US1685107A - Trussed structure - Google Patents

Description

Sept. 25, 1928. 1,685,107

H. G. TREGILLUS TRUS SED STRUCTURE Filed July 14. 1924 3 Shuts-Sheet 1 Haro/d G. Trey illus.

INVENTOR.

A TTORNE Y.

Sept. 25, 1928. 1,685,107

H. G. TREGILLUS THUS SED STRUCTURE Filed July 14, 1924 3 Sheets-Sheet 2 f "1 /4 e z l H 0/0/62 6. Trey/W115 INVILNTOR.

A TTORN E Y.

Sept. 25, 1928. 1,685,107

H. G. TREGILLUS TRUS SED STRUCTURE Filed July 14, 1924 5 Sheets-Sheet 3 Haro/d G. Trey/W115 INVEN TOR.

A TTORNI'IY Patented Sept. 25, 1928.

UNITED STATES HAROLD G. TREGILLUS, OF PARK RIDGE, ILLINOIS.

TRUSSED STRUCTURE.

Application filed July 14, 1924. Serial No. 725,883.

hfy invention relates to trussed structures, and particularly to roof trusses, preferably of moderate spans, for use in buildings, such as garages, factories, theatres, bowling alleys, halls, and all buildings where a clear space, unobstructed by posts or columns, is required. It relates particularly to the construction of the upper chord of the truss. It relates also to the means for connecting the ends of the upper chord to the ends of the lower chord.

One of the objects of my invention is to provide a structure which is made from a number of light members, arranged to cooperate in such amanner that the necessary and desired strength and rigidity are secured.

Another of the objects of my invention is to provide a trussed structure which is compact and has a reduced number of members connecting the upper and lower chords and which allows a maximum of unobstructed light and ventilation of the building.

A further object of my invention is to provide a roof truss which may be readily assembled and built at the place of its installation, thus avoiding the expense and difficulties attendant upon constructing the roof truss at some distant place and transporting it to the place Where it is to be installed Among other objects of my invention is to provide trussed structures which are economical of material and labor, and which may be constructed by workmen less skilled in the art than are usually required for more complicated trussed structures. This I no complish by combining an' arch wlth a tmssed structure of the prior art, in such a manner that the arch is continuously at tached, or substantially so, to the upper chord of the truss. For the purpose of this disclosure, but without intending to limit myself thereto, I have selected, as a pro ferrcd form for the truss, the well known W'arrcn type, although that type is not es sential in the application of my invention.

The upper chord of the lVarren truss illustrated in the drawings is constructed of a series of straight members, inclined to each other, and the arch, which I attach thereto, is so disposed that its longitudinal center line crosses and recrosses the center lines of each of the straight members comprising the upper chord of the lVarren truss.

In practice, the skeleton, which is the Simple Warren truss, is constructed complete within itself, and afterward the arch attached thereto. The simply made lVarren truss forms a frame work upon which to execute the more involved task of constructing the arch.

With the construction of my invention. the effective stress-resisting upper chord becomes a composite member, or a composite upper chord, combining curved and straight means firmly united into one unit. The addition of the curved means to the straight means gives an effective curvature to the whole which is less sharp than that of the curved means considered alone. The entire length of the composite upper chord may then be described as a series of flattened arched segments, end to end, with a slight, but abrupt, deflection where one segment joins another. This construction is most advantageous in that it results in an average of curvature best suited to resist alternate bulging and sagging tendencies due to irregular loading of the structure, as hereinafter explained, and so allows the use of a minimum amount of material forgiven requirements as to strength.

With relation to the connection of the upper chord to the lower chord, a construction is provided whereby the straight membered portion of the upper chord may be attached to the lower chord before the curved arch portion has been constructed, and the remaining parts of the connecting construction necessary to give the required strength to the whole may be added after the arched portion has been completed.

The invention will he more readily understood when read in conjunction with the accompanying drawings, which illustrate embodiments of the invention, it being obvious that various changes and modifications may be employed without departing from the spirit of the invention as defined in the appended claims forming a part hereof.

In the drawings:

Figure 1 is a side elevation of a trussed structure embodying my invention in simple form.

Figure 2 is an enlarged cross sectional View of the trussed structure taken on line 22 of Figure 1, looking in the direction of the arrows.

Figure 3 is an enlarged side elevation of the detail construction at either end of the structure of Figure 1, and showing a metallic lower chord.

Figure 4 is a plan view of the structure shown in Figure 3, the upper chord portions being removed.

Figure 5 shows a construction similar to that of Figure 3 in which a wood lower chord is substituted for the metallic lower chord.

Figures 6 and 7 show, diagrammatically, trussed structures of my invention having different numbers of panels to suit different conditions.

