Study of Earthquake Forces By Changing the Location of Lift Core

Shashwati Sanjay Vahadane et al. Int. Journal of Engineering Research and Application www.ijera.com
ISSN : 2248-9622, Vol. 6, Issue 6, ( Part -4) June 2016, pp.23-29
www.ijera.com 23 | P a g e
Study of Earthquake Forces By Changing the Location of Lift
Core
Shashwati Sanjay Vahadane*, Ashok W. Yerekar Sir **
* ME Student, Dept. of civil engineering, at People’s Education Society, College of Engineering Aurangabad.
** Professor at Dept. of civil engineering, Peoples Education Society, College of Engineering Aurangabad.
ABSTRACT
Lift core is an important element for strengthening of structure in earthquake prone area (Mw=6.5 or more).
This paper deals with use of lift cores to resist the seismic forces and its effect by changing the lift core location.
The study for G+5 and G+10 type frame buildings are taken under consideration. These buildings are further
subdivided as per soil strata i.e. hard, medium, and soft. Two locations of lift core considered for studies i.e.
centre core and corner core. Zone V is considered for all buildings which will cause maximum base shear to the
structure. Study is focused on comparative static and dynamic analysis which will show graphical
representation of G+5 and G+10 building along with soil type. Economy is studied in analysis.
Keywords: Lift core location, story drift, modal analysis, base shear, DBE.
I. INTRODUCTION
Earthquake is natural phenomena of
movement of underground tectonic plates which
releases tremendous amount of energy that leads
earth surface to vibrate. According to the theory of
Plate Tectonics, the entire surface of the earth can be
considered to be constantly on the move. These plates
brush against each other or collide at their boundaries
giving rise to earthquakes. Earthquakes became
frequent after the construction of Koyna Dam and this
is regarded as a classic case of man-made seismicity.
It was considered that earthquake may not occur on
hard rock ground but after the earthquake that occur
in Latur city (1993) which is considered to be the
most stable land in Maharashtra hence it can be
considered that Earthquakes are one of the
unpredictable natural calamity that can occur
anywhere in the world. Hence it is must to design all
structures as per earthquake standard. One of the
important observations has been done regarding
multistory building that; core shear wall can be used
as an earthquake resisting element.
Lift core plays vital role as a strengthening
element in structure and it is observed that
architectural planning for many buildings avoiding
this concept of study. Ideal location for lift core will
be important for safety and economy purpose in
structure as the study gives analysis of earthquake
forces by changing the location of lift core with
various cases included. In this report there will be
static and dynamic analysis to be taken in to
consideration. There are many methodologies to spot
the location for lift core and it has to be done on the
basis of static and dynamic analysis which gives
comparison of base shear and time period of
structure.
II. DESIGN
A. Design criteria:
The study will focus all in behaviour of
frames as per soil strata hence according to the lift
locations there will be selected frames of structures
considered. Details of frame behaviour are studied
with the help of the section considered from the
structure.
For more elaborated differentiation there are total six
numbers of cases, as follows (Fig. 1)
1. North edge members for X direction. (X1)
2. South edge members for X direction.( X2)
3. West edge member for Z direction. (Z1)
4. East edge member for Z direction.( Z2)
5. Mid Members for X direction. (MX1)
6. Mid members for Y direction. (MZ1)
Fig. 2.1 Cases for building of lift core at centre
In this study we will compare analysis
results between G+5 and G+10 with Soil strata Soft,
Medium, Hard & R= 3.This will be done for all
following parameters.
RESEARCH ARTICLE OPEN ACCESS

