Note: Descriptions are shown in the official language in which they were submitted.
CA 02867964 2014-10-16
PREFABRICATED MODULAR REBAR MODULES AND METHODS OF USING THE
SAME
FIELD OF THE INVENTION
This invention relates generally to the broad field of reinforced concrete and
more
particularly to the steel, or rebar used to reinforce the concrete. More
particularly, this
invention relates to methods and apparatus for constructing and installing
rebar used in
concrete construction.
BACKGROUND OF THE INVENTION
Reinforced concrete is a well known and widely used building material which is
used in building, bridges, roads, tunnels and other structural construction
projects.
Essentially the concrete, which is strong in compression but has no strength
in tension,
is reinforced with steel rods which pass through the zones of tension in the
structural
element. Engineers design the structural components; calculate the forces
which will be
generated by the structure, which may be carrying dynamic or static loads or
both; and
then develop a rebar plan to provide enough rebar reinforcement in the regions
of the
concrete structure where tension forces may be created. The rebar plan often
requires
complex cages with rebar elements bent from, for example, a top surface to a
bottom
surface and then back to the top surface to accommodate the load pattern
created in a
beam supported by a column for example.
Conventionally, rebar rods are transported individually to a work site and
then
assembled on site. In some cases they may be bent on site and in other cases
they
may be bent at the factory and merely assembled on site. Assembly means
placing the
rebar rods into a form which will then hold the liquid concrete which is
poured into the
form around the rebar. Once the concrete cures and hardens the forms can be
removed and the structural element is ready for use.
The rebar is typically provided with a textured outer surface to enable the
concrete to better grip the steel bars. The assembly of the rebar into the
forms is done
with great care ¨ the correct positioning of the rebar is required to ensure
the structural
element has the strength that it has been designed for. Each rebar element
must be
precisely located in the three dimensional space within the form to ensure
appropriate
load bearing capacity of the finished structural element. Thus the engineers
provide the
fabricators with exact rebar cage plans and designs and every rod is checked
for correct
positioning before any concrete is poured.
CA 02867964 2014-10-16
-2-
The fabrication of the re-bar cage according to the detailed design
specifications
can be slow and tedious work. The rebar components are connected on site by
workers
using ties with wires. The rods themselves can be long and unwieldy. The
position of
the components each have to carefully measured to ensure that they are
properly
spaced and located and that they will be located at an appropriate depth
within the
concrete once the concrete is poured into the form. The entire process of
installing the
components on site can be time consuming, which in turns increases the costs
of the
projects. Delays in the construction of rebar cages can cause significant
delays in the
entire construction project since the installation of reinforced concrete will
often be one
of the first steps in a major building project. For example, in a building the
concrete
frame of the building must be in place before the windows and interior
finishing can be
attempted within the frame. Since the installation of the rebar components
requires
rodworkers and other workers to be present on site, any staffing issues may
also cause
delays in the overall project. Construction of rebar structures onsite also
requires each
structure to be custom made.
Constructing rebar structures for raft and transfer slabs onsite is also
awkward in
that incomplete cage assemblies may lead to partially built cage structures
that are
shaky and hard to walk on, causing safety issues. Installation may also be
more
challenging where confined spaces exist during the construction of the slab
layers. It
may also be challenging to place rebar on slabs that are deeper than 1800mm or
approximately 6' in depth. Slabs are typically 2' to 12' deep.
Patent applications of general interest in the field of rebar include:
U.S. Patent No. 5,392,580 patented on February 28, 1995;
U.S. Patent No. 8,381,479 patented on February 26, 2013; and
U.S. Appl. No. 2009/0014419 published on January 15, 2009.
SUMMARY OF THE INVENTION
What is desired is a simpler and more efficient way of constructing reinforced
concrete structures.
In an embodiment there is a modular reinforcing steel structure for use in a
concrete building wall. The structure may comprise one or more prefabricated,
welded
modular cages having vertical reinforcing bars. The cages may be prefabricated
in an
CA 02867964 2014-10-16
-3-
offsite factory where there are the space, tools and workers to quickly and
easily create
the modular cages. There may be a plurality of continuous ties extending
around the
vertical reinforcing bars and a plurality of shear ties extending generally
horizontally
between the vertical reinforcing bars. Each prefabricated welded cage may be
sized
and shaped for shipping and said structure may be quickly and easily formed
onsite
from a plurality of said modular cages lapped together.
