US2319468A - Bridge floor - Google Patents

Description

H. NAGIN ET AL BRIDGE FLOOR Filedv April 1o, 1941 May 18, 1943 3 LESLIE C. 57E/clan No ,5m c 21M TToR/VEY Patented May 18, 1943 BRIDGE FLOOR Harold Nagin and Leslie C. Strickland, Pittsburgh,

Pa., assignors to Reliance Steel Products Company, McKeespox-t, Pa., a corporation of Pennsylvania Application April 10, 1941, Serial No. 387,850

4 Claims.

This invention relates to bridges and particularly to floors for use in bridges, and more particularly to metal bridge floors of the so called open type, which are used to directly carry the traffic unaided by fillers, such as concrete, between the assembled bars which form the oor. Our invention resides in the iloor itself, in the method of making it, and in the bars employed.

For certain purposes and under certain traffic conditions the tramo supporting roadway is advantageously constructed of metal open mesh gratings laid directly over a skeleton supporting structure, such as the sills or stringere of a bridge. The roadway is formed from gratings made in units or slabs which when placed in position on the supports are secured to form a continuous structure. Each unit is commonly made of spaced-apart metal bearer bars which span the space between the stringers or sills, the bearer bars being fastened together by transverse metal cross bars adjacent the tops thereof, and by tension distributing bars connecting the bottoms of the bearer bars. Such a grating or ooring is used without a filler between the various bars and presents a cell-like surface to the traffic. 'I'he flooring is substantially skidproof, is resistant to wear, is self-cleaning, and is the lightest typev of flooring known. The lessened dead weight enables a lighter supporting structure to be used, and consequently the total cost of a bridge in which this flooring is used may be less than when a solid floor is employed, which utilizes a filler of concrete or other materiai between the bars.

The openings in an open type fioor must not be too large, as vehicular traffic will not smoothly pass over such openings. To provide a satisfactory opening the space between adjoining bars should not `substantially exceed about two (2) inches and preferably the distance between the bars transverse to the direction of trailic flow should be somewhat less than two (2) inches.

It is customary to design open oors so that the main bearer bars transmit the trailic loads to the stringers and since deflection should be at a minimum the main bearer bars to be economical should be as deep as possible. A certain minimum thickness of metal is necessary to allow for corrosion and in many instances if the bearer bars are of an economical size and spaced close enough for smooth passage of tramo, the resulting structure will be unnecessarily strong. unduly heavy and too costly. If only a sufficient number of bearer bars are used to carry the load and prevent undue deflection and intermediate parallel bars of lesser size and weight are included to control the size of the openings, the resulting structure will be free from the aforementioned objections. Our invention utilizes this arrangemen-t.

It is desirable to secure the bearer bars, the intermediate bars and the cross bars together by welding. Due to the large number of joints necessary to secure the various bars together and maintain the desired size of the openings, hand .welding of such joints is quite expensive. Furthermore, handwelded joints, whether the weld be made by gas welding or by electric arc welding, cannot be satisfactorily galvanized. We have found that the joints can be satisfactorily, expeditiously, and cheaply made by pressure electric resistance Welding; and this discovery is one of the features of our invention.

The problem of skidding is of concern where the material presented to the modern day traffic is metal. The cellular or reticulated ooring of the open type provides good anti-slip qualities. We have found that the anti-slip or anti-skid qualities can be considerably enhanced by serrating the top of the bearer bars, especially in view of the fact that the most satisfactory design of bearer bars includes a bulbous head. It is also within r:ontemplation of our invention to serrate, if desired, the top surface of the intermediate bars and the top surface of the cross bars. Serration of all three bars will provide the maximum anti-skid properties, but very satisfactory results can be expeditiously obtained and at no extra cost by serrating only the tops of the bearer bars.

By the use of our invention, the open steel deck iiooring can be economically designed and fabricated, and it possesses superior skid resistant qualities. By the use of such a deck, the supporting structure therefor can be lighter and consequently cheaper, and the structure as a Whole is more satisfactory than any heretofore erected. The new type of bearer bar has superior properties.

