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International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 10, October 2013)
261
Rehabilitation and Strengthening of R.C.C. STRUCTURES by
using FRP composites
Rahul kumar satbhaiya1, Shishir gupta
2, T.R Arora
3
1M.Tech Scholar CTM, LNCT Bhopal (M. P.)
2Asst Proff LNCT Bhopal (M.P.)
3H.O.D Department Of Civil Engg. LNCT Bhopal (M.P.)
Abstract— Fiber Reinforced Polymer (FRP) as an external
reinforcement is used extensively to deal with the strength
requirements related to flexure and shear in structural
systems. But the strengthening of members subjected to
torsion is explored only recently. Torsion failure is an
undesirable brittle form of failure which should be avoided
specially in the earthquake prone areas. In the present work,
the behaviour and performance of rectangular reinforced
concrete beams strengthened with externally bonded Fibre
Reinforced Polymer (FRP) fabrics subjected to combined
flexure and torsion is studied experimentally.
Three sets of concrete cylinders were tested for their
ultimate strengths. In SET I three concrete cylinders (F1, F2
and F3) are tested. In SET II three concrete cylinders (S1, S2
and S3) are tested. In SET III three concrete cylinders (R1, R2
and R3) are tested. The concrete cylinders F1, S1 and C1 were
taken as the control concrete cylinders. It was observed that
the concrete cylinders F1, S1 and C1 had less load carrying
capacity when compared to that of the externally
strengthened beams using FRP sheets. In SET I concrete
cylinders F2 is strengthened only single warp of FRP sheet on
the full dimensions of concrete cylinders and F3 is
strengthened by double warp of FRP sheet on the full
dimensions of concrete cylinders. In SET II concrete
cylinders S2 is strengthened only single warp of FRP sheet on
the full dimensions of concrete cylinders and S3 is
strengthened by double warp of FRP sheet on the full
dimensions of concrete cylinders. In SET III concrete
cylinders R2 is strengthened only single warp of FRP sheet on
the full dimensions of concrete cylinders and R3 is
strengthened by double warp of FRP sheet on the full
dimensions of concrete cylinders. The ultimate load carrying
capacities of all the concrete cylinders are calculated.
Experimental data on ultimate cracking loads of each of
the cylinders were obtained. The effect of different types and
configuration of FRP and ultimate load carrying capacity of
the cylinders were investigated.
Keywords— Concrete, Cylinder, Failure, Fibre, Polymer,
Reinforced
I. INTRODUCTION
This The maintenance, rehabilitation and upgrading of
structural members, is perhaps one of the most crucial
problems in civil engineering applications.
Moreover, a large number of structures constructed in
the past using the older design codes in different parts of
the world are structurally unsafe according to the new
design codes. Since replacement of such deficient elements
of structures incurs a huge amount of public money
and time, strengthening has become the acceptable way of
improving their load carrying capacity and extending their
service lives. Infrastructure decay caused by premature
deterioration of buildings and structures has lead to the
investigation of several processes for repairing or
strengthening purposes. One of the challenges in
strengthening of concrete structures is selection of a
strengthening method that will enhance the strength and
serviceability of the structure while addressing limitations
such as constructability, building operations, and budget.
Previously, the retrofitting of reinforced concrete
structures, such as columns, beams and other structural
elements, was done by removing and replacing the low
quality or damaged concrete or/and steel reinforcements
with new and stronger material. However, with the
introduction of new advanced composite materials such as
fiber reinforced polymer (FRP) composites, concrete
members can now be easily and effectively strengthened
using externally bonded FRP composites.
Retrofitting of concrete structures with wrapping FRP
sheets provide a more economical and technically superior
alternative to the traditional techniques in many situations
because it offers high strength, low weight, corrosion
resistance, high fatigue resistance, easy and rapid
installation and minimal change in structural geometry. In
addition, FRP manufacturing offers a unique opportunity
for the development of shapes and forms that would be
difficult or impossible with the conventional steel
materials. Although the fibers and resins used in FRP
systems are relatively expensive compared with traditional
strengthening materials, labour and equipment costs to
install FRP systems are often lower. FRP systems can also
be used in areas with limited access where traditional
techniques would be impractical.
