US 3906571 A
A structural member entirely formed of sheet material suitably connected together along surface portions thereof. The sheet material is folded or otherwise formed into individual geometric shapes bonded to one another along overlying surfaces thereof.
Description (OCR text may contain errors)
United States Patent 1191 Zetlin Sept. 23, I975 [5 STRUCTURAL MEMBER OF SHEET 3,086,899 4/1963 Smith ct a1 .1 161/127 MATERIAL 3523333 211322 2 1 /32;
rlpe Inventor: Lev Zetlm, 89 Hamllton 3,391,511 7/1968 Harris ct 211.1... 161/69 x Roslyn, N.Y. 11576 3,415,027 12/1968 Snyder et 211.... 52/263  Filed May 30 1974 3,849,237 11/1974 Zetlin 14/73 X  Appl. No.: 474,527
Primary Exammer-N1le C. Byers, Jr. Related Appllcatlon D313 Attorney, Agent, or Firm-Henry Sternberg, Esq.  Division of Ser. No. 132,390, April 8, 1971, Pat. No.
52 us. c1. 1. 14/17; 14/6; 52/263  ABSTRACT Z gz' i' 2 A structural member entirely formed of sheet material 52/87 648 '6' suitably connected together along surface portions 136 1 6 thereof. The sheet material is folded or otherwise formed into individual geometric shapes bonded to  References Cited one another along overlying surfaces thereof.
UNITED STATES PATENTS 6 Claims 16 Drawing Figures 1,875,188 8/1932 Williams 161/127 US mm Sept. 23,1975
Sheet3of 6 3,9,571
US Pamm Sept. 23,1975 Shest 6 0m STRUCTURAL MEMBER OF SHEET MATERIAL CROSS-REFERENCES TO RELATED APPLICATIONS This application is a division of copending US. Patent Application Ser. No. 132,390 filed Apr. 8, 1971 entitled Structural Member of Sheet Material" by Lev Zetlin and not US. Pat. No. 3,849,237. The present invention relates to structural members, particularly a structural member which may be fabricated almost entirely of sheet material and which is capable of supporting loads and resisting stresses.
On object of the present invention is to provide a structure comprised of one or more interconnected structural members of the above type which is able to support loads while spanning the relatively large distances required to be spanned by a bridge.
A further object of the present invention is to provide a structural member of the type described above which may be formed almost entirely of paper or similar sheet material.
A still further object of the present invention is to provide a structural member of the above type which has a geometric configuration suitable for imparting rigidity and strength to the structures in which it is used.
Another object of the present invention is to provide a structural member having the above characteristics and which also displays a high strength to weight ratio.
A still further object of the present invention is to provide a structural member such as described above which displays the combined structural characteristics of a skeleton frame system and those of a stressed-skin system.
Another object of the present invention is to provide a structural member which, while possessing the above characteristics, may be fabricated out of materials such as sheet metal, sheet plastics, fiberous sheet materials, as for'example, paper, or even a sheet material comprised of a thin layer of concrete sprayed or otherwise suitably formed on steel reinforcing mesh.
Another object of the present invention is to provide a structural member, having the above characteristics, which is of modular construction and whose modular elements may be mass produced, easily transported to, and readily assembled at, the site.
Still another object of the present invention is to provide a lightweight, easily transportable, relatively inexpensive structural member of the above type which is comprised substantially entirely of mass-produceable modular elements of sheet material. i
A concomitant object of the present invention is to provide a structural member having the characteristics described above and which may be readily assembled with similar members to form a load carrying structure such as a bridge. i
In accordance with the present invention, a system of longitudinal webs of sheet material and hollow shell elements of sheet material are interconnected along overlying surfaces thereof for forming a composite integral structure which displays the combined characteristics of a truss and a stressed skin system.
More specifically, according to the preferred embodiment of the invention there is provided a longitudinal web of sheet material folded, along a longitudinal center-line thereof, into a V-shape. Modular shell elements, also of sheet material and having the shape of hollow pyramids, are longitudinally distributed along and nested in the longitudinal web and bonded thereto along corresponding overlying surfaces of the web and the shell elements. There results a composite structure displaying the characteristics of a series of interconnected triangular truss units providing the rigidity and stability incident to such structural triangulation.
