Analytical Investigation on External Beam-Column Joint Using ANSYS By Varying The Diameter Of The Longitudinal Reinforcement In Beam

Harish R et al. Int. Journal of Engineering Research and Applications www.ijera.com
ISSN: 2248-9622, Vol. 5, Issue 8, (Part - 1) August 2015, pp.01-05
www.ijera.com 1 | P a g e
Analytical Investigation on External Beam-Column Joint Using
ANSYS By Varying The Diameter Of The Longitudinal
Reinforcement In Beam
Harish R*, Nambiyanna B**, Dr. R Prabhakara***
*(PG Scholar, Department of Civil Engineering, MS Ramaiah Institute of Technology, Bangalore- 54)
**(Assistant Professor, Department of Civil Engineering, MS Ramaiah Institute of Technology, Bangalore- 54)
***(Professor & HOD, Department of Civil Engineering, MS Ramaiah Institute of Technology, Bangalore- 54)
ABSTRACT
The beam-column joint has been a topic of study for over 30 years now and still there are many things that yet to
be completely understood. The joint was considered to be rigid, however researches have shown that failure may
occur at the joint instead of the beam or column. This study was carried out to determine the effect of the
diameter of longitudinal reinforcement of the beam on the strength, deformation and ductility in the beam-
column joint using ANSYS. It was seen that the load carrying capacity and the deformation increases as the
diameter of reinforcement in the beam increases.
Keywords – ANSYS, Beam-column Joint, Diameter of Reinforcement, Finite Element
I. INTRODUCTION
The beam-column joint (BCJ) is one of the most
critical region in a multi-storey building. The beam-
column joint were usually considered as rigid frames.
But over the past 30 years, various researches have
indicated that the joint is not rigid. Also, the failure
may occur at the joint instead of the beam or the
column, hence the joint must also be considered as a
structural element. The Indian Standard defines a
joint as the portion of the column within the depth of
the deepest beam that frames into the column.
Computer simulation offers the potential to
understand the behavior of the RCC beam-column
joint to various loadings. The research presented here
focuses on ANSYS software to investigate the beam-
column joint. The current research aims to study the
effect of the variation of diameter of the longitudinal
reinforcement in the beam in an exterior beam-
column joint.
The literature on the above topic were less
however some of the literature which are very near to
the topic are given below :
Scott et. Al. [1] performed studies by varying the
reinforcement pattern using bent up, bent down and
U-bars. It was observed that the U-bars show highest
load carrying capacity while the bent up and bent
down bars fail due to pull out.
Kang and Mitra [2] proved that the increasing
development length, head thickness, head size and
decreasing joint shear demand gives better beam-
column joint performance.
Murty et al [3] have tested the exterior beam
column joint subject to static cyclic loading by
changing the anchorage detailing of beam
reinforcement and shear reinforcement. It was
reported that the practical joint detailing using
hairpin-type reinforcement is a competitive
alternative to closed ties in the joint region.
II. DETAILS OF SPECIMEN
The six beam-column joints which were
analysed in the CAD lab of Civil Engineering Dept.
research centre at MSRIT were modeled and run
using ANSYS. Each joint was designed as IS 456:
2000 and detailed as per SP34: 1987.
All the six beam-column joints had identical
beam and column sizes. The beams were 160 mm
wide and 230 mm deep and the columns are 230 mm
by 160 mm. The column height was fixed to 1000mm
and the beam length was fixed at 600mm. The clear
cover for the reinforcement was considered as 25
mm. The 28 day cube strength of concrete was taken
as 42.85 N/mm2. The yield stress in steel was
considered to be 500 N/mm2. The details of the
specimen can be seen in fig 1.
(i) 8 mm Longitudinal reinforcement
RESEARCH ARTICLE OPEN ACCESS

