US1968096A - Roof truss - Google Patents

Description

W. M. PRATT J ly 31, 1934.

ROOF TRUSS Filed April 4, 1930 4- Sheets-Sheet l INVENTOR 'Wkli'er M Pr??? v fiTTORNEY July 31, 1934.

W. M. PRATT ROOF TRUSS Filed April 4, 1930 4 Sheets-Sheet '2 July 31,1934.

w. M. PRATT ROOF TRUSS Fild April 4, 1950 4 Sheets-Sheet 4 Patented July 31 1934 I UNITED STATES PATENT OFF-ICE R F TRUSS Walter M. Pratt, Detroit, Mich. Application April 4,1930, Serial No. 441,534

Q 4 Claims. (01. 1os-2s) This invention relates to building trusses such shown in Fig. '7, the section being taken upon the as are employed primarily in supporting roofs line 7a7a of Fig.7; and bridge spans, and particularly relates to Fig. 8 is a fragmentary, side elevation of a building trusses having arched top chords. central upper portionof the truss of Fig. 7.

An object of the invention is to provide a truss Fig. 9 is a cross section taken upon the line 99 comprising an arched top chord, a bottom chord, of Fig. 8, and disclosing the use of splice plates and brace members extending from the truss to rigidly connect abutting halves of the top extremities to the central portion of the top chord, chord. and to .provide a system of bracing between said Fig. 10 is a fragmentary, side elevational view '10. brace members and top chord, giving the effect of of a similar joint established between abutting two truss members meeting centrally of the truss halves of the lower chord. and each comprising one-half of the top chord. Fig. 11 is a cross section upon the line 11-11 Another object is to form the arched top chord of Fig. 10. of a truss from a plurality of standard steel beams Fig. 12 is a fragmentary, elevational view of an 15. individually bent to the proper curvature and subend portion of the truss illustrated in Figs. 7-11, 7

sequently assembled one below another and sectionally showing a supporting wall. rigidly connected to form a unitary member. Fig. 13 is a horizontal, sectional view of the A further object is to form such a chord from same, taken upon the line 1313 of Fig. 12.

a pair of rigidly connected standard steel chan- Fig. 14 is a vertical, sectional view of said truss, ,20' nels arranged flange to flange, one above another, taken upon the line 1414 of Fig. 7. and individually bent to a suitable curvature prior Fig. 15 is afragmentary perspective of a top to their connection. chord, modified slightly from the disclosure of Another object is to reinforce a hollow top Figs. -7, 8, and 14. chord, formed as above described of upper and Fig. 16 is a similar view of a further modifica- 25 lower channel beams, by extending within said tion.

chord a reinforcing core, built-up preferably of Figs. 17 and 18 disclose still further modificawooden planks. tions of a built-up top chord, illustrating a pro- Still another object is to provide a truss comvision for attaching a wooden nailing plate. prising an arched top chord and a pair of main Fig. '19 is afragmentary perspective of a top 30 brace members extending from the extremities of chord built up of more than two interconnected said chord to its center portion, and to connect standard steel beams, arranged one aboveanother. saidtop chord and brace member by a system of Fig. 20 is a similar perspective showing a botbracing "comprising substantial uprights, said top tom chord correspondingly built up ofstandard chord comprising a pair of upper and lower steel steel beams.

35 beams welded together at points vertically regis-' Fig. 21 perspectively illustrates an alternative tered with said uprights, whereby stresses aremost form of bottom chord built up of standard steel efiiciently transmitted through said uprights to beams. said top chord. Those forms of the invention diagrammatically 1 Astill further object is to provide improved appearing in Figs. 1-6 inclusive all employapara- 40 joints between abutting portions of the chords of bolic top chord l, a substantially straight bottoma building truss, whereby sections of said truss chord 2, and a pair of main brace members 3 exmay be built up in a shop or yard, so as to be tended to the center of the top chord from the readily rigidly connected when positioned for use. intersections of its ends with those of the bottom These and various other objects theinvention chord In Fig. 1, hangers-4 are extended to the .45; attains by the construction hereinafter described bottom chord from the center of the top chord,

and illustrated in the accompanying drawings, and from one or more intermediate points of each wherein: r main brace member 3.-

Figs. 1 to 6 inclusive are diagrammatic; side Figs. 2, 3, 4, and 5 correspond as to elimination .elevational 'views of various modifications or a of the central'hanger shown in' Fig.1, the bottom truss embodying the same primary improvements; chordbeing supported bya plurality of hangers 5 Fig. 7 is a view in side elevation of substantially suitablylspaced between the truss ends and center. a half portion of an improved truss slightlyl In Fig.6, the top and bottom chords-are confurther modified from the diagramed construe-j ne cted by a plurality of hangers 6, one central of tions; I 9 the truss; and the remainder suitably spaced be-' 155 Fig. 'la-is' a cross sectional view of the truss tween the truss ends and-center.

