U.S. patent application number 11/207738 was filed with the patent office on 2006-03-23 for components for use in large-scale concrete slab constructions.
Invention is credited to William Grant Brown.
Application Number | 20060059804 11/207738 |
Document ID | / |
Family ID | 36072380 |
Filed Date | 2006-03-23 |
United States Patent
Application |
20060059804 |
Kind Code |
A1 |
Brown; William Grant |
March 23, 2006 |
Components for use in large-scale concrete slab constructions
Abstract
Structural reinforcing members are supplied for use in resisting
shear forces within larger construction projects using reinforced
concrete, along sites where strengthening ribs or beams between
formers are to be created. The members also force the channels
apart and maintain the reinforcing therein before curing at
predetermined dimensions and spacings. A variant provides
reinforcing cages that can be put together on the site for
maintaining multiple reinforcing rods. The cages of different beams
can intermesh at rib cross-over points. Example cages are eight-bar
cages where each bar is made of 1.25 inch diameter reinforcing
steel. During assembly the bars are held in place by the members
with the assistance of gravity so that relatively little linking
together of the reinforcing parts is required.
Inventors: |
Brown; William Grant;
(Waitakere City, NZ) |
Correspondence
Address: |
YOUNG & THOMPSON
745 SOUTH 23RD STREET
2ND FLOOR
ARLINGTON
VA
22202
US
|
Family ID: |
36072380 |
Appl. No.: |
11/207738 |
Filed: |
August 22, 2005 |
Current U.S.
Class: |
52/223.13 |
Current CPC
Class: |
E04C 5/0645 20130101;
E04C 5/168 20130101; E04C 5/0604 20130101 |
Class at
Publication: |
052/223.13 |
International
Class: |
E04C 5/08 20060101
E04C005/08 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 20, 2004 |
NZ |
534828 |
Sep 27, 2004 |
NZ |
535598 |
Claims
1. Components to form part of the reinforcement for a reinforced
concrete structure, wherein the components serve to (a) determine
the dimensions of strengthening beams or ribs of concrete to be
formed as part of the structure, by delimiting and occupying spaces
between rigid formers that will contain the concrete after pouring,
(b) dictate the placement of reinforcing bars of metal within the
strengthening beams or ribs of concrete by providing clear
attachment points for holding said reinforcing bars at
predetermined positions, and (c) serve in themselves as structural
reinforcement components orientated in order to resist shear stress
applied to the strengthening beams or ribs of concrete.
2. Components as claimed in claim 1 wherein each component is
formed from metal.
3. Components as claimed in claim 1 wherein the components are used
along the strengthening beams or ribs of concrete as a series of
single components (herein termed "structural stirrups") and each
single component includes (a) more than one attachment points for a
corresponding reinforcing bar held at a predetermined position, and
(b) at least one attachment point capable of locating the component
with respect to an adjacent former so that each component is
capable of holding said reinforcing bars at predetermined positions
with respect to the adjacent former.
4. Components as claimed in claim 1 wherein each component is used
as a member of a group of components for assembly as part of the
structure during construction, and each group of components after
assembly includes (a) more than one attachment point for more than
one reinforcing bars each held at a predetermined position, and (b)
at least one attachment point for location with respect to an
adjacent former so that each single component is capable of holding
said reinforcing bars at predetermined positions with respect to
the adjacent former, and (c) each group of components after
assembly serves as a cage assembly capable of holding said more
than one reinforcing bars at predetermined positions.
5. A reinforced concrete structure including a cage assembly as
claimed in claim 4.
6. A reinforced concrete structure including intersecting cages
constructed in position.
7. A method for assembly of a group of components as claimed in
claim 4 along the course of an intended strengthening beam or rib,
between formers, including the steps of: a) placing deep
non-structural "pod spacers and bar organisers" along the channel
in order to locate and hold the void formers in place during later
component placement, and thereby to maintain the channel width, b)
placing a structural "inverted top hat" deep bar-holding bent wire
shape with sufficient depth to support a first, lower layer of bars
at the deepest level, alongside each pod spacer and bar organiser,
c) placing a deep array of structural reinforcing rods in the
grooves provided by the deep series of pod spacers and bar
organisers, d) placing shallow non-structural pod spacer and bar
organisers along the channel, e) placing a shallow array of
structural reinforcing rods in the grooves provided by the shallow
series of pod spacers and bar organisers, f) placing an inverted
"U" structural element to serve as part of the cage over the
shallow array of reinforcing rods, in alignment with the "inverted
top hat" g) fixing the structural elements to each other, so that
the assembly is ready for receiving wet concrete and providing
reinforcement once the concrete has cured.
