CA1131872A

CA1131872A - Framework structure

Info

Publication number: CA1131872A
Application number: CA357,550A
Authority: CA
Inventors: Norbert Wackernell
Original assignee: INTERWACO AG
Current assignee: INTERWACO AG
Priority date: 1979-08-06
Filing date: 1980-08-01
Publication date: 1982-09-21
Also published as: AT362112B; EP0023721A2; ATA538679A; EP0023721A3

Abstract

FRAMEWORK STRUCTURE

ABSTRACT OF THE DISCLOSURE

A framework structure, for example, for roofs of industrial structures, includes tubular members connected to one another in joints and subtending an acute angle with one another so as to take up the tensile and compressive forces. The ends of the tubular members are flattened, and each tubular member has an intermediate portion between its tubular and flattened portions. The intermediate portion is formed by walls which converge linearly in a wedge-like manner. THe walls are inclined with ine another at angle of between 20° and 28°. It is especially advantageous when a joint is provided between the flattened end portions of a chord member and a diagonal member so that the axes of these members intersect.

Description

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The present invention -relates to a ramework structure which includes a piurality o~ tubular chor~l member adapted to be positioned in a horizontal plane, and a plurality of advantay~ously thxee-dim~nsiona~, for ex~nple, pyramidal tubular diagonal members~.which are connacted to one another in joints~by their super-imposed flattened portions.
A ~ramewor~ structure of the abo~e-mentioned yeneral t~pe, ~r example for roof s of inductrial structures, is knot~n in the axt. The special advantage of this type fxamework structu~e is its capabilit~ of bridaing great widths at high bending strength, while the weight of the structure can be relati~ely small because of the narrow tubular members~
The main forces which are applied ~o ~he ~tructure act in an a~ial direction of the mem~ers as tensile forces or compressi~e forces, and lmlst b~
absorbed by the mem~ers. Here, the ends of the members must be flattened and/or drilled through in order to connect the individual members so as ~-o form joints.
The thus produced unavoidable weakening o~ the ends of the me~er6 to se~ve as connection for joints is thus very Cigni,icantO The deLo~med cross~section ohtained mainly by the flattening of the tubula~ end portions of the members, must transmit all forces applied to the joi.nts and f-.-o~ there applied through the opposite .

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~nd l~ortions o the members to tlle other members conn~cted therewith, A special cxiterion in this case is the rerou~ing of the axially ac~ing force in the diagonal membe~rs at an angle of at least 45, applie~ to the generally horizontally arranged c~ord members. This flux of the force lines leads to ~uckling stresses in iIltermediate regions of th~ members, which are narrowed or constricted by the ~lattening r and extend from khe end portions of tha l~embers toward the tubular undef:ormed part of the diagonal members~
One solution of this problem per~ormed hy ~ special construction of these weakened rcgions is descxibed in the German Gæbra~lchsmus~er- No. 7~702r704 ~ . .
The narrowing from the circular cross-section to the flattened end is perormed in accordance with the so-. called natural shape~ While one-half of the constriction adjacent to the flattened end portion is relatively strongly bulged, the inclination in the other ha1f is only moderate until it reaches the diameter. of the ;n~berO
By addi~ional inward pressing of a corrugation in the r~gion o~ constriction~ an increase of the bucklin~
xesistance similax to a corrugated sheet is attained.
. - In this stxucture a xeinforcement in the plane connecting both corrugations i5 p.rovided~
HoweYer, the corrugation results in a weakincJ o the bending str~n~th and çrushin; in a plane which i5 nOrmcl to the above~-mentioned plane, so that it directly cause~
the inward buckllng.

