US3103025A

US3103025A - Structural unit

Info

Publication number: US3103025A
Application number: US777921A
Authority: US
Inventors: Alfred A Gassner; Harry J Kahn
Original assignee: Kaiser Aluminum and Chemical Corp
Current assignee: Kaiser Aluminum and Chemical Corp
Priority date: 1958-12-03
Filing date: 1958-12-03
Publication date: 1963-09-10
Anticipated expiration: 1980-09-10

Description

p 1963 A. A. GAssNER ETAL 3,103,025

STRUCTURAL UNIT- 2 Sheets-Sheet 1 a QN OM. QN

Filed Dec. 3, 1958 VENTORS NER mm. KAHN IN A RED A.GASS

THEIR ATTORNEYS A. A. GASSNER ETAL 3,103,025

STRUCTURAL UNIT 2 Sheets-Sheet 2 INVENITORS ALFRED A. GASSN ER HARRY J. KAHN THEIR ATTORNEYS Sept. 10, 1963 Filed Dec. 3, 1958 United States Patent 3,163,025 STRUCTURAL UNIT Alfred A. Gassner, New York, and Harry J. Hahn, Fresh Meadows, N.Y., assignors, by rncsne assignments, to Kaiser Aluminum & Chemical Corporation, Oakland, fialiih, a corporation of Delaware Filed Dec. 3, 1958, Ser. No. 777,921 12 Claims. ill. 14-1) The present invention, generally, relates to improvements in structural members and particularly to lightweight structures for forming bridges, derricks and the like, the elements of which can be prefabricated readily and transported for assembly at the site.

For bridges it is necessary to take into consideration the structural dead-weight of the bridge itself in addition to the loads or stresses to which it is subjected in determining its structure and safety factors. A large proportion of the load-carrying capacity of a bridge made of structural steel and concrete is used for supporting the dead weight of the bridge, and as the length and/ or Width of the bridge is increased, an even greater proportion of the load-carrying capacity'rnust be utilized to support the dead weight of the bridge. Moreover, in conventional steel bridges, each girder or beam must Withstand any load applied to it independently of the other beams, so that the size and strength of the girders or beams is very great.

In accordance with the present invention, a load'carrying structure is formed of a relatively small number of easily prefabricated parts of such weight and dimensions that they may be transported readily from a place of fabrication for assembly at a site. A load-carrying structure produced in accordance with the present invention includes a plurality of hollow beams of generally triangular cross-section positioned side by side in a substantially parallel relationship with the apices facing in the same direction. The corner pieces of adjacent beams are attached in an unique manner, which will be described in greater detail hereinafter, so that one side of each beam is disposed in a substantially parallel plane with a similarly disposed side of each other beam. A sheet or sheets of light-weight metal, such as aluminum or an aluminumbase alloy, join adjacent apices to strengthen and stiffen the structure and distribute the stresses on the respective structural elements so that the load-carrying capacity of the structure is at least equal to that of a conventionally constructed load-carrying structure of far greater Weight. Inasmuch as sheet metal of the type indicated is capable of withstanding substantial compression or tension stresses when adequately supported against buckling, a very strong load-supporting structure of relatively light weight can be produced by using sheet metal in combination with the reinforcing elements at suitable locations.

A bridge constructed in accordance with the invention embodies a semi-monocoque structure in which the hollow triangular beams withstand the various loads and stresses to which the bridge is subjected. The upper sheet or sheets forming the top of the structure resist compression stresses, and the sheet or sheets forming the under surface of the bridge resist tension stresses. Moreover, in such a bridge the arrangement of the elements is such that a load applied at any point is supported by all of the elements acting together as a unitary structure, thereby enabling lightweight metal to be used in the bridge with a marked reduction in dead weight without sacrificing strength.

A roadbed of, for example, reinforced concrete is formed directly on the upper surface of the semi-monocoque structure. Preferably, the roadbed is formed by pouring wet concrete over reinforcing members which include various structural members of the beams, to thereby 3,103,025 Patented Sept. 10, 1963 distribute the stresses relatively uniformly throughout-the bridge structure.

Bridges and other structural members according to the invention have the advantage over structural steel bridges of requiring little or no maintenance other than keeping the roadbed thereon in repair. Painting is reduced to a minimum, and little or no corrosion of the aluminum elements will take place under normal conditions of use. In those localities where salt Water corrosion might occur the aluminum components can be anodized to increase their corrosion resistance.

