PERFORMANCE OF CARBON FIBER AS LATERAL TIES IN SHORT AXIALLY LOADED CONCRETE COLUMNS

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International Journal of Civil Engineering and Technology (IJCIET)
Volume 7, Issue 3, May–June 2016, pp. 122–128, Article ID: IJCIET_07_03_012
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PERFORMANCE OF CARBON FIBER AS
LATERAL TIES IN SHORT AXIALLY
LOADED CONCRETE COLUMNS
Faheemuz Zafar
Structural Engineering
Department of Civil Engineering, Integral University, Lucknow, India
Zishan Raza Khan
Associate. Professor
Sabih Ahmad
Associate. Professor
ABSTRACT
An experimental program to investigate the structural performance of
CFRP as lateral tie in concrete column is conducted. The experimental
program consist of twenty one number of column fabricated and tested
experimentally under axial load. Specimens were divided into four groups and
each group except group 1 consists of six columns. Group 1 consist of
reference columns; three plain concrete and six specimen reinforced with steel
reinforcement. Group 2 columns were reinforced with CFRP lateral tie and
columns of group 3 were reinforced with CFRP lateral ties except end ties to
solve fabrication issue. Size of all the columns was kept same, 600 mm in
height and 150 in mm diameter. Results shows a significant increase in axial
capacity of column tied with CFRP lateral ties. Column with end steel ties
shows similar behaviour as CFRP tied column.
Key words: CFRP. Lateral tie, Strength, Strain
Cite this Article: Faheemuz Zafar, Zishan Raza Khan, Sabih Ahmad,
Performance of Carbon Fiber as Lateral Ties in Short Axially Loaded
Concrete Columns, International Journal of Civil Engineering and
Technology, 7(3), 2016, pp. 122–128.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=7&IType=3

Performance of Carbon Fiber as Lateral Ties in Short Axially Loaded Concrete Columns
BACKGROUND
Limited studies have been reported on the use of FRP bars as lateral reinforcements in
the compression members. Corrosion resistance, light weight, high tensile strength of
Carbon Fiber Reinforced Polymer have made them a competitive option as
reinforcing material especially in aggressive environment.
Hany Tobbi et al (2012) [6] investigate column reinforced with Glass Fiber
(GFRP) and Carbon Fiber (CFRP) as longitudinal bar and lateral ties. Based on test
results it was found that FRP ties significantly increased concrete strength and
ductility. Antony De Luca et al 2009 [3] investigate the behaviour of column
internally reinforced with GFRP bar. It was found that the failure mode was strongly
influenced by the spacing of the GFRP ties. Alsayed et al. (1999) [2] investigated the
effect of replacing longitudinal and lateral steel with an equal amount of GFRP bar it
was observed that replacing steel ties with GFRP ties reduced the axial capacity of the
column by about 10%.
INTRODUCTION
The use of Fiber Reinforced Polymer (FRP) in civil engineering practice is increasing
day by day. Although many researchers and practitioners have demonstrated potential
of its application in various civil engineering aspect, mostly of them rally on its use as
an alternative of retrofitting material.
The Reinforced Concrete column as vertical member transmit axial compression
load with or without moment to the substructure are of great importance for safety of
structure [7]. These columns are conventionally reinforced with steel longitudinal bar
and lateral ties. Corrosion of steel reinforcement is a very big problem due to presence
of salt, chemical or other industrial wastes. Lateral ties are generally located as an
outer reinforcement with respect to longitudinal reinforcement and therefore are more
susceptible to severe environment effects due to minimum cover provided. The use of
FRP as lateral tie in column has not yet been fully explored. Considerable research
works have been reported on the use of CFRP as internal reinforcement. This leads
improve our knowledge of behaviour of FRP RC member, on the other hand, the
behaviour of FRP RC compression members has not yet defined. This leaves a
research gaps in need of valuable investigations to introduce appropriate provisions in
guidelines. Direct replacement of steel with FRP is not possible due to their difference
in mechanical properties. Several codes and design guidelines (ACI 440.1R.06,
CAN/CSA S6-06, CAN/CSA S806-12 Canadian Code) [1][4][5] have been issued and
developed around the world on the structural use of FRP as reinforcing material. On
the other hand, limited studies have been reported on the use of FRP bars as vertical
and lateral reinforcements in the compression members. Extensive research has been
reported on the use of FRP material as repairing material. The current investigation
aims to evaluate the use of CFRP as lateral reinforcement in column.
RESEARCH SIGNIFICANCE
The scope of this study consists of experimental investigation of CFRP material as
lateral ties in short axially loaded compression member. For understanding the
behaviour of FRP tied RC column construction, instrumentation and testing of three
group of column with different tie configuration have been conducted. The present
study will attempt to increase the understanding of CFRP confined compression
member.

