DOI : 10.17577/IJERTV5IS070439
- Open Access
- Total Downloads : 324
- Authors : Md Abdul Bari, Prof. Shaik Abdulla
- Paper ID : IJERTV5IS070439
- Volume & Issue : Volume 05, Issue 07 (July 2016)
- DOI : http://dx.doi.org/10.17577/IJERTV5IS070439
- Published (First Online): 25-07-2016
- ISSN (Online) : 2278-0181
- Publisher Name : IJERT
- License:
This work is licensed under a Creative Commons Attribution 4.0 International License
Linear and Non Linear (Pushover) Analysis of An Irregular Shape Multistorey Building with Different Shear Wall Position
Md. Abdul Bari1,
1 P.G. Student, Department of Civil Engineering,
Khaja Banda Nawaz College of Engineering, Gulbarga, Karnataka State, India.
Prof. Shaik Abdulla2
2 Assistant Professor, Department of Civil Engineering,
Khaja Banda Nawaz College of Engineering, Gulbarga, Karnataka State, India.
Abstract: Nowadays, many of the buildings are traced by irregular in both plan and vertical configurations. Due to these irregularities in arrangement and deficient in symmetry might imply vital eccentricity between the stiffness centre and building mass, and give rise to damage in the form of coupled lateral response. One of the most commonly used lateral load resisting system is the shear wall system. Shear walls may be defined as the vertical planar elements, made up of RCC material and efficient in resisting lateral loads produced due to seismic actions. The irregularity of the building may be horizontally or vertically. In the present study an irregular shape multistory building is analyzed using shear walls at different positions to know the seismic behavior through seismic parameters like Time period, Base Shear, Storey Drift, Storey Displacements, Column Moments and Beam Moments. The analysis is carried out on different models using Equivalent Static Force Method (linear), Response Spectrum Method (linear), and Pushover Analysis Method (non linear) using ETABS application software.
Keywords Base Shear, Equivalent Static Force Method Pushover, Pushover Analysis Method, Response Spectrum Method, Shear Wall, Seismic Parameters, Storey Drift, Time Period.
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INTRODUCTION
One of the most commonly used lateral load resisting system is the shear wall system. Shear walls may be defined as the vertical planar elements, made up of RCC material and efficient in resisting lateral loads produced due to seismic actions. The irregularity of the building may be horizontally or vertically. Shear walls helps in reducing the dimensions of the beams and columns, which in turn helps in reducing the cost of the buildings. In the present study the shear wall is used as a barrier for resisting the lateral forces and also to reduce the lateral stiffness and lateral deflections when seismic actions come into picture.
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LITERATURE REVIEW
Dr. S. A. Halkude, Mr. C. G. Konapure, Ms. C. A. Madgundi conducted investigation on Effect of Seismicity on Irregular Shape Structure. In their G+11 Building by varying the percentage length of shear wall along with possible combinations of shear wall location, they concluded that the seismic effects were resisted effectively
by providing the closed box type shear walls [1]. Dr. H.S. Chore, P.A.Dode, N.L.Sawakare studied the Effect of Shear Wall on Response of Multi-storied Building Frame. In their study on G+12 rcc building by considering two types of structural systems, they concluded that the large dimension of shear wall helps in taking the major amount of horizontal forces [2]. S.A. Halkude, C.G. Konapure and S.M.Birajdar carried reaserch work on Effect of Location of Shear Walls on Seismic Performance of Buildings. In their work on a G+9 storey building (2 cases) consisting of 10% and 20% shear wall length in each case respectively they concluded that as the shear wall length increases the stiffness of the structure also increases [3]. Kashiwa Sagar K., Prof. M.R.Wakchaure, Anantwad Shirish studied the Effects of Numbers and Positions of Shear Walls on Seismic Behavior of Multistory Structure. They concluded that the stiffness of the building increases by adding shear wall to the structure thus reducing damage [4]. Aung Mon, Tin Tin Htwe did research work of Study on Performance of Discrete Staggered Shear Walls in 25-Storeyed RC Building. In their G+24 building having irregular vertical rectangular shape they concluded that the use of diagonal shear wall structure is more suitable than zigzag shear wall structure [5].
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BUILDING DESCRIPTION
The plan of the RC SMRF building is as shown in the Fig 1 . The plans of the various models are as shown in the Fig 2 below. In this study the plan configuration is same for all the models. Each model is of 15 storeys with a depth of the foundation equal to 2m. Each storey height is kept equal to 3.2m for all the various building models. An irregular shape in plan configuration building in zone IV is considered for the study. Floor live load is taken exactly half (50%) for the calculation of the seismic weight. The design data applied for all the different building models is given below in Table 3.1.
Table 3.1 Salient Features of the Building
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MODELLING AND ANALYSIS
Sl.No.
Specifications
Details
1.
