US3343320A - Construction of channeled steel beams - Google Patents

Description

Sept. 26,1967'- I F'.KRA JC|NOVIC 3,343,320

CONSTRUCTION .OF CHANNELED STEEL BEAMS Filed June 23, 1965 Y 7 Sheets-Sheet 1 INVENTOR PETER KRAJCINOVIC Sept. 26, 1967 P. KRAJCINOVIC CONSTRUCTION OF CHANNELED STEEL BEAMS 7 Sheets-Sheet 2 Filed June 23, 1965 INVENTOR PETER KRAJCINOVIC v v I ATTORNEY! p 1967 P. KRAJCINOVIC 3,343,320

CONSTRUCTION OF CHANNELED STEEL BEAMS 7 Filed June 22 1965- 7 Sheets-Sheet 5 1: IO N q N m INVENTOR KRAJCINOVIC Sept. 26, 1967 JP. KRAJCINOVIC 3,343,320 v CONSTRUCTION OF CHANNELED STEEL BEAMS Filed June. 25, 1965 '7 Sheets-Sheet 4 INVENTOR PETER KRAJCINOVIC p 26, 7 P. KRAJCINOVIC 3,

7 CONSTRUCTION OF CHANNELED STEEL BEAMS Fil'ed .June 23, 1965 '7 Sheets-Sheet 5 AJGINOVI C Sept. 26,1967 IP.KRAJCINOVYICV 3,343,320

CONSTRUCTION OF CHANNELED STEEL BEAMS Filed June 25; 1965 7 Sheets-Sheet 6 IIIIIIIIIIIII INVENTOR PETER KRAJCINOVIC Sept. 1967' P. KRAJCINOVIC 3,343,320

CONSTRUCTION OF CHANNELED STEEL BEAMS I Filed June 23, 1 965 7 Sheets-Sheet 7 INVENTOR PETER KRAJCINOVIC ATTORNEY;

United States Patent 3,343,320 CONSTRUCTION OF CHANNELED STEEL BEAMS Peter Krajcinovic, 504 Fattis and Monis Mansions, Corner Jeppe and Harrison Sts., Johannesburg, Transvaal, Republic of South Africa Filed June 23, 1965, Ser. No. 466,268 Claims. (Cl. 52--252) This is a continuation in part of the applicants copending application Ser. No. 122,316, filed July 6, 1961, and now abandoned. This invention relates generally to structural units and more particularly to a novel compound steel-concrete structure for use in bridges, buildings and the like.

It should be understood at the outset that this invention, although herein specifically described as applied to bridge structures, is equally applicable to any structural form such as a roof, deck, floor or any load-bearing structure which sustains transverse loads and resists their stressing effects.

In the prior art, the construction of combined steel and concrete structures for supporting transverse loads utilized mutually independent beam-slab systems, the slab portion of the system being formed generally from reinforced concrete for supporting the superimposed loads and for transmitting the loads to the slab-supporting steel beams.

The steel beams were designed to act independent of the slabs and to support both the concrete slabs and the loads imposed thereon.

In the next stage of development in the design of combined steel-concrete structures, it was discovered that a natural contact bond, formed between the concrete slab and structural steel beam portions would enable the concrete slab portion to not only transmit superimposed loads to the supporting steel beams, but would further contribute to the strength of the steel beams in their function of supporting the transmitted loads, thereby forming a new type of combined or composite steel-concrete beam structure. It was then concluded that, if adequately strong, the natural steel-concrete contact bond between the beam and the slab components could be structurally useful and beneficial. After some use and experimentation it was found, however, that the strength of the bond achievable was generally inadequate and did not afford the required safety. The possibility of utilizing this bond as a primary contributor to structural strength was therefore discarded and artificial mechanical means were turned to achieve the required connection between the components. Such mechanical connectors are broadly termed shear connectors and the recent direction of the art has been devoted to finding the most eflicient and effective shear connectors, discounting entirely the possible contribution afforded by the natural contact bond between the components.

In present-day composite structural design, the shear connectors are required to furnish an adequate and mechanically eflicient connection between the steel and concrete components thereof. As such, the connectors are relied on to resist not only the anticipated loadings but all possible mechanical interactions between the components as well. These interactions can arise from such sources as secondary mechanical effects of loads imposed on the structure or loads imposed by climatic changes. These interactions are manifested not only as longitudinal intershearing caused by transverse loading but also longitudinal intershearing action caused by the longitudinal direct shearing effect of longitudinal loading such as cleavage, flexing and twisting. Climatic conditions impose interactions characterized by interdilational mechanical actions caused by the differential thermal expanding and contrasting characteristics of the steel and concrete components as well as the shrinkage'during curing of the concrete portion. Iuterdilation between steel and concrete consists of the interaction in which one part tends to dilate (extend or shorten) that is prevented by the counterpart component which acts upon it in an opposite direction (counterdilate).

Another misuse or misapplication of prior art tie connectors of the bent, hook, spiral, hoop or stirrup type lies in failure to provide distributed supports, within the concrete mass, at the concave points of these connectors, contrary to the generally accepted sound principles governing design of reinforced concrete structures. This causes the connectors, even in their role of shear preventing members, to be ineflicient because the imposition of concentrated actions on relatively narrow strips or bands of concrete caused by the undistributed load exercises a splitting action thereon. This action not only unfavorably overstresses the concrete but also produces a very undesirable decrease in the rigidity of the concrete or a corresponding undue increase in yielding to deformation since under such circumstances concrete stressed in this manner becomes plasticized. As a further result, the abseuce of the required supports for the bends in the connectors increases the tearing, shearing, flexing and distorting action of the concrete on the connectors, and punching, shearing and flexing distortion actions of the tie connectors on the beam flange including a shearing and flexing distorting action of the tie connector on the welds which fasten them to the beam flanges. All of the above forces result in a requirement for much stronger flanges and welds than would normally be needed if the bends of such tie connectors were lightly loaded or properly supported by transverse steel reinforcement at the concave portion of their bends.

Another problem encountered with conventional tie connectors is that, functionally, they are cantilevered beams since one end thereof is fastened to the steel beam while the remainder is anchored in the concrete mass of the slab. The tendency to displace the steel beam relative to the reinforced slab subjects such tie to highly intensive combined shearing, flexing and tensional stresses with corresponding undue distortions and deflections thereof.

Due to a chemical-physical surface contact interaction between the steel and the hardening concrete, and an interlocking mechanical resistance against the relative dislocation between the steel and the hardened concrete and a resistance to separation and relative displacement of the steel and the concrete will occur whenever there is a tendency for different mechanical behavior across their contact surface. This resistance is called the natural (contact) bond. As already stated, for the conventional type of composite steel-concrete structures, this natural steel-concrete contact bond is discounted as a means for the conjoining of the steel and concrete of such structures.

For the conventional type of steel-concrete composite structures this natural steel-concrete bond is customarily only 40 to 60 percent of that which could be considered as adequate for the conjoining of their steel rib (beam) and reinforced concrete slab structural portions to act with the required safety as the compound type of steelconcrete conjoint structures, or compound steel-concrete structures.

