US2196158A - Concrete construction - Google Patents

Description

I April 1940- FQALLBRIGHT 2,196,158

CONCRETE CONSTRUCTION Filed Sept. 8, 193a 5 Sheets-Sheet 1 ,fzg veflfior \K [aw/1v F ALLB/E/GHT 6 WEM Y \S) d f/t'orweg A ril 2, 1940.

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E. F. ALLBRIGHT 2,196,158

CONCRETE CONSTRUCTION Filed Sept. 8, 1938 5 Sheets-Sheet 3 llrll'- Iwvewlbr [aw/N F flLLBE/GHT April 2, 1940- E. F. ALLBRIGHT 2,196,158

CONCRETE CONSTRUCTION Filed Sept. 8, 1938 5 Sheets-Sheet 4 191 view For [am/v F. ALLBK/GHT \i I y aw a/tfiommg April 2, 1940- I E. F. ALLBRIGHT 2,196,158

CONCRETE CONSTRUCTION Filed Sept. 8, 193a s Sheefs-Sheet 5 I77U677Z27i" [ow/1v E ALLBR/GHT Patented Apr. 2, 1940 UNITED STATES PATENT OFFICE CONCRETE CONSTRUCTION Edwin F. Allbright, Wollaston, Mass, assignor to Grid Flat Slab Corporation, Boston, Mass., a, corporation of Massachusetts Application September 8, 1938, Serial No. 228,937

'7 Claims.

This invention relates to improvements in concrete construction.

More particularlyit relates tothe centering of forms and laying of steel reinforcements for concrete floors, roofs, and the like, of the general type disclosed in my Letters Patent No. 1,307,031, dated June 17, 1919, wherein recesses are provided in the under face of .the concrete floor or other horizontal structure.

According to my said Letters Patent, a multiplicity of flanged sheet metal domes may be set next to each other with their respective flanges abutting, thus spacing the domes uniformly over the area where, the concrete is to be poured. The same dome-shaped forms may be utilized in the practice of my present invention, although the structural features of my novel reinforcement are not to be regarded as limited to the use of any particular device or devices for producing the recesses in the under face of the concrete.

Concrete construction of the sort to which the invention relates will have the under face deeply recessed at uniform intervals throughout its full area, except that a solid plinth may occur ateach location where a supporting column rises from below.

Between the recesses the walls of the recesses constitute intersecting ribs of corn crete; and the invention relates to improvements in the reinforcing of these relatively narrow ribs as well as to the reinforcing of the concrete structure as a whole.

Heretofore, the main reinforcing bars employed have been of great length-long enough to reach across the solid plinth of concrete over a column, and across the intervening region between that plinth and the next plinth, and across that next plinth also.

The parts of the bars ture in which all reinforcing bars may be straight. This eliminates the cost of bending them. Also, the main reinforcing bars may be considerably shorter than those considered requisite heretofore.

This eliminates the difliculties and expense of handling such extreme lengths. This feature is of substantial importance, for the span is often 24 feet between centers of plinths, and the plinths may be 10 feet wide, making a length of bar approaching 40 feet, which, in steel of inch diameter is awkward and extra expensive to transport and handle.

With the down-bending and the return upbending expense eliminated, another object is to provide for effective non-sagging suspension of the low bars at their ends.

These objects being attained, it also results from the invention that the reinforcing bars can be more easily placed than according to prior practices, and With less incidental expense.

A further object is to provide improved means for centering and for temporarily supporting the dome-shaped forms, and for improving the appearance of the recessed face of a concrete ceiling. 20

Still another object is to provide for varying the spacing of the dome-shaped forms as may be desired.

The stated'objects, and the other advantageous results which characterize the invention, are attained by emp oying a series of straight and stiff bars, herein called raising bars. In a preferred embodiment these rest on the tops of the dome forms, and are supported thereon a little above the plane of those tops, and one of them lies along each edge of each plinth. This makes a huge mesh or skeleton, usually rectangular, of raising bars, in which one series of bars extends in parallelism in one direction; and another series is of bars which extend in parallelism at right angles to the first; each bar crossing over a succession of tops of domes and crossing over valleys between thesuccessive domes in the series of domes on'which it rests.