Faheemuz Zafar, Zishan Raza Khan, Sabih Ahmad
EXPERIMENTAL PROGRAMME
The research investigation was conducted to evaluate the behaviour of the circular
concrete columns internally reinforced with steel longitudinal bars and CFRP lateral
ties. Two types of reinforcing bars were used in this study to reinforce the specimen.
Conventional Fe500 (yield strength of 500 MPa) deformed bar of 8 mm diameter
were used as longitudinal reinforcement. Plain bars with 6 mm diameter and Fe250
grade (yield strength of 250 MPa) were used as lateral ties.
Three groups of concrete column with different reinforcement type were tested
under axial compressive load. Size of all the specimen kept same, 600 mm in height
and 150 mm in diameter, with a cover of 12.5 mm provided. For each group except
group 1 six columns were cast and wet cured for 28 days before testing. All the
specimens were reinforced with Fe500 (yield strength of 500 MPa) longitudinal steel
rebar of 8 mm diameter. Group 1 include control specimen of three plain columns (P)
without reinforcement and six steel RC specimens (S6F0). Control specimen group 1
of columns were reinforced with Fe250 grade (yield strength of 250 MPa) plain bar of
6 mm diameter lateral ties with pitches of 100 mm. In the second group of columns all
the steel lateral ties were replaced with CFRP rectilinear ties of size 0.5×20 mm
(S0F6). Pitch of lateral ties kept same as steel ties in control specimen. While in third
group of columns all the steel lateral ties except corner two were replaced by CFRP
ties (S2F4). Size of all the specimens kept same, measured 150 mm in diameter and
600 mm in height. A cover of 12.5 mm was provided in each specimen.
Table Specimen details
Specimen
ID
Longitudinal Reinforcement Lateral Reinforcement
% No. of bars Bar size Area Pitch
P - - - - -
S6F0 1.7 6#8 mm 6 mm 28.26 100
S2F4 1.7 6#8 mm 6& (0.5×20) 28.26&10 100
S0F6 1.7 6#8 mm (0.5×20) mm 10 100
Unidirectional CFRP of 0.22 mm thickness is used, which is increased to 0.5 mm/
ply by pasting two layers with epoxy resin. Rectilinear CFRP rings were made of
cross section 0.5×20 mm by cutting the sheet in fiber direction. An overlap length of
100 mm is provided as per ASTM code.
Figure CFRP rings

Table 3-2 Mechanical Properties of CFRP as provided by the manufacturer
Density (gm/cm3
) 1.8
Tensile Strength (MPa) 4000
Tensile Modulus (GPa) 240
Elongation (%) 1.7
Cages of different reinforcement type were assembled as shown in figure. Steel
cylindrical moulds were used as formwork for casting of samples. The concrete of
M25 grade nominal mix was used for all samples. Concrete was poured into the
moulds from top in approximately three layers, tamping rod was used to consolidate
concrete and remove air bubble. Three standard cube of 150×150 mm size were
prepared and cured in the same condition for 28 days to determine actual strength of
concrete.
Figure Assembled cages Figure Test setup overview
TEST RESULTS
Table shows the results of the specimens experimental tested. Different modes of
failure were observed for plain and reinforced specimens tested in this study. Plain
concrete column fail suddenly after attaining its peak load significantly less load than
other confined columns. The failure of the plain specimen started with hair line crack
and then sudden failure at that point due absence of longitudinal reinforcement.
The general behaviour of confined concrete column was comparatively ductile
and complex unlike plain concrete column specimen. Failure of these column were
characterized sequentially by the development of surface cracks, cover spalling,
yielding of longitudinal steel, yielding of lateral steel, fracture of ties, buckling of
longitudinal bars and crushing of concrete core. The vertical cracks were noticed first
of all for all the specimen before spalling of cover, which was marked by separation
of large piece of cover from concrete core. The CFRP confined RC column failed in a
brittle manner

