Volume 05 Issue 07-2025
41
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
05
ISSUE
07
Pages:
41-50
OCLC
–
1368736135
A
BSTRACT
This paper presents the experimental test results of hybrid steel
–
glass fiber reinforced polymer (GFRP)
reinforced concrete beams under four-point bending, and compares them with conventional steel
reinforced concrete beams.
K
EYWORDS
Concrete, reinforced concrete beam, GFRP bar, steel bar, crack resistance, deflection, ultimate load,
ultimate moment, cracking moment.
I
NTRODUCTION
In the construction industry, the long-term
durability of reinforced concrete structures is
considered one of the pressing issues. In reinforced
concrete structures, the deterioration of concrete
can lead to the exposure of steel reinforcement, and
the slow penetration of oxygen from the air
through cracks results in the formation of iron
oxide in the steel reinforcement, which is primarily
composed of iron [1
–
3].
The use of FRP reinforcement as an alternative to
steel reinforcement in reinforced concrete
structures has emerged as an innovative
advancement in construction. Its advantages such
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Research Article
Flexural Behaviour Of Hybrid Steel-Frp Reinforced Concrete
Beam
Submission Date:
May 31,
2025,
Accepted Date:
June 29, 2025,
Published Date:
July 31, 2025
Crossref doi:
https://doi.org/10.37547/ijasr-05-07-05
Kamoliddin Muminov
PhD student, Namangan State Technical University, Uzbekistan
Ravshanbek Mavlonov
PhD, Namangan State Technical University, Uzbekistan
Volume 05 Issue 07-2025
42
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
05
ISSUE
07
Pages:
41-50
OCLC
–
1368736135
as resistance to corrosion, absence of magnetic
field generation, and non-conductivity of electricity
are expanding its field of application. In addition,
the high tensile strength and lightweight nature of
composite polymer reinforcements make them
increasingly attractive [4
–
6].
However, their tensile behavior follows a linear
pattern and remains linear up to failure. As a result,
concrete structures reinforced with composite
polymer reinforcement are prone to brittle failure
without any prior warning. Due to this factor,
design codes require an excessive amount of
reinforcement in concrete elements reinforced
with composite materials, in order to reduce the
probability of failure and minimize deformation.
However, this approach is not economically
justified [7
–
8].
The low modulus of elasticity of composite
polymer reinforcements causes greater deflection
and wider crack openings in flexural concrete
elements compared to those reinforced with steel
reinforcement of the same cross-section and
quantity. Consequently, some challenges arise
when calculating the serviceability limit states
(SLS) of concrete beams reinforced with composite
polymer reinforcement [9, 10, 11].
To address these issues, the idea of hybrid
reinforcement of flexural elements using both steel
and composite polymer reinforcements has
emerged. The most effective solution involves
placing the composite polymer reinforcement at
the bottommost part of the tensile zone with the
smallest protective concrete cover. In this
arrangement, the steel reinforcement is embedded
deeper inside the concrete, beneath the composite
polymer reinforcement, thereby reducing its
susceptibility to corrosion by increasing the
protective concrete layer [1, 4, 6, 10].
As a result, the steel reinforcement contributes less
to the load-bearing capacity of the element but
plays a crucial role in providing ductility and
flexibility [3, 8, 12, 13, 14]. Moreover, the presence
of steel reinforcement helps reduce the number
and width of cracks. Therefore, the combined use
of steel and composite reinforcement enhances the
durability and service life of reinforced concrete
beams compared to conventional reinforced
concrete [10, 15, 16].
Concrete cube specimens and their strength
Portland cement, sand, crushed stone, and water
were used to prepare the specimens for the
experimental study.
Volume 05 Issue 07-2025
43
International Journal of Advance Scientific Research
(ISSN
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2750-1396)
VOLUME
05
ISSUE
07
Pages:
41-50
OCLC
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1368736135
Fig. 1. Sand used for the concrete mix
Fig. 2. Crushed stone used for the concrete mix
To determine the compressive strength of the
concrete,
cube
specimens
with
nominal
dimensions of 100×100×100 mm were prepared in
four different series in accordance with the
international standard requirements of GOST
10180-2012. The concrete mixes were placed into
specially prepared molds (fig. 3), paying close
attention to the specified requirements and the
compaction of the concrete mix. The prepared cube
specimens were labeled and cured under normal
conditions for 28 days.
