METHOD OF WORKING CONNECTION END OF DEFORMED BAR FOR REINFORCING CONCRETE, DEFORMED BAR WORKED BY THE METHOD AND STRUCTURE DEFORMED BAR

METHODE DE RACCORDEMENT D'EXTREMITE DE BARRE DEFORMEE POUR ARMATURE DE BETON, METHODE DE TRAVAIL DE BARRE DEFORMEE ET BARRE STRUCTURALE DEFORMEE

English Abstract

With an object of providing a method of working a connection end portion of deformed bar for reinforcing concrete considerably reducing working expense by enhancing easiness of working by promoting mechanical strength of a connection portion by being able to work the connection portion without destructing a steel skeleton structure of a connection portion between pieces of steel bar, deformed bar worked by the method and a connection structure of deformed bar, the invention provides a method of working a connection end portion of deformed bar for reinforcing concrete featured in comprising a swaging step in which in deformed bar for reinforcing concrete featured in swaging at least a connection end portion at normal temperature and forming a rolled thread portion at an outer peripheral face of the connection end portion of the deformed bar subjected to the swaging step in which at least one connection end portion is swaged at a normal temperature such that a maximum diameter of the connection end portion is equal to or slightly larger than a diameter of a cylindrical body of the deformed bar or slightly smaller than a diameter of the deformed bar depending on a degree of working; and a rolling step of forming a thread portion having a diameter substantially equal to a swaging diameter at an outer peripheral face of the connection end portion of the deformed bar which has been subjected to the swaging step.

French Abstract

Linvention concerne un procédé de travail dune partie dextrémité de raccordement de barre déformée pour armer du béton réduisant considérablement la dépense de travail par lamélioration de la facilité de travail en favorisant la résistance mécanique dune partie de raccordement en étant capable de travailler la partie de raccordement sans détruire une structure darmature en acier dune partie de raccordement entre des pièces de barres en acier, une barre déformée travaillée par le procédé et une structure de raccordement de barre déformée, linvention prévoyant un procédé de travail dune extrémité de raccordement de barre déformée pour du béton de renforcement caractérisé en ce quil comprend une étape de rétreinte dans laquelle dans une barre déformée destinée à armer du béton, est caractérisée par la rétreinte dau moins une partie dextrémité de raccordement à une température normale et la formation dune partie de filet laminée au niveau dune face périphérique externe de lextrémité de raccordement de la barre déformée soumise à létape de rétreinte dans laquelle au moins une partie dextrémité de raccordement est rétreinte à une température normale de sorte quun diamètre maximal de la partie dextrémité de raccordement soit égal ou légèrement supérieur à un diamètre dun corps cylindrique de la barre déformée ou légèrement inférieur à un diamètre de la barre déformée en fonction dun degré de travail; et une étape de laminage consistant à former une partie de filet ayant un diamètre sensiblement égal à un diamètre de rétreinte dune face périphérique externe de la partie dextrémité de raccordement de la barre déformée qui a été soumise à létape de rétreinte.

Claims

What is claimed is:
1. A method of working a connection end portion of deformed bar for
reinforcing concrete characterized in comprising a swaging step in which in a
cylindrical
body of the deformed bar for reinforcing concrete, at least one connection end
portion of
the deformed bar in the deformed bar for reinforcing concrete having ribs and
a number
of nodes is swaged at a normal temperature such that a maximum diameter of the
connection end portion is equal to or slightly larger than a diameter of the
cylindrical
body or slightly smaller than a diameter of the deformed bar depending on a
degree of
working; and
a rolling step of forming a thread portion having a diameter substantially
equal
to a swaging diameter at an outer peripheral face of the at least one
connection end
portion of the deformed bar which has been subjected to the swaging step.
2. The method of working a connection end portion of deformed bar for
reinforcing concrete according to Claim 1, characterized in that an axis of
the connection
end portion of the deformed bar which has been subjected to the swaging step
is aligned
concentrically with an axis of a cylindrical body of the deformed bar formed
with the ribs
and the modes.
3. The method of working a connection end portion of deformed bar for
reinforcing concrete according to Claim 1, characterized in adding a step of
cutting for
facing and chamfering a side end face of the connection end portion of the
deformed bar
subjected to the swaging step.
4. The method of working a connection end portion of deformed bar for
reinforcing concrete according to Claim 1, characterized in that in the
rolling step, a
groove diameter of a thread ridge at a boundary contiguous to the rib and the
node is
gradually increased at the thread portion of rolling.