B. Assumptions:
For the purpose of transparency in results
the study considered some important assumptions that
are as follows,
i) Study is limited to Rectangular Shaped building
only i.e. 50X25m.
ii) The depth of foundation for all types of strata is
2m.
iii) Zone V, R=3, I=1, Damping=0.05
iv) Structure is OMRF type.(Ordinary moment
resistant frame)
v) IS code 1893-2002 considered, limit state.
In all cases only single lift core is provided
which is placed either in corner or in centre of the
structures. Hence with the consideration of strata
there will be total number 12 models to be taken in to
consideration for static and dynamic study.
C. Parameters used for study:
1. Maximum considered earthquake (MCE)
2. Zone Factor: (Z) = V
3. Response Reduction: (R) = 3
4. Importance Factor (I) = 1
5. Damping: 0.05
(As per IS 1893-2002 Part I)
6. Design Basis Earthquake (DBE)
7. Design Horizontal Seismic Coefficient (Ah)
8. Richer Scale Magnitude (Mw)
9. Structural response factor (Sa/g)
10. Design seismic base shear (VB)
11. Story drift
12. Response Spectrum
13. Modal Participation Factors(Pk)
14. Fundamental natural period (T)
15. Seismic weight of building (W)
D. Steps of Methodology:
Step 1:
Assume criteria of building and its
information for study. Such as earthquake zone,
damping, importance factor, response reduction
factor etc.
Step 2:
Prepare STAAD model, apply loading and
seismic factor for analysis.
Step 3:
Static analysis and response spectrum
analysis is carried out.
Step 4:
Comparative study is established with help of
graphs for
i) Storey Drifts
ii) Column Forces
iii) Mode Shapes
iv) Mass Participation Factors
v) Base Shear
vi) Column Design & Economics
vii) Response Spectrum
III. STATIC ANALYSIS
E. Story Drift:
Methodology:
In static analysis column forces and story
drift will be analyzed. Earthquake design parameter is
applied as explained earlier. In analysis most
important aspect are given below.
1. Design Horizontal Seismic Coefficient of a structure
(Ah) :
𝑨 𝒉=
𝒁𝑰𝑺 𝒂
𝟐𝑹𝒈
(Abbreviations in II-C)
Values of Sa/g will vary as per soil type and
time period; value of Ah will change according to soil
strata.
2. Total design lateral force or design seismic base
shear (VB):
Along any principle direction is
determined by the following expression:
VB= Ah W
(Abbreviations explained in II-C)
3. The approximate fundamental natural period of
vibration (T): (In Sec)
For buildings of moment-resisting frame and
with brick infill panels is estimated by the empirical
expression:
𝑻 𝒂 =
𝟎. 𝟎𝟗 𝒉
𝒅
Where,
h = Height of the building
d= Base dimension of the building at plinth level in
m.
4. Distribution of design force:
The design base shear computed in further
distributed along the height of the building as per the
following expression:
𝑸 𝒊=𝑽 𝑩
𝑾 𝒊 𝒉 𝒊
𝟐
𝑾 𝒊 𝒉 𝒊
𝟐𝒏
𝒋=𝒊
Where,
Qi = Design lateral force at floor i,
Wi = Seismic weight force at floor i
hi = Height of floor i measured from base
n = number of stories in the building
(As per IS 1893-2002 Part 1)

