US424427A - Bridge construction - Google Patents

Description

(No Model.)

H. E. MERTENS. BRIDGE CONSTRUCTION.

No. 424,427. Patented Mar. 25, 1890...

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UNITED STATES PATENT OFFICE.

HENRY E. MERTENS, OF ST. PAUL, MINNESOTA.

BRIDGE CONSTRUCTION.

SPECIFICATION forming part of Letters Patent No. 424,427, dated March 25, 1890.

Application filed October 15, 1889. Serial No. 327,132. (No model.)

To all whom it may concern.-

Be it known that I, HENRY E. MERTENS, a citizen of the United States, residing at St. Paul, in the county of Ramsey and State of Minnesota,have invented certain new and useful Improvements in the Construction of Bridges; and I do declare the following to be a full, 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, reference being had to the accompanying drawings, and to the figures of reference marked thereon, which form a part of this specification.

This invention relates to the construction of bridges; and it consists, generally, in the means employed for supporting the floorbeams with reference to the posts and in the connection between the longitudinal stringers and floor-beams.

The floor-beams of through-bridges have commonly been supported either by riveting directly to the vertical posts or by suspending the floor-beams below the lower chords of the bridge by means of hangers. YV hen supported in the first-mentioned manner, the floor-beam by being loaded will have its upper flange shortened and its lower flange lengthened, and the parts of the posts riveted to the ends of the floor-beams necessarily fol- I low this movement, whereby the posts will be deflected, and on account of the deflection will require a greater section or more material to withstand, in addition to the natural strain, the strain involved by the bending of the post, than would be otherwise required. Moreover, when so constructed the pull against the rivet-heads in the upper part of the connection between post and beam is liable to tear off the rivet-heads and render the whole construction dangerous. The same result also occurs from riveting the stringers to the floor-beams, as is the common method of construction. The load upon the stringers causes the upper flange to be shortened and the lower flange to be lengthened, thereby exerting a pulling force upon the upper rivetheads of the connection and rendering a detaching of the heads of the rivets possible.

In the case of suspended floor-beams there is generally a little space left between the lower end of the post and the top of the beam as allowance for the curvature of the beam under load, which allows the beam to jump to a greater or less extent.

My invention is designed to obviate the disadvantages herein set forth; and it consists in the general construction employed for this purpose and in various features of detail, hereinafter set forth.

The invention is illustrated in the accompanying drawings, in which-- Figure l is a partial cross-section of a portion of a bridge, illustrating the means employed for supporting the floor-beams and supporting the stringers with reference thereto; Fig. 2, a side elevation of one of the vertical posts, showing in dotted lines the means employed for supporting the floorbeams; Fig. 3, a top view of the end of a fioorbeam, showing the post in cross-section; Fig. 4-, a cross-section of the post in a plane indicated by the line 4 4 in Fig. 2 Fig. 5, an under side view of the plate which is riveted to the lower end of the post and the floor-beam, to which plate the lateral rods are attached; and Fig. 6, a cross-section of the floor-beam, showing the means employed for supporting the stringers thereto.

In the drawings, 1 is a vertical post of the form commonly used in bridges, consisting, mainly, of two channels connected by latticework, though the form is not material, having near its lower end the pin 2, to which are attached the several eye-bars 3 3, forming the lower chord and the diagonals of the bridge.

' Between the two sides of the post is formed a bracket 4, consisting of a vertical plate 5 and angle-plates 6 6, riveted together. The bracket, as an equivalent construction, may be formed of an I-beam or two channel-plates, with or without thickening-plates on one or both sides. The bracket thus formed constitutes a support for the floor-beam 7, which rests directly thereupon and is retained in place against lateral displacement by means of guide-plates 8 8, riveted either to the sides of the bracket and extending a short distance above the edge of the beam, as shown in the drawings, or riveted to the floor-beam and extending a short distance over the sides of the bracket. The bracket may rest directly upon the pin and be held in position by guides attached to the post, or it may be only riveted to the post in such a manner as to withstand the total load at the end of the floor-beam; or it may rest directly upon the pin and be held in position by being riveted to the post, which last arrangement is shown in the drawing.

The floor-beam 7 is of usual form, consisting of a flat plate of metal, constituting the web, and angle-plates attached to the top and bottom of the plate to form the flanges.

For the purpose of having the lateral strain pass through the lower flange of the floorbeam, and by this method decrease the tension in the lower flange of the beam, Iconnect the floor-beam with the bottom plate 14. To give space for the ends of the lower chordbars, the lower parts of the ends of the beam are cut away and the ends of the lower flan geplates bent up accordingly. To replace the material cut away from the floor-beam, by which the same is weakened, the floor-beam is again strengthened at the end by means of two plates 9, riveted rigidly to the same, and the top and bottom flange-plates at the points where they meet the thickening-plates 9 are bent over the same. At the extreme ends of the floor-beam two more thickening-plates 10 are riveted to the three already existing plates, so as to give sufficient stiffness against buckling of the Web and producing a sufficient bearing-surface at the bottom of the floor-beam. The lower end of this group of five plates rests upon the center of the bracket. The portion of the web extending below the lower flange-angles of the floor-beam is stiffened at its lower end by two angle-plates riveted by their vertical legs to the web and by their horizontal legs to the lateral plate 14.