8. A method as claimed in claim 5, further wherein at positions
where beams of reinforced concrete are intended to intersect, the
respective arrays of reinforcing rods are installed so as to cross
over each other thereby creating and installing interlocking
reinforcing cage assemblies.
9. A method as claimed in claim 8, wherein should beams of
reinforced concrete be intended to intersect, those groups of
components for use with a first set of reinforcing rods oriented in
a first direction is made longer in order to reach to a greater
depth than the groups of component for use with a second,
intersecting set of reinforcing rods by about the diameter of the
reinforcing rods, so that the sets of reinforcing rods may cross
over each other without bending.
Description
FIELD
[0001] This invention relates to building construction, to the
provision of reinforcement for concrete structures, and in
particular to structural components for incorporation in reinforced
concrete masses to become built structures such as floors,
buildings, bridges, or roads.
BACKGROUND
[0002] Concrete is a widely used cold-castable "liquid stone" used
as a building material. After the reactions involved in setting and
curing have taken place it has good compressive strength but
relatively poor tensile and shear strength, so rods of reinforcing
iron are cast into masses of concrete in order to restore tensile
and shear strength. For use in mainly single-storey domestic
housing floors poured as single slabs, the inventor has previously
described a floor construction technique using buried void formers
(made from a foam plastics such as polystyrene foam) to form a
matrix of stiffening beams in the spaces left between the formers,
using the inventor's stirrups to place reinforcing iron within the
rods, in order to provide a stiff concrete floor for an optimised
amount of materials. The void formers may have useful thermal
insulating properties. Instead of void formers, other types of
formers that contain the wet concrete within intended spaces may be
used in some constructions.
[0003] The bent-wire stirrups (also called spacers) keep the
formers apart and hence define the minimum width of concrete that
will comprise each stiffening rib and also serve to hold the
reinforcing iron and the void formers in place until the concrete
has been poured and has set within each channel that is
deliberately formed between the void formers. Other items such as
pipes may be tied on to the stirrups. The entire working surface of
the concrete floor is also provided with buried reinforcing mesh in
typical floors. Single-pour concrete slab floors are often laid
upon the ground (or grade as it is called in North America).
[0004] The final result after pouring and curing the concrete is a
slab having a surface layer of concrete completely covering a
reinforcing mesh layer that together have sufficient strength to
resist predicted point loadings in particular, and below those is a
crisscrossed array of deep concrete ribs each including reinforcing
bars, separated by voids, together having sufficient strength to
avoid failure of the slab as a whole. There is usually an outer
border also made of a deep concrete rib including reinforcing bars.
The design of each slab should be specified by an engineer in order
to provide a desired strength and the procedure may be checked
immediately before pouring in order to verify that channels of a
desired width depth and length, containing iron bars in the correct
positions within, are present. In contrast with the present
structural invention the channels formed with the prior-art
stirrups are small and weak (though appropriate for the job), and
would lack the required ability to adequately withstand the
stresses experienced in a larger construction.
[0005] This construction procedure is comparatively quick, has low
labour costs, such as by reducing the amount of tying-together of
reinforcing with wire, and the cost of raw materials is minimised.
Use of these stirrups sharply reduces the labour content of a
floor.
[0006] In relation to larger constructions, another laborious
prior-art practice which is overcome by means of the present
invention is that of assembling large cage structures of iron
reinforcing bars, frames, and tie wire (or welds) typically
off-site and then bringing them to the job and placing them in or
on the structure that is to become reinforced concrete using a
crane. Problems associated with this technique include the matter
of creating cage structures of just the right size (let alone
possible distortion during transport and placement) and of moving
the heavy, large, and not particularly strong structures safely and
conveniently to their final positions.
[0007] In this invention the term "structural stirrup" or
"structural spacer" generally refers to a stirrup in which the
material of the stirrup itself is capable of resisting shear
stresses applied to a beam or rib of reinforced concrete in which
it is implanted.
OBJECT
[0008] It is an object of this invention to provide components and
a process for the construction of floors made from reinforced
concrete capable of withstanding relatively high loadings, or at
least to provide the public with a useful choice.
STATEMENT OF INVENTION
[0009] In a first broad aspect this invention provides structural
components for use as part of the reinforcement of a reinforced
concrete structure, wherein the components serve to dictate the
dimensions of strengthening beams or ribs of concrete to be formed
as part of the structure by delimiting and occupying spaces between
rigid formers that will contain the concrete after pouring.
