US 3177619 A
Description (OCR text may contain errors)
April 13, 1965 1. A. BENJAMIN REINFORCED CONCRETE SLAB AND TENSION CONNECTOR THEREFOR INVENTOR. IRWIN A. BENJAMIN ATTORNEYS Filed June 29, 1962 United States Patent 3,177,619 REINFORCED CONCRETE SLAB AND TENSION CONNECTOR THEREFOR Irwin A. Beniarnin, University City, Mo., assignor to Granite City Steel Company, Granite City, IlL, a corporation of Delaware Filed June 29, 1962, Ser. No. 2%,362 1 Claim. (Cl. -290) This invention relates to improvements in means for connecting reinforced concrete slabs to metallic load bearing members whereby the components are made to act together or compositely.
Standard practices heretofore have involved placement of reinforced concrete slabs on steel beams such that the slabs and beams do not coact as a unitary assembly, but the beams alone carried all of the vertical loads transferred thereto by the slabs. Attempts have been made to prevent movement between the slabs and beams by the use of shear devices disposed in the body of concrete and secured to the reinforcing means or to the beams. Such devices act in flexure to develop very high stresses and usually result in failures by crushing of the concrete at the face of the devices. The high flexural stresses in these devices are generally developed close to the junction of the beam and decrease at a very rapid rate farther from the beam such that reverse bearing stresses are imposed in the slab, demonstrating that these devices act in bending and are ineflicient.
It is an object of the present invention to provide a more eflicient and more economical tie-in or connector between a reinforced concrete slab and its supporting beam and to form a connection to the beam at the same time for erection security during the pouring of the concrete.
it is also an object of the present invention to provide an improved connector for a reinforced concrete slab such that the stresses are taken in tension in the connector or in shear at the attachment to the beam, thereby eliminating the need for developing flexural resistance in the connector.
A further object of this invention is to provide an improved tension connector forreinforced concrete slabs and supporting beams such that stresses may be accurately controlled to react in tension in the connectors or shear at the zone of attachment, and so that a balanced distribution between tension and shear can be obtained as will be more particularly set forth.
Other objects and advantages of the present invention will appear as the description of preferred forms of the invention proceeds. It is a preference to form the tension connector of sheet material having a base portion to fit in the concrete reinforcement and a tension arm extending angularly into the body of the concrete to control the stresses for tension in the arm. The tension connector base, while formed to fit the reinforcement, provides means to control the shear stresses such that the shear stresses at the base may be balanced with tension stresses in the arm, whereby failure of the connector may be predicted for either tension in the arm or shear in the attachment of the base. The preferred embodiments of this invention have been illustrated in the accompanying drawings, wherein:
FIG. 1 is a sectional elevational view of a beam supported concrete slab of reinforced character illustrating one form for the improved tension connectors;
FIG. 2 is a sectional elevational view seen at line 22 in FIG. 1;
FIG. 3 is an enlarged and fragmentary perspective view of a tension connector and reinforcing means for the concrete slab;
FIG. 4 is a greatly enlarged and fragmentary sectional 3,177,519 Patented Apr. 13, 1965 view through the reinforced concrete slab to show the action of the tension connector;
FIG. 5 is a fragmentary perspective view of a portion of the assembly prior to pouring the concrete; and
FIG. 6 is a fragmentary view of a modification of the present connector means.
in FIG. 1 the reinforced concrete slab assembly is seen to comprise a beam 1% of any suitable shape, such as an I beam, the beam 10 being carried by spaced primary load bearing members 11. The beam 10 carries the end portions of a series of metallic corrugated sheets 12 having the longitudinal sides in overlapped relation to provide a complete form for the concrete material 13 which is placed thereon in plastic condition in the usual manner. Each of the sheets 12 is provided with spaced reinforcing bars 14 directed transversely of the crests of the corrugations and secured to each such crest by welding the bars thereto.
The end margins of the corrugated sheets 12 are placed on the flange 145a of the supporting beam 10 to provide a desired bearing contact therewith, as shown in FIGS. 2 and 3. After a series of sheets 12 have been placed spanning tWo adjacent beams 19 they are secured to the beam flanges 10a by welding the end portions. The welding is accomplished at the time the tension connectors 16 are placed so that the concrete 13 after pouring and setting will be made to act compositely with the beams 10. Each connector 16 is formed from strip material to provide a base end 18 which seats in the valley between two crests 15. The connector includes an arm 19 which extends upwardly from the base 18 at an angle A from a horizontal and varying from about 60 to 90, it being determined that the preferred angle A should be about such that stresses experienced by the connector shall be substantially in tension. It is a further characteristic of the connector 16 to provide an angular element 21 at its outer end with such element 20 being substantially at to the arm 19. It has been found that the angular orientation of arm 19 of each tension connector 16 effectively develops tension stress, While the angular element 219 develops vertical resistance. Since the arm 159 is designed flexurally weak and therefore tends to rotate from the base 18 (see broken line position of FIG. 4), tension is maintained.