During the course of the development of conventional composite steel-concrete structures, the fact that composite structures function predictably and regularly only so long as they act as a compound beam i.e. so long as the natural bond therebetween is not disrupted. After this natural bond starts to deteriorate the mechanical behavior of the structure becomes increasingly irregular with progressive disruption of the remainder of the bond.

It is an object of this invention to utilize and preserve the naturalcontact bond between steel and concrete in compound structures through (1) decreasing the stress imposed thereon to such a degree that the bond is not disrupted by increasing the area of contact between the steel beam and the concrete slab components, by (a) channeling or forming the face of the beam to be bonded to the concrete component in a channel configuration, and/or (13) providing longitudinal steel tie rods along the beam, connected thereto at least at the ends, the rods, when embedded in the concrete component, effectively increasing the contact area between the components, and through (2) increasing the strength or capacity of the contact bond between the steel and concrete portions of the compound beam by (a) use of chequered, or roughened steel plates or rolled steel beams with chequered faces for the concrete-seel interface, and/or deformed steel bars as the longitudinal ties and (b) attaching frame stifleners to the beams which, when encased in the concrete component, increase the strength of the contact bond, function as shear and cleavage connectors between the components, act as transverse ties or stirrups for at least one portion of the concrete component and act as a normal reinforcement for the concrete component.

It is another object of this invention to provide a novel transversely supporting beam structure and method of fabrication therefore which furnishes a longer span capability with fewer supporting beams than heretofore achievable by incorporating a monolithic compound metal-to-concrete deck beam structure.

It is a further object of this invention to provide a high strength-weight ratio beam and deck structure combining a concrete deck and metal beam into a monolithic load-supporting structure.

It is a still further object of this invention to furnish a monolithic concrete-metal beam load-supporting span by providing a novel means for joining the components thereof to insure a permanent physical-chemical interface bond therebetween.

It is still another object of this invention to furnish a novel means for conjoining the components of a concrete metal beam load-supporting span to insure a permanent physical-chemical bond therebetween by providing a channeled concrete contacting portion on the metal component to increase the concrete-to-metal contact surface area of the structure.

It is still another object of this invention to furnish a novel means for joining the components of a steelconcrete beam structure to insure a permanent physicalchemical bond therebetween by providing a channeled concrete contacting portion to the metal component and by providing longitudinally disposed beam-connected ties embedded in the concrete component to increase the concrete-to-metal surface area contact -of the structure.

It is still another object of this invention to furnish a high-strength monolithic steel-concrete beam-structure which contains a minimum amount of reinforcing and structural steel by providing a composite structural beam member in which the steel beam is mechanically preconditioned (prestressed) for maximum effectiveness and in which the steel and the concrete are fully utilized as appropriate load-carrying portions of the beam.

It is yet another object of this invention to provide a method of fabricating maximum strength-weight ratio composite steel beam-concrete deck beam structure in which the structure is progressively strengthened by the steps-of fabrication thereof.

It is a further object of this invention to furnish a steel beam structure for fabrication into a composite steel-concrete rib slab beam structure which contains a minimum of steel by fabricating the beam with beamsupporting strength somewhat in excess of that sufficient to support the weight of the beam itself, the beam being progressively strengthened by addition of the concrete component during the fabrication of the span.

It is still a further object of this invention to furnish a steel beam particularly adapted for use in a fabricationstrengthened, monolithic, steel-concrete beam structure by providing a frame-stiffened channeled portion for the beam.

It is yet a further object of this invention to furnish a frame-stiffened channeled steel beam for combination with a concrete deck structure in which the frame stiffeners when combined with and enclosing longitudinally disposed ties also serve as novel concrete-to-metal ties.

It is yet another object of this invention to furnish a beam structure having a greater span capability than heretofore achievable with a like cross section by providing monolithic composite concrete steel beam structure which achieves a greater strength-weight ratio.

It is still another object of this invention to furnish a beam-supported structure particularly adapted for use in bridges and similar deck roof or floor structures which minimizes the requirement for beam side bracing and/ or secondary or tertiary beams by providing a monolithic steel-concrete beam-slab structure in combination with novel transversely spaced and beam suspending end supports.

These and other objects of the invention will become better understood by reference to the following detailed description when viewed in light of the accompanying drawings wherein like elements thereof are indicated by like numerals and wherein:

FIGURE 1 is a perspective view partially broken away of a beam embodying features in accordance with the invention;

FIGURE 1a is a broken away perspective view of a portion of a beam similar to that shown in FIGURE 1 illustrating a variation in accordance with the invention;

FIGURE 2 is a sectional view of a beam similar to that shown in FIGURE 1 combined with a deck structure installed on bridge piers;

FIGURE 3 is a side elevational view of FIGURE 2 partly in section and partly broken away;

FIGURE 4 is an enlarged fragmentary view of a portion of the structure shown in FIGURE 2;

FIGURE 5 is an enlarged side elevational view of a portion of the structure of FIGURE 3;

FIGURE 6 is a view similar to that of FIGURE 2 showing a variation in the beam structure in accordance with the invention;

FIGURE 7 is a view similar to FIGURE 6 showing a further variation of the beam structure in accordance with the invention;

FIGURE 8 is a view similar to FIGURE 7 showing a further variation in the beam structure in accordance with the invention;

FIGURE 9 is an enlarged sectional view similar to FIGURE 8 showing still another variation of the beam structure in accordance with the invention;

FIGURE 10 is a perspective view of yet another beam structure in accordance with the invention;

FIGURE 11 is a view similar to FIGURE 10 showing still a further variation of beam structure in accordance with the invention;

FIGURE 12 is a perspective view of a basic beam embodying improvement in accordance with the invention;

FIGURE 13 is a perspective view of a series of beams installed on supporting members in accordance with the invention;

FIGURE 14 is a sectional view of another beam constructed in accordance with the invention;

FIGURE 15 is a sectional view of a span structure embodying beams formed in accordance with the invention; and

FIGURE 16 is a fragmentary view similar to FIGURE 15 illustrating a variation of the beam components thereof in accordance with the invention.

One of the primary features of this invention is the utilization of a lightweight, minimum required strength structural shape as a foundation upon which a final composite span structure is fabricated. This invention incorporates, for the structural shape, a channel as the primary steel structure. The channel shape, as hereinafter referred to, encompasses all configurations such as V, U box U, semicircular, hat or inverted U shapes and like sections as long as at least one longitudinal accessible trough or channel is included. As such, channeled beams can consist of -a single or of a multiplicity of channels for which reason corrugated steel plate structures are intended to be included within the term chauneled, and as such form part of this invention.

As used in the specification, the term beam is intended to denote any structure consisting of any required number of beams including a single, simple beam which transmits its load substantially lengthwise (in the direction of its longitudinal axis) and which is capable of resisting the bending effects of loads placed thereon, either alone or in conjunction with other stressing effects from the loading thereon. For this reason, slabs (rel-atively wide beams or beam structures), struts and tendons (strutting and tieing structures), arches and/ or suspending cables (arching and suspending structures) when relatively stiff and flexionally resistant, are consid ered to be specific forms of beams within the meaning of the invention.

