Modular reinforcement cages for ductile concrete frame members and method of fabricating and erecting the same

A generally rectangular wire grid of welded construction is utilized to define and maintain the positioning of rebar charged therethrough during the formation of structural column and girder cages. Pre-positioned ties guide the rebar through the grid. The pre-positioned ties are then tightened such that the rebar is held firmly in place at the close tolerance positions defined by the prefabricated grid. A plurality of such grids are assembled into expandable bundles such that they may be expanded in an accordion-like fashion about rebar charged therethrough, resulting in properly spaced grids for defining and maintaining the position of the rebar. Additional rebar members may then be charged therethrough to complete the construction of a column or girder cage. The modular reinforcement cages of the present invention thus eliminate piecemeal engineering requirements by providing modular building concepts in which a unique rebar bundle pattern facilitates improved containment.

FIELD OF THE INVENTION 
The present invention relates generally to building construction and more 
particularly to a ductile reinforced concrete frame comprising 
prefabricated welded grids for defining and maintaining the position of 
rebar charged therethrough such that high tolerances are maintained, metal 
usage is minimized, and improved structural strength is obtained. 
Ductility is improved, thereby reducing the amount of earthquake resisting 
material required by reducing the seismic forces that the structure must 
resist. The present invention thus provides a unique rebar bundle pattern 
for improved confinement. Modular building concepts eliminate piecemeal 
engineering requirements. 
BACKGROUND OF THE INVENTION 
Frames comprised of reinforced concrete columns and girders for 
constructing buildings are well known. Such contemporary columns and 
girders are commonly constructed by first forming a latticework of rebar, 
i.e., a cage, which reinforces and contains the concrete. The cage, 
generally defining the column or girder, is surrounded by a form, commonly 
constructed of steel or fiberglass. Concrete is then poured into the form 
such that the cage is encapsulated thereby. The concrete is then typically 
vibrated to remove any voids formed therein. The form may be constructed 
in place such that the resulting column or girder need not be moved after 
the concrete cures. Alternatively, the form may be constructed at a 
convenient location, and the column or girder thus fabricated subsequently 
moved to its final location. 
In multi-level commercial buildings, the steel latticeworks or cages for 
such columns and girders are commonly constructed by first disposing a 
plurality of elongate members or rebar upon a series of supports or horses 
and then positioning a plurality of sections of smaller diameter rebar or 
wire formed into generally rectangular hoops about the larger elongate 
rebar members to generally define the desired cage. Further elongate 
members may then be charged through these rectangular hoops and secured in 
position via wire ties. 
As can be appreciated, this process is extremely labor intensive. 
Additionally, very loose tolerances, typically approximately 1/2 inch, are 
maintained due to the difficult nature of handling and aligning such 
materials. Thus, the lateral position of an elongate rebar member at the 
intersection of one rectangular hoop may vary by as much as 1/2 inch 
relative to its position at the intersection of another rectangular hoop. 
Such large tolerances are not desired. They are tolerated by building 
codes because of the present-day method of preforming the hoops and hooked 
cross-ties. 
Typically such columns and girders are formed in thirty foot lengths, which 
are commonly required in building construction. Splice bars are shorter 
lengths, typically approximately sixteen feet, of rebar which are wire 
tied to the abutting ends of adjacent columns such that they may be joined 
thereby. As can be appreciated, such splicing greatly increases material 
usage, weight, and cost as well as requires substantial labor in the 
practice thereof. Column bars are spliced by overlapping their offset 
ends. Girder bars are usually just capped. 
The need for frame structures to exhibit a comparatively high degree of 
ductility is particularly important in geographic locations known to 
experience substantial seismic activity. In such geographic locations it 
is not uncommon for frame structures to experience sufficient force to 
cause crushing or brittle failure of the concrete during seismic activity. 
Such crushing or brittle failure may result in catastrophic failure of the 
structural member. 
For example, a portion of the encapsulating concrete may break away as a 
result of seismic activity. The breaking away of such a portion of the 
encapsulating concrete may then expose a portion of the rebar latticework 
or cage, allowing it to degrade from environmental factors, i.e. moisture, 
smog, etc., and also allowing it to move outward due to the lack of a 
retaining effect provided by the encapsulating concrete. 
Furthermore, rectangular hoops are subject to rupture or breakage upon 
experiencing substantial seismic forces. Such substantial seismic forces 
may urge the rebar restrained by the rectangular hoop outward with 
sufficient force to pull apart the bent ends of the rectangular hoop. 
Columns using cross-ties with 90-degree bends, when subjected to bending 
and axial forces, have exhibited brittle failures caused by the 90-degree 
bends straightening out. Also intermediate longitudinal bars between 
cross-ties buckle outward due to lack of positive confinement, thus 
causing a brittle failure of the concrete. Thus, such construction is 
inadequate for use in geographic locations known to experience substantial 
seismic activity. 