IV. RESULT ANALYSIS:
Results of story drift are shown in graphical
format and it is observed that all types of structures
giving symmetrical results for deflection. Total
twelve graphs extracted from results from which two
of them are shown above. Graphs prove that drifting
in both G+5 and G+10 type building will be more for
lift core at corner. Here is Graph of G+10 type
building which is showing Story drift of all the six
cases i.e. Corner lift core building for hard, medium,
soft strata and Centre lift core for hard, medium, soft
strata. The graphs shows deflection rate of building
increases at increasing story height, graph shows that
centre lift core for hard strata gives minimum
deflection and corner lift core for soft strata gives
maximum deflection. All graphs of centre lift core are
showing comparatively lesser amount of deflection.
As per IS code 1893-2002 -Part 1(7.11.1) above are
some valid graphs for study. It is observed that the
Storey drift is more in case of building with lift core
at Corner as the Building goes into Torsion Mode.
For the study, total 12 number of model bought under
observation, and it is observed that all models are
giving same results as it is given in above graphs.
Hence building at centre core will have the minimum
deflection with hard strata of the soil.
Fig. 3.1 Story drifts of G+5 Type building Fig. 3.2 Story drifts of G+10 Type building
Results of story drift are shown in graphical
format and it is observed that all types of structures
giving symmetrical results for deflection. Total twelve
graphs extracted from results from which two of them
are shown above. Graphs prove that drifting in both
G+5 and G+10 type building will be more for lift core
at corner. Here is Graph of G+10 type building which
is showing Story drift of all the six cases i.e. Corner
lift core building for hard, medium, soft strata and
Centre lift core for hard, medium, soft strata. The
graphs shows deflection rate of building increases at
increasing story height, graph shows that centre lift
core for hard strata gives minimum deflection and
corner lift core for soft strata gives maximum
deflection. All graphs of centre lift core are showing
comparatively lesser amount of deflection.
As per IS code 1893-2002 -Part 1(7.11.1) above
are some valid graphs for study. It is observed that
the Storey drift is more in case of building with lift
core at Corner as the Building goes into Torsion
Mode. For the study, total 12 number of model
bought under observation, and it is observed that all
models are giving same results as it is given in above
graphs. Hence building at centre core will have the
minimum deflection with hard strata of the soil.
V. DYNAMIC ANALYSIS
F. Responce Spectrum Analysis:
Response spectrum is peak or steady
response of a series of oscillators of varying natural
frequency, which are forced into motion by the same
base shear. The resulting plot can be used to pick the
response of any linear system, given its natural
frequency of oscillation. One such use is in assessing
the peak response of buildings to earthquakes.
In dynamic study this will be the basic parameter
which will come under analysis. As per IS code
response spectrum will be computed. Dynamic
analysis is performed to obtain the design seismic
force, and its distribution to different levels along the
height of the building and to the various lateral load
resisting elements. The basic calculation of response
spectra i.e. Design Horizontal Seismic Coefficient
(Ah) can be calculated by Static Method. For

Dynamic analysis, response spectrum command has
to place with modal analysis command; this will give
the specified demonstration.
Some of the important parameters to be used
in methodology are as follows,
i) Base shear analysis
ii) Time period analysis
iii) Frequency and Mass Participation
1. Modal Mass: Mk
𝑀k =
𝑾𝒊∅𝒊𝒌
𝒏
𝒊=𝟏
𝟐
𝒈 𝑾𝒊
𝒏
𝒊=𝟏 ∅𝒊𝒌
𝟐
Where,
g = Acceleration due to gravity,
Øik = mode Shape coefficient at floor i in mode k
Wi = Seismic weight of floor i
2. Modal Participation Factor: (Pk)
Modal participation factor of mode k of
vibration is the amount by which mode k contributes
to the overall vibration of the structure under
horizontal and vertical earthquake ground motions.
𝑷 𝒌 =
𝑾𝒊
𝒏
𝒊=𝟏 ∅𝒊𝒌
𝑾𝒊 ∅𝒊𝒌
𝟐𝒏
𝒊=𝟏
3. Peak lateral force (Qik):
𝑸𝒊𝒌 = 𝑨 𝒌∅𝒊𝒌 𝑷 𝒌 𝑾𝒊
Where,
Ak = Design horizontal acceleration spectrum values
k = mode
4. Peak shear force: (𝑽𝒊𝒌)
𝑽𝒊𝒌 = 𝑸𝒊𝒌
𝒏
𝒋=𝒊+𝟏
(IS 1893-2002-Part 1)
These are the equations used for Dynamic analysis.
VI. RESULT ANALYSIS:
i) Base shear Result:
Normalizes base shear values are presented
in graphs below.
Fig 5.1 Base Shear of G+5 Medium strata in Z
direction
Fig 5.2 Base Shear of G+5 Medium strata in X
direction

