US3017723A - Lift-slab construction of buildings - Google Patents

Description

Jan. 23, 1962 E. J. VON HEIDENSTAM 3,017,723

LIFT-SLAB CONSTRUCTION OF BUILDINGS Filed March 17-, 1953 2 Sheets-Sheet 1 F I 6.1 s 5 6 F11; ib EL T 7 3 7 7 FIG.2 9 1 El m m m 2 Q m m 12 14 FIG-3 11 INVENTOR.

Agmm rnma' E. J. VON HEIDENSTAM LIFT-SLAB CONSTRUCTION OF BUILDINGS 2 Sheets-Sheet 2 Jan. 23, 1962 FIG.6 ,TT /V L I INVENTOR.

3,017,723 LIFT-SLAB CONSTRUQTION F BUILDINGS Erik Johan van Heidenstam, 58 Regeringsgatan, Stockholm, Sweden Filed Mar. 17, 1958, Ser. No. 722,051 12 Claims. (Cl. 50-140) This application is a continuation-in-part of application Serial No. 627,400 filed December 10, 1956, now abandoned in the names of Erik 1. von Heidenstam, Gosta Kelfce, and Fred Winter, for Method and Device for Erecting Buildings.

When erecting buildings it is well-known to cast several floor slabs one upon the other on the ground and, after the concrete has solidified, to lift them to their final level in a building and to fix them there on supports or columns.

This so-called lift-slab method, although used to some extent mainly in U.S.A., has certain drawbacks which have until now limited the technical application of said method.

The chief purpose of this invention is to remove such drawbacks and to reduce the weight of the lift-slabs while simultaneously rendering the slabs sufficiently strong. Thus, the equipment necessary for lifting the slabs will be less expensive and the economy of the method will be substantially improved.

Another purpose of this invention is to reduce the quantity of concrete necessary for casting the lift slabs, while simultaneously the strength of the slabs is not reduced, or even is raised, in comparison with the lift-slabs heretofore known.

Another purpose of this invention is to improve the relative strength and resistance of lift-slabs, that is the quotient of strength to weight.

Another purpose of this invention is to render it possible to use weaker or fewer jacks for the lifting procedure, and/or to attain greater safety or possibly a greater speed, in such procedure.

Another purpose of this invention is to shape such liftslabs in such manner as to carry higher loads than heretofore.

Another purpose of this invention is to render it possible to construct arched slabs (fioorings) and to attain other architectural effects, at moderate costs.

Another purpose of this invention is to pro-stress the lift-slabs by simple means, and to reduce the quantity of reinforcement irons without reducing the strength and resistivity of the slab.

Other purposes will be evident from the following specification.

Some preferred embodiments of the invention are shown in the annexed drawings.

FIG. 1 shows a number of slabs manufactured according to a previously known method and ready to be lifted.

3,,fil'ifl23 Patented Jan. 23, 1962 and horizontal slab, a second slab is cast upon it, and so forth, until all slabs are completed. Then the slabs are lifted in relation to columns 4 which pass through holes 5 in the slabs. The lifting is performed by means of lifting jacks 6 and lifting poles 7. The top slab is lifted first and provisionally fastened to the column at a suitable level. Thereafter the other slabs are successively lifted to such levels that the bottom slab after having reached its final level in the building can be permanently fixed to the columns. This operation is repeated until all slabs are placed and fastened in position.

FIG. 2 shows a floor slab 3 furnished with parallelepipedical depressions 8 so that a slab of uniform thickness and reduced weight is obtained, the upper uninterrupted (unbroken) part 9 of it being stiffened by an intersecting system of flanges or stiffeners 10.

In the embodiment of the invention shown in FIGS. 3 and 4 the dash-and-dot line 11 indicates the vertical cen tral line of a column of the structure. The bottom or ground mould 2 is not plane, but has around the column position a depression 2a which in this embodiment resembles a funnel-shaped cone. On this ground mould 2 a number of slabs is cast each of them consisting of a plane portion 12 integral with a conical or funnel-shaped portion 13. The plane portion 12 has the thickness t and the corresponding conical portion 13 has the thickness t measured vertically, where t =t Mould parts 14 shape recesses into which reinforcement irons projecting from the parts 12 and 13 are placed, to be bent out later on to be cast into other parts of a slab, these latter parts being cast in situ preferably as soon as the slab has been lifted to its final position in the building. This appears from FIG. 4 showing the reinforcement 15 in the plane part of the slab, while the loops 16 are bent out from their recesses in the conical part 13. Reinforcement 17 is also placed in the concrete cast 18. When pouring the concrete cast 18 the conical portion 13 of the slab acts as a mould part together with an additional mould 19 adjacent to column 4. The column 4 has lateral recesses 20 rendering supporting surfaces 21 for the concrete 18. In the upper part of the concrete cast 18 reinforcement is laid to be connected with the reinforcement 15 projecting from the plane part of the slab. As shown in dash lines in FIG. 4, the concrete for the cast 18 may be poured on up to level 2.2 and prestressed reinforcement wires 23 wound along the periphery of the concrete cast 18.

