PARAMETRIC STUDY OF GLASS FIBRE REINFORCED POLYMER (GFRP) STRENGTHENED CONCRETE COLUMN UNDER ECCENTRIC COMPRESSION LOAD

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 08 | Aug 2023 www.irjet.net p-ISSN: 2395-0072
PARAMETRIC STUDY OF GLASS FIBRE REINFORCED POLYMER (GFRP)
STRENGTHENED CONCRETE COLUMN UNDER ECCENTRIC
COMPRESSION LOAD
Ajay Kumar, Deepak Tarachandani
Applied Mechanics Department
L. D. College of Engineering Ahmedabad
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ABSTRACT: The study investigated the performance of
reinforced concrete columns that were strengthened
using GFRP materials when subjected to eccentric
loading. Eccentric loading refers to the application of a
load that is not centrally located, causing an off-centre
force on the column. This type of loading is known to
introduce additional challenges and stress
concentrations in the column.
The objective of the research was to evaluate the
effectiveness of GFRP strengthening in improving the
performance of reinforced concrete columns under
eccentric loading. The researchers conducted FEA
analysis on a series of reinforced concrete columns, with
various parameters such as length, cross section,
eccentricity, end condition and varied spacing of stirrups
to compare their ultimate load carrying capacity and
displacement.
Finite Element Analysis (FEA) is employed to simulate
the behaviour of GFRP-strengthened concrete columns.
The numerical models are validated against
experimental results obtained from laboratory tests
conducted on prototype specimens. The study
investigates the influence of each parameter on the
ultimate load carrying
capacity and displacement of the columns, aiming to
identify the optimal configuration for GFRP
strengthening.
Overall, the research demonstrated the potential of GFRP
strengthening in enhancing the behaviour and
performance of reinforced concrete columns subjected
to eccentric loading. These findings can contribute to the
development of improved design guidelines and
strategies for strengthening existing structures or
designing new ones with increased resistance to
eccentric loading effect.
Key words: GFRP, Eccentric loading, Strengthening.
1. INTRODUCTION: When exposed to a humid
environment, the steel bars in reinforced concrete (RC)
structures experience a decline in their mechanical
properties, resulting in reduced load-carrying capacity
and serviceability. To prevent corrosion and degradation,
protective measures are necessary, but they can come
with a significant upfront cost.
Glass fiber reinforced polymer (GFRP) bars are
considered the optimal alternative to steel bars due to
their high tensile strength, lightweight nature, low
density, and excellent electromagnetic resistance. Most
importantly, they possess superior corrosion resistance.
Fiber Reinforced Polymers (FRP) were originally created
for the aerospace industry and later adopted by the
automotive industry. However, their superior
characteristics in comparison to other materials made
them a preferred choice for civil engineering applications
over time.
When it comes to research on FRP-confined concrete
columns, the focus is typically on studying the stress-
strain relationship of these columns, observing how they
behave under eccentric load, and evaluating their seismic
performance.
Since most columns in structures are subjected to
eccentric loads, the study of the behaviour of FRP-
confined reinforced concrete columns under such loads
holds greater significance.
2. FINITE ELEMENT MODELLING: Numerical
simulations of GFRP reinforced concrete columns were
done by using software ABAQUS. During the modelling of
specimens, the concrete material models, boundary
conditions, and different geometric and material
parameters. The concrete material was modelled as a
homogeneous 3D solid section. Diameter of main
reinforcement is 25 mm and diameter of stirrups is 8
mm.
In total 48 number of models were prepared and
the variable in models are length, end condition, cross
sectional dimension, eccentricity and varied stirrup
spacing.
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For considering the variation in eccentricity 12
models were prepared in which three eccentricities of 0
mm, 100mm and 175mm are considered for two
different length and for two different end conditions but
having same cross-sectional dimension. For same
eccentricities 12 models were also
prepared having different cross-sectional dimension
(400 x 400mm).
As per the provision of IS 13920 for special
confining reinforcement a stirrup spacing of 85mm in
top and bottom 450 mm and a spacing of 100mm in
middle portion of column is taken for that 24 models
were prepared having variation in length, eccentricity,
cross sectional dimension and end condition of column
but having two layers of hoop GFRP.
To determine the axial load-deflection history of
reinforced concrete columns up to failure, a static
monotonic loading was applied on the top by the
displacement control technique. An induced
displacement of 20mm was applied on the top centre of
concentric columns and at a distance equal to required
eccentricity from the centre of specimens along the
weaker axis of eccentric columns. The geometry and the
modelling details of the finite element models of steel-
reinforced columns are shown in Figure 1.
Table 1 Variables in modelling of column
Parameter Value
Density of concrete (ton/mm3) 2.4 x 10-9
Poisson’s ratio 0.2
Youngs modulus (N/mm2) 26587
Concrete cover (mm) 40
Initial and maximum increment size of the loading 0.01
Minimum increment size 10-10
Table 2 Element intricacies
Length
(mm)
End condition Eccentricity
(mm)
Cross section
(mm)
Spacing of stirrups
3500 Both ends hinged 0 350 x 350 Constant spacing of 100mm
2500 Both ends fixed 100 400 x 400 Varied spacing of stirrups
175
Figure 1 A typical steel reinforced concrete column strengthened with two layers of hoop wrapping