In each of the constructions diagramed, a system of bracing rigidly connects the top chord 1 and main braces 3. Thus, in Fig. l, a plurality of spaced brace members '7 perpendicular to the main braces 3, extend from the latter to the chord 1, and in Figs. 2 to 6 inclusive, spaced vertical brace members 8 similarly connect said chord and braces.

In Fig. l, diagonal braces 9 are extended between the top chord and member 3 in each of the panels formed by the members '7, said diagonals alternately inclining in reverse directions.

In Fig. 2, the panels between the uprights 8 and individually occupied by diagonal brace members 10, inclined reversely upward from their inner to their outer ends, at opposite side of the truss center.

In that modification shown in Fig.3, the uprights 8 are more numerous than in the other diagrams and diagonals 11 are provided in the panels formed between alternate uprights 8. Said diagonals as shown incline upwardly from their outer to their inner ends, their inclination thus differing at opposite, sides of thetruss center. Said diagonals are Welded at their mid-portions to the uprights 8 which rise centrally of the panels occupied by said diagonals, and thus said diagonals and the uprights to which they are welded strongly reinforce each other.

As shown in Fig. 4, each panel between the uprights 8 occupied by apair of brace members 12 reversely inclined to intersect the top chord midway of such panel. 7

Figs. and 6 illustrate provision of a pair of diagonally crossed brace members 13 in each of said panels.

The improved truss illustrated in Figs. '7 to 14 inclusive comprises an arched top chord (preferably parabolic) formed by paired upper and lower standard channel beams 14 and 15 having their flanges adjoined to form a hollow unit. A rigid connection is established between the adjoined flanges, preferably by welding. Thus, in said figures, welding beams 16 are formed at suitable space intervals.

It is important to observe that the hollow unit formed by said beams is of a cross section unsuitedfor bending, yet highly desirable from the standpoint of strength. The employment of such a cross section in an arched chord is made possible by building up said chord from the beams 14 and 15 which may be individually bent to the desired curvature. v

The lower chord 17 of the truss shown in Figs. '7 to let consists of a standard I-beam. having its web arranged transversely of the truss.

The upper and lower chords are each formed in halves abutting centrally of the truss, and adapted to be readily connected at the place of installation. Thus, a pair of splice plates 18, preferably rectangular, are rigidly moLuited upon the meeting ends of the halves of each chord, transversely of the latter, and are adapted to be bolted to each other face to face as indicated at 15). To attach said plates to the chord beams, welds are preferably established between said plates and beams entirely around the margins of the beam extremities.

The splice plates 18 of the top and bottom chords are connected to each other preferably by a pair of uprights 20a of If-shape in cross section, said uprights being welded to opposite faces of said splice plates and spaced apart by the latter, as best appears in Figs. 7 and These uprights increase the rigidity of each half section of the truss and tend to prevent such vibration of the central portion of either chord (and particularly the lower one), as might tend to loosen the bolts 19.

The described joint is further reinforced by interposing a pair of heavy. sheet metal plates 201) between the beams 14 and 15, one at each side of' said splice plates and welding same to said beams and plates. The lateral and vertical strength 'of thejoint is increased by extending the splice plates some distance above, below and at each side of the top chord, and the plates 202) also preferably project laterally beyond the chord.

t is preferred to reinforce the top chord 14, 15 by inserting in the hollow thereof a core 21 consisting preferably of wooden planks arranged in superposed courses nailed or otherwise fastened to each other at suitable points and having their end joints longitudinally staggered as best appears in Fig.8.. a I

From the ends of the truss, .a pair of main braces 22, preferably rectilinear, are extended to the center of the top chord. Said braces preferably consist of standard channel beamsv having their webs arranged transversely of the truss, their inner ends being fastened to the top chord, preferably by angle bars .23, which overlap and are welded to the lateral faces of said braces and the top chord, as best appears in Fig. 7.

Theouter ends of the'main braces are each welded or otherwise rigidly secured to a pair. of upright angle bars 24, welded to the sides of the top and bottom chords, as best appears in Figs.-

12 and 13. ,Thus said members 24 act to reinforce the joint between the top and bottom chord extremities, as well as anchoring for the outer ends of the main braces 22.

At suitable intervals between the truss center and its extremities, vertical hangers 25 are provided to support the lower chord and its load. These supports preferably have the form of angle bars, terminally welded to the members 17 and 22.

Between the top chordand each main brace .22 is provided a system of bracing,.producing in effect two truss members extended from the ends of the maintrussto the center of the top chord, thereof embracing one-half of the top chord. Thus, a plurality of channel-shapedbrace members 25, and of T-shaped brace members 26a are arranged in alteration at suitable intervals to connect each main brace to the top chord, being, as illustrated, perpendicular to the main braces. In each of the panels formed. between the members 2.6and 26a, a'pair of diagonally crossed brace rods 27'are disposed, said rods and the members 26 and 260, being preferably weldedto the top chord and main braces. The members 26 preferably have the full width of the truss. so that their sides are flush with those of the top an bottom chords.

