US1568631A - Cantilever bridge - Google Patents

Description

L. H. SHOEMAKER CAN'I'ILEVER BRIDGE Jan. 5 192 1,5'685631 Filed Au ustz'r, 1924' WITORNEY Patented Jan. 5, 1926.

UNITED STATES PATENT OFFICE.

LOUIS H. SHOEMAKER, or NEW Yonx, N. Y.

' CANTILEVER BRIDGE.

Application fil -ed August 27, 1924. Serial No. 734,433.

ification. I

My improvement relates particularly t the design and method of erection of the trusses constituting the anchor arm and the cantilever arm of such bridges. The usual cantilever bridge comprises at each end a continuous truss extending from the anchorage over the main pier to an end of a central suspended span. The continuous truss referred to-is composed of an anchor arm extending from the main pier to the anchorage and a cantilever arm extending from the main pier to thesuspended span. This style of truss is very expensive in design and in erection, and it is the object of the present invention to reduce such expense. The accompanying drawings illustrate diagrammatically a cantilever bridge built in accordance with the invention.

Fig. 1 is a side elevation of the entire bridge.

Figs. 2 and 3 are side elevations illustrating successive stages in the erection.

The drawings are in diagrammatic form, the details being of common-type and well understood to persons skilled in the art.

Referring to the embodiment of the invention illustrated, an anchor arm truss, AA, is provided, of moderate depth, generally about one-sixth of the anchor span, which is the distance between the anchorage 1 and the pier 2.

This truss may be designated as the auxiliary anchor truss. The same structure will extend continuously from the pier 1 toward the center of the bridge for several panels, forming a short cantilever arm, AC, which will be designated as the auxiliary cantilever.

truss. Betweenthis and the central suspended span 3 is a truss, MO, which wetrusses.

the old design.

a convenient top chord panel point'6. A supplementary truss or'extension 7 completes the auxiliary anchor truss, AA, to the I anchorage '1;

The tie or suspension system, SS, may

be-either a wire cable or an eye-barchain and may be built as'a practically straight stay extending from the point 5 to the top of the tower and thence to the point 6 without any intermediate connection tothe auxiliary anchor and auxiliary cantilever trusses. However, for aesthetic purposes and for greater rigidity it will generally be desirable to'build it in the form. of a curve with vertical suspenders 8, connecting the corresponding points of the chain or cable with the panel points of the auxiliary A bridge of ing in material compared with the ordinary cantilever,'by eliminating the long bracing members, the heavy transverse bracing and the l long supports for top chords which are characteristic of the ordinary cantilever. The present design may be carried outwith comparatively low trusses and thus with A very great advantage in case and plicity of erection is-obtained by this inthis type shows. a great savgreater variety than vention. With the usual type of cantilever bridge design the anchor arm is erected on falsework by means of an overhead traveler operating on the top chord or by anrinside traveler operating on the floor lot the bridge. This inside traveler has to be made high enough to set the highest members and is necessarily very tall and heavy. The anchor arm having been erected, the erection of the cantilever can proceed panel by panel. In long and heavy cantilever'spans, especially, the floor of the bridge is at a considerable height above the round or river bed and the falsework supporting the anchor arm is very high and on account of the weight it supports generally has to be made of steel. -It is therefore very expensive.

ed to any other work are usually scrapped when the work is completed.

W'ith'the improved type the erection of r the auxiliary anchor and the auxiliary cantilver trusses can begin at the pier 2 and proceed in both directions by the method til porary erection bars, TB,

