U.S. patent application number 12/012957 was filed with the patent office on 2009-08-06 for concrete form duct chair and method.
Invention is credited to James E. Fabinski.
Application Number | 20090193731 12/012957 |
Document ID | / |
Family ID | 40930280 |
Filed Date | 2009-08-06 |
United States Patent
Application |
20090193731 |
Kind Code |
A1 |
Fabinski; James E. |
August 6, 2009 |
Concrete form duct chair and method
Abstract
An improved concrete form duct chair and method of forming
concrete structures. The concrete form duct chair has a generally
flat polymer or steel body with several pre-stressing strand duct
sized apertures passing through the body, as well as four or more
alignment legs projecting from the body, the alignment legs and
body dimensioned and configured to extend for a total width
approximately equal to such cross sectional width of such concrete
form and thus hold the concrete form duct chair in position against
the walls of the form. Concrete access apertures passing through
the body allow concrete to pass therethrough during pouring
operations. A method embodiment of the invention teaches pouring of
concrete structures with pre-stressing ducts passing therethrough
using the device of the invention to retain the pre-stressing ducts
in alignment within the concrete form.
Inventors: |
Fabinski; James E.; (Denver,
CO) |
Correspondence
Address: |
BARBER LEGAL
P.O. BOX 16220
GOLDEN
CO
80402-6004
US
|
Family ID: |
40930280 |
Appl. No.: |
12/012957 |
Filed: |
February 6, 2008 |
Current U.S.
Class: |
52/223.13 ;
249/207; 52/677; 52/745.19 |
Current CPC
Class: |
E04G 21/1841
20130101 |
Class at
Publication: |
52/223.13 ;
52/677; 249/207; 52/745.19 |
International
Class: |
E04C 5/10 20060101
E04C005/10; E04C 5/16 20060101 E04C005/16; E04G 17/00 20060101
E04G017/00; E04G 21/02 20060101 E04G021/02 |
Claims
1. A concrete form duct chair of a concrete form having both a
first cross sectional width and a first pre-stressing strand duct,
the first pre-stressing strand duct having a first pre-stressing
strand duct diameter, the concrete form duct chair comprising: a
generally flat body; a first duct aperture passing through the
body, the aperture having a first duct aperture diameter
approximately equal to such first pre-stressing strand duct
diameter; first and second alignment legs projecting from the body,
the alignment legs and body dimensioned and configured to extend
for a total width approximately equal to such cross sectional width
of such concrete form; and a first concrete access aperture passing
through the body, the concrete access aperture dimensioned and
configured to allow semi-liquid concrete to pass therethrough.
2. The concrete form duct chair of claim 1, wherein the material of
duct chair comprises one member selected from the group consisting
of: polymer, metal, wood, and composites thereof.
3. The concrete form duct chair of claim 1, further comprising:
third and fourth alignment legs projecting from the body, the third
and fourth alignment legs and body dimensioned and configured to
extend for a total width approximately equal to such cross
sectional width of such concrete form.
4. The concrete form duct chair of claim 1, further comprising: a
second duct aperture passing through the body, the aperture having
a second duct aperture diameter approximately equal to such first
pre-stressing strand duct diameter.
5. The concrete form duct chair of claim 1, further comprising: a
second concrete access aperture passing through the body, the
second concrete access aperture dimensioned and configured to allow
semi-liquid concrete to pass therethrough.
6. A method of casting concrete structures comprising the steps of:
a) erecting a first concrete form side having an internal cross
sectional width to make a concrete form; b) providing at least one
duct chair having a generally flat body and a first duct aperture
passing through the body, the aperture having a first duct aperture
diameter approximately equal to such first pre-stressing strand
duct diameter, the generally flat body further having at least
first and second alignment legs projecting from the body, the
alignment legs and body dimensioned and configured to extend for a
total width approximately equal to such cross sectional width of
such concrete form, the body further having a first concrete access
aperture passing through the body, the concrete access aperture
dimensioned and configured to allow semi-liquid concrete to pass
therethrough; c) securing the at least one duct chair and a duct
passing through the duct aperture into the concrete form; and d)
casting concrete into the concrete form.
7. The method of casting concrete structures of claim 6, further
comprising: e) placing a first mat of reinforcing steel members
into the concrete form prior to securing the duct chair and duct
into the concrete form.
8. The method of casting concrete structures of claim 6, further
comprising: f) placing the duct through the duct chair aperture
prior to securing the duct chair and duct into the concrete
form.
9. The method of casting concrete structures of claim 6, further
comprising: g) placing the duct through the duct chair aperture
after securing the duct chair into the concrete form.