The foregoing objects and advantages of the invention will become apparent from the following description of a preferred form and certain alternate forms thereof and from the following illustrations of those forms, in which:
FIG. I is a perspective, partially cut-away, view of a bridge constructed in accordance with the preferred form of the present invention;
FIG. 2 is a perspective view of the bridge of FIG. 1, showing the internal construction at the underside thereof;
FIG. 3 is a transverse sectional view of the bridge taken along the line 33 of FIG. 1, in the direction of the arrows;
FIG. 4 is an enlarged fragmentary longitudinal sectional view taken along line 4-4 of FIG. 3, in the direction of the arrows;
FIG. 5 is an enlarged fragmentary longitudinal sectional view of the bridge taken along line 55 of FIG. 3, in the direction of the arrows;
FIG. 6 is anenlarged, perspective, partly sectional. partly schematic view of groups of pyramidal elements arranged, in accordance with the preferred embodiment of the present invention, in the oppositely directed channels formed by a plurality of longitudinal webs;
FIG. 7 is a schematic representation of the interfitting layers of sheet material for forming the longitudinal web according to the preferred embodiment of the invention; I
FIG. 8 is an enlarged perspective view of a single pyramidal unit according to thepresent invention;
FIG. 9 is an enlarged perspective, exploded, view of a pair of sheet sections each folded into half-pyramid shape and together forming an end closure for the opposite longitudinal ends of each upright pyramid series;
FIG. 10 is an enlarged perspective view of an end closure member for the opposite longitudinal ends of each series of inverted pyramids;
FIG. 11 is an enlarged perspective view of a transverse web element in accordance with the preferred embodiment of the present invention;
FIG. 12 is a perspective view of a pyramid-closure member for closing the open ends of the pyramidal members, according to one embodiment of the invention;
FIG. 13 is a perspective, exploded, view of a portion of the structure of FIGS. 1 and 2, showing the relationship between the longitudinal web, the upright and inverted pyramids, and the end-closure members according to one embodiment of the present invention;
FIG. 14 is a perspective view of the structure shown in FIG. 13, showing, in addition thereto, in exploded form, the upright and inverted transverse webs, the pyramid-closure members, and the decking, according to one embodiment of the present invention;
FIG. 15 is an enlarged, fragmentary, longitudinal sectional, view of a bridge built in accordance with the present invention, showing the internal construction of the preferred form thereof; and
FIG. 16 is an enlarged, fragmentary, transverse sectional view of the structure illustrated in FIG. 15.
According to the preferred construction a plurality of V-shaped members interconnected side-by-side, in rank formation, for a flat structure for use as a flooring, bridge, platform, or pontoon, or the like. A flat decking covering the top of the array of the structural members, and secured thereto, serves as means for making the overall composite structure even more rigid and, in the case of a bridge, serves as a flat road-bed.
In its basic form, the present invention includes a substantially V-shaped elongated longitudinal web member having at the interior thereof a core consisting of a chain of hollow, preferably pyramidally-shaped, shell members. A plurality of such V-shaped longitudinal web members may be arranged compactly side-byside to form a unitary structure such as a flooring, bridge, platform, roof or pontoon.
The pyramidal elements may be nested in the V- shaped longitudinal member with the relatively large surface areas of a pair of opposed walls of each of the pyramidal elements in superposed relation with corresponding surface areas of the V-shaped member and said superposed surface portions bonded to one an other substantially over the entire region of contact thereof. It will be noted that not only do pyramidal elements display relatively large surface areas for their volume, but according to the preferred form of the invention, the entire surface area of the four triangular faces of each pyramidal element is in a superposed relation with and bonded to, other elements of the structure. Thus, a first pair of opposite ones of the triangular faces of each pyramidal element overlie and are bonded over substantially the entire surface thereof to corresponding surface portions of the longitudinal web means while the other pair of opposed triangular faces of each pyramidal element are in overlying relation to and bonded over substantially the entire surface area thereof to one of a pair of triangular faces of a pair of transverse web'means respectively. As will be seen, pyramidally-shaped closure elements also have substantially their entire surface area in superposed relation with and bonded to corresponding portions of the pyramidal elements, on the one hand, and a deck membc'r, on the other hand.
