analysis and experimental study on strength and behaviour of exterior beam-column joints with...

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International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 1, January 2017, pp. 170–188, Article ID: IJCIET_08_01_018

Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=1

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication

ANALYSIS AND EXPERIMENTAL STUDY ON

STRENGTH AND BEHAVIOUR OF EXTERIOR

BEAM-COLUMN JOINTS WITH DIAGONAL CROSS

BRACING BARS AND STEEL FIBRES FOR

IMPROVING THE JOINT DUCTILITY

K. Johnson

Research Student, Department of Civil Engineering,

Karunya University, Coimbatore, India

Dr. G. Hemalatha

Professor & Head of Civil Engineering Department,

Karunya University, Coimbatore, India

ABSTRACT

The present work aims to study analytically and experimentally on the seismic performance of

exterior beam column joint to improve the joint ductility with non-conventional reinforcement and

by using steel fibres. Five joint sub assemblages were tested under reverse cyclic loading applied at

the beam end. Beam column joints are critical regions for frames designed for inelastic response to

severe seismic attack. The overall structural safety, especially for joints is due to lack of ductility.

Different parameter of joint using ANSYS modelling was studied and experimentally verified the

results. All these details are presented.

Key words: ANSYS modelling and analysis, beam-column joints, cyclic loading, displacement

ductility, hysteretic loops.

Cite this Article: K. Johnson and Dr. G. Hemalatha. Analysis and Experimental Study on Strength

and Behaviour of Exterior Beam-Column Joints with Diagonal Cross Bracing Bars and Steel Fibres

for Improving the Joint Ductility. International Journal of Civil Engineering and Technology, 8(1),

2017, pp. 170–188.

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1. INTRODUTCION

Seismic zones of low to medium seismicity do not take into consideration for design of reinforced concrete

structures. The reinforcement details of such structures conform to the general construction code of

practice may not adhere to the modern seismic provisions. The reinforced concrete joints are treated as

rigid in the analysis of moment resisting frames. The joint is usually neglected in Indian practice for

specific design and attention being restricted to provision of sufficient anchorage for beam longitudinal

reinforcement and can be acceptable when the frame is not subjected to earthquake loads. A beam column

joint becomes structurally less efficient when subjected to large lateral loads. By increasing the number of

Analysis and Experimental Study on Strength and Behaviour of Exterior Beam-Column Joints with Diagonal

Cross Bracing Bars and Steel Fibres for Improving the Joint Ductility


stirrups at the joint the joint shear capacity can be increased. When the spacing of stirrups at the joint

becomes closer, the joint will become congested and concrete will not enter into the joint due to

insufficient spacing and this is the practical difficulty facing at site while concreting the beam column

joints. Hence required compaction at the joint will not be attained. By providing non conventional cross

diagonal bars at the joint or by providing steel fibres at the joint, shear capacity of the joint and ductility

can be increased to a great extent. Analysis and experimental results shows increase in load carrying

capacity and shear capacity of the joint with non conventional bars and fibres at the joint. The earthquake

in Turkey and Taiwan occurred in 1999 reported catastrophic failures due to failure of beam-column joints.

Akashu Sharma, R. Eligehausen and G.R.Reddy [1] study on joint shear behavior of poorly detailed beam-

column connections in RC structures under seismic loads, Part I: Exterior joints. Due to inelastic capacities

of adjoining flexural members, beams and columns, to dissipate seismic energy, the poor design of beam

column joint will lead to failure. Even though other structural members conform to the design

requirements, the beam column joint design failure leads to failure of the entire structure,. S. S. Patil, S. S.

Manekari [2] study on analysis of Reinforced Beam-Column Joint Subjected to Monotonic Loading. The

joints are to be designed and detailed properly. Joints are the weakest point and will develop cracks and

fail first in earthquakes. To Preserve the integrity of the joint sufficiently high by designing and detailing

the joint properly. The ultimate strength should be sufficient to prevent excessive degradation of joint.

Preventing the loss of bond between the concrete and longitudinal beam and column reinforcement, the

crack in the joint can be minimized. The brittle shear failure of the joint can be prevented. Choudhury, A.

M., A. Dutta, and S. K. Deb. (2011) [5]. Moments of opposite signs are developed in columns above and

below the joints during earthquake. During earthquake, at the joint region, shear force of magnitude many

times higher than in the adjacent beams and columns will be developed. Joint failure can result, if not

designed and detailed. Lu, Xilin, Tonny H. Urukap, Sen Li, and Fangshu Lin. [10] Study on Seismic

behaviour of interior RC beam-column joints with additional bars under cyclic loading.

2. ANSYS 16 WORKBENCH (WB)

2.1. Modeling Geometry and Analysis

ANSYS WB 16 is used for the finite element modeling and analysis. The design of Beam Column Joint is

done using ANSYS WB Design Modeler. The ANSYS Design Modeler application is designed to be used

as a geometry editor of existing CAD models. Designers can design models with Design Modeler alone. Its

application is a parametric feature-based solid modeller. and is designed so that designers can intuitively

and quickly begin CAD drawing for engineering analysis pre-processing. In the designing of Beam

Column Joint it is used line body method to design reinforcement bar and fibre. This method gives

advantages of less system resource and analysis time and better result accuracy.2.2Modeling Finite

Element Model:

Modeling the Finite Element model is nothing but the descretization of model into elements. The goal

of meshing in ANSYS Workbench is to provide robust, easy to use meshing tools that will simplify the

mesh generation process. These tools have the benefit of being highly automated along with having a

moderate to high degree of user control. The finite element modeling is done using Elements SOLID185,

and BEAM188.SOILD 185 is used for 3-D modeling of solid structures. It is defined by eight nodes

having three degrees of freedom at each node: translations in the nodal x, y, and z directions. The element

has plasticity, hyper elasticity, stress stiffening, creep, large deflection, and large strain capabilities. It also

has mixed formulation capability for simulating deformations of nearly incompressible elasto plastic

materials. And it is fully incompressible hyper elastic materials. BEAM 188 is suitable for analyzing

slender to moderately stubby/thick beam structures. The element is based on Timoshenko beam theory

which includes shear-deformation effects. The element provides options for unrestrained warping and

restrained warping of cross-sections. The element is a linear, quadratic, or cubic two-node beam element in

3-D. BEAM 188 has six or seven degrees of freedom at each node. A seventh degree of freedom (warping

K. Johnson and Dr. G. Hemalatha


magnitude) is optional. This element is well-suited for linear, large rotation, and/or large strain nonlinear

applications.

