US729016A - Bridge construction. - Google Patents

Description

NO MODEL.

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PATENTE-D MAY 26, 1903. J. ToMLINsoN.

BRIDGE CONSTRUCTION.

APPLIGATION FILED DBO. v20, 1902.

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PATBNTED MAY 26, 1,903.

. J. ToMLINsoN. BRIDGE CONSTRUCTION.

APPLICATION PILED DEO. 20, 1902.

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UNITED STATES Patented May 26, 1903.

PATENT OEEICEc BRIDGE CONSTRUCTION.

SPECIFICATION forming part of Letters Patent No. 729,016, dated May 26, 1903.

Application filed December 20, 1902l Serial No. 136,084. (No model.)

To ctZ/'f whom, it may concern:

Be it known that I, JOSEPH ToMLINsON, a citizen of the United States, residing at Cedar Rapids, in the county of Linn and State of Iowa, have invented certain new and useful Improvements in Bridge Construction, of which the following is a specification.

Thisinventiou relates to suspension-bridges and similar structures supported by eyebarchains, wire cables, or both, attached to fixed anchorages at their shore ends.

The object of the invention is to provide for the construction of bridges of long span having great stability without excessive weight, the object being attained in part by suspending the main trusses in the same planes as the cables, which planes are inclined to the perpendicular, and in part by compensating for the contraction and expansion of the cables, so as to avoid any detrimental deflection under the influence of heat and cold.

The nature of the invention will fully appear from the description and claims following, reference being had to the accompanying drawings, in which- Figure l is a side view of a suspensionbridge illustrating my improvements. Fig. 2 is an enlarged view of the compensating device to show more clearly the details thereof. Fig. 3 is a cross-section showing the inclination of the cables and trusses. Fig. 4 shows detail of the cable supports at the piers. Fig. 5 illustrates a compound lever which may be used instead of a simple lever as a part of the compensating device.

e One of the most serious difficulties that has arisen in connection with suspension-bridges is due to the effect of changes of temperature on the long cables, the expansion and contraction of which cause injurious changes of form in the rigid trusses which they support. A part of my invention relates to means for compensating for this variation in the length of the cables, so that no serious change of form takes place in the structure in winter or summer.

In the drawings, A designates one of the main piers of a suspension-bridge.

B is a pier at the shore end of the saine.

C is the anchorage, supposed to be at an indefinite distance to the left. The main truss The inclination of the saddles should of4 course correspond with the inclination of the cables, the cross-beams being suitably beveled therefor, as shown. The posts are so mounted by suitable joints as to admit of their swinging a limited distance in a vertical plane parallel with the bridge; but transversely the construction may be as rigid as desired. Obviously under the` stress of a heavyload the truss midway of the span (and proportionately toward its ends) settles somewhat, and in harmony with this action of the truss, and its expansion and contraction as well, the cable-supports are made to rock in the manner above indicated.

It will be noted that the inclination of the trusses corresponds with that of the cables, as appears in Fig. 3. This construction serves to brace the bridge laterally against windpressure and is of advantage, furthermore, because it admits ofl the lower cross-beams being made considerably shorter than the upper ones, with a corresponding saving of material. In the type of bridge shown in Fig. 3 the narrower lower floor would be used for a railway-track and the upper one serve fora foot-bridge.

Referring to Fig. l, it will be seen that for the greater portion of their length the cables are connected by Suspenders K with the upper chord of the truss. This construction gives a suspending function to the diagonal and vertical members of the truss and admits of their being made much lighter than would be possible were the truss suspended from the bottom chord. It is evident, too, that the lift of the Suspenders is well distributed, since it embraces as to the bottom chord the base of the triangle whose sides are the braces TOO converging at the point of suspension. These advantages in construction, it is believed,will admit of the erection and successful operation of suspension-bridges for railway traffic of very long span when applied in connection with other novel features of construction to be more fully hereinafter described. In so far as I am aware this kind of engineering has not hitherto been practically carried out to any considerable extent, owing in part'to the great weight required in the trusses and in part to the changes in form due to variations in the deflection of the cables, as above mentioned.

Referring now to Figs. l, 2, and 5, it will be seen that the cables terminate at the shore ends of the bridge and there connect with the short arm of a level' L, as does also the end of the truss. The other end of the short arm of the lever connects with the shore-anchorage by a suitable cable, chain, or bar N. To the long end of the lever is suspended a heavy weight M. The end of the truss is also anchored to the pier B by a suitable anchor O and a short link P, which allows for the expansion and contraction of the truss. lThe main purpose of this anchorage is to prevent the lifting of the shore end of the bridge by a heavy load on the main span or other cause. By this construction the cables are subjected to a uniform tension and cannot, therefore, sag in summer and draw taut in winter,with the consequent changes in the form and elevation of the truss. The same principle is illustrated in Fig. 5, but with a pair of oppositely-extending levers connected by an eyebar Q. The weight in this case depends from the longer arm of each lever.v When placed at the middle of a span, as the device might be, an end of cable would connect with a short arm of each lever, as shown. When applied to the shore-anchorage, the anchor conne'ction would of course take the place of one end of cable.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-

l. In a suspension-bridge, the combination with suitable cable-supports, of cables depending in downwardly-converging planes, and trusses lying in planes parallel thereto.

2. In a suspension-bridge, the combination with suitable cable-supports, of cables depending in downwardly-converging planes,

trusses in planes parallel thereto, and suspenders depending from the cables and attached to the upper chords of the trusses.

3. In a suspension-bridge, the combination with suitable supports for the cables, of cables depending therefrom in downwardly-converging planes, trusses depending from the cables in coincident planes, cross-beams con necting the lower chords of the trusses, and longer cross-beams connecting their upper chords.

4. In a suspension-bridge, the combination with cables depending-in downwardly-converging planes, of saddles therefor set at right angles to such planes, and suitable supports therefor.

5. In a suspension-bridge, the combination with cables and trusses, of levers connecting by their shorter arms with the shore ends of the cables and trusses, a connection of the saine arms with the shore-anchorage, and a heavy weight depending from the long arms of the levers, substantially as and for the purpose set forth.

6. In a suspension-bridge, having cables and trusses substantially as described, of a leverconnecting by its shorter arm with the cable and truss, a shore-anchor connecting with the same arm, a heavy weight depending .from the longer arm, an anchor to connect the end of the bridge with the shorepier, and a link connecting said anchor with the end of the bridge, substantially as described.

7. In a suspension-bridge having cables and trusses, substantially as described, a lever adapted to connect with a cable by one of its arms, an anchor connecting with the lever at a short distance from the cable connection, and a-weight depending from the longer arm.

8. In a suspension-bridge, the combination with the cable and anchor, of a pair of oppositelyextending levers, a link connecting with their shorter arms, a connection of the cable with one such arm and of the anchor IOO with the other and a Weight depending from both longer arms, substantially as described. In testimony whereof I ax my signature in presence of two witnesses.

JOSEPH TOMLINSON. Witnesses:

J. M. ST. JOHN, J. F. GROAT.

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