US1983874A - Bar structural truss - Google Patents

Description

Dec. 11, 1934. w M PRATT 1,983,874

BAR STRUCTURAL TRUSS Filed July 18. 1950 2 SheetS-Sheet l INVENTOR ATTORNEY Dec. 11, 1934. w. M. PRATT 1,983,874

. BAR STRUCTURAL TRUSS Filed July 18, 1930 2 Sheets-Sheet 2 A .1\ A S\ Patented Dec. 11, 1934 1 .47

UNlTD STATES PATENT OFFICE BAR STRUCTURAL TRUSS Walter M. Pratt, Detroit, Mich. Application July .18, 1930, Serial No. 468,835 Claims. (Cl. 108-23) This invention relates to structural trusses, line 3-3 of Fig. l, and showing how the wooden and particularly to trusses of the joist or steel strips are bolted to the metallic, paired, chordbar type. forming bars.

An object of the invention is to adapt nailer Fig. 4 is a vertical cross section, taken on 5 strips to be so secured to either the top or bottom the line 4-4 of Fig. 1, and disclosing primarily 5' chord of a steel bar truss (or to both), in such details of the end connection between the chords, a manner as to become actual elements of said and provisions for seating the truss and resistchords, increasing their load capacities, as well ing end thrusts. as permitting the nailing of wooden joists, roof- Fig. 5 is a fragmentary top plan view of an ing, or flooring to said chords. end portion of the truss. 10 Another object is to rigidly connect the top Fig. 6 is a side elevational view of the imand bottom chords of a steel bar truss by verproved truss, in a modified form.

tical (or other) webbing members and allow the Fig. 7 is a typical vertical cross section through latter to terminally project sufficiently beyond a truss, further modified as regards the provision one or both of said chords to embed themselves for rendering thenailing strips actual parts of in wooden nailing strips subsequently applied to the chords.

said chords, and drawn into firm contact with Fig. 8 isa fragmentary horizontal section,

said metal chord members by bolts or the like, taken upon the line 8-8 of Fig. 7.

whereby the nailing strips become an actual Fig. 9 is a fragmentary elevational view of element (or elements) of the chord (or'chords), an end portion o a truss f t e type shown in 20' increasing the load capacities. Fig. 6, but somewhat modified as regards the A further object is to form the top or bottom provision for mounting it upon an abutment wall. chord (or both) of a steel bar truss of two or In these views, the reference character 1 desmore spaced steel bars of standard form and to ignates a pair (or more) of para1lel,'slightly sepjointly engage said bars by an elongated nailing arated, standard steel bars arched preferably 25' strip of wood or other suitable material, utilizing parabolically to form top chord elements of a the space between said bars to receive bolts, setruss. The bottom chordof said truss comprises curely clamping the strip to said bars. a pair or more of spaced parallel standard steel Still another object is to extend vertical webbars 2, which, as illustrated, are rectilinear, but

" bing bars between the top and bottom chords may in some instances be cambered, or otherwise 30'- of a steel bar truss, engaging their ends between varied from the form shown. Suitably spaced two bars spaced to form each ofsaid chords, lengthwise of the truss is a series of upright and to rigidly engage said vertical bars by a series webbing bars 3, the end portions of which engage of diagonal bars extending substantially from between and are welde'd'to the paired bars 1 end to end of the truss and arrangedalternately and 2, as best appears in Fig. 2. The uprights 351 at opposite sides of said verticals, whereby the 3 terminally project a short distance above and joint effect of said diagonals is substantially the below the bars land 2 and are formed with same as if they'were located in the central lonbeveled end faces 4 to adapt said end portions gitudinal plane of the truss. to more readily embed themselves in wooden A Still further Object i5 to provide an i p chord members 5 and 6, the former superposed 40 mea s for rigidly Connecting thetop and tto upon and arcuately conforming to the bars 1, chords of a steel bar truss, at their ends and for d th 1 tt engaging t under faces of the seating the truss'ends on suitable abutments. bars 2, throughout the length thereof.

These and various other objects the invention At suitable points between the uprights 3, the

attains by the construction hereinafter described, wooden chord members 5 and 6 are clamped to and ill s rat n the mp nyi win the chord bars 1 and 2- by bolts 7, preferably wherein: extending between the bars 1 and between the Fi 1 is a s d elevation of t p v t u s. bars 2, their heads being countersunk in the P ly s l sing a superposed'roof structure. top and bottom faces-of the members 5 and 6 Fig. 2 is a vertical cross section of the same respectively, as best appears in Fig. 3, and their taken on the line 2-2 of Fig. 1, and Show shanks carrying nuts 8 engaging below and above how the vertical webbing bars are terminally embars 1 and 2 respectively. By means of said bedded in wooden nailing strips. nuts and bolts the described wooden chord mem- Fig. 3 is a vertical cross section, taken on the bersarev clamped firmly against the bars 1 and 55 2, and the beveled ends of the uprights 3 are made to bite into said chord members.