[0010] Preferably also the components provided are capable of
determining the placement of reinforcing bars of metal within the
strengthening beams or ribs of concrete by providing attachment
points for supporting said reinforcing bars at predetermined
positions until casting is complete.
[0011] Preferably also the components provided are capable of
serving as structural reinforcement components orientated in order
to resist shear stress applied to the strengthening beams or ribs
of concrete.
[0012] Preferably each component is formed from metal.
[0013] Preferably each component is made of a stiff metal rod bent
into a desired shape. A preferred stiff wire is steel rod in the 5
to 12.5 mm range, although the material used to form structural
members is preferably of steel of a comparable thickness to that of
the bars used in the construction. Optionally the steel rod is
provided with a surface treatment capable of inhibiting
corrosion.
[0014] In one option, the components are used along the
strengthening beams or ribs of concrete as a series of single
components and each single component includes (a) more than one
attachment points each for a reinforcing bar of a reinforcing
structure held at a predetermined position, and (b) includes at
least one attachment point for location of the component with
respect to an adjacent former so that each single component is
capable of holding said reinforcing bars at predetermined positions
with respect to the adjacent former and (c) includes sufficient
internal tensile strength to serve as a structural element of the
reinforcing structure.
[0015] In another option, the components are used as members of a
group of components used along the strengthening beams or ribs of
concrete as a series of groups of components for assembly into part
of the structure during construction, and each group of components
after assembly includes (a) more than one attachment points for
more than one reinforcing bars each held at a predetermined
position, and\(b) at least one attachment point for location with
respect to an adjacent former so that each single component is
capable of holding said reinforcing bars at predetermined positions
with respect to the adjacent former, and (c) each group of
components after assembly serves as a cage assembly capable of
holding said reinforcing bars at predetermined positions.
[0016] In a related aspect the invention provides a set of
components for use as a group in reinforced concrete structures;
the set including an upper bar support, a lower bar support and
channel spacer, a lower cage stirrup, and an upper cage member; all
to be used as spaced-apart sets in conjunction with reinforcing
rods placed horizontally within channels.
[0017] Preferably the group comprises an "n-bar cage" where n may
be from two to sixteen bars of reinforcing rods.
[0018] In a second broad aspect this invention provides a method
for assembly of a group of components as previously described in
this section between formers and along an intended strengthening
beam or rib, including the steps of: (a) placing non-structural
"pod spacers and bar organisers" along the channel in order to to
locate and hold the void formers in place during later component
placement, and thereby to maintain the channel width, (b) placing a
structural "top hat" deep bar-holding bent wire shape with
sufficient depth to support a first, lower layer of bars at the
deepest level, alongside each pod spacer and bar organiser, (c)
placing a deep array of structural reinforcing rods in the grooves
provided by a series of pod spacers and bar organisers, (d) placing
a shallow non-structural pod spacer and bar organiser, (e) placing
a second, shallow array of structural reinforcing rods, (f) placing
an inverted "U" structural element to serve as part of the cage
over the shallow array of reinforcing rods, and then (g) fixing the
structural elements to each other such as by tying or welding, so
that the assembly is ready for receiving wet concrete and providing
reinforcement once the concrete has cured.
[0019] Preferably the respective arrays of reinforcing rods are
installed so as to cross over each other at positions where beams
of reinforced concrete are intended to intersect, thereby creating
interlocking reinforcing cage assemblies at the site.
[0020] Preferably, where intersection of respective arrays of
reinforcing rods is expected, the groups of components for use in a
first set of beams is made longer than the groups of components for
use in a second, intersecting set of beams by about the diameter of
the reinforcing rods, so that the arrays of reinforcing rods may
cross over each other without being bent.
[0021] Optionally the upper lengths of reinforcing iron are placed
to lie above the reinforcing mesh and below the surface of the
concrete.
Preferred Embodiment
[0022] The description of the invention to be provided herein is
given purely by way of example and is not to be taken in any way as
limiting the scope or extent of the invention. Variations which
would be obvious to a skilled reader are to be considered as
forming part of the invention.
DRAWINGS
[0023] FIG. 1: is a diagram showing a section across a reinforced
channel according to Example 2 of the the invention.
[0024] FIG. 2: is a perspective diagram taken from a photo to show
reinforcing bars placed in a channel, according to the
invention.
[0025] FIG. 3: is a perspective diagram also taken from a photo
from within a channel, showing perpendicular groups of reinforcing
bars crossing over each other.
[0026] FIG. 4: is a diagram showing a structural stirrup according
to Example I of the invention.
