US20090178356A1

US20090178356A1 - Pre-cast concrete column and method of fabrication

Info

Publication number: US20090178356A1
Application number: US12/008,929
Authority: US
Inventors: Hanns U. Baumann
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-01-15
Filing date: 2008-01-15
Publication date: 2009-07-16

Abstract

A column cage may comprise a plurality of column grids. The column grids may be formed with a plurality of longitudinal rebars. Also, the column grid may have a plurality of transverse rebars attached atop the plurality of longitudinal rebars. The transverse rebars may be attached to the longitudinal rebars. Four vertically extending rebars may be charged through the plurality of column grids at the four corners of column grids. The column grid may be held firmly to the vertically extending charged rebars with wire ties. Additionally, adjacent column cages may be connected to each other with a swedged on coupler.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. Pat. No. 5,305,573, filed on Jun. 3, 1992; U.S. Pat. No. 5,392,580, filed on May 6, 1992; and U.S. Pat. No. 5,459,973, filed on Apr.22, 1994, the entire contents of which are expressly incorporated herein by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND

The present invention relates to a concrete column, and a method for forming the same.
Prior art concrete columns are formed from a lattice work of rebars. In particular, vertically extending rebars are held in position by a plurality of equally spaced apart grids, as shown in FIG. 1. The grids are formed by bending short lengths of rebar and are held together by wire ties. For example, as shown in FIGS. 1 and 2, a square grid for holding in place twelve vertically extending rebars is shown. The grid is comprised of five different pieces of rebar. The first rebar is bent in a generally square shape having four rounded corners. The distal ends of the first rebar are bent inward toward the center of the grid. The other four rebars each have an L-shaped end and a J-shaped end laid upon the first rebar to form the grid. In particular, two of the four rebars are laid on top of the first rebar perpendicularly with respect to the other two of the four rebars which are laid below the first rebar. The five pieces of rebars are held together with a plurality of wire ties. A plurality of grids are formed. The twelve vertically extending rebars are then charged through the grids at the locations indicated in FIG. 1. The grids are held in place to the charged rebar with wire ties.
One deficiency of the prior art lattice work of grids and vertically extending rebars is that there are many crevices, voids and pockets between the five pieces of rebars that make up the grid, as shown in FIG. 2. These voids are typically very difficult to fill with concrete. Construction workers attempt to fill these pockets or voids by vibrating the wet concrete poured into a form surrounding the lattice work of grids and vertically extending rebars. Unfortunately, these voids may not be filled even with vibration thereby weakening the concrete column formed therefrom.
Another deficiency in the lattice work of grids and rebars is the enormous amount of weight of the material required to form the concrete column. In particular, the grid comprises rebars overlapping one another. The overlapping rebars add unnecessary weight to the concrete column. Moreover, the wire ties used to hold the rebars together add additional unnecessary weight to the concrete column. The additional weight due to overlapping rebars and the plurality of wire ties place an additional load on the concrete column such that the concrete column is able to withstand less stress from earthquakes and other forces.
Another source of voids and pockets within the concrete column is the protuberances (i.e., distal ends of first rebar and J-shaped ends of the other four rebars) of the rebar that are bent inward toward the center of the grid and the plurality of wire ties holding the rebars together. When wet concrete is poured in the form surrounding the lattice work of grids and vertically extending rebars, the concrete must work its way around and under each of the protuberances and wire ties. Unfortunately, due to the viscosity of the wet concrete, the concrete may not be able to work its way around each and every protuberance within the lattice work of grids and vertically extending rebar.
Another deficiency in the lattice work of grids and rebars is the inaccuracy of the placement of the five rebars that make up one grid and placement of the twelve vertically extending rebars within the plurality of vertically stacked grids. In particular, the five rebars are bent to form the structure shown in FIG. 1. Unfortunately, bending rebar is not accurate, and thus, the five rebars are not accurately placed in relation to each other. Moreover, the inaccuracy of the bent rebars is further accentuated because they are held together by wire ties since the lattice work of grids is inaccurate to begin with, the twelve vertically extending rebars are inaccurately placed within the lattice work of grids. The resulting concrete column formed from the column cage is not very rigid. Thus, the resulting concrete column is subject to breakage or failure upon the occurrence of an earthquake or other force.
Accordingly, there is a need in the art for an improved concrete column.

