CA2082530A1 - Structural beam - Google Patents

Abstract

A fabricated structural beam (10) comprises at least one longitudinally folded member having a web portion (16) and a head portion (12, 14). In different embodiments, a plurality of folded members may be interleaved with one another to provide configurations of varying load carrying capabilities. In all cases, the folded head portion (12, 14) is made rigid by forming it into a tube that is closed on all sides. This is accomplished by fastening the folded material upon itself in the web portion (16).

Description

-STRUCTURAL BEA~I
RELATED APPLlCATlO~

This is a continuation-in-part of serial no. 07/518,554 filed May 3, 1990.

FIELD OF THE INVENTION

This invention relates to the field of structural building materials, and more particu]arly to a fabricated structura] beam.

BACKGROI~ND OF T~ ~V~ON

A variety of types of structural beams are used in non-residential construction. Some examples include fabricated wooden girders, laminated wood beams and reinforced concrete beams. By far, the most commonly used material is struc~ural steel of various cross sections, such as "I"-section, "H"-section, "C"-section, "Z"-section and channel section. These structural steel shapes are most commonly manufactured by hot or cold rolling processes and generally provide a rela~ively heavy beam for a given load carrying capacity.

Structural sections fabricated from sheet steel are used in some COnStJuCtiOn applications. For example, it is now a common practice to utilize fabricated steel studs, particularly in non-residential construction.
Thesc are gcnerally made from galvanized steel sheet~ cold-rolled into a "Cn-section or channel section. Furthermore, corrugated or fluted steel sheets are widely used in flooring and roofilng applications.

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- 2~ ~ 2 Certain other fabricated structural shapes are known in the prior art.
For example, Figure I illustrates a prior art structural shape fabricated from sheet steel. Beam I comprises a web portion 2 and opposin~ head portions 3 and 4. As can be clearly seen in the illustration, beam 1 can be easily fabricated from a single flat sheet of steel by rolling or otherwise foldir~g the sheet longitudinally; lt should be noted that edges 5 and 6 of the sheet are folded back towards web portion 2, but are not fastened or otherwisc sc-,uicu ih~relo. A prior art beam such as beam I has a very limited load bearing capability.

It is one of the objects of the present invention to provide a fabricaled structural beam that has a load carrying capability comparable to that of conventional hot or cold rolled structural steel sections, but which is light in wcight compared to a conventional section of equal load carrying capability.
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SUMMARY OF THE INVEN~ION

The fabrica~ed structural beam of the present invention comprises a~
least one longitudinally folded member having a web portion and a head portion. In diffelent embodiments, a plurality of folded members may be interleaved with one another to provide configurations with varying load carrying capabilities. In all cases, the folded head portion is made rigid by forming it into a tube that is closed on all sides. This is accomplished by fastening the folded material upon itself in the web portion. Further embodiments of the invention fabricate the head portions of the beam from individual longitudinal members.

' 2~ ) 4 ~REF DES(; RTPllONQF THE D~AW~GS

Figure 1 is a cross sectional view of a prior art fabricaled struc~ural beam.

Figure 2 is perspeetive view of a preferJed embodiment of a fabricated structural beam according to the present invention.

Figure 3 is a cross sectional view -f the ~m. sh^wn. i.. Fi~,u.o .

Figures 4a, b illustrate the individual folded members used to construct the beam illustrated in Figures 2 and 3.

Figure 5 illustrates another embodiment of the present invention.

Figure 6 illustrates a modification of the embodiment shown in Figure 5.

Figure 7 illustrates yet another embodiment of the present invention.

Figure 8 illustrates a modification of the embodiment shown in Figure 7.

Figure 9 illustrates still another embodiment of the present invent~on.

Pigurc 10 illustrates yet a further embodimen~ of the present 2~;?
invention .

Figure 11 illustrates an additional embodiment of the present invention .

Figures 12a-12c illustrate variations on an embodiment of the present invension having fabricated head structures.