[0027] FIG. 5: illustrates example prior-art components--FIG. 5a
shows a non-structural stirrup and FIG. 5b shows a piece of
reinforcing iron bent to provide a four-bar cage.
[0028] FIG. 6: is another diagram showing a two-bar structural
stirrup according to the invention.
[0029] FIG. 7: is another diagram showing a structural stirrup for
use along a rib line where the floor surface height is stepped.
[0030] FIG. 8: is another diagram showing a structural stirrup for
use in the perimeter of a foundation.
[0031] The inventor's original stirrups (alternatively called
spacers) intended for small constructions are symmetrical bent
metal objects, typically as shown in prior-art FIG. 5a, showing a
non-structural stirrup with all bends in a single plane. There is
but one portion adapted for holding a reinforcing iron bar--the
lowest part; the corner at 20 so that the eventual concrete rib
(typically 6 inches across and 12 inches deep) will include one
central length of reinforcing iron. Such ribs have significantly
less structural strength as compared with those made of larger (eg
268 mm wide, at least 260 mm deep) concrete ribs having structural
applications and including more, larger bars at a variety of
heights. Non-structural ribs are suitable for single-floor
dwellings with floating slab-on-grade floors, whereas structural
ribs are required wherever the anticipated loads are higher.
[0032] The preferred manufacturing technique for these bent metal
objects is to use a numerically controlled wire-bending machine, so
long as available machines have the strength to cold-bend the
desired thickness of rod. Another way to make stirrups from any
thickness of iron rod is by heating the rod to red heat, then
bending it around pegs on a jig, and preferably coating the
finished product with an anti-corrosion treatment. Stirrups can
also be made by casting, moulding, cutting, or any other method
known to one skilled in the art, and the materials selected can be
selected from a large range of materials offering sufficient
strength as required during the period of construction of the
concrete structure.
[0033] All stirrups along the same channel usually have the same
shape and are laid at typically 18 inch spacings. Both end portions
of the prior-art stirrup of FIG. 5a --403 and 404 (occasionally
only one end--for use at perimeters, as in prior-art FIG. 8)
terminate in a downwardly projecting section 401 and 402 used to
impale and fix the stirrup in relation to a void former. (Options
may be adapted for use with other forms of fastening, such as holes
through flattened end portions for use against timber formers with
nails or screws). Between the end portions there is a channel
defining portion, comprising a downwardly projecting "U" shape
405-501-406 which in use occupies a channel that is typically 6 to
8 inches wide between adjacent void formers. Within the channel
defining portion there is one or sometimes more downwardly directed
recesses 501 for supporting horizontal reinforcing bars that will
be laid to pass along the length of the channel.
[0034] The recess or recesses are usually placed so that the bars
will lie at controlled positions deep in the interior of the
concrete rib that will be formed in the channel when concrete is
poured within. The stirrup prevents the bar(s) from being too close
to the base or to any exterior surface. The cover of concrete
provides strength and may be mandated for protection against
corrosion. Use of a rod material as the material for the stirrup
minimises any interruption to the integrity of the concrete rib
along its length--as compared for example to plastics moulded
versions. The strength required of the stirrup is for temporary
holding purposes only.
EXAMPLE 1
Structural Stirrups
[0035] Structural stirrups, also known as structural spacers
because they space apart bars and void formers (or other formwork),
provide extra points for locating lengths of reinforcing iron
within a channel so that the resulting rib will have a structurally
useful degree of strength. Examples are shown as FIGS. 4, 6, 7 and
8. They include bends to locate bars of reinforcing iron at a range
of depths. The structural stirrup of FIG. 4 includes
downward-directed bends at 409, 401 and 415 that can hold bars by
gravity alone, avoiding the labour costs of placing wire ties.
Extra bars could be tied in at 407 and 408, providing either a
three-bar reinforced rib, or a five-bar reinforced rib.
[0036] FIG. 4 shows a typical structural component, according to
the invention, for use in reinforced concrete structures.
(Dimensions are given by way of illustration only). This component
is made of 6.4 mm diameter steel rod, formed by bending in a
numerically controlled bending and cutting machine. Although that
method might seem unduly complex or slow, it is automated and the
versatility of the machinery suits the wide variety of particular
shapes and sizes that are required from time to time for these
components. The components to be described by example here
illustrate the principles of the invention but by no means the
entire possible range of examples.