Considering any row of domes which is in a 4 position bordering a side of a plinth, there will be valleys between the successivedomes of that row; and in each valley thus crossed by the raising bar resting on this row of domes, wire stirrups hang down into the valley from that bar and support the ends ofthe pairs of reinforcing rods which, deep down in the valley, extend from that plinth to its neighbor. That is in the case of valleys which extend only from plinth to plinth. Other valleys, not encountering any plinth, extend throughout the full dimension of the floor or roof. But the said stirrups support the ends of only those bars which extend from one plinth to another, and these rods in turn may support the rods extending through areas where they encounter no plinths. When the concrete has been poured, these rods make straight tensile reinforcements for the concrete close to the lower face of the rib, for each rib is the concrete filling of what was a valley between domes. Similar reinforcing rods, for the concrete at the upper face of the roof or floor, extend in two directions across above each plinth at this high level; and they have their ends supported on the said skeleton of raising bars in positions bordering the sides of the plinths.

This provision for utilizing wire stirrups for suspension of lower rods from higher bars, permits the building of an efiective net-work of reinforcing elements, in which, when incorporated in the poured concrete, pairs of straight bars may cross each other near the surfaces where stress is greatest, and provide a superior type of reinforcement. These stirrups are also essential in taking care of the shearing stresses in the ribs, when these stresses are too great to be carried by the concrete alone.

The dome-shaped forms may be centered and temporarily supported, as in my said Patent No. 1,307,031, by shoring whose individual boards may be spaced apart a distance approximating the outside width of a dome-form, from flange edge to flange edge, and which extend in parallelism in one direction only across the area of the floor or ceiling. The dome flanges may abut each other along these boards; or wide boards may be employed permitting spacing apart of the dome flanges as may be desired. In this latter case, according to the invention, structural plywood may be employed for overlapping slightly the edges of flanges, and for maintaining the domes until the concrete has been poured. When the temporary elements, including the plywood, are removed, the ribs of concrete between recesses are left with a surface aspect resembling panelling.

In the case where the dome flanges abut, temporary marking strips may be employed to leave impressions along joints for decorative effect.

It is intended that the patent shall cover, by suitable expression in the appended claims, whatever features of patentable novelty exist in the invention disclosed.

In the accompanying drawings, in which one illustrative embodiment of the invention, is shown:

Figure 1 is a top plan of a concrete construction for a floor embodying features of the invention, the concrete being absent from one area, to show in full lines the raising bars. reinforcing rods. stirrups and domes;

Figure 2 is a top plan, on a larger scale, showing upper reinforcing rods blackened and showing lower reinforcing rods cross-hatched, for clearness of portrayal of the overlapping and crossing reinforcing rods near the upper surface of cement over a plinth, and of the overlapping and crossing reinforcing rods near the lower surface of cement in the mid-region between four plinths;

Figure 3 is an elevation, enlarged still more, in section on 3-3 of Figure 2;

Figure 4 is a view similar to Figure 3, in section on 4--4 of Figure 2;

Figure 5 is a perspective of one of the stirrup units;

Figure 6 is a top plan of a structure, at a stage prior to pouring of the concrete, having my improved arrangement of shoring, the dome-shaped forms being absent from a portion of the area, for clearness;

Figure 7 is an elevation in section, as if on l'i of Figure 6; but showing Where the concrete will be located relative to the reinforcing rods;

Figure 8 is a view similar to Figure '7, in section as if on 88 of Figure 6;

Figure 9 is a fragmentary top plan of associated dome-shaped forms having small disks and triangular ribs for securing the forms, and for leaving decorating imprints on the under faces of the concrete ribs between recesses;

Figure 10 is an elevation, on an enlarged scale, in section on lf3-ll of Figure 9;

Figure 11 is a top plan of an arrangement in which the dome flanges are spaced apart;

Figure 12 is an elevation, on an enlarged scale, in section on l2l2 of Figure 11; and

Figure 13 is an elevation of fragments of adjoining domes, in section, showing reinforcing rods supported from below.