Channel-shaped steel beams of the above-described type, when transversely stiffened with frame-like stiffeners and/or bonded with plain or reinforced concrete to form a compound steel-concrete beam structure, have unexcelled structural-mechanical and geometrical properties. Without being transversely stiffened, channeled steel beams with relatively thin channel-forming steel portions would be too distortive to be adequately efiicient as beam structures. The conventional method of cross stiffening of channeled steel beams by means of rimtienin-g battens is usually inefficient because it leaves the sides and the bottom of such beams unstiifened and consequently unstable under the mechanical etfects of their transverse loadings. The conventional methods of cross stiffening channeled steel beams with full steel plate diaphragms would prevent the use of longitudinal ties and would also make it inconvenient to compound the beams with channel-filling concrete because full steel-plate diaphragms would chop it (the concrete) into independent longitudinal parts. The only feasible method of cross stiffening of channeled steel beams with thin channelforming portions is with frame-like stiifeners and/0r perforated steel plate diaphragms through which longitudinal tie-rods can be easily mounted if the beam is to be compounded with the concrete. These latter frame stilfeners function as described above.

h Because of the above problems, beams of the type utilized by this invention have generally been confined to the construction of relatively short span and/or lightweight beam structures of the secondary importance in spite of the otherwise ideal properties of these beams.

This invention provides a means of utilizing channelshaped beams by providing framed or generally hooped or looped stilfeners which increase the strength and rigidity of the steel beam. By increasing the strength sufficiently the basic structure may be supported prior to the combination of the beam with the concrete deck portion of the span. The stiffening frames are subsequently incorporated in the concrete component to provide mechanical connectors between the components. Under the circumstances, the relative universal stiffness and strength of channeled steel beams, when adequately stiffened with properly spaced transverse frame stilfeners of adequate strength and stiffness and provided with longitudinal ties, makes the beam unexcelled for the construction of compound steel-concrete structures; which is the underlying idea of this invention.

Framed cross stiffeners of channeled steel beams, in addition to serving to stiffen the relatively thin channelforming portion of the steel beam have a multiple useful function once embedded into the concrete component as will be described below. The longitudinal ties also function as the required longitudinal reinforcement of the concrete part of the structure. The trough-filling concrete not only furnishes the required strength and the rigidity but also functions as an additional stiffener for the steel beam.

The use of the channel beam configuration in a compound concrete-steel structure provides another benefit particularly applicable to deck or floor structures on which adverse side transverse loadings may be imposed on the deck surface, in that the shape of the channel provides a natural keying action between the concrete and the steel so that transverse loadings are resisted by the steel beam and reinforced concrete slab (the components themselves combining as a beam structure).

To further increase the load carrying capability of the steel beam alone without adversely increasing its flexional rigidity and weight, the beam structure can be mechanically preconditioned before the compositioning with concrete. This may be done either as a temporary or permanent measure by prestressing the beam with cables properly disposed therethrough, and/or precounterflexing the beam with suitable propping disposed therebelow after the beam is in place on the span-support structure. Intermediate mechanical conditioning of the structure can also be employed by changing the preconditioning loading on the beam after the beam is combined with the concrete or imposing additional mechanical intermediate or opposed post conditioning loadings on the resulting structure.

A further advantage of the channeled steel beam of this invention is that it can be strengthened and rendered adequately rigid by compounding it with concrete in two or more stages. This is accomplished by providing the channel beam of sufficient initial compressible strength to support only the weight of the beam itself plus the weight of the concrete sufficient to fill the channels of the beam. The beam is then supported and the channels are filled in one or more stages with concrete thereby strengthening and rendering the compressed side of the beam stifi by providing additional reinforced concrete channel-filling ribs for the compressive area of the beam. By proper proportioning of channels, additional channel filling concrete will increase the strength of the beam to a degree suflicient to support the weight of the next construction stage, d'eck part, structure and necessary construction equipment. The interposed channel filling concrete will also furnish a concrete-to-concrete interface between the beam and the bridge deck structure as will be discussed in greater detail below.

In addition to utilizing the channel-shaped structure of the beam to increase the area of the steel-concrete contact of the final compound beam, this invention further provides means to increase the contact area beyond that available by the channeling .of the'steel beam, by adding longitudinal tie rods to the steel beam tofurnish additional steel-concrete contact area complementingthat of the channels up to the required total steel-concrete contact area. The rods of these longitudinal ties, when mounted within the framed cross stiffeners, function additionally as the required longitudinal reinforcement of the reinforced concrete part of the compound steel-concrete structure.

The term conjoin is used as a generic description of any type of composition, connection, compounding or joining of parts. Under the generic term, the species term composite is intended to include two prior art structures made up of distinct parts, elements or substances conjoined together at discrete points by structural connectors such as by the prior art shear connectors. The species term compounded, on the other hand, is intended to describe the conjoining afforded by this invention, that is the atachment of the components by means of a natural steel-concrete contact bonding over the whole steel-concrete contact interface.

Turning now to FIGURE 1 of the drawings, a steel beam component partly compounded with concrete is shown. The beam component basically comprises a hollow cylindrical beam portion generally shown at 21 having vertically disposed longitudinal side plates 22 attached thereto proximate the horizontal center line thereof. Each end of the beam is provided with an end plate 23 connected to both the cylindrical portion and vertical side plates of the beam, which plate at the upper end thereof is connected to transverse support members 24 which transmit beam loads to the beam support structures (not shown). A plurality of transversely disposed rim tieing stiffeners 25 are placed spaced at required intervals along the length of the beam and are connected to the top of the beam 21 and to the top faces of side plates 22. These stiffeners serve to provide structural connection and some rigidity between the vertical side plates and to function as block connectors of the composite beam. Although these members are formed from angle irons in the embodiment of FIGURE 1, they may obviously be in the form of flat or other type battens, and may be trussed, laced, extended and the like alternatively. The rim stiffeners can be tied either to the upper surfaces of the vertical side plates 22 or at the internal edges thereof so that the stifieners are flush with the top edges of the side plates. For purposes of clarity, a portion of the stiffeners 25 are omitted from the assembly illustrated in FIGURE 1. A plurality of frame stiffeners 26 are transversely mounted in the troughs or channels formed by the upper section of the cylindrical portion 21 and the vertical side plates 22 and are alternately interspersed with the tieing stiffeners 25. The stiffeners 26, in turn, support a plurality of longitudinally disposed tie rods 27 tackwelded or tied with wire thereto. Special heavy end frames 28 may be provided at either end of the beam to furnish the anchorage for the tie rods 27 which are welded thereto in a permanent connection. The end frames 28 should be of sufiicient rigidity so that the tie rods are effectively anchored to the beam to act as structural extensions thereof during expansion, contraction, bending and flexing thereof. A longitudinally disposed tubular conduit 29 may be added where required for housing of spantieing tendons which traverses the beam through or above the transverse members 24 from one end to the other for purposes to be described below.

A poured concrete member 30 hereinafter referred to as channel-filling concrete is formed within the channel defined by the top of the cylindrical beam portion 21 and the vertical side plates 22 engaging the lower portion of the frame stiifeners 26 and the tie rods 27 disposed within the channel.