[0037] Note that the example structural stirrup shown in FIG. 4
includes the following components: downwardly projecting free ends
401, 402 intended to impale and hold (with the help of gravity) the
void formers and the reinforcing together as one unit until locked
in place by poured concrete, separated by a bridging portion
including two horizontal sections 403, 404 which lie over the
surface of the void former thereby holding the formers down during
pouring and maintaining a standardised height for the structural
stirrup; two vertical contact sections 405, 406, for defining and
maintaining the space between void formers; two central raised
"bar-holding corner" portions 407, 408, for locating lengths of
reinforcing rod--(the inside of bends made in the originally
straight rod); and to each side of each, a depressed holding corner
portion 409, 410 which is maintained at at least a certain distance
inside the channel between adjacent void formers by the descending
limbs; by the sloping separators 411, and 412. The spacing between
the structural reinforcing rods in the vertical axis is maintained
by the straight sections 413, 414. The "valley" 415 may be used as
a place for a further length of reinforcing rod or this can be
regarded as a distance-maintaining separator between rods 407 and
408 and as a depressed zone where a bar of the reinforcing mesh can
pass. Similarly the distance between 405 and 406 determines the
width of the channel between the voids which is to become filled
with concrete including the reinforcing materials held by the
structural stirrups.
[0038] It will be apparent that each structural stirrup is made of
an elongated material having (a) ends, (b) straight portions, and
(c) bent portions. Most bends are formed in a single plane although
bends can be made in any plane and the examples may make use of
advantages of bending in other planes. Note that although the
present embodiment has bent portions which are made by actually
bending a straight piece of stock, the aware reader will be able to
see that stirrups having flexures (corners) fulfilling these
functions might be made by other processes such as injection
moulding a plastics material into a die, by casting molten metal,
by cutting from a sheet, by slumping, or by bolting, welding, or
otherwise fixing together a number of parts into stirrups. Use
herein of the verb "to bend" or its variants does not preclude
alternative manufacturing processes.
[0039] In use, four lengths of reinforcing iron tied to this
structural stirrup at corners 407, 408, 409 and 410 have about the
same effect on tensile and shear strength as would four lengths of
reinforcing iron provided as a prior-art four-bar cage (FIG. 5b)
but with the advantages that the stirrup is a structural element,
and the substitute for the cage provided by the invention is
supported from the void formers so that the position of the bars
and of the entire cage within the rib of concrete is better defined
(for example they must lie at least 50 mm inside the concrete beam
according to New Zealand building code requirements, to reduce
corrosion and enhance function), and little or no wire tying is
needed. In some situations there may not be any nearby void
formers, when the prior-art four-bar cage can be used to hold the
rods together across a gap. As will be described later, there are
advantages in creating an equivalent to a cage on the job rather
then as a prefabricated component.
[0040] A suitable vertical separation between lengths of
reinforcing iron may be obtained by having the upper pair of rods
lying on or above the almost universally used reinforcing iron mesh
(not shown) which is buried to 30 or 50 mm under the surface of the
finished slab. Parts 407 and 408 of the structural stirrup poke
through the mesh. Using the mesh to support the upper beams makes
wire tying (if necessary) much easier than if the weight of the
bars has to be supported during and after tying. If the upper
corners are formed as functional rings then the mesh does not need
to support the upper pair of bars which could make the labour of
installation easier, as long as poking bars through holes is
feasible. Functional rings could comprise a loop of about 1.5
turns, or the portion of the stirrup leading to the valley 115
could be brought sideways and down in a "fat U" profile rather than
the "V" profile shown here, so that the surface profiles of corners
107 and 108 are closed.
[0041] Note that these structural stirrups also have a number of
associated functions:
[0042] 1. They define and keep open the channels between void
formers before concrete setting.
[0043] 2. They locate the void formers in position over the surface
that is to become a concrete slab and hold them down by the weight
of the iron bars onto the underlying damp course or other surface
to prevent any inadvertent movement by the weight of the iron
before pouring. This weight includes the weight of subsequently
placed reinforcing mesh, usually (but dependent on application)
1/10 or 1/8 inch diameter iron rod, welded into mesh with 10 inch
squares.
[0044] 3. They accurately locate the heights, directions and
horizontal locations of the reinforcing bars (iron) that provide
the concrete slab with useful structural properties.
[0045] 4. They can be used as frames to tie the reinforcing bars
down, and to each other, at correct placements.
[0046] 5. The highest corners (407, 408) which emerge above the
plane of the reinforcing mesh in some versions can be used to tie
down the mesh beneath the upper reinforcing bars.
[0047] The structural stirrup of FIG. 6 includes two bar holding
bends only, at 601 and 602 within a concrete rib 4 1/2 inches wide
and about 10 inches deep. These bars are well separated in height,
for extra flexural strength of the final construction. Because bend
601 is made to lie above reinforcing mesh, if used, and well above
the upper surface of the void formers, if used, this stirrup is
suited to use with relatively thick coverings of concrete over the
void formers. (604 may also be used to hold a bar but it will lie
rather too close to the edge of the concrete for approval by some
building inspection authorities).
