US1651032A - Structural unit - Google Patents

Description

Fig.1.

Nov. 29, 1927.

- 1,651,032 S. MACOMBER STRUCTURAL UNIT Filed June 2, 1923 INVENTOR.

' 13 zazziqy fzecamez I particular type of structural element.-

Patented" N 0v. 29, 1927.

UNITED STATES 1,651,032 PATENT OFFICE.

' STANLEY mncomnna, or MASSILLQN, 01110, ASSIGNOR To THE mncomn'nn STEEL COMPANY, or oANToN, OHIO, A CORPORATION or 0310.

sTRUcTUnAn UNIT.

Application filed June 2,

My present invention relates more particularly to the construction ,of a truss sectionor other structural unit for buildings and the like, where such unit-is fabricated from a plurality of bar or rod-like elements.

, "One important object of the invention is the provision of a light truss-like structure adapted for use instead of beams in carrying light loads as'in the case. of joists in floors and the like, but the utility of the invention is not limited to any such particular field or for that matter to any such 3 improved unit, in other words, may also be advantageously employed as a column, as a roof purlin and as a reinforcement forconcrete floors, etc. A further object is the provision of a structural unit of the. type in question wherein end members are provided having continuous supporting surfaces'in order to secure flexibility, or in other words permit variation in the span lengths for which any particular truss can be used. Still another object is to provide in such a structural unit for a variation in the span length, or in other words an extension of the normal length of the span using the same elements and thus avoiding additionalcost.

' required.

. in the manufacture ofthe truss.

' sections of the members. As a result for any given truss the supports must be located a definite distance apart and conversely for a given location of supports a definite design and length of truss must be used.

It is likewise Well known that a truss is ,a very efficient form of structure for the support of transverse loads due to the fact that the structural members of the truss are subjected only to pure tension and compression and by proper design each member can be exactly proportioned for "the stress to which it is subjected so that every part of the structure willzbe subjected-to substantially uniform stress of the maximum desired magnitude. Ascompared to this in the case of a beam subjected to transverse loads the maximum stresses vary at every section from a maximum at the polnt of maximum bending fabricate a standard line of trusses which oints of- 1e23. Serial No. e42 ,9a5.

moment, commonly midway between supports, to zero at the supports themselves while for every section the stresses vary from a small magnitude at the neutral axis to the maximum at the outermost fibres. As a result, the metal re uired to make a beam of same length and epth as a truss, each capable of, supporting the same loads, is verymuch greater than that required for the truss. Notwithstanding the great economy 'of material resulting from the use of trusses it has been the almost universal practice in the past to use beams in building construction for the support of floors, etc.

commercially impracticable to. design and 'w'ould'be capable of use in ordinary building construction as ordinary wood or steel beams are used which can be cut to the exact length It is the object of my invention to produce a truss which will have all the advantages as to the economy of metal inherent in this type, of structure and at the same time not be subject to the above objections and as a result. make itpossible to design a line of standard trusses consisting of comparatively few sizes which will provide'in their entirety for the. points of support being located any distance apart from'a desired minimum to a des redmaximum and thus meet the requirements of ordinary building construction.-

.To the accomplishment of the foregoing and related ends, the invention, then, con-I sists of the means hereinafter fully described and particularly pointed out in the claims,

the annexeddrawing and the following description setting forth in detail certain mech anism. embodying the invention, such dis-i closed means constituting, however, but one of various mechanical forms in. which the principle of the invention may be used.

' 1 but showing one end of a truss-like structural unit of modified construction; Figs. 8, 9 and 10 are transverse sections corresponding to the section of Fig. 5 but illustrating various modified constructions; and

Fig. 11 is a diagram showing the forces acting on the beam extension and the end joints of the truss.