Referring now to the drawings, and initially to FIG. I, there is shown a bridge B comprising a longitudinal web means 10, a plurality of pyramidal elements 20 and a decking 70. It will be seen that the bridge B extends between a suitable pair of spaced supports S, and 5:.
According to the present invention the entire structural member, for example the bridge B, is formed of sheet material folded in a prescribed manner and glued. or otherwise bonded together, along relatively large overlying surface portions thereof. Preferably, the
sheet material of which the structural system is formed is papcror cardboard. The connections between the elements forming the structural system of the invention are accomplished by bonding together superposed, i.e., overlying surface areas of-the sheet material elements. Thus, the structural system according to the present invention is comprised of a system of geometric folded modules which are, according to the preferred embodiment, bonded together at overlying surfaces thereof.
The structural system according to the present invention consists of two basic elements. Eachof these basic elements is fabricated of sheet material, preferably a laminate of paper or cardboard such as is commonly used in heavy duty packaging but other material such as sheet metal, aluminum, plastics, sprayed concrete or mortar over steel mesh is also suitable. The first element of a web 10 (FIG. 13) formed of a system of folded plates 11 developed by laminating several longitudinally creased layers 12a, 12b, 120, etc (FIG. 7), of paper, to each other. The longitudinal web means 10, thus formed, includes at least one pair of integrally connected, elongated, folded plates 11 having spaced surface portions 11a and 11b defining between themselves an elongated channel 13. In a structural system such as the bridge B, for example, a plurality of these folded elements 12 are transversely interlocked, as illustrated in FIG. 7, so as to prevent a saw-tooth profile in a transverse plane. The interlocked elements form the longitudinal web means which stands longitudinally the length of the bridge.
The second basic element is a hollow shell member of sheet material, preferably in the form of a pyramid 20 (FIG. 8). A plurality of these pyramidal elements 20 (inverted) and 20 (upright) are positioned between the folded plates 11 on the top and bottom of the first element 10 and nested in the respective channels 13 and 13 formed by the first element. The pyramids 20, 20 are longitudinally distributed along and located in the various elongated channels l3, 13. with each of the pyramids having a first pair of opposite surface portions 21a, 21b in superposed relation with the spaced surface portions llu, l lb, respectively forming the corresponding channel l3, 13'. The fold lines of the longitudinal web means alternately form crests l4 and troughs 14' which respectively lie in a pair of spaced parallel planes defining the bounds of the structural system. The hollow shell pyramids 20 and 20' are open at their bases and are positioned in side-by-side relationship in the corresponding elongated channels l3, 13, in such a manner that preferably the bases of the pyramids 20 lie in one, and the bases of the pyramids 20', in the other. of said parallel planes. Thus, the pyramids 20 are located in upwardly opening channels 13, while the pyramids 20 are located in downwardly opening channels l3 and inverted with respect to the pyramids 20. Furthermore, the pyramids 20, 20 in a pair of adjoining upwardly and downwardly opening channels l3, 13' are preferably staggered (FIG. 6) with respect to each other, in such a manner that the apices of the pyramids 20 will lie substantially in the region of the line of contact between adjacent base edges of adjacent pyramidal elements 20 located on the opposite side of the plate element 11 separating the channels 13 and 13'. Thus, the apex 22 of an upright pyramid 20', in one of the channels 13', will preferably be located in the region of the base edge line 23a of the inverted pyramid 20 located adjacent thereto, in the next adjoining channel 13, and so one for the remaining pyramid elements, with the result that the inclined edges of the staggered inverted and upright pyramids 20 and 20, in adjacent channels, are very nearly c0- linear and coact to resemble the chords of a truss.