In FIGURE 1a a modification of the end anchorage for the tie rods is shown and the portions of the beam shown in that figure corresponding to the portions of the beam of FIGURE 1 are indicated by like numerals of the next higher order. In FIGURE 1a, an extra-strong end-frame stiffener 126 is mounted to the beam at a point spaced from the end transverse members 124 and the tie rods 127 are bent down over the frame member 126 and attached to the transverse member 124 by welding or some other connection. As in the embodiment of FIGURE 1, the tie rods disposed in the trough formed by the side plates 122 and the cylindrical beam portion 121 are attached to the most proximate structural portion of the beam, e.g. in the case of those disposed along the side plates 122, to the side plates and those disposed along the cylindrical portion 121, to the cylindrical portion.

Turning now to FIGURES 2, 3, 4 and of the drawings, the beam of FIGURE 1 is shown installed on a bridge pier 31 and is bonded with a bridge deck 32 to form the final steel-concrete beam structure. In FIGURE 3, a pair of longitudinally aligned compound beams are shown in end abutting relationship and the corresponding parts of each are indicated by modifying letters a and b.

As was indicated above, the beam is supported through the transverse beam members 24. These transverse beam members are provided with rocker engaging plates 33 which are formed with arcuate recesses on the lower surfaces thereof. Rockers 34, mounted on flanged plates 36 on the piers 31, engage the plates 33 to support the beam. The rockers are retained on the flange plates 36 against lateral sliding movement by pins 37 (FIGURE 5) mounted in the plate 36 resting on the pier 31, the pin 37 projecting into a recess 38 (FIGURE 5) in the bottom surface of the rocker 34. The rocker type of suspension serves as a pivotal support-means to allow longitudinal movement of the bridge spans due to changes in temperature, humidity and/or loadings placed on the span in the plane of the span deck.

The cylindrical beam portion 21 is made up of an adequately thick semi-cylindrical plate 39 reinforced where required by additional arcuate plates 41 and 42 along the lowermost portion thereof. The upper portion of the cylindrical beam portion 21 is usually formed of a thinner semi-cylindrical plate 43 which is butt welded to the upper edges of the lower plate 39 adjacent the connecting point of the vertical side plate 22 as is shown most clearly in FIGURE 4 of the drawings. This style of fabrication, although preferred in certain situations may be varied as desired so long as the side plates 22 intersect the cylindrical portion of the beams tangentially. The relative thicknesses of the various plates are, of course, to be determined by proper design according to the length of the span and load requirements for the particular span, however, the upper plate 43 stiffened in the final structure by the reinforced concrete need only be of sutficient strength to resist a compressive loading of that portion of the beam which is equivalent to the bending load imposed on the beam by the weight of the steel beam itself and the trough concrete 30 plus whatever additional loads can be anticipated under the weight of the men and equipment necessary prior to the final hardening thereof. Once hardened the trough-filling concrete 30 provides additional stiffening for the structure.

The cylindrical beam portion 21 is stiffened internally by annular ring stiffener members 44 disposed at suitable intervals along the length of the beam. The stitfeners 44 provide reinforcement for the beam-forming plates to resist buckling thereof under bending, compressive or torsional loads placed thereon as is common in cylindrical load-supporting structure design. A plurality of tubular members 46 may be disposed within the cylindrical beam portion 21 traversing the ring stiffeners 44 and enclosing prestressed tendons 47 which are attached to anchor blocks 48 at each end of the beam structure. Where required the tubular conduit 29 carries post-tensioning spantieing cable 49 which will be described in greater detail below. As is shown in greatest clarity in FIGURE 4 of the drawings, a outwardly turned flange 51 is provided at the upper end of the vertical side plate 22 and an inwardly extending, longitudinally disposed reinforcing stiffener 52 for the plate 22 is attached to the vertical side plate 22 at the required place between the upper and lower edges thereof.

With particular reference to FIGURES 3 and 5, the specific structure of the transverse beam member 24 may be seen. The transverse beam member 24 is formed by welding two channel members 53 and 54 to opposite sides of the end plate 23 in back-to-back relationship so that they essentially form a modified I beam, the webs of which, if required, may be stiffened. Since all of the beam loadings are transmitted through the transverse beam member 24, this form of attachment provides a very suitable way of transversely distributing what would otherwise be concentrated loads throughout the end plate 23.

A structure embodying the features of this invention is preferably constructed in the following manner: The steel beams are prefabricated according to the configuration of the steel portion shown in FIGURE 1. The anchor blocks of tendons 47 are preferably of the regulatable type to allow adjustment of the preconditioning mechanical load preimposed on the beam as desired. With the beam properly installed, leveled and mechanically preconditioned, concrete is then poured into the channel or trough formed by the juncture of the upper part of the cylindrical beam portion 21 and the vertical side plates 22 to the level of the top edges of the vertical side plates. In most cases it is desirable to use a quick strengthening concrete such as that known in the trade as high-early since this type of concrete has minimum shrinkage and enables quicker construction. Once the channel concrete 30 has adequately hardened the first-stage steel-concrete compound beam achieved has a much greater load-supporting capability. The hardened channel-filling concrete 30 imparts additional stiffness to the steel beam above that afforded by the frame stilfeners 26, which stiffeners from this point on function primarly as steel-concrete connectors. The channel concrete 30 also forms a chemical-physical adhesive bond with the portions of the vertical side plates 22 and the cylindrical beam with which it is in contact as well as with the peripheral surface of the longitudinal tie rods 27 which are disposed in the confines of the channel defined by the surfaces. Since the tie rods 27 are tied into at least the beam ends, they function as additional beam surfaces to increase the area of contact between the channel concrete 30 and the beam.

Immediately after the depositing of the concrete 30 or after it has set properly, shuttering, centering, bracing and Where required propping (not shown) may be constructed as known in the art, for the construction of the deck portion of the bridge. The tendons 49 can then be adjusted to impart the desired preconditioning load to the tension portion of the beam after installation. After finishing the structure, the tendons and the housing of the block connectors 48 are then grouted (not shown) to prevent corrosion and/ or loosening thereof. Preconditioning could, of course, be accomplished prior to formation of the deck portion of the beam but it is important that the grouting be accomplished after completion of the entire structure or preferably with the structure deflected under maximum load so that the grouting is perpetually compressed and therefore crack free and moisture tight. Suitable highly elastic waterproofing members 56 (FIGURE 3) are installed between each of the abutting faces of the bridge deck 32.

Since the concrete deck 32 is poured into the channelfilling concrete 30 surfacent the beam, a physical-chemical adhesive bond is formed between the channel concrete and the deck concrete. This bond is much stronger and much more reliable than the normal bond between concrete and relatively smooth flat steel and the channelfilling concrete and deck concrete therefore function as an integral unit after hardening. The bond between the deck and the beam is further enhanced by the tie rods 27 encased in the deck concrete which function in a manner similar to the tie rods 27 disposed in the channels formed by the beam members to provide additional area of concrete-to-steel contact between the beam and the deck concrete. The frame stilfeners 26 rigidly attached to the steel beam structure and embedded in both the deck and trough concrete function as block-and-tie connectors of the prior art and supported by rods 27 they resist very efiiciently, lifting of the reinforced concrete deck 32 from the steel beam. Asymmetrical loads on the bridge deck tend to destroy the natural steel-concrete contact a bond between the steel and concrete by tension loading but is resisted by tension in framed stiffeners 26. The tie rods 27 are placed within the frame stilfeners 26 and perform another function in addition to that set forth above.