Referring first to Fig. 11, the truss is shown diagrammatically with an upper ehordl and lower chord 2, with diagonals 3, these various members being joined together in any suitable or well known manner at their points of intersection or joints. At the left hand end of the truss there is shown diagrammatically a beam 10, of any suitable cross sectional shape, connected in any suitable or well known manner, to the truss at the joints 15 and 16. The beam 10 extends beyond the end of the truss any desirable distance and furnishes a means of support for the whole structure such that the actual point of support may be located at any place along the beam. Assume for the purpose of illustration that the support is located under the beam at the point of the arrow B and that the truss is subjected to various loads which can for the purpose of analysis be represented by certain forces 1 1 etc., applied to the joints which loads and the weight of the truss itself cause a reaction of the support against the beam which can be the top and bottom which bottom flange at represented in direction and magnitude by the arrow B. As is easily shown, the conditions of equilibrium of beam 10 require that forces R, and R, be applied to the beam 10 at joints 15 and 16 by the truss. Or it may be considered that the beam 10 exerts the forces r, and '1', on the joints 15 and 16 of the truss. It is thus seen that the only effect on the truss of placing the point of support of the whole structure beyond the last joint ofthe truss is to increase the loads upon certain joints of the truss and hence the stresses in the truss members. This is not obj ectionable as an'increase in stresses would also occur if the truss itself had been extended to reach this same point of support.

the same time provides a continuous surface, any portion of which may be used to rest upon the supporting wall or girder. Any

portion of the beam 10 projecting beyond I the supporting ,wall or girder performs no useful function in connection with sustain- I nected to only two joints which keeps the stresses separate and distinct and of the desired type in each portion of the structure.

-From the foregoing it is clear that by the use of my invention it is possible'to construct a structural unit especially adapted to support transverse loads in which the portion subjected to large bending moments may be constructed of jointed elements thus subjecting these elements to substantially pure tensile or compressive stresses of maximum desired magnitude, whereas the portions where the bending moments are comparatively small may be constructed of elements subjected, to simple bending stresses which elements provide continuous surfaces, any portions of which may be used as points of support for the whole structure, thus combining in one and the same structure substantially maximum efficiency in use of metal resulting Theforces R,7R, and R acting uponthe.

"throughout their ma or extent but having beam 10 set u bending moments at every section of the eam,exeeptt hat part to the in minimum weight, and substantially. all the advantages inherent in a beam, i. e. adjustability of length of span due to con-' tinuous supporting surface presented by a beam. Y Referring first of all to the form of structural unit illustrated in Figs. 1 to 6, inclusive, it will be noted that the truss there shown is made up of five principal elements or pieces, viz, .twostraight bars or rods 1 that compose the upper chord; two similar bars or rodsv 2 that compose the bottom chord, such last mentioned bars or rods being straight their ends bent up to form angularly related several bars are electrically welded or otherwise permanently and rigidly secured together at the points where the angles 3* of the web member. 3 thus lie between paired bars 1 and paired bars 2. However, because of the simplicity of the operation, it is preferred to mash-weld together the bars at the points in question, the middle bar being placed in position between the top and bottom bars, as shown inthe sectional views, Figs. 3 to 6, inclusive, and the severaLwelds bein either successively orsimult-aneously pro uced.

' For the purpose of developing enough strength in the truss end, when resting on the support therefor provided, to carry the load of the truss, special attention has been paid to the design of such end portion of the unit. As already described, the terminal portions 2 of the lower chord members 2 are brought into parallel, more or less closely contiguous relation to the corresponding portions of the upper chord members 1. Such end portions of the respective chord members are then firmly and permanently secured together by means of two reinforcement plates 5 which extend inwardly between the upper chord members for a short distance beyond the portions thus lying adjacent portions 2 of the lower chord members and which are formed with laterallyprojecting flanges 5 that underlie such chord portions 2". The section of the two plates as thus opposed together in the end portion of the finished unit (see Fig. 3) is substantially that ofan inverted T, it being understood that all the elements entering into the structure at this point, as elsewhere, are suitably welded together at spaced points of contact, if not continuously, so as to insure rigidity and secure maximum strength.

' The depth of the plates 5 relatively to the depth of the truss as a whole, where such plates extend inwardly beyond the end proper of the unit, may of course vary, but as indlcated in Figs. 4. and 5, they may extend downwardly approximately one-third of thetotal vertical extent of the truss and they are preferably carried inwardly to at least the first upwardly bent angle 3 of the web member 3. j

I, In this particular embodiment of the invention theiruss member 2 does not make an actual joint with the truss member 1 but both members are rigidly joined to the plates '5 at closely adjacent points and for practical purposes act as if .directly joined to each other. The plates 5. are preferably joined continuously tothe extensions beyond the point 15 of the truss elements 1 and 2, thus forming a pure beam of ,this portion of the structure. The plates 5 may be joined continuously to the truss elements 1 to the right of the point 15 ,(Fig. 11) thus forming a composite element which acts both as a simple tension or compression v,member of the truss and also as a beam to transfer the reac-- tion of the sup'port to joints of the truss or they may only be joined to the truss joint 16. A

. larly upwardly bent portions 2 of such chord members, Such projecting extremities 3 thus provided serve to extend across the angular space which will be left between a vertical wall, on which the ends of the truss rest, and such inclined portions 2 of the bottom'chords and the ceiling lath may be fastened to such extremities and thereby be carried directly across to such wall.