10. The method of casting concrete structures of claim 6, further
comprising: h) securing the duct chair in place using
fasteners.
11. The method of casting concrete structures of claim 10, wherein
the fasteners further comprise one member selected from the group
consisting of: wires, flexible fasteners of plastic/polymer,
string, twine, rope, cable, screws, nails, brads, tacks, bolts,
snap fasteners, hook-and-loop fabric, sleeves, and combinations
thereof.
12. The method of casting concrete structures of claim 6, further
comprising: i) placing a second mat of reinforcing steel members
into the concrete form after securing the duct chair and duct into
the concrete form.
13. The method of casting concrete structures of claim 6, further
comprising: j) erecting a second concrete form side defining the
internal cross sectional width between the first and second
concrete form sides.
14. The method of casting concrete structures of claim 6, further
comprising: k) providing a first layer of steel plating in the
form.
15. The method of casting concrete structures of claim 6, further
comprising: l) allowing the concrete to cure after pouring.
16. The method of casting concrete structures of claim 6, further
comprising: m) stressing the concrete casting after pouring.
17. The method of casting concrete structures of claim 16, further
comprising: n) stressing the concrete casting immediately after
pouring.
18. The method of casting concrete structures of claim 16, further
comprising: o) stressing the concrete casting at a first time
duration after pouring.
19. The method of casting concrete structures of claim 6, further
comprising: p) separating the concrete casting from the form.
Description
COPYRIGHT NOTICE
[0001] A portion of the disclosure of this patent document contains
material which is subject to copyright protection. The copyright
owner has no objection to the facsimile reproduction by anyone of
the patent document or the patent disclosure, as it appears in the
Patent and Trademark Office patent file or records, but otherwise
reserves all copyright rights whatsoever. 37 CFR 1.71(d).
CROSS-REFERENCE TO RELATED APPLICATIONS
[0002] N/A
FIELD OF THE INVENTION
[0003] This invention relates generally to concrete form devices,
and specifically to duct chair devices for preformed or prestressed
concrete structures.
STATEMENT REGARDING FEDERALLY FUNDED RESEARCH
[0004] This invention was not made under contract with an agency of
the US Government, nor by any agency of the US Government.
BACKGROUND OF THE INVENTION
[0005] Casting of concrete structures, particularly pre-stressed
concrete structures, presently allows for creation of a wide
variety of extremely strong, and even extremely large, structures
falling into a wide range of types. Bridges, buildings, aprons, and
other structures may be constructed by pre-casting of large
concrete support sections and transporting such sections to the
location of construction. In addition to pre-casting, a large
number of items are still cast in situ, and the cumulative total of
cast concrete items, pre-cast, cast on site, pre-stressed or
otherwise, is enormous. U-beams, box beams, I beams, bulb-P beams,
aprons, walls, beams, pillars, foundations and anything else cast
in place or pre-cast may be considered to have the characteristics
and problems discussed herein, although bridge beam sections will
be selected as the exemplary context of the present invention.
[0006] The paramount consideration in any type concrete casting is
the question of safety, which normally devolves to a question of
initial strength and maintenance of strength despite aging,
weathering and so on.
[0007] Normally, a cast bridge section, whether pre-cast at a plant
or cast on site, will be a pre-stressed beam section of a tub or
box-like cross section. The actual thickness of the pre-cast
concrete (and the cross sectional thickness of the form producing
it) are actually normally quite thin, that is, the concrete is a
(relatively) thin shell surrounding a fairly large interior
space.
[0008] It is of great importance to the initial and continuing
strength of the concrete section that the pre-stressing cable
buried in the device are properly positioned at the time of
pre-stressing. However, in actual practice, according to the "PCI
BRIDGE DESIGN MANUAL", Chapter Three, FABRICATION AND CONSTRUCTION,
section 3.2.1, (page 11 of chapter three), "Plant-cast concrete
bridge products are structurally efficient sections which are
relatively thin and congested with reinforcements and embedments.".
One immediate concern which arises in that context is the placement
of the pre-stressing duct and cable buried in the concrete
structure's wall's prior to the pouring of the concrete. The
concrete is extremely heavy, of course. As the concrete enters the
form, it may move items within the form: reinforcement members
("re-bar" or layers of steel or entire mats of reinforcement
members), ducts designed to hold the pre-stressing cables and thus
the pre-stressing cables themselves, ducts or other conduits for
such items as liquid or electrical cables and so on.