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 10, October 2013)
262
II. LITREAURE
A review of some significant experimental investigations
conducted using steel plates is presented to demonstrate
some of the structural implications of external plating.
Research work into the performance of members
strengthened with steel plates was pioneered
simultaneously in South Africa and France in the 1960s
(L’Hermite and Bresson, 1967; Fleming and King,1967;
Lerchenthal,1967; Gilibert et al.,1976). Continued
development of suitable adhesives and the increased use of
the technique in practice stimulated further research work.
Eberline et al. (1988) present a literature review on
research and applications related to steel plate
bonding.Preliminary studies were conducted by Irwin
(1975). Macdonald (1978) and Macdonald and Calder
(1982) reported four point loading tests on steel plated RC
beams of length 4900mm. These beams were used to
provide data for the proposed strengthening of the Quinton
Bridges (Raithby, 1980 and 1982), and incorporated two
different epoxy adhesives, two plate thicknesses of 10.0mm
and 6.5mm giving width-to-thickness (b/t) ratios of 14 and
22, and a plate lap-joint at its centre. In all cases it was
found that failure of the beams occurred at one end by
horizontal shear in the concrete adjacent to the steel plate,
commencing at the plate end and resulting in sudden
separation of the plate with the concrete still attached, up to
about mid-span. The external plate was found to have a
much more significant effect in terms of crack control and
stiffness. The loads required to cause a crack width of
0.1mm were increased by 95%, whilst the deflections under
this load were substantially reduced. The post cracking
stiffness was found to be increased by between 35-
105% depending upon the type of adhesive used and the
plate dimensions. The features of this work became the
subject of a more detailed programme of research at the
TRRL (Macdonald, 1982; Macdonald and Calder, 1982), in
which a series of RC beams of length 3500mm were tested
in four point bending. The beams were either plated as-cast
or plated after being loaded to produce a maximum crack
width of 0.1mm. The effect of widening the plate whilst
maintaining its cross-sectional area constant was studied. It
was found that the plated as-cast and the pre-cracked beams
gave similar load/deflection curves, demonstrating the
effectiveness of external plating for strengthening purposes.
The benefits of utilising FRP materials over steel in plate
bonding applications are thus clear. The drawbacks are the
intolerance to uneven bonding surfaces which may cause
peeling of the plate, the possibility of brittle failure modes
(Swamy and Mukhopadhyaya, 1995) and the material cost,
since fiber composites are between 4-20 times as expensive
as steel in terms of unit volume.
However, in a rehabilitation project, where material
costs rarely exceed 20% of the overall project cost, the
installation savings can offset the higher material costs
(Meier, 1992). Peshkam and Leeming (1994) have
considered the commercial viability of FRP plate bonding
for bridge strengthening. In a straight comparison with steel
plate bonding for a typical application, despite the fact that
material costs will be increased, labour and equipment
costs will be reduced, construction times will be shorter
and durability will be improved. It is shown that 2kg of
FRP could replace 47kg of steel on an equal strength basis.
The costs of installing both materials are shown to be
similar; however, when traffic management, traffic delay
and maintenance costs are included, the use of FRP
provides a saving of 17.5% over steel. There are situations
where steel plate bonding is not a viable option because of
the extent of chloride contamination of the concrete. In
such cases, the use of FRP may avoid the need for
demolition and replacement. Peshkam and Leeming (1994)
presented a cost comparison of bridge replacement against
strengthening with FRP, in which possible savings of 40%
are demonstrated. These cost comparisons were made
before true manufacturing and installation costs were
known and were at the best estimates. Subsequently the
tendering process for real installation projects has shown
carbon fiber reinforced polymer (CFRP) plate bonding to
be very competitive against steel plate bonding in first cost,
before even future maintenance costs are added to the
whole life cost equation.