The length of these extremities will be made such as to cover the maximum distance which may be left, and if necessary the rods composing such extremity may be cut back to terminate thus flush with the wall.

As shown in Fig. 7, the inclined portions 2 of the bottom chord members need not be bent upwardly at the same angle as that observed informing the successiveangular portions of web member 3, as is the case in the form of truss shown in Figs. 1 and 2, but maylie at a more obtuse angle,-thus correspondingly shortening the horizontally extending portions 2 of such chord members that enter directly into the ends of the completed truss. This allows a longer end piece on the truss, bracesthe latter against bending and allows further extension of the span ing the truss, since the overall length of the rods used in fashioning such bottom chord members will be substantially, if not identically, the same in both designs. The other features of the modified construction of truss shown in Fig. 7 remain unchanged and so require no special description except to note that here the end reinforcement is comprised of'a single plate 5 having oppositely disposed horizontal flanges forming an inverted T.

While, as indicated, I preferably employ rods or bars which may be either round or square for the top and bottom chord members 1 and 2, other forms of material may be utilized. Thus, as shown in Fig. 8, the

top chord members 6 are in the form of angle bars, one flange of each being disposed vertically and lying against the respective sides of the web member?)- with the other.

flanges extending horizontally. In this construction it may be unnecessary to employ plates such as plate .5 in order to necessary rigidity to the ends of the .unit. In Fig. 9 I show the use of an inverted chan- As hereinbefore indicated, articular importance is attached to the deslgn of the ends of the unit, these being beams adapted to carry the'stresses into the center of the truss and at the same time takin care of the. excess bending moments. At t e same time a flexibility in the length of span, for which any particular truss can be used, is secured thus adapting my improved unit for more universal use than in the case'of units which i require to be designed specifically for a given span. Finally, it will be noted that all of the elements enteringinto the construction of my improved truss unit are stock shapes, whether rods, bars or channels,

so that the manufacture of the unit is much simplified, very little special equipment being required, while the welding operation, whereby the units are secured together, may be carried out on welding machines of standard v design.

'the respective pairs of bars 1 and 2 forming the top and bottom chords, I secure a truss formation having anunusual amount oflateral rigidity.

While the specific form of my improved structural element will find a large field of use as a joist in floor construction, it will be obvious that it may equally well be employed as a column or as a reinforcement for a concrete floor or roof of familiar form where the unit will be Wholly embedded in concrete. It is also readily adaptable for use in an inclined position, instead of horizontally disposed, so as to serve asa roof purlin.

Other modes of applying the principle of any invention-may be employed instead-of the one explained, change being made as regards the mechanism herein dlselosed, proylded the means stated by any of the followmg claims or theequivalent of such stated means be employed.

I thereforeparticularly point out and distinctly claim as my invention 1. In a structural unit for sup orting transverse loads, the combination 0 a cen-,

tral portion designed and constructed as a v load-sustaining member taken by itself, and

beam portions extending beyond the ends of such central portion, each of said beam extensions affording a multiplicity of points of support for the whole unit and being tied into such central portion so as to adapt the unit as a whole to sustain a predetermined load irrespective of such points of support.

2. In a structural unit for supporting transverse loads, t-hecombination of a ccntral portion with extension beam end menr bers affording a multiplicity ofpoints of support whereby the effective span of the ,unit may be varied continuously from'that of such central portion itself to the total span of the whole unit, said central portion being designed and constructed as a loadsustaining member taken by itself and such extension members being tied into suchccntral portion so as to adapt the unit as a whole to sustain a predetermined load irrespective of such points of support.

3. In a structural unit for supporting transverse loads the combination of a major portion constructed of simple tension and compression members so'organized as to present but few relatively widely separated points adapted to withstand the support reactions and an extension member tied into such major portion so as to beadapted to withstand the support reaction at any point throughout the length of the extension.

4:. In a structural unit for supporting transverse loads, the combination of a major portion of simple tension and compression members so organized as to present but low relatively Widely separated points adapted to withstand the support reactions and an.

extension member having a continuous surface throughout the length of the extension, said extension being tied into such major portion so as to adapt any portion of theextension to withstand the support reaction.