BRIEF SUMMARY

The column cage described herein and the concrete column formed by the column cage addresses the deficiencies identified above, discussed below and those that are known in the art.
The column cage may comprise a plurality of equally spaced apart column grids attached to vertically extending rebars. Each of the column grids may comprise a plurality of longitudinal rebars equally spaced apart from each other. A plurality of transverse rebars equally spaced apart from each other may be attached to the longitudinal rebars to form a plurality of orthogonal cells. By way of example and not limitation, to form one column grid, four longitudinal rebars may be equally spaced apart from each other. Four transverse rebars may have a length equal to about the longitudinal rebars. These four transverse rebars may be attached atop the longitudinal rebars. The transverse rebars may be attached (e.g., welding, etc.) to the longitudinal rebars at the point at which the transverse rebars contact the longitudinal rebars. Accordingly, such construction has an absence of protuberances which project inward toward the center of the column grid. The wet concrete is able to more easily flow through the column cage. As such, when wet concrete is poured into the form and through the column cage, the wet concrete fills the form surrounding the column cage such that the resulting concrete column has substantially no voids or pockets of air. Moreover, the column cage is not loosely held together by wire ties but is rigidly held together by welding and the like. Also, the resulting concrete column has substantially no voids or pockets of air. The resulting concrete column provides a more rigid and stronger concrete column compared to prior art concrete columns discussed in the background.
The column grid may have a generally square or rectangular configuration. The column grid may define four corners. The column cage may have less than twelve vertically extending rebars charged through the plurality of column grids. Preferably, the column cage has four vertically extending rebars charged through the plurality of column grids. Even though the column cage has less vertically extending rebars compared to the prior art, the concrete column formed by the column cage is more rigid compared to prior art concrete columns formed by the method discussed in the background. One benefit of having less vertically extending rebars charged through the column grids is that the wet concrete is able to more easily flow through the plurality or lattice work of column grids and vertically extending rebars to fill any voids or pockets of air that might be formed during the concrete pouring process.
The concrete column formed with the column cage discussed herein is more rigid compared to the prior art concrete column. As such, an individual column cage may be taller compared to prior art column cages. Accordingly, less interconnections between column cages are needed to reach a particular height. Moreover, less couplers are required to join the vertically extending rebars of adjacent column cages.
The construction of the column cages discussed herein produces a column cage which is generally lighter but stronger compared to prior art column cages discussed in the background.
In an aspect of the concrete column, adjacent column cages may be interconnected to each other with a swedged on coupler, a threaded coupler, or any other coupler known in the art or developed in the future.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which:

FIG. 1 illustrates a prior art column grid with twelve rebars charged therethrough;

FIG. 2 is a side view of the column grid shown in FIG. 1 illustrating spaces between the rebars used to fabricate the column grid;

FIG. 3 illustrates a concrete column formed with a column cage discussed in the detailed description and a second column cage interconnected to the concrete column with rebar couplers;

FIG. 4 is an enlarged perspective view of the column cage;

FIG. 5 illustrates a plurality of column grids stacked upon each other with rebar(s) being charged therethrough; and

FIG. 6 is an enlarged view of the rebars being interconnected to each other via a swedged on coupler.

