Post on 18-Aug-2020
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Steel fibres to improve structural performance of reinforced
concrete members
Ass. Prof. I. KOVÁCS University of Debrecen
Hungary
” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
Prof. Gy. L. BALÁZS
University of Technology and
Economics Budapest
Hungary
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
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Steel fibre reinforced concrete
Plain concrete Steel fibre reinforced
concrete
Aggregate
Steel
fibres
Cement
” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
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Observations
Dℓ
F
Tension
Compression
Dℓ/ℓ
s
Dℓ
F
Dℓ
ℓ
F F
Increasing fibre content
Increasing fibre content
” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
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D D
F
F
d
F
d
F F
Observations
Bending
Effect of local force
Increasing fibre content
Increasing fibre content
” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
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Use of SFRC in a cross section
Concrete
Fibre reinforced concrete
Steel fibre
reinforcement in
concrete members
Steel fibre reinforcement in reinforced concrete and
prestressed concrete members
Reinforcing bar
Prestressing
” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
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Use of SFRC in a cross section
Steel fibre reinforcement in the end
block region of prestressed member
Steel fibre reinforcement in repair and
strengthening of concrete members
” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
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Series of reinforced concrete beams
Hooked-end
steel fibres 0 V% 0.5 V% 1.0 V%
No stirrups A1 A2 A3
6/240 A4 A5 A6
6/120 A7 A8 A9
No stirrups
6/240
4/240
150
1800 mm 100 100
6/120
4/120
216
216
216
F
F
F F
F
F
Crimped
steel fibres 0 V% 0.5 V% 1.0 V%
No stirrups B1 B2 B3
4/240 B4 B5 B6
4/120 B7 B8 B9
” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
Reinforcing details
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
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Failure loads and failure modes Crimped steel fibres
D&D® ~ 30/.5
1.0 V%
Fu=44.7kN
0.5 V% Fu=33.6kN
SHEAR FAILURE
COMBINED FAILURE
fc,cube = 48.80 MPa fsp,cyl = 2.81 MPa
fc,cube = 47.16 MPa fsp,cyl = 4.13
MPa
Hooked-end steel fibres
Dramix® ZC 30/.5
NO STIRRUPS Fu=24.2kN
1.0 V%
Fu=35.0kN
0.5 V% Fu=29.0kN
NO FIBRES SHEAR FAILURE
SHEAR FAILURE
SHEAR FAILURE
fc,cube = 39.85 MPa fsp,cyl = 2.62 MPa
fc,cube = 37.58 MPa fsp,cyl = 1.57 MPa
fc,cube = 38.55 MPa fsp,cyl = 3.63 MPa
A1
A2
A3
Fu=21.6kN
NO FIBRES SHEAR FAILURE
fc,cube = 42.70 MPa fsp,cyl = 1.60 MPa
B1
B2
B3
NO STIRRUPS
NO STIRRUPS
NO STIRRUPS
NO STIRRUPS
NO STIRRUPS
” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
9
Failure loads and failure modes Crimped steel fibres
D&D® ~ 30/.5
1.0 V%
4/240 Fu=45.7kN
0.5 V%
4/240 Fu=44.3kN
SHEAR FAILURE
BENDING FAILURE
fc,cube = 48.80 MPa fsp,cyl = 2.81 MPa
fc,cube = 47.16 MPa fsp,cyl = 4.13
MPa
Hooked-end steel fibres
Dramix® ZC 30/.5
6/240 Fu=35.7kN
1.0 V% 6/240 Fu=35.0kN
0.5 V% 6/240 Fu=35.1kN
NO FIBRES SHEAR FAILURE
SHEAR FAILURE
BENDING FAILURE
fc,cube = 39.85 MPa fsp,cyl = 2.62 MPa
fc,cube = 37.58 MPa fsp,cyl = 1.57 MPa
fc,cube = 38.55 MPa fsp,cyl = 3.63 MPa
A4
A5
A6
4/240 Fu=27.5kN
NO FIBRES SHEAR FAILURE
fc,cube = 42.70 MPa fsp,cyl = 1.60 MPa B4
B5
B6
” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
10
Failure loads and failure modes Crimped steel fibres
D&D® ~ 30/.5
1.0 V%
4/120 Fu=45.0kN
0.5 V%
4/120 Fu=46.6kN
SHEAR FAILURE
BENDING FAILURE
fc,cube = 48.80 MPa fsp,cyl = 2.81 MPa
fc,cube = 47.16 MPa fsp,cyl = 4.13
MPa
Hooked-end steel fibres
Dramix® ZC 30/.5
6/120 Fu=37.4kN
1.0 V% 6/120 Fu=36.6kN
0.5 V% 6/120 Fu=35.0kN
NO FIBRES BENDING FAILURE
BENDING FAILURE
BENDING FAILURE
fc,cube = 39.85 MPa fsp,cyl = 2.62 MPa
fc,cube = 37.58 MPa fsp,cyl = 1.57 MPa
fc,cube = 38.55 MPa fsp,cyl = 3.63 MPa
A7
A8
A9
4/120 Fu=35.2kN
NO FIBRES SHEAR FAILURE
fc,cube = 42.70 MPa fsp,cyl = 1.60 MPa B7
B8
B9
” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
11
” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
Crack development
20kN - RC-B7 - 4/120 - 0V% D&D® 30/.5
