U.S. patent application number 10/920991 was filed with the patent office on 2006-03-23 for reinforced concrete structure, rebar end anchor therefor and method of manufacturing.
This patent application is currently assigned to Dayton Superior Corporation of 7777 Washington Village Drive. Invention is credited to Clifford D. Bennett, Walter E. Schoffstall.
Application Number | 20060059841 10/920991 |
Document ID | / |
Family ID | 36072407 |
Filed Date | 2006-03-23 |
United States Patent
Application |
20060059841 |
Kind Code |
A1 |
Bennett; Clifford D. ; et
al. |
March 23, 2006 |
Reinforced concrete structure, rebar end anchor therefor and method
of manufacturing
Abstract
A method of forming anchors at the ends of rebars includes
providing an anchor plate, forming an opening through the anchor
plate that is larger than the diameter of the rebar, heating the
end of a rebar, inserting it into the anchor plate opening and then
forging it to upsize the rebar end into engagement with the wall of
the anchor plate opening. Preferably, the wall of the opening
through the anchor plate is irregular to enhance the interlock
between the upsized rebar end and the anchor plate. The resulting
rebar end anchor then finds particular utility in reinforced
concrete structure at joint intersections of for example, a beam
and column or wall.
Inventors: |
Bennett; Clifford D.; (Alta
Loma, CA) ; Schoffstall; Walter E.; (Pine Grove,
PA) |
Correspondence
Address: |
WOOD, HERRON & EVANS, LLP
2700 CAREW TOWER
441 VINE STREET
CINCINNATI
OH
45202
US
|
Assignee: |
Dayton Superior Corporation of 7777
Washington Village Drive
Dayton
OH
|
Family ID: |
36072407 |
Appl. No.: |
10/920991 |
Filed: |
August 18, 2004 |
Current U.S.
Class: |
52/649.1 |
Current CPC
Class: |
E04B 1/215 20130101;
E04C 5/161 20130101 |
Class at
Publication: |
052/649.1 |
International
Class: |
E04H 12/00 20060101
E04H012/00 |
Claims
1. A rebar end anchor comprising: an anchor plate, an opening
formed through said anchor plate, said opening having irregular
wall portions, a rebar having an anchor end and an outer surface
and deformations formed in said outer surface, said rebar anchor
end being received in said anchor plate opening and forged into
mechanical interlock with said irregular wall portions of said
opening.
2. The combination of claim 1 wherein said rebar is of
substantially constant diameter prior to being forged into
mechanical interlock with said irregular wall portions of said
opening through said anchor plate.
3. The combination of claim 2 wherein said rebar diameter is
smaller than said opening through said anchor plate.
4. The combination of claim 3 wherein said irregular wall portions
comprise circular grooves.
5. The combination of claim 4 wherein said grooves comprise
threads.
6. The combination of claim 3 wherein said irregular wall portions
comprise a counterbore formed in said opening in said anchor
plate.
7. The combination of claim 3 wherein said irregular wall portion
comprise alternating peaks and valleys projecting inwardly in said
opening.
8. The combination of claim 1 wherein said anchor plate is
substantially round.
9. The combination of claim 1 wherein said anchor plate is
polygonal.
10. The combination of claim 1 wherein said anchor plate is
rectangular.
11. A reinforced concrete structure comprising: a concrete body; a
concrete beam intersecting said body, a reinforcing bar imbedded in
said body and said beam and having an end terminating in said body,
an end anchor plate, an opening formed through said anchor plate,
said opening having irregular wall portions, and said end of said
reinforcing bar being received in said opening and forged into
mechanical interlock with said irregular wall portions of said
opening.
12. The structure of claim 11 wherein said reinforcing bar is
substantially constant in diameter prior to being forged into
mechanical interlock with said irregular wall portions of said
opening through said anchor plate.
13. The structure of claim 12 wherein said reinforcing bar diameter
is smaller than said opening through said anchor plate.
14. The structure of claim 13 wherein said irregular wall portions
comprise circular grooves.
15. The structure of claim 14 wherein said grooves comprise
threads.
16. The structure of claim 13 wherein said irregular wall portions
comprise a counterbore formed in said opening through said anchor
plate.
17. The structure of claim 13 wherein said irregular wall portions
comprise alternating peaks and valleys projecting into said opening
in said anchor plate.
18. The structure of claim 11 wherein said anchor plate is
substantially round.
19. The structure of claim 11 wherein said anchor plate is
polygonal.
20. The structure of claim 19 wherein said anchor plate is
substantially rectangular.