A second wooden chord member 9 may be superposed upon the chord member 5 and is so illustrated in Figs. 1-4, being attached to the chord member 5, as shown, by spikes 10 or other suitable fastenings at suitable intervals. The roof (or floor) 11 may be applied either directly to the wooden chord member 9 or may be laid on joists 12 carried by said chord member.

To complete the Webbing structure of the described joist, it is preferred to engage a series of acutely inclined diagonal bars 13 of standard form with the uprights 3, said series extending from end to end of the truss. Preferably said bars 13 are alternately placed against opposite side faces of the uprights 3, and are rigidly connected to said uprights, as by welding. In the illustrated construction, each diagonal at its mid portion crosses one of the uprights 3, and its welded connection thereto materially reinforces the said upright as well as the diagonal.

At each end of the truss a vertical plate 14 is engaged between the bars 1 and between the bars 2 and is welded to both bars of each pair. Preferably the top portion of said plate is extended some distance centrally into the correspondlng end portion of the wooden top chord 5. Welded to the plate 14 and to the bars 2 therebeneath is a horizontal steel seating plate 15, which transmits the truss load to a suitable abutment 16, and an end abutment plate 17 for the truss, arranged transversely of the latter and formed integral with the plate 15 is welded to the outer edge of the plate 14 and to the ends of the bars 1 and 2. The plate 17 extends sufficiently above the bars 1 to act as abutments for the ends of the wooden chord members 5 and 9, and is somewhat wider than said chord members so that its lateral edge portions may be embedded in masonry. Integral with the plate 15 and downwardly extending against the inner face of the abutment wall 16, is a plate 17a, bolted to said wall as indicated at 17b. This construction very positively transmits to the wall 16 any end thrust that may be applied to the plate 17, as well as securing anchoring the truss against any lateral shifting.

Adjacent to each end of the truss the top and bottom chords are connected bya bolt or bolts 18 extending between the bars 1 and between the bars 2 and welded to both bars of each pair. The head and one end of each of said bolts and a nut engaging their other ends are clamped respectively below and above the bars 2 and wooden member 5.

Preferably a bar 19, transverse to the truss, is welded to the bars 1 and plate 14 at each end of the truss and projects laterally at each side thereof. In this way, the member 19 serves both as a pin anchor and an abutting surface to receive some of the thrust from the member 5.

The junction of member 9 with the member 17 is at such an angle that any tendency to uplift the member 9 is restrained by the member 17, which thus performs a double duty.

In that modification of the invention illustrated in Fig. 6, the construction conforms to the preceding description except that the top chord bars 1a are straight, and the bottom chord bars 2a are parabolic, the same being true of the wooden top chord members 5a and the wooden bottom chord members 60.. In this construction,

moreover, only a single wooden top chord member is illustrated, but a series of such members might be used.

In the further modified construction of the truss illustrated in cross section in Fig. 7, the metal top chord elements 1b and metal bottom chord elements 2b correspond to those already described, as do likewise wooden top and bottom chord members 5b and 6b. In this construction, however, the webbing uprights 3b are for their major lengths of square cross section, their upper portions 20 being cylindrical and threaded end projecting through the top wooden members 527 and engaged above the latter by nuts 21. The open ngs of the members 527 accommodating the top portions of the uprights 3b are proportioned to freely receive the threaded end portions of said uprights, but are of lesser cross sectional area than the square main bodies of said uprights. A. welded connection between the top chord bars 11) and the uprights 5b is established slightly below the end portions of said uprights, so that under a clamping stress applied by the nuts 21, the wooden chord member 5b is adapted to be forced down against the top chord bars 11), causing the squared portions of the uprights to bite some distance into the wooden members 5?), as Fig. 7 illustrates.