In another embodiment there is provided a method of constructing a reinforcing
steel structure for use in a concrete building wall. A plurality of
prefabricated, welded
cages having vertical reinforcing bars are provided at a worksite. Each of the
plurality of
prefabricated, welded cages may have a plurality of continuous ties extending
around
the vertical reinforcing bars and a plurality of shear ties extending
generally horizontally
between the vertical reinforcing bars. The plurality of prefabricated, welded
cages may
be installed at a worksite. Reinforcing steel bars are installed between the
plurality of
prefabricated, welded cages to form a continuous reinforcing steel structure.
Concrete is
added to the reinforcing steel structure to form a concrete building wall.
In another embodiment there is a reinforcing steel structure for use in a
concrete
building transfer or raft slab. The structure comprises one or more
prefabricated, welded
beams. The prefabricated, welded beams may comprise a top beam layer having
horizontal reinforcing bars, a bottom beam layer having horizontal reinforcing
bars, and
a plurality of continuous ties extending generally vertically around the top
beam layer
and the bottom beam layer. Each welded beam may be sized and shaped for
shipping
and said structure can be formed onsite from a plurality of said beams lapped
together.
In another embodiment there is a method of constructing a reinforcing steel
structure for use in a concrete building slab. A plurality of prefabricated,
welded beams
may be provided at a worksite. The welded beams may comprise a top beam layer
having horizontal reinforcing bars, a bottom beam layer having horizontal
reinforcing
bars, and a plurality of continuous ties extending generally vertically around
the top
beam layer and the bottom beam layer. A bottom slab layer comprising a
plurality of
horizontal reinforcing bars may be installed. The plurality of prefabricated,
welded
beams may be installed adjacent to one another on the bottom slab layer. A top
slab
layer comprising a plurality of horizontal reinforcing bars is installed on
the plurality of
welded beams to form a reinforcing steel structure. Concrete is poured around
the
CA 02867964 2014-10-16
-4-
reinforcing steel structure and permitted to cure to form a concrete building
slab.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference will now be made by way of example only to preferred embodiments
of the invention by reference to the following drawings in which:
Figure 1 is a top view of an embodiment of a prefabricated, welded cage for a
heavy wall;
Figure 2 is a top view of an embodiment of a continuous tie for use in a pre-
fabricated, welded cage;
Figure 3 is a top view of a PRIOR ART configuration of u-caps and horizontal
bars for use in a concrete wall structure;
Figure 4 is a top view of an embodiment having two prefabricated, welded cages
for a heavy wall;
Figure 5 is a top view showing a pair of lap bars connecting two continuous
ties;
Figure 6 is a top view of a PRIOR ART configuration of u-caps and horizontal
bars for use in a concrete wall structure;
Figure 7 is a top view of an embodiment of a steel structure made from a
plurality
of pre-fabricated, welded cages;
Figure 8 is a top view of an embodiment of a steel structure made from a
plurality
of pre-fabricated, welded cages for use in walls with zones;
Figure 9 is a top view of a section of an embodiment of a steel structure made
from a plurality of pre-fabricated, welded cages for use in a wall with zones;
Figure 10 is a top view of an embodiment of a steel structure having a
plurality of
prefabricated, welded cages.
Figure 11 is a side view of an embodiment having a pair of prefabricated
welded
beam for use in a transfer slab or raft slab;
Figure 12 is a perspective view of an embodiment of a bottom slab layer of
Figure 11 for a transfer slab or raft slab;
Figure 13 is a perspective view of an embodiment of a prefabricated, welded
beam of Figure 11 for installation in a transfer slab or raft slab;
Figure 14 is a perspective view of an embodiment of Figure 11 having a pair of
prefabricated, welded beams installed on a bottom slab layer;
CA 02867964 2014-10-16
-5-
Figure 15 is a perspective view of an embodiment of Figure 11 of a top slab
layer
installed on top of a pair of prefabricated, welded beams;
Figure 16 is a side view of an embodiment having a pair of prefabricated,
welded
beams having shear ties;
Figure 17 is a perspective view of an embodiment of a bottom slab layer of
Figure 16;
Figure 18 is a perspective view of an embodiment of a prefabricated, welded
beam of Figure 16 for a transfer slab or raft slab;
Figure 19 is a perspective view of an embodiment of a steel structure having a
pair of prefabricated, welded beams of Figure 16 installed on a bottom slab
layer; and
Figure 20 is a perspective view of an embodiment of a steel structure of
Figure
16 having a top slab layer installed on a pair of prefabricated, welded beams.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A prefabricated welded cage 104 is shown in Fig. 1. The prefabricated welded
cage 104 includes a number of vertical reinforcing bars 106. A continuous tie
108
extends around the vertical reinforcing bars 106. Although only one continuous
tie is
shown in Fig. 1, it will be understood that the welded cage 104 includes a
plurality of
continuous ties 108 which are placed at vertical intervals around the vertical
reinforcing
bars 106. Preferably, the plurality of continuous ties 108 are spaced at even
intervals
along the height of the vertical reinforcing bars 106. A plurality of shear
ties 110 extend
generally horizontally between the vertical reinforcing bars 106. The welded
cage 104 is
sized and shaped for shipping.
