Contents lists available at http://iosi.in/index.php/iosijecs ISOI Journal of Engineering and Computer science Volume 1 Issue 1; Page No. 07-17

Effect of shear wall location in buildings subjected to seismic loads Lakshmi K.O.1, Prof. Jayasree Ramanujan1, Mrs. Bindu Sunil2, Dr. Laju Kottallil3, Prof. Mercy Joseph Poweth4 1

Department of Civil Engineering, M.A. College of Engineering, Kothamangalam, India. 2

M.Tech (Structural) M.I.E, Technical Director, Geostructurals (P) Ltd. India

3

P. G. Coordinator, Department of Civil Engineering, M.A. College of Engineering, Kothamangalam, India. 4

HOD, Department of Civil Engineering, M.A. College of Engineering, Kothamangalam, India.

ARTICLE INFO

ABSTRACT

Received 15 Nov. 2014 Accepted 20 Dec. 2014

Performance of structures under frequently occurring earth quake ground motions resulting in structural damages as well as failures have repeatedly demonstrated the seismic vulnerability of existing buildings, due to their design based on gravity loads only or inadequate levels of lateral forces. This necessitates the need for design based on seismic responses by suitable methods to ensure strength and stability of structures. Shear wall systems are one of the most commonly used lateral load resisting systems in high rise buildings.. This study aims at comparing various parameters such as storey drift, storey shear, deflection, reinforcement requirement in columns etc of a building under lateral loads based on strategic positioning of shear walls. Based on linear and nonlinear analysis procedures adopted, the effect of shear wall location on various parameters are to be compared .Pushover analysis is used to evaluate the expected performance of the structure by estimating its strength and deformation demands in design earthquakes by means of static inelastic analysis, and comparing these demands to available capacities at the performance levels of interest. The capacity spectrum method is used to obtain the overall performance level of a structure. The software used is ETABS 9.5 and SAP 2000.V.14.1

Corresponding Author: Prof. Jayasree Ramanujan 1 Department of Civil Engineering, M.A. College of Engineering, Kothamangalam, India. .

they can form an efficient lateral force resisting system by reducing lateral displacements under earthquake loads. Therefore it is very necessary to determine effective, efficient and ideal location of shear wall. PERFORMANCE EVALUATION Structural behaviour under seismic loading requires an understanding of the behaviour under large inelastic deformations .Nonlinear Static Procedure/ Pushover analysis can be used to evaluate building loaded beyond the elastic range. The capacity spectrum method is one of the most established and widely accepted displacement based seismic design method which is used for performance based seismic design. II. LITERATURE REVIEW  Significance of Shear Wall in High rise Buildings  Static linear and nonlinear analysis procedures for determining structure responses under seismic forces  Performance based analysis of structures.

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INTRODUCTION There has been a considerable increase in the construction of tall buildings both residential and commercial and the modern trend is towards more tall and slender structures. Thus the effects of lateral loads like wind loads, earthquake loads and blast forces are attaining increasing importance and almost every designer is faced with the problems of providing adequate strength and stability against lateral loads. Shear wall system is one of the most commonly used lateral load resisting system in high rise buildings. Shear wall has high in plane stiffness and strength which can be used to simultaneously resist large horizontal loads and support gravity loads, which significantly reduces lateral sway of the building and thereby reduces damage to structure and its contents. Shear walls in buildings must be symmetrically located in plan to reduce ill-effects of twist in buildings. When shear walls are situated in advantageous positions in the building,

