AHSANULLAH UNIVERSITY OF SCIENCE

AND TECHNOLOGY (AUST)

PAPER ID: SEE 051

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

CONCRETE (SFRC)

Presented by

Sadia Mannan MituDepartment 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

DescreteSteel 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 preventsthe 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

EXPERIMENTAL PROGRAM AND STRATEGY

120°

120°

120°

Effective length=1.85in (47.2mm)

Effective length=2.8in (70.8mm)

Effective length=3.7in (94.4mm)

Steel fiber aspect ratio 40

Steel fiber aspect ratio 60

Steel fiber aspect ratio 80

0.4

in (

10m

m)

0.4

in (

10m

m)

0.4

in (

10m

m)

Diameter=0.04in (1.18mm)

Circularcross

section

Original length=2.65in (67.2mm)

Original length=3.57in (90.8mm)

Original length=4.5in (114.4mm)

(a)(b)

Figure 3: (a) Size and geometry of steel fibers (b) image of fibers

EXPERIMENTAL PROGRAM AND STRATEGY

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

aspect ratio.

(a) (b)

EXPERIMENTAL PROGRAM AND STRATEGY

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)

EXPERIMENTAL PROGRAM AND STRATEGY

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.

EXPERIMENTAL PROGRAM AND STRATEGY

Figure 7: Horizontal data acquisition

system via DICT.

Figure 6: Experimental setup for shear

critical beam in the UTM.

EXPERIMENTAL PROGRAM AND STRATEGY

Images of Experimental Testing of Simply Supported RC Beam

EXPERIMENTAL PROGRAM AND STRATEGY

0

1000

2000

3000

4000

5000

0 0.005 0.01 0.015

CSCCONCSC40CSC60CSC80

Com

pre

ssiv

e s

tress (

psi)

Compressive strain

0

7

14

21

28

35

Com

pre

ssiv

e s

tress (

MP

a)

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

CSTCONCST40CST60CST80

Te

nsile

str

ess

(p

si)

Tensile strain

0

1.4

2.8

4.2

5.6

7.0

8.4

9.8

Te

nsile

str

ess

(M

Pa

)

Fig. 2: Experimental results of plain concrete and SFRC (a) compression (b)

splitting tension

EXPERIMENTAL PROGRAM AND STRATEGY

(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

(ki

p)

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

EXPERIMENTAL PROGRAM AND STRATEGY

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 elementSOLID65 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

PO

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

YX

Z

Y

X

1

4

5

Rebar

Z

YX

I

J

x

FINITE ELEMENT MODELING AND ANALYSIS

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

FINITE ELEMENT MODELING AND ANALYSIS

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

FINITE ELEMENT MODELING AND ANALYSIS

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

FINITE ELEMENT MODELING AND ANALYSIS

Evaluation of FE results

0

2

4

6

8

10

0 0.01 0.02 0.03 0.04 0.05

ANSYS CSBFCCONANSYS CSBFC40�ANSYS CSBFC60ANSYS CSBFC80

Load

(ki

p)

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 CSBFCCONCSBFCCON

Lo

ad

(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

Lo

ad

(kN

)

35.2

0

1

2

3

4

5

6

7

8

0 0.5 1 1.5 2

ANSYS CSBFC40�CSBFC40

Lo

ad

(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

Lo

ad

(kN

)

35.2

(b)

Evaluation of FE results

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 CSBFC60CSBFC60

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

0

1

2

3

4

5

6

7

8

0 0.5 1 1.5 2

ANSYS CSBFC80CSBFC80

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

(d)

Evaluation of FE results

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.

THANK YOU