[0009] In the event that pre-stressing duct and cable is shifted,
the result can be a greatly weakened bridge section, which in turn
can conceivably have disastrous consequences. While pre-cast
concrete bridges are extremely safe, the real world is not, and it
is well documented that ships do frequently ram bridge abutments,
trains derail onto bridges, users overload bridges, battle damage
brings down bridges and so on. More insidiously, a mis-placed
pre-stressed duct and cable may lead to long term issues with the
bridge.
[0010] Testing by means of ultrasound and drill coring carried out
by one company under real-world conditions revealed that pre-stress
cable ducts moved during construction or pouring, even though the
ducts were properly wired in accordance with industry standard
techniques. This resulted in concrete walls that were too thin in
places. As miscasting a single bridge section can result in losses
of hundreds of thousands or millions of dollars to the company
doing the construction, this is both a safety issue and an economic
issue, and yet further a compliance issue.
[0011] Searching in the United States Patent and Trademark Office
collection of patent documents reveals little that is similar to
the invention taught herein.
[0012] "Bar chairs" or "slab bolsters" are known for holding re-bar
in place during casting of concrete products. Such devices are
typically elongated polymer or steel articles with numerous pairs
of parallel legs for support, the legs typically extending sideways
from the body but then making matching ninety degree turns to run
the same direction ("down") and support the device. Such devices
resemble nothing so much as a large polymer centipede. (See PRIOR
ART FIG. 12). Other types of devices may resemble small polymer
stools or the like. (See PRIOR ART FIG. 13). None are known which
have the structure of the present invention and thus none are known
which resemble the invention.
[0013] U.S. Pat. No. 4,021,979 issued to Rez on May 10, 1977,
teaches a bracket shaped device for in-lace casting having no
structural resemblance to the present invention.
[0014] U.S. Pat. No. 4,251,047 to Holtvogt on Feb. 17, 1981 teaches
a hold down device having a swivel and multiple bolts, for holding
cables, not cable ducts, and entirely lacking legs of any
description.
[0015] U.S. Pat. No. 4,807,843 issued Feb. 28, 1989 to Courtois et
al teaches a plug type device having no apertures or legs.
[0016] U.S. Pat. No. 5,259,586 to Miller, Sr. on Nov. 9, 1993
teaches an elaborate offset box beam structure for retention of
concrete rather than ducts.
[0017] U.S. Pat. No. 5,469,677 issued in the name Luthi on Nov. 28,
1995 teaches an anchor for stressing of concrete, however, the
anchor lacks arms, duct apertures and so on.
[0018] U.S. Pat. No. 6,047,515 issued to inventor Behlen on Apr.
11, 2000, teaches another type of bracket lacking the structures of
the present application: a flat body, apertures, legs and so
on.
[0019] U.S. Pat. No. 6,155,810 issued to Thim on Dec. 5, 2000
teaches an actual bed or mold for casting of prestressed concrete
but does not teach anything relevant to maintaining duct in
place.
[0020] U.S. Pat. No. 6,550,834 issued to Fromelius on Apr. 22, 2003
teaches an insert designed to create a void space, and lacking
arms, a flat body, duct apertures and so on.
[0021] U.S. Pat. No. 7,089,710 issued to Nicholson on Aug. 15, 2006
teaches a clamp, having two arms dimensioned and configured to
engage a conduit, however, it lacks arms spanning the width of a
concrete form, having no flat planar body, and lacking concrete
apertures allowing concrete to pass through the body of the
device.
[0022] U.S. Pat. No. 7,143,991 issued to Hirokawa et al on Dec. 5,
2006 teaches a vaguely cylindrical device which also lacks the
features of the present invention.
[0023] None of these devices show a substantially planar body with
legs projecting in opposite directions to a width equivalent to a
form interior width, nor yet duct apertures.
[0024] It would be preferable to provide a device and method
allowing duct work, particularly pre-stress cable duct work, to be
accurately and firmly secured within a concrete form.
[0025] It would further be preferable, and is a device, embodiment,
aspect, objective and advantage of the present invention to provide
a device allowing free flow of concrete through the form.
[0026] It would yet further be preferable and is a device,
embodiment, aspect, objective and advantage of the present
invention to provide a device and method which save on labor of
wiring ducts to interior components of a concrete cast and yet is
inexpensive to produce and use.
SUMMARY OF THE INVENTION
General Summary
[0027] The present invention teaches both an improved concrete form
duct chair and also an improved method of forming concrete
structures. The duct chair of the invention may be used to hold in
proper placement pre-stress strand (cable) ducts within a form as
concrete is added to the form during the construction of the
concrete member.