Fig. 3. Prepared cube specimens
Volume 05 Issue 07-2025
44
International Journal of Advance Scientific Research
(ISSN
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2750-1396)
VOLUME
05
ISSUE
07
Pages:
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OCLC
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Table 1. Results obtained from compressive strength testing of concrete cube specimens
No
Cube
specimen
series
Size
a×b×h
, mm
Ultimate
load
P
, kN
Specimen
strength,
R
i
MPa
а
Average
strength,
R
m
MPa
Normative
strength
R
n
,
MPa
Concrete
grade
Modulus of
elasticity
Е
,
MPa
1
Day 1,
Series 1
102х100х101
377,89
35,9
34,4
31,2
B30
30449
2
100х101х99
349,47
33,2
3
100х102х100
358,95
34,1
4
Day 1,
Series 2
100х99х101
383,16
36,4
34,9
31,7
B30
30568
5
102х101х101
346,32
32,9
6
100х100х99
372,63
35,4
7
Day 1,
Series 3
100х101х101
386,32
36,7
33,3
30,2
B30
30097
8
99х100х101
344,21
32,7
9
100х101х100
321,05
30,5
10
Day 2
101х101х101
383,16
36,4
33,9
30,8
B30
30124
11
102х101х99
324,21
30,8
12
99х100х100
363,16
34,5
Geometric dimensions and reinforcement of
the beams
For testing purposes, a total of 27 beams across 9
different series were prepared, each with a length
of l=150 cm and an effective span of l
₀
=140 cm. The
cross-sectional dimensions of the beams were
b×h=15×20 cm. The concentrated load was applied
at a distance of l₀/3 from the supports. The
distance from the edge of the beam to the support
was 5 cm. All beams were tested under four-point
bending (fig. 4a).
Volume 05 Issue 07-2025
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VOLUME
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Fig. 4. Geometric dimensions of the beam (a) and reinforcement cage (b)
The beams were reinforced using prefabricated
reinforcement cages. Since the beams were tested
under normal cross-section bending, no transverse
(shear) reinforcement was placed in the middle
span of the beams. In the support zones, the
spacing of the stirrups was set to 5 cm.
The length of the reinforcement cage was 145 cm,
and its height was 18 cm. In all beams, two Ø8 A-III
reinforcement bars were placed in the
compression zone. Ø6 A-I steel bars were used as
stirrups (fig. 4b).
Volume 05 Issue 07-2025
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International Journal of Advance Scientific Research
(ISSN
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VOLUME
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Fig. 5. Cross-sections of experimental beams and layout of reinforcement cages
B3-1S12-2G12
B6-2S10-2G12
c)
Volume 05 Issue 07-2025
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International Journal of Advance Scientific Research
(ISSN
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2750-1396)
VOLUME
05
ISSUE
07
Pages:
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OCLC
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B8-3S10-2G10
B9-2S10-3G10
Fig. 6. Failure modes of beams under applied loading
As a result of the experimental tests, the failure of
hybrid steel
–
composite reinforced concrete beams
corresponded to Failure Mode 4. This mode is
considered the closest to real-life structural
behavior. In Modes 1, 2, and 3, the longitudinal
reinforcement area relative to the beam’s cross
-
section is insufficient, while in Modes 5 and 6, the
Volume 05 Issue 07-2025
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(ISSN
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2750-1396)
VOLUME
05
ISSUE
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Pages:
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reinforcement is considered excessive, which is not
commonly used in construction practice.
In Mode 4, after the stress in the steel
reinforcement reached its yield strength, crushing
of the concrete in the compression zone was
observed. However, the glass composite
reinforcement did not rupture. The fact that the
composite reinforcement remained intact allowed
the beam to continue to behave elastically even
after reaching its ultimate load-bearing capacity. In
other words, upon unloading, a significant
recovery of deflection in the beam was observed.
Strength and crack resistance of the beams
Table 2 compares the theoretical calculations,
experimental test results, and ANSYS simulation
results of the cracking moment for the tested
beams. Additionally, the values of the applied load
at which the first visible cracks appeared in the
beams are presented.
Table 2. Crack resistance moment values in beam specimens
Beam notation
Ultimate
load P
u
, kN
Deflection
f
, mm
exp
crc
M
, kN
‧
m
exp
u
M
, kN
‧
m
exp
exp
/
u
crc
M
M
B1-3S12
109.7
29.9
4.61
25.60
0.18
B2-1S12-2G10
107.3
28.1
4.26
25.04
0.17
B3-1S12-2G12
119.6
30.2
4.47
27.91
0.16
B4-4S12
135.3
29.7
5.37
31.57
0.17
B5-2S12-2G12
138.1
23.4
4.83
32.22
0.15
B6-2S10-2G12
121.5
29.8
4.25
28.35
0.15
B7-5S10
116.2
25.0
5.15
27.11
0.19
B8-3S10-2G10
129.7
29.7
4.84
30.26
0.16
B9-2S10-3G10
118.1
28.1
4.41
27.56
0.16
According to the experimental test results of the
beams, crack formation in beams reinforced with
steel reinforcement developed later compared to
hybrid-reinforced beams. That is, the first visible
cracks were observed when the beam carried 17
–
19% of its ultimate load-bearing capacity.
However, in the hybrid-reinforced beams, this
value was 15
–
17% (table 2).
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