US1946049A - Plate girder - Google Patents

Description

Feb. 6, 1934. w. VVEISKQPF AL 1,946,049

PLATE GIRDER Filed Oct. 8.- 1931 2 Sheets-Sheet l INVENTORS 170MB Wait E0 01? Jbba/ WPikwortb;

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Feb. 6, 1934. w wElSKOPF r AL 1,946,049

PLATE GIRDER Filed Oct. 8. 1931 2 Sheets-Sneet, 2

INVENTORS nzmzzm 1:

ATTORNEY lay:

Patented Feb. 6, 1934 UNITED STATES PLATE Walter H. Weiskopf, Cedarhurst, and John Pickworth, Bronxville, N. Y.

Application October 8,

3 Claims.

Our present invention relates generally to structural elements, and has particular reference to plate girders.

The design of beams is, of course, predicated 5 primarily upon the maximum load which is to be supported, and the general objective of the structural engineer is to provide a beam having strength characteristics suflicient to carry the predetermined load and having a structural arrangement which is as economical as possible.

Economical design requires more than merely keeping the total weight of material to a minimum, since the designer is restricted, from a practical standpoint, to the employment of I- I beams, angles, and other structural elements of a character which are readily and inexpensively available on the market.

In the conventional type of plate girder, a single web plate is usually associated with a flange consisting essentially of a pair of angles riveted to one edge of the web plate. The flange may thus be considered to be substantially T-shaped in nature, with the T provided with two depending stem portions between which the web plate is sandwiched. Sometimes, the flange includes one or more cover plates which are incorporated into the flange construction by means of rivets passing through the cover plate or plates and through the laterally disposed legs or flanges of the two angles referred to.

Where the design of a structure makes it desirable, or, in certain instances, essential, for the beam to have a so-called clear flange, viz., a flange whose outer surface is substantially smooth and devoid of irregularities or projections such as rivet heads, the conventional type of plate girder can be employed only by eliminating the use of cover plates entirely; or, where one cover plate is used, by chipping the rivet heads which tie such plate to the angles of the flange. Where a plurality of cover plates are used, the provision of a clear flange is made even more diificult by 45 virtue of the irregularities or steps which are created at the ends of the cover plates, since such plates are usually not coextensive in length.

It is a general object of our present invention to provide a structural composite beam of the "plate girder variety which is equivalent, if not superior, in strength and load-carrying capacity, to the conventional type of plate girder which includes one or more cover plates; and our present beam is of a character which permits a clear flangeto be provided, if desired, without any GIRDER 1931. Serial No. 567,580

sacrifice in economy of design, assembly, or installation.

The provision of a clear flange by means of the conventional type of plate girder where cover plates are entirely omitted is usually diificult and unieasible for the reason that two angles alone are usually insufficient to provide a flange of the requisite strength. Although, theoretically, this lack of strength could be compensated for byincreasing the depth of the beam as a whole, theincrease in depth that would be ordinarily necessary is usually of such magnitude as to make such a beam utterly unsatisfactory from a practical standpoint. I

By means of our present invention we are enabled to provide a clear flange, without any sacrifice in strength, and possibly with an increase in strength, upongirders which are no deeper than those which have heretofore been constructed in the conventional manner. In fact, without any increase in depth our present beam is equal, and possibly even superior in strength, to the conventional plate girders which employthe maximum available angle sizes and the maximum practical number and thicknesses of cover platesj In addition to the fact that our present invention provides a beam having a clear flange, without any sacrifice in depth or strength, our present beam is more economical than beams of the conventional character. In carrying out our present invention fewer rivets are required, less additional material must be employed to compensate for rivet holes, and fewer pieces are to be handled during fabrication.

The clear flange construction of our present invention is of particular value in cases where a direct vertical load is imposed upon the beams, as in certain bridges, and in grillages. It is, therefore, a further object of our present invention to provide an improved type of grillage, and a novel and improved type of bridge construction.

We achieve the foregoing objects, and such other objects as may hereinafter appear or be pointed out, in the manner ilustratively exemplified in the accompanying drawings, wherem- Figure 1 is a fragmentary perspective View, partly in cross-section, of a plate girder constructed in accordance with our present invention;

Figure 2 is a cross-sectional view of a slightly modified construction;

Figure 3 is a cross-sectional view of a grillage employing one type of our present girder; and

Figure 4 is a cross-sectional view of the essential portions of a railroad bridge construction involving another type of our present girder.

One of the main features of our present invention lies in providing a structure wherein the flange is a substantially T-shaped, preferably composite, member wherein the cross-bar of the T is provided with at least three depending stems. In the drawings, we have illustrated a preferred construction wherein the T has three stems.