[0048] The structural stirrup 700 of FIG. 7 provides for up to five
bars, at 703 and 707 held by gravity, 704, 705 and 706 (held with a
tie), and the height difference between 703 and 707 increases the
bar separation for extra strength. This stirrup also provides for a
step change in concrete height by virtue of the lower height of
horizontal portion 702 as compared to portion 701. Such a step
change in floor height could have been specified in the plans for
the construction. The height of the void former on the left (under
portion 701) may be 4 inches higher than the height of the void
former 702 on the right. This example illustrates the design
freedom provided by use of numerically controlled manufacture.
[0049] The FIG. 8 asymmetrical structural stirrup 800 is intended
to locate lengths of reinforcing iron within a perimeter channel
around the outside of a slab-on-grade concrete floor. This type
provides holding corners for three reinforcing bars placed at 804,
805, and 806 in specified relationships to the outer corner of the
void former, thereby providing structural strength. Only one
impaling end (801) at the end of horizontal 802 is provided because
there will be no void former on the outside, but the stirrup at or
about 807 may be stapled or otherwise attached to wooden or other
formwork. located to the right of the stirrup so that the poured
concrete is held in place. This diagram also shows the preferred
extended, zig-zag limb 801 which enhances the grip of the
structural stirrup into the void former and tends to minimise
sideways deflection. Limb 803 may also be formed as a zigzag. The
bends in 801 are not shown because they are made in a plane
perpendicular to the plane of the illustration and to the rest of
this stirrup. An about 10 inches (255 mm) wide rib of concrete is
defined by means of this example structural stirrup.
EXAMPLE 2
Cage Constructions, Assembled on the Site
[0050] A further development of the present invention that is
intended for significantly greater loadings is partly based on a
non-structural stirrup as per FIG. 5a, but with additional parts.
Further, it resembles a cage structure, but one that is preferably
assembled on site. Some functions of a simple stirrup, such as
determination of the channel size are retained. By way of
comparison, we first describe a prior-art four-bar cage structure
illustrated as FIG. 5b. In this cage, which has an indefinite
length, four bars such as 502, 504, 505 and 506 are tied to a
series of bent reinforcing iron bars 503 which serves to maintain
the bars in a spaced-apart configuration after embedment in
concrete, so that the resulting reinforcement has greater strength
to resist torques. Larger cages would use stouter rods and have
more of them.
[0051] This description and these drawings are based on a specific
prototype, show an eight-bar cage, and refer to certain dimensions.
The prototype is a demonstration intended to cater to one site's
specifications. The experienced reader will be aware that floors
(or road surfaces, etc) may be designed to various degrees of
strength by the responsible engineers and hence wide variations in
bar numbers, diameters, positions, and other variables can be
imposed according to requirements while staying within the general
principles of the invention.
[0052] The example of FIG. 1, also shown as an installation in
perspective in photographs in FIGS. 2 and 3 is a mid-range size
example of an on-site cage/stirrup composite that illustrates the
principles of the invention. Several bent wire or bent rod items
are grouped together in assemblies that are used repeatedly along a
channel and which are linked, welded, or tied to at least some
reinforcing bars laid along the channel. Usually an entire floor
would be poured as one slab once a number of cage/stirrup
assemblies had been installed, although if the resulting floor is
considered too large in relation to potential shrinkage and
expansion of the concrete, expansion joint formers may be inserted
as is standard practice in the industry. It is convenient to
describe the structure in a preferred order of assembly. [0053] 1.
The first step, after laying out, is to place void formers 102, 103
made of a material such as a polystyrene foam of an appropriate
degree of density along each side of each channel. Preferably each
void former fills the area between one channel and a neighbouring
parallel channel, while usually including a second array of
channels oriented perpendicular to the first channels, herein
termed the first array. (Note that the cage/stirrup composite
structure may be tied to other structures in a construction that
does not include void formers as such, such as a construction dug
into the ground as a criss-crossed array of trenches, or one using
boxing made of wood or cardboard. The cage aspect of the invention
does not dependent on void formers for its operation). Void formers
(or other structures) may be raised above the grade on supporting
blocks 104, or on piles, in part to provide a level top surface at
103, 102 and in part to provide a deep space to receive concrete at
117. Damp-course material may be included below, as is standard
practice, or if a suspended floor or other structure is being
built, a lower temporary layer will have been put in place. Not
shown here is the preferred option of using a disposable hard board
(such as "Hardibacker (TM)" or plywood) as a protective surface
over the top of the void formers so that the pods can better
withstand the normal stresses of labourers (even vehicles) moving
over them while carrying bars and other things during assembly of
the floor. [0054] 2. The first laid components, known as "pod
spacers and bar organisers" serve to locate and hold the void
formers in place during later component placement. These first-laid
components are visible between impaling end 107A and 110 in FIG. 1,
including downward-projecting limbs 107 and 109 that define the
channel width by preventing a closer approach of the void formers,
and at least one but typically downwardly four bar
position-defining bends 108 along a wiggly part of this component.