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resistance and flexibility of structure. Building collapse is caused due to these inertia forces. Because earthquake ground motion is three-dimensional, the structure, in general, deforms in a three dimensional manner. Generally inertia forces generated by the horizontal components of ground motion require greater consideration for seismic design since adequate resistance to vertical seismic loads is usually provided by the member capacities required for gravity load design. The type of analysis to obtain seismic force, and their distribution to different levels along height of the building and to various lateral load resisting elements, depends on the height of the building, severity of the seismic zone in which the building is located and on the classification of the building as regular or irregular. METHODOLOGY Methods for Seismic analysis of buildings may be classified as follows: 1) Equivalent Static Analysis (Linear Static) 2) Response Spectrum Analysis (Linear Dynamic) 3) Pushover Analysis (Nonlinear Static) 4) Time History Analysis (Nonlinear Dynamic) EQUIVALENT STATIC ANALYSIS In Equivalent static analysis it is assumed that the structure responds in its fundamental mode. The response is read from a design response spectrum, given the natural frequency of the structure. This method work well for low to medium-rise buildings without significant coupled lateral–torsional modes, in which only the first mode in each direction is of significance. NONLINEAR STATIC PUSHOVER ANALYSIS Pushover analysis is a simplified, static, nonlinear analysis under a predefined pattern of permanent vertical loads and gradually increasing lateral loads. Typically the first pushover load case is used to apply gravity load and then subsequent lateral pushover load cases are specified to start from the final conditions of the gravity pushover. Typically a gravity load pushover is force controlled and lateral pushovers are displacement controlled. Load is applied incrementally to frameworks until a collapse mechanism is reached. Thus it enables determination of collapse load and ductility capacity on a building frame. Plastic rotation is monitored, and a lateral inelastic force versus displacement response for the complete structure is analytically computed. This type of analysis enables weakness in the structure to be identified. The decision to retrofit can be taken in such studies. The ATC-40 document have developed modeling procedures, acceptance criteria and analysis procedures for pushover analysis. As shown in Figure 3, five points labeled A, B, C, D, and E are used to define the force deflection behavior of the hinge and three points labeled IO, LS and CP are used to define the acceptance criteria for the hinge. The range AB is elastic range ,IO,

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Bozdogan K.B.,Deierlein et.al.,2010 [1] discussed in detail the modeling issues, nonlinear behavior and analysis of the frame – shear wall structural system. An approximate method which is based on the continuum approach and one dimensional finite element method to be used for lateral static and dynamic analyses of wall-frame buildings is presented. Shaik Kamal Mohammed Azam.,2013 [2] presented a study on seismic performance evaluation of multistoried rc framed buildings with shear wall. A comparison of structural behavior in terms of strength, stiffness and damping characteristics is done.The provision of shear wall has significant influence on lateral strength in taller buildings while it has less influence on lateral stiffness in taller buildings. The provision of shear wall has significant influence on lateral stiffness in buildings of shorter height while it has less influence on lateral strength. The influence of shear walls is significant in terms of the damping characteristics and period at the performance point for tall buildings. Provision of shear walls symmetrically in the outermost moment-resisting frames and preferably interconnected in mutually perpendicular direction forming the core will have better seismic performance in terms of strength and stiffness. Shahabodin ,Zaregarizi;2013 [4] presented a study on Comparative investigation on using shear wall and concrete infill to improve seismic performance of existing buildings in areas with high seismic potential. Results shows that concrete fills have considerable strength than brick in fills. whereas the displacement acceptance of brick infills is higher than concrete infills. Masonry infills as lateral resisting elements have considerable strength which can prevent even collapse in moderate earthquakes. Performance of concrete infills is dependent on adjacent elements especially columns, so premature failure in columns due to strong axial forces must be considered.Misam Abidi, Mangulkar Madhuri. N;2012 [5] presented an assessment to understand the behavior of Reinforced Concrete framed structures by pushover analysis and the Comparative study was done for different models in terms of base shear, displacement, performance point. The inelastic behaviour of the example structures are examined by carrying out displacement controlled pushover analysis. III. SEISMIC RESISTANT DESIGN OF BUILDINGS No building can remain entirely free of damage during quake, still, all structures, big or small; can be made to withstand earthquakes of a particular magnitude by taking certain precaution. STRUCTURAL RESPONSE The behavior of a building during an earthquake is a vibration problem. If the base of a structure is suddenly moved the lower portion of a building tends to vibrate, but the upper part of the structure will not respond instantaneously, but will lag because of inertial

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Prof. Jayasree Ramanujan, et al. ISOI Journal of Engineering and Computer science

Prof. Jayasree Ramanujan, et al. ISOI Journal of Engineering and Computer science

LS and CP stand for Immediate Occupancy, Life Safety and Collapse Prevention respectively. PERFORMANCE POINT The intersection of capacity spectrum with appropriate demand spectrum in capacity spectrum method. If the performance point exists and damage state at that

Figure 1: Capacity spectrum curve

point is acceptable, we have a building that satisfies the push-over criterion. Depending on the position and state of the performance point the analyst may decide on how safe or vulnerable the structure is and where possible strengthening should be performed.