In Figure 1, for example, it will be noted that the flange is composed of the medial, T-shaped member 10, and two outer members 11 and 12, the latter being arranged on opposite sides of the T-stem 13, respectively, and spaced from this stem. It is further to be noted that the medial member is an integral element of T-shaped cross-section, the cross-bar 14 having a substantially plane and smooth upper surface. The outer members 11 and 12 are preferably angles, each of which has one leg or flange arranged parallel to the T-stem 13 and the other leg or flange arranged substantially parallel to the cross-bar 14 of the medial member 10. V

The members 10, 11, and 12 constitute the composite flange of our present girder, and it is to be observed that this composite flange is substantially T-shaped and embodies three spaced stem portions. The elements of this flange are tied l to the web by means of rivets 15 which extend T-stem 13.

hrOugh the stem portion 13 of the medial member In the embodiment illustrated in Figure 1, the main or central stem of the flange is appreciably longer than the outer stems formed by the outer members 11 and 12.

To connect the two flanges of the beam of Figure 1, our invention calls for the employment of at least two Web plates arranged in parallel, spaced relationship on opposite sides of the For example, we have shown two web plates 16 and 17 arranged in alternate lapped relationship with the three depending stem portions of the substantially T-shaped flanges. The rivets 15, which are illustratively arranged in two staggered rows in Figure 1, serve to tie the flanges to the web. It is to be noted that each of these rivets is in multiple shear along four planes.

If desired, additional rivets may be caused to extend through the elongated, medial stem 13 and through the web plates 16 and 17. Each of such rivets would be in double shear.

By means of this simple and compact and obviously inexpensive construction, a plate girder is provided which has great advantages.

In Figure 2, we have illustrated a slightly modified type of construction wherein the medial stem 18, formed as an integral dependency of the medial, T-shaped member 19, is substantially no greater in length than that of the outer stem portions 20 and 21, the latter being provided by the employment of angular outer members tied to the medial member 19 by means of rivets 22. In this construction, two web plates 23 and 24 are employed as in Figure 1, and we have shown the possibility of employing only one row of rivets to tie the elements of the composite flange to the composite two-plate web.

It is to be noted that the top surface of each flange, in Figures 1 and 2, is entirely devoid of rivet heads, and since the medial, T-shaped flange member is always coextensive in length with that of the beam itself, a completely clear flange may be provided without any of the difficulties or problems hertofore encountered in endeavoring to provide a clear flange by the conventional type of plate girder.

In Figure 3, we have illustrated, by way of example, a typical employment of girders of the present character as sleepers in a grillage. We have illustratively shown three girders arranged side by side upon a foundation 26 and adapted to support the customary type of billet 27, which serves as a footing for a structural column 28 or other load.

Each girder has a flange composed of the medial, T-shaped element 29 and the two outer members 30 and 31, each of the latter being provided in the form of an angle. The elements of the flange are fastened to the web by means of the rivets 32 passing through the three depending stem portions of the flange and through the two web plates 33 and 34 which are disposed in alternate relationship with these stem portions.

The medial stem portion 35, formed integrally as a part of the element 29, is substantially longer than the outer stem portions; and at the base of each of the girders illustrated we employ two additional rows of rivets 36 which extend through the web plates 33 and 34 and through the medial stem 37 of the lower flange. These extra rows of rivets are of great advantage in assisting the transmission of the vertical load to the foundation 26.

The construction illustrated in Figure 3 is sub stantially like that of Figure 1, except that the free flanges of the outer angles 30 and 31 are disposed in close, substantially contacting relationship to the under surfaces of the cross-bar of the medial member 29 of each flange.

The absence of any connection between the elements of each flange, other than the rivets which extend through the medial stem portion, results in the provision of the desirable clear" flange, the advantages of which are obvious in Figure 3. The smooth and substantially flat, exposed surface of each of the lower flanges facilitates grouting under the girders, as indicated at 38; and the support of the billet 27 is greatly facilitated because no countersinking of rivet holes, or chipping of rivet heads underneath the billet, is necessary. I

It might be mentioned that the employment of our present type of girder in a grillage, as illustrated in Figure 3, is of further advantage by virtue of the increased stability and rigidity of the lower flange. The conventional type of plate girder frequently requires stiifeners for the lower flange, especially because of the tendency of the lateral portions of the flange to bend or buckle. The present flange structure is of a peculiarly rigid and staunch character which requires no such additional stiffening means.

In Figure 4, we have illustrated, by way of example, a further typical and advantageous employment of girders of the present character. Two girders are herein illustrated in spaced relationship, and are designed as elements of a railroad bridge. The railroad ties, such as the tie 39, are arranged transversely across the spaced girders and support the rails 40 in the usual manner. The free and smooth upper surfaces 41 of the flanges of the girders are of great advantage in permitting the ties 39 to be supported without any necessity for countersinking the ties. All of the ties that are necessary may be constructed in a uniform manner, preferably with a slight depression wherever the tie is adapted to rest upon and engage over the flange of one of the girders.