(This component being thinner is easier to bend freely than the
next component to be inserted). We prefer that the length of all
droppers holding "east-west" orientated bars is about one bar
diameter longer than those holding "north-south" droppers (or vice
versa) so that bars can cross over each other without impediment.
Hence it can be seen that the dimensions of the various bent metal
"bridging elements" sets the positions of the reinforcing bars
inside. The height of the valleys and hence the ironwork above the
grade is something normally determined by the engineer or by
ordinances. A typical suitable spacing along each channel is for
example 2 to 4 feet (0.6 to 1.2 metres) apart. [0055] 3. The second
laid component is for weight-bearing purposes It is a deep
bar-holding bent wire shape having an inverted top hat profile
113-113 lacking the end impaling sections, and with the depth of
the "U" sufficient to locate the recesses for holding a first,
lower layer of bars at the deepest level, is placed alongside each
stirrup. This heavier bar serves to support the weight of the
reinforcing material and to transfer the weight to the adjoining
void formers (or other structure). It is bent so that the bars
lying in the bar position-defining bends 108 are in contact with
this bent wire shape. This bar is not required to define the
channel width although it may do so. The first and second
components may be combined into one component. [0056] 4. The third
laid component is a deep array of reinforcing rods 105A, 105B,
105C, 105D which are possibly cut to length and are now placed in
the channel and may be tied down. (Tying down may be a regulatory
requirement although the bars are not likely to move on account of
their weight). The lower set of bars, to lie under the other
perpendicular set, are of course laid first. These bars are
relatively heavy but each is compatible with handling by two or
more men, unlike a finished cage, and a crane is not required.
[0057] 5. The fourth laid component is a shallow bar-holding bent
wire shape. Like the second laid component, this is made of a
lighter wire and is preferably bent to include impaling ends, for
retention during installation, and has a central series of at least
one but typically four bar position-defining bends 118. [0058] 6.
The fifth laid component is a shallow array of reinforcing rods
106A, 106B, 106C, 106D which are now placed in the channel and may
be tied down. Again, the lower set of bars, to lie under the other
perpendicular set, are of course laid first. These bars are
relatively heavy but each is compatible with handling by two or
more men, unlike a finished cage. [0059] 7. The sixth laid
component is the upper "U" section of the cage 119-119' which is
dropped down over the top set of bars. This item is used to cover
and retain the most shallow set of bars. It should be fixed to the
sides of the second laid component so that it will not spring
upwards for any reason and allow the upper bars, or itself, to
approach the surface of the intended pour of concrete. A suitable
fixing means is a wire tie at 115. We find it faster and more
convenient to use an arc welder to spot weld the cage components
together such as at 115, 116. If this is done the structure becomes
quite immobile. If anti-corrosion coatings have been specified the
weld should be sprayed with a zinc spray or similar, once cooled.
[0060] 8. Normal practice is to cover the upper surface of the
concrete, over the entire area of the slab and including the void
formers with a reinforcing iron mesh, supported above the void
former surface by support blocks or devices known in the trade
as"bar stools" that support the mesh deep within typically 4 to 6
inches of concrete. Then the assembly is ready for inspection and
then pouring. Of course, other items to be included within the
concrete such as pipes and cables should be placed before pouring.
[0061] 9. It will be appreciated that a middle layer of reinforcing
bars could also be placed in the channel if required.
[0062] As a result of this procedure, the channel is provided with
eight substantial steel bars running along its length. These bars
are variously known as "Reo bars, HD32, reinforcing material, or
"Seismic 500" and each is about 1 to 1.5 inches in diameter. These
replace a conventional "eight-bar cage" which under prior-art
methods would have been made with wire tying outside the work site,
trucked in, and lifted into position by crane. Four bottom bars
105A . . . 105D are positioned first, by placement on top of
aligning structures placed in the channels at a suitable spacing
such as 600 mm, 1 metre, or 1.2 metres apart. One structure is the
bent wire "pod spacers and bar organisers" 107-109 in FIG. 1. The
other structure is the "structural box cage stirrup" 111 in FIG. 1.
