US8224A - Means for adjusting the effective length of bribge-cottntekbhaces - Google Patents

Description

No. 8,224. A PATENTED JULY .15, 1851. D. o. MEGALLUM. MEANS EOE ADJUSTING TEE EFFECTIVE LENGTE -O'EBEIDGE COUNTER BEAGES.

N STATES 4Farm.TT OFFICE.- N

. D. `o. MeoALLUM, or owiaeo, New ronK.

` "MEANS For. ADJUSTING THE AEFrnctrivr. LENGTH oF Baines-CONTERBRAQES. i

. spcification of Letters Patent naseaeatea Juiy 15, 1851.

companying drawings, forming partfof this' t specification, in which*H "F'gure, l is 1alongitudinal elevation of a bridge girder. Fig. 2 is a longitudinal vertical section of part of `the same. t Sis a plan of part of the upper chord." Fig. i this `a transverseisection through theline @fain Fig. 1f, i. Figs.`5 and 6 represent the counter braces,` ona `scale larger than the othergu-rfes.

` Sfn-filarletters ofreference indicate cort respondingparts in each of the several `figures; p i

'My inventionrelates to the construction of open built beamsor girders employed in bridges, and `other structures of asimilar nature.

My `improvement consists in a new method of lengthening, or shorteningthecounter braces, whereby I enabled to produce and maintain any required down- `ward vertical strain, or deflection, upon the girders, and which method I deem far more useful in practice than those sometimes employed of using gibs and keys, or wedges for that purpose.

A, represents the lower chord of the girder, composed of four dr of any suitable number of string pieces bolted together and having cleats a, a, placed between them at suitable distances. -having only a very slight camber.

It is nearly straight, B, is the upper chord, formed also of any suitable number offstringers, and is of an arched form. The two `chords are connected by posts 0,0, forming' radii to the upper chord,

and` also at'their ends, by vertical` posts E, E, all of the said posts being so connected with the chords as to maintain the required positions of the several parts.

D, D, are thrust braces, each notched into the top of one oi the posts C, C, and into the foot of the next post nearer the end of the girder.

F, F, are inclined ties, or tension rods, outside the girder. t

G, G, are ties, or tension rods, similar to Fig.

F, F, passing through the lower and upper chords of the girder, at about the middleof its thickness.

Theseveral parts of thegirder, as far as I have described them, do not differ, essentially, in their `construction and arrangement from those of some other girders ,in use. Each of the` ties or tension rods last described, G, is incased by a counter brace H, the lowerpartfof which is of wood, and may be eitherf in one piece, bored through, t admit theA rod, 4"or in two pieces, placed one on y.each side of the rod; the lower end abutting on `a step b, placed on the lower chord,

t at the foot of the posts @,and its upper end `fitted to a metallic sheath I, through which also` the tensionrod passes. Thissheath, which lis best shown in Figs. 15 and 6consists of a `tubejhaving at its lower end `a socketlinto which the top of the counter braceH,`is fitted. The tension rodspass through clamping pieces c, J0, under the lower chord, and others c', 0", above `the upper chord.` These clamping pieces bear also against the head and foot of the posts C, C. `Theupper end of the sheath passes through the clamping piece c', .andis of suflicient length to project a shortudistance above it. `A plate of metal, ,having 4a hole through it of justsuliicient size topass the rod G is attached, at the top of thel girder, by bolts e, e, which pass through the clamping pieces, the upper chord, and the posts C, C, in a direction parallel with the tension rods. This plate bears` on `top of the sheath I.

J, is an arched beam, placed immediately i below the upper chord B, and notched between the posts C, C. IteXtends: from the crown of the arch` about half way tothe` pass through the lower chord A, and thebolsters I1, L, and rest in seats, on the top of the abutments or piers.

M, M, are other inclined struts their upper ends abuttingagainst steps g, g, under the upper chord B. They are secured to the posts, and pass through the lower chord and bolsters, and rest upon the abutments or piers, in a similar manner to K, K. Those counter braces H H which come in the way put together, and all except the tension rods G, G, and bolts, e, e, are bolted or screwed up. The bridge should then be loaded with a weight, greater than it will ever be required to bear, in ordinary traflic. It has been stated, in the foregoing description, that the length ofthe counter braces, is such, as to allow the ends of the metallic sheaths I, I, to project through the clamping pieces,

c', 0. This projection should be such, that the deflection of the girders, caused by the weight on the bridge, will, by increasing the dist-ance between the steps b, b, and the clamping pieces 0, c', cause the ends of the sheaths, to stand exactly flush, or a little above, the face of the clamping pieces. The plates, d, d, are then screwed down, to bear on the end of the sheaths, by means of the nuts and the bolts e, e, by which the deflection, producedby the load is maintained, after the load shall have been removed. The nuts on the ties or tension rods-G, G, may then be screwed up, to bring t-he required degree of tension upon them.V

The braces H, H might be continued through the upper chord of the girder, but

the metallic sheath I, is better suited, as it deflection, may be brought upon it, without increasing Jthe strain, or deflection, and consequently the girder will not be subjected to any vertical vibration, by the passing of this lesser weight over it. Wedges have been used, to effect this desirable object, but as they are liable to become loose, and work out of place, an effectual remedy and substitute is above described. 0

lVhat I claim as my invention, and desire to secure by Letters Patent, is y The method of lengthening or shortening the counter braces of a girder or bridge truss, so as to produce and maintain any desired, vertical strain, or deliection, of the girder or truss by means of the counter brace H, Whether all of'wood or provided with a metallic end or sheath; the plate of metal ci, bearing, upon the metallic end or sheath, (or upon the end of the wood, when the metallic end or sheath is not used) Y at the top of the girder; and the nuts, and the bolts e, e, passing through the clamping pieces, c, c, the upper chord, and the posts, by which the plate of metal d, is drawn down upon the metallic end or sheath and the adjustment ofthe length, of the counter brace is effected, substantially as herein described.

D. C. MCGALLUM.

lVitnesses:

W. H. STEWART, SILAs C. HAY.

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