Pipe reinforcing fabric

The specification discloses fabric for use in reinforcing concrete pipe. The fabric includes a plurality of circumferential defining line strands and a plurality of transverse strands positioned in spaced, parallel relationship to each other and extending generally perpendicular to the circumferential defining line strands. The transverse strands are divided into a plurality of sets having lengths equal to the predetermined reinforcement cage circumference. The circumferential defining line strands are divided along their lengths into quadrant defining portions. Additional reinforcement is provided at the quadrants wherein the areas of maximum stress will occur in the concrete pipe. The reinforcement may take the form of additional circumferential strands secured to the circumferential or transverse defining strands, a separate quadrant mat or fabric segment secured to the fabric, or the circumferential defining line strands may have an increased diameter at the desired quadrants in order to increase the steel area of the cage in the area of maximum stress that occur in the concrete pipe.

BACKGROUND OF THE INVENTION 
This invention relates to a wire fabric used in the reinforcement of 
concrete pipes. 
Various forms of wire fabric have been proposed which upon fabrication into 
a cylindrical cage or elliptical cage shape are employed to reinforce 
concrete pipe. These fabrics generally include a plurality of transverse 
wire strands and a plurality of circumferential defining line strands. The 
fabric is typically provided to the pipe manufacturer by the fabric 
manufacturer in the form of a continuous roll or in sheets manufactured to 
size. The transverse strands have generally been spaced at 6, 8 or 12 inch 
intervals and when fabric is supplied in a continuous roll the pipe 
manufacturer has had to count the number of transverse wires to determine 
the correct length for a predetermined size of pipe. The fabric must then 
be cut, formed into a circular or elliptical cage and the ends of 
circumferential line strands of the fabric overlapped and secured together 
as by welding. 
This procedure has resulted in a substantial amount of wasted fabric and 
increased fabrication time and cost due to the necessity of counting the 
transverse wires or spacings, required to yield a particular length of 
fabric for a predetermined cage for the pipe size. The spacing between the 
transverse wires or strands most generally yields a fabric length greater 
than the fabric length required for the circumference of the pipe 
reinforcing cage. Many of these problems have been alleviated by the wire 
fabric disclosed in U.S. Pat. No. 3,990,480, entitled METHOD AND FABRIC 
FOR MAKING REINFORCING CAGES, and filed on Jan. 20, 1975 by Wilbur E. 
Tolliver and Daniel J. Borodin. The disclosed fabric therein is divided 
into sets of transverse strands with each set separated by a space smaller 
than the spacing of transverse strands within each set. This results in a 
readily discernable severance or cut line for the shear operator and 
eliminates the necessity of counting transverse strands or spacing, to 
yield a length of fabric required for the predetermined pipe size. The 
fabric is made so that each set has a length corresponding to the 
circumference of the predetermined pipe size, for example. This fabric and 
method of making and using same substantially reduces the waste of the 
fabric from that heretofore experienced as well as increasing the 
efficiency of wire cage production. 
Additional problems, however, are presented which are not solved by this 
fabric. For example, reinforcement requirements of certain classes of 
concrete pipe can best be furnished by including additional reinforcement 
or steel area at the quadrants of the cage wherein the maximum stresses in 
the concrete pipe occur. On the inside reinforcement cage the maximum 
stresses occur at the crown and the invert of the pipe and on the outside 
reinforcement cage at the spring lines of the pipe. Additional steel area 
is required in the quadrants which include the points of maximum stress. 
This additional reinforcement has generally been provided by cutting the 
predetermined fabric lengths, rolling or forming the fabric into a 
reinforcing cage, connecting the ends of the cut fabric and then tack 
welding properly dimensioned fabric mats or quadrant mats to the cage at 
the quadrants where additional steel reinforcement is required. 
Also, it is sometimes advantageous or required to provide additional 
reinforcement in the form of stirrups at the point of maximum stress at 
the pipe crown and invert. The stirrups are projections, which when 
secured to the fabric in the areas of the maximum stress quadrants, extend 
radially outwardly from the cage. The stirrups have typically been 
attached to the fabricated pipe reinforcing cage resulting in the need for 
substantial more labor to complete the cage. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a unique wire fabric and method 
of using same is provided whereby a complete reinforcing cage including 
the required quadrant reinforcement at the areas of maximum stress may be 
formed in the field by the pipe manufacturer merely by cutting off lengths 
of a roll of the fabric or by using sheets of fabric, forming the cut 
fabric or fabric sheet into a cylindrical or elliptical cage and joining 
the ends of the fabric. In roll form, the wire fabric includes a plurality 
of circumferential defining line strands and a plurality of transverse 
strands positioned in spaced, parallel relationship to each other and 
extending generally perpendicular to the circumferential defining line 
strands. The transverse strands are divided into a plurality of sets with 
each set being spaced from an adjacent set along the circumferential 
defining line strands a distance less than the spacing of the transverse 
strands within each set to thereby define readily discernable cut lines. 
