IRJET- Seismic Behaviour of Buildings Resting on Sloping Ground

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 08 Issue: 04 | Apr 2021 www.irjet.net p-ISSN: 2395-0072
© 2021, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 18
Seismic Behaviour of Buildings Resting on Sloping Ground
Prashanth A S1, Thejaswini RM2, L Govindaraju3
1P.G Student, Department of Civil Engineering, U.V.C.E, Bangalore University, Bengaluru.
2Research scholar, Department of Civil Engineering, U.V.C.E, Bangalore University, Bengaluru.
3Professor, Department of Civil Engineering, U.V.C.E, Bangalore University, Bengaluru.
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Abstract - In hilly regions engineered construction is
constrained by localtopographyresulting inadoptionofeither
step back or step back - set back building configuration with
varying column heights, this condition leads to torsion and
increased shear during seismic ground motion. The buildings
situated on sloping grounds have mass and stiffness varying
along vertical and horizontal planes. Centre of mass and
center of rigidity do not coincide on various floors.
In this study an attempt have been made to study the effects
five storey and ten storey step back and step back - set back
buildings. The results in terms of storey displacement, base
shear, storey drift, time period and modal frequencies are
obtained.
Key Words: Sloping ground, storey displacement, storey
drift, step back and step back - set back building
1. INTRODUCTION
Any sudden shaking of the ground caused by the passage of
seismic waves through earth’s rocks is termed as an
Earthquake. In some parts of the world it is noticedthathilly
areas are more prone to seismic activities. A scarcityofplain
ground in hilly area compels the construction activity on
sloping ground. The behaviour of buildings resting on the
slopes are asymmetric which imparts irregularity in both
horizontal and vertical plane. The distribution of mass and
stiffness in horizontal and vertical planes plays a significant
role in the seismic behaviour of building during an
earthquake. These buildings have significant torsional
response when they are subjected to lateral forces and also
at the setback location there is an increase in stress
concentration during an earthquake. Due to the unequal
column height within the storeyleadstothedrasticvariation
in the stiffness in the storey.
2. SCOPE AND OBJECTIVES
1. Step back and step back-set back buildings of 5 storey
and 10 storey are studied.
2. Modal analysis has been carried out to obtain resonant
frequency or fundamental frequency of considered
buildings using finite element software SAP.2000.
3. Storey displacements and storey drifts are to be
obtained using Time history analysis using BHUJ
Earthquake Data.
4. A sloping angle of 27˚ with respect to horizontal has
been considered to observe the seismic performance of
the step back and step back-set back buildings.
5. The effect of bays in step back and step back-set back
buildings are studied by varying number of bays in Y
direction. (3-Bays).
3. DESIGN SPECIFICATION OF BUILDING
A medium rise and high-rise step back and step back–set
back buildings resting on sloping ground of angle of 270 has
been modelled and analysed using FEM based software SAP
2000. The model consists of five storey and ten storey witha
storey height of 3 m having 3 bays along longitudinal
direction and 1 bay with a spacing 4 m along transverse
direction and increased accordingly with a spacing of 4 m.
TABLE 1 and Table 2 represents 5-storey and 10 storey
building nomenclature.
TABLE 1: 5-storey building nomenclature
Where, SB represents Step back building and SSB
represents Step back – set back building.

TABLE 2: 10-storey building nomenclature
Where, TSB represents Ten storey step back building
and TSSB represents Ten storey step back - set back
building.
In total twelve buildings out of which six buildings are
analysed by considering step back type and the remaining
six are analysed as step back - set back type buildings as
shown in Table 1 and 2. All these buildings are investigated
for their dynamicresponseconsidering270 slopinggrounds.
Both dead load and live loads are considered as per IS 875
part II and the details are shown in Tables4and5.Structural
elements have been designed as per IS 456-2000 and IS
1893:2016 by considering M 25 grade concrete and Fe 415
grade steel. The dynamic parameters considered for the
analysis is given in Table 5. Table 6 indicates the designed
dimensions of the building components.
Table-3: Details of load for 5- storey buildings
STOREY
DEAD LOAD
(kN/m2)
LIVE LOAD
(kN/m2)
1,2,3,4 1 kN/m2 3 kN/m2
Roof 2 kN/m2 1.5 kN/m2
Table-4: Details of load for 10- storey buildings
STOREY
DEAD LOAD
(kN/m2)
LIVE LOAD
(kN/m2)
1-9 1 kN/m2 3 kN/m2
Roof 2 kN/m2 1.5 kN/m2
TABLE 5: Details of dynamic parameters
Sl.No. Contents Description
1 Seismic Zone V
2 Soil Type TYPE-I
3 Importance Factor 1
4
Response Reduction
Factor
5
Table -6: Details of Dimensions of Building Components
Structural
element
5-STOREY (in
mm)
10-STOREY (in
mm)
COLUMN 250×600 mm 400×600 mm
BEAM 300×400 mm 300×400 mm
SLAB 150 mm thick 150 mm thick
3. RESULTS AND DISCUSSION
Table 7 and 8 shows displacements for step back buildings,
base shear is represented in Table 9. Table 10 and 11 Shows
displacements for Step back - Set back buildings. Base shear
is represented in Table 12 for both the directions of the
buildings.
Storey drift at each storey of all considered buildings are
graphically presented in Fig.3 and 4 for Step back buildings
and Fig.8 and 9 for Step back-set back buildings
respectively.
Table 13 and 14 shows displacements of ten Storey Step
back buildings, Base shear is represented in table 15. Table
16 and 17 Shows displacements of ten storey Step back - set
back Buildings. Base shearofthebuildingsin bothdirections
are represented in Table 18.
Fig.13 and 14 represents the storey drift at each storey for
Ten Storey step back buildings.Fig.18and19representsthe
storey drift at each storey for for Ten Storey step back - set
back buildings respectively.
TABLE 7: Storey Displacement(mm) of Step-Back
Buildings along X-Direction
Number
of storey
SB-1 SB-2 SB-3
5 25.329 30.157 26.162
4 21.044 24.488 21.076
3 13.22 14.840 12.520
2 5.526 5.947 4.891
1 0.883 0.913 0.723

