Comparative Study of Static and Dynamic Seismic Analysis of Multistoried RCC Buildings by ETAB

Gauri G. Kakpur. Int. Journal of Engineering Research and Application www.ijera.com
ISSN : 2248-9622, Vol. 7, Issue 5, ( Part -5) May 2017, pp.46-51
www.ijera.com DOI: 10.9790/9622-0705054651 46 | P a g e
Comparative Study of Static and Dynamic Seismic Analysis of
Multistoried RCC Buildings by ETAB
Gauri G. Kakpure*, Dr. A. R. Mundhada**
*PG Student, Department of Civil Engineering, P.R.M.I.T. & R., Badnera, SGBAU Amravati, India.
** Professor, Civil Department, P.R.M.I.T. & R., Badnera, Sant Gadge Baba Amravati University, India.
ABSTRACT
Reinforced Concrete (RC) building frames are most common types of constructions in urban India. These are
subjected to several types of forces during their lifetime, such as static forces due to dead and live loads and
dynamic forces due to earthquake. In the present work, two tall buildings (a G+10 and a G+25 structure),
presumed to be situated in seismic zone III, are analyzed by using two different methods viz. equivalent static
analysis method and response spectrum method, using ETAB 15 software. From analysis results, the parameters
like storey drift, storey displacement, Axial Load, Bending Moments are determined for comparative study.
Results established the superiority of the Response spectrum method over the Equivalent static analysis method.
Keywords: RCC Buildings, Equivalent Static Analysis Method, Response Spectrum Method, Story Drift
I. INTRODUCTION
A natural calamity, an earthquake has
taken toll of millions of lives through the ages,
in the unrecorded and recorded history. A disruptive
disturbance that causes shaking of the surface of
the earth due to underground movement along a
fault plane or from volcanic activity is called
earthquake. The earthquake ranks as one of the most
destructive events recorded so far in India in terms
of death toll & damage to infrastructure last hundred
years. All over the world, there is a high demand for
construction of tall buildings due to increasing
urbanization and spiraling population, and
earthquakes have the potential for causing the
greatest damage to tall structures. Since the
earthquake forces are random in nature and
unpredictable, the engineering tools need to be
sharpened for analyzing structures under the action
of these forces. Structural analysis is mainly
concerned with finding out the behavior of a
structure when subjected to some action. This action
can be in the form of load due to weight of things
such as people, furniture, wind, snow etc. or some
other kind of excitation such as earthquake, shaking
of the ground due to a blast nearby, etc. The
distinction is made between the dynamic and static
analysis on the basis of whether the applied action
has enough acceleration in comparison to the
structure's natural frequency.
In the present work, two tall buildings (a
G+10 and a G+25 structure), presumed to be situated
in seismic zone III, are analyzed using two different
methods viz. equivalent static analysis method and
response spectrum method, using ETAB 15
software.
II. METHOD OF ANALYSIS
A. Equivalent Static Analysis
Analysis against earthquake effects must
consider the dynamic nature of the load. However,
for simple & regular structures, analysis by
equivalent linear static analysis method is often
sufficient. This is permitted in most codes of
practice for regular, low- to medium-rise buildings.
B. Response Spectrum Method.
The method represents the maximum
response of an idealized single degree freedom
system having certain time period and damping,
during earthquake ground motions. The maximum
response plotted against an un-damped natural
period and for various damping values can be
expressed in terms of maximum absolute
acceleration, maximum relative velocity or
maximum relative displacement.
III. Modeling and Analysis
In the present work, two models of a G+10
and a G+25 story public building are analyzed as
special moment resisting frames. The buildings are
assumed to be situated in earthquake zone III. The
rectangular plan dimension is 20.1 x 27.6 m. Grade
of concrete used is M 30 and Grade of steel is Fe
500. Floor to floor height is taken as 3.2 m. Slab
thickness (S1) is 150 mm. External wall thickness is
taken as 230 mm. Internal wall thickness is assumed
to be 115 mm. Building is assumed to be resting on
hard soil. Density of plastered masonry wall is
assumed as 20 kN/m³. For G+10 building, Beam size
is taken as 230 x 400 mm whereas the column size is
taken as 700 x700mm at G. L. (reduced to 600x600
RESEARCH PAPER OPEN ACCESS

mm after 4 storeys & 500 x 500 mm after 8 storeys).
For G+25 building, beam size is taken as 230 x 500
mm whereas the column size is taken as1000 x 1000
mm at base. After each 5th
storey, column size is
reduced by 100mm to 900 x 900 mm, 800 x 800
mm, 700 x 700 mm & finally to 600 x 600 mm
respectively.
Fig.1: Plan of building
IV. Results and Discussion
The above two RCC frame structures are
analyzed both statically and dynamically and the
results obtained are graphically shown below.
A. Comparison of Storey Drift
Fig. 2: Comparison of Storey Drift (G+10)
From Fig. 2 for x direction, it is observed
that the maximum storey drift in Response spectrum
analysis (RSx) is 21.17% less than Equivalent Static
Analysis (Ex) method. Similarly, for Y-direction it is
observed that the storey drift in Equivalent Static
Analysis (Ey) is 21.33 % more than the storey drift
in Response Spectrum Analysis (RSy).
Fig. 3: Comparison of Storey Drift (G+25)
From Fig. 3 for x direction it is observed
that the maximum storey drift in Response spectrum
analysis (RSx) is 24.12 % less than Equivalent Static
observed that the maximum storey drift in Response
Spectrum Analysis (RSy) is 23.10% less than the
corresponding storeys drift in Equivalent Static
Analysis (Ey).
B. Comparison of Storey Displacement
Fig. 4: Comparative Storey Displacement (G+10)
From Fig. 4, for x direction, it is observed
that the maximum storey displacement in Response
spectrum analysis (RSx) is 22.74% less than
Equivalent Static Analysis (Ex) method. Similarly,
for Y-direction it is observed that the storey
displacement in Response Spectrum Analysis (RSy)
is 22.93% less than the storey displacement in
Equivalent Static Analysis (Ey).
Fig. 5: Comparative Storey Displacement (G+25)