Referring to the drawings, the lightly dotted squares Hi of Figure 1 which is a top plan of floor, represent recesses in the under side of the concrete floor construction, and the portions l2 between squares ifi represent the concrete Walls of those recesses, being in the nature of crisscross depending ribs among the recesses, occupying the spaces marked 39 in Figures 3 and 4.

Figure 1 includes a full representation of two plinths and a partial representation of two others, each having the reference character 14. In the structure represented, the tensile stresses resulting from negative bending moments are greatest at the plinths, and the tensile stresses resulting from positive bending moments are greatest in the region midway between the four plinths.

According to the invention, reinforcing rods are arranged in pairs, with the pairs It crossing each other at each plinth, near the upper surface of concrete, and with the pairs 18 crossing each other at said mid-region between plinths, near the lower surface of each rib of concrete.

The enlarged plan, Figure 2, shows my improved structure prior to the pouring of concrete. The upper pairs of reinforcing rods l6 are blackened, and the lower pairs of reinforcing rods l8 are cross-hatched, in order to show clearly the crossing of pairs at the upper level. over a plinth, and the crossing of pairs at the lower level in the mid-region between plinths. Figure 2 illustrates also that the region intervening between any two plinths does not have the pairs of reinforcing rods crossing each other at either upper or lower levels, but has them extending in direction between the plinths at the lower level, and has them at the upper level extending at right angles to those at the lower level. Of course additional reinforcing rods may be used, but more are considered not necessary.

According to the invention, recessed dome forms 20 are first laid on a suitable temporary supporting structure 2] (Figure 3). Then a skelton raising bar structure is laid upon the domes, consisting of the parallel raising bars 22. which are each disposed medially above a row of domes 20 that lies next to one side of a plinth l4, and of the parallel raising bars 24 at a right angle with the bars 22, which are disposed like bars 22 on rows of domes lying along the other two sides of a plinth, crossing bars 22.

The bars 22, 24, which are primarily hanger supports, may be as long or as short as may be convenient and practicable in any particular case. Assuming a system of domed forms 20 to be in place, the bars may be rested on and spaced a little above the domes 20 (Figures 3, 4) by means of rough-surfaced briquettes 26 set on the domes at suitable intervals along the extent of a bar 22, 24. As portrayed in the drawings, a briquette 26 is set on every other dome 20, along the extent of each bar 22, 24. The bars rest directly on these briquettes, and/are spaced thereby from one to two inches or so above the domes, depending upon the thickness to which the concrete is to be poured over the tops of the domes, which ordinarily may range from two to four inches. Consequently, the length of the individual bars is quite unimportant.

After this skeleton support structure 22, 24 has been laid, stirrup units 28 are suspended from the bars 22, 24, one unit being placed to become embedded in each portion of a concrete rib 30, which ends at a margin of a plinth, one such stirrup being hung in the first section of every valley wherein a rib 36 will start away from a plinth.

As seen in Figure 5, each stirrup 28 may be a fabricated unit comprising a series of U'-shaped wires 28 secured together in spaced parallel relation and in alignment by the wire 28 welded to the bottom of each U, and by the wires 28 welded high up on the respective arms of the U, the end portions of the arms being bent into hooks to engage over the wires 23' and to extend obliquely downward as at 28 Two of these hook portions 28 preferably an opposed pair near the middle of the unit, are bent a little sidewise out of the plane of the remainder of their particular U element 28 thereby to constitute hooks, one at each side of the unit, for engaging also over one of the bars 22, or 24 which will hold the unit group of Us suspended until it becomes embedded within one of the concrete ribs 30.

The lower pairs of reinforcing rods l8 are positioned to be near the lower surfaces of the ribs 30, by being hung in these stirrup units 28 suspended from raising bars 22 or.24.

The upper reinforcing rods IB are positioned to be near the ultimate top surface of the concrete, and are shown resting upon the raising bars 22 or 24, depending upon the direction of their extent.