The prior art construction methods are thus labor intensive, require 
excessively large tolerances, utilize 90-degree bends which are failure 
prone, and additionally utilize intermediate bars which tend to buckle 
prematurely. 
As such, although the prior art has recognized, to a limited extent, the 
problem of fabricating structural members such as columns and girders in a 
manner which will withstand substantial seismic forces, the proposed 
solutions have to date been in effective in providing a satisfactory 
remedy. 
SUMMARY OF THE INVENTION 
The present invention specifically addresses and alleviates the above 
mentioned deficiencies associated in the prior art. More particularly, the 
present invention comprises dimensionally stable structural frames 
utilizing generally rectangular wire frames or grids, preferably of welded 
construction, to replace the prier art hoops and to define and accurately 
maintain the positioning of rebar members charged therethrough. 
Pre-positioned ties guide the rebar through each grid. The pre-positioned 
ties are then tightened such that the rebar is held firmly in place at the 
close tolerance positions defined by the prefabricated grid. 
A plurality of such grids may optically be assembled into laterally 
expandable cages or grid bundles such that they may be expanded in an 
accordion like fashion about rebar members charged therethrough. 
Positioner devices, preferably wire loops, define the relative positions 
of the grids once the bundle is expanded. This results in properly spaced 
grids for defining and maintaining the position of the rebar in the 
finished cages. Additional rebar members may then be charged through the 
grid bundles prior to expansion thereof to complete the construction of a 
column or girder cage. Such rebar members are attached to the grids via 
ties, preferably formed of wire. The cage is disposed within a form and 
the form is then filled with concrete to complete the fabrication of a 
column or girder. 
Bundles of grids with positioner devices attached can alternatively be 
expanded first and then have longitudinal rebar members charged 
therethrough, instead of being charged first and then expanded as 
described above. As a further alternative, only key, i.e., two upper 
corner, rebar members are charged through the bundle first. Subsequently, 
the bundle is expanded and then the remaining bars are charged 
therethrough. 
The grids are of integral construction such that they need not be assembled 
at the job site. Thus, each of the individual members of the grid are 
permanently interconnected, i.e., by welding, to one another such that 
interconnection need not be performed by construction personnel. Those 
skilled in the art will recognize that various other means of forming such 
integral grids are likewise suitable. For example, integral grids can be 
formed by forging, molding, machining, the use of bolts or other 
fasteners, etc. 
For certain special applications such as reinforced columns using high 
strength concrete, the grids are made of prewelded elongated hoops of 
paperclip-like configuration positioned at 90-degree orientation to one 
another. Longitudinal reinforcement is charged through the ends of these 
hoops. Grids or hoops could be made of other materials, such as graphite 
pultrusion, etc. 
The use of such prefabricated grids eliminates a substantial portion of the 
labor required in the fabrication of structural members such as columns 
and girders utilized in the construction of building frames. Additionally, 
the high tolerances, typically within approximately 1/16 inch, afforded by 
the use of such prefabricated grids substantially enhances the structural 
strength and ductility of the building frames fabricated therewith and 
additionally reduces the quantity of material required for such 
fabrication. Vastly improved ductility reduces the amount of material 
required to resist earthquake forces in the entire building structure. 
Interconnection modules facilitate the convenient attachment of girders to 
columns to allow rapid charging of splice bars through the girder and 
column cages. A ledge formed along the lower surface of the 
interconnection module provides vertical alignment of the cage attached 
thereto and supports the cage during the attachment process. Alignment 
members facilitate horizontal alignment of the cage by providing an easily 
observable indication of horizontal alignment. Thus, the girder cage or 
precast girder need merely be placed upon the ledge of the interconnection 
module and positioned in alignment with the alignment members to 
facilitate correct alignment thereof, greatly reducing the amount of labor 
involved in the attachment process. 
Rollers positioned upon the interconnection module and/or the prefabricated 
grids of the column cage or girder cage facilitate charging thereof. Such 
rollers both act as guides for charging and also substantially reduce the 
amount of work required by allowing the rebar thus charged to roll 
thereover, thus reducing friction. 
Two types of rollers are disclosed. A first or spool-type of roller 
comprises partitions for separating and properly positioning two or more 
rebar members. Spool-type rollers are attachable to the interconnection 
modules and/or the grids of columns or girders during the fabrication 
process, prior to the completion of welding. Snap-on split-sleeve rollers 
may be attached at any time. Both spool-type and snap-on split-sleeve 
rollers are preferably fabricated of steel. However, those skilled in the 
art will recognize that various other materials, i.e., plastic, are 
likewise suitable. 
