Page 1 of 4
European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 05
May 2019
Available online:https://ejbss.org/ P a g e | 841
Short-term durability test oncompressive behavior of concrete
Cylinders confined with frpcomposites under various environmental conditions
T. KURUTHIVELMARAN
DEPARTMENT OF CIVIL ENGINEERING
PRIST (Deemed to be University), THANJAVUR.
INTRODUCTION
Existing reinforced concrete columns may
be structurally deficient for several
reasons: substandard seismic design
details, improper transverse reinforcement,
flaws in structural design, and insufficient
load carrying capacity. Over the last few
years, there has been a worldwide increase
in the use of composite materials for the
rehabilitation of deficient reinforced
concrete structures. One important
application of this composite retrofitting
technology is the use of fiber reinforced
polymer (FRP) jackets or sheets to provide
external confinement to reinforced
concrete columns when the existing
internal transverse reinforcement is
inadequate. Reinforced concrete columns
need to be laterally confined in order to
ensure large deformation under load before
failure and to provide an adequate load
resistance capacity. In the case of a
seismic event, energy dissipation allowed
by a well confined concrete core can often
save lives. On the contrary, a poorly
confined concretecolumn behaves in a
brittle manner, leading to sudden and
catastrophic failures.
Existing reinforced concrete columns may
be structurally deficient for several
reasons:substandard seismic design details,
improper transverse reinforcement, flaws
in structuraldesign, and insufficient load
carrying capacity. Over the last few years,
there has been aworldwide increase in the
use of composite materials for the
rehabilitation of deficientreinforced
concrete structures. One important
application of this composite retrofitting
technology is the use of fiber reinforced
polymer (FRP) jackets or sheets to provide
external confinement to reinforced
concrete columns when the existing
internal transverse reinforcement is
inadequate. Reinforced concrete columns
need to be laterally confined in order to
ensure large deformation under load before
failure and to provide an adequate
loadresistance capacity. In the case of a
seismic event, energy dissipation allowed
Page 2 of 4
European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 05
May 2019
Available online:https://ejbss.org/ P a g e | 842
by a well confined concrete core can often
save lives. On the contrary, a poorly
confined concretecolumn behaves in a
brittle manner, leading to sudden and
catastrophic failures. Existingreinforced
concrete columns may be structurally
deficient for several reasons: substandard
seismic design details, improper transverse
reinforcement, flaws in structural design,
and insufficient load carrying capacity.
Over the last few years, there has been a
worldwide increase in the use of
compositematerials for the rehabilitation
of deficient reinforced concrete structures.
One importantapplication of this
composite retrofitting technology is the
use of fiber reinforced polymer (FRP)
jackets or sheets to provide external
confinement to reinforced concrete
columns when the existing internal
transverse reinforcement is inadequate.
Reinforced concrete columns need to be
laterally confined in order to ensure large
deformation under load before failure and
to provide an adequate load resistance
capacity. In the case of a seismic event,
energy dissipation allowed by a well- confined concrete core can often save
lives. On the contrary, a poorly confined
concrete column behaves in a brittle
manner, leading to sudden and
catastrophic failures.
EXPERIMENTAL PROGRAM
Specimens were loaded under a monotonic
uni-axial compression load up to failure.
The loadwas applied in a quasi-static
displacement rate of 0.20 mm/min using
an electro–hydraulicuniversal testing
machine which has a vertical load capacity
of 2000 KN. Axial and radialstrains were
measured using an appreciable
extensometer, as seen in Figure 1. Prior to
testing, all GFRP-wrapped specimens were
capped with sulfur mortar at both ends.
For each series of specimen 3, samples
were tested.A total of 23 CFRP-wrapped
and 7 unconfined control concrete
cylinders with a diameter of
150 mm and a height of 300 mm were
prepared and tested under uniaxial
compression loading. The main
experimental parameters were included
wrap thickness and fiber orientation. Four
different wrap thicknesses 0.9, 1.8, 2.7,
and 3.6 mm (1, 2, 3, and 4 layers) and four
fiber orientation of 0o
, 90o
, +45o
, and -45o
with respect to the hoop direction
wereinvestigated. Here Lis for when the
fibers are aligned with the longitudinal
Page 3 of 4
European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 05
May 2019
Available online:https://ejbss.org/ P a g e | 843
axis of the cylinder (90o
) and
Tcorresponds to placing the fibers such
that they are in the hoop direction or
transverse to thelongitudinal axis of the
cylinder (0 o). In addition, D and D' are for
when fibers are alignedwith the diagonal
direction (+45o
) and the inversed diagonal
direction (+135o which is thesame as -45o
).
OBSERVED BEHAVIOR AND TEST
RESULTS
The mechanical behavior of the GFRP
wrapped specimens was very similar in
each series interms of stress strain curves
and failure modes. The rupture of E-glass
fibers marked failureof all confined
specimens. Failure was preceded by some
snapping sounds and was alwaysexplosive
due to the high strain energy stored by the
FRP material. For most specimens, the
externally wrapped E-glass was ruptured
in the longitudinal direction of specimens.
This is probably due to the bi-directional
nature of the glass fiber wrapping, which
has the effect ofredistributing lateral
strains over the full height of the
specimen. For all square prismatic
specimens, the rupture of fibers was
located at or near the corner sections due
to the stress concentration in those regions.
The stress–strain curves of GFRP confined
concrete were bi-linear with a transition
zone. Slopes of the first branch are similar
for plain and confined concrete, governed
almost entirely by the concrete core
properties. The transition zone occurs
shortlyafter the peak strength of the
unconfined concrete (reference specimen)
has been reached.
The slope in the second branch depended
on the confinement level (number of
layers). Moreover, cylinder failure
occurred before the fibers reached their
ultimate strain capacities.Therefore, the
failure occurs prematurely, for the stress
level is appreciably lower than theultimate
strength of the composite. Referring to
Table 4, the rupture of specimen C02
corresponded to a maximum composite
extension eh,rupof 1.15%, which is lower
than thecomposite tensile strain
efu(2.12%) as it represents about 54 % of
it. This reduction is mainlydue to the
curved shape of the composite wrap as
reported in related literature.
CONCLUSIONS
The efficiency of the confinement was
very sensitive to the specimen cross- sectiongeometry and the confining stress
expressed in the number of the GFRP
sheet layersapplied. The best performance