2.2. Material Properties in ANSYS WORKBENCH and ANSYS Analysis

2.2.1. Loading Systems

The major loads are dead load, live load, imposed (wind) load, snow load, earthquake load imposed in the

structures. The analysis of joints is done with static and dynamic loads. Beams (bending), column (axial),

are static loading nature. Shake similar to that during earthquakes is called dynamic (random) loading.

2.2.2. Engineering Data

Use the Engineering Data cell with the Mechanical application systems or the Engineering Data

component system to define or access material models for use in an analysis. To add an Engineering Data

component system to the Project Schematic, drag the Engineering Data component system from the

Toolbox to the Project Schematic or double-click the system in the Toolbox. Study on Steel fibre

reinforced high performance concrete beam-column joints subjected to cyclic loading [7,8,9,10].

The non linear analysis of Beam Column Joint is done in Static and Transient (dynamic) analysis

system. The acceleration data given for analysis is taken from earthquake data of zone -III. A static load of

17 kN is applied at the tip of the beam and load increased gradually with 6 load steps. Static and dynamic

loading is applied at the joint and studied the behavior. Results taken from zone-III are used for preparation

of FE model.

3. PROPOSED WORK

3.1. ANSYS Modeling of Exterior Beam Column Joints under Static Loading

ANSYS modeling and analysis under static and dynamic loading with different loading conditions using

steel fibers, diagonal steel bars in the joint and at extended in column and beam directions to study the

resistant of shear or bond failure.

Steel fiber = 1% by volume and extending in column and beam directions. Study on Use of fibre

cocktails to increase the seismic performance of beam-column Joints [14,16,17,18].

3.2. Beam Column Joint Design details for ANSYS Modeling

Column size- 175 mm x 150 mm, Beam size- 175 mm (D) x 150 mm(B), Strength of concrete fck- 20

N/mm2., Yield strength of steel fy- 415 N/mm2.Column longitudinal steel- 16 mm diameter- 4 nos.

Column lateral tie- 8 mm diameter @ 150 mm c/c.. Beam main reinforcement steel- 12 mm diameter- 4

nos. Beam stirrups- 8 mm @ 100 mm c/c. Maximum load on column – Pmax. - 336 kN. Beam point load-

W max- 17 kN. Column height- 1500 mm, Beam length- 600 mm. RCC beam column joints were designed

for analysis based on IS 1893-2002 Criteria for Earthquake Resistant design of structures and detailing

based on IS 13920-1993 Edition 1.2 (2002-03) on Indian Standard Code of Practice Ductile Detailing of

Reinforced and referring to relevant books[24,25,26,27].

Analysis and Experimental Study on Strength and Behaviou


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3.3. External Beam-Column J

Figure 1 External joint under static loading

Figure 3 Pu&Wmax- bending stress

Figure 5 ANSYS 16 modeling under dynamic loading.

Figure 7 External joint static analysis using diagonal bars at t



IJCIET/index.asp 173

Column Joint - Analysis Setup

External joint under static loading Figure 2 ANSYS 16 modeling stat

bending stress Figure 4 Pu&Wmax

ANSYS 16 modeling under dynamic loading.-Deflection Figure 6

External joint static analysis using diagonal bars at the joint. Figure 8

Column Joints with Diagonal


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ANSYS 16 modeling static loading.-Deflection

Pu&Wmax- shear stress

Figure 6 Pu & Wmax- shear stress

Pu & Wmax- deflection

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Figure 9 Pu & Wmax

Figure 11 External joint using

Figure 13 Steel fibers extending


IJCIET/index.asp 174

Wmax- bending Figure 10 Pu & Wmax

External joint using steel fibers Figure 12 Pu &

Steel fibers extending in beam Figure 14 Pu &

Figure 15 Pu & Wmax- bending

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Wmax - shear

Wmax- deflection

Wmax- deflection




4. DUCTILITY

Ductility is generally measured in terms of displacement ductility. This is the ratio of the maximum

deformation that a structure or an element can undergo without significant loss of initial yielding resistance

to the initial yield deformation. The displacement ductility of all the models is presented in table 1. It can

be seen that the displacement ductility is more for the beam column joint with additional cross diagonal

bars and additional steel fibres. The percentage increase is 76.03% and 63.01%.The ductility increment is

more for the beam column joint with additional diagonal cross bars than with additional fibres by 13.02%. It can be seen that the displacement ductility factor for beam column joint with additional cross bracing

bars is 55.32% more than that of normal beam column joints. It can be seen in ANSYS 16 analysis that the

deflection at yield point load and at ultimate load are increasing by using the non-conventional diagonal

bars and steel fibre at the beam column joint. The displacement at ultimate load increases when the

additional cross diagonal bars and additional steel fibres are added at the beam column joint. Also it can be

seen that the results are better for the beam column joints with non-conventional diagonal bars extending

on beam and column directions by .3H and .3B. The ultimate upward displacement is greater than the

downward displacement for all the specimens.