, .; ' L 31 8r7 2 Summary oE t11e Xnvell~ion ~ n object oE the pxesent invention is to provi.de a framework structure which avoids ~he disatlvanta~es of the pxior art~ i~ore particulaxly, it.
I is ar~ o~ject of the present invention to design the const:xicted sections of the end portions of the members in s~!ch a manner that they have sufficient buckling and bendi.ng strength without weakening,compared to undefo~med portions of the me~1nbers.
In keepiny with these objects, and with others which will become apparent herei.nafter, these objects are attained in a framework structure in which an ir.!termediate portion of each memher located between its flattened port.ions and its t~bular portion is narrcwe~ from the tubular por1ion toward the flattened porti.on substantially linearly in a wedge-shaped manner, and wherein the length or dimensions o the perimeter of the axial cross-section of each member is substantially constant throughout the entire member.
~ lthouyh the linear constriction is known rom the German Of~enlegungschrift No. 2,720,029, ~he axial force lines therein do not converge at the end o~ the constriction into a ~oint, as in the ; applicant's invention, but extend through thin connecting pieces which, when angled, have a disadvan~ageous tendency to buckle~
'he wedge~shaped surfaces allow a favorable flux of the axial pressure forces toward the joints and there~y provide a high bending strengt~O

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Xt has been shv~ from e~perimellts~ that the resistance to bucklin~ of the linear compressive deformation is hi~her by 61% than that of a na~ural compressive defo~nation. The compresc.ive de:E~rmatlon of corrugations in accordance with the above~ entioned Gexman Gebrauchs muster provides for only a 20$i higher strength compared to a nats~al compressive:de fol~ati In the above-men~ioned Ger~an Gebrauchs~
muste:~, the ideal flux of force lines éxlerlds only uver _he narrow range of the corrugation~ In ~ccordan~e with ~:he featur~s of the present inventi.on, the forces are concentratea in the join~C; over a plurality of force lines in ~uasi-coxxugations which are joined in one plane~
Linearly e~tending cc)nstxiction reg~orls ha~e not been proposed before, even though such xegions may ~e consiclered to ~e scheme~ically indicated, for example, in the German Auslegeschri.ft 1,117,S45 or in th~ German Patent 54,142. Nothing is di.sclosed in these references to indicate that any linearly extending constriction regions have surfaces subtending an angle in ~he range of between 15 to 35~ to one another.
In ad~ition, in the above--mentloned German Auslegeschrift 1,117,845 the flattened ends s~f the membex~ are radially ~l~mped in slots of a joint member, whereas in accordance with the present invention the 1attened ends axe superimposed onto, and connected to on~ another~ This combination of the joint forma'ion with the linearl~
e~tencling constriction regions is however very i~po~tant _5.~

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in ord~r to eltta1n a very hi~l- resistance to bu~kling and a ve~ higil bending strength~ :rn ~he above-mentioned Ge~an Paten-t $~,1.42, it is clearly disclosed that the tubes are co~pressed at their e~ s. Holes are the~
dxilled through the plate-like ~ortions obtained by the compression~ It is com~?le~ely cleax ~hat when only the ends are com~res~ed~ tha constrictioll assumes the natu.ral shape~ The drawing of the Ge~nan Patent~ ¦
~eing a purely schematic representation, does not correspcnd to the actual de~orma~lon produced during the comFression.
The resistance to buckling in the cons~rictea region is op~imal wh~n the suriCac~s con-~erging toward one ~lother in a 1/edge~ e manner, subtend an angle alpha between 15 to 3$~,advantageously between 20 an~ 28o An angle alpha ~qual or greater than I:
appxoximately 28 results in an .increase in the force requixed to bend the member,and thus increases the stre~ o both wedge-shaped surfacesO Crushing or . ;-buckling of the members under the action of inward turning of the defo~med constrictlon regions and a local buckling of the flat sura~es o the tu~ular member would take place if large axial forces are required to be transmitted~ ' A length~ning o ~he c~.nstriction region and consequently an angle alpha o~ less than 20 would result in a drastic w~aXened resistance to lateral buckling.