Instead of having a portion of the web of the floor-beam cut away, as above mentioned, to give space for the lower chord-bars, it might be less expensive to have the end of the web of the floor-beam terminate at the point Where the cutting away begins, and shorter pieces of suitable size spliced to the ends of the web by the two thickening-plates 9 9, as shown in the drawings. It will be observed that the load upon the floor-beam 7 is borne directly by the bracket. The beam is not at any point supported by bolts or rivets, but is held in position against lateral displacement at the bottom by its connection with the lateral plate 14 at the point of support by guideplates and at the top by means of an angleplate 11, riveted to the post and secured to the beam in such a manner as to admit of the longitudinal movement of the same under load by means of bolts 12 12, passing through the angle-plate and through slots 13 in the horizontal legs of the upper floor-beam flanges. It will be noticed that upon the curvature of the beam, which takes place under load, the upper flange of the beam is shortened relatively to the distance between opposite posts, the slots 13 allowing a play of the beam upon the bolts 12 for that purpose. At the same time the portion of the beam which rests upon the brackets 4 is free to slide thereupon, thus permitting the beam to yield to any extent without the exertion of any degree of side strain upon the post.

The stringers or longitudinal beams connecting the adjacent cross-beams are supported in a manner substantially similar in principle. To the sides of the floor-beams 7, at the points where the stringers are to be located, are riveted thickening-plates for the purpose of stiffening the web and distributing the load borne by the stringers over the whole height of the beam. To these thickeningplates and the floor-beam web are riveted the brackets 16, conveniently formed of several angle and stiffening plates riveted strongly together and to the floor-beam and bearing on the lower flange of the floor-beam. these brackets rest the ends of the stringers, each end being properly strengthened by means of suitable stiifening-plates 18 and angle-plates 19, riveted thereto in such a manner that the outer faces of the angle-plates shall lie closely against the thickening-plates 20 of the floor-beam.

Through the outwardly-extending legs of the angle-plates 19 and the beam are inserted bolts 21 21, for the purpose of retaining the stringers in proper position laterally. It is to be understood that these bolts are not intended to carry any part of the load, and on this account, and for reasons hereinafter stated, are placed at some distance from the web of the stringer and preferably as near as possible to the outer edge of the flange. The object of this construction is to allow a slight parting of the upper edge of the stringer from the floor-beam by a slight bending of the angle-legs between the points of attachment or the bolts 21 when the curvature of the stringer under load takes place. The entire load is borne by the brackets, the function of the bolts being, as stated, to preserve the proper lateral position of the stringer.

In addition to overcoming the disadvantages above set forth as met with in. previous methods of construction, it may be mentioned as a constructive advantage possessed by this invention as compared with floor-beams riveted to the posts that a considerable amount of field riveting will be saved, and the well known superiority of shop riveting over field- Upon work renders this feature of great imporsame, and a bracket located above the lower chord-pin and riveted to the posts, which bracket forms a bearing-surface for the floorbeams to rest upon, substantially as specified, whereby field-riveting for supporting the floor-beam is entirely avoided.

2. In a bridge, the combination of chords,

diagonals, and posts, pin passing through the same, and a bracket adapted to form a seat or a bearing-surface for the end of the floorbeam Without being rigidly connected to the latter, which bracket rests directly on the pin, substantially as and for the purpose herein specified.

3. In a bridge, the combination of chords, diagonals, and posts, pin passing through the same, and a bracket located above the lower chord-pin and adapted to form a seat for the end of the floor-beam, and guides carried either by the bracket or by the end of the floor-beam and embracing the other of said parts, respectively, for the purpose of retaining the bearing-surface of the beam in position laterally, substantially as specified.

4. In a bridge, the combination of vertical posts, lower chord-bars, and diagonals, pin passing through the same, a bracket adapted to format seat for the end of the floor-beam,

guides mounted either upon the bracket or upon the floor-beam, an angle-plate having one of its legs secured to the post and the other resting upon the top of the fioor-beam,

and bolts passing through the horizontal leg of the angle-plateand through longitudinal slots in the flanges of the floor-beam, substantially as specified, whereby the floor-beam is restrained from vertical and lateralunovement, but allowed a longitudinal play With reference to the post.

5. A bridge having its cross-beams supported upon brackets, by Which means the bending of the posts due to the curvature of the floor-beam When loaded, is avoided, and supporting-brackets attached to the web of the floor-beam for supporting the stringers, substantially as specified.

6. The combination, with the cross-beamsof a bridge, of brackets secured to the sides thereof, stringers resting upon said brackets, angle-plates secured to the ends of the stringers, and bolts passing through the extending legs of said angle-plates and the cross-beam at a distance from the Web of the stringers,

substantially as specified, whereby the curva

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