US3624980A

US3624980A - Composite end connection for steel joists

Info

Publication number: US3624980A
Application number: US10399A
Authority: US
Inventors: Ira J Mcmanus
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-02-11
Filing date: 1970-02-11
Publication date: 1971-12-07
Anticipated expiration: 1988-12-07

Abstract

A COMPOSITE ACTION JOIST END INTERCONNECTION WITH A SUPPORTING BEAM AND CARRYING A CONCRETE SLAB IS DESCRIBED. AN OUTWARDLY-EXTENDING END PORTION OF THE TOP CHORD OF A STEEL JOITS IS PROVIDED AT THE UNDERSIDE WITH BEARING MEANS ADAPTED TO SEAT UPON AND BE SECURED TO THE SUPPORTING BEAM, WHEREBY, WHEN THE SUPPROTED CONCRETE SLAB IS POURED IN PLACE IN SUCH MANNER AS TO EXTEND OVER AND

UPON THE SUPPORTING BEAM, THE JOIST END INTERCONNECTING THEREWITH IS ENCASED WITHIN THE SLAB CONCRETE TO EFFECT THE COMPOSITE ACTION BETWEEN THE SUPPORTING STEEL AND THE CONCRETE.

Description

Dec- 7, 1971 l. J. MCMANUS COMPOSITE END CONNECTION FOR STEELIJOISTS Filed Feb. 11, 1970 6 ShGatsSheet 1 Dec. 7, 1971 1 MCMANUS COMPOSITE END CONNECTION FOR STEEL JOIsTs Filed Feb. l1, 1970 .3 ShOatS-ShOet 2 /A/l/E/VTO? 5 /PQ d. ma MAJ/UUS /77 70K/WV 7, 1971 l. .1. MCMANUS COMPOSITE END CONNECTION FOR STEEL JOISTS Filed Feb. 11, 1970 5 Sheets-Shoot 3 m T N E V. m

lUnited States Patent O 3,624,980 COMPOSITE END CONNECTION FOR STEEL JOISTS Ira I. McManus, 39 Lincoln Ave., Flor-ham Park, NJ. 07940 Filed Feb. 11, 1970, Ser. No. 10,399 Int. Cl. E04b 1/16, 5/29 U.S. Cl. 52-327 9 Claims ABSTRACT OF THE DISCLOSURE In my U.S. Pat. .No. 3,392,499, issued July 16, 1968, and in my co-pending patent application, Ser. No. 751,- 930, led Aug. 12, 1968, now Pat. No. 3,527,007 there are described various improvements in the connections between the ends of open-web steel joists and the steel beams or girders supporting them, whereby there is achieved composite action between the supporting beam or girder and a concrete slab poured over the joists and in bearing relation upon the supporting beam. The present invention is directed to improvements over the steel joist end connections disclosed therein.

In my above-described patent and patent application, I disclose end connections for steel joists enabling the top chord of the joist to be placed substantially level with the top flange of the supporting steel girders or beams, permitting marginal portions of the concrete slab floor to be placed in bearing relation upon top portions of the girder or beam and thereby effecting rigid composite interconnection of the floor slab with the girder or beam to act in unison therewith for increasing the rigidity of a Hoor or roof system. To accomplish this end, -vertical shear plate members are welded with respect to and extending upwardly of the top chord of a steel joist in spaced relation with the outer end thereof, and a horizontally extending bed plate member is secured against the end of the joist to connect with the supporting framework girder or beam by seating upon the top flange thereof, the arrangement being such that the top chord of the joist is substantially at the same level as the top of the supporting beam. In such construction, the shear device used to gain the composite action is above the top of the top chord of the joist, where it was encased in the subsequently poured concrete slab.

It is the principal object of this invention to effect composite action between the supporting steel and the concrete in a steel joist to steel beam or girder end connection by encasing the end of the top chord of the joist in the concrete slab and using the joist end so encased as the shear connector. In the present invention, therefore, the top of the joist top chord is above the top of the supporting beam or girder rather than at substantially the same level.

It is a more particular object to provide an improved end connection for open-web steel joists wherein the underside of an outwardly-extending end portion of the top chord of the joist is provided, at its underside, with a bearing member adapted to be seated upon and welded 3,624,980 Patented Dec. 7, 1971 ICC to the upper flange portion of a supporting beam or girder whereby, upon pouring of the slab to be supported by the girders and in overlying bearing relation upon said top flange, the joist end connection mechanism will be encased in the slab cement to effect the desired composite action.

