US3195277A - Prestressed concrete slab construction - Google Patents

Description

G. G. GREULICH PRESTRESSED CONCRETE SLAB CONSTRUCTION Original Filed June 27, 1957 July 2o, 1965 4 Sheets-Sheet 1 Il Il fil/l AJuly 20, 1965 G. G. GREuLlcH PRESTRESSED CONCRETE SLAB. CONSTRUCTION Original Filed June 27. 1957 4 Sheets-Sheet 2 July 20, 1965 G. G. GREULICH 3,195,277

PREsTREssED CONCRETE SLAB CONSTRUCTION Original Filed June 27, 1957 4 Sheets-Sheet 3 July 20, 1965 G. G. GREULICH 3,195,277

PRESTRESSED CONCRETE SLAB GONSTRUGTION Original. Filed June 27, 1957 4 Sheets-Sheet 4 Y j? 5:9 v 5 5.?

/l L K 1 n J KP IHIHI 64 JZ I J2 5 9 'Il 55 l|||| f7 forneys- United States Patent O 3,195,277 PRESTRESSED CON-CRETE SLAB CONSTUCTION Gerald G. Greulich, Fort Lauderdale, Fla., assignor to The Ceco Corporation, a corporation of Delaware Original application June 27, 1957, Ser. No. 668,506, now Patent No. 3,036,356, dated May 29, 1962. Divided and this application June 16, 1961, Ser. No. 124,266

2 Claims. (Cl. 5ft-128) This is a division of application'Serial No. 668,506, tiled June 27, 1957, now Patent No. 3,036,356.

This invention relates in general to prestressed concrete constructions and more particularly to prestressed concrete slabs, and to a building construction possessing certain advantages in structure and the mode of erection by reason of the inclusion of my novel prestressed slabs therein.

In this comparatively young art of prestressed concrete, the production of prestressed concrete beams has risen to substantial magnitude and for certain purposes prestressed concrete slabs have been produced, particularly for road and bridge constructions where the matter of depth or head room is of minor importance. Such slabs have included in their structure integral beams of considerable depth in which the prestressed strands or tendons were embodied.

For use where load bearing capabilities were of minor importance, shallower prestressed slabs have been produced in which the tensioned reinforcing strands were disposed both longitudinally and transversely of the body of the slab. Such slabs, however, possess insuiiicient load bearing capabilities to permit their use in large sizes Without the employment of supporting beams carried by the building columns and also transverse stringers which afford support for, and prevent tlexure and eventual ruptur of, such slab under load. In the production of such a slab having longitudinal and transverse reinforcing strands, the strands are commonly` tensioned in the casting bed by the application of tensioning stress to the strands individually. This is a tedious and consequently expensive procedure, and involves greater time and labor than the production of deeper beams in which the reinforcing strands can be tensioned in groups.

One of the primary purposes of my present invention is the provision of a prestressed concrete slab which is devoid of deep prestressed supporting beams but on the contrary is relatively thin, affording a maximum of head room in building structures and which at the same time possesses suicient strength so as to be self-supporting and load supporting without undue ilexure and is capable of use to form the'iioors and ceilings of building structures without the necessity of employing structurally independent supporting beams or stringers.

Another object of my invention is to provide prestressedconcrete slabs of such size and proportions as to form the floors and ceilings of rectangular bays defined by angularly spaced columns to which my novel slabs are rigidly and securely attached so as to be supported thereby and aiford the sole load bearing connection between the columns of the bay.

.A further objectv of my invention is to provide a prestressed concrete slab of novel construction embodying peripherally and'diagonally disposed tensioned strands, together with anchor'plates disposed at the corners of the slab and to which all of said strands are anchored.

Other objects and advantages inherent in my invention will be readily appreciated as the same becomes better understood by reference to thel following description when considered in connection with the accompanying drawings.'

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Referring to the drawings, FIG. 1 is a plan view of one of my novel prestressed concrete slabs positioned in a bay area defined by rectangularly spaced columns by which such slab is supported.

FIG. 2 is a fragmentary sectional view on the line 2 2 of FIG. 1.

