Performance Based Analysis of Concealed Beam in Reinforced Concrete Structure

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 06 | June -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 2193
Performance Based Analysis of Concealed Beam in Reinforced Concrete
Structure
Chetan Talawar 1, Hemant Sonawadekar 2
1 Post-Graduate Student, Dept. of Civil Engineering, KLE Dr MSSCET, Belagavi-590008, India
2 Assistant Professor, Dept. of Civil Engineering, KLE Dr MSSCET, Belagavi-590008, India
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Abstract- Beams are the structural elements and transfers
the load from slabs to columns. If the slab panels are very
large, the intermediate beams are used to convert them into
small panels. The dimensions of the beam depend on the load
from the slab. The HIDDEN BEAMS are widely used in
construction of multi-storey buildings because of the
advantages like, they provide more clearance between the
floor, they also save on formwork, labor and constructioncost.
In the present study the seismic behavior of the reinforced
concrete structure with and without concealed beam is
described. The various models of G+4 storey and G+6 storey
are modeled and analyzed in ETABS 09. The response
spectrum analysis is carried out as per IS 1893:2002 by
considering the seismic zone as ZONE II and medium soil.
Further the pushover analysis is carried out as per FEMA 356
and ATC-40. The parameters like Base Shear, Axial loads,
Natural period, Displacement are considered and comparison
is done between the models with and withoutconcealedbeam.
Key Words: ETABS 09, Concealed Beam, Response
Spectrum method, Pushover Analysis,PerformancePoint.
1. INTRODUCTION
The loads acting on the multi-story building are
Gravity loads (Dead load of the structure, Live load, Snow
load) and Lateral loads (earthquake and wind loads). In
earlier days only gravity loads are used to design the multi-
story buildings, but other than the gravity loads the
Horizontal loads are also act on the buildings. Now a day’s
design of the multi-story building is done by consideringthe
both Gravity loads and Lateral loads for the safety purpose.
The depth of the concealedbeamwill be equal tothe
thickness of the slab and it is hidden in the slab hence
Concealed beam is known as HIDDEN BEAM. The top levels
of the both slab and the hidden beam will be same. Concept
of concealed beam originated from flat slab. Thebeamrebar
is designed for the same depth of the slab. The concealed
beams are used to provide maximum clearance betweenthe
floors because of this hidden beams are widely used in
commercial buildings. When the concealed beams are
provided the beam-column joint is similar to the flat slab of
slab-column joint. Both buildings have the same appearance
but acts differently when considered resistance to gravity,
earthquake and wind loads.
Fig 1- Concealed Beam
2. MODELING AND BUILDING DATA
Fig 2- Building Plan

Fig 3- Building elevation
2.1 Building Data
Plan 9mX9m
Slab panel 3mX3m
Floor Height 3m
Column 450mmX450mm
Normal Beam 300mmX300mm
Concealed Beam 250mmX300mm
Slab thickness 250 mm
Grade of Concrete M20
Grade of Steel Fe 415
Wall Load on Perimeter Beam 13.8 kN/m
Wall Load on Intermediate
Beams
9 kN/m
Parapet wall load 3kN/m
Floor Finish(FF) (Assumed) 1kN/m2
Floor Live Load 3kN/m2
Roof Live Load 1.5kN/m2
Type of soil Medium Soil
Type of Structure SMRF
Damping ratio 5% (RC Structure)
Importance Factor (I) 1 (Table 6)
Response Reduction Factor 5 (Table 7)
3 : Analysis of the Building
Response spectrummethodisusedintheanalysisof
multi-storey building with and without concealed beam. In
response spectrum method, dynamic characteristics are
considered. Base shear is calculated by multiplying total
seismic weight with acceleration spectrum coefficient. Base
shear is calculated according to IS 1893 (Part 1) -2002.
RS X – Response Spectrum in X direction,
RS Y – Response Spectrum in Y direction.
3.1 Results and Discussion
3.1.1 Base Shear
No of
Storeys
Type of model
Base Shear
(kN)
G+4
without concealed beam 311.38
with concealed beam 295.65
G+6
Fig 4-Base shear Comparison
The base shear of the model with normal beam is
more than the model with concealed beam.
3.1.2 Natural Period
No of
Storeys
Type of model
Natural
Period
(sec)
G+4
G+6

Fig 5- Natural period Comparison
The Natural period of the model with concealed
beam is more than the model with the normal beam because
the stiffness of the concealed beam model is less than the
normal beam model.
3.1.3 Displacement
No of
Storeys
Type of model displacement
(mm)
G+4
G+6
Fig 6- Displacement Comparison
The depth of the concealed beam is less than that of
the normal beam because of this reason the weight of the
structure reduces. The stiffness of the whole structure
reduces in structure with concealed beam. Hence the
displacement of the top storey in models with concealed
beam is more than the models with normal beams.
3.2 Pushover Analysis
As the name pushover indicates, push the structure
with certain magnitude until itreachesmaximumcapacityto
deform. In this process the load on the structure is gradually
increased with certain pre-defined pattern. As the load on
the structure increases the yielding of the structure begins
and finally gets damaged and failure modes of the structure
becomes apparent. The effect of load reversal on the
structure during earthquake is analyzed by applying load
monotonically and deformation of the structureisestimated
with suitable damping. The aim ofthepushoveranalysisisto
understand the deformation andcrackingofthestructure.In
pushover analysis the plastic hinges are assigned to the
beams and columns at either ends. The hinges should be
studied carefully during the collapse mechanism and the
performance point may be observed. The hinges are
assigned to the beams and columns of the structure as per
the guidelines given in ASCE 41. For the beams the flexural
hinge (M3) and shear hinge (v2) are assigned at both the
ends at relative distance. Similarly, for the columns the
combination of axial and flexural hinges (P-M2-M3) are
assigned at both the ends with relative distance. At the
distance of 0.05 and 0.95, the hinges are assigned to the
beams and columns.
3.2.1 Performance point
The intersection of the capacity curve and the
demand curve is called as Performance point. The plotofthe
base shear of the structure to the roof displacement is called
as Capacity curve. and Capacity curve is also known as
Pushover curve.
Fig 7-Performane point fot G+4 model with concealed
beam