In the accompanying drawing where we have shown for purposes of illustration only the present exemplary embodiments of our invention:

Figure 1 is an end view in elevation of a part of a unit or slab resting on a support, generally along the line I-I of Figure 2,

Figure 2 is a cross-sectional view along the line II-II of Figure 1,

' Figure 3 is a fragmentary detail of a suitable top cross bar, ready for assembly,

Figure 3a is a fragmentary detail of another suitable cross bar,

Figure 4 is a fragmentary detail of a suitable bearer bar ready for assembly,

Figure 5 is a cross sectional view along the line V-V of Figure 4, but to an enlarged scale,

Figure 6 is an end view in elevation of a portion of a modied unit,

Figure 7 is a cross section of a modied cross bar, and

Figure 8 is an end View in elevation of a portion of still another unit.

In the drawing wherein like reference numerals represent like parts in the various views, the numeral I represents a supporting structure such as the stringer of a bridge. on which the floor is laid. The grating or iioor is made from bearer bars II, which are placed parallel to one another and laid across the stringers I0, intermediate bars I2 laid parallel to and between the bearer bars, cross bars I3 intersecting the bearer bars and intermediate bars and joined thereto, and tension distributing bars I extending between and laced through the bearer bars above the bottom anges thereof. The cross bars are less in depth than the bearer bars and the intermediate bars are less in depth than the cross bars.

Each bearer bar II has a head portion I5, having an umbrella like contour, a flange portion I6, and a web portion I7 narrower than the rest of the bar connecting the bulbous head I and the flange I6. The head portion I5 (see Figure 5) has sides which flare sharply outwardly and extend upwardly from the top of the web, and

a top portion from which a number of projections I 8 extend upwardly and longitudinally of the bearer bar. In Figure 5, I have shown five projections which vary in height, so that the center one 'is somewhat higher than those nearer the sides, and the projections nearest the sides are lower than any of the others. Of course the projections or ribs can be fewer in number but should not be less than two. So also the projections could be arranged so that the tops thereof lie in the same plane, or the top of center projection could be lower than that of the projections nearer the sides. We have found that a bearer bar having the dimensions approximately as follows provides suitable proportioning; height 5 inches, width of head 1 inch, height of head 1/2 inch, height of center rib 1% inch, height of edge projections 1/8 inch, thickness of web 1A; inch, width of iiange 1 inch, depth of ange inch. VThe intermediate bars can conveniently be 1/2 inch round. If desired the top portion of the intermediate bearer bars could be serrated. These dimensions are illustrative only. Such bearer bars are conveniently spaced for modern heavy traiiic loads about 5 inches center to center.

The cross bars I3 are preferably of rectangular cross section and have recesses I9 notched in the upper edges, and spaced apart the same distance as are the bearing bars. The recesses I9 are shaped so that they are Just slightly smaller than the sloping portions of the bearer bar heads with which the sides of the recesses will contact when the grating is assembled. This will ensure that the sloping sides of the recesses will closely abut and firmly weld to thesloping sides of the bearer bar heads. The bottom portion I9' of each recess is about the same width as the web thickness and extends a short distance into the cross bar.

In Figure 3a there is shown a cross bar I3c in which the recesses I9c are rectangular in shape. The recesses are wider than the thickness of the web llc of the bearer bar llc (shown in dotted lines), and about the width of the head I5c midway between the top and bottom thereof. When a cross bar of this type is pressed into position, the upper portions of the side walls of the recesses are partly forced into the sloping sides of the head and welded tightly and intimately thereto.

The bearer bars II are each provided with slots 2li spaced apart a distance to accommodate the desired spacing of the cross bars. A satisfactory distance is about 2 inches center to center. The top of the notch may conveniently be about 1/4 inch below the junction of the head I5 and the web I7 of the bearer bars. The slot 20 is large enough to snugly embrace the cross bar I3. Adjacent the lower portion of the slot is a lug 2l struck outwardly from the web I1. The lug and the slot are so positioned and dimensioned that when the cross bar is in the position shown in the completed structure illustrated in Figure 1 the lug 2l can be folded back into the slot 2li so as to iill up that portion of theslot which is left open when the 'cross bar I3 has been raised to nal position, in which the top of the cross bars and the tops of the bearer bars are in substantially or nearly the same place. The tops of the cross bars may be serrated if desired.