Description

CA 02268878 1999-04-13
Method of working connection end of deformed bar for reinforcing concrete,
deformed bar worked by the method and structure of connecting deformed bar.
s 1. Field a~f Ttre Invenrion
The present invention relates to a method of working a thread at a connection
end of deformed bar for reinforcing concrete for forming a framework of a
construction
object at sites of construction and civil engineering works, deformed bar
worked by the
method and a connection structure of deformed bar.
2. Description o~ the Prior Art
Generally, at sites of construction and civil engineering works, after
building a
basic framework by using deformed bar for reinforcing concrete, in a procedure
of
applying and curing concrete, a construction object is erected. In this case,
deformed
bar refers to bar having projections on the surface, projection in the axial
direction refers
is to "rib" and projection other than in the axial direction refers to "node".
Further, deformed bar for reinforcing concrete mentioned above is supplied by
being cut in a predetermined length and accordingly, depending on a size of a
construction object, deformed bar for reinforcing concrete is used by being
cut or by
being cut to a necessary length by mutually connecting pieces thereof.
2o Further, in mutually connecting pieces thereof, there is used a latching
process in
which connection end portions of respective pieces of deformed bar are made to
overlap,
thereafter, bound by steel wires.
However, loss of material is enormous since connection end portions of the
respective pieces of deformed bar are used to overlap, pieces of deformed bar
are
2s connected by using steel wires and accordingly, there poses a problem in
which
1

CA 02268878 1999-04-13
connection portions are agingly weakened and considerable labor cost is
required in
of connecting operation.
Further, a steel skeleton connected by the latching process achieves a feature
of
the connected steel skeleton structure only after applying concrete mortar and
completing
s curing operation by the force of adhering the steel skeleton with concrete
and accordingly,
when there causes trouble accidentally in concrete mortar or in the curing
operation, the
fragile structural feature of a structure may emerge.
As a method of resolving such a problem, there has been proposed a hot
upsetting method of connection end portions which is a kind of a mechanical
method of
to connection. This method is a method of upsetting the connection end
portions by
exerting force in the axial direction of deformed bar after heating the
connection end
portions.
However, there may also cause loss of material by shrinking the length of
deformed bar.
15 Further, heat is locally applied to the connection end portions and
accordingly,
there poses a problem in which the elongation rate is decreased by a change in
the
material structure of the connection end portions between a portion affected
by heat and
a portion not affected by heat, the connection end portion becomes weak at
impact and
irregular structure distribution emerges by partial heating.
2o Further, in order to resolve the problem, there has been developed a cold
process which is a method different from the above-described.
That is, according to the method, connection end portions are upset by
exerting
large pressure on the connection end portions along the axial direction of
deformed bar at
normal temperature (FIG. 5). In the process, there have bin proposed a first
method
25 in which a cut thread portion is formed at the connection end portion and a
second
2

CA 02268878 1999-04-13
method in which a rolled thread portion is forms after finishing the cutting
operation for
sltimming the upset connection end portion.
Incidentally, among the first method has been developed by Techniport
S.A. and is disclosed in Korean Examined Patent Publication No. 94-8311 and
s corresponding U. S. Patent 5,158, 527 and the second method has been
developed by CCL
of Great Britain a~ is disclosed in British Patent 2,286,782 A.
However, according to deformed bar worked by the upsetting method, there
were problems that the tensile strength and the hardness become extremely high
by work
hardening and a value of impact absorption energy is rapidly decreased.
1o Meanwhile, when a metallographic structure (FIG. 6A and FIG. 6B) of an
upset
connection end portion of deformed bar is compared with a metallographic
structure
(FIG. 7A and FIG. 7B) of original material, FIG. 6A and FIG. 7A respectively
show
metallographic structures along the axial direction of the upset material and
the original
material and it is known that in FIG. 7A, while ferrite and pearlite
structures progress
15 long and continuously in the axial direction, in FIG. 6A, the continuity of
the
metallographic structure in the axial direction is interrupted.
Further, FIG. 6B and FIG. 7B respectively show structures along a direction
orthogonal to the axis of the upset and the original materials and it is known
that while
according to the original material of FIG. 7B, ferrite and pearlite structures
are uniformly
2o distributed, according to the upset portion of FIG. 6B, the metallographic
structure is
considerably coarsened. Thereby, it is known that the structure of the upset
portion is
nonuniformly formed.
In order to resolve the above-described problem, it is an object of the
invention
25 to provide a method of working a thread of a connection end portion of
deformed bar for
3