Fig -1: Storey displacement(mm) of buildings along
X-Direction
Table 8: Storey Displacement(mm) of Step-Back Buildings
along Y-Direction
Number
of storey
SB-1 SB-2 SB-3
5 10.349 10.891 10.424
4 8.769 9.611 9.193
3 6.462 7.341 6.934
2 3.729 4.192 3.81
1 1.032 0.962 0.767
Fig 2: Storey displacement(mm) of buildings along Y-
Direction
Fig -3: Storey drift of buildings along X-Direction
Fig -4: Store Drift of buildings along Y-Direction
TABLE 9: Base shear(kN) of Step-Back buildings
SB-1 SB-2 SB-3
THX =360.10 kN THX =637.24 kN THX =803.255 kN
THY = 254.53 kN THY = 489.38 kN THY = 697.03 kN
Fig 5: Base shear (THX, THY) in SB1, SB2 and SB3
Buildings
TABLE 10: Storey Displacement(mm) of Step-Back Set-
Back Buildings along X-Direction.
Number
of storey
SSB-1 SSB-2 SSB-3
5 10.228 10.477 12.197
4 8.274 8.179 9.556
3 5.430 5.890 6.884
2 2.834 3.360 3.841
1 0.655 0.7458 0.745

Fig -6: Storey displacement(mm) for SSB1, SSB2 and SSB3
buildings
TABLE 11: Storey Displacement of Step Back - Set-Back
Buildings along Y-Direction
Number
of storey
SSB-1 SSB-2 SSB-3
5 11.639 11.425 10.967
4 10.975 10.414 10.172
3 9.303 8.460 8.230
2 5.251 4.568 4.300
1 1.402 0.986 0.814
Fig -7: Storey displacement(mm) of SSB1, SSB2 and SSB3
buildings
Fig 8: Storey drift of SSB1, SSB2 and SSB3 buildings
Fig 9: Storey drift for SSB1, SSB2 and SSB3 buildings
TABLE 12: Base shear of SSB-1, SSB-2, SSB-3
BASE SHEAR
SSB-1 SSB-2 SSB-3
Fig 10: Base shear for SSB1, SSB2 and SSB3 buildings
TABLE 13: Storey Displacement(mm) of Ten Storey Step-
Back Buildings along X-Direction
Number of
storey
TSB-1 TSB-2 TSB-3
10 66.103 68.033 67.183
9 63.484 64.670 63.689
8 59.044 59.228 58.172
7 52.643 51.910 50.985
6 44.426 43.238 42.605
5 34.732 33.682 33.440
4 24.034 23.577 23.729
3 12.997 13.41 13.869
2 4.811 5.495 5.816
1 0.788 0.904 0.8995

Fig -11: Storey displacement(mm) of TSB1, TSB2 and
TSB3 buildings
TABLE 14: Storey Displacement(mm) of Ten Storey
Step-Back Buildings along Y-Direction
Number
of storey
TSB-1
Storey
TSB-2
Storey
TSB-3
Storey
10 71.556 70.654 68.516
9 66.892 67.125 65.597
8 60.847 62.039 61.062
7 53.413 55.265 54.697
6 44.807 46.905 46.585
5 35.340 37.267 36.991
4 25.437 26.797 26.359
3 15.795 16.327 15.619
2 7.328 7.113 6.408
1 1.500 1.202 0.970
Fig -12: Storey displacement(mm) of TSB1, TSB2 and
TSB3 buildings
Fig -13: Storey drift of TSB1, TSB2 and TSB3 -Time
History (THX)
Fig -14: Storey drift of TSB1, TSB2 and TSB3 -Time
History (THY)
Table 15: Base shear of Ten Storey Step-Back buildings
BASE SHEAR
TSB-1 TSB-2 TSB-3
Fig 15: Base shear of TSB1, TSB2 and TSB3 buildings