The split-ring snap-on rollers may be conveniently attached to the grids of 
columns and girders when and where required. Split-rings snap-on rollers 
are configured as a generally cylindrical sleeves having a split formed 
longitudinally therein such that the sleeve may be pried open by manually 
enlarging the split therein. This allows the sleeve to be positioned upon 
a wire member or the like and the sleeve then closed by bending the split 
shut. 
Use of the spool-type rollers and split-ring snap-on rollers in various 
combinations are contemplated. For example, the spool-type rollers may be 
used at intervals along a column or girder to maintain alignment of the 
rebar charged therethrough during the charging process while split-sleeve 
snap-on rollers are used intermediate adjacent spool-type rollers to 
reduce friction and thereby further improve the charging process. 
Threaded couplings may optionally be used to attach adjacent columns and/or 
girders. The threaded couplings are initially threaded completely onto 
threaded portions of rebar extending from a first structural member. The 
threaded portions of rebar of the first structural member are then aligned 
with corresponding threaded portions of rebar of a second structural 
member such that the threaded portions of rebar abut. The threaded 
couplings are then twisted such that they thread onto the threaded studs 
of the second structural member. When the threaded couplings are 
positioned such that they envelope approximately equal portions of the 
threaded studs of both structural members, attachment is complete. 
A substantial savings in weight is realized in the practice of the present 
invention because the use of the prefabricated grids eliminates a 
substantial portion of the rectangular hoops utilized in the prior art 
construction of the steel latticework. The ends of the hoops, which are 
typically bent inwards about a rebar member, are not present in the grids 
of the present invention. Because of the large number of such rectangular 
hoops utilized in the construction of any given structural member, this 
savings is substantial. Additionally, the welded construction of the grids 
reduces the number of wire ties required. Additionally, the use of high 
strength wire ties for reinforcing the column and girder grids results in 
a substantial weight reduction. 
Strength and ductility is improved since every rebar member is confined 
within a welded corner or welded T intersection of a grid when the cages 
are formed. There are no non-welded or weak corners in the present 
invention which are particularly subject to failure during seismic 
activity. 
Because of the accuracy with which the steel reinforcing lattices of the 
present invention are formed, they do not tend to distort or corkscrew as 
they are being erected. Such distortion or corkscrewing represents a 
substantial problem in the prior art. It makes the fabrication and 
handling processes substantially more difficult and prevents uniform 
construction of the structural members. The resulting rigidity and high 
tolerance construction of the steel latticeworks of the present invention 
therefore substantially enhance and improve the erection process. Thus, 
the erection process requires substantially less time and is consequently 
less costly. 
The prior art, using structural steel columns, is at a disadvantage because 
the structural steel columns resist earthquake forces in only one 
direction. Also, steel anide flange columns have a weak axis which reduces 
their ability to support gravity loads. The present invention, on the 
other hand, allows for the maximum number of principal reinforcement bars 
to be arranged near the four outside edges of the concrete column where 
they will be efficiently resisting both axial gravity and bending moments, 
caused by lateral forces in both orthogonal directions. At the same time 
the present invention allows the girder bars to pass through the column in 
a modular configuration. 
By using bundled bars in both the column cage and the girder cage, the 
present invention provides a modular way to arrange reinforcement bars so 
that they can pass each other very efficiently in a four-way column-girder 
joint. 
At the same time the rebar arrangement provides for confinement of every 
rebar member, which is not the case in the prior art. 
This positive confinement of every column and girder rebar member is 
achieved and the closely spaced orthogonally oriented high strength wires 
in the column and girder grids are ideally positioned to resist the 
bursting forces created in the joint which cause brittle failures of 
reinforced concrete joints. 
The configuration of the present invention provides for the equivalent of 
an external hydrostatic pressure of several thousand psi. This new pattern 
of intersecting vertical and horizontal bars confined with orthogonally 
oriented high strength wires at very close spacing creates a new type of 
concrete frame which will allow the safe use of reinforced concrete in 
much taller buildings in seismic zones. At the same time, by automating 
the fabrication and erection of these highly ductile concrete frames, the 
cost of these tall buildings will be substantially less while their 
resistance to earthquakes will be substantially greater. This new pattern 
of reinforcement and confinement thus allows much stronger frames to be 
constructed whose members are significantly smaller in dimension. 
Thus, for taller buildings, less rentable space is lost to columns and 
girders in the present invention. In addition, because of the vastly 
increased ductility of this new kind of concrete frame, much less 
principal reinforcing steel and concrete in both columns and girders is 
required. This, in turn, reduces the dead weight of the building which 
further reduces the lateral earthquake forces and gravity loads. 
Thus, the present invention has a three-fold advantage over prior art in 
both concrete and structural steel. The first is that rebar pattern allows 
for more reinforcement in smaller members. The second is that vertical and 
horizontal rebar members pass through the joint in an efficient modular 
way which makes erection much faster. The third is that the present column 
rebar pattern allows the column to resist lateral forces from both 
orthogonal directions, while at the same time resisting axial forces more 
efficiently even though it is smaller. 