FIG. 3 is a similar view on the line 3 3 of FIG. 1.

FIG. 4 is a fragmentary sectional View on the line 4 4 of FIG. 1.

FIG. 5 is a fragmentary sectional view on the line 5 5 of FIG. 1.

FIG. 6 is a fragmentary plan view of a corner of my improved slab with a portion of the concrete removed to exhibit the anchor plate and reinforcing strand arrangement.

FIG. 7 is a sectional view on the line 7 7 of FIG. 6.

FIG. 8 is a sectional view on the line 8 8 of FIG. 6.

FIG. 9 is a somewhat schematic view showing the method of simultaneously tensioning the reinforcing strands by the application of tensioning forces directed diagonally of the slab.

FIG. 10 is a fragmentary view on an enlarged scale of one corner of the disclosure of FIG. 9.

FIG. 1l is a view similar to FIG. 1 illustrating a modiication of my invention.

' FIG. 12 is a fragmentary view taken on the line 12 12 of FIG. 1l.

FIG. 13 is an enlarged sectional view of one of the strand locking clamps.

Referring to the drawings more in detail, a prestressed concrete slab constructed in accordance with my invention is indicated generally by reference character 11. The slab, which :is of shallow thickness, is reinforced by any desired number of peripherally disposed strands 12, 13, 14 and 15 and by diagonally disposed strands 16 extending from corner to corner of the slab, and also by similar diagonally disposed strands 17 extending between the remaining corners of the slab.

All of the individual strands are preferably composed of :stress-relieved individual wires twisted together in cable form, such as is customarily employed in the production of pretensioned precast concrete units.

In accordance with my invention, these strands instead of being individually and consecutively tensioned in a tedious and time consuming operation are all anchored at their ends to corner anchor pla-tes indicated generally by reference character 18. From the enlarged showing of FIG. 6, which illustrates one of the typical plates, it will be observed that the plate comprises a fiat portion or base 19 provided with an upstanding anchor flange 21 reinforced by upstanding strengthening ribs 22 welded to the base and to the flange. The diagonal strands 16 are passed through the ange 21, as will be apparent from FIG. 8, and anchored to the plate by suitable end fittings 23 or other preferred commercial anchoring devices.

Each corner plate is also provided with upstanding anchor flanges 24 and 25 reinforced by strengthening ribs 26 and 27, respectively, and to which the peripheral strands 12 and 13 are respectively anchored by conventional end fittings or other suitable means of anchorage (FIGS. 6 and 10).

When the peripheral reinforcing strands or elements extending along the margins of the slab from corner anchor plate to corner anchor plate and the diagonal strands or elements extending diagonally of the slab from corner to corner have been anchored at their ends to the corner plates in the manner above described and as illustrated in FIGS. 9 and 10, all of said strands are then tensioned in a manner to be described.

Each anchor plate is attached at its outer end as shown in FIG. 10, to a yoke 28 in the form of a clevis by means A d of a pin 29 extending through the legs of the clevis and an aligned opening in the interposed plate. Each of said clevises, or in some instances all but one which may be stationarily anchored, are connected to a powerful ten-` The base of the bed will be shaped to produce a slab 1 bottomof the desired pattern or coniiguration. For purposes of economy in the use of slab material and of lightness in the finished product, the bed may be shaped to produce slabs shaped as exempliied in FIGS. 2 to 5, in-V clusive, of the drawings. Marginaily disposed grooves or channels adapted to accommodate peripheral strands such as 12 and lld of FIGS.' 2 and 3 result in the flat depending ribs33 and L394, respectively, and simliar ribs along the other two edges of the slab, while wider diagonally extending grooves or `troughs accommodating the diagonal f Strands 16 and 17 result in corresponding diagonal ribs 35 and 36, respectively. The intervening spaces between the marginal and diagonal ribs may be left open to present iiat downwardly facf i'ng surfaces or they may be ribbed in any preferred design, such, for instance, as the longitudinal ribs 37 of.V

FlGS. 2 and 5 or the transverse ribs 38 of FIGS. 3 and 4. In any event, the over-all thicknessof my ribbed rslabis very` materially 4less than that of the conventional deepbeamed slab of comparable load bearing strength. The attainable thinnessof my novel slab is importantly advantageous in the saving of head room in talll buildings, thereby in many instances enabling one or more additional iioors to be included in a building of fixed height.

