Method of Making Monolithic Concrete Structures

Abstract

A method of making a monolithic portion of a concrete building from a combination of pre-cast and cast-in-situ elements distributes moments and shear loads by using flanged pre-cast columns for support. In addition, a precast ‘waffle’ element is used to reduce the overall weight of the slab being formed. In preferred versions of this method support arms are provided that link formwork to an anchor cast into a pre-cast column and from the anchor to a load bearing point on a lower, pre-cured slab.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to concrete building units that may comprise both pre-cast and cast-in-situ portions to provide a continuous cementitious structure that distributes loads and moments so that less concrete is needed.

2. Background Information

In U.S. Pat. No. 7,121,061, the inventor teaches a method for making a monolithic reinforced concrete portion of a building by first erecting flanged wall members in a facing relationship, where at least one flange on each wall member preferably extends horizontally toward a facing wall member by about 10-25% of the intramural spacing. A slab extending across the intramural spacing is either cast in situ or formed by grouting a precast slab element into place. An advantage of this method is that when a complete room is defined by the wall elements, the method distributes moments and shear in two dimensions and thereby allows for the use of lighter, thinner structural elements. A disadvantage of this method is that its reliance on laterally extensive prefabricated wall members restricts its use to structures, such as apartment dwellings, that have relatively small openings in those wall modules, and precludes its use for structures, such as garages, warehouses and industrial buildings, that commonly provide relatively large open spaces by using spaced apart columns to support a ceiling or roof.

In DE 2,251,613, Schmidt teaches a method of fabricating a multi-storey cementitious structure in which spaced-apart columns support the above-grade levels. Schmidt's columns are pre-fabricated with flanges extending laterally by nearly one half of the inter-column spacing. A row of such columns is erected and the flanges on adjacent columns are grouted together to define a horizontal beam. Pre-fabricated concrete planks are then laid between two parallel beams and the planks are grouted together and to the beams so as to form a monolithic structure. A disadvantage of Schmidt's method is that the load imposed by the concrete planks is distributed one dimensionally, rather than in both lateral dimensions. This requires the beams and columns to be heavier and stronger than would be the case if the loads and moments were distributed in two dimensions.

In U.S. Pat. No. 1,516,074 Borg teaches a method of making a monolithic concrete structure in which a plurality of slabs is supported by another plurality of columns. Borg does not teach providing two dimensional support of horizontally extensive portions of his structure while the structure is being grouted together.

BRIEF SUMMARY OF THE INVENTION

One aspect of the invention is that it provides a method of making a monolithic reinforced concrete upper slab portion of a building supported by four or more precast columns. The columns are generally erected above a lower slab to define one or more generally rectangular bays having a respective column at each of its corners. Moreover, each of the precast columns has a reinforced rigid flange portion extending out horizontally at the selected height from the upper slab. Each flange portion, which is preferably square in a plan view, has rebar cast into it and extending outward from portions of all four of its edges. The columns are oriented so that each flange portion has two edges parallel to and facing respective edges of the flange portions of two other columns so as to define four rectangular border areas, each of which extends between a respective pair of the flange portions. A temporary support is placed in the middle of the bay defined by a set of four columns and a rectangular precast central slab preferably having rebar extending outward from all four edges is placed on it. The dimensions of the central slab are chosen so that the slab covers most of the bay and abuts, or slightly overlaps, all four border areas and the respective corner portions of all four associated columns. Formwork supported from the lower slab is placed beneath the border areas and concrete is poured to form the desired monolithic slab portion comprising the central slab and all four flange portions. This system distributes the loads and moments to all four sides, rather than only two sides, thus allowing for thinner slabs, which reduces weight, materials costs and labor.

In a preferred embodiment of the method, each of the precast columns comprises an anchor that is preferably a metal member cast into the column at a height about half way between the lower and upper slabs. When columns of this sort are provided, the formwork deployed beneath the border areas may be supported during casting by means of support arms connected to these anchors. In a preferred embodiment, each anchor is directly connected to two support arms, one of which extends from the anchor outward and upward to the formwork and the other of which extends from the anchor outward and downward to a load bearing point on the lower slab.

Another aspect of the invention is that it provides a method of using a relatively low weight slab member for making a monolithic reinforced concrete portion of a building comprising a monolithic slab supported by a plurality of columns. These columns are preferably erected at the four corners of one or more rectangular bays. The low weight slab or slabs are then placed atop the columns and are cemented thereto. The low weight slab members comprise a plurality of reinforced beam portions extending parallel to each of the edges of the slab member and an array of low-density regions disposed intermediate the beam portions. Rebar preferably extends along each reinforced beam portion and protrudes outwardly from each end thereof.