In this embodiment, the construction is slightly modified in that the outer members 42 and 43 of each flange are formed of angles arranged in the reverse manner from that in which they are shown in the other figures. A medial T-shaped member 44 is provided, as before, the integral stem 45 thereof being disposed between the web plates 46 and 47 and constituting the medial stem portion of the composite flange. The outer stem portions of the flange are composed of the two legs 48 and 49 of the angles 42 and 43, respectively, these legs being arranged parallel to the medial stem 45 on opposite sides of the latter. The free legs 50 and 51 of the angles 42 and 43, respectively, are, as before, arranged substantially parallel to the cross-bar of the T member 44, but are spaced from the later by a substantial amount by virtue of the reversed arrangement of the angles 42 and 43. The three elements of the flange are tied to the web plates 46 and 47 by means of the rivets 52.

The arrangement of the angles in the manner shown is advantageous for the reason that all parts of the structure are conveniently accessible to receive periodic protective coatings such as paint, and also for the reason that the cross members 53 of the bridge structure, forming part of the bracing between the two girders may be conveniently secured at their opposite ends to the free legs of the angles, for example, to the leg 50 at the left of Figure 4.

In the construction illustrated in Figure 4, each upper flange is secured to the web by an additional row of rivets 54 which extends through the medial stem 45 and through the web plates 46 and 47. These extra rivets aid in carrying the loads and transmitting them into the webs of the girders.

Although our invention is not restricted to any specific means for providing the several elements of the structure, we might mention that the medial, T-shaped elements of each flange construction are conveniently obtainable by splitting a rolled L-beam section of the character available on the market. The great variety of shapes which are rolled and so available provides a wide range from which a selection may be made. A wide or narrow cross-bar, or a long or short T- stem, may be obtained by selecting the proper beam or column section to cut or split.

It will thus be seen that we have provided a girder of simple yet economic design, having great riveting capacity between flange and web, having all of the flange material directly connected to the web, effecting a large saving in material and labor by eliminating a large amount of riveting heretofore required, and of a character which makes the present girders particularly applicable to cases requiring either a clear flange, an improved capability of transmitting loads from flange to web, or both. We attribute these advantages mainly to the provision of a substantially T-shaped, composite flange wherein at least three spaced stem portions are provided and wherein the middle stem or stems are integral with the cross-bar of the T. Preferably, though not necessarily, the medial element has a stem which is somewhat longer than the outer stems; and, preferably, though not necessarily, the outer stems are provided by the employment of outer members in the form of angles which are tied to the web by rivets extending through the medial stem portion.

Obviously, changes in the details herein described and illustrated for the purpose of explaining the nature of our invention may be made by those skilled in the art without departing from the spirit and scope of the invention as expressed in the appended claims. It is therefore intended that these details be interpreted as illustrative, and not in a limiting sense.

Having thus described our invention and illustrated its use, what we claim as new and desire to secure by Letters Patent is- 1. In a plate girder, a pair of opposite flanges each of which comprises an integral, T-shaped member, and a pair of outer members on opposite sides of the T-stern, respectively, and spaced from the latter; a web connecting the flanges and comprising two spaced plates arranged, respectively, in said spaces; and rivets binding together a the outer members of each flange, the web plates, and the corresponding T-stem; each pair of outer members being secured in position only by means of said rivets.

2. In a plate girder, a pair of opposite flanges each of which comprises an integral, T-shaped member, and a pair of outer members on opposite sides of the T-stem, respectively, and spaced from the latter; a web connecting the flanges and comprising two spaced plates arranged, respectively, in said spaces; and rivets binding together the outer members of each flange, the web plates, and the corresponding T-stem; each pair of outer members being secured in position only by means of said rivets, each of said outer members comprising an angle element having one leg parallel to the corresponding T-stem.

3. In a plate girder, a pair of opposite flanges each of which comprises an integral, T-shaped member, and a pair of outer members on opposite sides of the T-stem, respectively, and spaced from the latter; a web connecting the flanges and comprising two spaced plates arranged, respectively, in said spaces; and rivets binding together the outer members of each flange, the web plates, and the corresponding T-stem; each pair of outer members being secured in position only by means of said rivets, each of the outer members of at least one of said flanges comprising an angle element having one leg parallel to the corresponding T-stem with the free edge of said leg directe toward the cross-bar of said T.

WALTER I-I. WEISKOPF. JOHN W. PICKWORTH.

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