All of the reinforcing rods i6, 18 may be of the same length in a structure such as that here represented, which has square plinths I4 and which has the distance between plinths equal to the distance across a plinth. Actually the distance across a plinth. usually will be somewhat less than the distance between plinths. For example, assuming a distance of 24 feet from center to center of plinths, the width of each plinth ordinarily will be about four-tenths of that distance, which in the assumed case would be nine and six-tenths feet. And thus the distance between plinths would be fourteen and four-tenths feet. The reinforcing rods 16, I8 preferably will be a little longer than this distance between plinths, so that the rods i8 which extend between plinths, at the lower level, have their ends extending a little into the solid concrete of the plinths; and so that the rods I6 which extend across plinths and beside plinths, at the higher level, project across the rib next beyond the raising bar 22 or 24 on which they are resting.

After the reinforcing structure has been placed, and the concrete poured and set sufficiently, the

dome-shaped forms may be removed, leaving an under surface deeply recessed uniformly except at the regions of the solid plinths I4. As the forms are removed, the briquettes 26, on which the raising bars 22, 24 were originally laid, remain embedded in the concrete, held in by engagement of the concrete at the rough surfaces of the briquettes. The recessed construction thus produced effects a considerable saving of concrete by eliminating concrete which is not needed for strength, thereby assuring that the concrete which is used will Work-more nearly up to its maximum carrying capacity. Also the recessed construction relieves the concrete of the burden of carrying an excessive and unnecessary weight of concrete.

The recessed surface of concrete may be finished to produce a desired ceiling effect. In some cases the recesses may be preserved visible, while in other cases it may be preferred to cover the recessed surface to gain a plane effect.

Any practicable embodiment of the disclosed concrete reinforcing features, as herein disclosed, will include means for temporarily supporting and centering the dome-shaped forms 20, and one such as is represented generally at 2| in Figure 3.

Figures 6-8 illustrate an embodiment of the invcntion in which the dome forms 20 rest on, and are centered on, shoring which comprises the parallel boards spaced apart on centres at a distance equal to the outsidewidth of a dome form 20, and all extending in the same direction across the area of floor or ceiling which is to be constructed. These boards 32 may be themselves supported and maintained in any suitable manner, as by the joists 34, set edgewise, and extending across the direction in which the boards 32 extend (Figures 6, 8). The dome forms 20 rest directly on the boards 32 and are supported thereby along two sides only, and may be secured by a nail 36 or the like at each corner, the nail passing through the space at the juncture of the slightly rounded corners of dome flanges, with its head engaging and holding a corner flange of each of the four domes at the particular juncture.

The raising bars 22 and 24' of this embodiment serve the same function as the bars 22, 24 previously described. The reinforcing rods l8 cross each other in pairs in positions to be deep down in the ridges of concrete which border the recesses in a completed floor or ceiling, in regions between wall or beam supports; and the reinforcing rods l6 cross each at the higher level adjacent to the walls, and extend in one direction across beam supports. outside wall is represented at A and an inside wall at B; and a beam is represented at C in Figures 6 and 8. The raising bars 22' are shown resting directly on the dome forms 20, and the raising bars 24 are supported on the bars 22, being laid at 90 angles thereto. The stirrup units 23 are suspended from the raising bars 22 which are adjacent to the walls A and B, and from the raising bars 24 which are adjacent to the beam C. The pairs of reinforcing rods H! which extend in. directions between walls and between beams are supported near their ends in these stirrups.

Figures 9 and 10 illustrate means for making decorative impressions in the under faces of the ribs of concrete bordering the recesses. For this purpose a disk element Ml may be secured, as by a nail 42, over abutting corners of dome flanges, at each place where a plurality of such corners come together. Each disk has four In Figures 6 and 7, an

sockets therein for receiving the ends of bars 44, 'each'of which may be triangular in cross-section, and each extending along a line of edge abutment of dome flanges, from one disk 40 to another. The disks leave round impressions in the concrete and the bars 44 leave linear depressions in the concrete, when the domes and their appurtenances are removed.