Table 1 Displacement ductility of specimen from ANSYS model.

A1- Normal (IS 456) Static loading, A-Normal (IS 456) transient loading, B-With additional diagonal

bars at the joint - transient loading, C-With additional diagonal bars at the joint and extending in beam

(.3B) & column(.3H)- transient loading. D-With additional fibre at the joint- transient loading, E-With

additional fibre at the joint and extending in beam (.3B) & column (.3H) - transient loading.

Displacement (mm)

specimen yield ultimate Displacement ductility Average

displacement

ductility

Downward

direction

Upward

direction

Downward

direction

Upward

direction

Downward

direction

Upward

direction

A1 3.45 - 12.45 - 3.61 - 3.61

A 4.21 4.85 14.28 16.28 3.39 3.36 3.38

B 3.32 3.63 17.28 19.27 5.20 5.30 5.25

C 4.53 4.35 19.38 33.25 5.27 6.64 5.95

D 3.98 3.78 17.29 22.45 4.34 5.94 5.14

E 3.95 3.93 18.67 24.78 4.72 6.31 5.51



Table 2 Yield load and ultimate load of specimen from ANSYS 16 model

Table 2 shows the yield load and ultimate load in ANSYS analysis. The yield load for the specimen A1

is 18.15 k N and ultimate load is 20.34 k N under static loading. The yield load for the specimen A is 18.15

k N and ultimate load is 21.23 k N under dynamic loading. The yield load for the specimen B is 19.92 k N

and the ultimate load is 22.34 k N which is 9.75% and 5.22% more respectively than specimen A. The

yield load for the specimen C is 20.50 k N and the ultimate load is 24.03 k N which is 12.94% and 13.19%

more respectively than specimen A. The yield load for the specimen D is 18.38 k N and the ultimate load is

21.45 k N which is 1.26% and 15.16% more respectively than specimen A. The yield load for the specimen

E is 19.45 k N and the ultimate load is 22.03 k N which is 7.16% and 3.78% more respectively. It can be

seen in ANSYS analysis that the yield load carrying capacity and ultimate load carrying capacities of the

specimens are increasing by using the non-conventional cross diagonal bars and steel fibre at the beam

column joint. Also it can be seen that the results are better for the beam column joints with non-

conventional diagonal bars extending in beam and column directions by .3H and .3B. The higher stiffness

in finite element models may be due to the no consideration of the micro cracks in concrete and bond slip

of the reinforcement. Thus considering the ultimate load carrying capacities from analytical studies it can

be observed that the maximum load carrying capacity is for the beam column joint with cross diagonal bars

at the joint and extending in beam and column direction .3B and .3H respectively. The average

displacement ductility of specimens A1,A,B,C,D&Eare 3.61,3.38,5.25,5.95,5.140 and 5.51 respectively. It

can be seen that the displacement ductility is more for the beam column joint with additional cross

diagonal bars and additional steel fibres. The percentage increase is 76.03% and 63.01%.The ductility is

more for the beam column joint with additional cross diagonal bars than steel fibre by 13.02%.

The below given graph, figure16 and 17 is for the load against downward /upward displacement of

specimens under static and transient loading. It can be seen that the displacement under yield load and for

ultimate load for the beam column joint under static loading, dynamic loading, with additional cross

diagonal bracing bars, with additional steel fibre is 3.45 mm, 12.45 mm,4.21mm,14.28mm, 4.11mm, 17.28

mm, 4.53mm , 19.28 mm,3.98 mm, 17.29mm and 3.95 mm, 18.67mm respectively. The displacement at

ultimate load increases when the additional cross diagonal bars and additional steel fibres are added at the

beam column joint. Also it can be seen that when the cross diagonal bars and fibres are added beyond the

beam column joint in column and beam direction upto .30 H and .3 B, the ultimate displacement obtained

is more than that obtained when the cross bars and fibres are at the joint alone. The effect of displacement

at yield load and at ultimate load with the additional cross diagonal bars is more than additional steel fibre

at the joint.

Yield load (kN) Ultimate load (kN)

Specimen Downward

direction

Upward

direction

Average(P

ye)

Downward

direction

Upward

direction

Average(Pue

)

A1 18.15 - 18.15 20.34 - 20.34

A 18.15 18.15 18.15 21.23 21.23 21.23

B 19.98 19.85 19.92 22.34 22.34 22.34

C 20.15 20.84 20.50 23.83 24.23 24.03

D 18.38 18.38 18.38 20.45 20.45 20.45

E 19.45 19.45 19.45 21.38 20.98 21.18




Figure 16 Downward load-displacement curves Figure 17 Upward load-displacement curves

Comparison of ultimate load in upward loading and downward loading for all specimens is shown in

figure 18 and 19. The ultimate load carrying capacities of specimens A1,A,B,C,D&E are 20.34 k N, 21.23

k N, 22.34 k N, 24.03 k N, 21.45 k N and 22.03 k N respectively. The ultimate load carrying capacity of

beam-column joint with cross diagonal bracing bars increases by 5.22% when comparing with normal

beam –column joint and when the cross bracing bars are extended in beam and column directions by .3 B

and .3 H , the increase in ultimate load carrying capacity is 13.18% when comparing with normal beam

column joint. When steel fibre is added in the beam column joint in addition to normal bars, the ultimate

load carrying capacity is increased by 1.03% and when the steel fibres are extended in beam and column

directions by .3 B and .3 H, the increase in ultimate load carrying capacity is 3.76% when comparing with

normal beam column joint. Also it can be seen that cross bracing bars is added at the beam column joint in

addition to normal bars, the ultimate load carrying capacity increases by 9.41% than that of beam column

joint with steel fibres.