0.00
0.04
0.08
0.12
0.16
0.20
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Position of crack, x [mm]
w [
mm
]
n = 22, w = 1.450 mm
wm= 0.066 mm, sm= 78 mm
20kN - RC-B9 - 4/120 - 1.0V% D&D® 30/.5
0.00
0.04
0.08
0.12
0.16
0.20
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Position of crack, x [mm]
w [
mm
]
n = 30, w = 1.030 mm
wm= 0.034 mm, sm= 58 mm
B7 B9
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
12
Crack development ” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
0.00
0.04
0.08
0.12
0.16
0.20
Cra
ck
wid
th,
w [
mm
]
2000180016001400120010008006004002000
Position of crack, x [mm]
RC-B9 - 4/120 - 1.0 V% D&D® 30/.5
Fu = 45.0 kN
Bending failure
30 kN
0 kN
F F
fc = 47.16 MPa
fsp = 4.13 MPa
0.00
0.04
0.08
0.12
0.16
0.20
Cra
ck
wid
th,
w [
mm
]
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Position of crack, x [mm]
RC-B7 - 4/120 - 0 V% D&D® 30/.5
Fu = 35.2 kN
Shear failure
30 kN
0 kN
F F
fc = 42.7 MPa
fsp = 1.60 MPa
B7 B9
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r
rm kk.s
2125050
r
rm kk.s
2125045
r
rm kk.s
2125040
Plain concrete
0.5 V% steel fibre content
1.0 V% steel fibre content
Proposal for crack spacing
Crack width
smrmk sw
” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
14
” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
Crack spacing and crack width
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30 35
Force, F [kN]
Me
an
cra
ck
sp
ac
ing
[m
m]
EC2 (No steel fibres)0.5 V% fibre content (Proposal)
1.0 V% fibre content (Proposal)No steel fibre (Measured)
0.5 V% steel fibre (Measured)1.0 V% steel fibre (Measured)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0 5 10 15 20 25 30 35
Force, F [kN]
Me
an
cra
ck
wid
th [
mm
]
EC2 (No steel fibres)
0.5 V% fibre content (Proposal)
1.0 V% fibre content (Proposal)
No steel fibre (Measured)
0.5 V% steel fibre (Measured)
1.0 V% steel fibre (Measured)
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Conclusions ” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
Failure modes and failure loads
1) Steel fibre reinforcement can effectively be used to improve
shear capacity of plain concrete in beams made with no
stirrup reinforcement.
2) If reinforced concrete beams contain the required amount of
conventional shear reinforcement, hence fail in bending, the
addition of fibre does not considerably increase the failure
load.
3) With sufficient amount of fibres the failure mode could be
changed from shear failure to bending failure.
4) Steel fibres do not only increase shear capacity but also
provide substantial post-peak resistance and ductility in
conventional reinforced concrete members
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
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Conclusions ” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
Cracking behaviour
1. Steel fibres in concrete beams provide uniformly
distributed cracks.
2. More cracks developed in beams containing steel fibres
than in case of beams made of plain concrete and
consequently smaller crack spacing was observed.
3. Significant reduction of average crack width was observed
by the use of steel fibres.
4. Cracking characteristics was not significantly effected by
the type of fibre.
5. A modification to the crack spacing formula by EC2 was
developed in order to consider the effect of steel fibres.
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
17
Structural application of model
” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
ARCHI STAT LTD.
Architectural & Structural Design Bureau
Nyiregyháza, Hungary
Zsolt KASSAI DLA architect
Imre KOVÁCS PhD structural engineer
FREE SHAPE SENDWICH SHELL
HOUSES
Egerszalók, HUNGARY
Patented building technology for
sendwich shells
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
18
Steel fibres to improve structural performance of reinforced
concrete members
Ass. Prof. I. KOVÁCS University of Debrecen
Hungary
” SteelFibres to Improve Structural Performance of Reinforced Concrete Members” by Prof. György L. Balázs TU Budapest and Ass. Prof. Imre Kovács UD
Prof. Gy. L. BALÁZS
University of Technology and
Economics Budapest
Hungary
„Structural Concrete and Time” fib Symposium La Plata Argentina September 28. – September 30. 2005
THANK YOU FOR YOUR KIND ATTENTION!