By proper disposition of the tie rods 27 particularly at the concave corners of the frame stiffeners 26, point or line loads, which would normally be imposed by the resistance of the frame stiffeners to lifting of the deck, are distributed throughout the length of the concrete deck by the tie rods 27 thereby reducing the intensity of the compressive loadings imposed on the deck structure itself. The tieing stilfeners 25, although their function as stilfeners is also terminated once the trough concrete 30 has hardened, are formed and disposed to act as conventional block connectors between the concrete deck and the steel beam by resisting shear forces therebetween.

The aforedescribed method of constructing a steel concrete compound beam structure in accordance with the invention is particularly beneficial for use in spans where it is desired to avoid support thereof during the construction process. It would also be possible, but less desirable to complete the pouring of the concrete for both the channel and deck structure in one phase if the beam were suitably propped or supported from below until the concrete is hardened.

It should be obvious that the frame stilfeners 26 may be provided in any form so long as they function as.

stiffeners for channel portions of the beam prior to the formation of the concrete portion of the structure and as connectors to resist lifting of the bridge deck from the beam after final formation of the structure. As such, and depending on the loadings to be imposed thereon, they may be formed of rods or bars in the form of fully closed hoops or open stirrup type retainers and, if so required by design calculation, cross stiflfened with diagonals or other such members. The stiifeners may also be fully immersed within the channels with the top thereof below the upper edges of the side plates 22, immersed within the channel with the top edge thereof flush with the top sides of the vertical side plates 22 or extending from the channels to points near the surface of the concrete slab as shown in the aforedescribed figures. When relatively deep rim tieing or frame stifleners 25, 26 are to be used, apertures should be provided therethrough to accommodate the tie rods 27 so that the rods may be disposed at the required distance from the interface between the concrete and the steel in the channels and, as required, near the top boundary of the concrete slab. According to design requirements, it may be advisable to use the above-described perforated frame stiffeners alternately or intermixed with the frame st-iffeners shown in the aforedescribed figures.

The tie rods 27 may be of the type commonly used in reinforced concrete structures and should be structurally continuous between the ends of the beam. If two or more bars are required to make up one length, the connection should be welded or properly connected so that the connection is of a strength at least equal to the tensile strength of the uninterrupted rod. The tie rods could also be fabricated of steel tubing to function as housing for tendons, rods or cables which could be used in mechanical preconditioning of the beam or post conditioning of the ground beam structure if desired.

The chemical-physical adhesive'bond between the steel components and the concrete components can be enhanced by mechanical means achievable by roughening, grooving or chequering the faces of the steel plates of members which are to come in contact with the concrete and/ or using as the tie rods 27, steel rods or bars of the deformed type. To recapitulate the function of the various components of the structure of this invention:

The frame stilfeners 26 function as stiffeners for the channel-type beam prior to combination of the beam with the concrete component; as exceptionally long and effective block connectors between the beam and the concrete component, as tie connectors between the beam and the concrete component resisting transverse action and, in this function, they react as beam supported at either end as opposed to the free cantilevered beam action of conventional tie connectors thereby reducing the stresses imposed ou the stiffener itself, on the encasing concrete and on the connection point with the beam; as stirrups in connection with the tie rod 27; as transverse shear reinforcement between the beam and the concrete component and as transverse shear connectors resisting and transmitting lateral shearing, flexional and torsional mechanical interaction between the steel beam and the concrete component.

The tieing stiifeners 25 function as cross stiffeners tieing the vertical side plates 22 together and as block connectors between the steel beam and the concrete component. In this latter capacity, the stiffeners 25 may be designed with a minimum profile since their effective length is much greater than that of conventional block connectors. Since the tieing stiffeners 25 are embedded into an exceptionally stifr' portion of the reinforced concrete structure, the stiffeners do not require as much flexional strength as would otherwise be required if they were not so disposed.

The tie rods 27 function as extensions of the surface area of the steel beam to increase the contact area between the beam and the concrete component; as load distributors between the frame stilfeners 26 and the concrete component; as conventional reinforcement for the concrete; as end supports at the intersections of the frame stiffeners 26 and the tieing stiffeners 25; and as elastic tie connectors resisting relative sliding of the beams and the reinforced concrete.

The channels defined by the intersecting surfaces of the cylindrical beam portion 21 and the vertical flat plates 22 are intended to create an artificially enlarged steel-concrete contact surface to increase the strength of the natural chemical-physical adhesive bond between the steel and the concrete; to serve as the mold for the channel concrete 30; to impart the necessary lateral rigidity to the beam before the concrete component is added; and to provide the required lateral flexional and torsional strength and rigidity to the steel-concrete interface by providing a keying surface thereat.

The channel concrete 30 which may be described as a reinforced concrete rib formed between the steel beam and the concrete deck 32, functions to provide the required chemical-physical adhesive bond between the steel beam and the concrete component; to impart the required strength and rigidity to the steel beam to enable support of the concrete deck; to impart additional strength and rigidity to the concrete component; to create lateral fiexional and torsional strength and rigidity in the steel-concrete interface (keying); to stiffen the portion of the steel beam which contacts the reinforced concrete component; to disperse highly concentrated and intensive loads into the structure by distributing the loads over a wider surface area in the structure thereby avoiding undue tensional stresses in the reinforced concrete slabs which would result from such highly concentrated and intensive local action on the slab; and to participate in the total strength and rigidity of the resulting steel-concrete compounded beam structure.

It should also be obvious that the above components of the invention may be suitably combined with beams other than the cylindrical beam described in the aforegoing figures. FIGURES 6 through 11 and 14 through 16 illustrate some of the variations and arrangements possible within the scope of the invention. Portions of these figures corresponding to like components in the preceding figures are indicated by like numerals only of a succeeding higher order.

In FIGURE 6, a substantially box-type beam 221 is provided with a pair of channels in the upper surface thereof defined by vertical part of side plates 222 and upper plate 243. The tendons block connectors 249 are disposed near the lower edge of the beam 221 proximate either transverse side thereof. A deck 232, formed in accordance with the invention as described hereinbefore is connected to the box beam 221 by the natural chemical-physical adhesive bond and the frame stiffeners 226. Tie stiffeners 225 cooperate with the frame stiffeners 226 to provide the necessary rigidity for the channels formed by the members 243 and 222 prior to completing the structure with the trough concrete 230 and the concrete deck 232.

FIGURE 7 shows a similar configuration to that of FIGURE 6, the primary distinction being that the beam 321 is of an open box configuration and the troughs formed by the members 322 and 343 are disposed outwardly of the beam. The shuttering for forming the deck 332 would be installed across the open portion of the beam 321 and would be removed from within the beam after the deck had hardened, if so required.

In FIGURE 8, a semicircular beam 421 is combined with a deck 432. Although the primary distinction in this configuration over the preceding figure is the semicircular form of the beam, it should be noted that the members 443 defining a portion of the channel section of the beam are preferably arcuate and designed to intersect the walls of beam 421 tangentially to avoid bending of the beam hull plate 421.

