Journal Short Title (2014) 1-10 © STM Journals 2013. All Rights Reserved Page 1
An Experimental Investigation on Energy Absorption
Capacity of SFRSCC Exterior Beam Column Junction
Manjunatha K 1, Nambiyanna B2* and R.Prabhakara 3
1P.G. Student, Civil Engineering, Ramaiah Institute of Technology Bangalore, India 560054. 2 Assistant Professor, Civil Engineering, Ramaiah Institute of Technology Bangalore, India 560054 3Professor Emeritus Structural Engineering Division PG Center, VTU Belagavi, Karnataka 590 018
Earthquakes damages in concrete structure revealed that the importance of design of reinforced concrete
structure with high ductility. Strength and ductility of structure depend mainly on proper detailing of the
reinforcement in beam-column joints. For adequate ductility of beam column joints, use of closely spaced
hoops as transverse reinforcement was recommended which increases congestion of steel in joints. Due to
its specific properties, self-compacting concrete (SCC) gets dense and compacted due to its own self
weight in congestion reinforcement of beam column joints. Arresting of multiple cracks, fibres are added
in concrete has been shown to increase in ductility and energy absorption capacity. The present
experimental investigation aims to study the behaviour of RC exterior beam column joint under static load
using Steel Fibre Reinforced Self Compacting Concrete (SFRSCC). Exterior beam column joint has been
designed and detailed according to IS 456-2000 code. Normal Strength Concrete (NSC) designed as per IS
10262:2009 and SCC designed as per Nan Su method. Total 14 specimens were casted by varying aspect
ratio and percentage of fibre in NSC and SCC. Various aspects such as ultimate load carrying capacity,
deflection, crack width, ductility and energy absorption have been studied.
Keywords: Crack width, ductility, energy absorption, exterior joint, steel fibre self-compacting
*Author for Correspondence E-mail: [email protected] , Tel: 9886202241
In reinforced concrete buildings, portion of columns that are common to beams at their intersections
are called beam-column joint. Their constituent materials have limited strength; the joints have
limited force carrying capacity. Beam column joint plays a very important role in transferring the load
between the elements. There are three types of joints that can be identified, viz., interior joint, exterior
joint and corner joint. While comparing the three types of joints, exterior beam column joint will be
the most affected under any external loading 5. Proper design and detailing is required for better
performance of joints.
Due to the congestion of steel reinforcement at joint region, there is problem in compaction of
concrete which leads honeycombing in concrete and prevents the concrete to attain full compressive
strength 7. So using of Self consolidating concrete (SCC), a relatively new category of high
performance concrete is proportioned such that the concrete freely passes around and through
reinforcement, completely fills the formwork and consolidates under its own weight without
segregation. The high flow ability of SCC makes it possible to fill the formwork without vibration.
Due to the low water cement ratio, SCC should have improved to strength and durability.
Superior resistance of cracking and crack propagation of steel fibre, which helps to arrest cracks, fibre
composite possesses increased extensibility and tensile strength both at first crack and at ultimate,
particular under flexural loading 8. From the literature, it is noted that addition of steel fibres
improves the structural properties of beam column joint like strength, ductile, energy absorption and
crack arresting. Considering this, attempt has been made to investigate the behaviour of exterior beam
column joint with varying aspect ratio and percentage of fibre in NSC and SCC.
Article Short Title First Author Name
Journal Short Title (2014) 1-10 © STM Journals 2013. All Rights Reserved Page 2
Muthuswamy K.R, et al 4 Studied the effect of hybrid fibre reinforced concrete on exterior beam
column joint subjected to cyclic loading. Three types of reinforced cement concrete Exterior beam-
column joints, without fibre, with steel fibre and with hybrid fibre (steel & glass) were casted and
tested. The presence of hybrid fibres performed better and reduces the crack width and causes lesser
damages than that of conventional RC joint. The mode of failure of fibre reinforced joint was more
ductile than reinforced concrete joint.
Naveen Hooda, et al 8 conducted a comparative study on behaviour of exterior beam column joint
by providing different reinforcement detail, varying tie spacing and percentage of steel fibres under
monotonic load. The percentage of steel fibres was varied in volume fraction of 0.5%, 1% & 1.5%.
The investigation showed that the addition of steel fibres in the concrete mix improved structural
performance of beam column joint in terms of strength & ductility.
The following are the objectives carved from the literature review and gap analysis
1) To study the behaviour of exterior beam column joint with or without fibres.
2) To investigate the load deflection characteristics, load carrying capacity and energy
absorption capacity of sub-assemblies of steel fibre reinforced self-compacting concrete beam
column joint under static loads through experimental study.