of balanced erection (see Fig. 2), the unbalanced weight on the anchor arm side being taken up by falsework bents, BB, of comparatively light construction. These auxiliary trusses are comparatively low, so that there are no high lifts involved in their erection, and the erection can be performed by ordinary locomotive crane equipment or light travelers operating from the floor of the bridge. The erection having proceeded to the end 4 of the auxiliary cantilever truss, AC, the erection of the main cantilever truss begins. Temporarily the first upper panel points 5 and 9 are supported by temindicated in dotted lines attached to panel points 10 and 11 of the auxiliary cantilever truss. The main cantilever truss is then attached to the suspension system at the point 5. The suspension system may be attached. to some other panel point of the main cantilever truss; in which case, of course, the latter should be completed out to the panel point inquestion and then connected to the suspension system. The tower columns and bracing, shown extending only slightly above the auxiliary trusses in F 2, are then erected to full height as shown in Fig. 3. This can be easily done as a separate operation by means of light equipment. The suspension system is then extended from its connecting point 5 to the top of the tower and thence to the connection with the auxiliary anchor truss at any desired panelpoint, such as 6. If the suspension system is formed of eye-bars it will generally be erected by supporting the elements on temporary wire rope cables.

moved so that the weight of this truss is transferred to the suspension system. The

parts may then be as represented in Fig. 3. The extension of the main cantilever truss is continued by the usual methods to the point 12, to which the suspended span is to be connected; and the auxiliary anchor truss is extended in the opposite direction, as indicated at 7 to a bearing on thetop of the anchorage.

The building proceeds in the same way from both ends to the points 12 at the center, between which finally the suspended span 8 is introduced.

Though I have described with great particularity of detail certain embodiments of my invention, yet it is not to be understood therefrom that the invention is restricted to the particular embodiments disclosed. Various modifications thereof in detail and in the arrangement of the parts may be made by those skilled in the art without departing from the invention as defined in the following claims.

What I claim is:

1. In a-cantilever bridge, in combination, auxiliary anchor arm trusses extending from the anchorage to the pier, auxiliary cantilever arm trusses connected auxiliary anchor arm trusses extending from the pier outward and main cantilever arm trusses extending outward from the ends of said auxiliary cantilever arm trusses, said auxiliary cantilever trusses serving to support said main cantilever arm trusses, and stays extending from the latter to elevated points of support over the pier and thence further inward to the auxiliary anchor arm trusses.

2. In a cantilever bridge, in combination, auxiliary anchor arm trusses extending from the anchorage to the pier, auxiliary cantilever arm trusses connectedto and continuous with said auxiliary anchor arm trusses and extending outward from' the main pier, main cantilever arm trusses extending outward l'rom the outer end panel points of said auxiliary cantilever trusses,

said auxiliary cantilever arm trusses serving to support said main cantilever arm trusses, and stays attached to upper chord panel points of said cantilever trusses and extending inward to the top of a tower on the pier and thence inward to a connection with said auxiliary anchor arm trusses at to said arm anchor arms, cantilever arms and a suspended span, supported by masonry anchorages andmain piers, auxiliary anchor arm trusses extending from the anchorages tothe main piers, auxiliary cantilever arm trusses connected to and continuous with trusses and extending inward 'to the tops of towers on the mainpiers and thence inward to a connection with auxiliary anchor arm trusses at suitable top chord panel points.

4. In a cantilever bridge truss,the combination of an auxiliary anchor arm truss, an auxiliary cantilever arm truss, a main cantilever arm truss and a suspended span supported from the outer end of main cantilever arm truss, a tower on main pier,

- a chain or cable extending from a top chord panel point of main cantilever arm truss to the top of the tower and thence to a connection With the auxiliary anchor arm truss at a suitable top chord panel point, the above described parts being separate and distinct pieces of construction connected together so as to be mutually supporting and together forming a complete truss.

5. In the erection of a cantilever bridge, the method which consists in beginning on a pier and erecting in opposite directions 10 therefrom an auxiliary anchor truss and an auxiliary cantilever truss, supporting a main cantilever truss from the end of the auxiliary cantilever truss and from stays running over a tower and down to the auxiliary anchor truss, and extending the length of the trusses thus provided as required.

In Witness whereof, I have hereunto signed my name.

- LOUIS H. SHOEMAKER.

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