[0028] The concrete form duct chair of the invention has a
generally flat body of polymer, metal, wood, etc, the body having
passing through itself several apertures dimensioned and configured
to accept pre-stressing strand duct, so that the concrete form duct
chair may allow the cable ducts to pass through, thereby holding
them in place.
[0029] Several alignment legs project from the body, either in
plane or in other dimensions. The alignment legs and body are
dimensioned and configured to extend for a total width
approximately equal to such cross sectional width of such concrete
form and thus hold the concrete form duct chair in position against
the walls of the form. Four or more legs are preferable to provide
complete stability.
[0030] Concrete access apertures passing through the body allow
concrete to pass therethrough during pouring operations, thus
helping to avoid void areas within the final concrete
structure.
[0031] A method embodiment of the invention teaches pouring of
concrete structures with pre-stressing strands passing therethrough
using the device of the invention to retain the pre-stressing
strands in alignment within the concrete form. Several different
ordering of the steps of the method of the invention may be used
within the scope of the present invention.
[0032] Summary in Reference to Claims
[0033] It is therefore another aspect, advantage, objective and
embodiment of the invention, in addition to those discussed
previously, to provide a concrete form duct chair of a concrete
form having both a first cross sectional width and a first
pre-stressing strand duct, the first pre-stressing strand duct
having a first pre-stressing strand duct diameter, the concrete
form duct chair comprising: [0034] a generally flat body; [0035] a
first duct aperture passing through the body, the aperture having a
first duct aperture diameter approximately equal to such first
pre-stressing strand duct diameter; [0036] first and second
alignment legs projecting from the body, the alignment legs and
body dimensioned and configured to extend for a total width
approximately equal to such cross sectional width of such concrete
form; and [0037] a first concrete access aperture passing through
the body, the concrete access aperture dimensioned and configured
to allow semi-liquid concrete to pass therethrough.
[0038] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a concrete form duct chair,
wherein the material of duct chair comprises one member selected
from the group consisting of: polymer, metal, wood, and composites
thereof.
[0039] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a concrete form duct chair,
further comprising: [0040] third and fourth alignment legs
projecting from the body, the third and fourth alignment legs and
body dimensioned and configured to extend for a total width
approximately equal to such cross sectional width of such concrete
form.
[0041] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a concrete form duct chair,
further comprising: [0042] a second duct aperture passing through
the body, the aperture having a second duct aperture diameter
approximately equal to such first pre-stressing strand duct
diameter.
[0043] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a concrete form duct chair,
further comprising: [0044] a second concrete access aperture
passing through the body, the second concrete access aperture
dimensioned and configured to allow semi-liquid concrete to pass
therethrough.
[0045] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a method of casting concrete
structures comprising the steps of: [0046] a) erecting a first
concrete form side having an internal cross sectional width to make
a concrete form; [0047] b) providing at least one duct chair having
a generally flat body and a first duct aperture passing through the
body, the aperture having a first duct aperture diameter
approximately equal to such first pre-stressing strand duct
diameter, the generally flat body further having at least first and
second alignment legs projecting from the body, the alignment legs
and body dimensioned and configured to extend for a total width
approximately equal to such cross sectional width of such concrete
form, the body further having a first concrete access aperture
passing through the body, the concrete access aperture dimensioned
and configured to allow semi-liquid concrete to pass therethrough;
[0048] c) securing the at least one duct chair and a duct passing
through the duct aperture into the concrete form; and [0049] d)
casting concrete into the concrete form.
[0050] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a method of casting concrete
structures, further comprising: [0051] e) placing a first mat of
reinforcing steel members into the concrete form prior to securing
the duct chair and duct into the concrete form.
[0052] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a method of casting concrete
structures, further comprising: [0053] f) placing the duct through
the duct chair aperture prior to securing the duct chair and duct
into the concrete form.
[0054] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a method of casting concrete
structures, further comprising: [0055] g) placing the duct through
the duct chair aperture after securing the duct chair into the
concrete form.
[0056] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a method of casting concrete
structures, further comprising: [0057] h) securing the duct chair
in place using fasteners.
[0058] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a method of casting concrete
structures, wherein the fasteners further comprise one member
selected from the group consisting of: [0059] wires, flexible
fasteners of plastic/polymer, string, twine, rope, cable, screws,
nails, brads, tacks, bolts, snap fasteners, hook-and-loop fabric,
sleeves, and combinations thereof.
[0060] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a method of casting concrete
structures, further comprising: [0061] i) placing a second mat of
reinforcing steel members into the concrete form after securing the
duct chair and duct into the concrete form.