In either roll form or sheet form, provision is made for increasing the 
steel area in the direction of the circumferential defining line strands 
in predetermined areas which will subsequently become located within the 
pipe wall at the quadrants of maximum stress when the fabric is cut and 
formed into a reinforcing cage. The transverse strands may be spaced in 
the maximum stress quadrants a distance equal to that required for use of 
stirrup reinforcement or to a predetermined distance. In the remaining two 
quadrants, the spacing of the transverse strands may be increased to that 
required for supporting the circumferential defining line strands or to a 
predetermined distance equal to or greater than the spacing at point of 
maximum stress. 
As a result, a fabric is provided which is readily cut into predetermined 
lengths or is manufactured as sheets, which includes all necessary 
reinforcement and which requires only that the ends of the cut fabric or 
fabric sheet be joined. The fabric permits pre-attachment of stirrups 
during fabric manufacture to transverse strands which are already laid to 
mark the spacing required for the stirrups. The fabric and method for 
making and using same therefore reduces the reinforcing cage fabrication 
time, cost and difficulty; eliminates wasteful use of fabric; and results 
in substantial savings in steel material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In the embodiment illustrated in FIG. 1, the fabric 10 includes a plurality 
of longitudinal or circumferential defining line strands 12 and a 
plurality of transverse strands 14. These strands are interconnected such 
as by conventional welding operations and further are oriented at right 
angles to one another. The circumferential defining line strands 12 are 
spaced from each other at substantially equal intervals and extend 
parallel to each other. The transverse strands 14, however, are arranged 
in sets with some visible designation between sets to tell an operator or 
an automatic machine where the fabric should be cut. Preferably, the last 
strand 14b of each set is spaced from the first strand 14a of the next 
adjacent set by a distance which is just sufficiently great to allow the 
fabric to be cut between the sets. Typically, the spacing between the last 
strand of one set and the first strand of the next adjacent set would be 
approximately two to three inches. This spacing is less than the spacing 
between the transverse strands 14 within a particular set so as to define 
readily discernable cut or severance lines. Further, the distance along 
the circumferential defining line strands between the first and last 
strands of each transverse set corresponds to a reinforcing cage 
circumference for a predetermined class and size of concrete pipe. During 
the manufacture of the fabric, the line strands are divided longitudinally 
into preselected portions a, b, c, d, and e. Portion a has a length 
corresponding to one-eighth of the total length of the transverse set. 
Portions b, c, and d have lengths corresponding to one-fourth the length 
of the transverse set and portion e has a length corresponding to 
one-eighth of the length of the transverse set. As will be more fully 
described below, portions b and d correspond to the areas of maximum 
stress in the concrete pipe for which the subsequently formed reinforcing 
cage will be employed. 
In the alternative, the fabric can be shipped in sheets made to appropriate 
length. This eliminates yet another step for the pipe producer. 
In the manufacture of certain sizes and classes of reinforced concrete 
pipe, it is desirable that these areas of maximum stress be provided with 
additional reinforcement when compared to the areas of minimum stress. 
Applicable concrete pipe standards require that the steel area in these 
areas be increased. The steel area is defined as the sum of the 
cross-sectional areas of the strands which are circumferential defining 
line strands. Heretofore, the increased steel area required in the areas 
of maximum stress has been obtained by forming the reinforcing cage from 
the fabric and then tacking to the preselected portions of the cage 
reinforcement mats or quadrant mats which have first been rolled into an 
arcuate configuration. In accordance with the present invention, these 
additional fabrication steps by the pipe manufacturer are eliminated. As 
best seen in FIGS. 1 and 2, quadrant reinforcing mats 20 including 
quadrant transverse strands 22 and quadrant line strands 24 are integrally 
secured to areas b and d of each transverse set during the fabric 
manufacturing process. As seen in FIG. 2, the transverse strands 22 of the 
quadrant mat are welded to the circumferential defining strands 12 of the 
fabric. In the alternative, the line strands 24 may be welded to the 
transverse strands 14 of the fabric, or both may be done. 
The transverse strands 22 of the quadrant mat are spaced to accommodate 
reinforcing stirrups 30 schematically illustrated in FIG. 3. These 
reinforcing stirrups may be of the type disclosed in U.S. Pat. No. 
3,840,054 entitled STIRRUP FABRIC PIPE REINFORCEMENT and issued on Oct. 8, 
1974 to Wilbur E. Tolliver, the inventor of the present invention. The 
stirrups are employed to provide additional reinforcement at the areas of 
maximum stress with certain classes and sizes of concrete pipe. The 
stirrups may be hingedly secured to the transverse strands of the quadrant 
mats and placed in a foled position. With the fabric illustrated in FIG. 