Inasmuch as the beams themselves are formed of lightweight metals such as aluminum alloy, and these beams can be made in suitable lengths for assembly at the site, they can be prefabricated and transported readily by means of trailers or the like to the construction site.

For a better understanding of the present invention, reference may be had to the accompanying drawings in which:

FIGURE 1 is a perspective view in partial section of a typical bridge embodying the present invention;

FIGURE 2 is a view of a section of the bridge taken along the line 2-2 in FIGURE 1;

FIGURE 3 is a View in partial cross-section taken along the line 33 in FIGURE 2; and

FIGURE 4 is a view in partial cross-section taken along the line 4-4- in FIGURE 2.

Referring to the bridge shown in the drawings as an illustrative embodiment of the invention, the bridge 10 is 50 ft. long and is provided with a 24 ft. wide roadbed 11 of cast concrete,part of which is cut away in FIG. 1 to reveal a network of reinforcing rods and the upper surface of the structure. Each 50 ft. section of the bridge Weighs 11,300 pounds, only a fraction over nine pounds per square foot, and the bridge has a load carrying capacity satisfying highway requirements of a bridge of the size indicated. The arrangement of the various structural members for the bridge takes into consideration the torque loadings produced by wind against the side of the bridge and loadings produced by vehicles crossing the bridge. In addition, the bridge has withstood in one test operation an eccentric loading of percent of the design moment placed six feet from the center of the roadway.

Referring now to FIGS. 1 and 2, the bridge 10 is formed of three

beams

12, 13 and 14, each of which is of hollow triangular cross-section having an upwardly disposed base portion 15 and a downwardly disposed lower apex 16. Each of the beams is of isosceles or equilateral triangular cross-section, each side of which is formed of sheets of aluminum or aluminum alloy of appropriate thickness to

present sides

17, 18 and 19. The elongated relatively narrow load-bearing beams are disposed in side-by-side and interconnected load-transferring relationship.

As best. shown in FIG. 1, each of the

sides

17, 18 and 19 is reinforced by means of a plurality of aluminum angles 20 extending transversely of the beam. The angles are of a type commonly known as bulb angles; that is, they have thickened and rounded outer edge portions 21, as shown more particularly in FIG. 4. Moreover, the

sides

17, 18 and 19 of each beam are reinforced by positioning these angles 20 at spaced-apart intervals along each beam to stiffen the sheets against lateral flexing and, thus, improve the resistance of the sheets to deflection under shearing stresses.

To reduce further flexing of the sheets, each beam is provided at its ends with

channel members

26, 27 and 28 as seen in FIG. 2 and similar channel members spaced therefrom and forming the ends of the beam unit,

members

26a, 27a and 28a being visible in FIG. 1 and only member 28:: being visible in dotted lines in FIG. 4. The

flange 45 is formed on the corner piece 4% lower ends of the

channel members

27 and 28 are secured together by a gusset plate 29 in the form of an aluminum alloy angle. A gusset plate 39 (PEG. 4), similar to the plate 29, is used to secure the lower ends of the

channel members

27a and 28a. The lower ends of the previously described angles which are spaced apart throughout the length of each beam are not secured together, except those at approximately five foot intervals.

All of the angles 20 and the

end channel members

27 and 28 are secured at their lower ends to an apex corner piece 22 which extends over the entire length of each beam. As best shown in FIG. 2, the apex corner piece 22 of each beam is formed of an aluminum alloy extrusion having a thickened Web or base portion 23 and outwardly diverging edge flanges 24- and 25 to which the sheets forming the respective sides 13 and 19 of the beam are secured by means of rivets, bolts or the like, indicated by the numeral 31. A side flange of each

channel member

27 and 28 is also secured by means of the. rivets or bolts 31 to the flanges 24 and 25 of the apex corner piece 22.

Reinforcing

plates

32 and 33 are secured to the outer surfaces of the flanges 24 and 25 by these same rivets or bolts 31 at each end of the beams.

Filler pieces

34 and 35 are inserted between the reinforcing

plates

32 and 33 and the side sheets for

sides

18 and 19 of the respective beams to provide a smooth joint and to further reinforce the apex 16 of the beam. The intermediate angles Zll are similarly joined to the apex corner piece 22 but, as mentioned above, without the gusset plates except for those angles 20 at approximately every five feet along the length of each beam.