Saadatmanesh and Ehsani (1991) conducted an
xperimental study of the strengthening of reinforced
concrete beams using non-prestressed and prestressed
GFRP plates. One of the two prestressed beams contained a
relatively small amount of internal tensile steel
reinforcement, while the other contained larger bars and
was precracked prior to bonding of the plate. The plate
prestress in the precracked case closed some of the cracks,
indicating the benefit of prestressing from a serviceability
point of view. The beam with little original reinforcement
before plating experienced a large improvement in ultimate
capacity due to the additional moment couple provided by
the plate prestress. In both cases, the prestress was
generated by cambering the beam before bonding the plate
so that a tensile load was transferred to the plate when the
camber was released. Improved concrete crack control was
observed with prestressed plates, a clear advantage from a
serviceability point of view. A previous experimental study
by Saadatmanesh and Ehsani (1990) also included the
prestressing of a beam by cambering; this particular
specimen had a low internal reinforcement area ratio of
0.32% (based on effective depth) so that a very high
increase in ultimate load (323%) was observed as a result.
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 10, October 2013)
263
The GFRP plate was not anchored at its ends, and failure
occurred by premature plate separation associated with the
removal of a layer of concrete from the tension face of the
beam.
III. EXPERIMENTAL STUDY
The experimental study consists of casting of three sets
of reinforced concrete (RC) cylinders of size 150mm
diameter and 300mm height. In SET I three cylinders of M-
15 grade of concrete were casted, out of which one is
unreinforced and other two were strengthened using
continuous fiber reinforced polymer (FRP) sheets. In SET
II three cylinders of M-20 grade of concrete weak in shear
were casted, out of which one is the unreinforced and other
two were strengthened by using continuous fiber reinforced
polymer (FRP) sheets in shear. In SET III three cylinders of
M-25 grade of concrete weak in shear were casted, out of
which one is the unreinforced and other two were
strengthened by using continuous fiber reinforced polymer
(FRP) sheets in shear. The strengthening of the cylinder is
done with varying configuration and layers of FRP sheets.
Experimental data on load and failure modes of each of the
cylinder were obtained. The change in load carrying
capacity and failure mode of the cylinder are investigated
as the amount and configuration of FRP sheets are altered.
The following chapter describes in detail the experimental
study. In this study we have taken four cases for checking
the strength of unreinforced concrete cylinders over the
reinforced concrete cylinders with FRP (Fiber Reinforced
Plastic) sheets. In each case we have taken three sets of
concrete cylinders having different grades of concrete. All
experimental details given in table below.
Table 3.1
Case study details
CASE NO. LOCATIO
N
DETAILS
Case-I Sagar (M.P.)
Experimental grades
of Concrete M-15, M-
20 and M-25
Case-II Sagar (M.P.)
Experimental grades
of Concrete M-15, M-
20 and M-25
Case-III Bhopal
(M.P.)
Experimental grades
of Concrete M-15, M-
20 and M-25
Case-IV Bhopal
(M.P.)
Experimental grades
of Concrete M-15, M-
20 and M-25
All the specimens were tested in the “Structural
Engineering” Laboratory of Gov. Engg. College SAGAR
(M.P.). The testing procedure for the entire specimen was
same. After the curing period of 28 days was over, the as
washed and its surface was cleaned for clear visibility of
cracks. The most commonly used load arrangement for
testing of cylinders will consist of compression testing
machine loading. Before testing the member was
checked dimensionally, and a detailed visual inspection
made with all information carefully recorded. Loads will
then normally be increased again in similar increments up
to failure, cracking and manual strain observations must be
suspended as failure approaches unless special safety
precautions are taken. If it is essential that precise
deflection readings are taken up to collapse. Cracking and
failure mode was checked visually, and a load/deflection
plot was prepared.