1, the spacing between the transverse strands 14 may be made uniform and 
set so as to merely support the circumferential defining line strands 
since the spacing between the transverse strands of the quadrant mats is 
made to accommodate the stirrup reinforcement. 
When the resulting fabric is unrolled and the sets of transverse strands 
are cut into cage forming sections, they may be rolled into the cages and 
then the stirrups may be erected. 
As best seen in FIG. 3, the pipe manufacturer will sever the fabric at the 
readily discernable cut lines and roll the fabric into an elliptical or 
circular cylindrical reinforcing cage. When a single elliptical 
reinforcement cage is employed, or in an inside cage of a two cage 
assembly, the maximum stress will occur at the crown 32 and at the invert 
34 of the pipe and cage. The minimum stress will occur at the spring line 
36 of the pipe and cage. The quadrant reinforcement including the 
reinforcing stirrups will extend through an arc of 60.degree.-90.degree.. 
This arc area of the cage therefore, includes the areas of maximum stress 
of the concrete pipe reinforced by the fabric. Once the fabric has been 
severed or cut into the required sets or sections, the pipe manufacturer 
need only roll it into the predetermined cage shape and weld or otherwise 
secure the ends of the fabric together at the spring lines or point of 
minimum stress of the cage with transverse strands 14a and 14b closely 
adjacent one another. Therefore, the fabric illustrated in FIGS. 1 and 2 
substantially reduces the time consuming fabrication steps, results in a 
decrease in the amount of wasted fabric and the required quadrant 
reinforcement for particular size and class of pipe is provided without 
any additional steps by the pipe manufacturer. 
In the alternative embodiment illustrated in FIG. 4, the quadrant 
reinforcement is provided by joining a plurality of reinforcing strands 40 
to the fabric 10 at the preselected portions which correspond to the areas 
of maximum stress in the completed concrete pipe. The reinforcing strands 
40 are positioned on the fabric and extend parallel to the circumferential 
defining line strands 12. In this embodiment, the reinforcing strands 40 
are joined to the transverse strands 14 of the fabric, preferably on the 
same side as circumferential strands 12. This is a more preferable 
embodiment of the invention as compared to the FIGS. 1-3 embodiment in 
that this fabric would be easier to roll form than the FIGS. 1-3 
embodiment with this embodiment fabric, the roll formers would never have 
to roll over more than two thicknesses of wire whereas in the FIGS. 1-3 
embodiment, the formers have to roll over three thicknesses of wire at the 
quadrant areas. Further, with this embodiment the spacing between the 
transverse strands 14e which are positioned within the preselected 
portions of the set are spaced differently from the transverse strands 14 
outside of the preselected portions (strands 14, 14a, 14b and 14e lying in 
a common plane). It is preferred that the transverse strands 14e within 
these portions be spaced closer together in order to accommodate the 
stirrup reinforcement or for better mechanical anchoring ability. 
Typically, this spacing will be at approximately 4 or 6 inch intervals. 
Outside of this reinforced area, the transverse strands 14 may be spaced a 
greater distance which is sufficient to support the circumferential 
defining line strands 12. This feature results in a substantial savings in 
material and the fabrication of a fabric designed to accommodate the 
stirrup reinforcement. 
The embodiment illustrated in FIG. 5 is similar to that shown in FIG. 4 
except that the reinforcing strands 40 are joined to the fabric 10 by 
welding them to the circumferential defining line strands 12 of the fabric 
10. The circumferential defining line strands 12 and the transverse 
strands 14 are arranged in the desired relationship and the reinforcing 
strands 40 are positioned in engagement with the strands 12. The strands 
are then joined together employing conventional welding techniques. As 
with the embodiment illustrated in FIG. 4, the transverse strands 14 
within the preselected areas or portions are preferably spaced so as to 
accommodate the stirrup reinforcement. 
A further alternative embodiment for obtaining the required increase in 
steel area within the selected portions of the fabric is shown in FIG. 6. 
In this embodiment, the circumferential defining line strands 12 are 
formed with quadrant portions 12a having a diameter greater than the 
diameter of the strands 12 outside of the areas where additional quadrant 
reinforcement is required. The diameter of portions 12a is such that the 
steel area of the fabric at the quadrants of the subsequently formed cage 
will be that required for the particular class and size of concrete pipe 
to be manufactured. As with the embodiments illustrated in FIGS. 4 and 5, 
the spacing between the transverse strands 14 within the preselected 
quadrant portions of the fabric is made to accommodate the stirrup 
reinforcement. The circumferential defining line strands of the embodiment 
illustrated in FIG. 6 are formed with the portions of increased diameter 
employing conventional manufacturing processes. This embodiment 
substantially reduces the steps required in the fabrication of a fabric 
having integral quadrant reinforcement. 
