USRE34E - Improvement in wooden-frame brace-bridges - Google Patents

Description

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N.PETERS, PHOTO-LITHOGRAPHER. WASHINGYON, C.

-frame, and also the manner of UNITED STATES PATENT OFFICE.

STEPHEN H. LONG, OF MARIETTA, GEORGIA.

IMPROVEMENT IN WOODEN-FRAME BRACE-BRlD-GE-S.

Speciiication forming part of Letters Patent No. 1,398, dated November 7, 1839; Reissue No. 34, (lated July 20, 1841.

To all whom it may concern,.-

Be it known that I, STEPHEN H. LONG, of the United States engineers,l1ave invented certain Improvements in the Construction of Wooden or Frame Bridges, the objects of which are greater simplicity, economy, and efficiency in the mode ot bridge-building, and in the arrangement ofthe parts of bridges, than have hitherto been attained by any combination of principles or arrangement of parts heretofore adopted in structures of this nature.

The several parts of the bridge to which said improvements relate are the strings and their splices, the posts, the main braces, the counter-braces, and the arch-braces of a trusstrnssing or straining the truss-frames.

The several parts above enumerated have the same relation to the bridge, and are intended to impart a similar efficiency in sustaining it, as those designated by the same names in the several patents obtained by me `for wooden or frame bridges, and to which reference may be had. These parts, however, in the structure herein described, vary materially in their relative and especial] y in the transverse dimensions of the timber used from those contemplated and described in the patents above cited.

Iusteadof timbers of variousksizes and of nearly a square form,the several parts alluded to are to be uniform, or nearly so, in all their transverse dimensions, a transverse section of each timber of all the parts having the form ofa parallelogram, varying from two to four inches by eight to twelve or ifteeninches, according to the length of the bridge-span, the weight of the load to be sust-ained upon the bridge, and other circumstances connected with these considerations.

Instead ot'notches or recesses in the stringpieces and posts, by means of which these parts are locked together, and instead ot' wedges at the insertions ofthe posts between the string-pieces, the connections between the posts and strings areY effected by means of gibs and keys passing entirely through the strings transversely thereof, and at the same time resting in notches prepared for the reception of the gib and key in the back ofthe post, or in the side opposite to the points or steps at which the main braces communicate three inches thick, and three or four inches wide are inserted in the spaces/between the string -pieces and immediately behind the posts, for the purpose of aiding the gibs and keys in counteracting the thrust ot' the main braces. The coggles are applied subsequently to the adjustments effected by trussing, being confined at one end by appropriate notches in `the posts for their reception, and at the other by treenails passing through them and the string-pieces. The main braces are connected to the posts by means ot' notches or steps in the latter, adapted to the reception of tuscums at the ends of the former. and steps, as described in the preceding paragraph, steps of cast-iron, with appropriate lugs or bearings on opposite sides of each step, adapted to suitable receptacles for the same in the posts and braces, as represented in the accompanying drawings, may be substitutedffor the purpose of receiving and resisting the action to which these parts are subjected. The counter-braces occupy the entire distance between thc upper and lower strings diagonally of each panel of the trussframe, and are confined between the posts by treenails passing through them and the posts near the strings. They may also be confined to the main braces by treenails passing through them at the intersections of the former with the latter. The counter-braces are brought into their appropriate action by straining upon n the gibs and keys of the strings,in the manner The arch-braces rise in before explained. three or more pieces from a bench or bolster attached to the abutment or pier below the bridge, pass through the lower string in two or more pieces within the openings or interstices occasioned by the posts and main braces, enter the first, second, or third panel of the truss-frame, counting from each end of the bridge-span, and thrust against the further- Instead of tuscums tain and ecent, another splicing-piece is inbrace is to thrust firmly against a plate of the most posts of the panel entered, being intercepted by these posts, against which the thrust of the arch-braces is communicated in part by means of appropriate notches in the former and corresponding tuscums in the latter. The action of the arch-brace is continued past the posts by similar pieces and connections within the next panel, and by the aid of a splicing-piece situated between the posts and extending from the counter-brace of the panel first entered -to that of the panel beyond, and occupying the space between the side pieces of the arch-brace. Thus continued, the arch-brace extends to the head of the next main braces, and is connected with them near the upper string by means ot' corresponding tuscums and notches. In order to render the action ofthe arch-brace more cerserted, extending from the counter-brace last mentioned to the head of the next counterbrace, and occupying, as before, the space between the cheeks or side pieces of the archbrace. rlhe several parts of the arch-brace situated within the truss-frame, as also the posts and main braces at the crossings or intersections of the arch-braces, are firmly united by treenails passing entirely through the several pieces of which they are composed. rlhe interior portions of the arch-braces situated beneath truss-frames are respectively furnished with a series of gibs and keys, which serve not only to confine together the pieces of which they are composed, but also to render'the arch-braces extensible, or the reverse, as may be found necessary, either to give appropriate action to the arch-brace or to increase or diminish the camber of the bridge.