DETAILED DESCRIPTION

Referring now to FIG. 3, column cages 10 a, b are shown. Each of the column cages 10 a, b may be fabricated in a manner so as to be longer than a standard prior art column cage. In particular, prior art column cages are typically fabricated in thirty feet length. In contrast, the column cages 10 a, b shown in the drawings may be fabricated in lengths 11 longer than thirty feet. Since rebar is typically provided in sixty feet length, the column cages 10 a, b may each be fabricated up to sixty feet long. However, in the event that rebar greater than sixty feet can be provided, the column cages 10 a, b may each be fabricated greater than sixty feet and up to the length of the rebar. Since the column cages 10 a, b may be fabricated in a length 11 longer than standard prior art column cages, fewer column cages 10 a, b are interconnected to each other to reach a required height. Accordingly, less rebar couplers 44, 50 are needed to couple column cages 10 a, b together and also greater heights may be reached in a shorter amount of time compared to the prior art. It has been found that concrete columns may be fabricated with 75% less labor compared to prior art concrete columns.
Moreover, less rebars are charged through the column grids 12 compared to prior art column cages. By way of example and not limitation, less than twelve rebars 22 are charged through the column grids 12. Preferably, only four rebars 22 are charged through the column grids 12. In contrast, prior art column cages for forming concrete columns having a substantially equal cross sectional area as that formed by the column cage 10 has more charged vertically extending rebars, specifically, twelve vertically extending rebars.
Referring now to FIG. 4, the column cages 10 a, b may each have four vertically extending rebars 22 charged through column grids 12 along the longitudinal vertical direction of the column cage 10 a, b. In prior art column cages used to form a concrete column of approximate equal cross sectional area as concrete column fabricated with the column cage described in the detailed description, twelve rebars are charged through the column cage along its longitudinal length as shown in FIG. 1 and discussed in the background. In contrast, only four vertically extending rebars are charged through the column cages 10 a, b described herein. Beneficially, only four sets of corresponding rebars in the column cages 10 a, b are coupled instead of the twelve corresponding rebars in prior art column cages. This results in time saving and a lighter concrete column.
The column cages 10 a, b may each comprise a plurality of column grids 12 equally spaced apart from and parallel to each other along the longitudinal axis of the column cages 10 a, b. Each of the column grids 12 may comprise a plurality of first or longitudinal wire members 14 disposed perpendicularly to a plurality of second or transverse wire members 16, or vice versa. The first wire members 14 may be spaced apart equally and disposed parallel from each other. Likewise the second wire members 16 may be equally spaced apart and parallel from each other. The first longitudinal wire members 14 may be placed atop the second wire members 16. The first wire members 14 may be attached (e.g., welded, adhered, tied, etc.) to the second wire members 16 at or about the points of contact between the first and second wire members 14, 16. Preferably, the first wire member 14 is welded to the second wire member 16 at the point of contact therebetween.
More particularly, the column grids 12 may each comprise four longitudinal wire members 14 and four transverse wire members 16. The longitudinal and transverse wire members 14, 16 generally define a square outer periphery. The longitudinal and transverse wire members 14, 16 may form a plurality of orthogonal cells (e.g., nine cells). The total area of the column grid 12 may be approximately equal to or slightly less than the cross sectional area of the column 18 to be fabricated from the column cages 10 a, b.
The longitudinal and transverse wire members 14, 16 may generally define a square or rectangular outer periphery. Each of the column grids 12 may have four corners. Wire ties 20 may be attached to each of the four corners. The wire ties 20 may be prepositioned and attached (e.g., welded, attached, etc.) to either the longitudinal wire member 14 or the transverse wire member 16. To assemble the column cage 10, rebar 22 is charged through the plurality of column grids 12 at each of the four corners. Preferably, one rebar 22 is charged in the plurality of column grids 12 at an interior side of each of the four corners. After the charging process, the column grids 12 may be expanded as shown in FIG. 4. The wire ties 20 are then firmly wrapped around each of the charged rebars to firmly hold or secure the charged rebar 22 in place.
Each of the prepositioned ties 20 may be firmly attached at one end thereof to either the longitudinal wire member 14 or the transverse wire member 16. Those skilled in the art will recognize the various means (e.g., welding, hot glue, etc.) that are suitable for attaching the ties 20 to the longitudinal or transverse wire members 14, 16. The other end of each tie 20 may be disposed proximate an intersecting transverse or longitudinal wire member 16, 14 such that after charging the rebars 22 through the column grids 12, the wire ties 20 may be easily tightened about the charged rebars 22.
The use of such ties 20 with a prefabricated column grid 12 permits the rebar to be positioned within about 1/16″ of its intended location. Such close tolerance positioning of the charged rebar 22 minimizes metal usage, improves structural strength, and reduces the amount of time in labor required to form the column cage 10. These consistently exact dimensions improve the reliability of the reinforced concrete structure and permit them to withstand violent earthquake forces.
Strength of the column cage 10 is improved since each of the rebars 22 is confined within a welded corner of the column grid 12. This increases the rigidity of the column cage 10 such that the column cage 10 does not tend to distort or corkscrew when erected. Accordingly, the resulting rigidity and high tolerance construction of the column cage 10 therefore substantially enhances and improves the erection process. In particular, the column cage 10 may be fabricated greater than thirty feet in length which is the typical length of prior art column cages 10. Accordingly, fewer column cages 10 are interconnected to each other for a given height compared to prior art column cages.
The column grids 12 may be stacked upon each other for storage and transportation as shown in FIG. 5. After the column grids 12 are stacked upon each other, they may be shrink wrapped to facilitate handling. Shrink wrapping the stacked column grids 12 helps to prevent movement of the grids 12 relative to one another during shipping and handling.