While not here illustrated, it will be understood that pyramids 20 and 20. in adjacent channels 13 and 13', respectively, need not be staggered with respect to each other, but could be positioned such that the apex of each pyramid 20 will lie in the region of the midpoint of base line 23 of the next adjacent upright pyramid 20 on the opposite side of a plate element 11 therefrom.
The hollow-shell pyramidal elements 20, 20' are developed by cutting out a suitable flat geometric shape of sheet material and subsequently folding the latter along suitable fold lines 24 into desired pyramidal shape (FIG. 8).
After being nested in the web element the pyramids are preferably tied together with a third element, namely transverse web means 30, shown in FIG. 11.
The transverse webs 30 are preferably in the form of diamond-shaped sheets 31 folded along the short axes 32 thereof. As a result, each member 31 includes a pair of integrally connected sheet sections 33 and 34, suitable for connecting together adjacent ones of the pyramids 20 or 20', in the respective channel 13 or 13'. When folded, the portions 33, 34 of the transverse web members define between themselves second channels 35 extending transversely with respect to the channels 13, 13' of the longitudinal web means. On of the triangular sheets sections, e.g., 33, of the transverse web member 30, is positioned in superposed relation with a second surface portion b (FIG. 14) of one of a pair of longitudinally adjacent pyramids 20a and the triangular sheet section 34 of the transverse member is positioned in superposed relation with the adjacent one of the second surface portions 25a of longitudinally adjacent pyramid 20b. Preferably, the aforesaid triangular sheet sections 33, 34 of the transverse web member 30, will correspond substantially to the shape of the second surface portions 25a, 25b of the pyramids and will overly and be bonded to the corresponding triangular second surface portions of such pyramidal elements, respectively, for connecting together pairs of such pyramidal elements in side-by-side relation. The transverse web members 30 cooperate with the pyramidal elements to even further stiffen the longitudinal web means 10 and thus provide the latter with even greater resistance to buckling. Accordingly, there is developed a very reliable, rigid, structural system capable of economically and efficiently spanning relatively large distances.
As a result of the above described surface-to-surface interconnection of all the elements of the system, external loads applied to the systems are distributed therein in all directions, thus alleviating stress concentrations in the directly loaded parts.
A connecting means 50 which may be in the form of household glue or a similar means suitable for the particular sheet material used, is provided for use in erecting the individual hollow shell elements, the transverse web means and the longitudinal web means and for integrally connecting all these elements together at the aforesaid superposed surface portions thereof, to form the composite integral structure just described.
The preferred embodiment of the structure further includes a plurality of closure elements of sheet mate rial. A first group of these closure elements are the elements 60 which are preferably of truncated pyramidal form (FIG. 12), configurated so as to correspond to and be received in the open bases of the inverted pyramids 20. Elements 60 have side wall surfaces 60a, 60b. 60c and 60d adapted to overlie portions of respective walls 25a, 25b, 25c and 25d of the respective pyramid 20 in which the closure element is nested. The closure elements 60 further have a closed end wall 61 which forms a closure for the otherwise open bases of the pyramids 20. Theelosure surfaces 61 of all of these closure members 60 are located substantially in the plane i.e., the upper one of the aforesaid pair of parallel planes and y which delimit the web means 10. Together the end walls 61 form a substantially flat eontinuous surface in plane The truncated pyramidal closure pieces 60, illustrated in FIG. 12, are preferably prefolded and prestressed so as to be properly bondable to the inner surfaces of the cor-responding pyramidal elements 20 after being nested therein. Alternatively. the pyramids 20 may initially be formed as ho]- low, fully enclosed, elements.
For closing the ends of each of the channels 13 (in which the pyramids 20' are preferably staggered with respect to the pyramids 20 in the adjacent channels 13, by a distance equal to one-half the length of a pyramid 20) there are preferably provided hollow end closure elements 64 (FIG. 9) each of which corresponds substantially in size and shape to one-half of a pyramidal element 20. According to the preferred embodiment, the pyramids 20 and 20' are of equal size. Each element is preferably formed of a pair of glued-together folded sections 64a and 6412.