Typical seismic demand vs capacity plots. Figure 2: (a)safe design (b)unsafe design

CAPACITY CURVE

Figure 3: Idealized force- deformation curve for a Hinge

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relatively low uncertainty. In nonlinear dynamic analyses, the detailed structural model subjected to a ground-motion record produces estimates of component deformations for each degree of freedom in the model and the modal responses are combined using schemes such as the square-root-sum-of-squares. IV. STRUCTURAL MODELING AND ANALYSIS The Finite Element analysis software ETABS 9.5 is used to create the 3-D model and run the linear static and dynamic analyses and Pushover analysis is done in SAP2000 .V.14.1 .Eight different models were considered. DETAILS OF THE MODELS The model adopted for the study is a symmetric sixteen storey (G+15) residential building having ground storey height of 3m and typical floor height of 3m founded on medium soil .

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PERFORMANCE LEVEL Performance Level is defined as the expected behavior of the building in the design earthquake in terms of limiting levels of damage to the structural and nonstructural components . METHODS OF DYNAMIC ANALYSIS 1) Linear Dynamic Response Spectrum Analysis Response spectra are curves plotted between maximum response of SDOF system subjected to specified earthquake ground motion and its time period (or frequency). Plot with system time period on x - axis and response quantity on y - axis is the response spectra pertaining to specified damping ratio and input ground motion 2) Nonlinear Dynamic Time History Analysis Nonlinear dynamic analysis utilizes the combination of ground motion records with a detailed structural model, therefore is capable of producing results with

Prof. Jayasree Ramanujan, et al. ISOI Journal of Engineering and Computer science

Figure 4: Floor Plan (Typical)

calculated and assigned as uniformly distributed loads on beams. Rest is automatically considered by program itself. Live loads have been assigned as uniform area loads on slab elements as per IS 875(Part 2) Live load on roof=2kN/ m2 4.5 LOAD COMBINATIONS The load combinations considered for the analysis and design is as per IS: 1893-2002. ANALYSIS OF THE STRUCTURE 1) Equivalent Static method 2) Response Spectrum Analysis 3) Pushover Analysis EQUIVALENT STATIC METHOD The natural period of the building is calculated by the expressions T= 0.075 x h0.75 for bare frame and

T  0.09 h d for in filled frame as given in IS 1893 (Part 1) -2002, wherein h is the height and d is the base dimension of the building in the considered direction of vibration. The lateral load calculation and its distribution along the height are done as per IS: 1893 (part 1)-2002. The seismic weight is calculated using full dead load plus 25% of live load. Ta = = 0.85sec in x- direction (1) Ta =

= 0.94 sec in y – direction

(2)

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RESPONSE SPECTRUM ANALYSIS Response spectrum analysis of all the models are done .The parameters provided are Z=0.16 ,considering zone factor III I=1 ,considering residential building. R=5.0, considering special RC moment resisting frame.(SMRF)

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MODEL I - (MAC) : The model is symmetric in plan and is modeled with only column elements and no shear walls in layout. MODEL II - (MCE) : Model consists of shear wall provided in central core area and columns in all other positions . MODEL III - (MX) : Model consists of columns in all positions along with shear walls placed parallel to the X (Longitudinal)axis MODEL IV - (MY) : Model consists of columns in all positions along with shear walls placed parallel to the Y (Transverse)axis MODEL V - (MCO) : Shear wall is provided in all four corners of the building . MODEL VI - (MCC) : Model is assigned with shear walls at central core area as well as corners . MODEL VII - (MCX) : Model is assigned with shear walls at central core area and as well as in direction parallel to the X (Longitudinal)axis. MODEL VIII - (MCY) : Model is assigned with shear walls at central core area and also in direction parallel to the Y (Transverse)axis MATERIAL AND FRAME ELEMENT PROPERTIES The mix of concrete used for beams and slabs is M20 and that for columns is M40. Beams of size 200x600 and columns of size 300x1000 have been defined. Slab thickness is provided as required for the spans as per code. Shear walls provided are of thickness 200 mm and length 2500 mm except for core area where the central portion consists of a shear wall of length 2000 mm. Fixed supports are provided at base. LOADS ASSIGNED Gravity loads on structure include the weight of beams, slabs, columns and walls. The wall loads have been

Prof. Jayasree Ramanujan, et al. ISOI Journal of Engineering and Computer science

PUSHOVER ANALYSIS PUSHOVER ANALYSIS PROCEDURE CREATE 3D MODEL

GRAVITY PUSHOVER (FORCE CONTROLLED)