The lower portions of the bearer bars are secured in spaced relation by the tension distributing bars I4 which are laced through appropriate openings in the webs of the bearer bars just above the flange portions. A convenient size for such tension bars is about 1% inch square and spaced about 18 inches apart. If desired, the cross bars I3' may be wedge shaped as shown in Figure '7. Where such bars are used the slot 2U in the bearer bars should likewise be wedge shaped, so as to closely embrace the wedge shaped cross bars. Such a section I3' in some instances ensures better pressure electric resistance welding. The notches similar to those shown in Figure 3 are provided in the thinner edge.

In the modification shown in Figure 6 the bearer bars IIa have only three projections IBa extending upwardly from the head portion I5a and the tops thereof are in substantially the same plane. The recesses I9a of the cross bars I3a are so proportioned that there are spaces 22 between the sides of the recesses and the sides of the bearer bar heads I5a. The spaces 22 somewhat increases the resistance to skidding of the traflic engaging surface of the floor. Otherwise the grating is similar to that already described and is similarly made.

In Figure 8 there is shown a modified structure which may be entirely constructed by electric pressure resistance welding. The bearer bar IIb has a welding rib 23 projecting downwardly from the flange IBb to which the tension distributing bar Mh is pressure electric welded. The bar Nb' is preferably of greater depth than the height of the rib 23 and projects below it. This utilizes the strength of the tension distributing bar to its greatest'extent and also provides a skid' or runner which is of aid in handling the unit. Hand welding is entirely absent in this floor.

As hereinbefore stated, the bearer bars cannot be disposed closely enough together to economically provide cells of desirable size for smooth travel of the traffic. We therefore space the bearer bars Il widely enough apart to economically employ their physical characteristics, and to provide a desirable cell dimension we use intermediate bars I2, spaced between and parallel to the bearer bars. The intermediate bars are joined to the cross bars and the tops of all the various bars lie in the same plane or in closely adjacent planes. Where the bearer bars are spaced say inches center to centerVone intermediate bar about 1A), inch in diameter is sufficient between each pair of bearer bars, although more could be used. In any event, sufficient intermediate bars of a desired size should be provided so that the distance between the-various bars which define one dimension of the cell should not substantially exceed that which is desirable, e. g. about 2 inches. 'I'he other dimension of the cell is taken care of by the spacing of the cross bars.

Heretofore in structures of this general kind it has been the practice to join all of the bars by ordinary hand welding, either by use of gas welding or electric arc welding. This, due to the desirable close spacing of the various component bars, required a large number of welds per square foot, which is very expensive and besides the hand'welding even when performed by skilled operators is unsightly, and the progress of the work is slow. We have discovered that the bars forming the traffic surface can be joined cheaply, expeditiously, and in a sightly manner by pressure electric resistance welding. We assemble the bearer bars and cross bars so that the cross bars are pressure electric resistance welded to the bearer bars while the bearer bars are upside down. After this operation the intermediate bars are pressed'into and secured to the cross -bars by pressure electric resistance welding.

Lastly, the tension distributing bars are placed and secured, either to the bottom of the bearer bars or adjacent thereto. Where the tension distributing bars are laced through the appropriate openings in the lower part of the bearer bars as shown in Figure 1 they are hand welded to the bearer bars, after they are properly assembled. Where a bearer bar like that shown in Figure 8 is used, the tension distributing bar Mb is secured to the welding rib 23 by electric pressure resistance welding.

By using pressure electric welding, the process of assembling is greatly shortened and the costs of joining the bars are greatly reduced, and a more satisfactory job results. If a galvanized coating is used it will be of uniform color and have uniform corrosion resistance characteristics. These desirable features cannot be obtained where hand welding is resorted to.