To meet the wide range of needs which may be required
in fabricating composites, the industry has evolved over a
dozen separate manufacturing processes as well as a
number of hybrid processes. Each of these processes offers
advantages and specific benefits which may apply to the
fabricating of composites. Hand lay-up and spray-up are
two basic moulding processes. The hand lay-up process is
the oldest, simplest, and most labour intense fabrication
method. The process is most common in FRP marine
construction. In hand lay-up method liquid resin is placed
along with reinforcement (woven glass fiber) against
finished surface of an open mould. Chemical reactions in
the resin harden the material to a strong, light weight
product. The resin serves as the matrix for the reinforcing
glass fibers, much as concrete acts as the matrix for steel
reinforcing rods. The percentage of fiber and matrix was
50:50 in weight.
The following constituent materials were used for
fabricating the plate:
1. E-glass woven roving as reinforcement
2. Epoxy as resin
3. Hardener as diamine (catalyst)
4. Polyvinyl alcohol as a releasing agent
Contact moulding in an open mould by hand lay-up was
used to combine plies of woven roving in the prescribed
sequence. A flat plywood rigid platform was selected. A
plastic sheet was kept on the plywood platform and a thin
film of polyvinyl alcohol was applied as a releasing agent
by use of spray gun. Laminating starts with the application
of a gel coat (epoxy and hardener) deposited on the mould
by brush, whose main purpose was to provide a smooth
external surface and to protect the fibers from direct
exposure to the environment.
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 10, October 2013)
264
Ply was cut from roll of woven roving. Layers of
reinforcement were placed on the mould at top of the gel
coat and gel coat was applied again by brush. Any air
which may be entrapped was removed using serrated steel
rollers. The process of hand lay-up was the continuation of
the above process before the gel coat had fully hardened.
Again, a plastic sheet was covered the top of plate by
applying polyvinyl alcohol inside the sheet as releasing
agent. Then, a heavy flat metal rigid platform was kept top
of the plate for compressing purpose. The plates were left
for a minimum of 48 hours before being transported and
cut to exact shape for testing.
FIG 3.1-Application of epoxy and hardener on the
concrete structure
FIG -3.2 Fixing of FRP sheet on the concrete structure
IV. RESULTS
Three sets of concrete cylinders were tested for their
ultimate strengths. In SET I three concrete cylinders (F1,
F2 and F3) are tested. In SET II three concrete cylinders
(S1, S2 and S3) are tested. In SET III three concrete
cylinders (R1, R2 and R3) are tested.
The concrete cylinders F1, S1 and C1 were taken as the
control concrete cylinders. It was observed that the
concrete cylinders F1, S1 and C1 had less load carrying
capacity when compared to that of the externally
strengthened beams using FRP sheets. In SET I concrete
cylinders F2 is strengthened only single warp of FRP sheet
on the full dimensions of concrete cylinders and F3 is
strengthened by double warp of FRP sheet on the full
dimensions of concrete cylinders. In SET II concrete
cylinders S2 is strengthened only single warp of FRP sheet
on the full dimensions of concrete cylinders and S3 is
strengthened by double warp of FRP sheet on the full
dimensions of concrete cylinders. In SET III concrete
cylinders R2 is strengthened only single warp of FRP sheet
on the full dimensions of concrete cylinders and R3 is
strengthened by double warp of FRP sheet on the full
dimensions of concrete cylinders. The ultimate load
carrying capacity of all the concrete cylinders is given in
Tables below.
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 10, October 2013)
265
Table 4.1
Results for M-15 grade of concrete in Case -I
Sr.
No.
Date of
casting
Grade of
Concrete
Date of
Test
Cylinder
Status
Breaking
Load (MT)
Strength
Kg/cm2
Remark
1. 15/06/2013 M-15 12/07/2013 Without
warp
35.75 202.40 Initial stage
2. 15/06/2013 M-15 12/07/2013 Single
warp
55.45 313.94 Increased by
55% from
initial stage
3. 15/06/2013 M-15 12/07/2013 Double
warp
77 435.95 Increased by
38.86% from
single warp
Table 4.2
Results for M-20 grade of concrete in Case -I
Sr.