Figure 18 Upward loading Figure 19 Downward loading

Comparison of average displacement ductility for all the specimens A1,A,B,C,D,E are given below in

the figure 20,21 and 22. The displacement ductility factor for specimens A,B,C,D,E are 3.38,4.41,5.95,5.14

0

5

10

15

20

25

0 5 10 15 20

Displacement in mm

Load

in k

N

Load-downward dispalcement graph

-A1-A-B-C-D-E

0

5

10

15

20

25

0 5 10 15 20 25 30

Displacement in mm

Load

in k

N

Load-upward dispalcement graph

-A-B-C-D-E

21.23

22.34

24.23

20.45

20.98

18

19

20

21

22

23

24

25

A B C D E

Series1

Ulti

mat

e lo

ad in

kN

Upward loading

Specimen designation

20.34

21.23

22.34

23.23

20.45

21.38

18.5

19

19.5

20

20.5

21

21.5

22

22.5

23

23.5

A1 A B C D E

Series1

Downward loading

Ulti

mat

e lo

ad in

kN




and 5.51 respectively. It can be seen that the displacement ductility is more for the beam column joint with

additional cross diagonal bars and additional steel fibres. The percentage increase is 76.03% and

63.01%.The ductility is more for the beam column joint with additional cross diagonal bars than steel fibre

by 13.02%.

Figure 20 Ductility Downward direction Figure 21 Ductility Upward direction

Figure 22 Average displacement ductility

5. ENERGY DISSIPATION

With the models so far developed, the energy absorption capacity of different joints can be studied since

ductility is directly linked with energy absorption capacity of joints. The figure 23 and 24 below shows the

moment slope curves and cumulative energy absorption for the specimens A1,A,B,C,D and E respectively.

The area enclosed by the graph represents the energy dissipated by the specimens. It can be seen that the

energy dissipation is maximum for the beam column joint specimen with additional cross diagonal bars at

the joint and extending in beam and column directions by .3 B and .3 H in addition to normal

reinforcement. The beam column joint with additional diagonal confining bars, the energy dissipated is

found more than that of the beam column joint with normal bars. Also it can be found that the beam

column joint with normal reinforcement A1 and A starts yielding much before than the additional bars and

fibres. The specimens B and C the moment at yielding point is more than the moment at yielding point of

the beam column joint with additional fibres for the specimens D and E. The energy dissipated by the

specimens A1,A, B,C,D and E are 280 kN-mm, 420 kN-mm, 455 kN-mm, 560 kN-mm, 475kN-mm and

512.50 kN-mm respectively. The increase in energy dissipated by the beam-column joint with diagonal

bars is 8.33% when comparing with the normal beam-column joint. The increase in energy dissipated by

3.613.39

5.2 5.27

4.34

4.72

0

1

2

3

4

5

6

A1 A B C D E

Series1


Dis

pla

ce

me

nt

du

cti

lity

Downward direction

3.36

5.2

7.64

5.946.31

0

1

2

3

4

5

6

7

8

9

A B C D E

-

-

Dis

pla

ce

me

nt

du

cti

lity


Upward direction

Dis

pla

ce

me

nt

du

cti

lity


Upward direction

3.613.38

5.25

5.95

5.145.51

0

1

2

3

4

5

6

7

A1 A B C D E

Series1

Specimens

Dis

pla

cem

ne

t d

ucti

lity

Specimens




the beam column joint with steel fibre is 13.09% when comparing with the normal beam-column joint.

When comparing the energy dissipation capacity of beam –column joint with steel fibre and additionally

diagonally braced bars is 16.67% less. It can be seen that by extending the additional diagonal bars in the

beam-column joint in beam and column direction by .3B and .3H, the energy dissipation is increased by

7.69%. It can be seen that by extending the steel fibre in the beam-column joint in beam and column

direction by .3B and .3H, the energy dissipation is increased by 23.07%. The energy dissipation is

increasing with additional diagonal bars when comparing with steel fibre.

Figure 23 Moment - Slope curves Figure 24 Cumulative energy dissipation

Table 3 Maximum bending/ shear stress

The above table -3 indicates the results of ANSYS 16 analysis for specimens the maximum principle

stress, maximum shear stress, under static loading, seismic loading, using normal reinforcement steel, steel

fibers, using diagonal cross bracing bars at the joint, for exterior beam-column joints. The maximum shear

stress obtained in static loading is 7.51 MPa whereas the maximum shear stress under dynamic loading is

10.72 MPa with a percentage increase of 42.74%. The maximum bending stress obtained in static loading

is 17.34 MPa whereas the maximum bending stress under dynamic loading is 18.27 MP with a percentage

increase of 5.36%.

Analytical study of exterior beam column joint with additional diagonal bars within the joint subjected

to static and seismic loading by nonlinear finite element analysis using ANSYS software for nonlinear

analysis of reinforced concrete structures were carried out by increasing the diagonal reinforcement in

beam directions and column directions .3B and .3H respectively. The maximum shear stress obtained

0

5

10

15

20

25

0 0.02 0.04 0.06 0.08 0.1

A1

A2

B1

B2

C1

C2

Mom

ent i

n kN

-mM

omen

t in

kN-m

slope

280

420455

560

475

512.5

0

100

200

300

400

500

600

A1 A B C D E

Series1

Specimen

Cu

mu

lativ

e e

ne

rgy

dis

sip

ate

d in

kN

-mm

Loading conditions Maximum shear

stress(MPa)

Maximum bending

stress(MPa)