In performing the method according to FIGS. 3 and 4, a depression is formed in the ground, or other base upon which the structure is to be based, having a downwardly converging truncated conical shape. At the bottom of the depression a base surface is shaped for supporting a column 4, which surface will, of course, be

pressions in accordance with the prior art.

FIG. 3 shows a vertical section of a number of floor slabs in accordance with my invention.

FIG. 4 shows a vertical section of floor slabs (lift slabs) in accordance with my invention and placed in their position in the building.

FIG. 5 shows a vertical section of floor slabs in accordance with another embodiment of my invention.

FIG. 6 shows a vertical section displaying part of a conventional so-called mushroom column construction which, however, could not be used previously in connection with the lift-slab method.

FIG. 1 shows a ground area or building site 1, the surface of which forms a bottom or ground mould 2 for the 7 manufacture of the lowermost one of the concrete floor slabs 3. After the lowest floor has been cast as a plane given the same shape as the bottom of the column to be supported. The column is then placed in position on its base extending vertically. A circular angle iron 24 is then placed in the lower portion of the depression around the column, and reinforcing irons 15 laid in position. A layer of concrete is then poured into the depression with the angle iron serving as the inner mold.

The layer of concrete is made to extend outwardly beyond the depression with the desired thickness, and the layer of concrete in the depression is given the same dimension t in the vertical direction as the thickness, 2 of the outwardly extending slab portion 12.

At this time mold pieces 14 are located in the upper surface of the conical part of the mold for the purpose of forming recesses in the concrete into which reinforcing irons can later be placed in such position as to extend outwardly into the conical recess for engagement with further concrete to be poured later.

The preceding steps except for the provision of a recess in the ground and placement of column 4 are then repeated to form additional floor slabs 12 stacked or nested in the relationship illustrated in FIG. 3. The fioor slabs are then raised individually beginning with the top slab as has been customary until they are in the desired positions, respectively, opposite recesses in column 4 and forms 19 are applied beneath the central openings to close the gaps between the angle irons 24 and column 4. Reinforcing irons are then placed in recesses in the upper surface of the conical parts of the slabs extending into the conical recesses.

The locations of the respective slabs is preferably adjacent recesses 20 in column 4 so that the bottom edges 20 of the recesses form seats for supporting the slabs. The conical recesses in the slabs are then filled with concrete immersing the reinforcing irons 16, 17 forming a secure connection between the slabs and the column 4.

If desired the floor levels adjacent the columns may be made higher than the rest to provide for the application of tensioned bands 23 for prestressing the portions adjacent the columns.

The method according to FIGS. 3 and 4 thus renders the advantage that each of the slabs to be lifted-at a certain lifting power available-has a considerably increased bearing strength in relation to its own weight. The lifting can be performed with help of fastening devices fixed in the lower part of the conical slab part and consisting, for instance, of angle irons 24 which may be left in the finished building. As the slab parts immediately adjacent to the supporting areas (around the columns) are extremely resistant due to their curved shape, the maximum stresses on slabs 12 is considerably reduced. This obviously means a reduced floor thickness and a reduced reinforcement without weakening the flooring. Owing to the invention it is thus possible to make significant savings in material.

FIG. 5 shows a continuous, axially symmetrical, funnel-shaped depression of the ground mould 2 close to the columns, the inclination of said depression becoming increasingly steeper toward the horizontal plane. The: lower-most one of the slabs 3 is cast on the ground mould into such shape that its thickness t in the vertical direction is like the thickness t of the plane slab part independent of the angle of inclination. In those parts of the funnels 13 which are situated most closely to the central line 11, rigid moulds are fixed partly consisting of a number of mould discs 25 and partly-as intended for the top-most slab castof an upper mould 26. The mould parts 25 are threaded on to a post 28 which is fixed on a base plinth 27 and encased in a rotatable case 29 equipped with a disc and a handle 31. By means of this device it is possible to mould that part of the curved surface of the slab which is not covered by the upper mould 26, by turning the disc 30 around the post. 28.