The two upper corners formed along the length of each beam by the channel and angle members with the ends of the base 15 are reinforced in a different manner. As shown in FIG. 2, the corner piece 4% has a base flange 4-1 which is inclined acutely with flange 42, the angle being essentially complemental to the angle between the base 15 and the side 19' of each triangular beam. The flanges 41 and 42 are riveted, or otherwise secured, to the aluminum sheets forming the sides l'i7 and 19 and to the flanges of the

channel members

26 and 28. An upwardly extending and is inclined at an angle, as shown in FIG. 2. The upper end 44 of the flange 43 is turned over to lie in substantially a horizontal plane, which will be referred to again presently. A ridge 45 extends from the lower end of the flange 43 furtheumost from the flange 44.

A corner piece 56), formed on the adjacent triangular beam, has a base flange 51 and a flange 52, both formed similarly as the flanges 41 and 42 described above. An upwardly extending flange 53 is formed on the corner piece and is inclined at an angle matching that of the upwardly extending flange Ben the corner piece 4d. The upper end 54 of the flange 53 is turned over to lie in in a substantially horizontal plane. A recess 55 is formed at the opposite end of the flange 53 from the turned-over end 54, and it extends throughout the length of the corner piece 50 to receive the ridge 45 as shown in FIG. 2.

With the corner pieces ill and 5t? placed together, as shown in FIG. 2, it may be seen that a force applied in a vertical direction will be resisted by the inclined flanges 43 and 53. To secure these two corner pieces 44 and 50 together more positively, a plurality of bolts 56 are positioned at spaced-apart intervals along the entire length of the beams.

The corner piece 69 along each side of the structure is formed somewhat similar to the corner pieces described above. That is, the corner piece 60 is provided with a base flange 61 and a flange 62 inclined at an acute angle therewith. A channel member is supported in cantilever fashion between two

flanges

64 and 65 extending from opposite end of an upwardly extending flange 66 of the corner piece 66). The channel member as provides additional footage in the over-all width of the structure to support the roadbed 1-1.

As shown in FIGS. 1, 2 and 4, the apex corner pieces 3.6 of the hollow triangular beams 12, 1.3 and 14 are joined by means of a sheet "Ill of aluminum alloy to completely close the bottom of the bridge structure. The sheet ill, which may be either a single large sheet or a plurality of smaller sheets, is reinforced at intervals by means of transvers angle members 71 which may be substantially identical to the angle members 2i) including the bulb ends 21, FIG. 4. The longitudinal sides of the sheet 7t"; are attached by means of rivets or the like to a longitudinally extending T-shaped angle '72. The T- shaped angle '72, in turn, is attached to the base flange 23 of the apex corner piece 22 by means of bolts 73, or the like. As shown in FIGS. 2 and 4, the angle member 71 is secured to the base sheet 7e) by means of rivets 74 spaced at appropriate intervals along the length of the angle 71.

At spaced-apart intervals along the length of the bridge structure, concrete footings are provided to support the apex corner piece 16 as shown particularly in FIGS. 1, 2 and 4 of the drawings. A plate 81 is positioned on each of the concrete footings Sll and is held in place by bolts 82. A recess or channel 83 in the upper surface of the plate 81 is adapted to receive a block of suitable resilient material 34, such as bronze impregnated with oil, on which rests a bearing plate 85. An elongated bolt 36 is provided with an intermediate nut 87 to assist in securing the plate 81 to the concrete footing S0, and the nut 83 at the upper end of the bolt 86 is tightened only sufliciently to maintain the upper plate in position. As it may now be seen, this type of bearing permits longitudinal movement of the structure relative to the footings 8%.

As described previously above, the upper corner pieces 4% and 6d are provided with turned-over

flanges

44 and 64. These flanges 44 and 6d are formed such that Z- shaped shear tie members or elements 9%) may be attached thereto by means of rivets or bolts 91 and are spaced at intervals along the length of the structure, as

est seen in FIG. 1, to increase the shear strength characteristics of the concrete roadbed 11.

The upper sheet for side 17 of each triangular beam supports a sheet 92 which has transverse corrugations 93. The corrugations 93 are actually enclosed by and become part of the concrete roadbed 1]. to give the roadbed additional support between beam flanges. Of course, the corrugations 93 may be longitudinal, if desired, in which case they also serve as compression material prior to the establishment of composite action-between aluminum and concrete.