From Fig. 5 for x direction, it is observed
that the maximum storey displacement in Response
spectrum analysis (RSx) is 26.88% less than
for Y-direction it is observed that the storey
displacement in Response Spectrum Analysis (RSy)
is 25.94 % less than the storey displacement in
Equivalent Static Analysis method (Ey).
C .Comparison of axial load for Columns
From Fig. 6, it is observed that the axial
load for corner column A1 in Response spectrum
analysis (RSx) is 7% less than Equivalent Static
observed that the axial load for column
A1inResponse Spectrum Analysis (RSy) is 8% less
than Equivalent Static Analysis value (Ey).
Fig. 6: Max axial load for corner column A1 (G+10)
From Fig. 7 below, it is observed that the
axial load for peripheral column C1 in Response
spectrum analysis (RSx) is 5% less than Equivalent
Static Analysis (Ex) method. Similarly, for Y-
direction it is observed that Peripheral column load
C1 in the Response Spectrum Analysis (RSy) is 7%
less than Equivalent static method.
Fig. 7: Max load for peripheral column C1 (G+10)
axial load for interior column B2 in Response
spectrum analysis (RSx) is 2 % less than Equivalent
Static Analysis (Ex) method for a G+10 building.
Similarly, for Y-direction it is observed that interior
column B2 load in the Response Spectrum Analysis
(RSy) is 2% less than Equivalent Static Analysis
value (Ey) for the same building.
Fig. 8: Max load for interior column B2 (G+10)
Fig. 9: Max Load for Corner Column A1 (G+25)
From Fig. 9 above, it is observed that the
axial load for corner column A1 in Response
Similarly, for Y-direction it is observed that column
A1 in Response Spectrum Analysis (RSy) carries 7
% less load than Equivalent Static Analysis (Ey).
Fig. 10: Max load for peripheral column C1 (G+25)
axial load for peripheral column C1 in Response
direction it is observed that Peripheral column load
C1 in the Response Spectrum Analysis (RSy) is 7 %
less than Equivalent Static Analysis (Ey).

Fig. 11: Max load for interior column B2 (G+25)
axial load for interior column B2 is approximately
same in Response spectrum analysis (RSx) and
for Y-direction it is observed that interior column
load B2 in the Response Spectrum Analysis (RSy) is
just 1% less than Equivalent Static Analysis (Ey).
D.Comparison of Beam End B. M.
Fig. 12: Max. B. M. for beam A1B1-1A2A (G+10)
bending moment for end beam A1B1in Response
spectrum analysis (RSx) is 6 % lesser than
for Y-direction end beam 1A2A has 5% less moment
than Equivalent Static Analysis (Ex) method. From
Fig. 13 below, it is observed that the bending
moment for peripheral beam B1C1 in Response
direction peripheral beam 1B2B has 6% less
moment from Response Spectrum Analysis (RSy)
than Equivalent Static Analysis (Ey) method.
Fig. 13: Max. B. M. for beam B1C1-1B2B (G+10)
From Fig. 14, it is observed that the
bending moment for internal beam B2C2 in
Response spectrum analysis (RSx) is 4% less than
for Y-direction internal beam 2B3B in Response
Spectrum Analysis (RSy) has 7% less moment than
Equivalent Static Analysis value (Ey).
bending moment for end beam A1B1 in Response
Similarly, For Y-direction end beam 1A2A, B. M. in
Response Spectrum Analysis (RSy) is 3% less than
Equivalent Static Analysis (Ey), for the same
building.
Fig. 15: Max. B. M. for beam A1B1-1A2A (G+25)

From Fig 16 above, it is observed that the
bending moment for peripheral beam B1C1 in
Equivalent Static Analysis (Ex) method in case of a
G+25 building. Similarly, For Y-direction
peripheral beam 1B2B, B. M. in Response Spectrum
Analysis (RSy) is 3% less than the corresponding
Equivalent Static Analysis value (Ey).
From Fig17 above, it is observed that the
bending moment for internal beam B2C2 in
Equivalent Static Analysis (Ex) method for a G+25
building. Similarly For Y-direction, B. M. for
internal beam 2B3B in Response Spectrum Analysis
(RSy) is 3% less than Equivalent Static Analysis
(Ey) value.
V. CONCLUSION
i. Storey drift value for G+10 and G+25 are
22 to 25% less respectively, in dynamic
analysis than static analysis. All the values
are within the limits as per code
requirement.
ii. As the height of storey increases, the
displacement values too gradually increase.
Top storey has maximum displacement
value in both X-Y directions. For dynamic
analysis, storey displacement for G+10 and
G+25 buildings are 22 % & 26% less than
the corresponding values in static analysis.
iii. Axial load for corner column and peripheral
columns in G+10 and G+25 are 7% to 8%
less in dynamic analysis than static
analysis. However, axial load for interior
column in G+10 and G+25 are only @2%
less in dynamic analysis than static analysis
iv. Bending Moment for beams in G+10
building is 3% to7 % lesser than its static
analysis counterpart. However, in G+25
building the difference is even lesser at 3%
to 4% in dynamic analysis than static
analysis
v. Dynamic analysis gives lesser values for all
parameters than static analysis. Hence,
dynamic analysis is economical.
REFERENCES
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Static And Dynamic Loading Condition
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[2] Anirudh Gottala, Dr.shaik Yajdhani
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[8] E.Pavan Kumar,A.Naresh Earthquake
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pp.59-64

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