The method of producing and erecting buildings as: illustrated in FIG. 5, resembles that described in connection with FIGS. 3 and 4 except that in place of the circular angle irons 24, circular mold parts 25 are threaded on the central column or post 28 and the shape of therecess formed in the base is funnel shaped, that is, its inclination becomes steeper closer to the center. In this case also the vertical thickness t toward the center is made equal to the vertical thickness farther removed from the column.

For providing this special shape a mold 26 is placed over the column 23.

The shape of the outer surface of mold 26 is such as to give to the concrete engaged by it the desired shape described above. For shaping the funnel shaped portions outwardly of mold 26, a scraper plate 30 is provided which is connected with a sleeve 29 on column 28. The bottom edge of plate 30 is made such that when the disc is turned around column 28 the plate shapes the surface in such a way that the thickness measured ver- .tically is the same at all positions.

till

t The importance of this methodas described in connection with FIG. 5becomes most evident when compared to the geometrical shape, see FIG. 6, heretofore generally used for the so-called mushroom columns.

The column 4 is there provided with a conically widening top piece 32 on which a thicker part 33 belonging to the floor slab 12 of same thickness, is formed. It is obvious that the discontinuity at the transition points between 4, 32, 33 and 12 render concentrated tensions and stresses both due to the bending moments between slabs and columns and due to the shearing stresses; this is extremely unfavourable for the strength. A column capital as shown in FIG. 6 can thus not be considered as a technically perfect solution. The reason why said construction is normally still in use is to be seen in the fact that by conventional means a formation of curved areas as shown in FIG. 6 to be performed by casting in situ is too expensive.

The columns can also have the shape of wall elements.

What I claim is:

l. The method of constructing buildings having a plurality of concrete floors secured to vertical columns passing through holes in said fioorings, comprising, forming a mold having downwardly tapering depressions at those positions where the columns are to be erected, forming in said mold a concrete floor slab having downwardly tapering depressions therein and having uniform thickness measured vertically, and having a hole extending therethrough at the bottoms of said depressions, repeating said casting procedure using the first slab as a bottom mold, again repeating said slab-forming procedure until a stack of floor slabs is formed, erecting columns passing through said holes in said floors, raising said slabs successively to their final levels, by force exerted between said slabs and said columns, and casting concrete in said depressions in said slabs in contact with said columns thereby securing .said slabs to said columns.

2. The method of constructing multi-storied buildings and similar structures having a plurality of concrete floors secured to columns passing through holes in the floors, comprising, preparing a bottom mold having downwardly sunk funnel-like depressions therein, placing mold disks in the center of said depressions, forming in said mold a concrete floor slab having uniform thickness measured vertically including the part thereof in the depressions, said mold disks forming holes through the concrete at the center of said depressions, causing said concrete to solidify to a slab, repeating said slab-forming steps each time using the next preceding, underlying slab as a bottom mold for the next slab cast in the stack, erecting columns extending through the holes in the slabs, lifting said slabs by means of jacks acting upon said columns without substantially tilting them from their horizontal position, until they successively reach their final levels, and casting concrete into the funnel-like depressions and between the slab and the columns to secure said floor slabs to said columns at their desired respective levels.

3. The method of constructing multi-storied buildings and similar structures having a plurality of concrete floors secured to columns passing through holes in the floors, comprising, preparing a bottom mold having downwardly sunk funnel-like depressions therein, placing hole-forming members in the centers of said funnelshaped depressions, forming in said mold a concrete floor rslab having the same thickness measured vertically throughout and having through-extending holes made by said mold-forming members, leaving the concrete to solidify, then casting the next overlying slab by repeating the casting steps and using the underlying solidified slab as a bottom mold, repeating the casting steps to create a stack of slabs, forming columns with reduced portions at the levels of the floors of the building, placing said columns in the holes through the slabs, lifting said slabs by force exerted between said columns and said slabs without substantial tilting of their final levels, and casting concrete into said depressions and into the reduced portions of said columns to form a mushroom monolithic construction with the columns around their reduced portions.

