FINITE ELEMENT MODELING, ANALYSIS AND VALIDATION OF THE FLEXURAL CAPACITY OF RC BEAMS MADE OF STEEL FIBER REINFORCED CONCRETE (SFRC)

AHSANULLAH UNIVERSITY OF SCIENCE
AND TECHNOLOGY (AUST)
PAPER ID: SEE 051
FINITEELEMENT MODELING, ANALYSISAND VALIDATIONOF THE
FLEXURALCAPACITYOF RC BEAMSMADE OF STEELFIBER REINFORCED
CONCRETE(SFRC)
Presented by
Sadia Mannan Mitu
Department of Civil Engineering
Ahsanullah University of Science
and Technology (AUST),
Dhaka 1208, Bangladesh
Co-Authors:
Md. Mashfiqul Islam
Mohammed Shakib Rahman
Md. Serajus Salekin
Md. Rakibul Islam

CONTENTS
 Introduction of SFRC
 Experimental program and strategy
 FE modeling and analysis
 Evaluation of FE reults
 Conclusion

WHAT IS SFRC?
SFRC
STEEL
FIBRE
REINFORCED
CONCRETE

COMPONENT OF SFRC
SFRC
Constituents of
portland cement
Dispersion of
short
Descrete
Steel Fibre
Fine agg. &
Coarse agg.

ADVANTAGES OF SFRC
SFRC
ADVANTAGES
Enhancement of
ductility and
energy
absorption
capacity
Improve internal
tensile strength
of the concrete
due to bonding
force.
Increase the
flexural
strength , direct
tensile strength
and fatigue
strength.
Enhance shear
and torsional
strength
Shock
resistance as
well as
toughness of
concrete

PC(REINFORCED) VS SFRC
PC
(Reinforced)
SFRC

MECHANISM OF SFRC
Fibers distribute
randomly and act
as crack arrestors.
•When steel fibers are
added to a concrete mix :
changing concrete from a
brittle material to a
ductile one, in addition
to improving toughness
and rigidity
Increases the
ductility by arresting
crack and prevents
the propagation of
cracks by bridging
fibers.
Mechanism of fiber in flexure
(a) Free area of stress.
(b) Fiber bridging area.
(c) Micro-crack area.
(d) Undamaged area.

OBJECTIVE
Select
suitable &
available
type of steel
fiber
Investigate various
shear capacity
enhancements
of concretes
using the SF
Observe
Failure
patterns
Construct FE
models for PC
and SFRC
with ANSYS
Above all to
provide the
construction
industry of
Bangladesh with
reliable
experimental data
and validated FE
modeling about
this engineering
material.

EXPERIMENTAL PROGRAM AND STRATEGY
Experimental strategy
Experimental program
Specimen preparation
Testing and data acquisition
Investigation of failure pattern
FE modeling through optimizing the basic
engineering properties
FE analysis applying experimental loading environment and
displacement boundary conditions
Validation of FE models and analyses with experimental
results and failure modes

Typical Steel Fibers

120°
120°
120°
Effective length=1.85in (47.2mm)
Steel fiber aspect ratio 40
0.4in(10mm)
0.4in(10mm)
0.4in(10mm)
Diameter=0.04in (1.18mm)
Circular
cross
section
Original length=2.65in (67.2mm)
(a)
(b)
Figure 3: (a) Size and geometry of steel fibers (b) image of fibers

Figure 4 : (a) Preparation of steel fibers (b) steel fibers of different
aspect ratio.
(a) (b)

Aggregates
Crushed stone is used as aggregate in this research.
Different types of aggregate are shown in Figure 5.
Figure 5: (a) Stone aggregate (CA) and (b) Sand (FA)
(a) (b)

Clear span = 2.5'
Beam length = 3'
5"
6"
10mm
@2.5" c/c
Figure 1: Stirrup strategy.
Figure 2: Experimental strategy on
flexural beams.

Figure 7: Horizontal data acquisition
system via DICT.
Figure 6: Experimental setup for shear
critical beam in the UTM.

Images of Experimental Testing of Simply Supported RC Beam

0
1000
2000
3000
4000
5000
0 0.005 0.01 0.015
CSCCON
CSC40
CSC60
CSC80
Compressivestress(psi)
Compressive strain
0
7
14
21
28
35
Compressivestress(MPa)
0
200
400
600
800
1000
1200
1400
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
CSTCON
CST40
CST60
CST80
Tensilestress(psi)
Tensile strain
0
1.4
2.8
4.2
5.6
7.0
8.4
9.8
Tensilestress(MPa)
Fig. 2: Experimental results of plain concrete and SFRC (a) compression (b)
splitting tension
(a) (b)

Fig. 2: Experimental results of plain concrete and SFRC load
deflection behaviour of beams.
0
1
2
3
4
5
6
7
8
0 0.5 1 1.5 2
CSBFCCON
CSBFC40
CSBFC60
CSBFC80
Load(kip)
Mid point deflection (in)
0 12.7 25.4 38.1 50.8
Mid point deflection (mm)
0
4.4
8.8
13.2
17.6
22.0
26.4
31
Load(kN)
35.2