The upper flanges of the respective Z-shaped shear elements 94} are used, for convenience, to support a network 95 of reinforcing rods. Portions of the concrete roadbed 11 are cut away in FIG. 1 to show this network of reinforcing rods being supported directly above the upper surface of the bridge structure. The roadbed 11, new, is formed by casting the wet concrete direotry on the upper surface, described above, of the structure. The concrete will flow between the transverse corrugations 93, as seen in FIG. 3 and, thus, will enclose the Z-shaped elements flfl and the network 95- of reinforcing rods. Thus, the shear tie members E i will become fully embedded within the road bed slab 11. In the finished permanent composite bridge structure suitable means such as the sheets 7t) joining lower apices l6 and the downwardly inclined sides T18 and 19 of the beams act as the primary tensile load-bearing elements of the structure while the road-bed slab acts as the primary compression load-bearing element in the structure.

To further detail the illustrative bridge structure, all of the aluminum sections are formed of 606l-T6 aluminum alloy (an alloy composed of 0.25% copper,

0.6% silicon, 1.0% magnesium, 0.25% chromium, and the remainder aluminum).

By utilizing the structural arrangement described indetail above, the aluminum is used to its greatest efficiency and, therefore, its cost is not unnecessarily high. The cubic volume of concrete required for the roadbed is reduced by from one-third to one-half that customarily used, a factor which reduces still further the amount of dead weight to be supported by the beams. The concrete roadway 11 is formed integrally with the upper structure of the bridge and, therefore, is supported throughout its area so that it will not crack under load. In addition, a load applied at any point on the structure will be supported by the entire structure and not merely the beams immediately beneath the load. That is, the entire bridge structure is deflected by a load applied thereto. A structure as described above provides its greatest support under areas that will be highly loaded, and lesser support in lightly loaded regions. The lightness of the structure lends itself to ease of mobility by all means of transportation and reduces the requirement of heavy field handling equipment.

A semi-monocoque cellular structure of the type described above has tremendous torsional rigidity to the extent that a load placed eccentrically on one side of the structure activates all of the material of all the beams, requiring the entire structure to contribute resistance to the load and not solely the local beams adjacent to the point of load application. This alleviates the requirement for the concrete roadway slab to act as the primary load transferring member. Actually, the centroid of the composite section is just a little below the lower surface of the concrete.

It will be understood that various dimensions of a structure for a particular purpose may now be calculated by one skilled in the art using the structural arrangements described above, and more than three triangular beams may be used in a structure if desired.

While the structure described above is especially suitable for bridges, similar structural arrangements can be used for the booms of derricks, power shovels and the like and to other beam-like elements which are subjected to heavy loads. The lightness and strength of the structural units and freedom from frequent maintenance renders them superior to many of the steel structures used heretofore for the purposes mentioned. Accordingly, it will be understood that the particular bridge decsribed in detail above is illustrative and is not considered to be limiting to the scope of the following claims.

We claim:

1. A permanent composite bridge structure comprising a plurality of hollow elongated beams extending lengthwise of said bridge structure in side by side and interconnected load transferring relationship, each beam being of triangular cross-section, each beam also having an upwardly disposed base and downwardly inclined sides and a downwardly disposed corner, the sides of said beams comprising lightweight sheet metal, corner members of thicker lightweight metal secured to the corners of the beams, the downwardly inclined sides of one beam lying in substantially parallel planes with the similarly disposed sides of the other beams, means connecting the downwardly disposed corners of the beams, the corner members of a beam located adjacent both to the upwardly disposed base and the downwardly inclined sides thereof being arranged in load transferring and interconnected relationship, a roadbed slab disposed upon the upwardly disposed bases of the beams, said roadbed slab acting as the primary compression load bearing member in the bridge structure, means including shear tie elements aflixed to the last mentioned corner members of the beams and arranged transversely to the longitudinal axis of the bridge structure, said shear tie elements being embedded in the roadbed slab and acting to fully integrate the roa-dbed slab with the downwardly inclined sides of the beams whereby the downwardly inclined sides Olf the beams and the means connecting the downwardly disposed corners of the beams will act as the primary tensile load bearing elements of the bridge structure.