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In accoxdance with a ~urthex atlvantayeous embodimen~ of the pr~sent inventlon, the planes of 1att~ning are not only horizontal but also vertical, and the chord mernbers ar~ connected to the diagonal members by hori~ontally exten(ling screws.
~ The axrangem~nt o~ the joint is only possi~le beGause of the very ~ligh bending strength of the constriction reglon in the plane of the fla~tened end portions of the member. I'he special advantage of ~uch 21 ]oint is the fact that the force lines of the diagonal members in the joint region can extend directly to the chord me~ber axis, so t.hat the eccentricity of ~he orce lines occurring in a construction using vertically extending screws, which must ~e considered in static calculation~, is eliminated~ -Xn accordance wi'~h another embodiment of the present invention the choxd members may have a polygonal and advantageously r a square cross-section~
~hi.s e~minates the labor-consuming and time-consuming ~lattening of the chord members in the ]oint regio.nst and moreoverl does not a~fect the bending stxength of the choxd m~mbers, The dia~onals remain alwa~ flattened~ ~r additional advantage of this construction is that specially bend~resistant cro~-sections can be utiliæed~ In ordex to cor.nect the diagonal. membexs, threaded holes can be formed in ihe ~lalls of the chord me~bers~ .
The weakening of the chord members by holes which are formed in 1:he joint regic)ns can be avoided .

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when a plate coxresponding to the ~lattened end porticns of the diagonal mernbers is utllized .in tne regions o joints. This plate is welded to the chord member and extendsoutwaxaly thexe beyond, on each sicle, ~hexeas the end portions of ~he diagorlal mernbers are connected to sections of 'che plate. ext~nding outw~rdly beyond the chord memher.
~ n the fr~ne~ork cons~ruction, in accordance with the present irlvention, it is advantayeous when the diagonal members extend at an angle to the horizontal, which is smaller than 45, adv~ntageously smaller than 40, and has a prPerred range, for example be~ween 30~ and 40. In this way the eccentricity in the joints can be reduced to a minimal amountO
In order to completely elimina~e eccentricities, it i5 possible, in accordance with a further embodiment of the invention, ko provide between the flattened end of the mernbers a box shaped joint, which is 50 dimensioned that the axes of the diagonal members intersect the axes of the ch3rd melllbars so that no torque is generated~ The j oint ~ in accordance with the present invention~allows ~n especially rational mo~l~ing, n~nel~ a separa~e mountlng ~ the diagon~l membPrs and the chord members~ ~inally, in somP cases it is especially ad~antageous when the joint is composed of two cooperating parts, o~ wnich one par-l_ is connected lo -~he end portion of the chord memb~-r ~nd the otller part is cc)nnected ~o the end portion of the dia~c)nal rnembe3~

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r E ~-r n o the Drawin~.

For a ~uller understanding of the nature and objects of ~he invention, ref2rence should be had to the ollowing detailed description, taken in connection with the accompanying drawings, in which:
Fig. 1 is 2 longitudinal section of an end p~rtion o~ a ~ember of the framewoxk structure, according to the present invention, Fig~ 2 is an elevation view showing a portion of the framework structure, Fig. 3 is an elevation view of a chord mamber and a joint~
. Fig~ 4 is a plan view of a joint, FigO 5 is an elevation view showing an alternata fxa~ework structure, and ap~ears on the same sheet as Fig.1, : Figs,6a:through 6f are vaxious prererred cross-section~
o the chord members, Fig. 7 is a speciallycon.structed c~oss-section of a chord memberg ~ Fi~. 8a is a perspec~i~e ~iew of a cho~d member ;~ speciall~ arxanged for being connected to the diagonal members 7 Fig~ 8b i~ an. alternate version of a chord member specially arxa~ged for being connected to diagonal members, ,~ .
Fig~ 9 is an exploded perspective ~iew of a join~ and Fig~ 10 is an exploded perspect.ive view of a two-part jointO

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De~cx ~ E~bocliments Referring no~ to the drawi.ngs, and as can ~e seen from F~g. 1, a chord meluber ox a diagonal member ha5 circulax cxos~-~ec~ion3 and an end portiorl 2 which is ~lattened in a plane 1~ The end portions o the meInbers are connected with one another in jolnts as can be seen from Fig. 3, with the.aid o~ screws 10 which extend through openings, 6 ~o as to connect the members with one another and lo foxm the entire ramework structure. The through~gPing chord members may be flatt ned in an analogous manner without being divided ~t the xespective locations fGr connection to the dLagonal members. The constxuction shown in Fig. ~ may include a spe~.ial joint with the end portions of four chord members and four diagonal members~ .One end porti.on ~ay be inserted into another e~d poxtion~ as shot~n for two chord members 5 and 5' in the drawing. Thus, the thickness of the joint may be equal up to 16 times the wall thicknesses of the members. Thus a rigid connection region capable of being highly loaded is obtained~ The only weakened re~3ion of the mem~bers is disposed in the constric~ion region where the axial lines oE foxce change direction.
In accordance witl1 the inventlon due to the s~aight-line 7 plane sur~ace 8a and 8b of an intexmediat~ re~ion fo~minc~ a wedge and su~tending an anc~le ~rom hetween 20 and ~-, the constriction ` - L U ~-7~