Other objects, features and advantages of the invention will be apparent from the following description when read with reference to the accompanying drawings. In the drawings, wherein like reference numerals denote corresponding parts throughout the several views:

FIG. l is an isometric view of a joist end connection embodying the invention shown connected to a support girder and further showing the use of form plates therewith for forming a concrete oor slab over a series of steel joists;

FIG. 2 is a longitudinal cross-sectional view illustrating the end connection of FIG. 1 encased in a concrete slab;

FIG. 3 is a view similar to FIG. 2 on an enlarged scale and before pouring the concrete slab, illustrating mechanical details of the joist end connection;

FIG. 4 is a vertical cross-sectional view taken along the line 4-4 of FIG. 3 in the direction of the arrows and further illustrating mechanical details of the joist end connection;

FIG. 5 is a partial side elevational view, similar t0 that of FIG. 3 but showing a modified form of joist end connection embodying the invention;

FIG. 6 is a plan view, with portions broken away, taken along the line 6-6 of FIG. 5 in the direction of the arrows;

FIG. 7 is a vertical cross-sectional view, similar to that of FIG. 4, but illustrating a modified form of the keying member; and

FIG. 8 is still another View similar to that of FIG. 4 but illustrating a modified form of beam bearing member.

Referring now in detail to the drawings and considering rst the embodiment of the invention illustrated in FIGS. 1 through 4, numeral 10 designates a typical openweb steel joist comprised of a pair of angle-irons 11, 12 welded opposedly along the apices at one side of a zigzag bar web 13 to form the top chord of the joist, and a pair of angle-iron members 14, (only one shown in FIG. 2), welded opposedly along the apieces at the other side of the bar web 13 to form the bottom chord of the joist. in accordance with the present invention, the projecting outer end of the top chord of the joist 10, encased in concrete as is hereinafter described, is used as a composite shear-connected end connection. To this end, a pair of short angle-

shaped iron members

15, 16 are arranged together in U-shape below the outer end portions of the top chord angle-irons 11, 12, and are welded along their upper edges to outer edge portions of said top chord angle-irons to provide a box-like bearing member 17. The bearing member angle-

irons

15 and 16 may extend somewhat `beyond the outer ends of the upper chord angleirons 11, 12 to enhance encasement by the concrete. An upwardly-extending headed key pin 18 is secured, as by welding, to the top chord comprising the angle-irons 11 and 12, said key pin preferably being of such size as to fit snugly between said angle-irons, whereat it can be conveniently welded.

It is to be understood that the above-described end connection for joist 10 will be fabricated in the shop so that the assembly need merely be set in place between the supporting steel structure and welded thereto. FIG. l illustrates, by way of example, how the end connection at one end of the joist 10 is joined by welding, as indicated at 19, to the top flange of a girder or beam 20. FIGS. l through 3 illustrate how the end connection is so seated upon the top flange of the girder or beam 20 that the outer end of the top chord of the joist overlies said flange so that the loading forces thereat will be in shear.

The usual sheet metal form plate 21 placed on the erected joist form the bottom of a concrete slab 22 (sec FIG. 2). The form plates 21 extend fully to the outer end of the joist top chord, in the vicinity of the upstanding keying member 18, and are cut along each side of the end connection bearing member 17 to permit form plate portions between joists to be bent down into contact with the top flange of the supporting girder or beam 20 (see FIGS. 1 and 2). To further enhance encasement of the joist end in the concrete and the form plate 21 between the side cuts and resting on the top chords of joist 10 may be removed. As is best illustrated in FIG. 2, such installation of the metal form plates 21 permits the poured concrete of the slab 22 to encase the outer end of the joist end connection carrying the shear loading to allow composite action between the supporting girder or beam 20 and the concrete slab. In this connection, it will be understood that the horizontal portions of the angle-iron members '15 and 16 serve as bearing plates and the vertical portions serve as closure plates to stiften the joist end and to provide the shear capacity necessary to allow composite action to take place. The Vertical portions of the angle-

irons

15, 16, additionally, serve to close off the joist end against leakage of the concrete around the joist during pouring of the slab.

FIGS. 5 and f6 illustrate a modification of the invention shown in FIGS. l through 4 wherein, instead of utilizing a headed pin 18 as a keying member for interlocking with the poured concrete slab, such keying action is provided by an integral extension portion 23- of the zig-zag bar web 13 or a separate bent bar. As best illsutrated in FIG. 5, the extension portion 23 comprises a vertically upwardly-extending portion 24 merging into a horizontallyextending terminal hook portion 25 of such size and configuration as to be embedded at a substantially central vertical position in the slab when poured. The embodiments of FIGS. 5 and 6 also illustrate how inner end portions of the vertical portions of the angle-iron members and 16 can be cut and bent inwardly against the vertical portions of their respective top chord angle-irons 11 and 12 to close off the inner ends of the bearing member 17 against concrete leakage upon pouring of the concrete slab.