ASSIGN END OFFSETS

LATERAL PUSHOVER RUN STATIC PUSHOVER ANALYSIS (DISPLACEMENT CONTROLLED)

DEFINE HINGE PROPERTIES

ASSIGN HINGE PROPERTIES

ESTABLISH PERFORMANCE POINT

BEAM - DEFAULT V2&M 3 COLUMN - DEFAULT PM2M3 DEFINE STATIC PUSHOVER CASE STRUT – AXIAL P

Figure 5: Flow chart for Pushover analysis

IV. RESULTS AND DISCUSSIONS COMPARISON BETWEN EQUIVALENT STATIC METHOD AND RESPONSE SPECTRUM METHOD From the analysis results obtained following parameters are taken into consideration for the present study. STOREY DRIFT Story drift can be defined as the lateral displacement of one level relative to the level above or below it: As per Clause no. 7.11.1 of IS 1893 (Part 1): 2002, the storey drift in any storey due to specified design lateral force with partial load factor of 1.0, shall not exceed 0.004

Figure 6: Story Drift comparison of the models (Equivalent Static Method - X direction)

times the storey height. Maximum drift permitted = 0.004 x 3000 = 12mm.By comparing the drift values obtained for all models obtained using both methods ,it could be seen that in models with shear wall provided at core as well as in corners the inter story drift has considerably been reduced when compared to the bare frame model as well as those models in which shear walls are provided only in longitudinal or transverse directions. Fig 6 & 7 illustrates the comparison of story drift in X and Y directions in mm for all models using Equivalent Static Method.

Figure 7: Story Drift comparison of the models (Equivalent Static Method - Y direction

Figure 8: Story Drift comparison of the models (Response Spectrum Method- X direction)

Figure 9: Story Drift comparison of the model (Response Spectrum Method-Y direction)

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Fig 8 & 9 illustrates the comparison of story drift in X and Y directions in mm for all models using Response Spectrum Method

Prof. Jayasree Ramanujan, et al. ISOI Journal of Engineering and Computer science Table 1: Percentage variation in maximum Story drift values in X and Y directions using Equivalent static and Response spectrum methods

Percentage variation in maximum Story drift values in X and Y directions using Equivalent static and Response spectrum methods (In comparison with bare frame model) Equivalent static Response spectrum method method MODEL X direction Y direction X direction Y direction M 19.4 13.9 33.9 20 CE M 39.9 -9.5 49.5 -14.9 X

M

-5.4

16.9

0.7

24

M

31.4

25.1

41.5

25.6

M M

40.03 52.3

32.6 8.2

46.3 46.3

29.5 12.1

M

15.9

25.5

30.6

31.8

Y CO CC CX CY

BASE SHEAR Base shear is the maximum expected lateral force that will occur due to seismic ground motion at the base of structure. Fig 10 & 11 compares the Base shear values of the models in X and Y directions respectively using Equivalent Static Method.

Figure 10: Base Shear VBx

Figure 11: Base Shear VBy

5.3.3 LATERAL DISPLACEMENT Fig 12 & 13 compares the Lateral displacement values in X and Y directions respectively using Equivalent Static Method.

Fig 14 & 15 compares the Lateral Displacement values in X and Y directions respectively using Response Spectrum Method.

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Figure 13: Lateral Displacement in Y direction (Equivalent static method)

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Figure 12: Lateral Displacement in X direction (Equivalent static method)

Prof. Jayasree Ramanujan, et al. ISOI Journal of Engineering and Computer science

Figure 14: Lateral Displacement in X direction (Response Spectrum Method)

Figure 15: Lateral Displacement in Y direction (Response Spectrum Method)

Table 2: Percentage reduction in maximum Lateral displacement values in X and Y directions using Equivalent static and Response spectrum methods Percentage reduction in maximum Lateral displacement values in X and Y directions using Equivalent static and Response spectrum methods(In comparison with bare frame model) Response spectrum method X direction Y direction

Equivalent static method MODEL

X direction

Y direction

MCE

23.68

15.3

19.06

MX

34.3

-12.46

40.8

-9.2

MY

-6.1

16.6

28.8

21.1

MCO

31.5

19.2

28.8

21.1

MCC

42.6

22.6

52.08

28.8

MCX

54.7

7.3

36.7

6.2

MCY

19

24.7

14.6

21.9

12.4

From the above results it can be observed that the maximum reduction in displacement value is obtained for Model M (Frame with Core and corner shear wall). CC