In the embodiment illustrated in FIG. 7, the sets of transverse strands 
separated by the readily discernable cut lines are dimensioned so that 
they may be severed into lengths for the ready manufacture of inner and 
outer reinforcing cages. With certain sizes and classes of concrete pipe, 
two cages are employed. The length of the transverse set generally 
designated 50 corresponds to the preselected inner cage. The set 
designated 52 corresponds to the predetermined outer cage. Each set, of 
course, includes the required integral quadrant reinforcement. 
The FIG. 7 fabric is made along the lines of the most preferred FIG. 4 
fabric in that the transverse strands 14e within the quadrant areas are 
spaced more closely together than the transverse strands 14 outside the 
quadrant area. Also, strands 40 and 12 lie in a common plane and strands 
14e and 14 lie in a common place. 
The inner and outer cage arrangement formed from the fabric illustrated in 
FIG. 7 is shown in FIG. 8. As shown therein, the inner cage is reinforced 
at the pipe crown and invert. This reinforcement includes the stirrups 30 
and any one of the previously described embodiments for increasing the 
steel area along the circumferential defining line strands. With the outer 
cage, the areas of maximum stress occur at the spring lines while the 
areas of minimum stress occur around the crown and invert. Therefore, in 
manufacturing the reinforcing cage illustrated in FIG. 8, the pipe 
manufacturer will unroll the fabric, sever the fabric along the readily 
discernable cut lines, roll the set corresponding to the inner cage into 
the desired shape and weld the ends at the spring line of the inner cage. 
Next, the manufacturer will roll the set corresponding to the outer cage 
into the desired shape and join the ends of this at the crown or the 
invert. The inner cage is then positioned coaxially with the outer cage 
and the stirrups 30 are erected. With this embodiment as with the previous 
embodiments, the pipe manufacturer need only buy a single roll of fabric 
for manufacturing a complete run of pipe having the required reinforcement 
for the particular class and size. The manufacture of concrete pipe 
requiring the composite cage construction is made substantially more 
simple when the fabric illustrated in FIG. 7 is employed. 
As a further alternative embodiment, the fabric may be provided with 
diagonal strands 70 as shown in FIG. 9. The diagonal strands 70 are 
positioned on the fabric during the fabric manufacture so as to extend at 
a predetermined angle across the fabric. The diagonal strands 70 are 
employed when the pipe is manufactured by a packer head machine. The 
diagonals resist torsional stresses induced in the fabric during operation 
of the packing device and therefore reduce the incidence of cage 
distortion during this type of pipe manufacturing process. 
FIG. 10 shows a sheet of fabric 100 with a length appropriate for rolling a 
particular size reinforcing cage, including an overhang or lap portion 
101. Each sheet 100 is much like a segment on a roll of fabric 10 as shown 
in FIGS. 1 and 2. However in this embodiment, the quadrant reinforcing 
transverse strands 22 lie on the opposite side of the fabric from 
transverse strands 14, rather than in the same plane therewith. The 
circumferential defining strands 12 lie in the same plane as the 
circumferential defining strands 24 of the quadrant reinforcement. This 
embodiment will also probably pass through roll formers more easily than 
the FIG. 1 embodiment, but probably not as easily as the FIGS. 4, 5 and 7 
embodiments. 
FIG. 11 is an enlarged view of a small portion of FIG. 10. It illustrates 
that the quad circumferential strand 24 can be of a larger diameter than 
the main circumferential 12. Thus, even though quad circumferential 24 
contacts transverse strands 14 and is generally in the same plane as 
circumferential 12, it does project below the bottom of strands 12 because 
it is thicker. 
It should be readily apparent that the unique fabric and the unique method 
of making and using same which forms the subject matter of the present 
invention substantially reduces the amount of wasted material inherent in 
the manufacture of steel reinforced concrete pipe than heretofore 
possible. Further, the fabric since it includes the integral quadrant 
reinforcement and is divided into sets having lengths equal to that 
required for the reinforcement of the predetermined class and size of 
pipe, substantially reduces the steps required by the pipe manufacturer in 
the fabrication of the cages. The pipe manufacturer need merely cut off 
the predetermined lengths of the roll of the fabric, form the cut fabric 
into a cylindrical or elliptical cage and join the ends of the fabric. 
Even the cutting can be eliminated when the fabric is shipped as a 
plurality of separate sheets. This fabric and method of making and using 
same therefore substantially decreases the time and costs attendant to the 
manufacture of steel reinforced concrete pipe. 
Of course, it should be understood that the above is intended to be a 
description of the preferred embodiments only. The true spirit and scope 
of the present invention may be determined by reference to the appended 
claims.