These standard modular columns and girder cages are all predesigned to fit 
together without interference while erecting. Also these standard modular 
columns and girders will best tested so that each has a known ductility 
ratio and known capacity. 
During computerized analysis and design, the standard modular girder cage 
and column cage pattern is selected for each member based on its 
previously tested ultimate capacity. Computerized shop drawings, including 
bill of materials, may be prepared using the standard modular patterns of 
intersecting girder and column reinforcement and of the adjustable forms. 
A complete computerized material take-off and labor or equipment estimate 
can then be prepared using the information generated during preparation of 
the shop drawings. 
Computerized fabrication of the grids and principal reinforcement with ends 
offset can be accomplished. Computerized fabrication or joint cubes and 
grid bundles can then be performed as the final operation in the shop. In 
the field or in the shop, a computerized cage assembly machine can 
assemble the cages. 
The modular reinforcement cages for ductile concrete frame member of the 
present invention thus provide a unique rebar bundle pattern for improved 
confinement. This results in structural members which are less susceptible 
to the forces generated by earthquakes. 
A building structure utilizing the present invention can be safely designed 
and constructed with approximately half the amount of earthquake resisting 
material than is required in the prior art, which does not have the 
ability to have the core concrete strained without battle failure. 
Furthermore, the improved dimensional tolerance and standardized 
construction techniques facilitated by the present invention lend the 
structural members formed thereby to the use of automation, i.e. robotics. 
Thus, the present invention both represents a substantial advance in the 
art and facilitates such further advances. 
These, as well as other advantages of the present invention will be more 
apparent from the following description and drawings. It is understood 
that changes in the specific structure shown and described may be made 
within the scope of the claims without departing from the spirit of the 
invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The detailed description set forth below in connection with the appended 
drawings is intended as a description of the presently preferred 
embodiment of the invention, and is not intended to represent the only 
form in which the present invention may be constructed or utilized. The 
description sets forth the functions and sequence of steps for 
constructing and operating the invention in connection with the 
illustrated embodiment. It is to be understood, however, that the same or 
equivalent functions and sequences may be accomplished by different 
embodiments that are also intended to be encompassed within the spirit and 
scope of the invention. 
The ductile frame of the present invention is illustrated in FIGS. 2-19 
which depict a presently preferred embodiment of the invention. FIGS. 1a 
and 1b depict devices utilized according to prior art construction 
methodology. 
Referring now to FIG. 1a, a prior art rectangular hoop 10 is formed from a 
section of rebar such that it has four sides 12, 14, 16, and 18, and is 
generally configured as a rectangle. The rectangular hoop has corners 22, 
24, 26, and 28. The ends 20 and 21 of sides 12 and 18, respectively, are 
bent inward such that they may be disposed about either side of a rebar 
member (31 in FIG. 1b) charged through the rectangular hoop 10 and 
positioned at the corner 22 thereof. 
Referring now to FIG. 1b, the prior art construction of a column or girder 
cage is illustrated. Two rectangular hoops 10 are disposed about ten rebar 
members 11, 30, and 31 such that the rebar members 11, 30, and 31 are 
captured and contained within the rectangular hoops 10. As is well known 
to those skilled in the art, a plurality of such rectangular hoops 10 
charged with rebar members 11, 30, and 31 thus form a latticework or cage 
about which concrete is poured to form the desired structural member. 
Intermediate rebar members 11 are not confined at a corner and are 
consequently more subject to moving due to this lack of containment than 
are rebar members 30 and 31. 
Referring now to FIG. 2, a generally square column grid 40 of the present 
invention is illustrated. The column grid 40 comprises a plurality, i.e. 
four, of first or longitudinal wire members 42 disposed perpendicularly to 
a like plurality of second or transverse wire members 44 such that 
intersections 66, preferably welded joints, are formed. The first 42 and 
second 44 wire members thus generally define a square. That is, the 
longitudinal 42 and transverse 44 wire members form plural orthogonal 
cells. The total area of the grid 40 is approximately equal to, i.e., 
slightly less than, the cross-sectional area of the structural member, 
i.e. girder, to be fabricated therefrom. 
Disposed at a substantial number, preferably all, of the interior corners 
formed by the intersections 66 of the longitudinal 42 and transverse 44 
wire members are pre-positioned ties 46, preferably formed of wire. Those 
skilled in the art will recognize that other materials, i.e. plastic, 
string, cord, tie wraps, perforated plastic ties, etc., are likewise 
suitable. During the charging process these pre-positioned ties 46 define 
apertures through which rebar members are charged. After the charging 
process, these ties 46 firmly secure the charged rebar members in place. 