5. In a structural unit for supporting transverse loads, the combination of a central truss portion with extension beam end portions attached to the truss at its joints only, said end portions having continuous supporting surfaces beyond the ends of the truss.

6. Ina structural unit for supporting transverse-loads, the combination of a central truss portionand extension beam end portions, each of said end portions being connected to the truss at its respective end joint and at least one other joint and provided with continuous supporting surfaces.

beyond the ends of the truss. v 7. In a truss-like structuralyunit, the

- combination of top and bottom chord-men'i- 'bers, and a suitable web-member, said chordmembers .havlng ad acent ends'formed nto a remforced. extension for said u'mt, the reinforce'me'nt in such extension being carriedthence inwardly to a point where said webglemberis attached to the top chord-menr er. j j v 8. In a truss-like structural unit, the combination of top and bottom chord-members,

a suitable web-member, saidchord-members spaced relation throughout the major portion of their length and having their ends brought into relatively close proximity, such en'ds being likewise substantially parallel with each other and fixedly secured together to form extensions for said unit and rein forcing members in such extensions respectively, each such reinforcing member being carried inwardly to a point where said web member is attached to the top chord-member,

9. In a truss-like structural unit, the combination of top and bottom chord-members,

a suitable web-member, said chord-members relatively close proximity, such ends being likewise substantially parallel with each other and firmly secured together to form extensions for'said unit, and vertical reinforcement plates incorporated in such extensions, each such reinforcement plate being carried inwardly to a point where said webmember is attac ed to the top chord-member;

10. In a truss-like structural unit, the combination of two parallel rods forming top chord-members, two other rods spaced from but lying. parallel with said firstnamed rods throughout the major portion of their length. said last-named rods forming bottom chord-members and having their ends bent upwardly and then into parallel closely proximate relation to the correspondin ends ofsaid topschord-members, andv a suitable web-member connecting said top and bottom chord-members.

11.. In a truss-like structural unit, the combination of two parallel rods forming top chord-members, two other rods spaced from but lying parallel with said first-named rods throughout the major portion of their length, said last-named rods forming bottom chord-members and having their ends bent upwardly and then into parallel closely proximate relation to the 1 corresponding ends of said top chord-members, and still another rod bent to form a series of oppo-.

sitely directed) angles, the latter being secured to said top and bottom chord-members, respectively, and thereby constituting a web-member of said rod. I

12. In a truss-like structural unit, the combination of two parallel rodsiorming top chord-members, two other rods spaced from but lying parallel with said first-named rods length, said last-n proximate relation throughout the major portion of their arsed rods forming bottom having their ends bent into parallel closely to the corresponding ends of said top chord-members, and still chord-members upwardly and o another rod bent to torm a series of oppo-, I sitely directed angles the latter being secured to said top and bottom chord-memunit, the com- .bination of two parallel rods forming top chord-members, two other rods spaced from but lying parallel with said first-named rods throughout the major portion of their length, said last-named rods forming bottom chord-members and having their ends bent upwardly and then into parallel closely proximate relation to the corresponding ends of said top chord-members, still another rod bent to form a seriesv of oppositely directed angles, the latter being secured to said top and bottom chord-members, respectively, and thereby constituting a web-member of said rod, and vertical stiffening plates in the extensions formed by such end-portions of the chord-members.

14. In a truss-like structural unit, the'combination of two parallel rods forming top chord-members, two other rods spaced from but lying parallel with said first-named rods throughout the major ortion of their length, said last-named ro s forming bottom chord-members and having their ends bent upwardly and then i into parallel closely proximate relation to the corresponding ends of said top chord-members, still another rod bent to form a series of oppositely directed angles, the latter being secured to said top and bottom chord-members, respectively, and thereby constituting a web-member of said rod, and vertical stifi'ening plates in the extensions formed by such endportions of the chord-members, said plates being carried inwardly past the first upwardly directed angle of said web-member. I

15. In a truss-like structural unit, the combination of two parallel rods forming top chord-members, two other rods spaced from but lying parallel with said first-named rods throughout the major port1on oftheir length, said last-named rods forming bottom chord-members and having their ends bent upwardly and then into parallel closely proximaterelation to the corresponding ends 0 said top chord-members, still another rod v bent, to form a series of oppositely directed angles, the latter being secured to said top and bottom chord-members, respectively,

,lying beneath the portions of said chordmembers composing such extensions.

