International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 5, Issue 2, February 2016
ISSN 2319 - 4847
Effect of Earthquake on Multistoried Building
Resting on Sloping Ground with and without
bracing
Ms. Tejaswini S. Junghare1, Prof. N. N. Shinde2
1
PG Student, Structural Engineeirng, Pankaj Laddhad Institute of Technology and Management studies, Buldhana
2
Assistant Professor, Department of Civil Engineering, Pankaj Laddhad Institute of Technology and Management studies,
Buldhana
ABSTRACT
As population is going to be increase and due to rapid urbanization of country, India, the buildings are now constructed on
hills known as Step back building. But the behavior of buildings on hills or on slopes is different from the buildings on plain
ground. This causes irregularity in vertical configuration of building and thus more vulnerable during earthquake. Because of
these irregularities as a result of different column height, produces short column effect during seismic action. But to resist
these earthquake forces and to improve the stability of building, lateral force resisting members, bracings can be effectively
used. In this paper, building configuration resting (Step back building) on slope of 100 without bracings and with bracing
having three different height as 10 Storey, 8 Storey and 6 storey is studied. For this, building of symmetrical plan is analyzed by
using structural software STAAD v8i using response spectrum method. Analysis gives the result in terms of parameters as
storey drift, base shear and fundamental time period. And conclude with effective building configuration with bracing
Keywords: ab Step back building, bracings, response spectrum method.
1. INTRODUCTION
Due to the topography, increasing population and rapid urbanization buildings are also constructed on hills. This
causes more failure of structures during earthquake. The reason for such failure is due to the slope of ground which
produces irregularity in vertical configuration. Vertical irregularity forms short column and long column from which
short column attracts more earthquake force and fails earlier compare to long column. In such cases the lateral stability
of building can be increased by providing bracings in such buildings. So that, the displacement of buildings can be
reduced up to certain limit.
The main objective of this study is to improve the performance by reducing the storey drift, of building resting on hills
with the provision of bracing system. Base shear of this configuration are also compared along with their fundamental
time period.
2. METHODOLOGY
This study has been done in following steps which includes all the procedure from literature study up to result and
conclusion on this study:
1. Study the literature related with this work.
2. Parameters related with building models including plan of building has been decided.
3. Slope for these buildings were fixed as 100 on which building of three different storey height as 6 storey, 8 storey and
10 storey has modeled.
4. Response Spectrum Analysis in STAAD v8i has been performed.
5. Results are found in terms of storey drift, base shear and fundamental time period.
3. MODELING AND ANALYSIS
Models of two configurations, Step back building and Step back and Set back Building of three different storey as 6
Storey, 8 Storey and 10 Storey are modeled and analyzed for earthquake parameters using structural software STAAD
v8i using response spectrum method. For this analysis the categorization of models are as given in table 4.1 and figure
4.1 & 4.2:
Volume 5, Issue 2, February 2016
Page 157
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 5, Issue 2, February 2016
ISSN 2319 - 4847
Table 4.1: Model Details
Group
I
II
Model
No.
Model 1
6 Storey
Model 2
8 Storey
Model 3
10
Storey
Model 4
6 Storey
Model 5
8 Storey
Model 6
10
Storey
Storey
Slope
0
10
0
10
Structure
Step back
building
without
bracing
Step back
building
with X
bracing
These models are of same plan of dimension 30 X 30 m. These models are resting on ground of same slope as 100. For
this building column size are assigned as 700 X 700 mm whereas beam size of 230 X 700 mm with 150 mm slab
thickness. The parameters required for response spectrum analysis are as below:
Storey Height:
3m
Depth of Foundation:
1.75 m
Wall Thickness:
a) External :
b) Partition:
230 mm
115 mm
Grade of Concrete:
Slab thickness:
M 25
0.15 m
Superimposed Load:
Zone factor:
Importance Factor:
Response Reduction
Factor (SMRF):
Damping Ratio:
4 KN/m2
0.24
1.5
5
0.05
Figure 4.1: Plan of Building
Volume 5, Issue 2, February 2016
Page 158
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 5, Issue 2, February 2016
ISSN 2319 - 4847
Figure 4.2: Group I Model for Step back building without bracing
Figure 4.3: Group II Model for Step back building with X bracing
4. RESULTS AND DISCUSSION
Above models are analyzed in STAAD v8i by response spectrum method. These models are Step back building without
bracing and Step back building with bracing different storey are presented in tables and graphs for parameters Storey
Drift, Base Shear and Fundamental Time Period.