Fig-8 Hinge formation in G+4 model with concealed beam
The first hinge formed in beams and as the load
increases the hinges started forming in columns. Thisshows
weak beam and strong column concept. By observing the
hinges, most of the hinges are in Life safety zone. In model
G+4 storey without concealed beam, the formation ofhinges
taken place in earlier steps than the model with concealed
beam. In both the models bottom storey columns are having
more number of life safety hinges hence retrofitting of
columns has to be done.
Fig 9-Performane point fot G+6 model with concealed
beam
Fig-10 Hinge formation in G+4 model with concealed
beam
The base shear of the model without concealed
beam is more than the model with concealed beam. The roof
displacement, Spectral displacement,effectivetimeperiodof
the model with concealed beam is more and Spectral
acceleration is more for the model without concealed beam.
In model G+6 with concealed beam, the formation of hinges
took place in later steps than the model without concealed
beam. The retrofitting is required for the bottom storey
columns of the both the models since life safety hinges are
formed more.
5. CONCLUSIONS
Following conclusions are drawn from the present study
 The base shear of the concealed beam structure is less as
compare to normal beam structure. Since lesserthemass
lesser will be the seismic force. Hence it is concludedthat
concealed beam structure is better than normal beam
structure during earthquake.
 The influence of concealed beam in a structure increases
the natural period as compared to normal beam
structure.
 In multi-storey structures, if long spanslabsareprovided
the deflection will be more. The concealed beams are
provided in order to decrease the deflectionandincrease
the stiffness of the slab.
 In multi-storey building provision of concealedbeamcan
act as a flat slab and provides large clearance in between
the floors.
 As the damping value increases, the inelastic
displacement of the structure decreases due overall
increase in the structural stiffness. As the damping
increases, the capacity of the structure increases.

 The more number of life safety (LS) hinges are formed in
model with concealed beams as compared to model with
normal beams. hence performance of the model with
concealed beams is better than model with normal
beams.
ACKNOWLEDGEMENT
The authors would like to thank Shri S. C. Metagud
Chairman Governing council, K.L.E.M.S.S.C.ET and Dr.
Basavaraj G. Katageri principal of K.L.E.M.S.S.C.ET, Belagavi
for their kind support and providing good infrastructure.
The authors are grateful to Prof. (Smt) Bharati Chiniwalar,
Head of Civil Department, for encouragement and support.
REFERENCES
 Akash.C. Arakere, Tejas D. Doshi, “Comparison of Multi-
Storey Building with Normal Beams and Concealed
Beams”, International Research Journal of Engineering
and Technology (IRJET) e-ISSN: 2395 -0056, | June-2015
 Samir H. Riyaj Awad, “Performance based analysis of
Hidden Beams in Reinforced Concrete Structure”, An-
Najah National University, Nablus, Palestine.
 Samir H. Helou, Munther M. Diab, “Slabs with Hidden
Beams”, An-Najah National University, Nablus, Palestine.
 Navyashree K, Sahana T.S, “Use of flat slabs in multi-
storey commercial buildingsituatedinhighseismiczone”,
International Journal of Research in Engineering
and Technology, eISSN: 2319-1163, August, 2014.
 M. Altus ERBERIK, Amr S. ELNASHAI, “Vulnerability
analysis of flat slab structures”, 13th World Conference
on Earthquake Engineering, August, 2014.
 Sumit Pahwa, Vivek Tiwari and Madhavi Prajapati,
“Comparative Study of Flat
Slab with Old Traditional Two-way slab”, International
Journal of Latest Trends
 Federal Emergency ManagementAgency,FEMA-356:Pre
standard and Commentary for the Seismic Rehabilitation
of Buildings, 2000: Washington DC.
 Federal Emergency Management Agency, FEMA-440:
Improvement of Non-linear Static Seismic Analysis
Procedures, June-2005: Washington DC.
 ATC -40, ‘Seismic Evaluation and Retrofit of Concrete
Buildings’, Vol. 1&2, Applied Technology Council,
California, 1996
BIOGRAPHIES
Chetan Talawar
Post-Graduate Student,
Department of Civil Engineering,
K.L.E. Dr.M.S.Sheshigiri College of
Engineering and Technology,
Belagavi, India- 590008
Prof. Hemant Sonawadekar
M.Tech (Structural Engineering),
B.E (Civil),
Assistant Professor,
Department of Civil Engineering,
K.L.E. Dr.M.S.Sheshigiri College of
Engineering and Technology,
Belagavi, India- 50008

Performance Based Analysis of Concealed Beam in Reinforced Concrete Structure

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Performance Based Analysis of Concealed Beam in Reinforced Concrete Structure