The bearer bars which we have illustrated are economical in distribution of material. The head of the bar is shaped to facilitate pressure electric welding and offers a substantially skid-proof surface to the traiiic. One form of the bar also provides a welding rib, which enables the tension bar to be pressure electric welded into the structure.. The bearer bars may be formed by any method, such as by rolling or by extrusion. The projections or ribs I8 may run longitudinally of the bar,

transversely, or even diagonally. AIn the finished structure the cross bars may lie above, flush with or below the top surface of the heads of the bearer bars.

It is to be understood that structures of the type described can be used not only for open type bridge floors, but also for surfacing runways, vault covers, loading platforms and even in reinforced concrete structures. The dimensions herein given are illustrative, as it is apparent that the various dimensions depend on the loads to be carried, the smoothness of travel desired, the physical characteristics of the metal used, and the ideas of the designer.

While we have shown and described several specific preferred embodiments 'of the invention, it will be understood that we do not desire to be limited precisely thereto, and that various modiiications may be made within the scope ofthe following claims.

We claim as our invention:

1. In the method of fabricating a metal structural assembly consisting of bearer bars having a web portion and an adjoining head portion of greater thickness than the web portion, intermediate bars and cross bars, the head portion having integral longitudinally extending ribs extending upwardly from the top thereof, the steps which consist of placing a vertical slot in the web portion below the head portion, passing a cross bar having cut out portions of such shape as to embrace the web portion and the sides of the head portion, uniting the bearer bar and the cross bar by electric pressure resistance welding, so that the top edge of the cross bar lies adjacent the top edge of the bearer bar, and then uniting at least one intermediate bar by electric pressure resistance Welding to the cross bars in a position parallel to and between the bearer bars and thereafter pressure electric resistance welding a tension distributing bar to the bottom of the bearer bars so that the bottom of the tension distributing bar remains below the bottomof the bearer bars.

2*. In a structural assembly of metal bars, bearer bars each formed of a rolled section of metal having a base iiange and a head and a web joining the flange and the head, the sides of the head aring outwardly and upwardly from the web portion, the top of the head having longitudinally extending ribs projecting upwardly therefrom, cross bars of less depth than the bearer bars secured to the bearer bars by pressure electric resistance welding and terminating adjacent the upper surfaces of the bearer bars, and intermediate bars of less depth than the bearer bars pressure electric resistance welded to the cross bars parallel and ,between the bearer bars, the tops of the intermediate bars and the tops of the cross bars being in substantially the same plane.

3. In a structural assembly of metal bars, bearer bars each formed of a section of metal having a base flange and a head and a webJ joining the flange and the head, the sides of the head ilaring outwardly and upwardly from the web portion, the top of the head being serrated, a welding rib projecting downwardly from the bottom of the flange, cross bars of less depth than the bearer bars secured to the bearer bars by pressure electric resistance welding and terminating adjacent the upper surfaces of the bearer bars, intermediate bars of less depth than the bearer bars pressure electric resistance welded to the cross bars parallel and between the bearer bars, the tops of the intermediate vbars and the tops of the cross bars being in substantially the same plane and tension distributing bars welded to the ange ribs, the bottoms of the tension distributing bars lying below the ribs.

4. In a structural assembly of metal bars, bearer bars each formed of a section of metal having a base ange and a head and a web joining the ange and the head, the sides of the head Haring outwardly and upwardly from the web portion. cross bars of less depth than the bearer bars pressure electric resistance welded to the bearer bars, said cross bars having recesses therein of the thickness of the web, the top of the recesses flaring outwardly suilciently to leave a space between the sides of the recess and the sides of the head, the recesses being spaced apart the distance apart of the bearer bars, intermediate bars pressure electric resistance welded to the cross bars between and parallel to the bearer bars and of less depth than the cross bars, the top surfaces of all 5 bars lying in substantially the same plane.

HAROLD NAGIN. LESLIE C. STRICKLAND.

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