In placing the tension connectors 16 (FIG. 1) the angular elements 20 of one series thereof are oriented or turned to face away from the center or midspan of beam 19, while the other series are oppositely oriented or turned. This orientation causes the connector arms 19 to tend to rotate downwardly (FIG. 4) as bending occurs in the beam Iii under loading, with the result that the concrete bearing sets up stresses in the direction of arrows S. Since the angular element 20 is substantially locked against movement in the concrete 13 the resultant stress in the connector arm 19 is taken in tension, and shear stress is created in the welds W at the base 18.
It is seen in FIG. 3 that the connector base 18 is seated in a valley of the corrugated sheet 12 and Welds W are made along the opposite edges of the base 18. Moreover, at least one weld W is made through the corrugated sheet 12 to the beam flange 10a (FIG. 2) so that the sheet is secured to the beam flange 10a at the same time. The welds W are in the form of fillets and suflicient weld material is deposited to provide a shear connection having shear stress resistance at least balanced with the tension stress loading expected in the connector arm 19, but the weld fillet shear stress resistance may be made greater so that any failure of the connector 16 shall be in tension to avoid crushing the concrete 13.
A modified tension connector 21 is illustrated in FIG. 6, wherein the base 22 thereof has recesses 23 in one edge or both of its opposite edges to increase the length of the Welds W and thereby increase the shear stress resistance. In referring to recesses'23 it is intended that [the term shall also include apermre type openings between the edges for receiving weld fillets. The arm 24 and outer angular end element 25 of the modified connector are substantially like those described for the tension connector 16, and'the'manner of its use is the same. H p v 7 It has been'found from tests that'the connectors 16 or 21 may be madefrom. 1 2 gage sheet metal having a Width of 1 /2", withthe arms 19 or 24 approximately 3" long and the angular elements '20 or 25 at the outer end about /2" long and turned to lie at about 90 to the axis of the arms. The size of the base portions 18 or 22 is governed by the dimensional configuration ofthe corrugated sheets "'12. A tensionconnector of the form shown at either 16 or 21' has the advantage'that the stress loading in tension can be varied'b-y increasing or decreasing the gage of the sheet metal, and the shear stress resistance can be correlated with the tension stress by providing one or morev straight welds W as in FIG. 3 or one or more elongated welds as in FIG. '6. Testshave further shown that the present tension connectors are more efiicient than the Ipresently known connectors in preventing damage to the concrete, in effecting composite action and coaction-between the reinforced concrete slab and the supporting beams, and in controlling the stress patterns within the assembly.
The foregoing disclosure has been given in connection with certain preferred embodiments of tension connectors for reinforced concrete slabs, but it is understood that the embodiments herein may be altered in size, proportion and location without in any way departing from the broad principle of its action and eifect in composite reinforced concreteslab construction, While the present disclosure has included one example ofa corrugated shut and reinforcing rod type of form for the plastic concrete which later becomes the reinforcement for the solidified concrete, it is understood that other forms and reinforcement components may be employed without departing from the "improvements herein shown. It is, therefore, the aim to include all'possible 'forms' andaequivalent embodiments in theappe'nded claim.
' What is claimed is: In a reinforced-concrete floor slab assembly, principal "support means in spaced parallel' relation, beamniembers carried by said support means in spaced horizontal r'elation spanning the 'distance'between support means, a plurality of form and reinforcing corrugated sheets'having' end portions resting on said beam members with the corrugation crests and valleys directed transversely to said beam members, a plurality of T individual connector elements each formed of fiat strip material with a base end turned to seat in a corrugation valley and an arm extending angularly from 'the' baseendlto *an outer end bent at right angles to said arm 'and oppositely to said turned base end,
, said 'c'onnectorelerr'ients"being-placed in corrugation valleys adjacentthei'end' portions'of said sheets and across the length of said beam span between said support means, theangularly extending arms of said connector elements on each side of'the' mid fspan ofsaid'beam members being oppositely oriented and extending. above the corrugation crests, and each base end of said connector elements being formed with'rece's sed edges of non linear form to receive weldments,'weldments coi'in'ecting said'recessed edges of said base end of said connector elements to the adjacent end portion-of said corrugated sheets and-to said beam members, said weldments-forming tensile load and shear stress connections with said beam members and fixing said base,endsoffthe-connector elements in position, and a body of concrete material carried by, said corrugated sheets filling said valleys and extending-to a height above said crests to fullycover' and surround said angularly extending armsand outer'bent ends thereof, the angularity of each said arm of said'connector elements being from to degreesto the horizontal direction of said beam members totransmit tension stresses into said weldments and connect said body of concrete to said sheets and beam members.
Rfernces Citedbyithe Examiner UNITED 5 STATES PATENTS JACOB L; NACKENOEF, Primary Examiner. HENRY c'. SUTHERLAND, Examiner.