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2~fi?~'~ 6 DETA~ED l:)ESCRIP~lOI~ OF THE lNVENTlON

ln thc following description, for purposcs of explanation and not limitation, specific numbers, dimensions, materials, etc. are set for~h in order to provide a thorough understanding of the present invention.
Howcvcr, it will bc apparent to one skilled in the art that the present invention may be pract;ced in other embodiments that depart from these specific details.

Referring first to Figures 2 and 3, a preferred embodiment of the preseot invention will be described. Beam 10 comprises a pair of triangularly shaped head portions 12 and 14 joined together by web portioo 16. In o~erall configuration, beam 10 is thus similar to a conventional "I" beam. Howevcr, unlike a convcntional structural bcam, bcam 10 is fabricated from relatively thin gauge sheet material. In most applications, beam 10 will be built up from cold rolled sheet steel.
However, it is lo be understood that the present invention is not limited to such a choice of material, but may be constructed from any suitable mallcablc sheet material. In particular, certain applications may recommend the use of alunminum or even a plastic. -.
The construction of beam 10 can best be undcrstood with referenceo Figures~ 4a~and 4b which illustrate the individual members 20 and 30 that are interleavcd to form beam 10. Member 20 is folded longitudinally :
and comprises a web portion 22, triangular head portion 14, web flange 24 and ~tail flangc 26. In thc illustrated embodiment, member 30 is identical to member 20, but need not be so. Members 20 and 30 are interleaved ~ :
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' ~ Ul!~7~7Y ~ Ji~3~i;a-~-77 such Ihat web portion 22 of member 20 extends between web por~ion 32 and web f1ange 34 of member 30. Likewise, web portion 32 of member 30 e~tends between web portion 22 and web flange 24 of member 20. Tail flangc 26 of member 20 abuts wall 13 of triangular head portion 12.
L.ikewise, tail flange 36 of member 30 abuts wall 15 of triangu]ar head portion 14.

It is preferable that the cross-section of head por~ions 12 and 14 be substantially equilateral triangles. However, the invention is not limited in this regard.

Members 20 and 30 are secured to one another by fastening means 18. Fastening means 18 may comprise conventional mechanical fasteners, such as rivets or screws. Fastening-means 18 may also comprise other conventional fastening means, such as spot welding or adhesives. The preferred embodiment utilizes a fastening technique sold under the trademark TOX by Pressotechnik, GMBH and its licensees. This technique employs a stamp and die ~o join together two or more thicknesses of matenal in a cold extrusion forming process. The TOX process is particularly advantageous for use with the present invention since it is fast, does not employ consumable fasteners and does not rupture anti-corrosion coatings. ~ -.
Web portion 16 of fabricated beam 10 comprises two thicknesses ofmaterial. For applications requiring a greater web thickness, either or both of web flangcs 24 and 34 may be extended such that web portion 16 comprises three or four thicknesses of material.

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2q ~,?~) 8 Beams of ~he present invention, such as beam 10, may be conveniently fabricated by a continuous process wherein coils of sheet stecl are fed through a suitable arrangement of rollers to impart the desired longiludinal folds and simultaneously interleave the members.
The- fabricated beam then passes through an array of mating stamp and die sets to fasten the members together at suitable intervals. The Icngth of the completed beam is not inherently limited by such a process, and thus beams of any practical length can be readily manufactured. Moreover, the arrangement of rollers can be rclatively easily altcred to produce beams of differing transverse dime~sions. The manufacturing process also easily accommodates sheet materials of different thicknesses so that the load capacity of the manufactured beam may bc selected for each lot produced.
For relativcly large cons~ruction projects, suitable equipment may be located at the job sitc to pFoduce beams according to the present invention in a manner somewhat analogous to that used for on-site fabrication of res;dential guttcrs.

