US671923A - Bridge superstructure. - Google Patents

Description

No. 67l,923. Patented Apr. 9, Mil. R. PETERSEN.

BRIDGE SUPEBSTRUCTURE.

(Application filed July 81, 1899. (No Model.) 3 Sheets-Sheet l.

mi norms PETERS ca. mo'ro-Lm-m, WASHINGTON a c.

N0. 67!,923. Patented Apr. 9, [90L R. PETERSEN.

BRIDGE SUPEBSTBUCTUBE.

(Annlication filed July 81, 1899.)

(No Model.) 3 Sheets-Sheet 2.

2% 5 B l -M7" No. 67I,92-3. Patented Apr. 9, mm.

B. PETERSEN.

BRIDGE SUPERSTRUCTURE.

(Application filed July 31, 1899.)

(No Model.) 3 Sheets-Sheet 3.

Wat 26556.5;

wagz

m: Mamas vmns ca. PNUYO-UTHO" wAsHma cm 04 c.

UNITED STATES RICHARD PETERSEN, OF

PATENT OFFICE.

ELBERFELD, GERMANY.

BRIDGE SUPERSTRUCTU RE.

To all whom it may concern.-

Be it known that I, RIO ARD PETERSEN, a subject of the German Emperor, residing at 168b Konigstrasse, Elberfeld, in the Kingdom of Prussia, Germany, have invented certain new and useful Improvements in Bridge Superstructures; and I do hereby declare the following to be afu'll, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

-My invention relates to improvements in bridge superstructures, and in particular to a bridge superstructure normally intended to carry its main load unsymmetrically with the line of gravity of the said main load outside the main truss.

Under the present practice of bridge-building conditions sometimes arise compelling the use of a narrow main truss, which of necessity not only receives its main load unsymmetrically, but so unsymmetrically that the line through the center of gravity of said main load falls outside the said main truss. Such a condition arises, for example, when a double-track railway-bridge must be built with a truss narrower than the distance between the inside rails of the two tracks.

In all the forms of bridges hitherto known to me a condition such as above set out would require a large increase in the amount of material employed, because when, for example, a train was crossing the bridge on one track the longitudinal vertical main girder would be subjected to a greater strain than it would be if two trains each equal in weight to the one above mentioned were crossing the bridge at the same time on the two tracks. Such an increase in weight of material is dis advantageous not only in cost of construction, but also because it tends to limit the span length.

The object of my invention is to avoid these disadvantages in a bridge superstructure of the class described, while at the same time giving a construction in which all the necessary calculations may be practically applied for determining the strains and the sizes of the difierent members of the superstructure.

With this object in view my invention, broadly considered, consists of a bridge su- Patent No. 671,923, dated April 9, 1901.

Serial No. 725,618. (No model.)

perstructure com prising a tubular main truss having a rectangular cross-section, and brackets extendinglaterally beyond the main truss and carrying the roadway for the main load.

More specifically considered, my invention consists in a bridge superstructure having a tubular truss formed of two vertical girders and two horizontal girders having their chords in common-that is to say, the upper chord of the left-hand vertical main girder serves as the left chord of the upper horizontal main girder, the lower chord of the said left-hand vertical girder serves also as the left chord of the lower horizontal main girder, and so on, the tubular truss thus formed carrying brackets which extend laterally beyond the truss and support the roadway for the main load.

A further feature of my invention consists in a structure, such as above pointed out, having cross-braces at the two ends of the structure, and, finally, having crossbraces intermediate the said end cross-braces, if so required.

My invention will now be more specifically described in connection with the accompanying drawings and then particularly pointed out in the claims.

