IRJET- Study on Soft Storey Effect of Plan Regular and Irregular RC Framed Structures under Different Seismic Zones using Response Spectrum Method of Analysis

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 09 | Sep 2019 www.irjet.net p-ISSN: 2395-0072
© 2019, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 339
Study on Soft Storey Effect of Plan Regular and Irregular RC Framed
Structures under Different Seismic Zones using Response Spectrum
Method of Analysis
Aradhya B M S1, Dr. B Shivakumara Swamy2
1 Student M.Tech, Department of civil Engineering, Dr AIT, Bengaluru, Karnataka, India
2Professor, Department of Civil Engineering, Dr AIT, Bengaluru, Karnataka, India
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Abstract -In urban India and modern world multi storey
constructions openfirst storeyisatypical commonfeature Due
totheadvantageofopenspacefor the purpose of parking and
for commercial use. And also plan irregularity structures has
become common nowadays in urban areas for different
reasons like non availability of required site dimensions,
aesthetic view etc., Under high seismic regions the buildings
built with open storey as well as irregular plan buildings are
undesirable. This project aims for the study of performanceofa
Reinforced concrete frame building (G+13) with soft storey
and with bare frame and also with masonry wall infill. Linear
dynamic analysis (response spectrum analysis) is done using
the software SAP2000 as per IS 1893-2002 ( part 1 ) and the
results obtained from the structure like storey displacement,
Storey drift, Base shear and time period were compared with
the plan regular and irregular structures (re-entrant corner
type of irregularity) under medium soil forseismic zones II &
V.
Key Words: Soft storey, Response spectrum analysis,
SAP2000, Plan irregularity, Masonry wall infill.
1. INTRODUCTION
Due to past earthquake disasters we seen that many
structures collapsed which were not designed as earthquake
resistant structures and hadhugedestructionandalsolossof
life, so now this issue has become biggest challenge for civil
and structural Engineers to make sure structures are safe
during earthquake. In modern world plan irregularity
structures has becomecommon nowadays inurbanareasfor
different reasons like non availability of required site
dimensions, aesthetic view etc., irregularities as per IS code
1893-2002are stiffness,diaphragm, out ofoffsets, no-parallel
offsets, re-entrant corner, and torsion irregularity. Most
buildings are outlined by irregular in each plan and vertical
configuration.
Masonry infill generally includes of bricks or concrete
blocks built between beams and columns of a reinforced
concrete frame. The presence of masonry infill walls has an
important impact on the seismic zone response of a
reinforced concrete frame building, increasing structural
strength a stiffness. The structural influence of infill wall
results into stiffer structure thus decreasing the storey
drifts. This improved overall performance makes the
structural design greater practical to consider infill wallsas
a structural element in the earthquake resistant design of
structures.
1.1 Objectives
The objectives of this study are listed below.
 To analyze the effect of soft storey in RC framed
structure.
 To study the behavior of the RC framed structure
with soft storey and without soft storey.
 To compare behaviour of RC framed plan regular
and irregular structures under all seismic zones
using response spectrum method.
 To find the important parameters like Base shear,
displacement, storey drifts and time period.
1.2 Methodology
Following method is adopted for the analysis,
1. Extensive literature review is carriedout
2. Using the software SAP2000 analysis of the
buildings with plan regular and irregularity is
done, and also considered with and without soft
storey as well as masonry infill.
3. VariousparameterslikeDisplacement,Storeydrift,
and Base shear and time period were obtained.
Based on the results obtained conclusions are derived.
2. MODEL DETAILS
The study is carried out for the behaviour of G+13 storied
R.C frame buildings with and without soft storeys as well as
with and without masonry wall infill for plan regular andre-
entrant type of irregularity. Floor height providing is 3.5m
and plinth height as 1.8m and properties are defined for
frame structures.12modelsareshapedinSAP2000software
for dynamic analysis.