Figures 11 and 12 show an arrangement of dome forms wherein the dome flanges may be spaced apart as desired. Plywood panelling 46 extends between the domes of forms 20 and slightly overlaps the spaced-apart flanges. The plywood panels are fitted to come nicely together, as seen in Figure 11, and disks 48 may be nailed at each juncture to hold the panels in place, and the panels hold the dome for. s properly placed during pouring and setting of the concrete. When the forms and plywood are removed, the concrete surfaces bordering recesses present a panelled effect.

Ordinarily the one-inch reinforcing rods IE, l8 can span the space between raising bars 22 or 24 without impracticable sagging. But additional raising bars may be employed if desired.

The lower reinforcing rods i8 may, if desired, be supported on wire chairs 50 which may stand on the flanges of domes, as indicated, in Figure 13. However, the supporting of these rods E8 in stirrups is preferred because both the rods and the stirrups are entirely enclosed and hidden when the concrete is poured.

I claim as my invention:

1. A structure for the forming and reinforcing of concrete floors and the like horizontal slabs recessed on their under sides, comprising, in combination, removable recess-forming domes spaced apart on temporary supports and aligned in two sets of parallel rows extending in directions which cross each other; raising bars, each extending along and supported by the domes of a row; high level reinforcing rods, approximately straight, crossing and supported by one parallel set of said raising bars; low level reinforcing rods, approximately straight, extending in valleys between rows of domes; and stirrups located in said valleys for supporting there the said low rods; the said stirrups of a valley being hung on raising bars by being hooked over those bars which extend in a direction crossing that direction in which that valley extends; said temporary supports and said domes being removable from the structure after the concrete has been poured and has at least partially set, leaving said bars and rods remaining as reinforcing elements in the concrete.

2. A structure for the forming and reinforcing of concrete floors and the like horizontal slabs recessed on their under sides, comprising, in combination, removable recess-forming domes spaced apart on temporary supports and aligned in two sets of parallel rows extending in directions which cross each other; raising bars, supported by the domes; spacing elements resting on the tops of domes across which the raising bars are laid for supporting said bars at an elevation above the tops of the domes; high level reinforcing rods, approximately straight, crossing above and supported by resting on said raising bars; low level reinforcing rods, approximately straight, extending in valleys between rows of domes; and means located in said valleys for supporting there the said low rods; said temporary supports and said domes being removable from the structure alter the concrete has been poured and has at least partially set leaving said bars and rods remaining as reinforcing elements in the concrete, and leaving said spacing elements permanently embedded in the concrete.

3. A structure for the forming and for reinforcing concrete floors and the like horizontal slabs as in claim 1 in which each stirrup comprises a plurality of U-shaped wires connected together in parallelism and having hooks for hanging the stirrup on a said raising bar; said U-wires extending down in a valley for supporting the reinforcing rods in the U.

4. A structure for the forming and reinforcing of concrete floors and the like horizontal slabs as in claim 2, wherein regions for the concrete plinths are devoid of the domes, and said raising bars extend along each side of each such plinth region, and wherein the reinforcing rods which extend between the regions for plinths are of length for their end portions to extend and be embedded in the concrete of the plinths.

5. A structure for forming and for reinforcing concrete floors and ceilings as in claim 2, wherein the dome forms are rectangular, and a base flange extends along each side of each for automatic spacing apart of domes by the abutting of flanges of adjoining dome forms; and wherein, at the corner junctures of adjoining flanges, a securing element engages a corner of each flange; and a recess-forming strip extends along each line of abutting juncture of flange edges, the strip being between and temporarily held by said securing elements.

6. A structure for the forming and reinforcing of concrete floors and the like horizontal slabs as in claim 2, wherein the dome-forms have base flanges which are spaced apart in the directions of said rows of domes, and in which stifi sheet material is temporarily secured in the valleys between domes, bridging the spaces between flanges, and securing the domes in their said alignment in rows.

7. A structure for the forming and reinforcing of concrete floors and the like horizontal slabs as in claim 2, wherein the dome-forms have base flanges which are spaced apart in the directions of said rows of domes, and in which sheets of structural plywood are temporarily secured in the valleys between domes, bridging the spaces between flanges, and securing the domes in their said alignment in rows.

EDWIN F. ALLBRIGHT.

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