[0062] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a method of casting concrete
structures, further comprising: [0063] j) erecting a second
concrete form side defining the internal cross sectional width
between the interior and exterior concrete form sides.
[0064] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a method of casting concrete
structures, further comprising: [0065] k) providing a first layer
of steel plating in the form.
[0066] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a method of casting concrete
structures, further comprising: [0067] l) allowing the concrete to
cure after pouring.
[0068] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a method of casting concrete
structures, further comprising: [0069] m) stressing the concrete
casting after pouring.
[0070] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a method of casting concrete
structures, further comprising: [0071] n) stressing the concrete
casting immediately after pouring.
[0072] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a method of casting concrete
structures, further comprising: [0073] o) stressing the concrete
casting at a first time duration after pouring.
[0074] It is therefore another aspect, advantage, objective and
embodiment of the invention to provide a method of casting concrete
structures, further comprising: [0075] p) separating the concrete
casting from the form.
BRIEF DESCRIPTION OF THE DRAWINGS
[0076] FIG. 1 is a planform diagram of a first embodiment of the
device having four conduit apertures and shorter alignment legs.
The diagram may be either a top or bottom view of the device.
[0077] FIG. 2 is a planform diagram of a second embodiment of the
device having four conduit apertures and longer alignment legs. The
diagram may be either a top or bottom view of the device.
[0078] FIG. 3 is a planform diagram of a third embodiment of the
device having three conduit apertures and shorter alignment legs.
The diagram may be either a top or bottom view of the device.
[0079] FIG. 4 is a planform diagram of a fourth embodiment of the
device having three conduit apertures and longer alignment legs on
one side. The diagram may be either a top or bottom view of the
device.
[0080] FIG. 5 is a side view of an alternative embodiment of the
device having three alignment legs per side.
[0081] FIG. 6 is a side view of an alternative embodiment of the
device having three alignment legs per side.
[0082] FIG. 7 is an end view of the device.
[0083] FIG. 8 is a cross sectional view of an embodiment of the
device in use while a concrete section form is being prepared.
[0084] FIG. 9 is a greatly simplified cross sectional view of a
prior art U-tub beam with an imposed load.
[0085] FIG. 10 is a partial cross-sectional side view of a simple
bridge structure showing a single "pre-stressing strand" cable in
use in a support beam.
[0086] FIG. 11 is a flow chart showing an exemplary method of the
invention.
[0087] FIG. 12 is a diagram of a PRIOR ART bar chair for holding
rebar in place during concrete pouring operations. It may be seen
to be completely unsuited by structure to holding ductwork in
place.
[0088] FIG. 13 is a diagram of a PRIOR ART bar chair of a different
type.
INDEX OF REFERENCE NUMERALS
[0089] Duct aperture 12 [0090] Concrete aperture 14 [0091] Leg 16
[0092] Body/side 18 [0093] Duct aperture 22 [0094] Concrete
aperture 24 [0095] Leg 26 [0096] Body/body side 28 [0097] Leg 32
[0098] Duct aperture 34 [0099] Concrete aperture 36 [0100] Body
side 38 [0101] Leg 42 [0102] Duct aperture 44 [0103] Concrete
aperture 46 [0104] Body 48 [0105] Leg 52 [0106] Leg 62 [0107] Duct
chair 801 [0108] Form walls 802, 804 [0109] Open end 806 [0110]
Rebar lattice 808 [0111] Duct support aperture 810 [0112] Duct 812
[0113] Alignment leg 814 [0114] Deck 906 [0115] Reinforcement 910
[0116] Duct 912a, 912b [0117] Support column 1002 [0118]
Pre-stressed concrete beam 1004 [0119] Deck 1006 [0120] Pre-stress
cable 1008 [0121] Design 1102 [0122] Set up form side 1104 [0123]
Reinforce and embed 1106 [0124] Duct through duct chair 1108 [0125]
Place duct and chair 1110 [0126] Reinforce and embed 1112 [0127]
Set up form side 1114 [0128] Cast concrete into form 1116 [0129]
Cure concrete 1118 [0130] Pre-stress 1120 [0131] Remove form
1122
DETAILED DESCRIPTION
[0132] FIG. 12 is a diagram of a PRIOR ART bar chair for holding
rebar in place during concrete pouring operations. It may be seen
to be completely unsuited by structure to holding ductwork in
place. FIG. 13 is a diagram of a PRIOR ART bar chair of a different
type. Both types and other common types are largely used to hold
rebar in place during concrete pouring, and as such, merely need a
flat surface or area of supports which will prevent rebar from
drifting one direction when concrete is poured. However, these
structures will not serve adequately in the context of trying to
prevent motion at any location except close to the bottom surface
of a pour, that is, the prior art may serve adequately when pouring
a flat apron onto flat ground, as the rebar resting atop the device
will be held up off the ground during the pour, however, in a tub
beam, the form is oriented at an angle to the horizontal and a
prior art chair would simply tumble down the inside of the
form.