The truss terminally engages suitable seats formed upon walls or columns 28, superposed sheet metal plates 29 and 30 beingengaged-between the truss extremities and said seats for distributing the truss load to an adequate seat area. The lower chord, which directlyengages the, plates 30 is slightly spaced; below theends of the top chord (as best appears in Fig. 12), and a pair of sheet metal plates 31 laterally overlap the adjoining ends of the two chords and arewelded thereto, as indicated at 32. An anchorage pin 33 is extended transversely of the truss adjacent to the outer ends of the plates 31, a nd to the top edges of the lower chord, and is welded to said ends and edges.

Various possible modifications of the top'chord of the described truss are illustrated in Figs. 15 to 19 inclusive. Thus, in Fig. 15, there is shown a top chord comprising upper and lower standard channel beams 34 having edges adjoining as in the first-described chord, but disclosing continuous welds 35 between said flanges. This secures a somewhat greater strength than the first-disclosed construction, in which the welds are spaced.

The top chord shown in Fig. 16 also employs reversely disposed standard channel beams 36, a sheet metal plate 3'7 being in this construction interposed between and Welded to the flanges of said beams. Said plate marginally projects at the sides of the chord, and its projecting portions are engaged by bolts 38 to support any desired suspended structure.

In Fig. 1'7, a pair of upper and lower reversely disposed channel beams 39 are welded to each other at intervals, and the same welds fasten vertical bolts 40 to the lateral faces of said beams, for attaching a nailing plate 41 to the top of the chord.

The top chord shown in Fig. 18 comprises upper and lower standard channels 42 having strips of heavy sheet metal 43 engaged at intervals therebetween and welded thereto, said strips projecting beyond the side faces of said beams for engagement by bolts 44 for securing a wooden nailing plate 45 upon the chord.

Fig. 19 illustrates the possibility of building up a top chord of more than two standard steel channels 46, the flanges thereof projecting alternately upwardly and downwardly, welds 4'? being employed at suitable longitudinally spaced points to connect said beams.

In Fig. 20,'the same structural feature is shown applied to a bottom chord formed by two or more superposed standard channel beams 48 welded to one another at suitable longitudinally spaced points, as indicated at 49. It is to be noted in connection with the chord forms illustrated by Figs. 19 and 20 that the welds between the beams are registered vertically.

Fig. 21 discloses a further modification for the lower chord of a metal truss comprising a pair of channel beams 50 extending one above the other with their webs adjoining and welded to each other at suitable space intervals, as indicated at 51.

In the described construction, the system of bracing between the top chord and main braces comprises relatively light and small members, and a maximum of space for light, ventilation, or other purposes is provided between the top and bottom chords.

The various types of top chords disclosed by this application are built up of members, capable of inexpensive bending in their vertical plane, by virtue of their relatively slight vertical stiffness.

Said members, however, have a very considerable lateral stiffness, and the unitary connection of a plurality of said members in superposed relation combines their several vertical stiffnesses so that the unit as a whole has great stiffness, both laterally and vertically. Where spaced welds are employed to connect the beams forming said top chord, they are formed at sufiiciently close intervals to insure a vertical stiffness at least as great as that of the complete chord in a lateral direction.

What I claim is:

1. The combination with two aligned chord sections, each comprising upper and lower metal members, of a pair of splice plates rigidly engaging end faces of said sections and meeting in a plane substantially transverse to said sections,

, means rigidly connecting said plates to each other,

and a plate arranged transversely of said splice plates between the upper and lower members of each of said sections, welded to said members and to the adjacent splice plate.

2. The combination with two sections of a truss chord, each comprising upper and lower members and arranged in end to end relation, of a pair of splice plates respectively permanently secured to the adjoined ends of said sections and abutting face to face, transversely of the chord, and marginally projecting at each side of the chord, a plurality of fastenings rigidly interconnecting said plates, and a pair of plates, each positioned between the upper and lower members forming one of said sections and projecting at opposite sides of said members, and endwise abutting against said splice plates, said reinforcing plates being'welded to bers between which they are positioned, and func tioning to interconnect the upper and lower memthe slice plates and to the members, to assist in fastening the splice plates to the chord sections, and to reinforce the chord against transverse stresses.

3. The combination with a metallic chord member of a splice plate, occupying a substantially transverse relation to said member and engaging an end face of the member and projecting above, below and at each side of said member, said member being welded to said plate, around substantially the entire margin of the contact area of the member and plate.

4. The combination with two sections of a truss chord, arranged in end to end relation, of a pair of splice plates respectively permanently secured to the adjoined ends of said sections and abutting face to face, said plates projecting marginand f astenings rigidly and detachably connecting the projecting marginal portions of said plates, I

said plates strongly reinforcing the chord in connecting the sections thereof.

WALTER M. PRATT.

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