21. A method of manufacturing a rebar with end anchor comprising:
providing an anchor plate, forming an opening through said anchor
plate having irregular wall portions, providing a length of rebar
having an anchor end, heating said anchor end of said rebar,
inserting said heated anchor end of said rebar into said opening in
said anchor plate, and forging said heated anchor end of said rebar
into mechanical interlock with said irregular wall portions of said
opening in said anchor plate.
22. The method of claim 21 wherein said rebar is of substantially
constant diameter prior to being forged into mechanical interlock
with said irregular wall portions of said anchor plate.
23. The method of claim 22 wherein said substantially constantly
diameter of said rebar is smaller than said opening through said
anchor plate.
24. The method of claim 23 wherein said irregular wall portions
comprise circular grooves.
25. The method of claim 24 wherein said circular grooves comprise
threads.
26. The method of claim 23 wherein said irregular wall portions
comprise a counterbore formed in said opening through said anchor
plate.
27. The method of claim 23 wherein said irregular wall portions
comprise alternating peaks and valleys projecting into said opening
in said anchor plate.
28. The method of claim 21 wherein said anchor plate is
substantially round.
29. The method of claim 21 wherein said anchor plate is
substantially polygonal.
30. The method of claim 29 wherein said anchor plate is
substantially rectangular.
Description
FIELD OF THE INVENTION
Background of the Invention
[0001] Concrete is characterized by high compressive strength and
notoriously poor tensile strength. In a typical reinforced concrete
structure this deficiency in the tensile strength of the concrete
is obviated by imbedding in the concrete at those points where
tensile stress will be encountered, reinforcing bars, typically of
steel. Where a section of a reinforced concrete structure
terminates at another section, such as at a beam/wall or
beam/column intersection, provision must also be made to insure
that the ends of the rebars will not pull out of the wall or column
when tensile stress is encountered. Conventionally, this was
remedied by bending the end of the rebar and perhaps inserting
another rebar beneath the bend perpendicularly to the length of the
first rebar. Typically, a joint of this type is congested to begin
with and this remedy compounded the congestion, resulting in higher
concrete placement costs and possible concrete consolidation
problems.
[0002] To avoid these problems it is known to provide an enlarged
head at the rebar end, either through forging or by welding a plate
on the rebar end, or providing a plate with a threaded opening,
upsetting the end of the rebar to enlarge its diameter and then
threading the enlarged end complementarily to the anchor plate
threaded opening and screwing the plate onto the threaded rebar
end.
[0003] Where the rebar ends are provided with a forged head, a very
large forging press is required, a substantial portion of the rebar
must be preheated for forging with a commensurate expenditure of
time and energy, and multiple strikes of the press are required to
create the headed end. Where the end plate is a separate part with
a threaded opening receiving a threaded end of the rebar, the rebar
end must first be upsized through a forging process before the
threads are cut into the rebar end. This is necessary to achieve
the ultimate strength of the rebar. If the rebar were threaded
without upsizing the end, the thread would create a weak point that
would reduce the overall tensile strength of the rebar.
[0004] As noted above, it is also known to weld an anchor plate to
the end of a rebar, typically through an inertia welding process.
This approach has the drawbacks of requiring a separate fabricated
anchor plate and requiring the upsizing of the rebar end prior to
welding, but more importantly, the welding process is subject to
various process variables that contribute to quality
considerations.
[0005] It will be seen, therefore, that a need exists for a rebar
anchorage to reduce congestion at a joint intersection in a
reinforced concrete structure, but without the disadvantages noted
above with respect to conventional methods of providing an end
anchorage for concrete reinforcing bars.
SUMMARY OF THE INVENTION
[0006] The present invention provides a method of manufacturing an
end anchor of superior structural performance but with the
expenditure of less energy required than in comparable prior art
methods, resulting in cost savings and a unique end anchor
product.
[0007] Specifically, in accordance with the present invention a
separate anchor plate is provided, which may be round, square,
rectangular or other configuration and through the plate an opening
having irregular wall portions is formed. Conventional rebar having
an effective outer diameter smaller than the size of the opening
through the anchor plate is preheated at its end, the heated end
inserted into the opening through the plate and then forged onto
the plate by upsizing the rebar end and filling the hole through
the plate with rebar material to form a mechanical interlock with
the irregular wall portions of the opening through the anchor
plate.
[0008] This method permits the use of smaller forging presses than
would be required to forge the end of a rebar into an end anchor
and requires less heat prior to forging and less strikes of the
forging press to complete the assembly. Thus, an end anchor in
accordance with the present invention may be produced in less time
and with less energy than comparable processes for forming rebar
end anchors.