The anchor plates having been positionedk at the corners of the casting bed and attached to the anchored tensioning apparatus and the strands having been arranged in the various marginal-and diagonal grooves in the bed base, the strands are then anchored to their respective anchor plates, as previously explained. Before'being finally anchored, however, each strand is drawn taut, whetherV it be of the straight type or of the draped or slightly sloped type, and anchored under a slight initial tension. Preferably this initial tension under which the strands are anchored to the corner plates should be substantially uniform. A

The jacks 31 or other preferred tensioning devices are now actuated in succession or simultaneously to draw the diagonally opposed anchor plates apart longitudinally of the diagonal strands, Vthereby tensioning the diagonal strands to whatever degree may have been determined as preferable for the particular slab to be produced.

rhe outward movement of the anchor plates diagonallyV of the bed tensions not only the diagonal strands but also simultaneously tensions the peripheral strands anchored to such` plates. The stress exerted upon the peripheral strands by the diagonal movement of the anchor plates in each Vinstance is equal to the cosine ofthe angle between the diagonal and peripheral strands at each corner. Thus, by applying to each of the corner plates a tensioning stress exerted diagonally of the slab, all of the diagonal and peripheral strands are simultaneously and speedily tensioned to the requisite degree. Furthermore, by tensioning the strands simultaneously in one operation, they will be subjected to a substantially uniform tension under'which they will be held in the conventional manner, permitting removal of the jacks for use elsewhere in the interim, until the slab has been pouredV and set.l

After the tensioning operation the casting forms, which in theV present instance are merelythe movable sidewalls 32 of the bed,` are placed in position around the perimeter of the .slab to be formed, whereupon the concrete' slurry i is poured in the usual manner. After sufficient curing to bond the concreteV to the strands, the stress is gradually relieved and sustained at the design load by the surrounding set concrete.

The clevises or yokes 28 are then removed from the anchor piates, whereupon the slab can be lifted ont of the form and transported to a storage area. Before being stored, however7 the exposed corner di) of each anchor plate is removed by cutting along the dotted line il shown in llG.y l0, the size and shape of the cut-out portion being such that theV plate will conform closely to thecolumn to which it will be subsequently attached. It will be observed from FGS. V6, 7, S, and l0 that each corner plate .is provided With an `upstanding wall l2 providing adam forV restricting the ow of poured concrete away from the corner of the anchor plate, thus leaving the kcorner outside the dam exposed, as will be apparent from FG. 10.

Since the conventional end fittings heretotoresuggested for use are quite expensive and when left in the slab materially increase the cost .of production, I have illustrated in FlGS. ll to i3 of the drawings a more economical procedure which enables such expensive iittings to be repeatedly reused instead of being permanently embedded in the slabs.

Cn FlG. l1 of the drawing the plate there shown is designated lby reference character 51 and the pins which correspond with the pins 29 previously described are designated by reference characters 52, 53, 54, and-55, respectively. The flanges 5e, 57, and Si?, which in the form of the invention previously described were designated as the anchor flanges, are in this instance of lighter construction and serve Vmerely as guide plates for the reinforcing strands which are passed through openings in the plates or` are disposed inslots extending downwardly. from the upper edges ot the plates and in which the strands are positioned.

The opstanding anges 59,'6L62, and 6.3, which in the form previously described were of light construction yand served merely as dams to hold the concrete away from the outer corners o the plates, are in this instance made of heavier material andserve as the-anchor plates.