At the opposite longitudinal ends of each series of inverted'pyramids 20 there may, according to the preferred embodiment, be provided end closures 63, such as illustrated in FIG. 10. End closures 63 are preferably also in the form of hollow shell elements each of which has three triangular sides and a triangular open face. The apex of the intermediate ozne, 63a, of the triangular sides, is located in the colinear base line of the remaining triangular sides 63b and 630. The hollow elements 63 form a flat end closure 63:: at the end of each string of longitudinally distributed pyramidal elements 20.
The bridge B, according to the preferred embodiment of the present invention, further includes a decking for transferring the loads evenly to the remainder of the structure. This decking, while preferably also formed of sheet material, is so constructed as to be capable of withstanding the concentrated wheel loading of motor vehicles, including heavy trucks. As previously noted, the end walls 61 of the closure elements 60 provide a flat continuous surface on the top of the structural system capable of having bonded thereto. as at 51, in face-to-face relation, the underside of the flat decking member 70.
It its preferred form, the decking member 70 is comprised of a pair of laminated layers 71 and 72 of a'sheet material and an intermediate layer 73 comprised of a series of parallely arranged cylindrical tubes 74, also of sheet material. These tubes are preferably in side-byside contact with one another and preferably extend transversely with respect to the length of the decking so as .to reinforce the pair of spaced flat layers 71 and 72 of laminated sheet material located on opposite sides of and bonded to the intermediate tube layer.
As a result of its unique design, the above described components of the structural system (FIG. 14) may be readily assembled together at the construction site by bonding these together along the aforementioned overlying surface areas thereof. The large surface areas available for bonding result in exceptionally strong and reliable connections. The specific glues and cements best suited for such bonding will depend on the particular sheet materials involved, and are well known to those skilled in the art. A high-load-bearing structural system, such as a bridge, may thus be fabricated solely out of sheet materials, such as paper.
Preferably, each of the component parts, for example the pyramids 20, the longitudinal web means 10, the transverse web means and the closure elements 60 and 63, is fabricated out of individual, stock size, sheets of paper, by cutting the latter into desired shape, scoring the paper along desired fold lines and then laminating together individual sheets of such scored paper in such a manner that (as illustrated with respect to web 10, in FIG. 7-) alternate sheets of the paper are po sitioned with their region of discontinuity in nonoverlapping relation. In FIG. 13, it will be see, that, for example, the lines of discontinuity 26a and 27a of the adjacent layers 26, 27, respectively, of a pyramidal element 20, are located at opposite edges of the pyramaid and are not adjacent to one another. Thus, the region of discontinuity of any individual sheet is reinforced by a non-discontinuous region of an adjacent sheet, so as to -minimize any effect of such discontinuity on the structural strength of the element. After folding into desired shape, the scored folds of the pyramid may be filled with flue to provide an even stronger structural joint along such fold lines.
The term paper" as used herein is intended to include suchsheet materials as paper board, liner board, fiber board and cardboard.
Not only do the strength and stiffness properties of paperdiffer greatly in compression and in tension, but
' paper is also an anisotropic material, i.c., it displays different structural properties along different axes thereof. According to the preferred embodiment of the present invention, particular advantages result from the latter speciallstructural properties inherent in paper. For example, the tensile strength of the paper is nearly twice as great in the direction of the grain of the paper as it is in the cross direction. According to the preferred embodiment. all of the elements of the structure are comprised of folded and glued flat surfaces shaped to take full advantage of the special properties of pa per. Thus the webs II) are constructed with the grain of the paper thereof extending in longitudinal direction, and the pyramids 20, 20 are constructed with the grain of the paper thereof extending peripherally, i.c., in a direction about the apex. The pyramid closure elements 60 are cut and prefolded so as to form prestresscd, i.c., spring-like inserts for the tops of the inverted pyramidsZO. Coated with glue, the closure elements 60 are inserted into the open faces of the pyramids and prcss'outwardly against the pyramid walls to provide proper bonding along all adjoining surfaces.