The structure of one of the plurality of continuous ties 108 is shown in Fig.
2. The
continuous tie 108 shown in Fig. 2 is a single piece of reinforcing steel that
forms a
closed loop with, for example, ends that overlap.
In Fig. 3, a prior art design for rebar components in a wall structure is
shown. A
pair of horizontal bars 120 is connected to a pair of u-caps 118 at each end.
This
structure would need to be constructed using individual horizontal bars and u-
caps on
site and then carefully connected to each of the vertical reinforcing bars
106. Installation
of this prior art system would likely be expensive and time consuming.
CA 02867964 2014-10-16
-6-
Fig. 4 and 5 show how two prefabricated welded cages 104B and 104C may be
installed at a work site. The two cages 104B and 1040 are placed side-by-side
as
shown in Fig. 4. As shown in Fig. 5, a pair of lap bars 116 are connected
between each
of the adjacent continuous ties 108B and 108C. For each of the plurality of
continuous
ties 108B and 1080 in each of the cages 104B and 1040, pairs of lap bars 116
are
connected between them. Multiple cages may be connected in this manner. The
pair of
welded cages 104B and 104C are placed adjacent and parallel to each other for
use in
a single length of a concrete building wall. The plurality of lap bars 116
extend generally
horizontally between overlapping adjacent ends of the pair of welded cages.
As shown in Fig. 4, each of the plurality of shear ties 110 have a hook end
112
and a flat end 114. In the embodiment shown in Fig. 4, the plurality of shear
ties 110 are
arranged between the vertical reinforcing bars 106 in an alternating parallel
pattern with
the hook ends 112 of each adjacent shear tie facing in an opposite direction.
Fig. 6 shows a prior art method of installing a section of wall, which
requires a
long horizontal bar 120 and u-caps 118 connecting the horizontal bars 120 at
the ends
of the components. This installation method has similar drawbacks to the prior
art
method shown in Fig. 3.
Fig. 7 shows a reinforcing steel structure 100 including a plurality of the
one or
more prefabricated, welded cages 104. In this case there are shown four welded
cages
104A, 104B, 1040, and 1040. The reinforcing steel structure 100 has a corner
pair of
welded cages 104A and 104B which are placed adjacent and perpendicular to each
other for use in two adjoining walls forming a corner of a concrete building
wall. A
plurality of u-caps 118 extend generally horizontally around adjacent ends of
the pair of
welded cages. The welded cages 104A and 104B meet at a corner generally
denoted
by 126. Similarly, welded cages 104C and 104D are adjacent corner pieces
connected
by a plurality of u-caps 118. Welded cages 104B and 1040 form a parallel pair
of
welded cages placed adjacent and parallel to each other to together form a
structure for
a single length of a concrete building wall. A plurality of lap bars 116
extend generally
horizontally within the vertically reinforcing bars 106 and between
overlapping adjacent
ends of the parallel pair of welded cages 104B and 104C. As will be
understood, various
different combinations and configurations of welded cages 104 may be connected
to
form steel structures for concrete walls of various different configurations
and sizes.
CA 02867964 2015-09-18
-7-
Fig. 8 shows an embodiment of the steel structure 100 having walls with zones
having a different configuration of shear ties 110. In the embodiment shown in
Fig. 8,
Shear ties 110 are placed with the hook ends 112 oriented in the same
direction as each
other and the shear bars 110 are placed at each end of the welded cages 104A
to
104D. Also, although in the embodiment shown in Fig. 7, add bars 122 are used
exclusively as the vertical reinforcing bars 106, in the embodiment shown in
Fig. 8, add
bars 122 are used only at each end of the respective welded cages 104A to
104B. The
shear ties 110 are placed between the add bars 122. The thicker vertical bars
122 are
zone concentrated reinforcing bars and the thinner of the vertical bars 106
represent
stress distributed reinforcing bars.