[0133] FIG. 9 is a greatly simplified cross sectional view of a
prior art U-tub beam with an imposed load. Deck 906, the imposed
load, is supported by the "tub" shaped beam below it. The beam may
be seen to contain both reinforcement 910 and also ducts 912a,
912b, which contain pre-stressing cables. It will be understood
that the pre-stressing of the structure by means of the cables
contained in the ducts will provide a great deal of additional
strength to the concrete U-tub beam, strength above that of
non-pre-stressed concrete. Seen from the side, a bridge section
made in this manner would look somewhat like FIG. 10. FIG. 10 is a
partial cross-sectional side view of a simple bridge structure
showing a single "pre-stressing strand" cable in use in a support
beam. Support column 1002 supports one end of a pre-stressed
concrete beam 1004, which in turn supports the imposed load of deck
1006. The scale of such structures may be quite large, for example,
deck 1006 may be an eight lane highway, with columns 1002 more than
100 feet tall. Such a highway bridge may have long sections
comprising a single U-tub beam 1004 (and as seen in cross-section
in FIG. 9, already referenced). Pre-stressing cable 1008 may be
seen in partial cross-section. The effectiveness of cable 1008 in
providing extra strength to the bridge is dependent upon the proper
positioning of the cable 1008: in the wrong location or orientation
it may provide no strength to the concrete by failing to properly
pre-stress the concrete. Worse, in some cases the cable 1008 may
actually reduce the strength of the concrete if the mis-alignment
brings the cable too close to the surface of the U-tub beam.
[0134] Thus, it would be preferable to provide a device able to
ensure proper alignment of the pre-stressing cable in such a U-tub
beam. In numerous other contexts, it would preferable to provide
exact location of a wide variety of embedments in a concrete cast
article.
[0135] The term concrete as used herein refers to any mixture of
cement, water, aggregate whether fine or course, and additional
admixtures such as are often used at the present time. The term "an
aperture dimensioned and configured to allow semi-liquid concrete
to pass therethrough" therefor may in turn refer to various sizes
of aperture, as a larger aperture will be required for mixtures
having relatively course aggregate, in a state of partial cure,
having constituent admixtures which impact the viscosity of the
concrete or are otherwise less prone to pass through an aperture
than other mixes, while smaller apertures may be used in more
typical circumstances.
[0136] It will be understood that the device of the present
invention is substantially depicted in the context of a concrete
tub beam or the like with simple concrete mixtures and a limited
range of embedments and reinforcements, however, the invention is
not so limited and may be used with a wide range of aggregates,
admixtures, water-reducers, retarders, accelerators, air-entraining
admixtures, corrosion inhibitors, mineral admixtures, prestressing,
pretensioning, post-tensioning, a wide variety of strand sizes and
duct sizes, a wide range of duct and strand spacings and
arrangements, a wide variation in the quantities of ducts, strand
anchors, strand couplers, epoxy coatings and other coatings,
indented strands and various strand profiles, prestressing bars,
and even with non-prestressed concrete structures and
reinforcements. It may be used with a wide variety of deck systems
and panels, diaphragm casting, water-cement ratios, heat
application regimes, planned voids, and other aspects of concrete
casting. It may be used with precast and cast-in-place
construction.
[0137] FIG. 1 is a planform diagram of a first embodiment of the
device having four conduit apertures and shorter alignment legs.
The diagram may be either a top or bottom view of the device, which
has a substantially planar (flat) two dimensional body with various
apertures therethrough and alignment legs extending therefrom in
one, two or three dimensions so as to provide an exact alignment to
ducts passing through duct aperture 12. Duct aperture 12 will have
a diameter which may be varied as required to match to a particular
duct on a particular job.
[0138] Concrete access aperture 14 may similarly vary in dimension
and shape in order to provide maximum concrete access in the form
with minimum blockage of concrete during pouring. It will be
understood that large webs on the body of the device are generally
undesirable as they are likely to promote voids within the
concrete, an obvious safety issue. Thus the webwork of the body 12
of the device may be interrupted by one or more concrete access
apertures 14 so that as liquid concrete enters the form during
pouring, the concrete penetrates efficiently, without voids
occurring behind the invention.