' The strands in this formof the invention, instead of being held at each end by expensive end fittings, are anchored tothe flanges which also serve as the dams. Referring iirst to the peripheral strands 64, it will be observed that theyconstitute a pair consisting of a single strand klooped around the pin 52;' and secured by end fittings 65 to a block 66 abutting against the pin 531 at another side corner of the slab. When the pins 52 Vand 53 have been moved outwardly diagonally of the slab thereby formed, by jacks or other tensioning devicesfthe tensioned strands lare locked to the anchor anges 59 and 61 by gripping devices each consisting of a longitudinally split tapered block 68 provided with internal gripping teeth or shoulders 69. After the strands have been tensioned, these Vsplit gripping devices are orced'into the openings or slots 7l in the anchor plates, thereby gripping the strands and locking them under tension to the anchor plates.

Similarly, the strands 72 are wrapped, around the pin 52,1passed through the block k73 to which they are secured by the' end ttings 7d, Vand afterbeing'tensioned they are locked-tothe anchor plate 63 bythe locking devices 68.

The diagonal strands, Whichin the presenttinstance are 'four in number, are held uin the desired position by the guidetlanges 57; the inner strands 7S being looped around the pin fi'andanchored to the Vblock '76, while the outer strands 77 are wrappedaround the pinSZ andianchored tothe block 7S. i i

After the strands have been `tensionedfand locked by the clamping Vdevices in ,the manner described, and after the concrete has 4been poured, the strands are all severed with a torch or other cutting means outsideY the anchor flanges. In other Words, they .are cut between the points of Vanchorage and the clevis pins.A i

The expensivev end ttings are thereby released for use. in the production of the following slab, instead of being permanently embedded in the concrete so as to constitute a fixed cost item in each slab. The short pieces of strands resulting from the cutting may be discarded and, since they are of minor importance cost-wise as compared to the end fittings, a substantial saving is made by employing the form of anchorage disclosed in FIGS. 11- 13, inclusive, in lieu of the anchorage previously disclosed.

irrespective of the manner -of tensioning the strands employed, the pouring of the concrete and the subsequent steps are the same as previously described. After the slabs have been completed, and the concrete has become fully set and the slabs are required for use, they are removed from the storage area by suitable hoisting apparatus and transported to the location where they are to be used. Here they are lifted by suitable hoisting apparatus constructed and arranged to hoist each slab in a diagonal position in an open bay and lower it into and position it horizontally in the bay in which it will provide a permanent floor and ceiling.

Referring now to FIGS. 1, 6, 7, and 8, it will be ob served that the columns 43 defining the area of the bay have iixedly secured thereto, at spaced Vertical intervals corresponding to the floor levels, supporting brackets 44 which are permanently attached to the columns by welding or other reliable means of attachment. Each hoisted slab is lowered into position in the bay so as to fit between the columns defining its area with each anchor plate of the slab substantially contacting the adjacent faces of the columns to which the plate is then rigidly secured, preferably by welding 45 as indicated in FTGS. 7 and 8. The strengthening ribs 26 and 27 are also rigidly secured to the column, preferably by welding. Access to the edges of the plates and ribs to enable the welding to be performed is had through the space lying outside the darn 42 by which the flow of concrete 46 has been restricted, as previously explained. After the attachment of the corner anchor plates and ribs to the columns has been effected, the space between the columns and the dams 42 of the plates is filled with poured concrete, as indicated by 47 in FIGS. 7 and 8, thus providing a ilat top surface for the slab extending entirely to the columns.

While for erection purposes the columns may be temporarily 'or even permanently tied together by any suitable connecting means, it will be manifest that the slabs constructed and arranged and anchored in the manner described constitute the sole load bearing connections between the columns. The diagonal and peripheral pretensioned strands impart to the relatively thin slabs sutiicient stress resistance to enable al1 l-oad supporting beams and stringers t-o be dispensed with.

The economy in construction and erection attained by use `of my improved slab structure and the saving in time and material employed in the production `of my improved slab constitute in the aggregate a great saving in building cost. In addition, by reason of the thinness of my novel slabs and the absence of deep beams in the structure, a substantial saving in head room is attained in the building.

While I have shown and described that embodiment of my invention which at present seems preferable, it should be understood that various modiiications and details of structure and procedure may be resorted to within the scope of my invention as defined in the following claims.