Fig. 9 shows an embodiment of a portion of a steel structure having welded
cages 1040 and 104D. Hooked horizontal bars 124 are placed at the corner 126
where
welded cages 104C and 104D are adjacent. Horizontal j-bars 116 are located
inside the
vertical reinforcing bars 106 and match the continuous ties 108. The
horizontal bars 124
are also closed ties. The j-bars 116 are embedded between the modular welded
cages
104C and 104D and which may assist in preventing failure when concrete spalls
under
stress.
Fig. 10 shows a steel structure 400 having a plurality of prefabricated welded
cages 404A to 404D. Vertical reinforcing bars 406, all in the form of add bars
422, lie
between continuous ties 408 in each of the welded cages 404A to 404D. Shear
ties 410
connect between the vertical reinforce bars 406 and are placed with the hooked
ends
412 of adjacent shear ties 410 facing in opposite directions. Opposite the
hooked ends
412 of each shear tie is a flat end 414. U-caps 418 provide a connection
between
corners 426 of adjacent welded cages 404A and 404B, as well as adjacent welded
cages 404C and 404D. The embodiment shown in Fig. 10 is similar to the
embodiment
of reinforcing steel structure of Fig. 7, except with the addition of a
plurality of lap bars
416 extending generally horizontally within the vertical reinforcing bars 406
and
between the corner pairs of welded cages 404A and 404B as well as welded cages
404C and 404D. The addition of the plurality of lap bars 416 may be preferred
in cases
where a seismic resistant design is required.
The reinforcing steel structure 100 of Figs. 1, 4, and 7 to 9, may be
installed for
use in a concrete building wall by the following method. The method of
constructing the
CA 02867964 2014-10-16
-8-
steel structure 400 in the embodiment shown in Fig. 10 is similar to the
method of
installing the steel structure 100 shown in Fig. 7. A plurality prefabricated,
welded cages
104 are provided on site at a worksite. The plurality of prefabricated, welded
cages are
installed at a worksite where a concrete wall is to be made. Reinforcing steel
bars are
installed between the plurality of prefabricated, welded cages to form a
reinforcing steel
structure. As shown in Figs. 1, 4 and 7 to 9, the reinforcing bars installed
between the
welded cages 104 may include u-bars, lap bars or other rebar structures that
allow for
the communication of tension stress between the cages. As a final step,
concrete (not
shown) is poured into the reinforcing steel structure 100 to form a concrete
building wall.
Although the walls shown in Figs. 1 to 10 have certain dimensions, it will be
understood that various difference dimensions of walls may be constructed,
using
different sizes of cages depending on the application. The size of the cages
should be
chosen to fall within transportation limits, which may be, for example, 12
feet by 12 feet
by 60 feet. In this sense transportation limits means the size of module that
can be
readily accommodated within the existing size of conventional transport
vehicle (truck,
or train car) that may be used for shipping rebar. While at present the size
as outlined
above is suitable in some jurisdictions, it will be understood that the
present invention
comprehends adapting the size of the modular cages to meet whatever the local
transportation limits might be. Further, while the above noted size limit is
the maximum
size, the present invention comprehends a modular approach and therefore in
some
cases depending upon the structural design, the equipment available on site to
assemble multiple modules into compound cage assemblies the modules may be
made
smaller than the maximum size and yet dimensioned to be efficiently fit within
the typical
transportable volume.
Fig. 11 shows a side view of two prefabricated welded beams 204A and 204B.
The welded beams together form a reinforcing steel structure 200 (Fig. 15) for
use in a
concrete building transfer or raft slab. A plurality of continuous ties 212
extend generally
vertically around a top beam layer 206 having horizontal reinforcing bars and
a bottom
beam layer 208 having horizontal reinforcing bars. Each welded beam 204A and
204B
is sized and shaped for shipping. As shown in Fig. 11, the prefabricated
welded beams
204A and 204B are installed between a top slab layer 214 and a bottom slab
later 218.
The continuous ties 212 shown in Fig. 11 are a single piece of reinforcing
steel that
CA 02867964 2014-10-16
-9-
forms a closed loop.
The components of the reinforcing steel structure 200 are shown in Figs. 12-
15.
The bottom slab layer 218 is shown in Fig. 12. A plurality of bottom
horizontal
reinforcing bars 220 are installed parallel to one another.