Each pre-positioned tie 46 is firmly attached at one end thereof to a wire 
member 44 or 42. Those skilled in the art will recognize that various 
means, e.g. welding, hot glue, etc., are suitable for attaching the ties 
46 to the wire members 42 and 44. The other end of each tie 46 is disposed 
proximate an intersecting wire member 42 or 44 such that after charging, 
the wire tie may be tightened about the captured rebar member. 
The use of such ties 46 with a prefabricated grid 40 make possible high 
tolerances, i.e., approximately 1/16 inch, in the positioning of the rebar 
members charged therethrough. Such close tolerance positioning of the 
rebar charged through the grids 40 minimizes metal usage, improves 
structural strength, and reduces the amount of time and labor required to 
form the structural members. 
The uniformly constant confinement provided by the present invention's 
tight tolerance fabrication gives the reinforced concrete member much 
greater ductility than is present in the prior art. These consistently 
exact dimensions improve the reliability of the reinforced concrete 
structure and permit it to withstand violent earthquake forces. 
The more exact dimensions of the grids of the present invention provide for 
the use of automated fabrication and assembly methods. They thus reduce 
the time required for erection, as well as for the connection of the cages 
and precast members of the present invention. 
The increase ductility of the structural members of the present invention 
makes them more resistant to lateral seismic forces. Thus, the members can 
be constructed utilizing significantly less concrete and steel while 
maintaining the same earthquake resistance. 
Referring now to FIG. 3, a generally rectangular grid 60 for use in the 
formation of girders 130 (best shown is FIGS. 10 and 15) of the present 
invention is illustrated. The girder grid 60 comprises a plurality, i.e., 
three, first or vertical wire members 62 disposed perpendicularly to a 
plurality, i.e., four, of second or horizontal members 64. As in the 
column grids 40, pre-positioned wire ties 46 are formed at the interior 
corners of intersecting wire members 62 and 64 and provide like benefits. 
Referring now to FIG. 3a, the intersection 66 of two wire members 62 and 64 
having a pre-positioned tie 46 attached thereto is illustrated. A weld 
joint preferably interconnects the two wire members 62 and 64. Such welded 
construction is preferably utilized in both the column grids 40 of FIG. 2 
and the girder grids 60 of FIG. 3, because of the high strength union 
formed thereby. Alternatively, the column 40 and girder 60 grids may be 
formed by molding, machining, utilizing fasteners, or forging. Those 
skilled in the art will recognize that various other materials and methods 
of forming prefabricated integral, one-piece, grids are likewise suitable. 
An assembly fixture is utilized to hold the longitudinal 42 and transverse 
46 wire members of the column grid 40 or the vertical members 62 and 
horizontal members 64 of the girder grid 60 in position while the wire 
members 42 and 46 or 62 and 64 are interconnected and/or the ties 46 are 
attached thereto. 
A substantial savings in weight is realized in the practice of the present 
invention because use of the prefabricated column 40 and girder 60 grids 
eliminates the ends 20 and 21 of the rectangular hoops 10 (as shown in 
FIGS. 1 and 2) which are present in the prior art. Because of the large 
number of such rectangular hoops 10 utilized in the construction of any 
given structural member, this savings is indeed substantial. Labor is also 
saved by reducing the number of pieces that the worker must install. 
The elimination of the ends 20 and 21 of the prior art rectangular hoops 10 
facilitates passage of the wet concrete through the grids of the present 
invention. It also enhances the vibration process such that voids are 
better eliminated in the present invention. Thus, concrete flow is 
improved and the integrity of the structural member is enhanced. More 
rebar can be used in smaller members without inhibiting the pouring and 
vibrating of the wet concrete. Thus, smaller members have greater weight 
bearing capacity. 
Strength is improved since every rebar member is confined within a welded 
corner or welded T intersection of the grid. There is no non-welded or 
weak corner which is particularly subject to failure during seismic 
activity. 
Because of the accuracy and rigidity with which the steel reinforcing 
lattices or cages of the present invention are formed, they do not tend to 
distort or corkscrew as they are being erected. The resulting rigidity and 
high tolerance construction of the steel cages therefore substantially 
enhances and improves the erection process. Thus, the erection process 
requires less time and is consequently less costly. 
Referring now to FIG. 4, an interconnection module 80 is illustrated. The 
interconnection module 80 comprises a plurality of first 82 and second 84 
perpendicularly intersecting horizontal wire members, preferably defining 
prefabricated grids. The intersecting first 82 and second 84 wire members 
define a plurality of separate planes which are interconnected via a 
plurality of third or vertical members 86. Three alignment members 88 are 
preferably positioned vertically upon each vertical face of the 
interconnection module 80 to define the position at which a girder is 
attachable. An angle bracket 90 having upper 92 and lower 94 perpendicular 
edges is attached at the lowermost portion of each of the four vertical 
faces of the intersection module 80 to facilitate abutting attachment of 
girders thereto. Adjacent angle brackets, i.e., those on adjacent faces of 
the interconnection module are preferably formed at different heights or 
offsets relative to one another. These offsets prevent the rebar members 
of perpendicularly intersecting girders from interfering with each other. 