In addition to the inferior portions of the arch-braces above named, I also sometimes employ what I denominate side arch-braces,77 and these-rise from the lower string-pieces at or near the first, second, or third set of posts from each abutment or pier, and extend obliquely upward, embracing each of the sides of the truss-frame to the upper string crossing one, two, or more panels, as may be deemed most expedient. The head of each side archsame transverse dimensions, situated immediately below and parallel to the upper string. The foot of each side arch-brace is to thrust against a sill of similar transverse dimensions resting edgewise on the lower strings and extending through a distance of one or more panels of the bridge. 4The side arch-brace plates and sills must be firmly connected with the truss-frame by means of bolts, clamps, treenails, or other device passing through them and through the posts and main braces at their several crossings. At all junctions, either of the brace with the plate or with the sill, and at all intermediate joints,a thin plate or sheet of iron should be inserted, in order to prevent the bers or grain of one timber from penetrat-ing between those ofthe other. The splicabove and below.

ings of the outside string-pieces are eected by means of wooden splicing-pieces with appropriate notches and corresponding tuscums, or With coggles of iron or wood situated in appropriate notches prepared for their reception in the splicing-piece and string-piece, and may be clamped together by gibs and keys, or by screw bolts passing entirely through the strings. The central string-piece may also be spliced in a similar manner, or by means of treenails of wood passing entirely through the strings, no other clampings being required in this case. The lateral bracing is effected by means of locked lattice-work banded by ribbands on both sides of each truss-frame of the bridge,both above and below the lateral braces. The rib-bands are confined to the lateral braces by treenails passing entirely through them and the braces at every intersection of the former with the latter.

The accompanying drawings will serve to illustrate and make known the manner in which I construct the respective parts of my brace-bridge and carry myimprovements into operation.

In Figure 1, A B C D represent a side view of part ot' a truss-frame, C D being the archbrace. with its lower end, C, resting on a bench or bolster on the abutment or pier below the bridge, n n a showing the situation of the gibs and keys by which the respective thicknesses of timber of which the arch-brace consists are confined together.

In Fig. 2, A B C D are an enlarged view of a part of such frame, drawn to a scale suiiciently large to exhibit the mode of connecting the respective parts thereof. arch-brace. E E are the main braces, F F the counter-braces, and G G the posts. The timbers constituting the arch-brace are connected at g g with the posts G by means of tuscums and notehes,and with one of the main braces E by similar means,as shown at e. The main braces E E are likewise connected with the posts G G, both above and below, by like means. The posts rG G extend a few inches above the upper and below the lower strings.

These strings consist each of three thicknesses of stuff, as shown at H, Fig. 3. rIhe posts GG and the main bracesEE are eachof them double, and their ends arev received into thespaces between` the center and the two outer stringpieces. 'The counter-bracesF Fare single and abut against the center string pieces both They are treenailed at each end to the posts G G, and also to the main braces where they pass between them. The space between the two pieces of timber which constitute the arch-brace C D, I usually ll up by inserting what I denominate splicingtimber, and connect the whole together by passing treenails through them.

It has been mentioned above that n n n in Fig. 1 show the situation of the gibs and keys by which the respective timbers composing the arch-brace are connected together. Such C Darethe A cccc, Fig. 2.)