In FIGURE 9 an inversion of the function of the channel surface in accordance with this invention is shown in the hat-shaped beam 521. Since the channel configuration is intended partially to furnish an increased surface contact area between the concrete and the steel beam, it should be obvious that either side of the channel formed can be used to perform the function. In this case, the channel concrete 530 may be poured With the aid of suitable shuttering or molds to encase the outer portion of the beam 521. The frame stiffeners 526 are disposed on the exterior of the hat-shaped beam and, in combination with the lower tie stiffeners 525, serve essentially the same function as the frame stiffeners of the aforegoing described figures. An additional tieing stiffener 525 can be provided across the upper surface of the beam 521.

FIGURE 10 illustrates what is essentially a conventional I beam 621 modified with vertical side plates 622 to form a channeled I beam.

FIGURE 11 illustrates a further embodiment with angularly disposed side plates 722 mounted on an inverted T beam 721. With the addition of the end frame stiffeners, tie rods and tieing stiifeners and trough concrete in the concrete deck, these latter two beam configurations will function with highly increased effectiveness and ability than would their counterparts conventionally combined with concrete decks.

FIGURE 12 illustrates the basic form of the channel beam. As was adequately set out above, the basic shape of the channel 821 is highly susceptible to cross sectional distortion and has therefore not been fully utilized heretofore in conventional construction. By the simple addition of frame stiffeners 826 the rigidity of the total beam is increased to a point where the beam may be utilized universally with a greater strength and rigidity per unit weight than any of the simple structural shapes now available. These versions can also be used as steel beams with or without compounding it with channel-filling concrete.

In FIGURE 13 a series of beams 921a through 9210 are shown installed in piers 93111 through 9310. to illustrate with more clarity the function of the post tensioning cable 49. The deck portions have been omitted for the purpose of clarity. The beam 9210 is rigidly fixed to the pier 931d and pivotally connected to the pier 931a on the rockers 934. The succeeding beams 921a and 921d are pivotally connected to their respective piers through rockers at both ends thereof and, assuming that the beam 921a is the final end beam at the other side of the bridge structure, the cable 949 is tied thereto at one end and while post tensioned the other end thereof is tied to the beam 9210. This post tensioning procedure is, of course, conducted after the deck portion of the spans has been completed so that, when tension is applied to the cable 949, decks are brought into tight abutting relationship and all spans function together longitudinally as a single unit. This figure also illustrates the four point suspension of the beams 921a and 92112 on the rockers 934, which suspension eliminates the requirement for side bracing or secondary beams to resist overturning of the beams.

Although the aforedescribed figures illustrate single beams in conjunction with the bridge structure, it is of course anticipated that as many beams as required by design calculation can be provided for each of the spans. It should be emphasized, however, that due to the structural characteristics of the channeled steel beams fabricated in accordance with this invention in combination with the suspension arrangement for the beams taught herein, it is possible to fabricate extremely long spans utilizing a single steel beam.

Further modification of the beam structure in accordance with the invention is shown in FIGURE 14. In this modification thechannel shaped beam 1021 is provided with a horizontal, longitudinally disposed diaphragm 1043 plate across the channel intermediate the upper and lower edges thereof while the extensions of the channel beam above the diaphragm plate comprise the equivalents of vertical side plates 1022 for the composite channel forming portion of the beam. As in the prior embodiments, frame stiffeners 1026 are transversely disposed in the upper channel formed by the members 1043 and -22 and tieing stifieners 1025 connect the upper flanges 1051 intermediate the frame stiffeners 1026. This configuration furnishes a rectangular channel beam having a concrete receiving channel formed in the upper portion thereof by the diaphragm 1043.

Referring now to FIGURE 15 of the drawings, the versatility of beams fabricated in accordance with the invention is illustrated in a double-deck type of bridge or span configuration. In this figure, component parts relating to the upper span are sufirxed by a while the corresponding portions of the lower span are suflixed by :b. In this figure, each deck 1132a and 1132b is compounded with a pair of channeled chords 1121a and 1121b respectively. A plurality of trussed webs 1157, vertically disposed in one plane as shown in the drawings and vertically or angularly disposed in the side elevation as is common in the'art, connect the upper beams 1121a with the lower beams 1121b to provide the web portion of the resultant beam. Channel concrete 1130a and 1130b is disposed in the upper and lower beams respectively in a manner similar to that described for the preceding figures, which concrete furnishes the required compressive strength for each of the beams as well as the required natural steel-concrete contact bond between the steel and reinforced concrete of the steel-concrete compound beam. This structure is applicable to doubledeck bridges as well as combined double floored structures in buildings and is particularly useful in the latter application for large unsupported spans in multi-story buildings.

In FIGURE 16, another type beam structure incorporating features in accordance with this invention is illustrated. In this structure, a single deck 1232 is supported by a depending truss structure made up of upper channeled chord 1221a and lower chord 1221b connected by trussed web members 125-7 in the manner somewhat similar to that described in FIG. 15. In this structure, since the lower beam 1221b is essentially in pure tension, and there is no requirement for bonding to any concrete structure, it consists of a box beam and is not combined with concrete as would be the case if it were to be compounded with concrete deck structure. The upper channeled chord 1221a is essentially identical to the upper 14 channeled chord shown and described in a description relating to FIGURE 15 of the drawings.

What has been described above is intended primarily as exemplary to enable those skilled in the art in the practice of the teachings of the invention. The invention may therefore be practiced otherwise than as specifically set forth above and it should be understood that, within the scope of the appended claims, the invention could be practiced otherwise than as specifically set forth above and it should be understood that, within the scope of the appended claims, the invention could be practiced otherwise than as specifically taught.

What is claimed as new and desired to be Letters Patent of the United States is:

1. A beam for resisting the bending effects of loads imposed thereon comprising:

a beam structure;

longitudinal members defining at least one channel with said beam structure;

a plurality of frame stiifeners disposed along and engaging said channel, said frame stitfeners comprising rigid annular hoops at least substantially equal in thickness to said longitudinal members with the sides thereof corresponding to said longitudinal members connected to each member forming said channel and conforming substantially to the cross sectional configuration of said channel.

2. A beam for resisting the bending effects of loads imposed thereon comprising:

a beam structure;

longitudinal members defining at least one channel with said beam structure;

a plurality of frame stiifeners transversely disposed along and engaging said channel, said frame stiffeners being formed of an elongated member at least substantially equal in thickness to said longitudinal members bent to form a closed hoop and to conform substantially with the cross sectional configuration of said channel, said frame stilfeners being connected to said channel along the surfaces thereof which engage said longitudinal members;

and a plurality of longitudinally disposed tie rods engaging said frame stiffeners within the area defined thereby at least at the concave points of curvature formed by the bends in the elongated members forming said frame stiffeners.