16.111 a. structural unit for supporting transverse loads, the combination of a cenasa load-sustaining member taken by itself,

andflbeam portions extending beyond the ends of such central. truss said beam extensions affording a multiplicity of points of support for the whole unit and being tied into such central truss portion so as to adapt the unit as a whole to sustain a predetermined load irrespective of such points of support.

17 In a structural unit for supporting transverse loads, the combination of a central truss portion'with extension beam end members affording a multiplicity of points of support whereby the effective span of the unit may be varied continuously from that of such central truss portion itself to the total span of the whole unit, said central truss portion being designed and constructed as a load-sustaining member taken by itself, and such extension members being tied into such central truss portion so as to adapt the unit as a whole to sustain a predetermined load irrespective of such points of support.

18. In a truss-like structural unit, the.combination of top and bottom chord-members, and a continuous, reversely bent web-member, said members forming a central loadsustaining'unit portion, andbeam end extensions for said central portion afiording a multiplicity of pointsof support, said extensions being connected to said central portion so as to adapt the unit as a whole to sustain a predetermined load irrespective of such points of support.

19. In a truss-like structural unit, the. combination of top and bottom chord-members, and a suitable web-member, said chord-members having adjacent ends formed into a reinforced extension for said unit, the re- I inforcement in such extension being carried thence inwardly to a point Where said web: member is attached to a-chord-member.

20. In a truss-like structural unit, the combination of top and bottom chord-members, a suitable web-member, said chord-members being disposed in substantially parallel relation throughout. the major portion of their length and having their ends brought into relatively close proximity, such ends being firmly secured together" and forming extensions for said unit, and vertical reinforcement plates incorporated in such extensions, said plates being formed with laterally proectm flanges engaging the ends of said bottom c ord-member, each of said plates being carrled lnwardly to a point'where said webmember is attached to a chord-member.

'21. In a truss-like structural, unit, the combination of two parallel rods forming topchord-members, two other ro ds spaced from but lying parallel with said first-named rods throug out the major portion of their length, said last-named rods forming bottom chord-members and having their ends bent portion, each of.

upwardly and then into closely proximate relation to the corresponding ends of said top chord-members, a suitable web-member connecting said top and bottom chord-me bers, and means securing together -the respective closely proximate chord ends.

22. In a truss-like structural unit, the combination" of two parallel rods forming top chord-members, two other rods spaced from but lying parallel with said first-named rods throughout-the major portion of their.

length, said last-named rods forming bottom chord-members and having their ends bent upwardly and then into closely proximate relation to the corresponding ends of said top chord-members, means integrated with said closely proximate chord ends to form unit-end bearing portions having a multiplicity of points of support, and a suitable web-member connecting-said top and bottom chord-members.

23. In a truss-like structural unit, the combination of two parallel rods forming top chord-members, two otherrods spaced from but lying parallel with said first-named rods throughout the major portion of their length, said last-named rods forming bottom,

chord-members and having their ends bent upwardly and then into closely proximate relation to the corresponding ends of said top chord-members, a suitable web-member connecting said major portions of the top and bottom chord-members, and means integrated with said closely proximate chordends to form unit-end bearing portions having a multiplicity of points of support, said rods. spaced from but lying parallel with.

said first-named rods throughout the major portion of their length and forming bottom integrated means at each unit-end being carchord-members, said last-named rods having their ends bent upwardly and then into closely proximate relation to the corresponding ends of said top chord-members, and a reversely bent web-member connecting said top and bottom chord-members, the angles of said web-member being secured to said.

chord-members in the spaces between the respective pairs of rods.

25. In a truss-like structural unit, the combination of two parallel spaced rods forming top chord-members, two other parallel spaced. rods spaced .from but'lying parallel with; said first-named rods throughout themajor;

portion of their length and forming bottom chord-members, said last-named rods having their ends bent upwardly and then into closely dproximate relation to the correspond mg en continuous, reversely bent web-member cons of said top chord-members, and a their ends bent upwardly and then into closely proximate relation to the corresponding ends of said top chord-members and firmly secured relatively thereto, and a re 1 versely bent web-member connecting said top and bottom chord-members, the angles of said Web-member being secured to said chord-members in the spaces between the respective pairs of rods.

Signed by me, this 29th day of May, 1923.

STANLEY MACOMBER.

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