In a preferred embodiment, the slab member is formed by setting the rebar in position in a mold that defines the beam portions, placing blocks of polymeric foam in the regions between the rows of rebar and then casting the slab member. In particularly preferred cases, the weight is further reduced by providing that much of the precast slab member is thinner than the final slab. This minimizes the weight of precast pieces that need to be lifted and lowered into position and allows the builder to bring the entire slab up to a final specified thickness by pouring additional concrete on top of the pre-cast slab member.

In a particular preferred embodiment, the slab member comprises stepped or rabbeted edges in which an upper portion of the edge region extends all the way to the edge of the slab member and the lower portion of the edge region is stepped back therefrom. When used with a column having a complementary rabbeted flange in which a lower portion protrudes farther than an upper one, each corner of the slab can be placed in abutting contact with a respective flange prior to cementing the slab member to the column.

Although it is believed that the foregoing rather broad summary description may be of use to one who is skilled in the art and who wishes to learn how to practice the invention, it will be recognized that the foregoing recital is not intended to list all of the features and advantages. Those skilled in the art will appreciate that they may readily use both the underlying ideas and the specific embodiments disclosed in the following Detailed Description as a basis for designing other arrangements for carrying out the same purposes of the present invention and that such equivalent constructions are within the spirit and scope of the invention in its broadest form. Moreover, it may be noted that different embodiments of the invention may provide various combinations of the recited features and advantages of the invention, and that less than all of the recited features and advantages may be provided by some embodiments.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a schematic perspective view of an intermediate step in forming a slab.

FIG. 2 is a cross-sectional view of an upper portion of a flanged column, the section taken as indicated by the arrow 2-2 in FIG. 1.

FIG. 3 is a detail view, as indicated by the phantom circle 3 in FIG. 1, the view showing a corner of a column flange disposed beneath a corner of a central slab member.

FIG. 4 is a plan view of a preferred central slab.

FIG. 5 a is a cross section of a central slab having raised beam sections, the section taken as indicated by the arrow 5a,b-5a,b in FIG. 4.

FIG. 5 b is a cross section of a preferred central slab having some rebar held in place with stirrups, the section taken as indicated by the double-headed arrow 5a,b-5a,b in FIG. 4.

FIG. 6 a is another cross section of the slab of FIG. 5a, the section taken as indicated by the arrow 6a,b-6a,b in FIG. 4.

FIG. 6 b is another cross section of the preferred central slab, the section taken as indicated by the arrow 6a,b-6a,b in FIG. 4.

FIG. 7 is a sectional view showing temporary support arms used to support formwork used in casting a border area, the section taken as indicated by the arrow 7-7 in FIG. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

In studying this Detailed Description, the reader may be aided by noting the definitions of certain words and phrases used throughout this patent document. Wherever those definitions are provided, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to both preceding and following uses of such defined words and phrases. At the outset of this Description, one may note that the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or. The term “bay”, as used herein, stands for a rectangular horizontal division of a structure, and in particular stands for a region defined by a rectangular grid that may have a column at each corner thereof or that may have columns at two corners and a wall portion along one side. The term “rebar” is used herein to denote elongated reinforcing members of any sort and includes, but is not limited to, steel reinforcing bars.

Turning now to FIG. 1, one finds a schematic depiction of an intermediate step in a process of forming a slab 10 by joining a plurality of flange portions 12 of respective columns 14 with a central precast slab portion 16 and by casting border areas 18, which extend outward from the bay 20, in situ. Although the drawing depicts only a single bay 20, the reader will understand that the process herein described is applicable to a multi-bay arrangement. Moreover, although the depicted single bay has a column at each corner, the reader should recognize that flanged wall members, as described by the inventor in his U.S. Pat. No. 7,121,061 can be substituted for pairs of the depicted columns. The disclosure of U.S. Pat. No. 7,121,061 is fully incorporated herein by reference.

In a preferred configuration, such as that shown in FIG. 2, each column 14 comprises both a vertically extensive portion 22 and a flanged portion 12 that preferably comprises a stepped or rabbeted edge region 24 in which a lower portion 26 of the edge region extends further outward from the vertically extensive portion 22 than does an upper portion 28. This rabbeted edge arrangement is similar to that used on wall members described in the inventor's U.S. Pat. No. 7,121,061, and has the same preferred height ratios, set-back distances and protrusion lengths for rebar 29. The rabbeted arrangement aids in transferring shear loads from a supported portion of the slab to the rigid flange, and thence to the vertically extensive portion of all of the columns and to neighboring bays. In a particular preferred embodiment the lower portion of the rabbet extends ten to twenty centimeters outward beyond the upper portion of the rabbet. In order to provide a desirable overlap arrangement with a central slab member 16, rebar does not protrude from the corners 30 of the flange portions.