FIG. 7 illustrates another modification of the invention, differing from the embodiment illustrated in FIGS. l through 4 only in that, instead of utilizing a headed pin keying mem-ber 18, or a bent bar 23 in FIG. 5, an inverted U-shaped bar 26 is used, the outer ends of the legs of said bar being welded in straddling relation across and above the outer end of the top chord comprising angle-irons 11 and 12. As illustrated in FIG. 7, the U- shaped bar 26 will preferably be of such height as to extend upwardly approximately into the center of the thickness of the concrete slab to be poured.

FIG. 8 illustrates still another modification of the invention differing from the embodiment illustrated in FIGS. l through 4 in that, instead of utilizing two

angleiron members

15 and 16 to for-m the bearing member 17, an integrally formed, inverted U-shaped channel member 27 is used. With such construction, as illustrated, the height of the bearing structure can be increased beyond that afforded by the compo-site bearing member 17 of FIGS. 1 through 3, if desired; for example, if a slab of increased thickness is to be poured. With this construction, additional rigidity can be obtained by extending the terminal end portion 28 of the zig-zag bar web 13 to meet the web or bottom wall of the U-shaped member 27, whereat it can be welded as indicated in 29. A keying member consisting of a pin 18, bent bar 23, or stirrup 26 is added to provide the necessary locking of the concrete to the joist end.

While I have illustrated and described herein several forms in which my invention can conveniently be ernbodied in practice, it is to be `understood that these forms are presented by way of example only and not in a limiting sense. Thus, while the steel joists herein illustrated and described are :fabricated of welded-together steel angleiron and rod members, it is to be understood that other types of steel joists fabricated of steel members having other shapes could as well lbe used in combination with the composite end joint embodying this invention. The invention, in brief, includes all the forms and embodiments coming within the scope and lspirit of the following claims.

What I claim as new and desire to secure by Letters Patent is:

1. In a steel joist construction and connection therefor, the combination comprising, a beam, a steel joist having an elongated top chord, an elongated bottom chord and web means interjoining said top and bottom chords and securing them in interspaced relation, said top chord having a composite end portion extending outwardly beyond its associated bottom chord at at least one end of said joist, a bearing member fixed against the underside of the outwardly-extending composite end portion and secured against the top surface of said beam and supporting said end of said joist, said elongated top chord comprises a pair of spaced, parallel angle iron members having horizontal flange portions in a common plane defining the top surface of said top chord, said bearing member comprising channel means having a web and two upstanding leg portions, the upper ends of said two leg portions being secured respectively to the outer edges of the angle irons forming the horizontal flange portions, and impervious corrugated deck form means lying upon the top surface of said steel joist and having end portions bent downwardly at each side of said bearing member to the plane of the seating surface thereof, and resting on said beam surface, a concrete slab portion formed over said slab form means, said bearing member and said beam surface supporting said end of said joist encasing said bearing member and said steel joist end portion to effect composite action between the joist end connection and the concrete slab, said composite end portion including key means extending upwardly therefrom for interlocking action between the concrete slab and joist end connection.

2. A steel joist construction and end connection therefor as defined in claim 1, wherein said bearing member com-prises a pair of short angle-shaped iron members symmetrically arranged and welded in a box-like configuration with respect to the underside of said end p0rtion of said top chord.

3. A steel joist construction and end connection therefor as defined in claim 1, wherein said bearing member' comprises an inverted, U-shaped channel symmetrically arranged and welded in a box-like conguration with respect to the underside of said end portion of said top chord.

4. A steel joist construction and end connection therefor as defined in claim 1 wherein said key means comprises a headed pin.

5. A steel joist construction and end connection therefor as defined in claim 1 wherein said key means is in the fform of an inverted U-shaped bar.

6. A steel joist construction and end connection therefor as defined in claim 1 wherein said web ymeans comprises a zig-zag shaped bar and wherein said key means comprises an end portion of said bar extending yupwardly of the outer end of said outwardly-extending end portion of said top chord to enhance interlocking action between the concrete slab and the joint end connection.

7. A steel joist construction and end connection there- -for as defined in claim 2 wherein inner end portions of the vertical flange portions of said short angle iron members are bent inwardly in the direction of the vertical flange portions of said top chord angle iron members.

8. A steel joist construction and end connection therefor as defined in claim 2 wherein said short angle iron members extend outwardly beyond said angle iron members of said top chord.

9. A steel joist construction and end connection therefor as dened in claim 3 wherein 'said U-shaped channel extends outwardly beyond said angle iron members of 5 said top chord.

References Cited UNITED STATES PATENTS 6 Young 52-334 Sahlberg 52-334 Davis 52-334 Macomber 52-692 McManus 52-334 X McManus 52-483 X U.S. Cl. X.R.