Table 16: Storey Displacement(mm) of Ten Storey Step-
Back Set-Back Buildings along X-Direction
Number
of storey
TSSB-1
Storey
TSSB-2
Storey
TSSB-3
Storey
10 56.263 60.699 65.833
9 53.296 58.077 63.177
8 49.281 54.324 59.319
7 44.086 49.148 53.832
6 37.355 42.048 46.154
5 29.404 33.325 36.522
4 20.912 23.401 25.496
3 11.342 13.0161 14.020
2 4.280 5.070 5.241
1 0.751 0.785 0.682
Fig -16: Storey displacement(mm) of TSSB1, TSSB2 and
TSSB3 buildings
Table 17: Storey Displacement(mm) of Ten Storey Step-
Back Buildings along Y-Direction
Number
of
storey
TSSB-1
Storey
TSSB-2
Storey
TSSB-3
Storey
10 60.941 54.473 52.024
9 60.091 53.120 50.678
8 58.271 50.981 48.287
7 52.327 46.221 43.586
6 44.786 39.892 37.358
5 35.817 32.095 30.728
4 25.931 23.245 22.590
3 16.053 14.140 13.548
2 7.358 6.091 5.488
1 1.488 1.014 0.805
Fig -17: Storey displacement(mm) of TSSB1, TSSB2 and
TSSB3 buildings
Fig -18: Storey drift of TSSB1, TSSB2 and TSSB3 -Time
History (THX)
Fig -19: Storey drift of TSSB1, TSSB2 and TSSB3 -Time
History (THY)
Table 18: - Base shear of (TSSB-1, TSSB-2, TSSB-3)
buildings
BASE SHEAR
TSSB-1 TSSB-2 TSSB-3

Fig 21: Base shear (THX, THY) of TSSB1, TSSB2 and TSSB3
Buildings
4. CONCLUSIONS
1. From the modal analysis high-rise buildings, it is found
that as the bay increases the fundamental frequency of
the considered buildings decreases.
2. It is also observed that the fundamental frequency of
step back building is lower compared to step back set
back building.
3. It is observed that for high-rise buildings storey
displacement increases in X-direction and decreases in
Y-direction for time history analysis.
4. The storey displacement is moreforwith3-baysforstep
back set back building compared with the two bay and
one bay along transverse direction.
5. Step back buildings have more storey displacement
compared to step back set back building configuration
6. The storey drift is observed to be more for step back
building configuration compared to the step back set
back building for time history analysis.
7. It is also observed that the base shear is more for step
back building compared with stepback setback building
for time history analysis for 5-storey and 10-storey
buildings.
8. Base shear is observed to be more for step back setback
building compared to step back building configuration
for high-rise building.
REFERENCES
[1] S.A. Halkude, M. G Kalyanshetti and V.D. Ingle, “Seismic
analysis of buildings resting on sloping ground with
varying number of bays and hill slopes”, International
Journal of Engineering Research
&Technology,Vol.2,pp.3632-3640,2013.
[2] S. Varadharajana, V. K. Sehgal and B. Saini (2014),
“Fundamental time period of RC Setback Buildings”,
Concrete research letters, Vol. 5(4), December 2014.
[3] Birajdar.B.G and S. S. Nalawade (2004)“Seismic analysis
of buildings resting on sloping ground”, 13thWorld
Conference on EarthquakeEngineering,Vancouver,B.C.,
Canada, Paper No. 1472, 2004.
[4] Rahul Ghosh andRama Debbarma (2017),“Performance
evaluation of setback buildingswithopengroundstorey
on plain and sloping ground under earthquake loadings
and mitigation of failure”, This article is published with
open access at Springerlink.com Int, J Adv Struct Eng
(2017) 9:97–110, 14 February 2017 The Author(s)
2017.
[5] Ravikumar C M and Babu Narayan K S (2012), “Effect of
Irregular Configurations on Seismic Vulnerability of RC
Buildings”, Architecture Research 2012.
[6] S. A. Halkude (2013), “Seismic Analysis of Buildings
Resting on Sloping GroundwithVaryingNumberofBays
and Hill Slopes”, International Journal of Engineering
Research and Technology ISSN:2278-0181, Vol.2, Issue
12, December-2013.
BIOGRAPHIES
Prashanth A S,
P.G Student, Department of Civil
Engineering, U.V.C.E, Bangalore
University,Jnana BharathiCampus,
Bengaluru.
Thejaswini R. M.
Assistant professor in Govt.
S.K.S.J.T. Institute.
Research scholar, Department of
Civil Engineering, U.V.C.E,
Bangalore University, Bengaluru
L. Govindaraju,
Professor, Department of Civil
Engineering, U.V.C.E, Bangalore
University,Jnana BharathiCampus,
Bengaluru.

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