I claim:

1. A rectangular prestressed concrete slab having an anchor plate mounted at each corner yof the slab, each anchor plate extending diagonally inward from its adioining corner of the slab and each plate having a notched exposed corner receiving a support for the corner of said slab, each anchor plate provided with a vertical anchoring flange disposed perpendicular to each adjacent edge of the slab and a centrally disposed anchoring flange perpendicular to the diagonal of the slab intersecting the plate, each flange having a plurality of horizontally arranged openings extending therethrough, a plurality of pretensioned reinforcing strands extending peripherally along the margin of the slab and other pretensioned strands extending diagonally of the slab between said plates, each `opening receiving an end of one of said strands, and means anchoring the ends of the strands to the anchoring flanges on said anchor plates and maintaining the requisite tension on said reinforcing strands to produce a precompression in the set concrete slab.

2. In a building construction having columns arranged in rectangular spaced relation, a rectangular prestressed concrete slab proportioned to be disposed within said columns, said slab having an anchor plate at each corner of the slab, means securing each of said plates to an adjacent column, each anchor plate extending diagonally inward from its adjoining corner of the slab and each plate having a notched exposed corner receiving a column at a corner of said slab, each anchor plate provided with a vertical anchoring flange disposed perpendicular to each adjacent edge of the slab and a centrally disposed ange perpendicular to the diagonal of the slab intersecting the plate, each flange having a plurality of horizontally arranged openings extending therethrough, a plurality of pretensioned reinforcing strands extending peripherally along the margin of the slab and other pretensioned strands extending diagonally of the slab between said plates, each opening receiving an end of one of said Strands, and means anchoring the ends of the strands to the anchoring flanges on said anchor plates and maintaining the requisite tension on said reinforcing strands t0 produce a precompression in the set concrete slab.

References Cited bythe Examiner UNITED STATES PATENTS 692,309 2/ 02 Knoche 50-148 1,444,806 2/23 ySoty 50 148 2,689,999 9/54 Petersen 50-128 2,964,143 12/ 60 Fayeton 50-80 2,995,799 8/ 61 Youtz 5 0-80 FOREIGN PATENTS 900,581 10/ 44 France.

1,119,999 4/56 France.

820,576 1'1/51 Germany. 680,907 10/52 Great Britain.

HENRY C. SUTHERLAND, Primary Examiner.

JACOB L. NACKENOFF, Examiner.

Claims (1)

1. A RECTANGULAR PRESTRESSED CONCRETE SLAB HAVING AN ANCHOR PLATE MOUNTED AT EACH CORNER OF THE SLAB, EACH ANCHOR PLATE EXTENDING DIAGONALLY INWARD FROM ITS ADJOINING CORNER OF THE SLAB AND EACH PLATE HAVING A NOTCHED EXPOSED CORNER RECEIVING A SUPPORT FOR THE CORNER OF SAID SLAB, EACH ANCHOR PLATE PROVIDED WITH A VERTICAL ANCHORING FLANGE DISPOSED PERPENDICULAR TO EACH ADJACENT EDGE OF THE SLAB AND CENTRALLY DISPOSED ANCHORING FLANGE PERPENDICULAR TO THE DIAGONAL OF THE SLAB INTERSECTING THE PLATE, EACH FLANGE HAVING A PLURALITY OF HORIZONTALLY ARRANGED OPENINGS EXTENDING THERETHROUGH, A PLURALITY OF PRETENSIONED REINFORCING STRANDS EXTENDING PERIPHERALLY ALONG THE MARGIN OF THE SLAB AND OTHER PRETENSIONED STRANDS EXTENDING DIAGONALLY OF THE SLAB BETWEEN SAID PLATES, EACH OPENING RECEIVING AN END OF ONE OF SAID STRANDS, AND MEANS ANCHORING THE ENDS OF THE STRANDS TO THE ANCHORING FLANGES ON SAID ANCHOR PLATES AND MAINTAINING THE REQUISITE TENSION ON SAID REINFORCING STRANDS TO PRODUCE A PRECOMPRESSION IN THE SET CONCRETE SLAB.

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