(ii) 10 mm Longitudinal Reinforcement
(iii) 12mm Longitudinal Reinforcement
Fig. 1 : Reinforcement Details of Beam-Column Joint
III. ANALYTICAL MODEL
3.1 Elements for ANSYS
The beam-column joint was modelled in ANSYS
with SOLID 65 and LINK 180 elements. The SOLID
65 was used to model the concrete. The LINK 180
was used to model the reinforcement in the concrete.
The various parameters required in modeling is
shown in table 1.
Table 1: Material Properties and Element types for
ANSYS
Material
Number
Element Type
Material
Properties
1 Link 180
Linear
Isotropic
Ex
2100000
N/mm2
Prxy 0.3
Bilinear Kinematic
Yield Stress 500 N/mm2
Tangent Modulus 10
2
Solid – Concrete
65
Linear Isotropic
Ex - M 30 32729.96
N/mm2
Prxy 0.2
Concrete
Shear Transfer Coeffecients for an
Open Crack
0.3
Shear Transfer Coeffecients for a
Closed Crack
0.7
Uniaxial Cracking Stress 4.58 N/mm2
Uniaxial Crushing Stress 42.85 N/mm2
Typical shear transfer coefficients represent
conditions of the crack face, It has value ranges from
0.0 to 1.0, with 0.0 representing a smooth crack
(complete loss of shear transfer) and 1.0 representing
a rough crack ( no loss of shear transfer). The shear
transfer coefficients for opened and closed cracks are
determined using the work of Kachlakev, et al.
(Kachlakev 2001) as a basis.
3.2 Modeling In ANSYS
The beam-column joint was modeled in ANSYS
using the above material properties and element
types. The column was considered to be fixed and a
constant axial load of 130 kN, which was the
calculated working load, was applied at the top of the
column. The column was fixed at the top and the
bottom. The load at the beam was applied at a
distance of 100 mm from the free end of the
cantilever portion, in incremental proportions. Even
though the load can be applied at the centroid of the
structure, the loads are applied at the respective
points in order to simulate the actual behavior of the
beam-column joint. The models were analysed
applying monotonic load in the downward direction.
The mesh size was fixed at 25mm. A total of 6 beams
were analysed. The variation made for the beam-
column joint were variation of diameter of
longitudinal reinforcement and the shear
reinforcement. The details of the joints are given
below in table 2. Fig 2 represents the ANSYS
models.
Table 2: Details of Reinforcement for the specimen
Specimen
Set
No.
Column
Reinf.
Beam Reinforcement
Longitudinal Shear
BCJ 1 1
4 Nos-
16ɸ
6 Nos - 8ɸ
8mm@
100c/c
BCJ 2 1
4 Nos-
16ɸ
4 Nos – 10 ɸ
8mm@
100c/c
BCJ 3 1
4 Nos-
16ɸ
3 Nos – 12 ɸ
8mm@
100c/c
BCJ 4 2
4 Nos-
16ɸ
6 Nos - 8ɸ
8mm@
150c/c
BCJ 5 2
4 Nos-
16ɸ
4 Nos – 10 ɸ
8mm@
150c/c
BCJ 6 2
4 Nos-
16ɸ
3 Nos – 12 ɸ
8mm@
150c/c

(i) Meshed Model in ANSYS
(ii) Reinforcement Configuration
Fig 2: ANSYS modelling
IV. RESULTS AND DISCUSSION
4.1 Load Deflection Characteristics
The load deflection characteristics for 6 exterior
beam column joints which were analysed are shown
in figure 3. It was seen that as the diameter of the
longitudinal reinforcement increases, the cracking
load and the ultimate load carrying capacity reduces
as seen in table 3 ( BCJ 1 to BCJ 2 to BCJ 3, BCJ 4
to BCJ 5 to BCJ 6). It was observed that normalizing
of loads are necessary as the area of steel provided is
not constant, the normalized Ultimate load and
Cracking load are shown in table 3. Fig 3, shows the
combined load deflection characteristics of the joints.
From the cracks, in Fig 4., it can be seen that the
failure occurs at the beam and not at the junction.
This implies that the beam-column joint has been
designed as a strong column weak beam and the
plastic hinge is formed in the beam.
Fig 3 : Load Deflection Graph
Table 3: Normalized Loads
Specimen
Set
No
Ultimate Load
(kN)
Cracking Load
(kN)
BCJ 1 1 58.38 9.08
BCJ 2 1 58.12 8.80
BCJ 3 1 54.95 8.22
BCJ 4 2 57.03 9.09
BCJ 5 2 56.95 8.67
BCJ 6 2 52.87 8.14
Fig 4: Cracks in Beam Column Joint
4.2 Ductility Characteristics
Ductility is generally measured in terms of
displacement ductility. It is the maximum
deformation a structure can undergo without
significant loss of initial yielding resistance. It is the
ratio of maximum deformation to the deformation at
yield.
The displacement ductility for the six specimen
are given in table 4 along with the yield deformation