~ Referring next to Figure S, another embodiment of the present invcntion is illustratcd. Here, bcam 40 comprises members 42 and 44.
These membcrs may be fastencd togethcr at locations 45, 46 and 47 as shown in Figure 5; howevcr, it is preferablc to insert a third member 50 :
betwccn membcrs 42 and 44 as shown in Figurc 6. Inscrt SO includes tail anges S2 and S4 that abut against thc respectivc triangular head portions of mcmbers 42 and 44. Members 42, 44 and 50 are fastened toge~her by fastening mcans 18 as describcd above. The rcsulting structurc of beam ~ .
40 is quite ~similar to that of bcam 10 as illustrated in Figure 3, except that : ~:

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the web portion comprises three thicknesses of materiah l`his embodiment has the particular advantage that member 50 may be made of a heavier gauge material than members 42 and 44, thereby imparting additional strength to beam 40 without necessarily increasing the thickness of material in she head portions of the beam. It should be noted that membcr 50 may comprise a conventional T beam or other conventional steel section where substantial reinforcement is desired. Member 50 need not be inserted over thc entire span of beam 40, but may be inserted only in certain longitudinal regions requiring additional reinforcement.

Still another embodiment of the prescnt invention is illustrated in Figurc 7. Beam 60 comprises a single longitudinally folded member having parallel web portions 62 and 64, head portion 66 and opposing tail flanges 68 and 70. This embodiment can be utilized as illustrated in Figure 7 by fastening web portion 62 and 64 together at locations 72 and 74.
However, it is preferable to add a second longitudinal member 76 as showD in Figure 8. Member 76 includes tail flangc 78 that abuts head portion 66. As with the other embodiments thus far described, web portion~ 62 and 64 and member 76 are secured by fastening means 18. As with the embodiment illustrated in Figure 6, member 76 may be of the same or a~ heavier gauge than thc remainder of thc beam.

Rcfcrring now to Figure 9, a modification of the embodiment illustrated in Figures 2 and 3 is shown. In this embodiment, members 20' nd 30' arc cssentially identical to members 20 and 30 previously described exccpt for corrugations 80 and 82. These corrugations arc added to providc additional stiffness in beam 10'.
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'- 10 In a similar manner, Figure 10 illustrates a further modification of beam 10 as shown in Figures 2 and 3. Beam 10" includes embossed ribs or corrugations 86 on the sloping walls of head portions 12" and 14". It will be understood that other patlerns of corrugations and other means of rcinforccment may be incorporated with any of the embodiments described herein.

With reference now to Figure 11, yet another embodiment of the present invention is shown. Beam 100 is constructed in a manner essentially similar to the embodiments described above. Howevert this design offers significant advantages as will be described below.

Beam 100 comprises web member 102, which includes tail flanges 104 at each end. Beam 100 also comprises a pair Df ;dentical head members 106. Each of head members 106 is folded approximately in the shape of an equilateral triangle having sides 107, 108 and 109. Side 109 terminates with web nange 110 and side 107 terminates wi~h web flange 111 in like manner. Flanges 104 of web member 102 are secured to sides 108 of head members 106 by mcans of fasteners 18. Likewise, tail flanges 104 of web member 102 are secured to sides 108 of head members 106 by mcans of fasteners 18. As discussed in connection with the pre~iously described cmbodimcn~s, fastencrs 18 may be any suitablc form of fastener. However, in this embodiment, the TOX fastening system is not prefcrred because of the difficulty of positioning a dyc within the triangular head members. More suitablc fastening means for this cmbodiment are rivets or spot welding.
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2~?.c~3 In beam 100, shear and bearing loads are carried by sides 107 and 109 of head members 106 and also by web member 102. By fastening the web mernber flanges 104 to head member sides 108, greater flexural strength is achieved in comparison to the beams described above.
Moreover, web member 102 of this embodiment increases the buckiing strength of the head members. The thickness of web element 102 may be selected ~o achieve any desired beam s~ength. It is to be noted that this selection may be independent of the selecled thickness of head members 106, thereby a]lowing the structural characteristics of beam 100 to be optimized for particular applications.

Figures 12a-12e i]lustrate further Yariations of structural beams within the scope of this invention. RefelTing first to Figure 1 2a, the basic characteristics of lhis design will be described with equal applicability to the variations shown in Figures 12b-12e. Beam 120 comprises a pair of identical web members 122. Each of web members 122 has a center portion 124, outwardly angled intermediate portions 126, and ~lange portions 128. Web members 122 are attached ~o one another at their respective center portions 124 by means of fasteners 18.