Static 7.51 17.34

Dynamic 10.72 18.27

Diagonal bars 7.05 14.48

.3B 6.00 12.30

1% fiber 10.10 16.15

.3B 8.95 14.38



under the same loading conditions in dynamic loading is 7.05 MPa. The maximum bending stress under

dynamic loading is 14.48 MPa. The maximum shear stress and maximum bending stress of beam column

joint with additional cross diagonal bars extending in beam and column directions by .3B and .3H are 6.00

MPa and 12.30 MPa. It can be seen that the bending stress and shear stress are decreasing by 15.05% and

14.89% respectively. From the analysis it can be seen that the effect of diagonal bars in exterior beam

column joint in reducing shear stress and bending stress at the joint under static and dynamic loading

conditions is effective when comparing with joint without cross diagonal bars. The additional bars

effectively increased the strength capacity at the joint vicinity as well as sufficient development of ductility

to the frame members under increasing lateral loading. The joint was fully restrained at the column ends. It

was inferred from the analysis that as load increases displacement, minimum stress and maximum stress

also increases. Also the stiffness of the structure changes the displacement, minimum stress and maximum

stress changes with respect to loading. With the increase of ratio of bending moment of column to beam,

the plastic hinges are more likely to develop in the beam, and the ductility of the joint improves. Additional

diagonal bars prevented cracks at the edges of the joint interface between column and beam. Furthermore,

these joints have been proven to behave in a ductile manner as beams undergo plastic hinging earlier than

the columns. The orientation of additional cross diagonal bars added strength in favour of members they

were oriented to. That is, additional bars along beam added strength towards the beam ends and additional

bars along column added strength towards the column.

The performance of steel fibre reinforced exterior beam-column joints were compared with that of

conventional joints. Results showed that using steel fibre reinforced concrete (SFRC) within beam-column

can significantly enhance the shear resistance capacity of joints.It can be seen that the effect of steel fiber

in exterior beam column joint in reducing shear stress and bending stress at the joint under static and

dynamic loading conditions is effective when comparing with joint with normal reinforcement steel and

with diagonal bars. The maximum shear stress obtained under dynamic loading condition is 10.10 MPa

whereas the maximum bending stress is 16.15MPa. The maximum bending stress obtained under the same

loading conditions in dynamic loading with steel fiber extending in beam and column directions by .3B

and .3 H is 14.38MPa whereas the maximum shear stress is 8.95 MPa. The analysis results also showed

that using additional steel fibre reinforcement is an effective method to reduce the lateral reinforcement in

the beam plastic hinge region. The decrease in bending stress by extending the fibre in beam and column

directions is 10.95% and 10.99%.

It is generally accepted that addition of steel fibres significantly increases tensile toughness and

ductility, also slightly enhances the compressive strength. The benefits of using steel fibres become

apparent after concrete cracking because the tensile stress is then redistributed to fibres. The results

showed that using steel fibres can significantly increase the joint shear strength and also the shear stress

corresponding to the first crack.

6. EXPERIMENTAL WORK

• Five samples casted and tested in laboratory as given below A-Normal (as per IS 456- 2000)

• B-With additional diagonal bars at the joint

• C-With additional diagonal bars at the joint and extending in beam ( .3B) & column(.3H)

• D-With additional fibre at the joint

• E-With additional fibre at the joint and extending in beam (.3B) & column (.3H)

• Specimen size(T Shape) - Column size- 1000 mm x 175 mm x 150 mm. Beam size- 600 mm x 175 mm x

150 mm.

• The material properties of steel fibre used are DRAMIX ® 3D

with tensile strength 1225 N/mm2, Young’s

modulus 210000 N/mm2, length 60 mm, aspect ratio 80 and diameter is 0.75 mm.




Figure 25 Casted specimen ready for testing Figure 26 Test set up

Figure 27 Testing progress Figure 28 Crack patterns.

Table 4 Displacement ductility of specimen tested in laboratory

Displacement (mm)

specimen yield ultimate Displacement ductility Average

displacement

ductility

Downward

direction

Upward

direction

Downward

direction

Upward

direction

Downward

direction

Upward

direction

A 4.70 4.60 16.50 16.00 3.50 3.50 3.50

B 4.17 3.70 21.50 19.50 5.15 5.25 5.20

C 3.40 4.40 15.00 33.00 4.40 7.50 5.95

D 3.70 3.75 17.29 22.45 4.30 5.90 5.10

E 4.10 4.13 18.67 24.78 4.50 6.00 5.25



The displacement ductility of all the specimens tested in laboratory is presented in table 4. It can be

seen that the displacement ductility is more for the beam column joint with additional cross diagonal bars

and additional steel fibres. The percentage increase is 70% and 50%.The ductility increment is more for the

beam column joint with additional diagonal cross bars than with additional fibres by 20%. It can be seen

that the displacement ductility factor for beam column joint with additional cross bracing bars is 48.57%

more than that of normal beam column joints. Also it can be seen that the results are better for the beam

column joints with non-conventional diagonal bars extending on beam and column directions by .3H and

.3B. The ultimate upward displacement is greater than the downward displacement for all the specimens.