3. A beam for resisting the bending effects of loads imposed thereon comprising:

a beam structure;

longitudinal members defining at least one channel with said beam structure;

a plurality of frame stiffeners transversely disposed along and engaging said channel, said frame stiffeners being formed of elongated members at least substantially equal in thickness to 7 said longitudinal members bent to form a closed hoop and to conform substantially to the cross sectional configuration of said channel, said frame stifieners being connected to said channel along the surfaces thereof which engage said longitudinal members;

and a plurality of longitudinally disposed tie rods engaging said frame stiifeners within the area defined thereby at least at the concave points of curvature formed by the bends in the elongated members forming said frame stifieners, said tie rods being substantially coextensive with said beam and rigidly connected thereto at least at either end thereof.

4. A compound concrete-steel beam for resisting the bending effects of loads imposed thereon comprising:

a steel beam structure, longitudinal members defining at least one horizontally disposed channel with said beam structure, and a plurality of frame stiffeners transversely disposed along and engaging said channel, said frame stitfeners comprising rigid annular hoops at least substantially equal in thickness to said protected by and a concrete structure formed on said beam structure in contact with the longitudinal members defin ing said channel to form a natural bond at the interfaces therebetween to maintain connection between the structures against shear forces imposed along the plane of said interfaces, said concrete structure further encasing said frame stiifeners, said frame stiffeners maintaining connection between said structures against mechanical actions of loadings and interfaces and a second concrete deck structure formed on said first concrete structure in contact with the upper surface thereof to form a natural bond at the interface therebetween to maintain connection between said first and second concrete structures against shearing stresses along the plane of the interface between said first and second structures, said first and second structures further encasing said frame stiffeners, said frame stiffeners maintaining connection between each of said structures against forces tending to provide separation thereof in planes other than that of said interfaces.

16 bers extending laterally on each side of said beam, and support means engaging said transverse members proximate each end thereof to provide the entire support for said beam.

8. A compound concrete-steel beam for resisting the bending effects of loads imposed thereon comprising:

a steel beam structure, longitudinal members defining at least one horizontally disposed channel with said beam structure, a plurality of frame stiffeners transversely disposed along and engaging said channel, each of said frame stiifeners being formed of an elongated member at least substantially equal in thickness to said longitudinal members 'bent to form an annular hoop and to conform substantially to the forces tending to provide separation thereof in planes cross sectional configuration of said channel, said other than that of said interfaces. frame stiifeners further being connected to said chan- 5. A compound concrete-steel beam for resisting the nel along the surfaces thereof which engage said bending effects of loads imposed thereon comprising: longitudinal members, and a plurality of longitudi- & Steel beam Structure, longitudinal members dfifining nally disposed tie rods engaging said frame stiffeners at least one horizontally disposed channel with said 20 ithi h area d fi d h b at least at h beam Structure, and a plurality of frame stittenel's cave point of the bends in the elongated member transversely disposed along and engaging said chanforming Said frame stiffener; 531d frame CmPn smg ,ngld and a concrete structure formed on said beam structure hoops at least substantially equal 1 thlckness to Said in contact with the lon itudinal members defining said longitudinal members with the sides thereof correchannel to form a natural bond at the interfaces spending to Said longitudinal members Connected to therebetween to maintain connection between the each member forming said channel and conforming substantially to the cross sectional configuration of structllresf against Sheffmng Stress along the planes said channel and projecting upwardly th f of sa d interfaces, said concrete structure further and a first concrete structure formed on said beam struceflcaslng sttld frame stflffllers and said longitudinal ture in contact with the longitudinal members defin- P Sald frame snficners and Sald tie rods j ing said channel to substantially fill said channel and tammg connectlPn between the Structures agam'st form a natural bond at the interfaces therebetween bond Stress tendlng to prolide separation thereof to maintain connection between the aforesaid struc- PlaneS other than that of Said interfacestures against shearing stress along the plane of said 9. A beam in accordance with claim 8 wherein transverse members are connected to the ends of said beam proximate the upper portion thereof, said transverse members extending laterally on each side of said beam ends, and support means engaging said transverse members proximate each end thereof to provide the entire support for said beam.

10. A compound steel-concrete beam for resisting the bending effects of loads imposed thereon comprising:

a steel beam structure, longitudinal members defining at least one horizontally disposed channel with said beam structure, a plurality of frame stiffeners transversely disposed along and engaging said channel, said frame stiifeners being formed of an elongated member at least substantially equal in thickness to said longitudinal members bent to form a closed annular 6. A compound concrete-steel beam for resisting the bending effects of loads imposed thereon comprising:

a steel 'beam component, longitudinal members defining at least one horizontally disposed inverted channel with said beam component, and a plurality of frame stiifeners transversely disposed along and engaging the outer surfaces of said channel, said frame stiffeners projecting above said beam and conforming substantially to the cross sectional configuration of the outer surfaces of said channel, said frame stiffeners further being connected to said longitudinal members hoop and to conform substantially to the cross sectional configuration and to extend above the confines of said channel, said frame stiffeners being connected to said channel along the surfaces thereof which engage said longitudinal members, and a plurality of longitudinally disposed tie rods engaging said frame stiifeners within the area defined thereby at least at the concave point of the bends in the elongated memalong the surfaces thereof which are in engagement r f rming Said frame stiffener; therewith; and a first concrete structure formed on said beam and a concrete component formed on said beam comstructure in contact with the longitudinal members depone-nt in contact with the outer surfaces of the fining said channel to substantially fill said channel longitudinal members defining said channel to form a 6,, and encase the portion of said tie rods disposed in natural bond at the interfaces therebetween to main- 0 said channel to form a natural bond at the interfaces tain connection between the components against therebetween to maintain connection between the shearing stress along the plane of said interfaces, said aforesaid structures against shear forces imposed concrete component further encasing said frame stiffalong the planes of the interfaces, and a second concners to maintain connection between said compo- 7O crete deck structure formed on said first concrete nents against forces tending to provide separation structure in contact with the upper surface thereof to thereof in planes other than that of said interfaces. form a natural bond at the interface therebetween 7. A beam in accordance with claim 4 wherein transto maintain connection between said structures verse members are connected to the ends of said beam against shearing stress along the plane of the interproximate the upper portion thereof, said transverse memface between said first and second structures, said first and second structures further encasing said frame stiifeners and said tie rods, said frame stiffeners and said tie rods maintaining connection between each of said structures against forces tending to provide separation thereof in planes other than that of said interfaces. 7

11. A compound concrete-steel beam for resisting the bending effects of loads imposed thereon comprising:

a steel beam component, longitudinal members defining at least one horizontal inverted channel with said beam component, a plurality of framed stitfeners transverselydisposed along and engaging the outer surfaces of said channel, said frame stilfeners being formed of an elongated member bent to project above said beam and conform substantially to the cross sectional configuration of the outer surfaces ofsaid channel, said frame stiffeners further being connected to said channel along the sufaces thereof which'engage said longitudinal members, and a plurality of longitudinally disposed tie rods engaging said frame stiffeners within the area defined thereby at least at the concave point of curvature formed by the bends in the elongated member forming said frame stiffener;

and a concrete component formed on said beam component in contact with the outer surfaces of the longitudinal members defining said channel to form a natural bond at the interfaces therebetween to maintain connection between the components against shearing stress along the plane of said interfaces, said concrete component further encasing said frame stitfeners and said tie rods to maintain connection between said components against forces tending to provide separation thereof in the planes other than that of said interfaces. 7