Figure 8 shows a portion of the composite upper chord, or arch, of my invention.

Figure 9 shows a cross section of the upper chord, or art-h, on the line A-A of Figure 8.

Figure 10 shows a cross section of the upper chord, or arch, on the line B-B of Figure 8.

Figure 11 is a diagrammatic View of the arrangement of the composite upper chord of my invention in association with the lower chord and web members.

Figure 12 is a diagrammatic view of the trussed structure showing the effective center line of the upper chord as a series of non-tangential arch segments.

Figure 13 is a plan View of a portion of the trussed structure at the juncture of two straight members and shows a portion of the curved members of the composite upper chord.

Figure 14 is a sectional view taken on line 14 14 of Figure 13.

Figure 15 is a plan view of a portion of the structure shown in Figure 5, the bolt and nut construction being shown diagrammatically, and,

Figure 16 is a diagrammatic View of the trusse" structure, but includes, in addition, tension members extending to the upper chord from the center of the lower chord.

In the structure illustrated in Figures 1, 2, 3, 4, 13 and 14 the straight, angularly disposed members 1, 2 and 3 are preferably timbers, the adjacent ends of which abut against the wood blocks 7 and 8. The member 4, in this figure, consists of two structural steel angles forming the lower chord, which angles are suitably spaced, and which spacing is maintained at the middle of the chord by the wood block 9. Each of the web members 5 and G is conr posed of two planks or boards suitably secured on either side of the wood blocks 7, 8 and 9. Wood strips 10, 10, 11, and 11 are, respectively, secured to the adjarent ends of the straight members 1, 2, and 3 and to the blocks 7 and 8 for the purpose of holding those pieces in position during construction and may be removed later. A metallic U-shapcd member 12 is placed around the lower ends of each of the straight members 1 and 3 and is attached to each of the ends of the angles 4 by means of bolts and nuts 13, as clearly shown in Figures 3 and 4.

On each side of this structure is secured, by means of nailing, spiking, or other suitable means, the arch members 14 and 14*, each of which consists, preferably, of laminated elements or a plurality of superposed planks or scantlings, or other suitable material, sprung to the required curvature. The abutting ends of the straight members 1, 2 and 3 generally protrude above the top of the laminated arch members 14 and 14, but their intermediate portions are generally below the top of the arch members 14 and 14 The ends of the arch members 14 and 14" are cut oil in the horizontal and vertical planes a and b, respectively, as shown in Figure 3.

A metallic abutment member is arranged at each end of the truss and includes a plate 15 which is attached to the transversely arranged angle iron 16 by means of countersunk rivets (or bolts and nuts) 17. The plate 15 is also attached to the lower chord angles 4 by means of bolts and nuts 18. The ends of the arch members 14 and 14, where they are cut ofi'f in the plane a, rest on the plate 15. The inside face of the angle iron 16 bears against the arch memebrs 14 and 14 in the plane I), which thus securely holds the arch members with relation to the remainder of the structure. The straight member 1, or 3, as the case may be, is supported by the plate 15 and restrained against outward thrust by the metallic U- shaped member 12, and the arch members 14 and 14 are supported by the plate 15 and restrained against outward thrust by the angle iron 16. The angle iron 16 serves a shoe and bears upon the wall of the building or other supporting means which may be employed (not shown in the drawings).

For the purpose of anchoring the ends of the truss into the wall, or other supporting means, the angle irons 16 are made of suiiicient length so that their ends protrude beyond the width of the arch members 14 and 14". These projecting ends when solidly built into the wall provide the necessary anchorage.

In onstructing the building, the required number of trusses, suitably spaced, are set upon the side walls, columns, or other supports, and the roof joints, or purlins, are laid upon the arch members 14 and 14 in the usual manner and spiked. At the points where the straight members 1, 2 and 3, and the blocks 7 and 8 project above the arch members 14 and 14 the joists are notched, which thus holds the tlllS': securely against lateral displacement (not shown in the drawings).

(ill

VYhcre it is preferred, a lower chord whichconstructed of woed 19 shown in Figures 5 and '15, may be "siilistituted for the steel angles 4' shown in Figures 1, 3 and 4. lVith this construction, the lower chord: consists, preferably, of two similar a horizontal plane 0, allowing the lower chord timbers l9 and l9 to be attached on both sides of the upper chord timber 1 or 3,515 the case may be, to which they are secured by the bolts and nuts 23, and to which they may'also be spiked. A metallic U-shaped memher19 similar to the U-shaped member 12, shown in Figure 3, may be attached to reinforce this structure; however, this is not essential, as generally the bolts 23 are sufficient. to resist the stresses encountered.

lVhre it is inconvenient to provide timbers of sufficient length to construct trusses of long span, the upperchord. may be divided into four or more panels, as shown in Figure 6. In this arrangement the members 214, 25, QG and 27 constitute the upper chord, and with the struts' 28, 29, 30 and 31 and the lower chord 32, produce another form ofa complete \Varren truss. To this VVarren truss is'added the laminated arch member 33, the Whole forming another embodiment of my invention- Figure 7shows how, in small structures,

the struts or web members may be omitted entirely, and the laminated arch member 34 added to the simple triangular truss, in which 35 and 36 are the upper chord timbers and 37 is the lower chord.

