Seismic Analysis of C, L, F, I Shapes Shearwalls Along with the Introduction of Raft Foundation in Different Seismic Zones in Type 3 Soil

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Seismic Analysis of C, L, F, I Shapes Shearwalls Along with the Introduction of Raft Foundation in Different Seismic Zones in Type 3 Soil

T. Harshavardhan1

M. Tech (Structural Engineering) Anurag Group of Institutions

Hyderabad.

Dr. A. Vimala2

M. Tech (Structural Engineering), (PhD) Anurag Group of Institutions

Hyderabad ISTE, ICACI, ICI

Abstract Shear wall is a structural member used to resist lateral forces Parallel to the plane of the wall. For slender walls where the bending deformation is more, Shear wall resists the loads due to Cantilever Action. In other words, Shear walls are vertical elements of the horizontal force resisting system. The present work deals with a study on the improvement shape of shear walls in symmetrical high rise building. In symmetrical buildings, the center of gravity and center of rigidity coincide, so that the shear walls are placed symmetrically. In this work a high rise building with different shapes of shear walls is considered for analysis. The multi storey building with 10 storey are analyzed for its storey drift, story displacement and base shear using ETABS software. For the analysis of the building for seismic loading with all Zones (Zone- II, III & IV Zone-V) is considered. The analysis of the building is done by using dynamic method(Response spectrum analysis).

Shear wall is a structural member used to resist lateral forces Parallel to the plane of the wall. For slender walls where the bending deformation is more, Shear wall resists the loads due to Cantilever Action. In other words, Shear walls are vertical elements of the horizontal force resisting system. In building construction, a rigid vertical diaphragm capable of transferring lateral forces from exterior walls, floors, and roofs to the ground foundation in a direction parallel to their planes. Examples are the reinforced-concrete wall. Lateral forces caused by wind, earthquake, and uneven settlement loads, in addition to the weight of structure and occupants, create powerful twisting (torsional) forces. This leads to the failure of the structures by shear. Shear walls are especially important in high-rise buildings subject to lateral wind and seismic forces. Generally, shear walls are either plane or flanged in section, while core walls consist of channel sections. They also provide adequate strength and stiffness to control lateral displacements.

Shear wall is a structural member used to resist lateral forces Parallel to the plane of the wall. For slender walls where the bending deformation is more, Shear wall resists the loads due to Cantilever Action. In other words, Shear walls are vertical elements of the horizontal force resisting system. In building construction, a rigid vertical diaphragm capable of transferring lateral forces from exterior walls, floors, and roofs to the ground foundation in a direction parallel to their planes. Examples are the reinforced-concrete wall. Lateral forces caused by wind, earthquake, and uneven settlement loads, in addition to the weight of structure and occupants, create powerful twisting (torsional) forces. This leads to the failure of the structures by shear. Shear walls are especially important in high-rise buildings subject to lateral wind and seismic forces. Generally, shear walls are either plane or flanged in section, while core walls consist of channel sections. They also provide adequate strength and stiffness to control lateral displacements.

  1. INTRODUCTION

    parallel to the force of the action. The core eccentrically located with respect to the building shapes has to carry out torsion as well as bending and direct shear. These shear wall resist horizontal forces because their high rigidity as deep beams, reacting to shear and flexure against the overturning. The Shear Wall shapes used in this work are,

    1. C

    2. L

    3. F

    4. I

  2. MODELLING OF BUILDING

Building details are selected based design by IS 456-2000 code, building dimensions are selected based on above literature reviews. Based on design, building details are listed in below table

Height of the building

30m

No. of stories

10

Height of each storey

3m

Grade of concrete

FE415

Grade of steel

M30

Depth of slab

300 mm

Size of the beams

400×400 mm

Size of the column

700×800mm

Shear wall thickness

300mm

Plan area

576 m²

In this work, models are considered to understand the seismic analysis of multi storied building with different shapes of shear walls. The models consist of 10 story building

DIFFERENT SHAPES OF SHEAR WALLS

The shape and location of the shear wall have significant effect on the structural behavior under lateral loads. Lateral loads are distributed through the structure acting as the horizontal diaphragm, to the shear walls,

Model 1

LSHAPE SHEAR WALL COMPARED IN SOIL TYPE 1,2,3AND EARTH QUAKE ZONES 2,3,4,5

Model 2

C SHAPE SHEAR WALL COMPARED IN SOIL 1,2,3 AND EARTH QUAKE ZONES 2,3,4,5

Model 3

F-SHAPED SHEAR WALL COMPARED IN DIFFERENT SOIL CONDITIONS AND EARTHQUAKE ZONES

Model 4

C,L SHEAR WALLS ON SOIL 3 TYPE IS PERFORMED USING RAFT FOUNDATION

MODEL5

F SHAPED SHEAR WALL ON SOIL 3 TYPE IS PERFORMED ON RAFT FOUNDATION.