2. A composite bridge structure as set forth in claim 1 wherein said shear tie elements are comprised of a plurality of Z-shaped members.

3. A composite bridge structure as set forth in claim 1 wherein said last mentioned corner members comprise a first corner member and a second corner member disposed on opposite sides of each beam, said first corner member having a plurality of angularly disposed flanges and a ridge formed in one of said flanges and the second corner member comprising a plurality of anguliarly disposed flanges certain of which mate with certain flanges on the first corner member of an adjacent beam, one of the flanges of said second corner member having a groove within which the ridge on the first corner member of the said adjacent beam is disposed, and means securing said first and second corner members together.

4. A composite bridge structure as set forth in claim 1 wherein stiflening members are secured to and extend transversely of the longitudinal axis of the upwardly disposed bases and the downwardly inclined sides of the beams.

5. A permanent composite bridge structure comprising in combination a plurality of hollow elongated beams extending lengthwise of said bridge structure in side-by-side and interconnected load transferring relationship, each beam being of triangular cross-section and each beam having an upwardly disposed base and downwardly inclined sides and a downwardly disposed corner, the sides of said beams comprising lightweight sheet metal, corner members of thicker lightweight metal secured to the corners of the beams, the downwardly inclined sides of one beam lying in substantially parallel planes with the similarly disposed sides of the other beams, means including sheets of lightweight metal connecting the downwardly disposed corners of the beams, the corner members of a beam located adjacent to both the upwardly disposed base and the downwardly inclined sides thereof being arranged in load transferring and interconnected relationship, a roadbed slab disposed upon the upwardly disposed bases of the beams, said roadbed slab acting as the primary compression load bearing member in the composite bridge structure, means including shear tie elements atfixed to the last mentioned corner members of the beams and arranged transversely to the longitudinal mtis of the bridge structure, said shear tie elements being embedded in the roadbed slab and acting to 'fully integrate the roadbed slab with the downwardly inclined sides of the beams whereby the downwardly inclined sides of the beams and the means including sheets connecting the downwardly disposed corners of the beam will act as the primary tensile load bearing elements of the bridge structure.

6. A composite bridge structure as set forth in claim 5 wherein said shear tie elements are comprised of a plurality of Z-shaped members.

7. A composite bridge structure as set forth in claim 5 wherein said last mentioned corner members comprise a first corner member and a second corner member disposed on opposite sides of each beam, said first corner member having a plurality of angularly disposed flanges and a bridge formed in one of said flanges and the second corner member comprising a plurality of angularly disposed flanges certain of which mate with certain flanges on the first corner member of an adjacent beam, one of the flanges of said second corner member having a groove within which is disposed the ridge on the first corner member of the said adjacent beam, and means securing the said first and second corner members together.

8. A composite bridge structure as set forth in claim 5 wherein stiffening members are secured to and extend transversely of the longitudinal axes of the upwardly disposed bases and the downwardly inclined sides of the beams.

9. A structural unit for a bridge comprising a plurality of elongated relatively narrow load-bearing beams disposed in side-by-side and interconnected load-transferring relationship, each beam being of triangular cross section and forming a substantially continuous triangular cell provided with an upwardly disposed base and downwardly inclined sides, the plurality of beams being so arranged whereby one side of each beam is in a substantially parallel plane with a similarly disposed side of each other beam and with the lower apices of the beams facing in the same direction, the sides of each beam being formed of a lightweight sheet metal, corner pieces secured to each corner of a beam and formed of thicker lightweight metal and extending lengthwise of each beam, means joining said lower apices together and disposed substantially parallel with the upwardly disposed bases of said beams which are also located opposite the lower apices thereof, said lastmentioned means and the downwardly inclined sides of the beams acting as the primary tensile load-bearing elements of the structural unit, stiffening members secured to and extending transversely to the sides and upwardly disposed bases of the beams and means including shear tie members rigidly affixed to the corner pieces of the beams that are located adjacent both to said upwardly disposed bases and the downwardly inclined sides of the beams, said shear tie members extending in a direction transverse to the longitudinal axis of the beams and being adapted to become fully embedded within a road-bed slab when the slab is mounted on the upwardly disposed bases of the beams, whereby the said slab can act as the primary compression load-bearing element of the bridge in which the structural unit is incorporated and said last-mentioned corner pieces comprising a first corner piece and a second corner piece disposed on opposite sides of each beam, said first corner piece having a plurality of angularly disposed flanges and a ridge formed in one of said flanges and the second corner piece comprising a plurality of angularly disposed flanges certain of which mate with certain flanges on the first corner piece of an adjacent beam, one of the flanges of said second corner piece having a groove within which the ridge on the first corner piece of the said adjacent beam is disposed and means securing said first and second corner pieces together.