Fig 5.4 Base Shear of G+10 Medium strata in Z
direction
Above are few graphs, shown in linear format
which proves that base shear for building at
centre/mid lift core is lesser than that of corner lift
core. As per proven study it is required to have lesser
Base shear for building to achieve economy in
structures. Here G+5 type and G+10 type building
shows similar results as it shown in Static analysis.
Hence this concludes that in dynamics analysis base
shear will be lesser in centre lift core as compared to
corner lift core building. Here study models are
shown maximum base shear as there are assumption
have be considered to get transparency in results.
1. Time Period: (TP)
i) Time period for G+5 hard strata (Centre and Corner
core):
Fig.5.5 Time period of G+5 at hard strata
Fig.5.6 Time period of G+5 at medium strata
ii) Time period for G+5 Soft soil centre :
Fig.5.7 Time Period of G+10 at Centre Core
(Soft strata)
Fig.5.8 Time Period of G+10 at Corner core (Soft
strata)
From all above results it is computed that time
period for corner core is much lesser than the time
period at centre core building. As the TP for lift core
at corner is more it is clear that the building is in
torsion. Torsion mode invites more destruction of

elements as columns are not designed for turning or
torsion behavior.
2. Modal analysis and Mass Participation:
Mass participation behavior of one of the
structure which shows clearly that the frame which is
extremely near to the lift core is giving less amount of
mass participation than frame which is placed away
from lift core. The other frame considered to be a
corner lift core which gives maximum deflection in
one direction only. The torsion is an additional force
that acts because if the location core at corner hence
mass participation can be optimized if core be placed
at centre. Some of the images of test results from
STAAD Pro showing mode shapes of particular case
are as follows.
i) G+5 Hard strata-Centre lift core:
Fig. 5.9 Modal analysis for G+5 (Centre core)
Frame at Section MX (Front view)
Fig. 5.10 Modal analysis for G+5 (centre core)
Frame at Section MX (Top view)
Fig 5.11 Table for Frequencies and mass
participation for G+5
ii) G+10 Soft strata- Corner lift core:
Fig. 5.12 Modal analysis for G+10 (Corner core)
Frame at Section MX (Front view)
Fig. 5.13 Modal analysis for G+10 Frame at Section
MX (Top view)
Fig. 5.14 Table for Frequencies and mass
participation for G+10(Corner core) Soft strata.
VII. CONCLUSION:
i) It was observed that the Storey drift is more in
building with corner lift core as the Building goes
into Torsion Mode.
ii) The base shear is higher in Corner Core as compared
with the base shear of building with Centre Core.
iii) Time periods of the structure is inversely proportional
with soil stiffness hence it is conclude that the hard
soil strata gives best safety for earthquake resistant
structures
iv) The Buildings with Lift Core at Corner tend to go in
Torsion Mode which develops extra forces in the
frames.
v) Greater Economy can be achieved by keeping the Lift
Cores at Centre of the Buildings.
vi) Building at centre lift core will gives economical
design as well as sufficient amount of safety

REFERENCES
[1]. Dr. Sudhir Jain “Explanatory examples on
Indian Seismic codes IS 1893-2002 (Part I)”-
Indian Institute of technology Kanpur.
[2]. Hialee Rahandale and S.R. Satone in IJERA,
“Design and analysis of multistory building
with effect of shear wall”- May/ June2013
(IJERA)
[3]. Indian Society of structural Engineering
(ISSE) Journal. Manual on basic concept of
earthquake resistant structures.
[4]. J.L. Humur and S. Yavari “Design of concrete
shear wall buildings for Earthquake Induced
torsion” June 2002- at Canadian society of
civil engineering.
[5]. Manoj Baraskar “Collapse Evaluation of Steel
structure” – (2011) Lambert Academic
Publishing, State University of New York,
USA.
[6]. P.D. Pujari “ Performance based seismic
design of reinforced concrete symmetrical
building”- (SEC 2014)
[7]. P.P. Chandurkar, Dr. P.S. Pajgade “Seismic
analysis of RCC building with and without
shear wall” (May/June 2013) Vol I,
International Journal of Modern Engineering
Research (IJMER).
[8]. Ratnesh Kumar “Comparison of seismic
vulnerability of building for higher force VS
higher ductility”-Structural Engineering
convention”-(SEC) 2014.
[9]. Raushan Ranjan,NIT “Seismic analysis of
RCC framed building with plan Irregularity”-
(SEC 2014)

Study of Earthquake Forces By Changing the Location of Lift Core

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