreference to-the execution of the system in concrete wherein a, network of rods, cables, etc. is employed, it will 'furtherbe clear that the peripheral member may be detached; salvagedor disposed of if the ends of the rods or cables are provided with lugs which become imbedded inthe concrete (e.g.. s'eeFigure 13). .The remaining concrete shell will thc'n'represent an achievement in negatively curved architectural surfaces, somewhat akin to the positively curved surfaces tion and in plan. r

2. In a' structural'unit, a closed, curved, continuous, peripheral element of material of inherent elasticity, said element being present to exert constant outward thrust, said element being prebent in the direction of interiorly directed tensional forces toprevent fracture upon the application of tensional stress beyond the elastic limit thereof, means tojplace said periphery under tensional stress, said means comprising tension members interconnecting one side of said periphery to; an opposite side thereof, a second series of tension members positioned angularly tosaid first tension meansand also connect ing thrust outwardly when placed under tensional stress directed towards the center thereof, said element being prebent in the direction of interiorly directed tensional forces to prevent fracture upon the application of tensional stress beyond the elastic limit of the element, said element defining in plan an area approximately triangular in configuration, means to place said element under tensional stress, said means comprising three tension tapes extending from each corner of said triangular configuration to the opposed side thereof, said tapes comprising three sectors of equal dimension, additional tension members parallel to each of said tension tapes, the tension tapes and members on top in each sector running underneath angularly inclined tension members and tapes in any 0t er of said sectors, said tension tapes and tension means placing said peripheral element under tension said element having successive high corner and low intermediate points, said element and the area defined thereby comprising contiguous and approximately parabolic curves throughout both in plan and in section.

4. In a structural unit, a closed, continuous, peripheral element of inherent elasticity, said element being prebent to prevent fracture upon the application of tensional stress beyond the elastic limit thereof, said element being prestressed to exert constant, outward thrust, said element defining an approximately square configuration in plan, means to place said element under tensional stress,

said means comprising tension tapes extending from corner to corner of said square configuration, said tapes defining four sectors of equal dimension, additional tension members in each of said corners disposed normal to the plane of said tension tapes, the tension tapes and tension members lying on top in any sector being disposed underneath the tension tapes and tension members of any adjacent sector, said tension tapes and members placing said peripheral element under tensional stress, said element having adjacent high and low points respectively, said element comprising, in both plan and section, a structure having a series of contiguous parabolic curves.

5. In a structural system, the method of fabrication of a unit which is under stress throughout the periphery and the area circumscribed thereby, comprising forming an endless curved periphery having inherent elasticity causing it to exert outward thrust throughout when placed under stress, submitting said member to tensional stress by interconnecting opposite sides of said periphery and drawing said opposite sides together by interior tension members, thereby creating interiorly directed forces to form successive low and high points in said periphery, said circumscribed area forming a plurality of sectors equal in number to the number of said low and high points, interconnecting said tension members so that said tension members in any one of said sectors which overlie the others of said tension members, underlie the others of said tension members in any other of said sectors, said forces creating a series of contiguous, approximately parabolic curves in section and in plan throughout said periphery and throughout the area defined thereby.

6. In a structural unit, a closed peripheral element, said element being prestressed to exert an outwardly directed, constant thrust, means to place said element under tensional stress to form contiguous, approximately parabolic curves in both plan and section, said means comprising a membrane within said element exerting interiorly directed forces thereupon, said peripheral element having at least two low points and a corresponding number'of high points are formed in said peripheral element.

7. in a structural unit, a closed peripheral element, said element being prestressed to exert an outwardly directed, constant thrust, means to place said element under tensional stress, said means having contiguous parabolic curves in both plan and section, said means comprising a membrane within said element exerting interiorly directed forces thereupon, said element and said membrane forming a compoundly curved shell structure, said peripheral element having at least two contiguous low and high points.

8. In a structural unit, a continuous, spring-loaded peripheral element of resilient material, said element exerting outward thrust throughout, means to place said element under stress in a direction opposite the direction of said thrust, said means comprising a membrane interconnecting opposed sides of said peripheral element, said membrane placing said peripheralelement under restrictive tension, said element having successive high and low points, said element having curves of approximately parabolic configuration in both longitudinal and lateral section.

9. In a structural unit, a spring-loaded peripheral element of resilient material defining a closed area, said element being adapted to exert thrust outwardly in a direction away from the center of said area, means to place said element under stress, said means comprising a membrane interconnecting opposed sides of said periphery, said membrane extending throughout said area and placing said peripheral element under restraint, said peripheral element having successive high and low points, said membrane comprising an anticlastic formation having approximately parabolic curvatures in one direction and having additional approximately parabolic curvatures in a direction approximately normal to said one direction.

10. In a structural unit, a spring-loaded peripheral element of resilient material defining a'closed area, said element being adapted to exert thrust outwardly in a direction away from the center of said area, means to place said element under stress, said means comprising a membrane interconnecting opposed sides of said peripheral element, said membrane consisting of at least two series of tapes interconnecting opposed points on said element, one of said series of said tapes being positioned in a direction approximately normal to another of said series, said membrane extending throughout said area and placing said peripheral element under restraint, said element having successive high and low points, said membrane having an anticlastic shape consisting of approximately parabolic curvatures in one direction and consisting of additional approximately parabolic curvatures in a direction approximately normal to said one direction.

References Qited in the file of this patent UNITED STATES PATENTS 2,545,556 Pont Mar. 20, 1951 FOREIGN PATENTS 1,120,195 France Apr. 16, 1956 OTHER REFERENCES Engineering News Record, December 1954, page 36.

Journal of the American Concrete Institute, January 1955, pp. 397-415.

Progressive Architecture, March 1955, pp. 130-131.

House and Home, August 1955, pp. -96.

Progressive Architecture, September 1955, pp. 82-83.

Civil Engineering, May 1956, pp. 64-65.

House and Home, September 1956, pp. 134-135.

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