Type Of Structure
SMRF
2.
Zone
IV
3.
Layout
as Shown in the fig.1
4.
Number of Stories
(G+15)
5.
Ground Storey Height
3.2m
6.
Floor-To-Floor Height
3.2m
7.
Wall Thickness
0.23m
8.
Live Load
3.0 KN/m2
9.
Materials
M25 and Fe500
10.
Seismic Analysis
ESA, RSA And
Pushover
11.
Design Philosophy
Limit State Method Conforming
To IS 456 : 2000
12.
Size of Column
(0.35×0.90) m
13.
Size of Beams in Longitudinal and
Transverse Direction
(0.23×0.60) m
14.
Total Thickness of Slab
0.150 m
Sl.No.
Specifications
Details
1.
Type Of Structure
SMRF
2.
Zone
IV
3.
Layout
as Shown in the fig.1
4.
Number of Stories
(G+15)
5.
Ground Storey Height
3.2m
6.
Floor-To-Floor Height
3.2m
7.
Wall Thickness
0.23m
8.
Live Load
3.0 KN/m2
9.
Materials
M25 and Fe500
10.
Seismic Analysis
ESA, RSA And
Pushover
11.
Design Philosophy
Limit State Method Conforming
To IS 456 : 2000
12.
Size of Column
(0.35×0.90) m
13.
Size of Beams in Longitudinal and
Transverse Direction
(0.23×0.60) m
14.
Total Thickness of Slab
0.150 m
In the present study about 13 models where considered with following models such as bare frame, full infill, shear wall at different positionswith infill. The analysis is done using ETABS. The plan layout for all the models is same as shown in the Fig 1 below. Model 3 to Model 13 are same as Model 2 but only the infill is replaced by Shear Wall at required positions. The shear wall run throughout the height of the building and has constant 5m length in every model.
Fig 1. Plan Layout
Fig 2. Proposed Model
Model 1: Bare Frame with mass of infill .Model 2: with brick infill masonry wall run throughout the height of the building. Model 3: With 2 horizontal shear wall and 2 vertical shear walls at middle of outer edges. Model 4: With 3 vertical shear walls (i.e. 2 at outer corners and 1 at middle) and 2 horizontal shear walls (i.e. at middle of top and bottom) at the edges. Model 5: With 6 horizontal shear walls with 4 at outer edge corners and at middle of inner edges. Model 6: With 6 vertical shear walls, 4 at outer edge corners and 2 at middle of inner edge. Model 7: With 6 shear walls, 4 horizontal at outer edge corners and 2 vertical at middle of inner edges. Model 8: With 6 shear walls, 4 vertical shear walls at outer edge corners and 2 horizontal shear walls at middle of outer edges. Model 9:
With 7 shear walls, 6 vertical shear walls (4 at outer edge corners and 2 at inner edges) and one horizontal shear walls at outer edge corner. Model 10: With 7 shear walls, 4 horizontal at outer edge corners and 3 vertical shear walls (2 at inner edge and 1 at outer edge). Model 11: With 8 shear walls, 4 vertical (2 at inner edge and 2 at outer edge corners) and 4 horizontal at outer edge corners. Model 12: With 8 shear walls, 4 vertical ( 2 at inner edge and 2 at outer edge corners) and 4 horizontal ( 2 at inner edge and 2 at outer edge corners).Model 13: With 8 shear walls, 4 vertical and 4 horizontal at outer edge corners.
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RESULTS AND DISCUSSION
Time Period in Sec
Time Period in Sec
-
Fundamental Time Period
2.5
2
1.5
1
0.5
IS CODE
ETABS
2.5
2
1.5
1
0.5
IS CODE
ETABS
0
0
1 2 3 4 5 6 7 8 9 10 11 12 13
Model No.
1 2 3 4 5 6 7 8 9 10 11 12 13
Model No.
Chart 1. Time Period Vs Models.
The above graph (Chart 1.) shows the variation of time period for the different models obtained using IS code and ETABS analysis. It shows that natural time period of bare frame model from ETABS analysis resulted in higher value as compared to the value obtained from the IS code.
Time period is smallest for model 11 in ETABS analysis when compared to other infill category models ( i.e. from Model 2 to Model 13). Therefore it can be clearly understood from the Chart 1 that the infill and the shear walls, decrease the natural time period of the building.
12000
10000
8000
6000
4000
12000
10000
8000
6000
4000
IS Code
Fx (ESA) Fy (ESA)
IS Code
Fx (ESA) Fy (ESA)
Base Shear in KN
Base Shear in KN
-
Design Seismic Base Shear
1
2
3
4
5
7
Model No.
9 10 11 12 13
1
2
3
4
5
7
Model No.