In the foregoing it has-been assumed that timbers of the necessary size are always ob-' tainable from which to produce the upper chords. however, when this is not possible it is understood that these timbers may consist of two or more planks or boards placed side by side and secured to each" other was to present the same ross section as would be presented by a single timber. Upon occasion it may be'preterable to use several smaller timbers, arranged one above the other, a substitute for the larger timber. Either of these methods of building up members termed upper chord"or com posite chord is contemplated in my invention.

In the preceding specification, and particularly inthe following description of the functioning of the structure of my invention, I have occasion to make use oi certain terms having accepted meanings within the art of structural engineering not always in accordance with the meanings outsid c the art, "'ljhcre tore, l wish to define thes terms as 'used herein.

T he upper chord and lower chordiin a trussed structure are iiaincs appliedi to the main members"estending 'f rom one end the other of the structure, whether str ai ht, curved, or in a series of lines. In an arc ed. truss, the arch may be termed the upper chprdfi, whereas in geometryjonly the line joining its'ends would be ter'med'thc chord, The web members of' atru ssed structure are the comparatively short incinhers join ing the upper andlower chords, which, by resisting tension or compression it-p1 maintain the chords in theirrelatiivc po. tion.. v .H The center of gravity of a member herein indicates the center of area ot'fits' cross sea tion throughout its lengthl The ceiiter of gravityof a" straight member, then, is" any point in the longitudinal axis of the member, whereas, in mechanics, only the middle pdiht of the axis would be so defined. Similarly, the center of gravity of a curvedmenih er is any pointin theturvd/liiicalongits center. '7 i Referring to Figure 8;, the dotted, line (Z, indicates the center ofgravit'y offthe timber 2." The dotted line a indicates t e-"cntif of gravity ofthe arch members" 1 and 'l ifl combinedl' The center i'gra'vity of the combinedstraight and curved members will then lie somewhere between -the ddtt d 'liiies (Z and e andfits approximate position is' ind'i} cated bv the line By referring to Eigiires 9 and 1 0 it will be seen that th eselines (1,12, andf, respectively, pass tmmgamaeaaa of area of i the cross section off their re spective units at any-point througheiit the length of thememben 'W w If the top chord'bf an arched truss is parabolic, under uniform load; throughout, the arch will be in compression but will, have no tendency either to bulge or sag. If; no certain portions are loaded andf'on portion is without load, the loaded po rtionsiesist; compression and also a tende ncy to \vlii le the unloadedv portion resists compres sion and tends to bulge. It the chord: portion shown in Figure 8 be co nsideredlas a portion of a truss, uniformly loaded through, out its length, it would best resist the sagging tendency if its effective center of gr av ity were the line 6, but, on the other hand, if it he considered as an unloaded portion, the bulging tendency would be eliminated it" its center of gravity were the line (1: Therefore, to be most eificient under either condition, it is desirable thatthe effective center of gravity be intermediate the lines J and e, as, the line V By proportioning the areas of the timber 2 and the arch members 14 and 14 itispossible to establish the position ofthe line f so that the entire composite upper chord member will be equally effective against compression and sagging, or compression and bulging, so that there is no excess of material for the one condition in order to provide sufficient for the other. The economy of this construction, is, therefore, obvious.

The described construction of the composite upper chord permits longer portions to be employed and disposed between the web members, and dispenses with the use of certain web members which would otherwise be required, and also increases the lighting and ventilation in the building and improves the appearance of the trussed structure.

As before stated, the upper chord. of the Warren truss, illustrated in the drawings, is constructed of a series of straight members 1, 2, and 3, which are inclined to each other. The arch member 14, which is cooperatively arranged with respect to these members 1, 2 and 3, is so disposed that its longitudinal center line crosses and recrosses the center line of each of the members 1, 2 and 3, as indicated at g, h, i, j, k and Z, in the diagrammatic drawing Figure 11. What has been stated with relation to the arch member 14 also applies to the arch member 14. The effective upper chord then becomes as illustrated in Figure 12, and may be termed an arch which is bent slightly but abruptly at the points m and a, compensation being made for these bends by reducing the curvature of other portions of the arch, or, in other words, a series of arch segments, each segment having less than sufficient rise or curvature to convert the whole into one continuous arch.