4. The method of constructing multi-storied buildings and similar structures having a plurality of concrete floors secured to columns passing through holes in the floors, comprising, forming a stack of substantially identical concrete floors provided with funnel-shaped projections extending downwardly from points located interiorly of the peripheries of said floors and of the same thickness measured vertically including the portions forming funnel-shaped projections, forming holes through the floors in the centers of the funnel-shaped projections, erecting columns extending through said holes in the floors, lifting the floors successively to their final levels, and casting concrete into said funnel-shaped projections and around the columns thereby securing said floors to said columns.

5. The method of constructing multi-storied buildings and similar structures having a plurality of concrete floors secured to columns passing through holes in the floors, comprising forming a plane bottom mold having funnel-shaped depressions extending downwardly from its main plane surface and located at distances from the outer edges of said bottom mold, forming into said bottom mold, a concrete slab having the same thickness measured vertically both in the plane portion and in the depressions, while making through-extending holes in the bottoms of said depressions, allowing the concrete to solidify, repeating the casting, hole-making and solidifying-steps, while using the then next underlying fioor slab as a bottom mold, erecting columns in said holes when the stack of concrete floors has solidified, lifting the floors successively to their final levels, by force exerted between said columns and slabs, and securing the floors to the columns by casting concrete in said funnel-shaped depressions, forming mushroom-shaped monolithic connections between the floors and their carrying columns.

6. A building structure comprising a plurality of horizontal parallel, spaced concrete floors, having plane portions and funnel-shaped projections extending downwardly from the floors at points inside their peripheries and formed of concrete integrally with the plane portion of said floors, columns extending through said floors at the centers of said projections, and concrete cast into the funnel-shaped cavities of said projections and around said columns uniting them permanently to a stiff mushroomshaned bond between floors and columns 7. A multi-storied building frame, comprising a plurality of horizontal, parallel, spaced concrete floors having substantially plane portions of uniform vertical thickness, and having depressed funnel-shaped portions extending downwardly from the plane floors and well inside their periphery, said funnel-shaped portions being formed of concrete integrally with the floors, columns extending through said floors at the centers of the funnel-shaped portions, and bodies of concrete cast into the cavities inside said portions and around said columns uniting the columns permanently with the floors.

8. A multi-storied building frame, comprising, a plunali-ty of horizontal parallel, spaced concrete floors, having substantially plane portions having uniform vertical thickness, and having depressed funnel-shaped portions extending downwardly from the said plane and portions thereof and located well inside their peripheries, and funnel-shaped portions being formed of concrete integrally with the plane portions of said floors and having the same vertical thickness as the respective floors, columns extending through said floors at the centers of the funnel-shaped portions, and bodies of concrete formed in the cavities inside said funnel-shaped portions and around said columns uniting the columns permanently with the floors.

9. The method according to claim 1, and in which said slab is formed with another portion extending horizontally outward from the depressions.

10. The method according to claim 1, and forming the funnel-shaped slab curved inwardly downwardly.

11. The method according to claim 1, and inserting depression-forming molds in the upper surface of the funnel-shaped slab to provide recesses, inserting reinforc ing irons in said recesses extending outwardly thereof into the space within said funnel-shaped portion and filling said recesses and said funnel-shaped space with concrete around the columns emersing the reinforcing irons.

12. The method of constructing buildings and similar structures having a plurality of concrete floors, comprising, casting on a lower level a number of stacked floor slabs having downwardly directed funnel-shaped depressions with holes for the passage of columns, and with the same vertical thickness of concrete all over, erecting vertical columns passing freely through the holes in the slabs, then lifting said slabs by means of lifting jacks and casting concrete into said depressions and around said columns to permanently fix said slabs to said columns at the proper levels to form the building frame.

References Cited in the file of this patent UNITED STATES PATENTS 1,045,774 Conzelman Nov. 26, 1912 1,066,436 Peltzer July 1, 1913 1,444,806 Soty Feb. 13, 1923 2,006,070 DiStasio June 25, 1935 2,296,863 Miller et al Sept. 29, 1942 2,483,175 Billner Sept. 27, 1949 2,531,576 McClellan et al Nov. 28, 1950 2,871,544 Youtz Feb. 3, 1959 FOREIGN PATENTS 1,109,975 France Oct. 5, 1955 1,133,932 France Nov. 26, 1956

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