[0009] As a result, the construction of an intersecting joint, such
as the termination of a beam into a column or wall in a reinforced
concrete structure is greatly facilitated, while conserving the
energy and commensurate expense thereof usually associated with end
anchors of this type. Therefore, in a typical intersection of this
type, where reinforcing bars and associated ties create a congested
condition, the necessity of contributing to that congestion by
bending the end of the terminating rebar and providing cross rebar
members within the bend is avoided but again, without the expense
attended to conventional end anchors.
[0010] Additionally, the process of forging the rebar into the
anchor plate provides the added benefit of upsizing the rebar at
the connection. This provides a stronger section of rebar at the
connection and ensures that the rebar, if subjected to ultimate
tensile stress, will break at a location distant from the anchor
plate connection. This is an important feature because there are
standards that require failure to occur away from the connection.
This makes it obvious that the rebar has failed and not the anchor
plate-rebar connection.
[0011] These and other objects and advantages of the present
invention will become apparent from the following description, the
accompanying drawings and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and, together with a general description of the
invention given above, and the detailed description of the
embodiments given below, serve to explain the principles of the
invention.
[0013] FIG. 1 is a perspective view showing a typical beam-column
connection utilizing one embodiment of end anchors in accordance
with the present invention;
[0014] FIG. 2 is a perspective view of an end anchor plate in
accordance with the present invention illustrating an opening
through the plate having one form of irregularly shaped walls, in
this embodiment, taking the form of internal grooves;
[0015] FIG. 3 is an elevational view, partly in section, showing an
end of a conventional rebar about to be received in an opening
through the anchor plate of FIG. 2;
[0016] FIG. 4 is a view similar to FIG. 3, but illustrating the
rebar end after it has been preheated and forged into mechanical
interlock with the irregularly shaped walls of the opening through
the anchor plate of FIG. 3;
[0017] FIG. 5 is a view similar to FIG. 3, but showing a second
embodiment of the invention, wherein the irregularly shaped wall
portions of the opening through the anchor plate are formed as a
counterbore;
[0018] FIG. 6 illustrates the end of a rebar received in the
opening of the anchor plate shown in FIG. 5 after the rebar has
been preheated and forged into interlocking engagement with the
irregular walls of the anchor plate;
[0019] FIG. 7 is an end view of the anchor plate and forged in
place rebar of FIG. 4;
[0020] FIG. 8 is a view similar to FIG. 7 but illustrating another
embodiment of the present invention, wherein the anchor plate is
formed with a square configuration;
[0021] FIG. 9 is a view similar to FIG. 8, but wherein the anchor
plate is rectangular; and
[0022] FIG. 10 is a perspective view of another embodiment of
anchor plate showing another form of irregularity in the side walls
of the opening through the anchor plate designed to be mechanically
interlocked with the heated, forged end of a rebar.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] FIG. 1 of the drawings depicts a beam-column connection 10,
which comprises a column 12, a through beam, consisting of beam
segments 14 and 16 and a beam 18 terminating at the connection. As
will be apparent from in FIG. 1, the intersecting vertical
reinforcing bars, as at 20 and the horizontal intersecting bars, as
at 22 and their associated ties, as at 24, create a congestion
which, in conventional connections of this type is exacerbated by
the addition of the rebars projecting from the terminating beam,
particularly where the rebars of the terminating beam are bent at
substantially right angles and additional rebar inserted in the
bend to resist withdrawal. A disadvantage of this increased
congestion is poor concrete consolidation, higher concrete
placement costs and poor in place concrete quality. This condition
is ameliorated in accordance with the present invention by
providing rebar 26 with anchor ends comprising anchor plates, one
embodiment of which is shown at 30 and which are attached to the
rebar in a method in accordance with the present invention. While
the plates 30 shown in FIG. 1 are rectangular, it will be apparent
as the description proceeds that the plates may assume other
configurations, such as circular and square.
[0024] Thus, as seen in FIG. 2 of the drawings, an anchor plate 32
of round or circular configuration is shown having an opening 34
formed there through. As will be apparent from FIG. 2, the wall
portions of the opening 34 are irregular, that is, the wall portion
of the opening 34 is not merely a smooth constant diameter surface
extending through the anchor plate 32. Instead, the wall portions
of the opening 34 are, in the embodiment of FIG. 2, provided with
circular grooves 36. While the grooves 36 of FIG. 2 comprise a
threaded opening, as may also be seen in FIGS. 3 and 4, it will be
apparent the grooves 36 may also be simply a series of parallel
circular grooves.