region 8 has ~n optimum resistance to buckling and bendi.ng s~rength~ ~ts s~atic streng~h i~ higher by 6~.~
compared to ~hat of a constri~tion sh~ped in accordance with a naturally bulging profile, or cross-section~
The cons~riction xe~ion 8 can be for~ed hy a compression of the tubular e~d portions of the memb~'rs between t~o ~rapezoidal~shaped die parts~ The width of the sur~aces ~a ~nd ~b increases with the de~rease o~ the distance therebet~een, so that the be~ding s~rer,gth o the constxlcted region in the plane 1 extendin~
to the ~lattened end portions 2,~ lS consi.derably increased~
The chord me~bers 5 ar~ co~mected to one another in joint 4, as shown in part-section in Fig. 2, and are ~rr~nged in a horizontal position. Neighboring ~hord members are connected by the diagonal members 7. ~he ~lattened end portions of the diagonal members 7 are 50 angled that they extend parallel to the .respective end portions of the chord members and abut th~éagainst..
Xn the example shown in Fig. 3, the point of inte~section of the cixes 3 of th~ diagonal ~ember 7 forms an eccentricity "e" (deviation from the ; .
vertical plane~ relativ~ to the axis 1 of the chord membex. Thi5 eccentricity can be avoided in the event of hori~ontal arxan~ement of the screw~ 10 shown in The chord member 5 " showrl in l?ig . 4 has a rectangular cross-section and possesses the advantage that the j oint re~ion does not need any flattening 50 that no wea'~enillg of the bending stl-er,~;:h ~ 1..
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tak~ place~ Rotation o~ the (non-illu~trated) ends of the diagonal member 7 isl Lhe clirection o~ the arrow 9 is oFposed by the increased b,~nding strength of the constriction region which pro~iides increased resi~tance~
: The framewor.~ st:ructure shown in Fig~ 5 ha~ a plurality of joints ll wi.-th horizontal screw c~xe~
and a chord member S" o a rectangular cross secticn~
Figs. 6a-6~ ~;how- possible cxoss sections of chord ~nembers whic~h are especially advan~ageous for the realizati.on o~ the distinctive features of the presPnt invent:ionO ~he cross-~actions ~ay b~ square, rectangular, txapezoidally-shaped, ; C-sha~ed, double T-shaped, or Omega-shaped.
- i ~ - Fig. 7 shows chord member 13 with a :
trape~oidally-shaped- cross-section. The flatt~ned poxti~ns of ~he diagonal member 7 do not, in this -case, have to be angled ~or mounting on the inclined surfaces of the chord membex 13. The inclined surfaces subtend an angl~ with the horizontal, whîch is ~qual ~o appro~imately 45, The diagonal me~ber 7 is, however,-spatially inclined, that is, it is not located in a plane normal to the axis of the chord memberD Thus, the angle ~hich it subtends wi~h the hori~ontal is smaller than 45, and ranges in some cases between 30 and 40~
The chord member 5" shown in ~ig. 8a is provided with a rectangular plate 12, whereas the chord member 5ll in Fig. 8b is provided ~Yith a square plate 12~. The plates are welded ~o the respective chord members and serve for connecting the fla~tened end po~ions of the diagonal ne~bers. This construction is especially advantageous when a chord membex is utilized whose edge length is smaller than the diagonaL
o the flattened end portion of the dia~onal member.
This construction also has the advantage ~hat the chord member is not weakened, or weakened only to a ~mall extend by openings for screw5 being p~ovided therein~
Fi~. 9 shows a joint 14 composed of a chord p~ate 15 and diagonal plate 16 which are welded to on~ another by ~our angled bars 170 The joint 14 is ar~anged bet~een the 1attened end portion 2 of the chord member 5 and the flattened end portion o~ the diagonal member 7, and is screwed to both of these end portions. Instead of the angled bars 17, other spacer~
can be utilized, such as for example, bars or plates of diffexent respective cross-sections.
E'igD 10 shows a joint 18 which is composed of two separate parts 18a and 18b. The dia~onaI part l~a includes a circumferentially closed frame 19 having an opening closed by a {non-illustxaled) cover plater whi(~h is connected by screws to the fla~tened end portion of the diagonal mfmber 7. The chord part 18b includes a choxd plate 15' to which a spacer, for eYample, the angled piece 17, is welded. In the mounted condition r the ~rame 19 ~ ~ onto the anyled piece 17. The join~ i connection is es~ablished by scre~s ex,ending through the openings 6 . Nat~ ~ ally, t he connection Cdn a~o be ~-1J- ~