Volume 5, Issue 2, February 2016
Page 159
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 5, Issue 2, February 2016
ISSN 2319 - 4847
1. Storey Drift:
Table 5.1: Storey Drift for 10 Storey
Storey
Height
0
3
6
9
12
15
18
21
24
27
30
10 Storey
Storey Drift of
Step back
Storey Drift of
building
Step back
without
building with X
bracing (cm)
bracing (cm)
(cm)
0.4511
0.429
0.9592
0.7293
1.1028
0.8069
1.0532
0.7562
0.9548
0.6675
0.8502
0.5726
0.749
0.4877
0.6436
0.4261
0.529
0.3948
0.3898
0.288
0.2485
0.1793
Graphical representation:
Figure 5.1: Storey Drift for 10 Storey
Table No. 6.2: Storey Drift for 8 Storey
8 Storey
Storey Drift of
Storey
Step back
Storey Drift of Step
Height
building without back building with
bracing (cm)
X bracing (cm)
(cm)
0
0.5457
0.4333
3
1.1478
0.7434
6
1.297
0.8148
9
1.2086
0.7493
12
1.0616
0.647
15
0.9037
0.5393
18
0.7331
0.4444
21
0.5383
0.3299
24
0.3343
0.2019
Volume 5, Issue 2, February 2016
Page 160
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 5, Issue 2, February 2016
ISSN 2319 - 4847
Graphical representation:
Figure 5.2: Storey Drift for 8 Storey
Table No. 5.3: Storey Drift for 6 Storey
6 Storey
0
Storey Drift of
Step back
building
without
bracing (cm)
(cm)
0.5111
3
1.0653
0.6425
6
1.1846
0.6891
9
1.0647
0.6108
12
0.8608
0.4878
15
0.6151
0.3537
18
0.3681
0.2098
Storey
Height
Storey Drift of
Step back
building with X
bracing (cm)
0.3795
Graphical representation
Figure 5.3: Storey Drift for 6 Storey
This result gives the improvement in storey drift when step back buildings are provided with X bracing. It shows that
the storey drift for models with x bracing is reduced about 65% in comparison with same models without bracing.
Volume 5, Issue 2, February 2016
Page 161
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 5, Issue 2, February 2016
ISSN 2319 - 4847
2. Base Shear:
Table No. 5.4: Base Shear for 10, 8 and 6 Storey
Step Back
Step Back
Building
Storey Height
Building with X
without
braicng
bracing
10 Storey
9935.11 KN
10007.23 KN
8 Storey
9903.03 KN
9905.64 KN
6Storey
7875.86 KN
7918.37 KN
Graphical representation of Base Shear:
Figure 5.4: Base Shear for 10, 8 and 6 Storey
When step back building is provided with X bracing the base shear for all storey height is increases which increase the
weight of building.
3. Fundamental Time Period:
Table 5.5: Fundamental Time Period
Step Back
Step Back
Storey
Building
Building with X
Height
without bracing
braicng
10 Storey
1.50525 Sec
1.32877 Sec
8 Storey
1.23829 Sec
1.11536 Sec
6Storey
0.97651 Sec
0.88965 Sec
Graphical representation;
Figure No. 5.7: Fundamental Time Period
Volume 5, Issue 2, February 2016
Page 162
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 5, Issue 2, February 2016
ISSN 2319 - 4847
Similarly, fundamental time period in both the cases without and with bracing is not much varying. There is slight
change in variation of fundamental time period.
5. CONCLUSIONS
From all the results seen above which are plotted from the response spectrum analysis of step back building and step
back and set back building it can be concluded that,
1. Storey drift is reduced when Step back building is provided with X bracing.
2. Analyzed Base shear in Step back building compare to building with X bracing is
3. Similarly, Step back building with X bracing has more fundamental time period compare to models without
bracing.
4. Step back building is more susceptible during earthquake due to irregularities and hence when X bracing is
provided in such cases it wil perform better compsir to without bracing.
References
[1] Miss. Chaitrali Arvind Deshpande, Prof. P. M. Mohite, “Effect of Sloping Ground on Step- Back and Setback
Configurations of R.C.C.Frame Building”, International Journal of Engineering Research & Technology (IJERT)
ISSN: 2278-0181 Vol. 3 Issue 10, October- 2014
[2] Sujit Kumar, Dr. Vivek Garg, Dr. Abhay Sharma, “Effect of Sloping Ground on Structural Performance of RCC
Building Under Seismic Load”, Sujit Kumar Et Al. ISSN: 2348-4098 Volume 2 Issue 6 August 2014 (Ver II)
[3] T. Seshadri Sekha, Md. Jaweed Jilani Khan, “Evaluation Of Seismic Response of Symmetric And Asymmetric
Multistoreyed Buildings”, IJRET: International Journal of Research in Engineering and Technology eISSN: 23191163 pISSN: 2321-7308
AUTHOR
1. Ms. Tejaswini S. Junghare, P G Student, Strucutral Engineering, Pankaj Laddhad Institute of Technology and
Management studies, Buldhana.
2. Prof. N. N. Shinde, Assistant Professor, Department of Civil Engineering, Pankaj Laddhad Institute of Technology
and Management studies, Buldhana.
Volume 5, Issue 2, February 2016
Page 163