3. FEA Model Results:
Figure 2 Ultimate load carrying capacity of 3.5 m column having both ends fixed and cross section of 350 x 350 mm with
different eccentricity
Figure 4 Ultimate load carrying capacity of 3.5 m column having both ends hinged and cross section of 400 x 400 mm with

Figure 6 Ultimate load carrying capacity of 3.5 m column having both ends hinged and cross section of 350 x 350 mm
having varied spacing of stirrups with different eccentricity
Figure 9 Ultimate load carrying capacity of 2.5 m column having both ends fixed and cross section of 350 x 350 mm having
varied spacing of stirrups with different eccentricity

4. Conclusion:
It can be concluded that by using GFRP under eccentric
loading for different length of column and same cross
section does not increase the load carrying capacity as
much but it significantly reduces the displacement by
13.5 % for concentric loaded column.
By changing the end condition from hinged to fixed, the
load carrying capacity of the GFRP strengthened RC
column is increased by 2.78 % for 100 mm eccentricity
and displacement is reduced by 3.14 % for 175 mm
eccentricity with respect to column having both ends
hinged.
The load carrying capacity of GFRP strengthened RC
column under eccentric loading is increased by 3.46 %
for column having larger cross section as compared to
smaller cross section.
By reducing the length of column by taking same cross
section and end condition the load carrying capacity is
increased by 4.77 % for 100 mm eccentricity
significantly but very less for 175 mm eccentricity and
displacement is also reduced by 7.46 % for 100 mm
eccentric loading.
GFRP strengthened RC column under eccentric loading
having varied spacing of stirrups along the length of
column significantly reduces the displacement by 20 %
under 100 mm eccentric loading for smaller length of
column.
The ultimate load carrying capacity is increased by 3.15
% and displacement is reduced by 10.16 % for
concentric loading by changing the spacing of stirrups
for smaller length of column under both ends hinged
condition.
For column having cross section 350 x 350 mm having
both ends fixed does not enhance load carrying capacity
significantly but it reduces the displacement by 1.54 %
under 175 mm eccentric loading by reducing the length
of column.
For column having cross section 400 x 400 mm and both
ends fixed reduces the displacement by 2.87 % and there
is negligible change in ultimate load carrying capacity
under concentric loading by reducing the length of
column.
So, it is better to use GFRP for smaller length of column
under small eccentric loading and larger cross section.
GFRP also enhances the load carrying capacity when the
spacing of stirrups is varied along the length of column.
5. References:
1. Behaviour of GFRP strengthened Reinforced Concrete Columns under Large Eccentric Compression Load” by
Advanced Materials Research Wang, Yongfeng Wang, Suyan Wang.
2. Finite element analysis of rectangular reinforced concrete columns wrapped with FRP composites by Abdurra’uf
M Gora1, Jayaprakash Jaganathan, M P Anwar, U Johnson Alengaram.
3. The effect of FRP characteristics on the behaviour of square columns under eccentric loads by Hiwa Noamani,
Arash Sayari.
4. Tests of glass fibre reinforced polymer rectangular concrete columns subjected to concentric and eccentric axial
loading by Mohamed Elchalakani, Guowei Ma.
5. Numerical Investigation of Load-Carrying Capacity of GFRP-Reinforced Rectangular Concrete Members Using CDP
Model in ABAQUS by Ali Raza, Qaiser uz Zaman Khan, and Afaq Ahmad.
6. Compression behaviour of FRP-strengthened RC square columns of varying slenderness ratios under eccentric
loading Nadeem Siddiqui, Husain Abbas, Tarek Almusallam, Abobaker Binyahya, Yousef Al-Salloum.
7. Experimental and numerical study on the structural behaviour of eccentrically loaded GFRP columns by F. Nunes
a, M. Correia b, J.R. Correia a, N. Silvestre a, n, A. Moreira.
8. Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures.
9. Design recommendations for the use of FRP for reinforcement and strengthening of concrete structures by S.
Rizkalla, T. Hassan, and N. Hassan.

10. Experimental and numerical study on the structural behaviour of eccentrically loaded GFRP columns by F. Nunes,
M. Correia, J. R. Correia, N. Silvestre, and A. Moreira.
11. Tests of glass fibre reinforced polymer rectangular concrete columns subjected to concentric and eccentric axial
loading.
12. Nonlinear finite element modelling of concrete confined by fiber composites by A. Mirmiran, K. Zagers, and W.
Yuan.
13. 3D finite element analysis of substandard RC columns strengthened by fiber-reinforced polymer sheets by A. I.
Karabinis, T. C. Rousakis, and G. E. Manolitsi.
14. Experiments and finite element analysis of GFRP reinforced geopolymer concrete rectangular columns subjected
to concentric and eccentric axial loading by M. Elchalakani, A. Karrech, M. Dong, M. S. Mohamed Ali and B. Yang.
15. Behaviour of full-scale glass fiber-reinforced polymer reinforced concrete columns under axial load by De Luca A,
Matta F, Nanni.
16. IS: 456 – 2000, IS: 13920 – 2016, IS: 800 – 2007.

PARAMETRIC STUDY OF GLASS FIBRE REINFORCED POLYMER (GFRP) STRENGTHENED CONCRETE COLUMN UNDER ECCENTRIC COMPRESSION LOAD

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