When, on account of the necessity of providing openings of given shape or size through the truss, it becomes necessary to vary the positions of certain web members, or even to eliminate them entirely, this alteration may change the function of such web members as are displaced, and, thus, in some cases, change the type of the skeleton, or foundation truss from a Warren to a Pratt truss. I, therefore, desire to emphasize the fact that, while the combination of an arch with a truss of the Warren type is, in most instances, the preferred form of my invention, it is clearly within the scope of my invention to apply it to a Pratt, Howe. Fink, or any other type of truss best suited to the conditions encountered in practice.

I wish further to point out the relationship of my present invention to my prior invention covered by my Patent Number 1330,77], which, in claim 4, refers to the combination of an arch with an inverted truss; the arch being connected to the truss at various points throughout its length. In my present invention, the Warren truss is not inverted when the structure is uniformly loaded, but, under certain conditions of partial loading, the Warren truss is in verted, i. e., the function of the Warren truss is to hold down the arch where it tends to rise rather than hold it up where it tends to sag. In my present invention the arch has connection with the truss which is substantially continuous throughout its length. While it is evident, therefore, that my present invention is broadly covered by my Patent Number 1,330,771, and that the structure herein described is a modification of the structure disclosed in that patent, it is also apparent that the modifications referred to are not described in that patent and constitute distinct and separate invention.

My present invention is also related to the structures of my co-pending application, Serial Number 391,035, filed June 23, 1920, The drawings of that application show, in Figure 3, an arch combined with a \Varren truss, the arch being connected directly to the truss at its ends and two interi'nediatc points. and indirectly connected to the centor of the lower chord at the other points by means of tension members whose function is to resist bulging of the arch. In my present invention, I am able to dispense with these tension members, for the reason, that the bulging tendency is decreased as previously described, and the arch, being combined with the straight member, is able to resist what bulging tendency remains. Upon occasion it may be desirable to add to the structure of Figure 1 tension members extending from the block 9 to intermediate points on the members 1, 2 and 3, as shown diagrammatically in Figure 16, thus combining my present invention with that of my co-pending application above referred:1 to. i

Other combinations of the herein disclosed invention with the structures shown in the drawings, or otherwise disclosed in my Patent Number 1.330571, and my copending application. Serial No. 391.035, are contemplated to suit special conditions as they may arise.

Having fully described my invention, what I claim and desire to secure by Letters Patent is:

1. In a structure of the character described, the combination of a truss, including angularly disposed upper chord members, and an unbroken arched member substantially continuously connected thereto, said arched member being disposed relatively to the angularly disposed upper chord members of the truss so that it crosses and recrosses said angularly disposed upper chord members, said arched member being of curved laminated construction.

2. In a composite trussed structure comprising wood upper chord and metal lower Ion chord members and web members, part of the connecting means between said chord members being a U-shaped strap, a horizontal plate connected to an end of said metal lower chord member, and an angle iron having greater thickness than said plate, said angle iron having its horizontal leg beneath and connected to said plate, and its other leg projecting upwardly and vertically in a plane perpendicular to the plane of said upper and lower chord members, said plate and angle iron confining the end of said wood upper chord member and receiving portions of downward and outward thrusts respectively from said upper chord member, the end of said upper chord memher having horizontal and vertical faces by means of which said downward and outward thrusts are transmitted to said plate and angle iron.

3. A truss complete within itself, comprising upper and lower chord members and web struts, all of said component truss parts being straight and angularly disposed one to another, any two of said members and struts forming two sides of not more than one complete triangle, the corners of any such triangle constituting panel points in said truss, the component portions of said upper chord members being also angularly disposed to each other, arch means combined with said straight upper chord portions and substantially continuously and directly connected thereto, thus forming a composite upper chord means, said arch means being so combined with said straight upper chord portions that their axes cross and recross each other, and arranged so that the depth of said combined upper chord means is maximum at points intermediate adjacent panel points.

4. A truss complete within itself, comprising upper and lower chord means and web struts, all of said component truss parts being straight and angularly disposed one to another, forming a series of adjacent but non-overlapping triangles, said upper chord means comprising planks connected end to end, angularly disposed one to another and having their wide surfaces in the vertical plane, laminated arch means combined with said upper chord means, comprising curved scantlings having their narrow edges in contact with said wide surfaces of planks, the scantlings being fastened to each other and to the planks.

5. In a trussed structure, an upper chord portion comprising a wood plank set on edge, and curved laminations having portions of their vertical faces fastened in contact with said plank, the whole chord portion thus formed having its greatest Vertical dimension intermediate its ends.

In witness whereof, I hereunto subscribe my name this 9th day of July, A. D 1924.

HAROLD G. TREGILLUS.

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