Table -1: Description of models
MODEL
NUMBE
R
EART
HQUA
KE
ZONE
PLAN TYPE STOREY
DESCRIPTION
Model 1 ZONE
II
Plan Regular Masonry wall in
filled frame
Model 2 ZONE
II
Plan Regular Bare Frame(without
masonry wall infill)
Model 3 ZONE
II
Plan Regular Soft Storey At
Ground Floor frame
Model 4 ZONE
II
Plan Irregular Masonry wall in
filled frame
Model 5 ZONE
II
Plan Irregular Bare Frame(without
Model 6 ZONE
II
Plan Irregular Soft Storey At
Ground Floor frame
Model 7 ZONE
V
Plan Regular Masonry wall in
filled frame
Model 8 ZONE
V
Plan Regular Bare Frame(without
Model 9 ZONE
V
Plan Regular Soft Storey At
Ground Floor frame
Model 10 ZONE
V
Plan Irregular Masonry wall in
filled frame
Model 11 ZONE
V
Plan Irregular Bare Frame(without
Model 12 ZONE
V
Plan Irregular Soft Storey At
Ground Floor frame
2.1 Model dimensions
Building dimension X=30m, Y=30m,
Height of the building Z=53m (Including head room)
Number of stories = G+13
Each Storey height = 3.5m, 2m (Head Room)
Column spacing along X direction = 5 m
Column spacing along Y direction = 10 m
2.2 Material properties
Concrete Grades = M25, M30, M35 (As per IS standards)
Steel Grade = Fe500
2.3 Member properties
Slab thickness = 200mm
Wall thickness (outer) = 230mm (Masonry)
Parapet and partition walls = 115mm (Masonry)
Beam size = 230X350mm (M25), 250X850mm (M25)
Column size
= 350X350mm (M30), 500X1000mm (M30), [up to 26.5m]
= 300X300mm (M30), 350X700mm (M30), [26.5m to 53m]
Height of parapet wall =1.0m
2.4 General loading
Wall (230mm) load on beam = 12kN/m
Wall (115mm) load on beam = 6kN/m
Floor finish = 1kN/m2
Water tank load (circular 1.1m dia) = 12 kN/m2
Lift load considered on slab = 12 kN/m2
Live load (IS 875-1987 part 2) = 4kN/m2 (floor)
Live load (IS 875-1987 part 2) = 1.5kN/m2 (roof)
For seismic Zone II
 Importance factor = 1.0
 Response reduction factor =5
 Site type = Medium (II)
 Zone Factor =0.10
For seismic Zone V
 Importance factor =1.0
 Response reduction factor= 5
 Site type = Medium (II)
 Zone Factor =0.36
2.5 Planning and modelling
Before modelling, architectural plan of all the models are
prepared using AutoCADD software.
Fig -1: Regular plan ground floor

Fig -2: Regular plan 1 to 13 floors
Fig -3: Irregular plan for ground floor
[Re-entrant corner type irregular building having
projections 50% along X direction and 33.33% along Y
direction]
Fig -4: Irregular plan for 1 to 13 floors
[Re-entrant corner type irregular building having
projections 50% along X direction and 33.33% along Y
direction]
Fig -5: Plan regular frame Fig -6: Plan regular
with masonry wall in fill bare frame
Fig -7: Plan regular frame Fig -8: Plan irregular frame
with Soft storey at GF masonry wall in fill
Fig -9: Plan irregular Fig -10: Plan irregular frame
Bare frame with soft storey at GF
3. ANALYSIS
Response spectrum analysis is done for the buildings by
considering they are located in seismic zone II & V using
SAP2000 software.