A prefabricated welded beam 204 is shown in Fig. 13. The welded beam 204 has
a plurality of vertical continuous ties 212 that extend around top and bottom
beam
layers 206 and 208. The top beam layer 206 has a plurality of top horizontal
reinforcing
bars 210. The bottom beam layer 208 has a plurality of bottom horizontal
reinforcing
bars 211. The top and bottom horizontal reinforcing bars 210 and 211 are
oriented
lengthways along the welded beam 204 and are parallel with one another.
Different
orientations of the horizontal reinforcing bars may be used.
Fig. 14 shows one of the steps in installing the welded beams 204A and 204B in
a steel structure. The welded beams are placed side-by-side on top of the
bottom slab
layer 218. As shown in Fig. 15, the top slab layer 214 is then installed on
top of the
welded beams to form the steel structure 200. As shown in Fig. 15, the top
horizontal
reinforcing bars 210 of the top beam layer 206 lie adjacent to and in the same
plane as
the top horizontal reinforcing bars 216 of the top slab layer 214, with the
two layers
oriented so that the plurality of horizontal reinforcing bars 216 of the top
slab layer 214
are oriented generally perpendicularly to the horizontal reinforcing bars 210
of the top
beam layer 206. Similarly, the bottom horizontal reinforcing bars 211 of the
bottom
beam layer 208 lie adjacent to and in the same plane as the top horizontal
reinforcing
bars 220 of the bottom slab layer 218, with the two layers oriented so that
plurality of
horizontal reinforcing bars 220 of the bottom slab layer 218 are oriented
generally
perpendicularly to the horizontal reinforcing bars 211 of the bottom beam
layer 208. It
will be understood that different orientations of each of the various
horizontal reinforcing
bars may be used.
Figs. 16 to 20 show a steel structure 300 (Fig. 20) comprising a plurality of
prefabricated welded beams 304 installed side-by-side between a bottom slab
layer 318
(Fig. 17) having horizontal reinforcing bars 320 and a top slab layer 314
(Fig. 20) having
horizontal reinforcing bars 316. The prefabricated welded beams 304 are shown
in
more detail in Fig. 16 where the welded beams 304 each include a plurality of
vertical
continuous ties 312 which extend around a top beam layer 306 and a bottom beam
CA 02867964 2014-10-16
-10-
layer 308. The top beam layer 306 formed from a plurality of top horizontal
reinforcing
bars 310 and the bottom beam layer 308 being formed from a plurality of bottom
horizontal reinforcing bars 311.
The embodiment of the steel structure 300 shown in Figs. 16 to 20 is similar
to
the steel structure 200 shown in Figs. 11 to 15, except that the embodiment of
the steel
structure 300 includes a plurality of shear ties 322 extending generally
vertically
between the horizontal reinforcing bars 310 of the top beam layer 306 and the
horizontal reinforcing bars 311 of the bottom beam layer 308. The shear ties
322
include a hook end 324 and a flat end 326. Each of the one or more
prefabricated,
welded beams 304A, 304B include shear ties 322 that are oriented with the hook
ends
324 connected to the horizontal reinforcing bars 310 of the top beam layer
306. As
shown in Fig. 16, the plurality of shear ties 322 form two parallel rows of
shear ties 322
extending along a length of the one or more prefabricated, welded beams 304A
and
304B.
Figs. 12 to 15 and 17 to 20 generally set out the steps in constructing a
reinforcing steel structure 200 or 300 for use in a concrete building slab.
Reference will
be made hereafter to the embodiment of the steel structure 200 shown in Figs.
12 to 15,
but the same method installation applies to the steel structure 300 in Figs.
17 to 20.
Generally, the beams are assembled as units using a combination of welds and
ties at
intersections. The ratio between the number of ties and welds is adjusted as
required
due to loading and flexibility requirements. Although the process described
herein has
two layers of rebar in the top and bottom formed from the top and bottom beam
layers
and the top and bottom slab layers, a similar procedure may be used when there
are
more than two layers of rebar for the top and bottom mats. All welding may be
done in
accordance with local welding standards. Different numbers, orientations and
sizes of
welded beams may be used in a steel structure depending on the application
desired.
Initially, a plurality of prefabricated, welded beams 204 are provided at a
worksite. The beams preferably have dimensions equal to or less than 12 feet
by 12
feet by 60 feet, in order to conform with transportation limits. The size of
the beams may
depend on the transportation limits in different jurisdictions. The plurality
of
prefabricated welded beams 204 may be assembled and welded at a separate
facility
from the worksite. The beams 204 may be delivered on site when the concrete
slab
CA 02867964 2014-10-16
-11-
structure is being constructed. By providing the beams 204 in a prefabricated
form, the
installation process on site may be simplified. The bottom slab layer 218 is
installed as
shown in Fig. 12 at a work site. Next, each of the prefabricated, welded beams
204 are
placed adjacent to one another on the bottom slab layer 218. The bottom slab
layer 218
and the beams 204 may be connected by a suitable combination of welding or
wire ties.