Beam 120 further con prises head members 130 secured to respective flange portions 128 of the web members, also by means of fasteDers 18. Beam 120 differs from all of the previously described beams in tbat the triangular head structures are not folded from a single sheet of material, but rather arc fabricated from individual elements, namcly, intermediate portions 126 of web members 122 and head members 130.

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-These elements define a tubular structure with a generally triangular cross-section as in all other embodiments described thus far.

Beam 140 illustrated in Figure 1 2b is essentially identical to beam 120, but employs extended head members 142. Beam 150 shown in Figure 12c is again essentially identical to beam 120 but employs channel shaped head members 152 Figure 1 2d illustrates a beam 160 wherein head members 162 have a "C"-section. Figure 12e shows beam 170 in which head member 172 includes a longitudinal depression 173 that serves as a stiffening element. Head member 174 is shown as a simple plate identical to head members 130 of beam 120. However, it is to be understood that head member 174 could be iden~ical to head member 172.
In fact, any combination of head members can be utilized with the basic structure comprising web members 122 to accommodate special applicati ons, By virtue of nange elements 128 oî the various embodiments illustraled in Figures 1 2a-1 2e, these beams are particularly well suited for fastening horizonlal collateral elements, such as floors or cei]ings, from either the top or bollom of each flange By virtue of vertical flange elements 155, beams 150 and 160 are furlher adapted for faslening vertical collateral elemenls, such as partitions, wallboard, or window wall directly to the beam, Moreover, vertical nange elements 155 facilitate fastcning beams 150 and 160 from the side to conventional strap hangers and the like. As in all of the previously described embodiments, the thickness of the individual members of these beams may be selected to achieve virtually any desired structural characteristics The beams ...

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illustrated in Figures 12a-12e offer the particular advantage of being more economical to manufacture, partly due to the fact that obtuse folds of material are not required.

It will be recognized that the above described invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the disclosure. Numerous variations will be apparent to persons skilled in the art of structural design. For example, while the embodiments discussed above are most advantageously constructed of cold rolled sheet steel, a hot rolling process may be employed in certain applications. In particular, it should be noted that cold rolled and hot rolled sections may be combined as discussed above in connection with Figure 6. Furtherrnore, because of the open nature of the beams of the present invention, a plurality of such beams may be "nested"
within one another to provide a greater load bearing capability than a single such beam without increasing the gauge of sheet material used.

To illustrate the advantages of the present invention, ~he following ta~les compare ~he ca]culated performance of a test section comprising the embodiment illustrated in Figures 2 and 3 with various standard s(ructural shapes. In each of the following tables, the beam of the present invention has a height of 200 millimeters and a width of 60 millimeters. Resul~s for three material thickness are presented, namely 1.0 millimeter, 1.2 millimeter, and 1.6 millimeter. All results are for standard sections of hot rolled British grade 43C steel, which is generally equivalent to ASTM A36.

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In the following tables, Columns (a), (b), and (c) give the mass per meter, cross sectional area and moment of inertia for the sections respectively. Column (d) gives the load considered for detlection purposes, W D, based on Ihe design criterion that the maximum deflection should be less than l/360th of a beam length of 3 meters. Column (e) gives the load ratio with respect to the tesl section. Column (f) gives the maximum span for each section when the point load equal to WD for the test section is applied to the simply-supporled beams. Column (g) gives the maximum span ratio with respect to the test section.

When a section of the present invention is compared with standard sections of similar mass per meter, its moment of inertia is significantly larger than that of the other sections. Thus, it supports more loading compared with the s~andard sections. Similarly, jt spans longer than the standard sections for the same maximum deflection.

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Claims

1. A fabricated structural beam comprising at least one longitudinally folded member having, in contiguous relationship, a first web portion, a folded head portion having first, second and third segments, and a second web portion fastened to said first web portion so that said head portion forms a three sided tube.

2. The fabricated structural beam of Claim 1 wherein said first, second and third head portion segments have substantially equal transverse dimensions such that the cross section of said head portion is a substantially equilateral triangle.