In the drawings, Figure 1 represents a transverse view at the abutment of a bridge embodying my invention in that specific form in which a cross-brace is employed at the end of the main truss. Fig. 2 is a similar view taken through the bridge at a point intermediate the bridge ends; Fig. 3, a side view of a portion of the bridge; Fig. 4, a plan view of the same, the floor structure being removed; Fig. 5, a diagrammatic perspective of a bridge embodying my invention, made with trussgirders as distinguished from plate-girders; Fig. 6, a transverse view of a modified form of bridge embodying my invention which is applicable where for some reason the height of the bridge is limited; Fig. 7, a transverse view of a little more than half of a carriage and footway bridge made up of four independent superstructures each embodying my invention; Fig. 8, a transverse view of another form of bridge embodying my invention, this construction being specially intended for carrying a single-rail suspended railway. Figs. 9 to 13 are diagrammatic views in ex- P (l %),while the right vertical main girder A-B is subjected to the upward strain P In any case the load on the adjacent vertical main girder due to the unsymmetrical loading is greater than if double the loadviz.,

2 P-was placed symmetrically on the bridge, since in the latter case neither vertical main girder would have agreater load upon it than P. Consequently it is very irrational to construct the ordinary form of bridge with such a small distance between the two vertical main girders as is indicated in Fig. 9, and. where conditions compel such a construction itis absolutely necessary, as is obvious to those skilled in the art, that the vertical main girders shall be made of heavier material than if the bridge was intended to carry only a symmetrical load of double the amount. however, the construction shown in Fig. 10, which illustrates my invention, is considered, it will be noted that the load P, located at one side, is shifted over to the adjacent vertical main girderA-B,and that in consequence of this shifting the two horizontal main girders A-A B-B' each receive the stressesP If now the bridge is considered as consisting of four girders independent of each other,

Fig. 11, and the strains calculated individually for each girder, the fact appears that the chord A, in so far as it is a constituent of the vertical main girder AB, receives a compressive strain, while as a constituent of the horizontal main girder A-A it is subjected to tension. The reverse is true of the chord B, which, asa constituent of the vertical main girder A-B, is subjected to a tensile strain, while as a constituent of the horizontal main girder B-B it is subjected to compression. My new system therefore produces the great advantage that the eccentric position of the load does not cause a greater strain on the adjacent vertical main girder than would double the same load it sym metrically placed.

When the four main girders are united by a stiff diagonalthat is, a diagonal brace which can act as a compression member, (see Fig. 12)then the distribution of the load P, acting on the bracket among the four main girders, is as follows: The load P is shifted into the axis of the main truss and distributes itself there parallel to the main girders in the horizontal strain H and the vertical strain V, each horizontal girder receiving the strain while each vertical girder receives the strain The resulting moment, P c, is

divided, as in Fig. 13, in such a manner that Pc fi and After the strains have been thus distributed among the four girders the latter are calculated separately as if they were independent of one another. Then, finally, the tensile strains of the common chords are added.

WVhile in the ordinary construction shown in Fig. 9 the distance 17 between the vertical main trusses of a two-track railway-bridge must not be less than the distance between the tracks if the loading of one track is not to produce a greater strain on the adjacent vertical main girder than double the load symmetrically located, on the other hand in my construction the said distance I) may be reduced to almost one-third of the distance between said tracks without allowing the onesided load to cause agreater strainon the adjacent vertical girder than would double the load symmetrically placed. Therefore my invention permits the construction of narrow bridge superstructures, and consequently of narrow substructures, without requiring a greateramount of material in-the main truss.

It is unimportant in my construction whether the main girders be plate-girders or trussgirders.

When in a bridge constructed in accordance with my invention the two vertical main girders are supported by the fou ndations,then the main truss must be stifiened in at least two cross-sections by diagonal cross-braces, (see Fig. 1,) while the remaining cross-sections do notabsolutely require to be provided with diagonal cross-braces. (See Figs. 2, 7, and 8.) When, on the other hand, the two horizontal main girders are also sustained by lateral supports, then all the cross-sections can be arranged, as in Figs. 2, 7, and 8, without diagonals. Furthermore, all the cross sections may be stiffened by diagonals. This is necessary when the bracket-arms do not extend from near the chords, but are arranged as shown in Fig. 6.

Referring to Figs. 1, 2, 3, 4, 6, 7, and 8, V V are the two longitudinal vertical girders, connected by the longitudinal horizontal girders H H these being shown as united to the vertical girders at the tops and bottoms of the latter by the common chords A A B B.