Thus, a girder cage 130 (FIG. 10) may be attached to a column cage 150 
(FIG. 9) having an intersection module 80 formed thereon by positioning 
one edge of the girder cage 130 upon the lower edge 94 of the angle 
bracket 90 and aligning the girder cage 130 with the alignment members 88. 
Alignment of the vertical wire members 62 of the girder cage 130 with the 
vertical alignment members 88 of the interconnection module 80 is thus 
attained. Ties may then be utilized to connect the girder cage 130 to the 
interconnection module 80. The weight of the girder cage 130 may be 
supported by the angle bracket 90 during the attachment process. 
Attachment of the girder 130 to the column having the interconnection 
module 80 formed thereon is further accomplished by extending splice 
sections of rebar along the girder rebar members charged through the 
column girder 130 and attaching the splice sections of rebar thereto, 
generally via ties, preferably wire ties. Girder rebar splice bars are 
changed horizontally through the column cage 150. The girder splice bars 
are tied to the girder cage bars. A minimum of eight feet of splice rebar 
is generally desired within the girder cage 130 being attached to the 
column cage 150. 
Splice member overlap length reduction is achieved due to better 
confinement. Because of the uniform confinement among the full length of 
the splice, tests have shown that the required lap length is much less 
than that required by code. Consequently shorter overlaps save a 
substantial amount of reinforcement steel. If an opposing girder cage 130 
is attached to the interconnection module 80, then the splice sections of 
rebar extend through the interconnection module 80 such that they are 
attached to both opposing girder cages 130. 
Referring now to FIG. 4a, the welded interconnection 85 of the first 82, 
second 84, and third 86 rebar members is illustrated. Welded construction 
is preferred, although those skilled in the art will recognize that 
various other methods are likewise suitable. 
Referring now to FIGS. 5 and 5a, an expandable cage or grid bundle 100 is 
comprised of a plurality of individual column grids 40. The grids 40 are 
attached together via loops 102 disposed about adjacent rebar members, 
i.e. adjacent horizontal wire members 44 and/or adjacent vertical rebar 
members 42. The loops 102 limit the expansion of the wire cage 100 and 
define the final positions of the grids 40. The grids 40 preferably expand 
such that adjacent grids are approximately three inches apart after 
expansion. Similar construction is utilized in fabrication of an 
expandable cage or grid bundle comprised of girder grids 60. The loops 102 
are preferably comprised of steel, however, those skilled in the art will 
recognize that various other materials, e.g. copper, aluminum, plastic, 
rope, fabric, etc., are likewise suitable. Additionally, tie wraps and/or 
perforated plastic wraps may be utilized as the loops 102. 
The column grids 40 (as well as the girder grids 60) can be configured such 
that they may be nested for storage and transportation. Nesting allows 
each grid to be positioned as close as possible to adjacent grids, such 
that a compact assembly is formed. To nest the column grids 40, for 
example, every other column grid 40 is turned around such that the first 
wire members 42, for example, are disposed next to each other, i.e., one 
above and one below. Thus, for each such turned grid, the length of the 
assembly is reduced by the diameter of the wire member 42 and space is 
correspondingly conserved. 
The entire expandable cage or grid bundle, whether in a nested 
configuration or not, is preferably shrink-wrapped to facilitate handling. 
Shrink wrapping envelopes the grid bundle with plastic to prevent movement 
of the grids relative to one another during shipping and handling, as well 
as during the cage assembly process. 
Referring now to FIGS. 6, 6a, and 6b, a horse 110 supports upper elongate 
rebar sections 112. Lower rebar sections 113 may be supported, as 
required. The horse comprises parallel base bars 210 which extend the 
distance of the structural member to be formed thereupon, vertical support 
bars 212, and cross members 214 adjustably attached to the vertical 
support members 212. Base cross members 218 interconnect the base members 
210. 
With particular reference to FIG. 6a, the height of each cross member 214 
can be varied by loosening adjustable fittings 216 and sliding the cross 
member 214 up or down as desired. Retightening the adjustable fitting 216 
firmly secures the cross member 214 in place. 
With particular reference to FIG. 6b, adjustable support 220 comprising 
support surface 222 disposed atop adjustable vertical support members 224 
and attached to cross member 226 may be utilized to support the 
interconnection modules 80. As with the adjustable cross members 214, the 
height of the support surface 222 is adjustable via adjustment couplings 
228. 