3. The fabricated structural beam of Claim 1 wherein said at least one longitudinally folded member is cold rolled from sheet steel.

4. The fabricated structural beam of Claim 1 comprising two longitudinally folded members substantially identical to each other and fastened together at their respective web portions.

5. The fabricated structural beam of Claim 4 wherein said web portion of each of said longitudinally folded members extends within said head portion of the other such member and terminates at a tail flange abutting said head portion of the other such member.

6. The fabricated structural beam of Claim 5 wherein each of said tail flanges is fastened to said head portion of said other folded member.

7. The fabricated structural beam of Claim 1 wherein at least one of said first, second and third head portion segments is embossed with a plurality of reinforcing ribs.

8. The fabricated structural beam of Claim 1 further comprising a longitudinal reinforcing member fastened to said first and second web portions.
9. A fabricated structural beam comprising:
a first longitudinally folded member having a web portion and a folded head portion having a triangular cross section, said head portion including a web flange extending substantially parallel to said web portion;
a second longitudinally folded member substantially identical to the first and interleaved therewith such that said web portion of each longitudinally folded member extends between said web portion and web flange of the other;
said first and second longitudinally folded members fastened to one another at their respective web flanges.

10. The fabricated structural beam of Claim 9 wherein each of said first and second longitudinally folded member is folded along an edge opposite said head portion to form a tail flange extending approximately perpendicular to said web portion.

11. The fabricated structural beam of Claim 10 wherein said tail flange of each longitudinally folded member abuts said head portion of the other longitudinally folded member.

12. The fabricated structural beam of Claim 11 wherein each of said tail flanges is fastened to said head portion of said other folded member.
13. The fabricated structural beam of Claim 11 wherein at least part of said web portion of each of said longitudinally folded members is corrugated.

14. The fabricated structural beam of Claim 13 wherein said corrugated part of said web portion of each of said longitudinally folded members is wholly disposed within said head portion of the other longitudinally folded member.

15. The fabricated structural beam of Claim 9 wherein at least one surface of said head portion of each of said longitudinally folded members is embossed with a plurality of reinforcing ribs.

16. A fabricated structural beam comprising:
a first longitudinally folded member having first and second web portions and a folded head portion having a triangular cross section;
a second longitudinally folded member substantially identical to the first and oriented with respect thereto such that their respective first web portions overlap;
said first and second longitudinally folded members fastened to one another at said overlapping first web portions.

17. The fabricated structural beam of Claim 16 further comprising a central longitudinal member inserted between said web portions of said first and second longitudinally folded members.

18. The fabricated structural beam of Claim 17 wherein said central longitudinal member is longitudinally folded along opposing edges to form substantially perpendicular flanges.

19. The fabricated structural beam of Claim 18 wherein said flanges of said central longitudinal member abut the head portion of said first and second longitudinally folded members respectively.

20. The fabricated structural beam of Claim 19 wherein said flanges of said central longitudinal member are fastened to said respective head portions.

22. A fabricated structural beam comprising a longitudinally folded member having a pair of substantially parallel web portions fastened to one another, a folded bead portion having a triangular cross section and a folded tail portion forming a pair of flanges extending from each of said web portions and substantially perpendicular thereto.

23. The fabricated structural beam of Claim 22 further comprising a central longitudinal member inserted between said web portions of said longitudinally folded member.

24. The fabricated structural beam of Claim 23 wherein said central longitudinal member is longitudinally folded along one edge thereof to form a substantially perpendicular flange.

25. The fabricated structural beam of Claim 24 wherein said flange of said central longitudinal member abuts the head portion of said longitudinally folded member.

26. The fabricated structural beam of Claim 25 wherein said flange of said central longitudinal member is fastened to said head portion of said longitudinally folded member.

27. The fabricated structural beam of Claim 23 wherein said central longitudinal member is a hot rolled steel section.

31. A fabricated structural beam comprising:
a pair of web members, each having a center portion, first and second outwardly angled intermediate portions and first and second flange portions contiguous with said respective intermediate portions, said center potions fastened to each other at their respective center portions;