Both structures are U-shaped and are supported by their ends (113,
113' and 110) against the upper surfaces of the pods.
[0063] FIG. 2 is a perspective view (taken from a photograph)
looking down on a channel including reinforcing according to the
procedure and materials described previously in this section. This
was an experimental prototype and some of the stirrups (e.g. 110)
are temporarily lifted up on packers 201 to adjust the heights of
the supported bars. 202 is a distant view of an intersecting
channel and other numbers are as per FIG. 1.
[0064] FIG. 3 is a perspective view (from a photograph taken within
the assembled channel), looking at an intersection of channels
where the lower arrays of bars intersect. In prior art methods of
making reinforced floors, this simple laying procedure resulting in
intermeshed cages would not be feasible. The labourers do have to
remember to lay the lower sets of bars first and preferably use
longer or shorter stirrups 109 for both top and bottom sets of bars
according to positions. Alternatively, different heights of bar
chair may be used to support the bent stirrups. In FIG. 3, the
lower sets of bars are in view (the top set 106A-D are only just
visible). The set 105A . . . D corresponds to those of FIG. 1. The
set 305 A-D is a second set arriving at the intersection at right
angles. Again there is no need to tie or otherwise fix the bars
together unless there is a small discrepancy to be overcome or if
there is a regulatory requirement to tie.
[0065] Under prior art methods, bars would be cut and tied to
bridging bars which pass by each other at an intersection. This
significantly weakens the structure and takes time and labour
units.
[0066] The large bars are usually about 30-60 feet long. They are
best joined up by an end-to-end butt with a bridging rod tied (or
welded) to both of them, over at least 2 feet overlap on each
side.
[0067] It will be appreciated that two labourers can carry a large
metal bar from a pile to an end-use site while they create the
n-bar cages about the floor. Therefore there is no requirement to
have a crane to work over the floor areas to handle pre-assembled
four-bar or eight-bar cages.
VARIATIONS
[0068] There is wide scope for variation in sizes and shapes of
spacers/stirrups for specific applications, and for locations of
holding corners within any type of spacer, directed to controlled
positioning of the bars in relation to the concrete rib, for
specific tasks.
[0069] An engineer may specify a selected inter-spacer spacing
along a channel, the number and size of the reinforcing bars to be
used, and the position of each bar within the channel, in view of
the cross-sectional area of the concrete in the beam, and according
to structural requirements such as the expected load, plus safety
margins while obeying the limits imposed by any standards or
building codes in force at the site.
INDUSTRIAL APPLICABILITY AND ADVANTAGES
[0070] The advantages include: [0071] 1. reduced labour time
(perhaps by about 80% labour reduction in one estimate) during
preparation of the reinforcing iron and hence labour cost, as well
as a reduced amount of undesirable jobs on the site (because tying
cages and beams is an unappealing job. The skill level is lessened.
The overall cost of a built structure is reduced. [0072] 2. The
method provides ease of specification, better assurance that
specifications are being followed, and is well adapted for
inspections such as before pouring. [0073] 3. The four-bar,
six-bar, or similar cages are constructed at the position of end
use within the trenches and do not need to be trucked (by
relatively ineffectively loaded trucks) to the site already made
up, and lifted into position by crane. [0074] 4. "Seamless"
intersections of four-bar, six-bar, or similar cages in a first or
"north-south" direction with four-bar, six-bar, or similar cages
running in the perpendicular or "east-west" reinforcing bars can be
created at the time of bars placement, including crossing over of
bars, while retaining structural integrity. [0075] 5. Use of a
numerically controlled wire bender, or other rod shaping means,
allows good freedom when adapting the basic idea to specific
construction site requirements. [0076] 6. The metal reinforcing is
positively held within the concrete to be poured. Potential "close
approaches" to a perimeter of the body of concrete can be
anticipated and prevented by means of supports ("bar chairs")
and/or by anti-corrosion treatment of metal at risk. [0077] 7. This
system does not impose any breaks along the length of the
reinforced rib, whereas some plastic prior art analogues having
flat profiles inevitably interrupt the concrete.
[0078] Finally, it will be understood that the scope of this
invention as described and/or illustrated herein is not limited to
the specified embodiments. Those of skill will appreciate that
various modifications, additions, known equivalents, and
substitutions are possible without departing from the scope and
spirit of the invention as set forth in the following claims.
* * * * *