10. A structural unit for a bridge comprising a plurality of elongated relatively narrow load-bearing beams disposed in side-by-side and interconnected load-transferring relationship, each beam being of triangular cross section and forming a substantially continuous triangular cell provided with an upwardly disposed base and downwardly inclined sides, the plurality of beams being so arranged whereby one side of each beam is in a substan- .metal and extending lengthwise of each beam, means including lightweight sheet metal joining said lower ap-ices together and disposed substantially parallel with the upwardly disposed bases of said beams which are also located opposite the lower apices thereof, said last-mentioned means including lightweight sheet metal and the downwardly inclined sides of the beams acting as the primary tensile load-bearing elements of the structural unit, stiffening members secured to and extending transversely to the sides and the upwardly disposed bases of the beams and means including shear tie members rigidly affixed to the corner pieces of the beams that are located adjacent both to said upwardly disposed bases and the downwardly inclined sides of the beams, said shear tie member extending in a direction transverse to the longitudinal axis of the beams and being adapted to become fully embedded within a roadbed slab when the slab is mounted on the upwardly disposed bases of the beams, whereby the said slab can act as the primary compression load-bearing ele ment of the element of the bridge in which the structural unit is incorporated, said last-mentioned corner pieces comprising a first corner piece and a second corner piece disposed on opposite sides of each beam, said first corner piece having a plurality of angularly disposed flanges and a ridge formed in one of said flanges, the second corner piece comprising a plurality of angularly disposed flanges certain of which mate with certain flanges on the first corner piece of an adjacent beam and one of the flanges of said second corner piece having a groove within which the ridge on the first corner piece of the said adjacent beam is disposed and means securing said first and second corner pieces together.

1-1. A structural unit for a bridge comprising a plurality of elongated relatively narrow load-bearing beams disposed in side-by-side and interconnected load-transferring relationship, each beam being of triangular cross section and forming a substantially continuous triangular cell provided with an upwardly disposed base and downwardly inclined StldBS, the plurality of beams being so arranged whereby one side of each beam is in a substantially parallel plane with a similarly disposed side of each other beam and with the lower apices of the beams facing in the same direction, the sides of each beam being formed of a lightweight sheet metal, corner pieces secured to each corner of the beam and formed of thicker lightweight metal and extending lengthwise of each beam, means joining said lower apices together and disposed substantially parallel with the'upwardly disposed bases of said beams which are also located opposite the lower apiccs thereof, said last-mentioned means and the downwardly inclined sides of the beams acting as the primary tensile load-bearing elements of the structural unit, stiffening members secured to and extending transversely to the sides and the upwardly disposed bases of the beams and said corner pieces including a first corner piece and a second corner piece disposed on opposite sides of each beam and adjacent both to the upwardly disposed base and the downwardly inclined sides thereof, said first corner piece being provided with ridge means, and the second corner piece being provided with a recess means within which the ridge means on the first cornerpiece of an adjacent beam is disposed and means securing said first and second corner pieces together.