3) To compare the behaviour of all the specimens with the effect of steel fibres in the beam
column joint under monotonic load and also to compare the various parameters like load
carrying capacity and energy absorption capacity.
Ordinary Portland cement 43 grade confirming to IS: 12269 (1987) was used. The fine aggregate used
was manufacture sand having a fineness modulus of 2.43. Fe-500 HYSD bars and undulated low
carbon cold drawn wire type V steel fibre was used.
Table 1: Materials
cementOrdinary Portland cement
specific gravity of 2.79
specific gravity of 2.39
Fly ashCLASS F FLY ASH
Super plasticizerGLENIUM B233
modifying agentGLENIUM STREAM 2
strength 700-900 MPa
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Mix proportions for M30 grade concrete
1) Normal Strength Concrete for M30 grade concrete mix were obtained based on the IS: 10262-2009,
the details of mix proportion thus obtained are given in table 2. The mix proportion used is 1:2.1:2.46
with W/C ratio 0.55.
Table 2 Mix design for M30 NSC
2) The self-compacting concrete for M30 grade of concrete mix design used in the present study was
based on Nan-su method. The main consideration in the Nan-su method is that voids present in loose
aggregates are filled with paste, and that the packing of the aggregates is minimized. This is achieved
by using more sand and less gravel (50-58%). Here it was investigated how maximum packing
achieved for different percentages and finally (S/a) volume ratio of fine aggregates to total aggregates
was 53% with a packing factor of 1.14.
In the present study, the various trial mixes were conducted from nan-su mix design methods of SCC.
To obtain SCC which satisfies various tests like filling ability test, passing ability test and segregation
resistance test etc. on fresh SCC, slump flow test, J-ring test, V-funnel test, L-box and U-box test
were to be conducted. After passing these tests, successful SCC mixes are arrived. From such
successful mixes, choose final mix of proportion after the cubes are cast and tested after 7 days and 28
days. The details of workability test results and mix proportion thus obtained are given in table 3 and
table 4 respectively.
TABLE 3: Workability test results for SCC
Table 4: Mix design for M30 SCC
lit/m3 Sl N.Prope rty of SCCLimitations Te st
T50 in seconds2-5 secs3.8 secs
J-Ring0-10 mm4 mm
U-Box (H2-H1)0 to 30 mm9 mm
L-Box blocking ratio (H1/H2)0.8 – 1.0
Slump flow in mm650 mm – 800 mm
V-funnel flow in seconds4-12 secs CementFly ashFACAWaterSPVMAFiber
Article Short Title First Author Name
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Designing and detailing of beam column joint specimen
Design of beam and column was designed as per specifications of IS 456:2000 and SP-16. The size of
column is 100mm x 210mm and length is 1000mm. The size of beam is 80mm x 180mm and length
of beam from the face of column is 600mm, Fig. 1(a) shows the detailing of beam column joint. In all
the specimens, reinforcement kept constant. In beam section 2 # 12 Ø and 1#8Ø at tension and 2#8 Ø
at compression. Shear reinforcement of two legged stirrups of 8 Ø at 150 mm c/c are provided. In
column section 4 # 12 Ø and Shear reinforcement of two legged vertical stirrups of 8 Ø at 150 mm c/c
are provided, Fig. 1(b) shows reinforcement cage.
Fig.1(a): Detailing of Beam column of joint Fig.1(b): Reinforcement cage
Preparation of formwork
Wooden moulds of required size were prepared and were used as formwork for casting of beam
column joint as shown in Fig. 2(a). The inside portion and corners of the moulds were properly
greased for easy detachment of formwork from specimen. Plastic cover has been attached at the
bottom of form work to easy detachment from the ground. Cover blocks of height 15mm were used at
the bottom of the form work above which the reinforcement cages were placed. Placing of concrete,
Curing and white wash of specimen as shown in Fig. 2(b), Fig. 2(c) & Fig. 2(d).
Mixing of concrete and casting of specimens
The constituents of the normal strength concrete and self-compacting concrete i.e., cement, fly ash,
sand, coarse aggregate, water, superplasticizer, VMA and steel fibres were calculated and mixed in
proportion. Pan mixer was used for mixing the constituents. Mixing was continued until a
homogenous mixture was obtained. The concrete from the mixer was taken in pans and was poured
into wooden moulds. For normal strength concrete needle vibrator was used to make sure it reached
all the parts of formwork. The concrete was filled into the moulds in 3 layers. After concreting was
finished, the top layer of beam column joint was levelled to get a smooth surface. For self-compacting
concrete top layer is levelled to smooth surface without any needle vibrator for compaction. 3 cubes
of size 100mm x 100mm x 100mm each were cast simultaneously during every mix.