Adjacent interconnection modules 80 are preferably spaced approximately 
three feet six inches apart. Such horses 110 are utilized to support 
sections of rebar during the charging process wherein columns and girders 
are formed according to both the prior art and present invention. 
Referring now to FIGS. 7 and 8, horses 110 are illustrated supporting two 
elongate rebar sections 112, preferably formed of #11 rebar. Those skilled 
in the art will recognize that various other sizes of rebar may likewise 
be suitable. A plurality of expandable grids 100, preferably still 
shrink-wrapped, depend from the rebar sections 112. Similarly, a plurality 
of interconnection modules 80 depend from the rebar sections 112. Each 
interconnection module 80 is preferably further supported by a support 220 
(FIG. 6b). The expandable bundles 100 expand to fill the distance between 
interconnection modules 80 in the manner illustrated in FIG. 5a. Columns 
up to sixty feet in height, the standard uncut length of rebar as 
purchased from the mill, can easily be fabricated utilizing the process of 
the present invention. 
With particular reference to FIG. 8, the charging process is illustrated. 
During charging, a plurality of additional elongate rebar sections 116, 
preferably likewise formed of #11 rebar, are pushed through the openings 
of the expandable cages or grid bundles 100 and interconnection modules 
80. Charging is preferably performed with the grid bundles 100 still 
shrink-wrapped. By charging the grid bundles 100 while they are still 
shrink wrapped, the individual grids comprising the bundles are maintained 
in a desired, i.e. collapsed or nonexpanded, configuration which 
facilitates their handling and thus makes the charging process easier. 
This is accomplished by pushing the rebar sections 112 and 116 through the 
plastic shrink wrap. The shrink wrap is removed prior to expanding the 
grid bundle 100. 
Each of the elongate rebar sections 112 and 116 pass through the ties 46 of 
the individual grids 40 comprising the grid bundle 100. The ties 46 are 
tightened after expanding the expandable grid bundle 100 to securely 
attach the individual grids 40 to the charged rebar members 112 and 116. 
Interconnection modules 80 are similarly attached at the desired locations 
along the charged rebar sections. 
After a steel reinforcing cage is formed as described above, forms, 
typically comprised of fiberglass or steel, are secured about the 
latticework or cage and concrete is then poured into the forms. As in 
prior art structural member construction, the concrete substantially 
encapsulates the steel cage. Although the fabrication of a column cage 
according to the method of the present invention is described above, the 
method of fabricating a girder cage is an analogous process wherein girder 
grids 60 are substituted for the column grids 40. 
After pouring the concrete into the form, it is typically vibrated to 
minimize voids or air pockets formed therein during the pouring process. 
Use of the column grids 40 or girder grids 60 of the present invention 
enhance both the pouring and void elimination processes. Pouring is 
facilitated by eliminating extraneous protuberances which would otherwise 
inhibit the flow of concrete through the steel latticework of the cage. 
The locked ends 20 and 21 of the rectangular hoops 10 (shown in FIGS. 1a 
and 1b) are eliminated. Theses superfluous members represent a substantial 
impedance to the flow of concrete through the steel latticework due to 
their large number. Furthermore, the amount of steel utilized in wire ties 
is reduced both by maximizing the efficiency of the attachment process 
through the use of pre-positioned wire ties 46 and by utilizing 
prefabricated column 40 and girder 60 grids. The vibration or void 
elimination process is likewise enhanced through the elimination of 
superfluous steel since such protruding steel both contributes to the 
formation of voids and inhibits their elimination. 
Referring now to FIG. 9, an interconnection module 80 having a plurality of 
elongate rebar sections 112 and 116 charged therethrough is illustrated. 
As can be seen, the rebar sections 112 and 116 extend through the openings 
in the interconnection module 80. The interconnection module 80 may be 
secured to the elongate rebar members 112 and 116 via ties. Those skilled 
in the art will recognize that various other means, i.e. welding, for 
securing the interconnection module 80 to the rebar members 112 and 116 
are likewise suitable. 
Referring now to FIGS. 10-13, a girder cage 130 constructed according to 
the present invention is illustrated. The girder generally comprises a 
plurality of rebar members 132, preferably #11, charged through a 
plurality of girder grids 60, at the corners thereof. Additionally, rebar 
members 133 are charged intermediate the corner rebar members 132. 