[0139] Leg 16 may extend from the body on one, two, three, four or
more sides, so as to maintain the device in proper alignment within
the concrete form and thus maintain the duct, and thus the cable
within the duct, in the proper alignment. Note that the ducts used
are not necessarily limited to pre-stressing strand ducts, they may
be ducts for other cables (electrical and so on) or for deliberate
passages through the device or for another purpose or function
desired.
[0140] Body/side 18 may advantageously be made of polymer/plastic,
preferably a mixture having advantageous material properties when
embedded in a concrete matrix. Metal may also be used, as may wood,
advanced composite materials, combinations thereof and other
suitable materials now known or later developed.
[0141] In the presently preferred embodiment and best mode
presently contemplated for carrying out the invention, the
dimensions of the device will be specified for the nature of the
concrete structure being cast. That is, a device for use in a
concrete shell 24 inches in thickness might advantageously have
legs and body spanning a total width of 24 inches, so as to have
the ends of the legs rest on both form sides during construction. A
device for use with three ducts of 4.5 inches diameter may of
course advantageously have three duct apertures of approximately
4.5 to 5 inches diameter, and so on.
[0142] FIG. 2 is a planform diagram of a second embodiment of the
device having four conduit apertures and longer alignment legs. The
diagram may be either a top or bottom view of the device. Duct
aperture 22, concrete aperture 24 and body 28 may be substantially
as previously described, however, it may be seen that leg 26 may be
a different length than legs on other portions of body 28. By this
means, the exact placement and orientation of the cable ducts may
conveniently be provided anywhere within the concrete structure,
not merely in the exact center of the shell.
[0143] In the presently preferred embodiment and best mode
presently contemplated for carrying out the invention, four or more
legs are found to provide the best support, alternative embodiments
with less may be used as convenient, however, the use of four or
more legs appears to provide the best alignment.
[0144] FIG. 3 is a planform diagram of a third embodiment of the
device having three conduit apertures and shorter alignment legs.
The diagram may be either a top or bottom view of the device. Leg
32, duct aperture 34, and concrete aperture 36 may be seen to
occupy different relative positions in relation to each other. In
comparison to the first two embodiments, there is not a pair of
legs projecting from an area of the body located in between two
duct apertures (in contrast to leg 16 of FIG. 2), the size of
concrete access holes is different and so on.
[0145] Body side 38 may be seen to be either straight, curved, or a
combination of both, and may include angles and other shapes useful
in alignment, for example, projections designed to grasp other
embedments.
[0146] FIG. 4 is a planform diagram of a fourth embodiment of the
device having three conduit apertures and longer alignment legs on
one side. The diagram may be either a top or bottom view of the
device. Again, leg 42, duct aperture 44 and concrete aperture 46
may vary in their placement on body 48, with legs of differing
length and only three ducts. Thus, it may be seen that the range of
combinations of the elements of the invention is quite broad.
[0147] FIG. 5 is a side view of an alternative embodiment of the
device having three alignment legs per side. Leg end 52 may be seen
projecting therefrom, as in FIG. 6 (a side view of an alternative
embodiment of the device having two alignment legs per side)
leg/leg end 62 may be seen. The ends of the legs may rest against
the opposing sides of the concrete form so as to provide the
desired alignment. FIG. 7 is an end view of the device, showing
that sides of the device may if desirable be plain, without legs
projecting therefrom.
[0148] FIG. 8 is an extremely simplified cross sectional view of an
embodiment of the device in use while a concrete section form,
either open top or not, is being prepared.
[0149] Duct chair 801 sits between form walls 802, 804, at a
position somewhat below form top 806. Rebar lattice 808 (some
elements seen in cross section as circles, other elements seen
longitudinally as long members) may be seen in place, as may duct
support aperture 810, through which duct 812 passes.
[0150] Significantly, it may be seen that alignment leg 814 holds
the device in place against one, or in the best mode, BOTH form
walls 802, 804, providing proper alignment to the duct 812. In past
methods, wiring of the duct into place was quite common, however,
use of wire was extremely labor intensive and testing at one
concrete casting company has shown that wiring may not effectively
hold the ducts in proper placement during the concrete pour.
[0151] FIG. 11 is a flow chart of an exemplary embodiment of the
method of the invention.
[0152] The first step of most concrete casting will be design, step
1102, of both the article and then the concrete form to make the
article. After design, step 1104 is the setting up of a first side
of the form, for example, the interior wall of the tub (reference
numeral 804 in FIG. 8) or the exterior wall (reference numeral 802
in FIG. 8). Usually, the exterior wall would be the first wall,
however, it is conceivable that it might be done in reverse order,
or even that the walls might be made after all the embedments,
though this is not the best mode contemplated.