After 24 hrs the beam column joint was demoulded and the cubes were removed from the moulds and
kept for curing. For a period of 28 days curing was done and wet gunny bags were used to prevent the
loss of moisture. Cubes were cured in curing tank. After curing the specimen was white washed for
proper visualization of crack pattern. This procedure was followed for the entire 14 specimens.
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Fig 2(a): Preparation of formwork Fig 2(b): Placing of concrete
Fig 2(c): Curing of Specimens Fig 2(d): White washing of Specimens
TESTING ARRANGEMENT AND PROCEDURE
After the curing period was completed, the beam column joints were white washed before mounting
to the loading frame. A typical loading arrangement is shown in the Fig.3.
Fig 3: Testing of Beam-column joint
Article Short Title First Author Name
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? The specimens were tested under a loading frame of 100 tones capacity.
? The exterior beam column joint specimens were tested for static loading. The specimens were
mounted and hydraulic jack was placed at the centre using plumb bob.
? An axial load of 280 KN which is the reduced scaled down load, was applied on column by
means of 500 KN hydraulic jack.
? A point load was applied to the beam end at a distance of 50 mm from end. Load was applied in
? The load-deflection curve has been plotted by using data acquisition system. The accuracy of the
deflection values were 10 readings per second.
? For every increment of load, the surface was checked for any visible cracks and if any were
marked using a marker pen.
? First crack width was measured immediately when crack appeared at surface of the specimen,
further crack propagation was measured for each interval of load and finally, maximum crack
width was measured at ultimate deflection.
? Test was continued till the specimen reached its ultimate failure.
? Specimens denotes with which type of concrete, aspect ratio and percentage of fibre. Example
specimen SCC [email protected]% denotes, SCC type concrete in which aspect ratio 20 and 0.5% of fibres
RESULTS AND DISCUSSION
Results were obtained from the test on beam column joint at 28 days. From all the NSC specimens,
ultimate load and corresponding deflection of specimens were found to increase as the fibres aspect
ratio and content increased, which ensures that ductility enhanced but specimens NSC [email protected]% and
NSC [email protected]% failed at early load when compared to other specimens which ensures that providing
of steel fibre is limited. From all the SCC specimens, specimens with fibres having better results when
compared to specimen without fibres. SCC [email protected]% and SCC [email protected]% specimens having
maximum ultimate load for corresponding deflection when compared to other specimens. Fig. 4(a)
and 4(b) shows a comparative graph of load-deflection curve for NSC and SCC specimens
respectively. Fig. 4(a) and 4(b) shows a comparative graph of load-deflection curve for NSC and SCC
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Fig.4(a): comparative load – deflection graph for NSC specimens
Fig.4(b): comparative load – deflection graph for SSC specimens
Energy absorption capacity and load carrying capacity
Significant increase in first crack load and ultimate load were found with the increase in fibre content
in both NSC and SCC specimens. In NSC specimens, the specimen NSC [email protected]% having maximum
load carrying capacity compared to other specimens. First crack load and ultimate load carrying
capacity of NSC [email protected]% is 201% and 165% more than that of NORMAL NSC specimens
respectively. In SCC specimens, specimen SCC [email protected]% having maximum load carrying capacity
compared to other specimens. First crack load and ultimate load carrying capacity of SSC [email protected]%
is 166% and 179% more than that of NORMAL SSC specimens respectively. Fig.5 shows load
carrying capacity of all specimens.
Fig.5: load carrying capacity of all specimens
Energy absorption is represented by the area enclosed under the load deflection curve. It was observed
that energy absorption capacity of specimen increased by adding fibres. Specimen NSC [email protected]% is
5.6 times more than NORMAL NSC specimen. Specimen SCC [email protected]% is 3.1 times more than
NORMAL SCC specimen. Fig.6 shows energy absorption of all specimens.
Journal Short Title (2014) 1-10 © STM Journals 2013. All Rights Reserved Page 8
Fig.6: energy absorption graph of all specimen
Based on the observation from the experimental results the following conclusions are drawn
? The ultimate load carrying capacity of SCC [email protected]% specimen was 2.6 times more than
specimen without fibre in SCC.
? It was observed that specimens with fibres, the cracks were few with reduced crack width.
? Addition of fibres in concrete decreases the crack width up to aspect ratio fibres of 20, further
crack width increased with increases in aspect ratio of fibre.
? The energy absorption capacity of specimen increased by adding fibres. Specimen NSC
[email protected]% is 5.6 times more than NORMAL NSC specimen. Specimen SCC [email protected]% is 3.1
times more than NORMAL SCC specimen.
We sincerely thank management, CE, Principle and Head of department of Civil engineering Ramaiah
Institute of Technology, Bengaluru-560054, affiliated to VTU, Belgaum for the facility provided to
conduct the experimentation and all the technical guidance.
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