Additionally, cross members 134 and spool-type rollers 136 (best shown in 
FIG. 12) may optionally be provided to improve the charging process. The 
cross members 134 are welded at the appropriate heights along selected 
vertical rebar members 62 of girder grids 60 to provide proper support for 
the rebar members 132 charged therethrough. Rollers 136 are comprised of 
first 138 and second 140 rebar supporting portions, each disposed outboard 
of corresponding partitions 142. The partitions 142 maintain positioning 
of the associated rebar sections 132. The spool-type rollers 136 
preferably comprise a metal material, i.e. steel, although they may 
alternatively comprise a plastic material, preferably a low-friction 
plastic material such as TEFLON (a registered trademark of Du Pont de 
Nemours, E. I., & Co., Inc.). Those skilled in the art will recognize that 
various other materials are likewise suitable. Ties 46 secure elongate 
rebar sections 132 in position after they have been charged through the 
girder grids 60. 
Referring now to FIG. 14, a column cage 150, such as that being assembled 
in FIGS. 7 and 8, is being positioned by crane 152. The expandable grid 
bundles 100 have been expanded and secured in position via ties 46. The 
interconnecting modules have likewise been secured in position with ties 
46. If concrete is applied prior to erection, then rebar couplers, as 
shown in FIGS. 18 and 19, must be used to connect column section to column 
section and girders to columns. 
Referring now to FIG. 15, a ductile frame 160 is comprised of columns 150 
and girders 130. The girders 130 are attached to the columns 150 at 
interconnection modules 80. Distance "A" between adjacent girders is 
preferably approximately thirteen feet and distance "B" between adjacent 
columns is preferably approximately 30 feet. When a tall building must 
accommodate below-grade parking, columns must be spaced at approximately 
thirty feet on center in both directions. 
Referring now to FIGS. 16, 17, and 17a, the steel structures or lattices 
associated with the interconnection of girders 130 and columns 150 are 
illustrated. Split-sleeve snap-on rollers 180 (as best shown in FIG. 17a) 
may optionally be installed upon any rebar members having other rebar 
members charged thereover to facilitate such charging. Such split-sleeve 
snap-on rollers preferably comprise a metal material, such as steel. 
However, they may alternatively comprise a plastic material, such as 
TEFLON. Those skilled in the art will recognize that various other 
materials are likewise suitable. 
The split-sleeve snap-on roller is preferably configured such that the 
split 181 may be pried apart or opened sufficiently to facilitate 
attachment thereof to a rebar member or the like. Thus, such split-sleeve 
snap-on rollers are disposable upon preformed column grids 40, and 
interconnection modules 80 in order to facilitate the charging of rebar 
members therethrough. 
Splice rebar members 182 interconnect opposing girders 130. The splice 
rebar members 182 are disposed parallel to and adjacent the rebar members 
132 comprising the girder cage. The splice rebar members 182 are attached 
to the rebar members 132 of the girder cages via ties. Those skilled in 
the art will recognize that various other means of attaching the splice 
rebar members 182 to the girder rebar members 132 are likewise suitable. 
The rebar members 116 of the column 150 further comprise tapered portions 
such that they may readily interconnect to additional column rebar cage 
members 190 for attachment thereto. Each attachment may be accomplished 
via ties. Those skilled in the art will recognize that various other means 
for attachment are likewise suitable. 
Referring now to FIGS. 18 and 19, the use of a threaded coupling 170 to 
interconnect columns and/or girders is illustrated. The threaded coupling 
170 is initially threaded completely onto first threaded rebar members 172 
which are partially embedded within a column 150 or a girder 130. 
Complimentary second threaded studs 174 are positioned in alignment and 
abutting relation to the first threaded studs 172 upon which the threaded 
couplings 170 are attached. The threaded couplings 170 are then unthreaded 
partially from the first threaded studs 172 such that they thread upon the 
complimentary second threaded studs 174, thereby interconnecting the first 
threaded studs 172 and the complimentary second threaded studs 174. The 
threaded couplings may optionally comprise a ductile material or mechanism 
to facilitate minor relative motion between the columns and/or girders 
joined thereby. 
It is understood that the exemplary ductile frame described herein and 
shown in the drawings represents only a presently preferred embodiment of 
the invention. Indeed, various modifications and additions may be made to 
such embodiment without departing from the spirit and scope of the 
invention. For example, the grids may be comprised of various materials 
and formed by various processes which provide a high strength, integral 
construction. Also, members other than contemporary rebar, i.e. angle 
iron, square tubing, etc., may be utilized in the construction of the 
present invention. Furthermore, the grids need not be rectangular in 
shape, but rather need only conform generally in shape to the 
cross-section of the structural member being fabricated therewith. 
Additionally, those skilled in the art will recognize that stay-in-place 
forms may be utilized in the construction of columns, beams, and similar 
construction members according to the present invention. The structures 
and methodology of the present invention need not be limited to use in the 
fabrication of columns and girders. Rather, those skilled in the art will 
recognize that the structures and methodology of the present invention may 
be utilized in the construction of various other structural members as 
well. Thus, these and other modifications and additions may be obvious to 
those skilled in the art and may be implemented to adapt the present 
invention for use in a variety of different applications.