Table 5 Yield load and ultimate load of specimen tested in laboratory

Figure 29 Ultimate load of specimens Figure 30 Average displacement ductility of specimens

Testing results shows the yield load for the specimen A is 15.45 k N and ultimate load is 18.50 k N

under dynamic loading. The yield load for the specimen B is 18.45 k N and the ultimate load is 22.00 k N

which is 19.41% and 18.91% more respectively than specimen A. The yield load for the specimen C is

23.12 k N and the ultimate load is 26.00 k N which is 49.64% and 40.54% more respectively than

specimen A. The yield load for the specimen D is 18.48 k N and the ultimate load is 21.00 k N which is

19.43% and 13.51% more respectively than specimen A. The yield load for the specimen E is 19.12 k N

and the ultimate load is 23.00 k N which is 23.75% and 24.32% more respectively. It can be seen in

experimental results that the yield load carrying capacity and ultimate load carrying capacities of the

specimens are increasing by using the non-conventional cross diagonal bars and steel fibre at the beam

column joint. Also it can be seen that the results are better for the beam column joints with non-

conventional diagonal bars extending in beam and column directions by .3H and .3B. Thus considering the

ultimate load carrying capacities from experimental studies it can be observed that the maximum load

Yield load (kN) Ultimate load (kN)

Specimen Downward

direction

Upward

direction

Average(P

ye)

Downward

direction

Upward

direction

Average(Pue

)

A 15.35 15.50 15.45 18.25 18.75 18.50

B 17.80 18.10 18.45 21.50 22.50 22.00

C 22.50 23.75 23.12 25.25 26.75 26.00

D 18.38 18.75 18.48 20.50 21.50 21.00

E 19.00 19.25 19.12 22.00 24.00 23.00

18.5

22

26

21

23

0

5

10

15

20

25

30

A B C D E

Series1

Ultim

atel

oad

in kN

Specimens

Experiment results

3.5

5.2

5.95

5.1 5.25

0

1

2

3

4

5

6

7

A B C D E

Series1

Av

era

ge

dis

pla

ce

me

nt

du

cti

lity Experiment- displacement ductility




carrying capacity is for the beam column joint with cross diagonal bars at the joint and extending in beam

and column direction .3B and .3H respectively.

6.1. Energy Dissipation in Experimental Works Load –Displacement Hysteresis Loops

From the experimental works, the energy absorption capacity of different joints can be studied since

ductility is directly linked with energy absorption capacity of joints. The figure 23 and 24 below shows the

load –displacement hysteresis loops and cumulative energy absorption for the specimens A,B,C,D and E

respectively. The area enclosed by the graph represents the energy dissipated by the specimens. It can be

seen that the energy dissipation is maximum for the beam column joint specimen with additional cross

diagonal bars at the joint and extending in beam and column directions by .3 B and .3 H in addition to

normal reinforcement. The beam column joint with additional diagonal confining bars, the energy

dissipated is found more than that of the beam column joint with normal bars. Also it can be found that the

beam column joint with normal reinforcement A starts yielding much before than the additional bars and

fibres. The specimens B and C the moment at yielding point is more than the moment at yielding point of

the beam column joint with additional fibres for the specimens D and E. The energy dissipated by the

specimens A, B,C,D and E are 450 kN-mm, 475 kN-mm, 600 kN-mm, 525kN-mm and 550 kN-mm

respectively. The increase in energy dissipated by the beam-column joint with diagonal bars is 8.33%

when comparing with the normal beam-column joint. The increase in energy dissipated by the beam

column joint with steel fibre is 13.09% when comparing with the normal beam-column joint. When

comparing the energy dissipation capacity of beam –column joint with steel fibre and additionally

diagonally braced bars is 16.67% less. It can be seen that by extending the additional diagonal bars in the

beam-column joint in beam and column direction by .3B and .3H, the energy dissipation is increased by

7.69%. It can be seen that by extending the steel fibre in the beam-column joint in beam and column

direction by .3B and .3H, the energy dissipation is increased by 23.07%. The energy dissipation is

increasing with additional diagonal bars when comparing with steel fibre.

Figure 31 Specimen as per-IS-456-2000 Figure 32 Specimen with cross diagonal bars at joint

-25

-20

-15

-10

-5

0

5

10

15

20

25

-20 -15 -10 -5 0 5 10 15 20 25

SPECIMEN-A

SAMPLE-A

-25

-20

-15

-10

-5

0

5

10

15

20

25

-25 -20 -15 -10 -5 0 5 10 15 20 25

SAMPLE-B

Series2

SPECIMEN-B



Figure 33 Specimen with cross diagonal bars extended Figure 34 Specimen with steel fibres at joint

Figure 35 Specimen with steel fibres extended Figure 36 Experiment- Cumulative energy dissipation

Table 6 Comparison of energy dissipation Analysis vs Experimental

The beam column joint with additional diagonal confining bars, the energy dissipated is found more

than that of the beam column joint with normal bars with increase of 25%. The beam-column joint with

additional steel fibres, the energy dissipation is found less than that of joint with cross diagonal bars by

9.10%. The increase in energy dissipated by the beam-column joint with diagonal bars extended in beam-

column direction is more that when comparing with the normal beam-column joint with cross diagonal

bars at the joint by 26.31%. The increase in energy dissipated by the beam column joint with steel fibre is

22.22% when comparing with the normal beam-column joint.

-30

-20

-10

0

10

20

30

-30 -20 -10 0 10 20 30 40

SPECIMEN-C

SAMPLE-C

LO

AD

IN

kN

-25

-20

-15

-10

-5

0

5

10

15

20

25

-25 -20 -15 -10 -5 0 5 10 15 20 25

SPECIMEN-D

SAMPLE-D

-30

-20

-10

0

10

20

30

-25 -20 -15 -10 -5 0 5 10 15 20 25 30

SPECIMEN-E

SAMPLE-E

450475

600

525550

0

100

200

300

400

500

600

700

A B C D E

Series1

cum

ula

tiv

e e

ne

rgy

dis

sip

ate

dk

N-m

m

Expeirment- cumulative enery dissipation

specimen

Specimen Energy dissipation kN-mm)-

Analysis

Energy dissipation(kN-

mm)-Experimental

% increase energy dissipation

A 420 450 -

B 455 475 5.55

C 560 600 33.33

D 475 525 16.67

E 521.5 550 22.22




Table 7 Comparison of ultimate load- Analysis vs experimental

The ultimate load in analysis for the specimen A is 21.23 k N and the ultimate load in testing is 18.50 k

N which is 12.85% variation. The ultimate load in analysis for the specimen B is 22.34 k N and the

ultimate load in testing is 22 k N which is 1.52% variation. The ultimate load in analysis for the specimen

C is 24.03 k N and the ultimate load in testing is 26 k N which is 8.19% variation. The ultimate load in

analysis for the specimen D is 20.45 k N and the ultimate load in testing is 21 k N which is 2.68%

variation. The ultimate load in analysis for the specimen E is 21.18 k N and the ultimate load in testing is

23 k N which is 8.59% variation. It can be seen in ANSYS analysis that the yield load carrying capacity

and ultimate load carrying capacities of the specimens are increasing by using the non-conventional cross

diagonal bars and steel fibre at the beam column joint.