The effect of firmly embedding projecting ends of the uprights 3 in the wooden members 5 and 6 is to establish a unity of action between said member and the metal bars 1 and 2, so that said Wooden member become actual components of the top and bottom chords, acting in unison with the latter in resisting such longitudinal shearing stresses as act in said chords when the truss is under a load. In the absence of the interlock established by said projecting ends, only an inadequate frictional force would questionably function to establish such unity of action. A very tight wedging fit of the uprights 3 into the members 5 and 6 is, of course, essential to the desired result, and such a fit is established by sinking the beveled ends of the upright into the wooden members under a clamping stress induced by the bolts and nuts 7 and 8. The total strength of each of the truss chords is greatly increased by thus bonding the wooden and metallic chord members together and the described connection adapts the composite chords to take either tensile, compressive or bending stresses with the same uniform action.

By the employment of parabolic chords to carry uniform loads, stresses in the diagonal webbing members 13 are practically eliminated. The location of said diagonals alternately on opposite sides of the uprights 3 neutralizes such tendency toward eccentric stresses as might otherwisearise, and produces the same condition as regards balancing of stresses as if all the webbing members (3 and 13) were in the same central vertical plane.

A desirable feature of the described truss is its capacity foruse either in the form shown in Fig. 1 or that shown in Fig. 6. Thus, by simply inverting the truss, it may be adapted to conveniently carry either a parabolic or a flat roof on its top chord, and either a fiat or parabolic ceiling on its bottom chord. In either of these constructions, the top chord is in compression and the bottom chord in tension.

While the top chord bars 1 have been illus-, trated as square, and the bottom chord bars 2 are cylindrical, it is to be understood that either round or square bars, or any other suitable cross sectional form, may be used for the bars 1, 2. 3 and 13.

It is also to be understood that the wooden chord members 5 and 6 may be applied to both top and bottom chords, as shown, or to only one thereof, and that one or more additional wooden members may be applied not only to the top chord, as has been indicated at 9, but the bottom chord also if desired.

The described end connection between the top and bottom chords established by the plates 14, 15 and 16 very securely connects the top and bottom metallic chord bars, as well as providing a firm seat for the truss ends and a rigid abutment for both the metallic and wooden elements of the two chords.

The preferred rigid connection between the uprights 3 and bars 1 and 2 is established by welding, the same being true of the connections between the diagonals 13 and the uprights 3, and the connections between the plates 14, 15 and 17.

While the members 5, 6 and 9 are preferably wooden, some other material, softer than the bars 1 and 2 might be substituted.

While it is apparent that the illustrated embodiment of my invention is well calculated to adequately fulfill the objects and advantages primarily stated, it is to be understood that the invention is susceptible to variation, modification and change within the spirit and scope of the subjoined claims.

What I claim is:

1. In a structural truss, metallic top and bottom chord members extending substantially from end to end of the truss, a plurality of metal bars rigidly connecting said metallic chord members and having end portions projecting beyond one thereof, a third chord member of softer material and of a shape offering greater resistance to lateral buckling than the last-mentioned metallic chord member, engaging that face thereof from which said metal bars project, and means clamping the wooden chord member firmly against its companion metallic chord member, whereby the projecting portions of said metal bars are sunk into the third chord member to unify the latter with the engaged metallic chord member in meeting stresses acting longitudinally or transversely thereof.

2. A structural truss as set forth in claim 1, said projecting end portions of the metal bars having their end faces beveled to adapt them to more readily penetrate the third chord member.

3. In a structural truss, a pair of spaced, parallel, metallic top chord members, a pair of spaced, parallel, metallic bottom chord members, means rigidly connecting said chord members at their corresponding ends, a third chord member substantially coextensive with and of softer material than one of said pairs of metallic chord members and bridging the faces of the latter remote from the other pair, a plurality of metal webbing bars rigidly connecting the top and bottom metallic chord members and engaging between the paired members of each thereof and projecting beyond one of said pairs to form bonding elements tightly inserted in the third chord member, and means clamping the third chord member firmly against the metallic chord members which it bridges, and establishing the specified tight insertion of the bonding element in said third chord member.

4. A composite chord for structural truss purposes comprising a pair of spaced, substantially parallel, metal bars extending lengthwise of the chord, a wooden chord member extending lengthwise of the chord and superposed on said metal bars, and fasteners connecting said metal bars and wooden chord member, spaced longitudinally of the chord, passing through said wooden member and between said metal bars and abutting the under faces of both of said bars.

5. In a structural truss, an arched top chord comprising separate upper and lower members substantially coextensive, a bottom chord establishing a tie between the ends of the top chord, a plurality of metal bars, spaced longitudinally of the truss, and rigidly connecting the bottom chordto the lower member of the top chord and their upper ends projecting above said lower member, and being embedded in the upper member of the top chord, and means securing the upper member of the top chord in engagement with the lower member thereof and in engagement with said projecting ends.

WALTER M. PRATT.

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