[0153] Reinforcement and other embedments are then placed in the
form at step 1106. Rebar mats are one obvious example of this.
[0154] In prior practice, the rebar mats might then be used as a
support structure to wire in the ducts which would hold the
pre-stress strand. However, as previously noted, testing has
revealed that this may not be sufficiently reliable.
[0155] Duct may then be placed through duct chair at step 1108, and
then the duct and chair may be secured into the form at step 1110.
However, it is also possible to place the chairs into the form and
run the ductwork therethrough and remain within the scope of the
invention claimed herein.
[0156] Additional reinforcement and embedding may occur at step
1112.
[0157] Setting up of the other form side 1114 may not be necessary
in a "one sided" form, however, in the best mode now contemplated,
the method of the invention is used with "shell" type forms such as
beams. Note that setting up the form's first side 1104 may occur as
late in the process as concurrent with step 1114.
[0158] Casting of concrete into the form at step 1116 is the step
in which prior art devices (wire) often failed to secure the duct
work in place. This step is the point at which the concrete is
finally introduced into the form, and it is during this step that
the concrete access apertures (such as aperture 14 of FIG. 1) may
allow concrete to pass freely through the device, preventing the
formation of voids.
[0159] Curing of concrete (step 1118) may as previously noted occur
with various heat regimes (electric heat, steam heat and others) or
without, with or without curing agents and so on. Pre-stressing of
the concrete using the pre-stressing cable 1120 may occur at this
time or at a later time, even at the actual job site.
[0160] Removal of the form at step 1122 completes the process and
allows transportation to the job site, unless the cast is occurring
at the construction site. Removal may occur as early as concurrent
with step 1116 or anytime thereafter.
[0161] It is important to understand that the order of steps shown
in FIG. 11 is merely exemplary. For example, the interior form side
may be constructed first and the exterior last, or the embedments
and reinforcements may be placed first and both form sides later,
the ducts may be placed and then the duct chairs added (using
embodiments having split ring duct apertures), the duct chairs may
be installed and then the duct run, stressing may occur at a first
time interval after curing or even at the construction site and so
on and so forth in numerous permutations and combinations.
[0162] All dimensions and configurations of the device may have a
wide range of values. For example, for a first cast concrete item,
the values of Table One might be used:
TABLE-US-00001 TABLE ONE Duct Aperture Diameter 3.375 inch Concrete
Aperture Diameter 0.675 inch Leg Length 2.0 inch
END TABLE ONE
[0163] However, it will be understood that the dimensions of Table
One, like the layouts shown in the diagrams, are merely exemplary.
Each manufacturer of duct and cable makes differing sizes of duct,
requiring different sizes of duct aperture. Each bridge section may
be a unique width, requiring different leg lengths. And pouring
conditions (how liquid the concrete is at the moment of pouring,
the composition of aggregates and admixtures and so on) may
drastically impact the size of the concrete aperture. Thus Table
Two is an equally valid size of device, even though the dimensions
may be seen to be radically different.
TABLE-US-00002 TABLE TWO First Duct Aperture Diameter: 1.125 inch
Second Duct Aperture Diameter: 12 inch First Concrete Aperture
Diameter: 0.125 inch Second Concrete Aperture Diameter: 2.75 inch
First Leg Length: 0.5 inch Second Length: 12.5 inch
END TABLE TWO
[0164] From these dimensions it may be seen that a single chair
might have two lengths of legs (for example if the ducts are to be
maintained quite close to one side of a thick wall, an admittedly
unusual situation but within the scope of the patent claims made
herein). There may be multiple diameters and shapes of concrete
access apertures, depending on the shape of web of the body, and
there may be multiple duct diameters if different cables or
purposes are being met by the ducts embedded in the concrete
construction.
[0165] Thus, the device may vary quite a bit: duct apertures may be
"split" so as to allow them to be placed around a duct rather than
the duct fed through the aperture, apertures may be shapes other
than circular, leg length may vary, the device may be offset from
the center of the concrete shell and so on and so forth.
[0166] The disclosure is provided to allow practice of the
invention by those skilled in the art without undue
experimentation, including the best mode presently contemplated and
the presently preferred embodiment. Nothing in this disclosure is
to be taken to limit the scope of the invention, which is
susceptible to numerous alterations, equivalents and substitutions
without departing from the scope and spirit of the invention. The
scope of the invention is to be understood from the appended
claims.
* * * * *