Since the structural system according to the present invention is composed of hollow elements and since the hollow pyramidal elements 20 are bonded to the interiorsurfaces of the longitudinal web means 10, the pyramidal elements are also subjected to the stresses borne by those portions of the longitudinal web means to which they are attached. Furthermore, the inclined corner portions, i.e., edge portions 24 of each of the pyrarnidal units 20, 20, from the apex 22 down to the base 23 thereof, act as truss members, thereby forming, with the other inclined edges of the remaining pyramidal units, an integrated truss system.
Each of the edges 24, of the pyramidal elements, thus forms a cord of a truss so that the resulting structure is made up of a series of interconnected triangular truss units having the rigidity and stability incident to structural triangulation. As a result of the surface-to-surface interconnection of all of the elements of the structure, applied external loads are distributed in all directions, thus acting to reduce the otherwise high stresses in the directly loaded portion.
By way of example, a paper bridge, approximately ten feet wide and four feet deep, was constructed inaccordance with the present invention. The bridges, having a length of 32 feet was able to easily bear the weight of a l2,000 pound truck when the latter was driven over its 30 foot span numerous times. During load testing, for support of the 12,000 pound truck, the paper structure deflected only one-half inch within its 30 foot span. The bridge weighed approximately 9,000 pounds and consisted entirely of paper and glue. The sheet material (1) used for constructing the elements of the structure, for example, the pyramidal elements, the longitudinal webs, the transverse webs and the decking, was 0.1 inch thick Solid Fibre which consisted of four plies of 90 No. Kraft liner-board (heavy duty paper) laminated together. The various component elements of the structure were bonded together along overlying surfaces thereof, as described above, forming laminated sections such as, for example, section E (FIG. 15) 0.4 inches thick, and section F (FIG. 15) 0.6 inches thick. Joined together, these elements form a stressed-skin structure that behaves like an orthotropie bridge. The sheets 12a, 12b, 120, etc., as well as sheets 26a and 27a, etc., were each 0.1 inch thick as per above.
The deck (FIGS. 15 and 16) was fabricated of parallel. side-by-side, cylindrical paper tubes 74 also comprised of laminated sheets of paper. By way of example, the tubes 74 have a wall thickness of approximately onehalf inch and an inside diameter of approximately 3 inches. The tubes are sandwiched between a pair of spaced flat layers 71 of laminated sheets of paper I. 1
While the deck 70 has been illustrated with a core of cylindrical paper tubes 74 laminated between flat layers of sheet material 71, it will be understood that other deck structures, for example, one having a sawtoothshaped laminated core (not shown), similar to the Iongitudinal web structure of web 10 described above (FIG. 3), and sandwiched between the pair of laminated sheet layers 71, would also be satisfactory and is intended'to be included within the scope of this invention.
By way of example, the pyramidal units of the latter bridge are each approximately 2 feet high and have a rectangular open base approximately 48 inches in length (longitudinal direction of web 10) and approximately 24 inches in width (transverse direction).
The pyramids 20, 21' are longitudinally distributed, with adjacent base edges thereof in close proximity to one another, in the corresponding elongated channels 13, 13. The apex angles of a pair of opposite sidewalls 21a and 21b of the pyramidal elements 20 are preferably chosen to correspond to the apex angle formed between plates llu and 11b of the longitudinal web means 10. The sheet material used in the structure according to the present invention, while preferably paper, may be any suitable sheet material. such as sheet steel, sheet aluminum, sheet fiberglass, as well as other structural plastic sheet materials, or the like.
It will be seen that the structure of this invention is such that the component parts thereof can be simply and inexpensively manufactured, transported and assembled together.
It can be seen that the structure described herein can have many applications in addition to use as a supporting beam or bridge. For example, a structure according to the present invention would be useful in cases where buoyancy is desired. Thus, by using water resistant materials, or water resistant coatings over water permeable materials, a structure according to the present invention could, for example, be used as a pontoon" bridge. By using additional closure pieces, similar to elements 60, to close off the open ends of the bottom pyramids a fully enclosed cellular structure is formed. The air-filled, fully-enclosed, pyramidal units and the enclosed spaces therebetween, result in a buoyant structure.