REINFORCEMENT DEMAND IN COLUMNS In order to determine the effect of shear walls on columns, reinforcement requirement in columns C11, C18 and C24 are compared for all the models. The variation in steel quantity requirement is shown graphically for all the models. 2

Table 3: Percentage variation in column reinforcement in mm for Column 11 2

Percentage variation in column reinforcement in mm for Column 11(In comparison with bare frame model) M

M

M

M

M

M

CE

X

Y

CO

CC

CX

CY

FIRST

34.7

28.9

-40

44.6

34.7

34.7

34.7

SECOND

24.9

1.53

-69.8

4.7

7.4

7.6

27.6

THIRD

0.76

7.7

-95

1

0.08

16.5

9.1

FOURTH

-0.5

26.9

-81

-0.2

34.37

34.37

3.76

FIFTH

-4.2

21.2

-74

5.9

21.2

21.2

-4.9

SIXTH

-6.16

7.07

-66.5

-0.3

7.07

7.07

-9

SEVENTH

-9.4

10.75

-99

-0.4

10.75

10.75

4.24

13

M

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Story No:

Prof. Jayasree Ramanujan, et al. ISOI Journal of Engineering and Computer science

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Table 4: Percentage variation in column reinforcement in mm for Column 18 2

Percentage variation in column reinforcement in mm for Column no 18(In comparison with bare frame model) M

CE

X

FIRST

11.6

-2.2

SECOND

-1

THIRD

M Y

M

M

M

M

CO

CC

CX

CY

-14.1

14.02

18.3

18.1

18.03

2.98

-23.4

0.83

6.7

4.95

1.23

-1.5

4.2

-33.9

1.17

0

7

1.74

FOURTH

-1.61

4.5

-55.7

0

1.29

7.54

-2.45

FIFTH

-13.6

12.6

-80

7.73

13.4

17.2

-19

SIXTH

-29.7

9.09

-110

9.09

0

9.09

-40.5

SEVENTH

-5

0

-89

0

0

0

-15.96

14

M

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Story No:

Prof. Jayasree Ramanujan, et al. ISOI Journal of Engineering and Computer science 2

Table 5: Percentage variation in column reinforcement in mm for Column 24 2

Percentage variation in column reinforcement in mm for Column no 24 (In comparison with bare frame model) Story No:

M

M

M

CE

X

FIRST

21.7

-44

SECOND

-14.5

THIRD

Y

M

M

M

CO

CC

CX

CY

-89.9

49.02

21.7

15.8

21.2

0.72

-60

6.1

11.8

14.3

-18.2

-20.8

0.23

-66

7.05

16.2

17.6

-19.06

FOURTH

-27

2.37

-64.8

4.12

26.3

18.4

-25.85

FIFTH

-34.9

8.8

-74

13.19

20.32

20.82

-37

SIXTH

-26.5

0

-82.3

0

0

0

-35.6

SEVENTH

0

0

-42.9

0

0

0

-0.16

From the results obtained it can be observed that though the reinforcement requirement in columns for top storeys are converging to minimum values ,for bottom storey's the reinforcement requirement in column shows considerable variation when provided with shear walls as compared to the bare frame model. In Model M and M ie.models with core shear walls CO

M

CC

and that with shear wall at core and corners, the percentage of steel required in columns in ground floor has come down by 44%, 18% and 49% and up to 34.7%

Figure 19: Pushover curve for model M

CC

,13.4% and 26.3% respectively in top floors when compared with bare frame model. PUSHOVER ANALYSIS Pushover analysis is carried out for all the models .The results obtained are shown below. Pushover curve is a plot of base shear versus roof displacement which is also known as the capacity curve. This curve gives an assessment of base shear induced at performance point. The performance point is obtained by superimposing demand spectrum and capacity curve transformed into spectral coordinates. The capacity spectrum obtained for model is shown below.

Figure 20: Capacity spectrum for model M

CC

PLASTIC HINGE LOCATIONS Location of weak points and potential failure modes that structure would experience in case of a seismic event is expected to be identified by pushover analysis. The possible hinge locations in model VI & I ie. M and M predicted by pushover analysis is shown in Fig 5.16 and 5.17.