12. A structural unit for a bridge comprising a plurality of elongated relatively narrow load-bearing beams disposed in side-by-side and interconnected load-transferring relationship, each beam being of triangular cross section and forming a substantially continuous triangular cell provided with an upwardly disposed base and downwardly inclined sides, the plurality of beams being so arranged whereby one side ofcach beam is in i8, substantially parallel plane with a similarly disposed side of each other beam and with the lower apices of the beams facing in the same direction, the sides of each beam being formed of a lightweight sheet metal, corner pieces secured to each corner of a beam and formed of thicker lightweight metal and extending lengthwise of each beam, means joining said lower apices together and disposed substantially parallel with the upwardly disposed bases of said beams which are also located opposite the lower apices thereof, said last-mentioned means and the downwardly inclined sides of the beams acting as the primary tensile loadbearing elements of the structural unit, stiifening members secured to and extending transversely to the sides and the upwardly disposed bases of the beams, means including shear tie members rigidly afiixed to the corner pieces of the beams that are located adjacent both to said upwardly disposed bases and the downwardly inclined sides of the beams, said shear tie members extending in a direction transverse to the longitudinal axis of the beams and being adapted to become fully embedded within a roadbed slab when the slab is mounted on the upwardly disposed bases of the beams, whereby the said slab can act as the primary compression load-bearing element of 10 the bridge in which the structural unit is incorporated 2,001,315 Proctor May 14, 1935 and said last-mentioned corner pieces comprising a first 2,116,033 Malone May 3, 1938 corner piece and a second corner piece disposed on oppo- 2,245,688 Krueger June 17, 1941 site sides of each beam, said first corner piece being pro- 2,910,016 Faverty Oct. 27, 1959 vided with ridge means and the second corner piece being 5 2,926,928 Bennett Mar. 1, 1960 provided with a recess means Within which the ridge means on the first corner piece of an adjacent beam is FOREIGN PATENTS] disposed Iand means securing said first and second cor- 9 329 Great Britain 1 9 Her pieces together- 1 574,761 France 1924 References Cited in the file of this patent g if f j f UNITED STATES PATENTS E l" 1,073,542 Stewart Sept. 16, 1913 OTHER RLFERENCE" 1,688,723 Lathlop Oct. 23, 1928 15 Engineering News-Record, Jan. 30, 1958, page 22. 1,874,572 Montgomery Feb. 17, 1930 Thofehrn, abstract of rapplication Serial No. 291,581

1,913,342 Schaffert June 6, 1933 published Apr. 27, 1943, AFC. publication.

Claims

1. A PERMANENT COMPOSITE BRIDGE STRUCTURE COMPRISING A PLURALITY OF HOLLOW ELONGATED BEAMS EXTENDING LENGTHWISE OF SAID BRIDGE STRUCTURE IN SIDE-BY-SIDE AND INTERCONNECTED LOAD TRANSFERRING RELATIONSHIP, EACH BEAM BEING OF TRIANGULAR CROSS-SECTION, EACH BEAM ALSO HAVING AN UPWARDLY DISPOSED BASE AND DOWNWARDLY INCLINED SIDES AND A DOWNWARDLY DISPOSED CORNER, THE SIDES OF SAID BEAMS COMPRISING LIGHTWEIGHT SHEET METAL, CORNER MEMBERS OF THICKER LIGHTWEIGHT METAL SECURED TO THE CORNERS OF THE BEAMS, THE DOWNWARDLY INCLINED SIDES OF ONE BEAM LYING IN SUBSTANTIALLY PARALLEL PLANES WITH THE SIMILARLY DISPOSED SIDES OF THE OTHER BEAMS, MEANS CONNECTING THE DOWNWARDLY DISPOSED CORNERS OF THE BEAMS, THE CORNER MEMBERS OF A BEAM LOCATED ADJACENT BOTH TO THE UPWARDLY DISPOSED BASE AND THE DOWNWARDLY INCLINED SIDES THEREOF BEING ARRANGED IN LOAD TRANSFERRING AND INTERCONNECTED RELATIONSHIP, A ROADBED SLAB DISPOSED UPON THE UPWARDLY DISPOSED BASES OF THE BEAMS, SAID ROADBED SLAB ACTNG AS THE PRIMARY COMPRESSION LOAD BEARING MEMBER IN THE BRIDGE STRUCTURE, MEANS INCLUDING SHEAR TIE ELEMENTS AFFIXED TO THE LAST MENTIONED CORNER MEMBERS OF THE BEAMS AND ARRANGED TRANSVERSELY TO THE LONGITUDINAL AXIS OF THE BRIDGE STRUCTURE, SAID SHEAR TIE ELEMENTS BEING EMBEDDED IN THE ROADBED SLAB AND ACTING TO FULLY INTEGRATE THE ROADBED SLAB WITH THE DOWNWARDLY INCLINED SIDES OF THE BEAMS WHEREBY THE DOWNWARDLY INCLINED SIDES OF THE BEAMS AND THE MEANS CONNECTING THE DOWNWARDLY DISPOSED CORNERS OF THE BEAMS WILL ACT AS THE PRIMARY TENSILE LOAD BEARING ELEMENTS OF THE BRIDGE STRUCTURE