CA 02268878 1999-04-13
r~nforcing concrete and a structure of connecting deformed bar worked in
accordance
with the method.
Further, it is other object of tl~ invention to provide a method of working a
connection end portion of deformed bar for reinforcing concrete capable of
maintaining a
s fibrous structure inherent to deformed bar by not carrying out cutting
operation and a
connection sti ucture of deformed bar obtained by using the method.
Further, it is other object of the invention to provide a method of working a
connection end portion of deformed bar for reinforcing concrete for making a
structure
remain unchanged by not applying heat and a connection structure of deformed
bar
to obtained by using the method.
Further, it is other object of the invention to provide a method of working a
connection end portion of deformed bar for reinforcing concrete for
compensating for a
weakness in a stnacture caused by work hardening by not upsetting the
connection end
portion and a connection structure of deformed bar worked by the method.
1s In order to realize such a problem, according to the invention, there is
provided
a method of working a connection end portion of deformed bar for reinforcing
concrete
characterized in comprising a swaging step in which in the deformed bar for
reinforcing
concrete, at least one connection end portion of the deformed bar for
reinforcing concrete
having ribs and a number of nodes is swaged at a normal temperature tech that
a
2o maximum diameter of the connection end portion is equal to or slightly
larger than a
diameter of a cylindrical body of the deformed bar or slightly smaller than a
diameter of
the deformed bar depending on a degree of working; and
a rolling step of forming a thread portion having a diameter substantially
equal to
a swaging diameter at an outer peripheral face of the connection end portion
of the
25 deformed bar which has been subjected to the swaging step.
4

CA 02268878 1999-04-13
Further, according to the invention, there is provided a deformed bar for
reinforcing concrete characterized in that at least one connection end portion
is swaged at
a ~rmal temperature anti a rolled thread portion is formed at the one
connection end
portion of the deformed bar subjected to the swaging step.
s Further, the invention is featured in a connection structure of a deformed
bar for
reinforcing concr~e in which at least one connection end portion is swaged at
a normal
temperature and pieces of the deformed bar each formed with a rolled thread
portion at
an outer peripheral face thereof which has been subjected to the swaging step
are
connected by a connector having a thread in a mode in correspondence with the
rolled
1o thread.
BRIEF ESCRIPTION OF TIC DRAWINGS
FIG. lA through FIG. lE are stage views showing a method of working a
connection end portion of deformed bar for reinforcing concrete according to
the
invention.
1 s FIG. 2 is a view enlarging a thread portion of FIG. 1 E.
FIG. 2A and FIG. 2B are views showing preferred embodiments of thread
portions.
FIG. 3A is a metallogaphic structure diagram along an axial direction of a
connection end portion according to the invention.
2o FIG. 3B is a metallogaphic structure view along a direction orthogonal to
an
axis of the connection end portion according to the invention.
FIG. 4 illustrates state views for connecting deformed bar according to the
invention by couplers.
FIG. 5 is a state view in which a connection end portion of deformed bar for
25 reinforcing concrete in line with a conventional technology is upset.
s

CA 02268878 1999-04-13
FIG. 6A is a metallographic structure diagram along an axial direction of the
connection end portion of FIG. 5.
FIG. 6B is a metallographic structure diagram along a direction orthogonal to
an
axis of the connection end portion of FIG. 5.
s FIG. 7A is a metallographic structure diagram along an axial direction of an
original material used in the invention and the conventional technology.
FIG. 7B is a metallographic structure diagram along a direction orthogonal to
an
axis of the original material used in the invention and the conventional
technology.
FIG. 8A and FIG. 8B are a front view and a side view of dies showing a state
of
to swaging a connection end portion of deformed bar for reinforcing concrete.
A further detailed explanation will be given of preferred embodiments
according
to the invention in reference to the drawings as follows.
15 FIG. 1 A shows deformed bar for reinforcing concrete before working and a
deformed bar for reinforcing concrete 100 is constituted by a cylindrical body
10 and ribs
30 and nodes 20 formed on an outer peripheral face thereof at equal intervals.
Further, as shown by FIG. 1 A, according to a long piece of deformed bar, a
connection end portion 40 may normally be bent relative to an intermediary
portion of
2o deformed bar.
Further, FIG. 1B shows a swaging step in which deformed bar is inserted into
swaging dies (FIG. 8A is a front view, FIG. 8B is a side view) constituted by
2 or more
of pieces or rollers, thereafter, hydraulic or mechanical force is exerted and
swaging is
carried out at normal temperature.
2s Further, the projected ribs 30 and the nodes 20 of the connection end
portion 40
6