Table Test Results
Specimen f ʹc Axial Load
Pmax
Axial Strain
ɛc
P 25.3 372.5 -
25.6 376.5 -
26.8 406.2 -
S6F0 25.3 565.3 0.0133
25.6 566 0.0134
26.8 582.2 0.0136
S0F6 25.5 751.7 0.0161
25.9 753.2 0.0158
26.6 758.5 0.0153
S2F4 25.5 756 0.0153
25.9 757.1 0.0151
26.6 759 0.0156
Strain of lateral ties could not be observed as strain gauges were installed at
middle portion of column, while failure of specimen occurred at end of column.
Failures of all the columns were observed at a distance 150 to 250 mm (d (diameter)
to 2d of column) from end of column.
Figure Spalling of cover and buckling Figure Cracking appearance of specimen of
longitudinal bar

Load vs. Deflection curves for S6F0 specimen
0
100
200
300
400
500
600
0.52.54.56.58.5
Load
Deflection
Deflection
Deflectio
n
0
100
200
300
400
500
600
0.1
1.5
3
4.5
6
7.5
8.8
Deflection
Deflectio
n
0
200
400
600
800
0.1 2 4.16.38.6
Load
Deflection
Deflection
Deflectio
n
0
200
400
600
800
0.1 2 4 6 8
Load
Deflection
Deflection
Deflection
0
200
400
600
800
0.1 2.7 5.9 8.3
Load
Deflectio
Deflection
Deflectio
n
0
200
400
600
800
0.1 2 4 6 8
Load
Deflection
Deflection
Deflection

CONCLUSION
To analyse the behaviour of CFRP confined RC column 21 specimens with different
confinement were subjected to axial compression observed. Following observations
were recorded.
 A significant increase in axial capacity of CFRP confined specimen was observed
 Failure of CFRP confined column attribute to crushing of concrete core and rupture
of CFRP lateral tie.
 Failure of CFRP confined column was brittle that can be avoided by reducing tie
spacing.
 Failure of specimens were at a distance 150 mm (diameter of column), reducing tie
spacing at that region will eventually increase strength of column.
 The test observation indicates that at both end of column steel tie can be used to
overcome from fabrication issue without any strength loss.
REFERENCES
[1] American Concrete Institute (ACI) Committee 440, [2006]. Guide for the
Design and Construction of Concrete Reinforced with FRP Bars, ACI 440.1R-
06, Farmington Hills, Mich
[2] Alsayed, S. H.; Al-Salloum, Y. A.; Almusallam, T. H.; and Amjad, M. A, 1999,
“Concrete Columns Reinforced by GFRP Rods,” Fourth International
Symposium on Fiber-Reinforced Polymer Reinforcement for Reinforced
Concrete Structures, SP-188, C.W.Dolan, S.H. Rizkalla, and A. Nanni,
American Concrete Institute, Farmington Hills, Mich., pp. 103 112.
[3] Antonio De Luca, Fabio Matta, Antonio Nanni. “Behavior of Full-Scale
Concrete Columns Internally Reinforced with Glass FRP Bars under Pure Axial
Load” Composites & Polycon 2009, American Composites Manufacturers
Association. January 15-17, 2009
[4] Canadian Standards Association (CSA), [2006- S6S1-10 Edition 2010].
Canadian Highway Bridge Design Code—(Section 16), CAN/CSA-S6-06,
Rexdale, Toronto.
[5] Canadian Standards Association (CSA), [2012]. Design and Construction of
Building Components with Fiber Reinforced Polymers, CAN/CSAS806-12,
Rexdale, Toronto.
[6] Hany Tobbi, Ahmed Sabry Farghaly, and Brahim Benmokrane, “Strength Model
for Concrete Columns Reinforced with Fiber-Reinforced Polymer Bars and
Ties” ACI Structural Journal. MS No. S-2012-364.R3
[7] Prof. Dr. Nameer A. Alwash and Ahmed Hamid Jasim, Behavior of Short
Concrete Columns Reinforced by CFRP Bars and Subjected To Eccentric Load,
International Journal of Civil Engineering and Technology, 6(10), 2015, pp. 15–
24.
[8] H.Taibi Zinai, A. Plumier, D. Kerdal, Computation of Buckling Strength of
Reinforced Concrete Columns by The Transfer-Matrix Method, International
Journal of Civil Engineering and Technology, 3(1), 2012, pp. 111–127.
[9] Dr. Salim t. Yousif, New Model of CFRP-Confined Circular Concrete Columns:
Ann Approach, International Journal of Civil Engineering and Technology,
4(3), 2013, pp. 98–110.
[10] Mohammad M. Zaki M. Afifi, “Behavior of Circular Concrete Columns
Reinforced With FRP Bars and Stirrups” PhD Thesis. December 2013

PERFORMANCE OF CARBON FIBER AS LATERAL TIES IN SHORT AXIALLY LOADED CONCRETE COLUMNS

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