With particular reference to FIG. 5, the charging process of the rebar 22 is illustrated. During charging, a plurality of rebars 22 are pushed through the cells of the plurality of column grids 12 at the four corners thereof. Charging of the rebar 22 may be performed with the column grids 12 still stacked and shrink wrapped. By charging the shrink wrapped column grids 12, the individual column grids 12 may be maintained in a desired configuration which facilitates their handling, and thus, makes the charging process easier. This is accomplished by pushing the rebar 22 through the plastic shrink wrap. In particular, four rebars 22 may be charged through the stacked and shrink wrapped column grids 12. One rebar 22 may be disposed at each corner. Each of the rebars 22 may pass through the ties 20 disposed at the four corners of the column grids 12. After the rebars 22 are charged through the stacked and shrink wrapped column grids 12, the plastic shrink wrap may be removed from the stacked column grids 12. The stacked column grids 12 may then be expanded along the length of the rebars 22. Preferably, the column grids 12 are separated equidistant from each other and generally in parallel relationship with one another or generally perpendicular to the rebars 22. The ties 20 attached to the column grids 12 may then be tightened to the charged rebars to securely attach the individual column grids 12 to the charged rebars 22. This forms the column cage 10.
The rebars 22 may be charged through the plurality of column grids 12 via the method and device disclosed in U.S. Pat. No. 5,392,580, filed May 6, 1992, the entire content of which is expressly incorporated herein by reference. Generally, the stacked and shrink wrapped column grids 12 may be supported by elongate sections. The rebars 22 may then be charged through the stacked and shrink wrapped column grids 12. After the rebars 22 are charged through the column grids 12, the shrink wrap may be removed from the stacked column grids 12. The column grids may be separated from each other at equi-distant spaces. Thereafter, the wire ties 20 may be wrapped around the rebar 22 to securely hold the rebars 22 in place. The elongate rebar sections may be removed from the plurality of column grids 12.
In an aspect of the column cage 10 described herein, it is contemplated that the column cages 10 may be erected on site or pre-fabricate off site and transported (e.g., truck) to the site of use.
After forming column cage 10 as described above, the column cage 10 may be erected on the ground as shown in FIG. 3. Concrete forms are secured about the column cage 10 and wet concrete is then poured into the forms. The concrete forms are typically comprised of fiber glass or steel. As in prior art concrete column construction, the concrete substantially encapsulates the column cage 10. After pouring the concrete into the form, it is typically vibrated to minimize voids or air pockets formed therein during the pouring process. The column grids 12 enhance the pouring of concrete to eliminate voids or pockets of air because the extraneous protuberances are eliminated which would otherwise inhibit the flow of wet concrete through the plurality of column grids 12 and vertically extending rebars 22. Furthermore, the amount of wire ties is reduced because only four wire ties are required instead of twelve. Additionally, the rebars forming the column grids 12 are not overlapping thereby reducing the overall weight of the column cage 10.
Referring now to FIG. 3, a plurality of column cages 10 a, b may be interconnected to each other until a required height is achieved. In particular, a first column cage 10 a may be disposed vertically on the ground 38. A form may be secured about the column cage 10 a and concrete poured within the form. At this time, the upper distal end portion 40 of the column cage 10 a is not encapsulated with concrete. A second column cage 10 b may be vertically disposed on the upper distal end portion 40 of the first column cage 10 a. The first and second column cages 10 a, b may each have vertically extending rebars 22 which are aligned to each other. As such, a lower distal end portion 42 of the second column cage 10 b having four rebars 22 may be aligned to the upper distal end portions of the four rebars 22 of the first column cage 10 a.
A rebar coupler 44 may be used to attach the four rebars 22 of the first column cage 10 a to the four rebars 22 of the second column cage 10 b. Examples of various rebar couplers 44 that may be used to interconnect the vertically extending rebars of the column cages 10 a, b are disclosed in U.S. Pat. Nos. 5,305,573; 5,459,973; and 5,606,839, the entire contents of which are expressly incorporated herein by reference.
Alternatively, the rebar coupler 44 may be a swedged on coupler 50, as shown in FIG. 6. During assembly, the four vertically extending rebars 22 of the column cage 10 a extend upward. Concrete does not encapsulate the upper distal end portions 46 of the vertically extending rebars 22. The swedged on couplers 50 may have an elongate cylindrical configuration, as shown in FIG. 6. An inner diameter 50 of the coupler 50 may be sized and configured to the outer diameter 52 of the rebar 22 such that the swedged on coupler 50 may be pressed fit onto the upper distal end portion 46 (see FIG. 6) of the rebar 22. One swedged on coupler 50 may be pressed fit onto each of the upper distal end portions 46 of the rebars 22 of the first column cage 10 a (see FIG. 3). The second column cage 10 b may have a plurality of rebars 22. Lower distal end portions 48 (see FIG. 6) of the rebars 22 of the second column cage 10 b may be aligned to respective upper distal end portions 46 of the rebars of the first column cage 10 a. The swedged on couplers 50 may be press fit onto the lower distal end portions 48 of the rebars 22 of the second column cage 10 b.
Once the second column cage 10 b is attached to the first column cage 10 a via the rebar coupler 44 or a swedged on coupler 50, a form may be secured about the upper distal end portion 40 of the first column cage 10 a and at least the lower distal end portion 42 of the second column cage 10 b. Concrete is then poured into the form to encapsulate the upper distal end portion 40 of the first column cage 10 a and the lower distal end portion 42 of the second column cage 10 b. The poured concrete may now be vibrated to minimize voids or air pockets formed therein during the pouring process. The upper distal end portion 40 of the second column cage 10 b may not be encapsulated with concrete at this time. A third column cage may now be attached to the second column cage 10 b in the same manner that the second column cage 10 b is attached to the first column cage 10 a discussed above. A plurality of column cages 10 may be attached to each other in the aforementioned process until a desired height of column cages 10 is reached.
Since the column cage 10 may be fabricated so as to be longer than the typical thirty feet prior art column cage, less interconnections between column cages 10 are required. By way of example and not limitation, for a ninety feet concrete column 18, three prior art column cages, each having a length of thirty feet, are required to meet the ninety feet height requirement. In contrast, two column cages 10 a, b, each having a length of forty-five feet may be fabricated in the manner described herein and attached to each other to meet the ninety foot requirement. As such, only one splice between the column cages 10 a, b exist in the ninety foot column.
In an aspect of the column cages 10, each of the column cages 10 are more rigid compared to the prior art column cages. Accordingly, each of the column cages 10 may be fabricated to be longer than the typical thirty foot length of prior art column cages. More particularly, the column cage 10 fabricated in the method described herein may extend up to sixty feet in length or more so as to be limited by the length of available rebar in industry.
In an aspect of the column cages 10, it has been found that the labor required to assemble the column cages and stacked plurality of column cages upon each other was reduced by 75% compared to prior art column cages and stacking the same.
The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments.