4 RESULTS AND DISCUSSIONS
The various parameters like Displacement, Storey drift,
Base shear and Time period are obtained by carrying
response spectrum analysis for the different models
considered in this study.
4.1 Displacement:
Fig -11: Displacement along X direction at zone II
Fig-11 Shows the plots of displacement of structure
along the height in X direction for model 1 to model 6,
obtained by dynamic analysis for zone II. Model 2 has higher
displacement compare to other models. The highest
displacement of the building found to be 17.32mm in Model
2 (Regular plan with bare frame)
Fig -12: Displacement along X direction at zone V
Fig-12 Shows the plots of displacement of building
along height in X direction for model 7 to model 12,obtained
by dynamic analysis for zone V. Model 8 has highest
displacement compare to other models. The maximum
8 (Regular plan with bare frame)
Fig -13: Displacement along Y direction at zone II
Fig-13 Shows the plots of displacement of building
along height in Y direction for model 1 to model 6, obtained
by dynamic analysis for zone II. Model 5 has highest
displacement compare to other models. The maximum
5 (Irregular plan with bare frame)
Fig -14: Displacement along Y direction at zone V

Fig-14 Shows the plotsofdisplacementof buildingalong
height in Y direction for model 7 to model 12, obtained by
dynamic analysis for zone V. Model 11 has greater
displacement compare to other models. The highest
11 (Irregular plan with bare frame)
4.2 Storey Drift:
Fig -15: Storey drift along X direction at zone II
Fig-15 Shows the plot of storey numberv/sstoreydrift
for model 1 to model 6, and observed that the storey drift is
highest in the storeys where the soft storey is located. The
highest value of storey drift in the X direction 0.0056m is
occurred in the model3 (Regular plan frame with soft storey
at GF) located in seismic zone II.
Fig -16: Storey drift along X direction at zone V
Fig-16 shows the plot of storey numberv/sstoreydrift
graph for model 7 to model 12, it is observed that storey
drift is highest in the storeys where the soft storey is
situated. The highest value of storey drift in the X direction
0.0203m is occurred in the model9 (Regularplanframewith
soft storey at GF) located in seismic zone V.
Fig -17: Storey drift along Y direction at zone II
Fig-17 Shows the plot of storey number v/s storeydrift
graph for model 1 to model 6, it is observed that the storey
drift is maximum in the storeys where the there is no
masonry wall infill is present. The maximum value of storey
drift in the Y direction 0.0059m is occurred in the model 5
(Irregular plan with Bare frame) located in seismic zone II.
Fig -18: Storey drift along Y direction at zone V

Fig-18 shows the plot of storey numberv/sstoreydrift
graph for model 1 to model 6, it is observed that the storey
drift is maximum in the storeys where the there is no
masonry wall infill is present. The maximum value of storey
drift in the Y direction 0.0275m is occurred in the model 11
(Irregular plan with Bare frame) located in seismic zone V
4.3 Base shear:
Fig -19: Maximum base shear along X direction at zone II
Fig-19 Shows the plot between maximum base shear
v/s various models considered in the analysis. It is observed
that the highest base shear value 4267.05 kN is occurred in
the model 1 (Regular plan frame in filled withmasonrywall)
along the X direction located in seismic zone II. It is also
observed that, masonry in fill influences the base shear of
the building and model 1 which is in filledwithmasonrywall
has higher base shear compared to other models.
Fig -20: Maximum base shear along X direction at zone V
Fig-20 Shows the plot between maximum base shear
v/s various models considered in the analysis. In this
observed that the highest base shear value 15094.74 kN is
occurred in the model 7 (Regular plan frame in filled with
masonry wall) along the X direction located in seismic zone
V. And also observed that, models with bare frame has very
less base shear compare to other models
Fig -21: Maximum base shear along Y direction at zone II
Fig-21 Showstheplotbetweenmaximumbaseshear
v/s various models considered in the analysis. It is observed
that the maximum base shear value 4266.95 kN is occurred
in the model 1 (Regular plan frame in filled with masonry
wall) along the Y direction located in seismic zone II. It is
also observed that, masonry in fill influences the base shear
of the building and model 1 which is in filled with masonry
wall has higher base shear compared to other models.
Fig -22: Maximum base shear along Y direction at zone V
Fig-22 Shows the plot between highest base shear v/s
various models considered in the analysis. In this observed
that the maximum base shear value 15093.72kN isoccurred
in the model 7 (Regular plan frame in filled with masonry
wall) along the Y direction located in seismic zone V. And
also observed that, models with bare frame has very less
base shear compare to other models.
4.4 Time period:
Fig -23: Maximum Time period at zone II
Fig-23 Shows the plot between time period v/s
various models considered in the analysis. In this observed
that the maximum time period value 3.52 seconds is
occurred in the model 2 (Regular plan with Bare frame)
located in seismic zone II. And also observed that models
with bare frame has very high time period compare to other
models.