12. A compound steel-concrete beam for resisting the bending effects of loads imposed thereon comprising:

a steel beam structure, longitudinal members defining at least one horizontally disposed channel with said beam structure, a plurality of frame stitfeners transversely disposed along and engaging said channel, each of said frame stiifeners being formed of an elongated member at least substantially equal in thickness to said longitudinal members bent to conform substantially to the cross sectional configuration of said channel, said frame stiifeners further being connected to said channel along the surfaces thereof which engage said longitudinal members, and a plurality of longitudinally disposed tie rods engaging said stifieners within the area defined thereby at least at the concave point of the bends in the elongated member forming said frame stiffener, said tie rods being substantially coextensive with said beam and at least a part of them rigidly connected thereto at least at the ends thereof;

and a concrete structure formed on said beam structure in contact with the longitudinal members defining said channels and to encase said tie rods to form a natural bond at the interfaces therebetween to maintain connection between the structures against shearing stressalong the plane of said interfaces, said concrete structure further encasing said frame stiffeners so that said frame stiffeners in combination with said tie rods maintain connection between the structures against forces tending to provide separation thereof in planes other than that of said interfaces.

13. A compound concrete-steel beam for resisting the bending effects of loads imposed thereon comprising:

a steel beam structure, longitudinal members defining at least one horizontally disposed channel with said beam structure, a plurality of frame stifieners transversely disposed along and engaging said channel, each of said frame stiifeners being formed of elongated members at least substantially equal in thickness to said longitudinal members bent to conform generally to the' cross sectional configuration of and to extend above the confines of said channel, said frame stilfeners being connectedsto said channel along the surfaces thereof which engage said longitudinal members, and a plurality of longitudinally disposed tie rods engaging said frame stilfeners within the area defined thereby at least at the concave points of curvature formed by the bends in the elongated members forming said frame stiifeners, said tie rods being substantially coextensive with said beam and rigidly connected thereto at least'at'the ends thereof; and a first concrete structure formed on said beam structure in contact with the longitudinal members defining said channel to substantially fill said channel and encase the tie rods disposed therein to form a natural bond at the interfaces therebetween to maintain connection between the aforesaid structures against shear forces imposed along the plane of said interfaces, and a second concrete deck structure formed on said first concrete structure in contact with the upper surface thereof and encasing the tie rods disposed above the confines of said channel to form a natural bond at the interfaces therebetween to maintain connection between said first and second concrete components against shearing stress along the plane of the interfaces between said first and second components, said first and second concrete structures further encasing said frame stiifeners so that said frame stiffeners in combination with said tie rods maintain connection between each of said structures against forces tending to provide separation thereof in planes other than that of said interfaces.

14. A compound concrete-steel beam for resisting the bending effects of loads imposed thereon comprising:

a steel beam component, longitudinal members defining at least one horizontally disposed inverted channel with said beam components, a plurality of frame stiffeners transversely disposed and engaging the outer surfaces of said channel, each of said frame stitlfeners being formed of elongated members bent to project above said beam and conform substantially to the cross sectional configuration of the outer surfaces of said channel, said frame stilfeners further being connected to said channel along the surfaces thereof which engage said longitudinal members, and a plurality of longitudinally disposed tie rods engaging said frame stiifeners within the area defined thereby at least at the concave points of curvature formed by the bends in the elongated member forming said frame stiffener, said tie rods being substantially coextensive with said beam and at least a part of which rigidly connected thereto at least at either end thereof; and

a concrete component formed on said beam component in contact withthe outer surfaces of the longitudinal member defining said channel and encasing said tie rods to form a natural bond at the interfaces therebetween to maintain connection between the components against shearing stress along the plane of said interfaces, said concrete component further encasing said frame stiffeners so that said frame stiffeners in combination with said tie rods maintain connection between the components against forces tending to provide separation thereof in planes other than that of said interfaces.

15. A beam in accordance with claim 12 wherein transverse members are connected to each end of said beam proximate the upper portion thereof, said transverse mem- 70 bers extending laterally on each side of said beam, and

support means engaging the transverse members proximate each end thereof to provide the entire support for said beam.

(References on following page) References Cited UNITED STATES PATENTS Baldwin 14-1 Rogers 52-339 Grady 525 82 Thomas 52 582 Henderson.

Farham et a1. 52436 Maddock 1416 Leisner 52251 VanderHeyden 52433 Naillon 52225 Silberkuhl et a1 52723 FRANK L. ABBOTT, Primary Examiner.

FOREIGN PATENTS Canada. France. France. France.

Great Britain. Great Britain. Great Britain. Great Britain. Switzerland.

J. L. RIDGILL, Assistant Examiner.

Claims (1)

1. 5. A COMPOUND CONCRETE-STEEL BEAM FOR RESISTING THE BENDING EFFECTS OF LOADS IMPOSED THEREON COMPRISING: A STEEL BEAM STRUCTURE, LONGITUDINAL MEMBERS DEFINING AT LEAST ONE HORIZONTALLY DISPOSED CHANNEL WITH SAID BEAM STRUCTURE, AND A PLURALITY OF FRAME STIFFENERS TRANSVERSELY DISPOSED ALONG AND ENGAGING SAID CHANNEL, SAID FRAME STIFFENERS COMPRISING RIGID ANNULAR HOOPS AT LEAST SUBSTANTIALLY EQUAL IN THICKNESS TO SAID LONGITUDINAL MEMBERS WITH THE SIDES THEREOF CORRESPONDING TO SAID LONGITUDINAL MEMBERS CONNECTED TO EACH MEMBER FORMING SAID CHANNEL AND CONFORMING SUBSTANTIALLY TO THE CROSS SECTIONAL CONFIGURATION OF SAID CHANNEL AND PROJECTING UPWARDLY THEREFROM; AND A FIRST CONCRETE STRUCTURE FORMED ON SAID BEAM STRUCTURE IN CONTACT WITH THE LONGITUDINAL MEMBERS DEFINING SAID CHANNEL TO SUBSTANTIALLY FILL SAID CHANNEL AND FORM A NATURAL BOND AT THE INTERFACES THEREBETWEEN TO MAINTAIN CONNECTION BETWEEN THE AFORESAID STRUCTURES AGAINST SHEARING STRESS ALONG THE PLANE OF SAID INTERFACES AND A SECOND CONCRETE DECK STRUCTURE FORMED ON SAID FIRST CONCRETE STRUCTURE IN CONTACT WITH THE UPPER SURFACE THEREOF TO FORM A NATURAL BOND AT THE INTERFACE THEREBETWEEN TO MAINTAIN CONNECTION BETWEEN SAID FIRST AND SECOND CONCRETE STRUCTURES AGAINST SHEARING STRESSES ALONG THE PLANE OF THE INTERFACE BETWEEN SAID FIRST AND SECOND STRUCTURES, SAID FIRST AND SECOND STRUCTURES FURTHER ENCASING SAID FRAME STIFFENERS, SAID FRAME STIFFENERS MAINTAINING CONNECTION BETWEEN EACH OF SAID STRUCTURES AGAINST FORCES TENDING TO PROVIDE SEPARATION THEREOF IN PLANES OTHER THAN THAT OF SAID INTERFACES.

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