From the truss thus formed extend the lateral brackets, which comprise arms which carry the bridge-floor members, the said arms being near the top of the truss in Figs. 1 to 4 and 7, as shown at I, or intermediate the top ICC and bottom of the truss, as shown at I in Fig. 6, or near the bottom of the truss, as shown at I Fig. 8. The outer ends of the said bracket-arms are supported either by compression members extending from the said arms to the lower part of the respective longitudinal vertical girders V V as shown at K, Figs. 1, 2, and 7, and at K, Fig. 6, or by tension members extending from said bracket-arms to the upper part of the respective longitudinal vertical girders, as shown at K in Fig. 8. In all three constructions the two ends of the truss may be provided with cross-bracing, as is indicated at L in Fig. 1, this cross-bracing consisting of compression members which extend in an incline from one vertical girder to the opposite vertical girder. The truss may also be supplied with end and intermediate cross-bracing, as indicated in Fig. 6, in which L L are compression members and L L are tension or tension and compression members, or the intermediate cross-bracing may be like the end cross-bracing shown in Fig. 1 and above referred to.

It will be seen from the description herein-- before given that in carrying out my invention I employ a tubular truss having a we tangular cross-section-that is to say, a truss composed of four girders, two arranged horizontally and two arranged vertically. It is to be understood that I use the term girder in its specific sense-viz, as meaning a principal member of a bridge-truss intended to receive and sustain an appreciable and material proportion of the load on the truss, as distinguished from the subordinate parts of a bridge-truss, such as wind-bracing or the like, which are not intended to receive any part of the main live load.

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

1. In a bridge normally intended to carry its main load unsymmetrically with the line of gravity of the said load outside the main truss, the combination with a tubular main truss composed of two horizontal main girders and two vertical main girders having their chords in common, of brackets extending laterally beyond the respective vertical main girder, and a main-load roadway carried by said brackets.

2. In a bridge normally intended to carry its main load unsymmetrically with the line of gravity of the said load outside the main truss, the combination, with a tubular main truss having a rectangular cross-section, of brackets extending laterally beyond the side walls of the truss, a main-load roadway carried by said brackets, and cross-braces at the two ends of the main truss.

3. In a bridge normally intended to carry its main load unsymmetrically with the line of gravity of the said load outside the main truss, the combination, with a tubular main truss composed of two horizontal main girders and two vertical main girders having their chords in common, of brackets extending laterally beyond the respective vertical main girder, a main-load roadway carried by said brackets, and cross-braces at the two ends of the main truss.

4. In a bridge normally intended to carry its main load unsymmetrically with the line of gravity of the said lead outside the main truss, the combination, with a tubular main truss having a rectangular cross-section, of brackets extending laterally beyond the side walls of the truss, a main-load roadway carried by said brackets, and diagonal crossbraces at the two ends of the main truss.

5. In a bridge normally intended to carry its main load unsymmetrically with the line of gravity of the said load outside the main truss, the combination with a tubular main truss composed of two horizontal main girders and two vertical main girders having their chords in common, of brackets extending laterally beyond the respective vertical main girder, a main-load roadway carried by said brackets, and diagonal cross-braces at the two ends of the main truss.

6. In a bridge normally intended to carry its main load unsymmetrically with the line of gravity of said load outside the main truss, the combination with a tubular main truss having a rectangular cross-section, of brackets extending laterally beyond the side walls of the truss, a main-load roadway carried by said brackets, cross-braces at the two ends of said main truss, and cross-braces intermediate said end cross-braces.

7. In a bridge normally intended to carry its main load unsymmetrically with the line of gravity of said load outside the main truss, the combination with a tubular main truss composed of two horizontal main girders and two vertical main girders having their chords in common, of brackets extending laterally beyond the respective vertical main girder, a main-load roadway carried by said brackets, cross-braces at the two ends of the main truss, and cross-braces intermediate said end cross-braces.

8. In a bridge normally intended to carry its main load unsymmetrically with the line of gravity of said lead outside the main truss, the combination, with a tubular main truss composed of two horizontal main girders, and two vertical main girders having their chords in common, of bracket-arms connected at their inner ends to the truss adjacent to the upper chord, bracket-braces extending from near the outer ends of the said bracketarms to the truss adjacent to the lower chord, and a main-load roadway located upon the bracket-arms.

In testimony whereof I have affixed my signature in presence of two witnesses.

RICHARD PETERSEN.

Witnesses W. SoHMrrz, T. GRUMMEL.

Images