Figure 21: Location of Plastic hinges in model M

CC

Figure 22: Location of Plastic hinges in model M

AC

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AC

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CC

Prof. Jayasree Ramanujan, et al. ISOI Journal of Engineering and Computer science

Fig 23 shows the plastic hinge formation in frame element 734.Hinge is formed within the immediate occupancy range. So member is safe within applied load limit.

Figure 23: Plastic hinge formation in frame element 734

Figure 24: Plastic hinge formation in frame element 2040

situated near to core area show a reduction in steel requirement up to 44.6% when shear wall is provided at the core and 34.7% when shear wall is located at core and corner of the structure. 5) Push over analysis results provides an insight into the performance of structures in post elastic range which thereby helps in assessing the weakness and possible failure mechanisms of structure which is not possible when using equivalent static and response spectrum method of analysis .This could be useful in rectifying the detrimental effects in the design stage itself or for adopting suitable retrofitting methods in case of post earthquake seismic hazard estimation. VI. SCOPE FOR FUTURE RESEARCH The volume of work undertaken in this study is limited to comparison of seismic response parameters in a building with different shear wall locations using linear and nonlinear analyses and Performance level evaluation using Pushover analysis .The study could be extended by including various other parameters such as torsional effects and soft storey effects in a building .Non linear dynamic analysis may be carried out for further study for better and realistic evaluation of structural response under seismic forces .

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V. CONCLUSIONS From the present investigation and the results obtained it can be concluded as following: 1) In medium high rise buildings (ie greater than 10 storeys) provision of shear walls is found to be effective in enhancing the overall seismic capacity characteristics of the structure. 2) From the comparison of story drift values it can be observed that maximum reduction in drift values is obtained when shear walls are provided at corners of the building . 3) Lateral displacement values obtained from static method of analysis indicate that shear wall provision along longitudinal and transverse directions are effective in reducing the displacement values in the same directions. Response spectrum analysis results provides a more realistic behavior of structure response and hence it can be seen that the displacement values in both X and Y directions are least in model with shear wall in core and corners when compared to all other models. 4) The reinforcement requirement in column is affected by the location and orientation of adjacent shear walls and columns ,ie alignment along weaker or stronger axis for the structure under consideration. Though the demand is varying ,it could be seen that the columns

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Table 6: Performance point comparison of models

Prof. Jayasree Ramanujan, et al. ISOI Journal of Engineering and Computer science

6.

7.

8.

9.

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1. Himalee Rahangdale , S.R.Satone, Design And Analysis Of Multi storied Building With Effect Of Shear Wall, Vol. 3, Issue 3, May-Jun 2013, pp.223232. 2. M.Y. Kaltakci, M.H. Arslan and G. Yavuz, Effect of Internal and External Shear Wall Location on Strengthening Weak RC Frames, Sharif University of Technology, August 2010,Vol. 17, No. 4, pp. 312323. 3. Shaik Kamal Mohammed Azam, Vinod Hosur, Seismic Performance Evaluation of Multistoried RC framed buildings with Shear wall, International Journal of Scientific & Engineering Research Volume 4, Issue 1, January-2013 4. P. B. Oni, Dr. S. B.Vanakudre, Performance Based Evaluation of Shear Walled RCC Building by Pushover Analysis, International Journal of Modern Engineering Research (IJMER) , Vol. 3, Issue. 4, Jul Aug. 2013 pp-2522-2525. 5. D. B. Karwar, Dr. R. S. Londhe, Performance of RC framed structure using Pushover analysis

,International Journal of Emerging Technology and Advanced Engineering, Volume 4, Issue 6, June 2014 Yousuf Dinar, Md. Imam Hossain, Rajib Kumar Biswas, Md. Masud Rana, Descriptive study of Pushover analysis in RC structures of Rigid joint, IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE), Volume 11, Issue 1 Ver. II (Jan. 2014), PP 60-68 ATC-40. “Seismic evaluation and retrofit of concrete buildings.” Volume 1 and 2. Applied Technology Council, California, 1996. [5] FEMA-273. “NEHRP guidelines for the seismic rehabilitation of buildings.” Federal Emergency Management Agency, Washington DC, 1997. FEMA-356. “Prestandard and commentary for the seismic rehabilitation of buildings.” Federal Emergency Management Agency, Washington DC, 2000. IS: 1893 (Part 1) 2002- Indian standard- “Criteria for earthquake resistant design of structures”, Bureau of Indian Standards, New Delhi

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