FINITE ELEMENT MODELING AND ANALYSIS
FE modeling
* Suitable element type
* Adequate mesh size
* Optimized material properties
* Appropriate boundary conditions
* Realistic loading environment
* Proper time stepping

20
FE element
SOLID65 is used to model the concrete and also SFRC. The solid is capable of
cracking in tension and crushing in compression. The element is defined by eight
nodes having three degrees of freedom at each node; translations in the nodal x, y,
and z directions. The element is capable of plastic deformation, cracking in three
orthogonal directions and crushing.
The shear element reinforcements are modeled using LINK8 element which is a 3D
spar element with three degrees of freedom at each node same to SOLID 65.The
geometry and node locations for this type of element are as follows:
K
J
L
I
M
P
O
N
I M,N,O,P
K,L
J
M
I
N
J
O,P
K,L
Prism Option
Tetrahedral Option
(not recommended)
2
6
3
Z
Y
X
Z
Y
X
1
4
5
Rebar
Z
Y
X
I
J
x

FE models
(a)
(b)
Figure 13: Typical diagram of FE model of RC beam in ANSYS 11.0 (a)
meshing and boundary condition and (b) deformed shape

FE governing parameters
Modulus of elasticity
Stress-strain relationship
Poisson’s ratio
Willum and Warke (1975) criterion
Shear transfer coefficient for open crack
Shear transfer coefficient for close crack
Tensile strength
Compressive strength

Table 1: FE input data for SOLID65 and LINK8 element
Properties for FE
model
Beam specimen (SOLID65)
Rebar
(LINK8)CSBFCCON CSBFC40 CSBFC60 CSBFC80
Density 2.69g/cm3 2.77g/cm3 2.72g/cm3 2.74g/cm3 7.8g/cm3
Tensile strength 4 Mpa 6 MPa 8 Mpa 6.3 Mpa -
Poisson’s ratio 0.325 0.325 0.325 0.325 0.3
Shear transfer Co-
efficient: Closed
crack
0.5 0.5 0.5 0.5 -
Open crack 0.3 0.3 0.3 0.3
-
Yield stress - - - - 420 Mpa

Evaluation of FE results
0
2
4
6
8
10
0 0.01 0.02 0.03 0.04 0.05
ANSYS CSBFCCON
ANSYS CSBFC40
ANSYS CSBFC60
ANSYS CSBFC80
Load(kip)
Deflection (in)
Figure 9: Load deflection behavior of FE models

Figure 10: Comparison of test results of (a) CSBFCCON (b) CSBFC40
(c) CSBFC60 (d) CSBFC80 and FE model.
(a)
0
1
2
3
4
5
6
7
8
0 0.5 1 1.5 2
ANSYS CSBFCCON
CSBFCCON
Load(kip)
0 12.7 25.4 38.1 50.8
0
4.4
8.8
13.2
17.6
22.0
26.4
31
Load(kN)
35.2
0
1
2
3
4
5
6
7
8
0 0.5 1 1.5 2
ANSYS CSBFC40
CSBFC40
Load(kip)
0 12.7 25.4 38.1 50.8
0
4.4
8.8
13.2
17.6
22.0
26.4
31
Load(kN)
35.2
(b)

Figure 10: Comparison of test results of (a)CSBFCCON (b) CSBFC40
(c)CSBFC60(d) CSBFC80 and FE model.
(c)
0
1
2
3
4
5
6
7
8
0 0.5 1 1.5 2
ANSYS CSBFC60
CSBFC60
Load(kip)
0 12.7 25.4 38.1 50.8
0
4.4
8.8
13.2
17.6
22.0
26.4
31
Load(kN)
35.2
0
1
2
3
4
5
6
7
8
0 0.5 1 1.5 2
ANSYS CSBFC80
CSBFC80
Load(kip)
0 12.7 25.4 38.1 50.8
0
4.4
8.8
13.2
17.6
22.0
26.4
31
Load(kN)
35.2
(d)

Evaluation of failure pattern and failure location for
beams
CSBFCCON
CSBFC40

CSBFC60
CSBFC80
Evaluation of failure pattern and failure location for
beams

Conclusion
29
1. The compressive strength increases about 17.6%for SFAR 40 with respect to
control specimen & ductility is increased about 5, 3.6 and 3 times for SFAR 40,
60 & 80 respectively.
2. The tensile strength enhanced about 58%, 117.5% & 64.1% & ductility
increased about 15,9.2, & 13 times respectively.
3. The load deflection behavior shows that the flexural strength increased about
50%, 94% & 79% for the SFAR 40, 60 & 80 respectively and ductility enhanced
3.7, 3.125 & 4 times respectively.
4. The FE showed similar results which ensures the validity of the models and the
FE models are successfully capable of predicting the enhanced capacities due to
SFRC.
5. These FE modeling will definitely provide invaluable information of this
engineering material to the construction industry of Bangladesh.

FINITE ELEMENT MODELING, ANALYSIS AND VALIDATION OF THE FLEXURAL CAPACITY OF RC BEAMS MADE OF STEEL FIBER REINFORCED CONCRETE (SFRC)

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