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reversed, namely the spacer can be connectec1 to the diagonal member ~nd the frame 19 can be connected to the chord member.
I wish it to be understood that I do not desire~ to be limited to the exact details of construct:on ~hown and described, for obvious modi~icatiotls will occur to a person s~illed in the axt.
Having thus described the inuention, what :~ claimas new and desire to be secured by Lettexs P~ten~:, is as follows:

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Claims

CLAIMS.

1. A framework structure, comprising in combination, a plurality of chord members, and a plurality of diagonal members, each of said members having a tubular portion, a portion flattened in a substantially pre-determined plane, and an intermediate portion between said tubular portion and said flattened portion, said flattened portions of said members being superimposed on, and connected to one another so as to form a plurality of joints, respectively, each of said intermediate portions substantially linearly narrowing from the tubular portion to the flattened portion of the same member in a wedge-like manner as viewed in a longitudinal section normal to said plane, and subtending an angle of 15° to 35° therebetween, the perimeter dimension of the axial cross-section of each member being substantially constant over the entire length thereof.

2. A framework structure as defined in claim 1, wherein said diagonal members extended in three dimensions.

3. A framework structure as defined in claim 2, wherein said diagonal members extend in a pyramidal manner.

4. A framework structure as defined in claim 1, wherein said angle ranges between 20° to 28°

5. The framework structure as defined in claim 1, wherein the planes of said flattened portions extend in a first direction, the flattened portions of said chord members being adapted to be connected to the flattened portions of said diagonal members by fastening means extending in a direction substantially at right angles to said first direction.

6. A framework structure as defined in claim 1, wherein each chord member has a polygonal cross-section remaining unchanged in the region of a corresponding of said joints.

7. A framework structure as defined in claim 6, wherein each chord member has a square cross-section.

8. A framework structure as defined in claim 1, further comprising at least one plate located in the region of each joint connected to the corresponding chord member, so that the sections of said plate extend outwardly beyond each side of the corresponding chord member, each of said diagonal members being connected to the outwardly extending sections of said plate.

9. A framework structure as defined in claim 8, wherein said plate is welded to said chord members.

10. A framework structure as defined in claim 1, wherein each of said chord members has a trapezoidally-shaped cross-section with an inclined surface adapted to be positioned so as to subtend an angle of substantially 45° with the horizontal.

11. A framework structure as defined in claim 1, wherein each of said diagonal members is adapted to be positioned so as to subtend an angle with the horizontal smaller than 45°.

12. A framework structure as defined in claim 11, wherein each of said diagonal members is adapted to be positioned so as to subtend an angle with the horizontal smaller than 40°.

13. A framework structure as defined in claim 12, wherein each of said diagonal members is adapted to be positioned so as to subtend an angle with the horizontal ranging between 30° and 40°.

14. A framework structure as defined in claim 1, wherein each of said joints is located between the flattened portion of one chord member and the flattened portions of respective diagonal members, so that the axis of said one chord member and the axes of said diagonal members substantially intersect.

15. A framework structure as defined in claim 14, wherein said joints are box-shaped.

16. A framework structure as defined in claim 14, wherein each of said joints is composed of two parts, one of said parts being connected to one chord member, the other of said parts being connected to corresponding diagonal members.