and ultimate deformation. The plot of ductility vs
reinforcement percentage shows that as the diameter
of reinforcement increases, the ductility reduces. And
as the shear reinforcement spacing is reduced the
ductility reduces. This can be observed in fig. 5. To
determine the yield deformation, bilinear method of
approximation was used as shown in fig 6. It is
observed that ductility of the joint reduces as the
diameter of the longitudinal reinforcement increases.
Table 4 : Ductility of Beam-Column Joints
Specimen
Set
No.
Displacement Disp.
Ductility
(μd)
Yield
(Δy)
Ultimate
(Δu)
BCJ 1 1 3.89 9.71 2.50
BCJ 2 1 4.34 10.45 2.41
BCJ 3 1 3.87 8.45 2.18
BCJ 4 2 3.3 9.62 2.92
BCJ 5 2 3.93 10.52 2.68
BCJ 6 2 3.64 8.21 2.26
Fig 5: Ductility versus Reinforcement
Fig 6: Bilinear Method For Ductility
4.3 Deflection at Working Load
The deflection at working load is shown in table
5.
Specimen Set Pcr (kN)
Deflection
(mm)
BCJ 1 1 9.08 2.22
BCJ 2 1 8.80 2.45
BCJ 3 1 8.22 2.87
BCJ 4 2 9.09 2.37
BCJ 5 2 8.67 2.52
BCJ 6 2 8.14 2.97
V. CONCLUSIONS
The following conclusions are drawn from the
study of the external beam-column joint applying
monotonic load:
(i) The cracking load reduces as the diameter of the
bar increases. For set 1 the reduction from 8mm to
10mm bars was 3% and for 8mm to 12mm was 10%.
Whereas for set 2, for 8mm to 10mm it was 4.76%
reduction and from 8mm to 12mm it was 10.43%.
(ii) The load deflection characteristics show that at
working load, as the diameter increases the deflection
increases.
(iii) The ductility of the joint reduces as the diameter
of the bar increases. For set 1, the ductility reduces
by 3.6% for 8mm to 10mm and there was reduction
by 12.8% from 8mm to 12mm. Also for set 2, the
ductility reduces by 8.21% for 8mm to 10mm and
there was reduction by 29% for 8mm to 12mm. Also
it was seen as the spacing of stirrups decrease the
ductility reduces, comparing BCJ 1 and BCJ 4 there
was an increase in ductility by 14.38%.
(iv) The displacement at working load increases as
the diameter of the reinforcement increases. The
deflection for set 1, increases by 10.36% for 8mm to
10mm bars and increases by 27.28% for 8mm to
12mm. For set 2, it was seen that the deflection
increases by 6.30% for 8mm to 10mm and there was
an increase of 25.32% for 8m to 12mm bars.
(v) The ultimate load carrying capacity also decreases
as the diameter of the bar increases. For set 1 the
reduction of ultimate load for 8mm to 10mm bars
was 3% and for 8mm to 12mm was 10%. Whereas
for set 2, the ultimate load carrying capacity for 8mm
to 10mm it was 4.76% reduction and from 8mm to
12mm it was 10.43%.
Thus, it is concluded that the diameter of the
longitudinal reinforcement in the beam plays a major
role in the behavior of the beam-column joint.
Further research can be carried out by considering
variation of column and beam dimension, varying the
percentage of steel and this will further enhance our
understanding of the beam-column joint.
VI. ACKNOWLEDGEMENT
We sincerely thank management, CE,Principal
and Head of Department of M.S.Ramaiah Institute of
Technology, Bangalore-560054, affiliated to VTU,
Belgaum for the facility provided to conduct the
analytical work and all the technical guidance.
REFERENCES
Design Standard Codes:
[1] BIS (2000). ―IS 456: 2000—Indian Standard
Plain and Reinforced Concrete—Code of
Practice (Fourth Revision)‖, Bureau of
Indian Standards, New Delhi.

[2] BIS (1987b). ―SP 34: 1987—Handbook on
Concrete Reinforcement and Detailing‖,
Bureau of Indian Standards, New Delhi.
Journal Papers:
[3] Scott, R. H. (1992). The Effects of Detailing
on RC Beam/Column Connection Behavior.
The Structural Engineer. Vol. 70 No. 18 :
318-324.
[4] Thomas H.K.Kang and Mitra N. (2012).
Prediction and performance of Exterior
Beam-Column Connections with the headed
bars subjected to load reversal. Engineering
Structures 41(2012) 209-217.
[5] Murty, C.V.R., Rai, D.C., Bajpai, K.K. and
Jain, S.K. (2003).―Effectiveness of
reinforcement Details in Exterior Reinforced
Concrete Beam-Column Joints for
Earthquake Resistance‖, ACI Structural
Journal, Vol. 100, No. 2, pp. 149–156.
[6] K.R. Bindhu, K.P. Jaya, ―Strength And
Behaviour Of Exterior Beam Column Joints
With Diagonal Cross Bracing Bars‖, Asian
Journal Of Civil Engineering (Building And
Housing) Vol. 11, No. 3 (2010) Pages 397-
410.
[7] Subramanian, N. and Rao, D.S.P. (2003).
―Seismic Design of Joints in RC
Structures—A Review‖, Indian Concrete
Journal, Vol. 77, No. 2, pp. 883–892.
[8] Marzouk, H., Mohamed Emam, and Hilal,
M. S. (1996). Effect of High-Strength
Concrete Columns on the Behavior of Slab-
Column Intersection. ACI Structural
Journal. Vol. 93 No. 5 : 545-554Text Books
[9] Park, R. and Paulay, T. (1975). “Reinforced
Concrete Structures”, John Wiley & Sons,
Inc., New York, U.S.A.
THESES
[10] Laura N Lowes, Niranjan Mitra, Arash
Altoonash (2004),” A Beam Column Joint
Model For Sumulating the Earthquake
Response of RC Frames.” Pacific
Earthquake Engineering Research Report,
University of California, Berkley

Analytical Investigation on External Beam-Column Joint Using ANSYS By Varying The Diameter Of The Longitudinal Reinforcement In Beam

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Analytical Investigation on External Beam-Column Joint Using ANSYS By Varying The Diameter Of The Longitudinal Reinforcement In Beam