9 10 11 12 13
2000
0
2000
0
6
6
8
8
Chart 2. Base shear Vs Models
From the graph (Chart 2) it is seen that the values of Base Shear for the Bare Frame in both the methods are least as compared to other models. The IS code method
graph lies at the bottom, which means that the codal method gives the lower values of base shear than ETABS.
80000
70000
60000
50000
40000
30000
20000
10000
0
EQSA RSA
Push Over
80000
70000
60000
50000
40000
30000
20000
10000
0
EQSA RSA
Push Over
1 2 3 4 5 6 7 8 9 10 11 12 13
Model No.
1 2 3 4 5 6 7 8 9 10 11 12 13
Model No.
Base Shear in KN
Base Shear in KN
Base Shear in KN
Base Shear in KN
Chart 3. Comparison of Base shear by ESA, RSA, and Pushover for various Models along longitudinal direction.
60000
50000
40000
30000
20000
EQSA RSA
Push Over
60000
50000
40000
30000
20000
EQSA RSA
Push Over
10000
0
10000
0
1 2 3 4 5 6 7 8 9 10 11 12 13
Model No.
1 2 3 4 5 6 7 8 9 10 11 12 13
Model No.
Chart 4. Comparison of Base shear by ESA, RSA, and Pushover for various Models along transverse direction
The above graph (Chart 3 and Chart 4) for Base shear shows least value for the Bare Frame (Model 1) in all the 3 methods of analysis performed using ETABS.
Pushover analysis lies at the top, showing higher values with greater variation of Base shear in different models.
Storey Drift in m
Storey Drift in m
-
Storey Drifts
0.0009
0.0008
0.0007
0.0006
0.0005
0.0004
0.0003
0.0002
0.0001
0
ESA
RSA PUSHOVER
0.0009
0.0008
0.0007
0.0006
0.0005
0.0004
0.0003
0.0002
0.0001
0
ESA
RSA PUSHOVER
1 2 3 4 5 6 7 8 9 10 11 12 13
Model No.
1 2 3 4 5 6 7 8 9 10 11 12 13
Model No.
Storey Drift in m
Storey Drift in m
Chart 5. Comparison of Storey Drift, Models and Methods of Analysis along longitudinal direction
0.005
0.004
0.003
0.002
0.001
ESA
RSA PUSHOVER
0.005
0.004
0.003
0.002
0.001
ESA
RSA PUSHOVER
0
0
1
2
3
4
5
6
7
8
9 10 11 12 13
1
2
3
4
5
6
7
8
9 10 11 12 13
MODEL NO.
MODEL NO.
Chart 6. Comparison of Storey Drift, Models and Methods of Analysis along transverse direction
The graphs Chart 5 and Chart 6 show the comparison of Story drift values of different models along transverse and longitudinal direction obtained using ESA, RSA and Pushover analysis. From the above charts we can see that the values of drift are maximum in case of pushover analysis for models with shear walls. The Model
13 and Model 11 in RSA shows the minimum values of Storey drift along transverse and longitudinal direction respectively in RSA when compared to other models with shear walls. The storey drift values are maximum for Bare frame model along longitudinal in ESA and for model 5 along transverse in Pushover analysis
Storey Displacement in mm
Storey Displacement in mm
-
Storey Displacement
35
30
25
20
15
10
5
0
ESA
RSA PUSHOVER
35
30
25
20
15
10
5
0
ESA
RSA PUSHOVER
1 2 3 4 5 6
8
9 10 11 12 13
1 2 3 4 5 6
8
9 10 11 12 13
7
Model No..
7
Model No..
Storey Displacement in mm
Storey Displacement in mm
Chart 7.Comparison of Storey Displacement, Models and Methods of Analysis along longitudinal direction.
180
160
140
120
100
80
60
ESA
RSA PUSHOVER
180
160
140
120
100
80
60
ESA
RSA PUSHOVER
1
2
3
4
5
6
7
8
9 10 11 12 13
1
2
3
4
5
6
7
8
9 10 11 12 13
MODEL NO.
MODEL NO.
40
20
0
40
20
0
Chart 8. Comparison of Storey Displacement, Models and Methods of Analysis along transverse direction.
The Chart 7 and Chart 8 shows the comparison of Story displacement values of different models along transverse and longitudinal direction obtained using ESA, RSA and Pushover analysis. From the charts it is seen that Model 9 and Model 13 showed minimum values of storey displacement in RSA along longitudinal direction. Model
11 along transverse direction in RSA showed minimum value when compared to the other models with shear walls. Graphs also show that the storey displacement is maximum for Bare Frame along longitudinal direction in ESA and also along transverse direction for model 13 in Pushover analysis.
-
Beam Moments and Column Moments
Beam Moments (KN-m)
Beam Moments (KN-m)
140
120
100
80
60
40
20
0
Beam Moments (KN-m)
140
120
100
80
60
40
20
0
Beam Moments (KN-m)
1 2 3 4 5 6 7 8 9 10 11 12 13
1 2 3 4 5 6 7 8 9 10 11 12 13
Chart 9. Beam Moment Vs Model No.