Although the columns 14 are depicted in the drawing as having a flat top surface, which accords with a process of making a single storey above grade, the reader should realize that many other arrangements are possible and that, more generally, the top of each column may comprise attachment means for mounting the base of another column used to support a yet higher storey in the structure.

The preferred central slab 16 has a complementary rabbeted edge region in which an upper portion of the edge region 32 extends further outward than does a lower portion 34. This allows each corner 35 of the slab member 16 to rest upon a respective corner of a column flange 12, as depicted in FIG. 3. As described above with respect to the flange portions, although the central slab member preferably has rebar extending outward from all its edges, there is no rebar extending outward from the corner portions that overlap with the flange portions.

Turning now to FIG. 4, one finds a plan view of a preferred central slab member, which is configured as a “waffle”. The preferred central slab member comprises a rim portion 36 having the rabbet edge features described above. In addition, the slab 16 comprises a grid of reinforced beam portions 38 running parallel to the edges of the slab 16. The upper portion of the beam portions 38 may have rebar cast into them, as depicted in FIGS. 5a and 6a. Preferably, the reinforced beam portions comprise rebar cast into lower portions of the beam and other rebar held on top of the beam portions by means of stirrups 39. The rebar retained in stirrups is preferably cast into the center section during a single concrete pour that tops off the waffle section and forms the border area portions of the slab. Rebar preferably protrudes through and outward from the ends of these beam portions as depicted in FIGS. 5a,b and 6a,b. The areas between the beam portions are preferably only about half the maximum thickness of the central slab member 16, and may be filled, at least partially, with foamed plastic blocks 40 or other lightweight items.

In a preferred process, the central slab 16 is pre-cast using foamed plastic blocks 40 having outwardly protruding ears or lugs 42. During this casting operation, the blocks 40 are held in position by the mold (not shown). Subsequently, when concrete is cast on top of the foam, as will be hereinafter described, the lugs 42 prevent the heavy concrete above the blocks from pushing the blocks out through the bottom of the precast slab 16. The reader will recognize that other means of locking the low density blocks into the concrete may also be employed and that these include, without limitation, providing a recessed region in the foam and inserting rebar through the foam and into adjacent areas prior to casting.

In a preferred process the columns 14 and wall members (not shown) are erected on a hardened bottom slab 44 or are supported above a bottom slab by being attached to another column or wall at a lower level in the structure—i.e., a column or wall associated with a building storey below the bottom slab. Free-standing temporary supports 46 are then placed in the central portion of each bay and respective central slab members are placed onto each one of them. As described above, in preferred arrangements, corners of the slabs are supported not only by the temporary support 46, but also by the corners of respective column flanges, as depicted in FIG. 3.

After the central slab members are in place, the preferred process calls for the erection of formwork 47 in the border areas. At this point additional rebar 29 may be introduced into the border areas and preferably fastened to rebar protruding from a slab or flange by clamping, welding, or by any other known means. In a preferred process the formwork in the border areas is supported by a combination of temporary trusses 48 and support arms 50. In this arrangement a first support arm 50 is fastened between a truss 48 and a respective anchor 52 in a column adjacent to the truss, as depicted in FIG. 7. Each such column may then be connected to a load bearing point 54 on the bottom slab 44. This arrangement has several advantages, not the least of which is that it provides more open space for movement of people and equipment on the bottom slab during the process of setting up for the concrete pour.

The preferred process allows for a single concrete pour to complete the slab by filling in the forms in the border areas and by also filling in those portions of the central slabs that have a reduced thickness.

Although the present invention has been described with respect to several preferred embodiments, many modifications and alterations can be made without departing from the invention. Accordingly, it is intended that all such modifications and alterations be considered as within the spirit and scope of the invention as defined in the attached claims.

Claims

1) A method of making a monolithic reinforced concrete portion of a building comprising an upper slab portion having a selected thickness extending between a top surface at a selected top height to a bottom surface at a selected bottom height, the slab portion connected to four columns defining a rectangular bay, the method comprising the steps of: a) providing the four precast reinforced columns respectively erected at respective corners of the rectangular bay, each of the columns comprising a respective vertically extensive portion and a respective horizontally extensive rectangular reinforced rigid flange portion having rebar protruding from each of its four edges, wherein each of the flange members has a top surface at the selected top height, the columns oriented so that each flange portion has two edges parallel to and facing respective edges of two other of the flange portions so as to define four border areas, each of which extends between a respective pair of the flange portions;b) placing a first temporary support within the rectangular bay so that a top of the support is substantially at the selected bottom height;c) placing a rectangular reinforced precast central slab member on the first support, the central slab member extending across the bay so as to abut all four of the flange members, the central slab member having a thickness over most of its area that is less than the thickness of the upper slab portion, the central slab member having rebar protruding outward from each of its edges;d) supporting respective forms beneath each of the border areas;e) pouring concrete over the forms and the central slab member to form the upper slab portion;f) waiting for the concrete to harden; andg) removing the supports.