Fig -24: Maximum Time period at zone V
Fig-24 Shows the plot betweentimeperiodv/svarious
models considered in the analysis. In this observed that the
highest time period value 3.53 seconds is occurred in the
model 8 (Regular plan with Bare frame) located in seismic
zone V. It is also observed that models with masonry wall
infill has very less time period compare to other models
5. CONCLUSIONS
From this study following conclusions are drawn:
 Models having bare frame shows the maximum value of
displacement in Both X and Y direction and under both
Earthquake zones II and V compare to all other models
because of less lateral stiffness of the storey.
 The displacement value is considerably reduced in the
models with masonry wall infill in both X and Y
direction under seismic forcesatbothEarthquakezones
II and V. from this we can conclude that we should
prefer masonry wall infill instead of bare frame
structures under higher seismic zones.
 Models with soft storey shows higher value of storey
drift than models without soft storey, therefore we
should avoid soft storey in the buildings under higher
seismic zones or we should increase the lateral stiffness
of the storey by providing shear wall, bracings etc.
 The existence of masonry infill impacts the overall
behaviour of structures when exposed to earthquake
forces. Lateral displacements and storey drifts are
noticeably reduced when the involvement of the infill
brick wall is taken into account
 Models with bare frame shows very less base shear
compare to models with masonry wall infill therefore
we conclude masonry wall influences the base shear of
the building.
 Models with bare frame shows high time period
compare to other models, which indicates bare frame
buildings are more flexible under seismic forces.
 Models with masonry wall infill has very less time
period compare to other models which shows masonry
infill makes building more stiffer and less flexible under
seismic forces.
 Re-entrant type of plan irregularity buildings having
projections less than 50 % are acceptable under both
seismic zones II and V with masonry infill and not
acceptable with bare frame .
 When Column dimensions to be changed along the
height of the building in bare frame buildings
(considering economy point as well as requirements),
sudden change of column dimensions with large
difference should not be done which mayleadtosudden
storey drift.
 Steel framed structure can be used to Study on soft
storey effect of plan regular and irregular structures
under different Seismiczonesusingresponsespectrum
method of analysis can be done.
 Buildings can be analyzed in different soil types and
seismic zones III and IV also.
 Other forms of irregularities as per IS 1893 (part1):
2002 such as Torsion irregularity, diaphragm
discontinuity,out-of-planeoffsets,non-parallel systems
can be taken for further study
REFERENCES
[1] Singh Shailendra andVasaikarHemantBabulal,“Seismic
Response of Soft Storey on High Rise Building Frame”,
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[2] K. Vamshi Satyanarayana and Vinod Kumar, “Seismic
Response of RC Frame Building with Soft Storey at
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42 Number-4 - December 2016.
[3] S.Arunkumar and Dr. G. Nadini Devi, “seismic demand
study of soft storey building and it’s strengthening for
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[4] Pavithra R and Vasaikar Hemant Babulal, “Study of
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non-linear dynamic analysis of multi storied R.C frame
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ETABS”, www.irjet.net, p-ISSN: 2395-0072, Volume: 05
Issue: 07 | July 2018.
[6] Ganesh Kumbhar and Anirudhha Banhatti, “Seismic
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6. FUTURE SCOPE

[7] Vihar S Desai, Hitesh K Dhameliya, Yati R Tank,
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at different level along with ground level”,
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2017.
[8] Pritam C. Pawade, Dr P.P Saklecha and Milind R Nikhar,
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zones and various type of soil”, IARJSET, ISSN (Print)
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[11] IS: 1893 (Part 1):2002 Criteria for earthquake resistant
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And more.
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Issue 4, April 2017.

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