The Chart 9 shows the maximum values of beam moments for each model obtained by comparing ESA, RSA and Pushover analysis. It is found that the Beam
moment for the model 8 is maximum (126.8980 KN-m) and model 10 (93.0701 KN-m) is minimum when compared to other models in all the methods of analysis.
2500
2000
1500
1000
500
0
M2
M3
2500
2000
1500
1000
500
0
M2
M3
1 2 3 4 5 6
1 2 3 4 5 6
7
Model No.
7
Model No.
8
8
9 10 11 12 13
9 10 11 12 13
Column Moments in KN-m
Column Moments in KN-m
Chart 10. Column Moments for Different Models
The Chart 10 shows the maximum values of beam moments for all the 13 models obtained from ESA, RSA and Pushover analysis. It can be noted that the column moments are maximum for Model 11 (M2 = 1166.4374KN-m) and Model 8 (M3 = 2219.2285 KN-m)
and minimum for the Model 1 (M3 = 103.15KN-m and M3
= 273.88 KN-m).
-
-
CONCLUSION
-
From the analysis using ETABS the fundamental Time Period showed lower values than IS code method, hence the time period can be reduced by providing shear walls at centre and outer edge corners in longitudinal direction for the irregular shape buildings.
-
From both IS Code and ETABS (ESA, RSA and Pushover) methods the Bare Frame is found to have least Base Shear values. It increases as the shear walls are added to the structure.
-
Pushover analysis give higher values of base shear in all the models compared to other methods of seismic analysis.
-
Design Seismic Base Shear obtained from using IS Code method is not in a good agreement with the values obtained from Equivalent Static method of analysis in ETABS.
-
The Storey Drift values are within the limits specified by the IS 1893-2002 (Part 1).
-
Storey Drifts can be reduced by providing the shear walls at the outer edge corners in both direction and also vertical shear walls at centre of the structure. It increases with the reduction of
shear walls in the structure and is also maximum for the model with only longitudinal (horizontal) shear walls.
-
Increase in number of shear walls is effective in reducing the Storey Displacements.
-
Providing the shear walls at outer edge corners as well as at centre (vertical direction) helps in reducing the values of storey displacements.
-
The beam moments can be reduced by providing shear walls at outer edge corners in horizontal (longitudinal) direction and at centre in vertical (transverse direction) direction. It increases as shear wall number in both direction are nearly equal each other.
-
Column moments can be controlled by providing shear walls in both directions at centre as well as outer edge corners.
-
Hence from the above work it can be concluded that the model with shear walls at corners as well as at centre (with vertical orientation) helps in controlling the seismic parameters.
REFERENCES
-
Dr. S. A. Halkude, Mr. C. G. Konapure, Ms. C. A. Madgundi, Effect of Seismicity on Irregular Shape Structure (Civil Engg. Dept. Walchand Institute of Technology Solapur, Solapur University, India.
-
Dr. H.S. Chore, P.A.Dode, N.L.Sawakare, Effect of Shear Wall on Response of Multi-storied Building Frame. Department of Civil Engineering Datta Meghe College of Engineering, Airoli, Navi Mumbai, India.
-
S.A. Halkude, C.G. Konapure and S.M.Birajdar, Effect of Location of Shear Walls on Seismic Performance of Buildings. Vol.5, No.2 (April 2015), International Journal of Current Engineering and Technology.
-
Kasliwal Sagar K., Prof. M.R.Wakchaure, Anantwad Shirish, Effects of Numbers and Positions of Shear Walls on Seismic Behavior of Multistory Structure. Department of Civil Engineering. University of Pune Pune,Maharshtra,India.
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Aung Mon, Tin Tin Htwe, Study on Performance of Discrete Staggered Shear Walls in 25-Storeyed RC Building. International Journal of Scientific Engineering and Technology Research, ISSN 2319-8885 Vol.03, Issue.17 August-2014, Pages: 3573-3578.
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Shrikhande.M and Agarwal.P, Earthquake Resistant Design of Structures, Prentice Hall of India Private Limited, New Delhi.
-
IS 456: 2000, Indian Standard Code of Practice for Plain and Reinforced Concrete, Bureau of Indian Standards, New Delhi.
-
IS 875: 1987, Code of practice for design loads (other than earthquake) for building and structures – Part 2: Imposed loads, Bureau of Indian Standards, New Delhi.
-
IS 1893 (Part I): 2002, Criteria for Earthquake Resistant Design of Structures, Bureau of Indian Standards, New Delhi.
-
S.K Duggal, Earthquake Resistant Design of Structures. Oxford University Press,Civil Engineering Department, Motilal Nehru National Institute of Technology, Allahabad.