CA 02268878 1999-04-13
shown by FIG. 1 A are pressed such that diameters thereof become substantially
equal to
a diameter 11 of the cylindrical body of the deformed bar 100.
In this way, an axis 19 of the cylindrical body 10 is aligned to be concentric
with
an axis 59 of a swaged portion 50. By being processed by the step, deformed
projection portions of the ribs 30 or deformation of a steel skeleton bar
member can be
finished to be straight.
Thereafter, a section of the connection end portion 50 projected by the
swaging
step is machined similar to FIG. 1C, a section 53 is flattened by facing and
chamfering
and an edge 55 at an outer periphery of the section 53 is faced.
1o FIG. lE is a state view showing a state of deformed bar finished with
working
operation.
In this way, by restraining destruction of a thread at a corner in handling
deformed bar, fastening force of deformed bar is promoted.
Further, a thread portion 60 is formed by rolling an outer peripheral face of
the
swaged portion 50 similar to FIG. lE.
Further, an outer diameter 61 of the rolled thread portion 60 is formed to be
equal to or slightly larger than the diameter 11 of the cylindrical body 10.
In this way, the metallographic structure of the thread portion material
according
to the invention is not cut, according to the plastically worked thread
portion, the
2o mechanical strength is promoted, the metallographic stricture becomes
dense, at the
same time, an inner portion of the connection portion maintains an inherent
structure and
accordingly, the connection portion withstands large load and impact.
FIG. 3A and FIG. 3B show photographs of a structure of a connection end
portion of deformed bar according to the invention, FIG. 3A shows a
metallographic
structure along the axial direction of deformed bar and it is known that the
continuity of
7

CA 02268878 1999-04-13
ferrite and pearlite structures shown by FIG. 7A emerges further clearly and
the structure
also becomes dense.
Further, FIG. 3B shows a metallographic structure along a direction orthogonal
to an axis of deformed bar and the structure emerges more densely than the
ferrite and
s pearlite structures shown by FIG. 7B.
Meanwhile, in working the thread portion, although various kinds of threads
such as a circular thread or a triangular thread and the like can be worked,
the thread
portion is worked by a circular thread more preferably.
For example, threads can be worked as shown by FIG. 2A and FIG. 2B.
to The reason is that when the working is carried out by a circular thread,
the
section of a thread ridge is rounded and a tooth root portion is constituted
thickly as in a
trapezoidal thread and accordingly, the resistance force is intensif ed, as a
result, not only
a notch phenomenon does not occur but also a fastening force is intensified
and the
thread can be fastened easily at a construction site replete with dust or
sand.
1 s Further, when the pitch of the circular thread is narrowed more than that
of a
general thread, not only the fastening force and the strength are promoted but
also there
is no concern of relaxation even when considerable vibration is caused.
Further, a stress concentration phenomenon can be restrained by gadually
increasing a groove diameter 63 of a thread ridge at a boundary 65 contiguous
to the rib
20 30 and the node 20 from the rolled thread portion 60 as shown by FIG. 2.
Further, although there is illustrated the deformed bar 100 for reinforcing
concrete formed with the ribs 30 and the nodes 20 in FIG. lA, the invention is
not limited
thereto but is applicable to deformed bar for reinforcing concrete having ribs
formed in
slanted lines or X-like lines.
25 There is shown in FIG. 4 a method of connecting pieces of deformed bar for

CA 02268878 1999-04-13
reinforcing concrete formed as described above, there is adopted a coupler 200
provided
with nut portions (Figs. 4B, 4C) in correspondence with a shape of the rolled
thread
portion 60 for connccting the rolled thread portions 60 formed at the
connection end
portions 40 of respective pieces of the deformed bar 100.
s As described above, according to the invention, by enabling to work a
connection portion of deformed bar for reinforcing concrete used at sites of
construction
and civil engineering works without destrocting a steel skeleton structure of
the
connection portion, the mechanical strength of the connection portion can be
promoted.
Further, the connection portion can be formed by swaging dies and rolling and
to accordingly, fabrication thereof is extremely facilitated, further,
reduction in fabrication
expense accompanied thereby is made possible. Particularly, when the
connection
portion is fabricated by a circular thread, there is achieved an advantage in
which
fastening is facilitated, connecting operation is much facilitated, shortening
of a
construction time period as well as a reduction in expense are achieved,
compared with a
1s connection structure of deformed bar fabricated by a conventional upsetting
system, the
length of deformed bar can be maintained as it is and accordingly, about 1
through 2 % of
material can be saved.
9

Representative Drawing