Table 8 Comparison of ultimate load and increase in load carrying capacity

The ultimate load carrying capacity of beam-column joint with cross diagonal bracing bars increases by

18.91% when comparing with normal beam –column joint and when the cross bracing bars are extended in

beam and column directions by .3 B and .3 H , the increase in ultimate load carrying capacity is 40.34%

when comparing with normal beam column joint. The ultimate load carrying capacity of beam-column

joint with fibres increases by 13.51% when comparing with normal beam –column joint and when the

fibres are extended in beam and column directions by .3 B and .3 H, the increase in ultimate load carrying

capacity is 24.32% when comparing with normal beam column joint.

Specimen Ultimate load (kN)-

Analysis

Ultimate load (kN)-

Experimental

% variation

A 21.23 18.50 12.85

B 22.34 22.00 1.52

C 24.03 26.00 8.19

D 20.45 21.00 2.68

E 21.18 23.00 8.59

Specimen Ultimate load (kN)-

Analysis

Ultimate load (kN)-

Experimental

% increase in load

A 21.23 18.50 -

B 22.34 22.00 18.91

C 24.03 26.00 40.54

D 20.45 21.00 13.51

E 21.18 23.00 24.32



Table 9 Comparison of ductility factor and increase in ductility

It can be seen that the displacement ductility factor for beam column joint with additional cross bracing

bars is 48.57% more than that of normal beam column joints. The cross bracing bars extending in beam

and column direction by .3B and .3H, the ductility factor increases by 70%than that of beam column joints

with bars at the joint. Beam column joints with addition of steel fibre, the ductility factor increases by

45.71% and when the fibres are extended in beam and column directions by .3B and .3H, the ductility

factor increases by 50%. It can be seen that the ductility factor is more for the beam column joints with

cross bracing bars by 20% than steel fibres. The cross bracing bars extending in beam and column

direction by .3B and .3H, the ductility factor increases by 21.43%than that of beam column joints with bars

at the joint.

7. CONCLUSIONS

In this paper performance of exterior beam column joints with non-conventional reinforcement detailing

and steel fibres were examined analytically using ANSYS 16 modeling and analysis and experimentally

tested specimens under static loading, seismic loading, using normal reinforcement steel, steel fibers, using

cross diagonal bars at the joint, diagonal bars and fibers at varying depths and heights in beam and column

directions are carrying out to find out various factors affecting the failure of joints under different loading

conditions. The exterior beam-column joints are studied with different parameters like i.e. Maximum

principle stress, Maximum shear stress, Displacement, rotations, yield load, ultimate load, displacement

ductility and energy absorption capacity. Specimens were casted and tested at laboratory to compare the

results obtained the in analysis and experiment. It is found that the results of ANSYS analysis and

experiments are matching very well with marginal variations as tabulated. Specimens were casted and

tested at laboratory to compare the results obtained the in analysis and experiment. It is found that the

results of ANSYS analysis and experiments are matching very well with marginal variations as tabulated.

Additional cross diagonal bars, steel fibres at the joint along with lateral reinforcement prevented cracks at

the edges of the joint interface between column and beam. The additional cross diagonal bars and steel

fibres extension in the beam and column directions analysis results shows increase the ductility of the joint

, yield load and ultimate load carrying capacity and increased energy absorption capacity under higher

loading conditions. The orientation of additional diagonal bars added strength in favour of members they

were oriented to. Additional bars along beam added strength towards the beam ends and additional bars

along column added strength towards the column. The performance of steel fibre reinforced exterior beam-

column joints were compared with that of conventional joints. Results showed that using steel fibre

reinforced concrete (SFRC) within beam-column joints can significantly enhance the shear resistance

capacity, displacement ductility and energy absorption capacity of joints. The analysis results also showed

that using steel fibre reinforcement is an effective method to reduce the lateral reinforcement in the beam

Specimen Average displacement

ductility

Increase in displacement

ductility with normal

specimen

% increase

A 3.50 - -

B 5.20 1.70 48.57

C 5.95 2.45 70.00

D 5.10 1.60 45.71

E 5.25 1.75 50.00




plastic hinge region and can significantly increase the joint shear strength and also the shear stress

corresponding to the first crack.

8. ACKNOWLEDGEMENT

ANSYS 16 modeling and analysis of RCC exterior beam column joints under different loading conditions

and specimens were casted and tested at laboratory to compare the results obtained the in analysis with the

whole hearted help, support and directions of many people through their constructive criticisms in the

evaluation and preparation of this paper. The author takes this opportunity to appreciate the works done by

many researchers in this field. Thanks to all for extending the necessary support and guidance required to

complete this paper.

REFERENCES

[1] American Concrete Institute, ACI 352R-02, ACIASCE, Committee 352, Detroit, 2002,

Recommendations for design of beam-column-joints in monolithic reinforced concrete structures.