No.
Date of
casting
Grade of
Concrete
Date of
Test
Cylinder
Status
Breaking
Load (MT)
Strength
Kg/cm2
Remark
1. 16/06/2013 M-20 13/07/2013 Without
warp
45.75 259 Initial stage
2. 16/06/2013 M-20 13/07/2013 Single
warp
65.45 370.55 Increased by
43% from
initial stage
3. 16/06/2013 M-20 13/07/2013 Double
warp
87 492.56 Increased by
33% from
single warp
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 10, October 2013)
266
Table 4.3
Results for M-25 grade of concrete in Case –I
Sr.
No.
Date of
casting
Grade of
Concrete
Date of
Test
Cylinder
Status
Breaking
Load (MT)
Strength
Kg/cm2
Remark
1. 17/06/2013 M-25 14/07/2013 Without
warp
52.45 296.95 Initial stage
2. 17/06/2013 M-25 14/07/2013 Single
warp
69.23 391.96 Increased by
32% from
initial stage
3. 17/06/2013 M-25 14/07/2013 Double
warp
98.76 559.15 Increased by
43% from
single warp
Table 4.4
Results for M-15 grade of concrete in Case –II
Sr.
No.
Date of
casting
Grade of
Concrete
Date of
Test
Cylinder
Status
Breaking
Load (MT)
Strength
Kg/cm2
Remark
1. 18/06/2013 M-15 15/07/2013 Without
warp
34.85 197.31 Initial stage
2. 18/06/2013 M-15 15/07/2013 Single
warp
56.24 318.41 Increased by
61% from
initial stage
3. 18/06/2013 M-15 15/07/2013 Double
warp
76.85 435.10 Increased by
36% from
single warp
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 10, October 2013)
267
Table 4.5
Results for M-20 grade of concrete in Case –II
Sr.
No.
Date of
casting
Grade of
Concrete
Date of
Test
Cylinder
Status
Breaking
Load (MT)
Strength
Kg/cm2
Remark
1. 19/07/2013 M-20 16/08/2013 Without
warp
45.20 255.90 Initial stage
2. 19/07/2013 M-20 16/08/2013 Single
warp
64.84 367.10 Increased by
43.45% from
initial stage
3. 19/07/2013 M-20 16/08/2013 Double
warp
85.88 486.22 Increased by
32% from
single warp
Table 4.6
Results for M-25 grade of concrete in Case –II
Sr.
No.
Date of
casting
Grade of
Concrete
Date of
Test
Cylinder
Status
Breaking
Load (MT)
Strength
Kg/cm2
Remark
1. 20/07/2013 M-25 17/08/2013 Without
warp
51.25 290.16 Initial stage
2. 20/07/2013 M-25 17/08/2013 Single
warp
68.88 389.97 Increased by
34.39% from
initial stage
3. 20/07/2013 M-25 17/08/2013 Double
warp
97.95 554.56 Increased by
42.2% from
single warp
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 10, October 2013)
268
Table 4.7
Results for M-15 grade of concrete in Case –III
Table 4.8
Results for M-20 grade of concrete in Case –III
Sr.
No.
Date of
casting
Grade of
Concrete
Date of
Test
Cylinder
Status
Breaking
Load (MT)
Strength
Kg/cm2
Remark
1. 24/06/2013 M-15 14/07/2013 Without
warp
35.05 198.44 Initial stage
2. 24/06/2013 M-15 14/07/2013 Single
warp
56.29 318.69 Increased by
60% from initial
stage
3. 24/06/2013 M-15 14/07/2013 Double
warp
76.15 431.13 Increased by
36.64% from
single warp
Sr.
No.