2) The method of claim 1 wherein each of the flange portions comprises four rabbeted edge portions, each of which comprises a respective lower portion extending further away from the associated column portion than does a respective upper portion, wherein both the upper and lower portions have rebar extending outwardly therefrom.

3) The method of claim 1 wherein the central slab comprises four rabbeted edge portions, each of which comprises a respective upper portion extending to a respective edge of the central slab and a respective lower portion that does not extend to the respective edge, wherein both the upper and lower portions have rebar extending outwardly therefrom.

4) The method of claim 1 wherein: each of the flange portions comprises four rabbeted edge portions, each of which comprises a respective lower portion extending further away from the associated column portion than does a respective upper portion, and wherein both the upper and lower portions have rebar extending outwardly therefrom except in four flange corner regions;each of the central slab portions comprises four rabbeted edge portions, each of which comprises a respective upper portion extending to a respective edge of the central slab and a respective lower portion that does not extend to the respective edge, wherein both the upper and lower portions have rebar extending outwardly therefrom except in four central slab corner regions; andwherein the dimensions of the flange portions and central slab are selected so that when the central slab is placed on the first temporary support, each of the four central slab corner regions rests on top of a respective flange portion corner region.

5) The method of claim 1 comprising an additional step, carried out before the concrete is poured, of placing additional rebar in each of the border areas, the additional rebar running parallel to a nearest central slab edge.

6) The method of claim 1 wherein each of the columns comprises a respective anchor disposed in the vertically extensive portion thereof, and wherein the step of supporting a respective form plate beneath each of the border areas comprises connecting a respective first support arm between the respective form plate and the anchor disposed in a respective one of the pair of columns defining the respective border area; and connecting a respective second support arm between each of the respective anchors and a cured bottom slab.

7) The method of claim 1 wherein the central slab comprises two mutually perpendicular sets of rebar running between respective parallel edges thereof, the slab further comprising a plurality of low density elements.

8) A method of making a monolithic reinforced concrete portion of a building comprising an upper slab supported by a plurality of columns extending above a bottom slab, the method comprising the steps of: a) providing the plurality of precast reinforced columns comprising respective vertically extensive portions and respective horizontally extensive rigid flange portions disposed at a selected slab height, wherein each vertically extensive portion comprises a respective anchor for connecting a support arm to the column;b) erecting the columns to extend from a lower slab to at least the height of the upper slab;c) placing formwork extending between at least two of the columns and supporting the formwork by a combination of at least two first and at least two second support arms, wherein each of the first support arms connects a respective portion of the formwork to a respective anchor and wherein each second support arm connects the respective anchor to a respective load bearing point on the bottom slab;d) pouring concrete onto the formwork and allowing it to harden; ande) removing the support arms and the formwork.

9) The method of claim 8 wherein each anchor comprises a respective metal member cast into a respective column.

10) The method of claim 8 wherein each support arm is adjustable in length.

11) A method of making a monolithic reinforced concrete portion of a building comprising a slab supported by a plurality of columns comprising at least four columns erected at the four corners of a rectangular bay, the method comprising the steps of: a) providing a rectangular pre-cast slab member comprising a plurality of reinforced beam portions extending parallel to each of the edges of the slab member and an array of low-density regions disposed intermediate the beam portions, the slab member comprising rebar extending outward from each of the beam portions along each of the four edges of the slab member;b) supporting the slab member in abutting contact with each of the columns; andc) pouring concrete to join the slab member to the columns.

12) The method of claim 11 wherein the low density regions comprise polymeric foam blocks having protrusions extending outward from faces thereof.

13) The method of claim 11 wherein each of the columns comprises a laterally extensive flange portion having a rabbeted edge in which an upper portion of the flange portion is stepped back from the edge; wherein the slab member comprises a rabbeted edge in which a lower portion of the slab member is stepped back from the edge and wherein the step of supporting the slab member in abutting contract comprises placing each of four corner portions of the slab member on respective corner portions of each of the flange portions.

14) The method of claim 11 wherein selected portions of the slab member have a thickness equal to the thickness of the slab and other selected portions of the slab member have a thickness substantially equal to one half of the slab thickness.