It will be understood that a composite structural unit according to the present invention, i.e., longitudinal web means and pyramidal elements distributed therealong and connected thereto, as described, lends itself admirably to use as a structural element. Such structural element may, for example, be comprised of a single V-shaped web 11a, 1 lb and a plurality of longitudinally distributed pyramids 20 nested in the channel 13 thereof and connected thereto, as taught herein. Such composite structural member can span relatively large distances without requiring intermediate columnar supports. The structural system of the present invention combines the structural characteristics of a skeleton frame system with those of a stressed skin system. Thus, the system according to the present invention has an unusually high strength to weight ratio because of the internally continuous braced skin-structure and because of the fact that pyramidal elements have a high ratio of surface area per unit volume and consequently are among the most stable of all polyhedrons.
It can be seen that this invention provides improved strength members for a bridge, or a roof, or the like, comprising uniquely formed sheet material elements uniquely combined to provide a supporting structure which is relatively light in weight yet very strong.
It will be understood that where sheet material other than paper is used, for example plastic or light-gauge steel or aluminum, the means for integrally connecting the sheet members at overlying surface portions thereof may include such connecting means as spotwelds, solder, rivets, heat seals and any other fastener or bond which permits surface-to-surface connection between the flat surfaces of the geometric shapes formed by folded sheets of such materials. In lieu of the pyramidal elements, of course, other hollow solidgeometric shaped elements can be used provided they have flat surfaces which permit a surface-to-surface connection in substantially the manner herein described.
It will also be understood that by increasing the thickness of the sheet material or the number of sheets of material in each layer and/or by increasing the number of pyramidal elements in a given channel, the strength of the composite structure may be even further increased.
While particular embodiments of this invention have been shown and described, it will be obvious to those skilled in the art that there are changes and modifications which may be made without departing from the scope of the invention in its broader aspects, and it is, therefore, intended in the claims to cover also such changes and modifications as fall within the true spirit and scope of this invention.
Having thus described my invention, what l claim and desire to protect by Letters Patent is:
l. A bridg'efor spanning the: distance between a pair of horizontally spaced supports;
longitudinal web means of sheet material consisting of a pleated sheet member extending substantially horizontally between the supports and having a saw-tooth profile in a transverse plane, said pleats of said sheet member comprising planar mutually inclined walls defining alternately upwardly and downwardly open longitudinal channels in side-byside relation;
a plurality of pyramid-shapcd hollow elements of sheet material longitudinally distributed along and located inside-by-side relation, in at least a pair of said upwardly and an intermediate one of said downwardly open channels, each of said hollow elements having a pair of opposed wall portions in face-toface contact with adjacent walls of said pleated member, respectively;
said hollow elements in said upwardly open channels having closed planar base portions located substan tially in a common plane defined by the upper fold lines of said pleated member;
planar decking means of sheet material overlying said closed planar base portions of said hollow elements; and
connecting means connecting together said hollow shell elements with said decking means and with said pleated member at corresponding overlying surface portions thereof.
2. The bridge according to claim 1 wherein said sheet material is paper.
3. The bridge according to claim 2 wherein said decking means comprises a pair of outer spaced layers of laminated paper and an intermediate layer of transversely oriented tubular paper members distributed in side-by-side relation substantially along the entire length of said decking and bonded to said outer layers.
4. The bridge according to claim 2 wherein said decking. said pleated member and said hollow shell elements each consist of laminated sheets of paper.
5. The bridge according to claim 1 further comprising transverse web means for connecting together adjacent ones of said shell elements in at least one of said channels.
6. The bridge according to claim 1 wherein said pleated member and said pyramid elements each consist of laminated sheet material, alternate layers ,of sheets of material in each said laminated sheethaving discontinuous portions staggered with respect to the discontinuous portions of the remaining ones of the