After the welded beams are installed, the top slab layer 214 is installed on
the plurality
of welded beams to form the reinforcing steel structure 200. The top slab
layer 214 and
the beams are connected using welding or wire ties. Finally, concrete (not
shown) is
added to the reinforcing steel structure to form a concrete building transfer
or raft slab.
By installing the steel structure 200 using modular components in the form of
prefabricated welded beams 204, the beams are generally sturdy for
transportation and
installation. The rigidity of the beams 204 may allow them to be walked on and
can
provide a surface to stand on during installation. By providing the beams 204
in a
completed form, it may lessen the need for workers to install rebar components
in
confined spaces. Testing has shown that installation using modulated welded
cages
may reduce installation time by as much as half of the time compared to
traditional
methods.
The prefabrication of welded cages and beams allows each of the connections to
be provided entirely by welding. Preferably, the reinforcing steel in each of
the welded
cages and welded beams are joined using 100% welding, which may increase the
strength of the prefabricated components compared to using wire ties.
Preferably, each
of the one or more prefabricated, welded cages or beams have dimensions equal
to or
less than 12 feet by 12 feet by 60 feet or other suitable dimensions that may
be required
by transportation limits. Different sizes of welded beams may be constructed.
The
welded beams are sized and shaped to suit the profile of the transfer or raft
slab.
Variations of the size and shape may also be required since slabs may have
steps or
slopes on the top or bottom. The welded beams and welded cages are generally
arranged on the transportation vehicles to fit as many as possible onto a
single load.
The amount loaded onto each vehicle also depends on the sequence of delivery,
which
should follow a logical order based on the order each component is installed.
A load of
welded beams or cages may also be combined with additional loads, such as
loose
bars to fully load a transport vehicle. The sequence of transportation may be
of
CA 02867964 2014-10-16
-12-
heightened important since there are frequently issues with the amount of free
space on
site.
Welded cages generally are no wider than 12' in width to meet certain
transportation requirements and the length may be dependent on the length of
wall. The
welded cages may be sized and shaped to fit the least number of cages as
possible in
each wall in order to reduce the number of laps required when installing the
cages. It
may be beneficial to ensure that the wall cages are each the same size and
there are a
number of factors which may have an effect on the size and shape of a cage,
and there
may be variation from cage to cage. Factors which may dictate width of a
welded cage
may include the thickness of the walls, any additional openings in the walls
and the
intersections with other walls, etc.
From a delivery point of view, in some jurisdictions, the welded cages and
beams
may be limited to being no more than 12' wide in one direction, since the
trailers are 8'
wide and the limit for the overhang is 2' on each side. Trailers also come in
different
sizes, and in some jurisdictions, the maximum length may be 60'. Longer or
wider
assemblies than the maximums in a particular jurisdiction are possible with
special
permits and may require heavy duty cranes for positioning and offloading.
Another
factor for the size of welded cages and beams is crane lifting capacity
onsite, since
cages cannot be designed heavier than allowed by the crane lifting capacity,
which may
vary from site to site.
Although the prefabricated welded cages 104 and 404, and the prefabricated
welded beams 204 and 304 are shown with particular arrangements of reinforcing
steel,
it will be understood that various modifications may be made which allow for
the
construction of prefabricated welded components offsite which may be
transported in a
completed form. The welded cages 104 and 404 are preferably made using
vertical
reinforcing bars which are welded inside a plurality of parallel horizontal
continuous ties.
The welded beams 204 and 304 are preferably made using top and bottom beam
layers
which are welded inside a plurality of vertical continuous ties.
The prefabricated beams and cages described herein may be mass produced,
since each component may be fabricated following a specific design.
Although the foregoing description has been made with respect to preferred
embodiments of the present invention it will be understood by those skilled in
the art
CA 02867964 2014-10-16
-13-
that many variations and alterations are possible. Some of these variations
have been
discussed above and others will be apparent to those skilled in the art.
In the claims, the word "comprising" is used in its inclusive sense and does
not
exclude the possibility of other elements being present. The indefinite
article "a/an"
before a claim feature does not exclude more than one of the feature being
present
unless it is clear from the context that only a single element is intended.