[2] Choudhury, A. M., A. Dutta, and S. K. Deb. (2011) "Study on size effect of RC deficient beam-column

joints with and without retrofitting under cyclic loading." International Journal of Civil and Structural

Engineering Volume 2, No 2, 2011, ISSN 0976 – 4399

[3] Ganesan, N., P. V. Indira, and Ruby Abraham. "Steel fibre reinforced high performance concrete beam-

column joints subjected to cyclic loading." ISET J. Earthq. Technol 44.3-4 (2007): 445-456.

[4] ISET (1981). "A Manual of Earthquake Resistant Non- Engineered Construction”.Indian society of

earthquake technology.Roorkee.

[5] Liu, C. (2006). ―Seismic Behaviour of Beam-Column Joint Sub assemblages Reinforced with steel

Fibers‖, Master’s Thesis, University of Canterbury,Christchurch, New Zealand.

[6] Lu, Xilin, Tonny H. Urukap, Sen Li, and Fangshu Lin. "Seismic behaviour of interior RC beam-column

joints with additional bars under cyclic loading."Earthquake and Structures 3, no. 1 (2012): 37-57.

[7] Pannirselvam, N., P. N. Ragunath, and K. Suguna. "Strength Modeling of Reinforced concrete Beam

with Externally Bonded FRP Reinforcement."American Journal of Engineering and Applied Sciences

1.3 (2008): 192.

[8] Patil, S. S., and S. S. Manekari. "Analysis of Reinforced Beam-Column Joint Subjected to Monotonic

Loading." International Journal of Engineering and Innovative Technology (IJEIT), Analysis 2.10

(2013).

[9] Perumal, P., and B. Thanukumari. "Use of fibre cocktails to increase the seismic performence of beam-

column Joints." International Journal of Engineering Science and Technology 2.9 (2010): 3997-4006.

[10] French, C., M.E. Kreger, and American Concrete Institute., High-strength concrete (HSC) in seismic

regions. 1998, Farmington Hills, MI: American Concrete Institute. vii, 471.

[11] Midrand, Fibre reinforced concrete. Cement & Concrete Institute, 1997. 178

[12] Anon, Design considerations for steel fiber reinforced concrete. ACI Structural Journal (American

Concrete Institute), 1988. 85(5): p. 563-580.

[13] Soroushian, P., F. Mirza, and A. Alhozaimy, Bonding of confined steel fiber reinforced concrete to

deformed bars. ACI Materials Journal (American Concrete Institute), 1994. 91(2): p. 141-149.

[14] Tang, J., et al., Seismic behavior and shear strength of framed joint using steel-fiber reinforced

concrete. Journal of Structural Engineering, 1992. 118(2): p. 341-358.

[15] Barragan, B., et al. Development and application of fibre-reinforced self-compacting concrete. 2005.

Dundee, Scotland, United Kingdom: Thomas Telford Services Ltd, London, E14 4JD, United Kingdom.



[16] Miao, B., J.-C. Chern, and C.-A. Yang, Influences of fiber content on properties of self-compacting steel

fiber reinforced concrete. Journal of the Chinese Institute of Engineers, Transactions of the Chinese

Institute of Engineers,Series A/Chung-kuo Kung Ch'engHsuchK'an, 2003. 26(4): p. 523-530.

[17] Canbolat, B.A., G.J. Parra-Montesinos, and J.K. Wight, Experimental study on seismic behavior of high-

performance fiber-reinforced cement composite coupling beams. ACI Structural Journal, 2005. 102(1):

p. 159-66.

[18] Swamy, R.N. and H.M. Bahia, Effectiveness of steel fibers as shear reinforcement. Concrete

International: Design and Construction, 1985. 7(3): p. 35-40.

[19] K.R.Bindu and K.P.Jaya, Strength and behaviour of exterior beam column joint with diagonal cross

bracing bars. Asian Journal of Civil Engineering (Building and Housing ) Vol.II,No.3(2010):p 397-410.

[20] Gencoglu, M., and B. Mobasher. "The strengthening of the deficient RC exterior beam-column joints

using CFRP for seismic excitation." Proceedings of the 3rd

international conference on structural

engineering, mechanics and computation 10-12 September 2007,Cape town ,South Africa”.

[21] Gupta,A. and Agarwal,P. "Performance Evaluation Of Exterior RC Beam Column Joint strengthened

With FRP Under Cyclic Load” Fourth International Conference on Structural Stability and Dynamics

(ICSSD 2012), 4–6 January, 2012.

[22] Takayama, H., Proceedings of the JCI International Workshop on Ductile Fiber Reinforced

Cementitious Composites (DFRCC)-Application and Evaluation. 2002, Tokyo: Japan Concrete Institute.

[23] IS 13920-1993 Edition 1.2 (2002-03), “Indian Standard Code of Practice Ductile Detailing of

Reinforced Concrete Structures Subjected to Seismic Forces”, Bureau of Indian Standards, New Delhi,

2002.

[24] IS 1893-2002 Criteria for Earthquake Resistant design of structures

[25] IS 456: 2000 (Fourth Revision), “Indian Standard: Plain and Reinforced Concrete –Code of Practice‖,

Bureau of Indian Standards, New Delhi, 2005.

[26] M. Said and T. M. Elrakib. Enhancement of Shear Strength and Ductility for Reinforced Concrete Wide

Beams Due To Web Reinforcement. International Journal of Civil Engineering and Technology

(IJCIET), 4(5), 2013, pp. 168–180.

[27] N. Sundar, P. N. Raghunath and G. Dhinakaran, Flexu ral Behavior of RC beams with Hybrid FRP

Strengthening. International Journal of Civil Engineering and Technology (IJCIET), 7(6), 2016,

pp.427–433.