[0025] In any case, it will be noted from FIG. 3 of the drawings
that the outer surface of rebar 37 is provided with deformations 38
which enhance its embedment in the concrete beam 18. While the
rebars 20, 22 and 26 are shown as smooth surfaced in FIG. 1 of the
drawings, in actuality all of the bars would preferably be provided
with deformations such as at 38 as shown in FIG. 3 of the drawings.
It will also be noted from FIG. 3 that the nominal outer diameter
of the rebar 37 is smaller than the opening 34 through the plate
32. This permits the anchor end 40 of the rebar to be inserted
freely into the opening 34.
[0026] However, prior to placing the anchor end 40 of the rebar 37
into the opening 34, end 40 is first heated and then, after it is
received in the opening, subjected to an axial force and thus
forged into place in mechanical interlocking relationship with the
irregular wall portions 36 of the anchor plate 32. In other words,
the heated end 40 of the rebar 37 is upsized by forging, filling in
the irregularities 36 in the opening 34 through the anchor plate 32
with material from the rebar to form a mechanical joint. As noted
above, upsizing the rebar ensures that should it encounter ultimate
tensile stress, it will break at a point remote from the joint with
the anchor plate,
[0027] While the end anchor construction shown in FIG. 4 of the
drawings is formed by forging the heated, anchor end 40 of the
rebar 26 into the grooves 36, it is possible to utilize other wall
irregularities as depicted in FIG. 5 of the drawings. Here, anchor
plate 42 is provided with a counterbored opening 44 having a first
portion 46 a second portion 48 and an interconnecting portion 50.
Otherwise, the process of manufacturing the rebar anchor end of
FIG. 5 proceeds similarly to that previous described. Thus, anchor
end 52 of rebar 54 is first heated and then, because the nominal
diameter of the rebar 54 is smaller than the first portion 46 of
the opening 44 through the plate 42, it is freely received in the
opening 44, after which the heated anchor end 52 is forged to
expand outwardly and fill the entire area of the counterbore
opening 44, including, not only the smaller diameter portion 46,
but also the counterbored portion 48 and the interconnecting
portion 50. Thus, again the heated anchor end of the rebar is
upsized to fill the opening 44 and form a mechanical joint between
the rebar and the anchor plate 42.
[0028] FIG. 10 of the drawings shows yet another embodiment of
anchor plate 60 having an opening 62 there through having irregular
wall portions 64. In the embodiment of FIG. 10 the irregular wall
portions 64 take the form of alternating peaks 66 and valleys 68
extending about the entire wall portion of the opening 62. While
not specifically shown, it will be apparent that a mechanical
interlock connection is made between the irregularly configured
wall portions 64 of the anchor plate 60 in the same manner as the
embodiments of FIGS. 4 and 6. That is, a rebar having a nominal
diameter smaller than the opening 62 is first heated and then
inserted into the opening 62 where it is forged, thereby upsizing
the heated end of the rebar and filling all of the spaces around
the alternating peaks 66 and valleys 68 to create a mechanical
interlock between the rebar and the anchor plate 60.
[0029] While in the embodiment of FIG. 4 of the drawings, the
anchor plate 32 is shown as round, the anchor plate may take
various other configurations, including a polygonal shape and more
specifically, a rectangular shape as shown at 35 in FIG. 9 of the
drawings or a square shape as shown at 33 in FIG. 8 of the
drawings. It will also be apparent that the anchor plates 42 and 60
may also assume round, palegamal, rectangular and square shapes,
similarly to the embodiment of FIG. 4 of the drawings.
[0030] Regardless of the specific configuration of the anchor plate
it will be apparent that the present invention provides a method of
fastening securely an anchor plate to an standard rebar by forming
an irregularly shaped wall portion defining an opening through the
anchor plate, heating an end of the rebar, inserting it into the
opening in the anchor plate and then forging the heated end of the
rebar to upsize it and fill the interstices provided by the
irregular wall portions of the opening through the anchor plate,
resulting in a secure mechanical interlock between the end of the
rebar and the anchor plate. Thus, the advantages of utilizing an
end anchor in place of merely bending the terminal portion of a
rebar and inserting a crossing rebar are obtained, but without the
expenditure of energy and expense associated with end anchors of
this type. While the methods and structures formed thereby
described herein constitute preferred embodiments of the invention
it is to be understood that the invention is not limited to these
precise forms of method and structure formed thereby and that
changes may be made therein without departing from the scope of the
invention as defined in the appended claims.
* * * * *