` arch-braces in Fig. 4. Between the stringgibs and keys are also employed for the same purpose in various other parts of the structure. Thus, for example, they are employed in mortises through the timbers, (shown at The manner of constructing these gibs and keys, and of inserting and fixing them so as to confine the timbers together,will be manifest upon reference to Fig. 5, where they are represented on an enlarged scale. They are also shown as passing th rough the string-pieces in Fig. 2 and through the pieces, and immediately behind and in contact with the posts, I insert coggles or blocks of timber, (represented byb b b, Fig. 2,) which I fasten in place by treenails. These are for the purpose of sustaining the posts and preventing their yielding or splitting at the gibnotches. The mortises c c c (shown on the upper and lower string-pieces in Fig. 2) intersect the posts in those parts, and the posts are necessarily notched out to allow the gibs and keys to pass on their sides opposite tothe main braces. These notches in the posts serve, as above remarked, to maintain a relative distance between the upper and lower stringpieces, to clamp and confine them together,

and to impart the requisite power oftrussing to the truss-frame. A

Fig. 3 exhibits different views of a portion of the string-pieces` showing the manner of splicing them, and also the relative positions of the string-pieces. posts, and braces as they project into and arecon nected with each other. These representations apply equally to the upper and the lower portions of the trussframe. f

Fig. 4 represents a portion of the arch-brace with the manner of applying the gibs and keys thereto, by which it may be extended or contracted at pleasure, the several mortises for the gibs and keys being at equal distances from each other. From this arrangement the camber of the truss-frames may be increased or diminished, as may be required. The center and the two outer pieces of the five thicknesses (represented as clamped together iu Fig. 4) are thosevwhich rest upon the bench or bol-- ster of the abutment or pier. The other two pieces are those which pass up into the trussframe.

Instead of the notches and tuscums formed in the timber for connecting' the main braces and the posts, I sometimes employ steps or bearings of cast-iron, which are `furnished with lugs or tusculns projecting out from each of their sides, and entering corresponding notches made in the posts and braces. These are shown in place at a a, Fig. 2, and separately on an enlarged scale at Fig. 6.

Similar stepsor pieces of cast-iron may be brace-bridge with the bined with the other parts thereof. In this gure I have shown two inferior arch-braces, A and B; and I have also shown a double set of side arch-braces, ed in dotted lines. marked C C, and the inner ones C C'. The outer braces have their ends against 'the plate each against the additional sill-piece D D. `The second or inner pair of side arch-braces, C C', are shown as abutting against each other at their upper ends, and at their lower ends against the piece D D.

by connecting posts, main and counter braces, and archbraces, ed as set forth, using therewith such bolts or treenails as I may deem proper, but not intending to claim the use of bolts and treenails as making any part of my invention.

k ing through the string pieces and into the posts near their ends, for the purpose of trussemployed for splicing andk uniting the stringpieces, being substituted for the intermediate notched splicing-pieces of wood, (represented vas used at H H, Fig. 3.)

Fig. 7 .represents the truss-frame of my side arch-braces comthis part being represent- The outer braces are E E, and the foot of Having thus fully described the manner in which I construct my brace-bridge and counect the respective parts thereof together, what I claim cure by Letters Patent, is the 'followingthat is to say:

as new therein, and desire to sel. The forming of the truss-frames of bridges and combining string pieces,

by the aid of gibs and keys construct- 2. The employment or use of the gibs and eys formed in the manner set forth, and passing and straining the frame generally.

3. The manner of arranging the arch-braces so as to diminish or to increase the camber of the truss-frames by the employment of gibs and keys passing through those portions thereof Which constitute the lower parts of said archbraces.

4. The construction and employment of a bearing or step of cast-iron, furnished with lugs or tuscums which are let into corresponding notches in the head and foot of the main braces and the posts, in the manner and for the purpose set forth.

5. The combining with the truss-frames,

constructed as herein set forth, the side archbraces embracing between them ive posts and braces over which they pass, and connected therewith, as herein shown and fully made known.

the respect- STEPHEN H. LONG.

thrust at their upperV

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