Claims

1. A concrete column comprising:

a plurality of prefabricated grids disposed parallel to each other and spaced apart from each other, the prefabricated grids being vertically aligned to each other, each of the prefabricated grids having a rectangular configuration defining four corners;

four rebars charged through the prefabricated grids and respectively disposed adjacent the four corners of the prefabricated grids; and

concrete encapsulating the prefabricated grids and at least a portion of the four rebars.

2. The concrete column of claim 1 wherein each of the prefabricated grids have first, second, third and fourth rebars disposed parallel to each other and spaced apart from each other, and each of the prefabricated grids have fifth, sixth, seventh and eighth rebars disposed transverse to the first, second, third and fourth rebars, attached to the first, second, third and fourth rebars and spaced apart from each other.

3. The concrete column of claim 1 consisting essentially of:

a first rebar charged through the prefabricated grids adjacent an intersection of the first and fifth rebars;

a second rebar charged through the prefabricated grids adjacent an intersection of the fourth and eighth rebars;

a third rebar charged through the prefabricated grids adjacent an intersection of the first and fourth rebars; and

a fourth rebar charged through the prefabricated grids adjacent an intersection of the fifth and eighth rebars.

4. The concrete column of claim 1 wherein the plurality of prefabricated grids is expanded to a total length greater than thirty feet.

5. The concrete column of claim 4 wherein the plurality of prefabricated grids is expanded to a total length up to a length of the four rebars.

6. A concrete structure comprising:

a first concrete column comprising:

concrete encapsulating the prefabricated grids and at least a portion of the four rebars; and

a second concrete column comprising:

a plurality of prefabricated grids disposed parallel to each other and spaced apart from each other, the prefabricated grids being vertically aligned to each other, each of the prefabricated grids having a rectangular configuration defining four corners; and

four rebars charged through the prefabricated grids and respectively disposed adjacent the four corners of the prefabricated grids;

four couplers attached to corresponding rebars of the first and second concrete columns.

7. The concrete structure of claim 6 wherein the four couplers are swedged on couplers.

8. The concrete structure of claim 6 wherein less rebar couplers are used to interconnect the first and second concrete columns compared to prior art concrete columns of similar size fabricated by column grids comprising a plurality of rebars held together by wire ties.

9. The concrete structure of claim 7 wherein the swedged on couplers each have an inner diameter sized and configured to be press fit onto the rebars of the first and second concrete columns.