Date of
casting
Grade of
Concrete
Date of
Test
Cylinder
Status
Breaking
Load (MT)
Strength
Kg/cm2
Remark
1. 26/07/2013 M-20 15/08/2013 Without
warp
44.89 254.15 Initial stage
2. 26/07/2013 M-20 15/08/2013 Single
warp
64.56 365.52 Increased by
43.38% from
initial stage
3. 26/07/2013 M-20 15/08/2013 Double
warp
85.42 483.62 Increased by
32.31% from
single warp
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 10, October 2013)
269
Table 4.9
Results for M-25 grade of concrete in Case –III
Table 4.10
Results for M-15 grade of concrete in Case –IV
Sr.
No.
Date of
casting
Grade of
Concrete
Date of
Test
Cylinder
Status
Breaking
Load (MT)
Strength
Kg/cm2
Remark
1. 27/07/2013 M-15 16/08/2013 Without
warp
35.19 199.23 Initial stage
2. 27/07/2013 M-15 16/08/2013 Single
warp
57.05 323 Increased by
62.12% from
initial stage
3. 27/07/2013 M-15 16/08/2013 Double
warp
76.45 432.83 Increased by
34% from
single warp
Sr.
No.
Date of
casting
Grade of
Concrete
Date of
Test
Cylinder
Status
Breaking
Load (MT)
Strength
Kg/cm2
Remark
1. 26/07/2013 M-25 15/08/2013 Without
warp
50.85 287.89 Initial stage
2. 26/07/2013 M-25 15/08/2013 Single
warp
67.28 380.92 Increased by
32.31% from
initial stage
3. 26/07/2013 M-25 15/08/2013 Double
warp
96.70 547.48 Increased by
43.72% from
single warp
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 10, October 2013)
270
Table 4.11
Results for M-20 grade of concrete in Case –IV
Sr.
No.
Date of
casting
Grade of
Concrete
Date of
Test
Cylinder
Status
Breaking
Load (MT)
Strength
Kg/cm2
Remark
1. 28/07/2013 M-20 17/08/2013 Without
warp
45.10 255.34 Initial stage
2. 28/07/2013 M-20 17/08/2013 Single
warp
64.95 367.72 Increased by
44.01% from
initial stage
3. 28/07/2013 M-20 17/08/2013 Double
warp
85.92 486.45 Increased by
32.2% from
single warp
Table 4.12
Results for M-25 grade of concrete in Case –IV
Sr.
No.
Date of
casting
Grade of
Concrete
Date of
Test
Cylinder
Status
Breaking
Load (MT)
Strength
Kg/cm2
Remark
1. 28/07/2013 M-25 17/08/2013 Without
warp
51.25 290.16 Initial stage
2. 28/07/2013 M-25 17/08/2013 Single
warp
68.15 385.84 Increased by
32.97% from
initial stage
3. 28/07/2013 M-25 17/08/2013 Double
warp
96.25 544.93 Increased by
41.23% from
single warp
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271
Fig – 4.1 Combined results for breaking load on grades case-I
Fig – 4.2 Combined results for breaking load on grades case-II
International Journal of Emerging Technology and Advanced Engineering
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272
Fig – 4.3 Combined results for breaking load on grades case-III
Fig – 4.4 Combined result for breaking load on grades case-IV
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273
V. CONCLUSION
All specimens are tested At Gov. Engineering College
Civil Laboratory, SAGAR. The results of testing on
cylinders are given above in tables. In this exercise we have
chosen three grades of concrete cylinders M-15, M-20 and
M-25 which are generally used in these days for
construction work under the limit state design consideration.
Test Cylinders Size 150 mm diameter x 300 mm height
water cured. Date of Wrapping is 36 hrs before from date of
testing. We have made 3specimens for each grade and tests
are applied on all 9 specimens. In this study the specimens
are made by concrete and warp with the FRP (Fibre-
reinforced plastic). The tests are conducted on normal
concrete and FRP warped concrete. After completing all the
analysis on normal concrete and FRP warped concrete
grades M-15, M-20 and M-25, the strength of concrete grade
is increased with average 37% for all grades.
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