MODEL 6

I SHAPE SHEAR WALL is performed on rft foundation

FIGURES

3D VIEW OF THE BUILDING WITH THE L SHAPE SHEAR WALLS

3D VIEW OF THE BUILDING WITH THE L SHAPE SHEAR WALLS

3D VIEW OF THE F SHAPED SHEAR WALL

MODAL ANALYSIS

The three dimensional reinforced concrete structures were analyzed by Response Spectrum Analysis using ETABS software. It is a linear dynamic statistical analysis method to indicate the likely maximum seismic response of an elastic structure. A plot of the peak acceleration for the mixed vertical oscillators. A response spectrum is simply a plot of the peak or steady-state response (displacement, velocity or acceleration) of a series of oscillators of varying natural frequency that are forced into motion by the same base vibration or shock. The analysis results will show the performance levels, behavior of the structures.

Design of raft foundation in etabs

  1. Meshing of the thick slab into the 20×20 quadrilaterals

  2. Assigning area springs to the slab with pin supports.

  3. Local axes are taken into consideration

  4. THICK SLAB OF 450 mm is choosen

3d view of the building with raft foundation

RESULTS AND DISCSSIONS

This chapter deals with the results and discussion of work. A comparison made between building models to know the seismic analysis of multi storied building with different shapes of shear walls. The linear dynamic analysis has done by using response spectrum method to know the maximum response of structure. The response is observed in terms of story displacement, story drift, and story shear. And linear dynamic analysis has done to know the seismic analysis of multi storied building with different shapes of shear walls at particular place. The results are observed for all the zones of models like zone II, III, IV and V. And also comparing the all results and select better shape of shear wall in zones.

L SHAPE SHEAR WALL RESULTS IN DIFFERENT ZONES

C SHAPE SHEAR WALL RESULTS IN DIFFERENT ZONES

Zones

RSX

RSY

II

Displacement

10.715

9.740

Drift

0.000225

0.000232

Shear

15384

16345

III

Displacement

17.324

15.960

Drift

0.000146

0.000167

Shear

24345

25678

IV

Displacement

24.774

36.466

Drift

0.000757

0.000878

Shear

10651

14614

V

Displacement

30.765

32.456

Drift

0.000245

0.000225

Shear

23876

19667

F SHAPE SHEAR WALL RESULTS IN DIFFERENT EARTHQUAKE ZONES

Zones

RSX

RSY

II

Displacement

26.546

25.808

Drift

0.000167

0.000210

Shear

4089

3478

III

Displacement

30.562

34.945

Drift

0.000253

0.000156

Shear

13450

14500

IV

Displacement

35.456

38.325

Drift

0.000744

0.000869

Shear

6450

9089

V

Displacement

40.564

43.562

Drift

0.000123

0.00358

Shear

26667

25678

Zones

RSX

RSY

II

Displacement

12.545

15.768

Drift

0.000167

0.000210

Shear

4089

3478

III

Displacement

15.675

18.987

Drift

0.000253

0.000156

Shear

12451

13506

IV

Displacement

19.657

24.564

Drift

0.000744

0.000869

Shear

36666

34678

V

Displacement

24.564

73.268

Drift

0.000999

0.00293

Shear

52244

55732

Zones

RSX

RSY

II

Displacement

12.545

15.768

Drift

0.000167

0.000210

Shear

4089

3478

III

Displacement

15.675

18.987

Drift

0.000253

0.000156

Shear

12451

13506

IV

Displacement

19.657

24.564

Drift

0.000744

0.000869

Shear

36666

34678

V

Displacement

24.564

73.268

Drift

0.000999

0.00293

Shear

52244

55732

I SHAPE SHEAR RESULTS IN DIFFERENT ZONES

Zones

RSX

RSY

II(0.1 SEISMIC FACTOR)

Displacement

12.432

14.548

Drift

0.000379

0.000334

Shear

6904

4123

III(0.16 SEISMIC FACTOR)

Displacement

15.564

18.725

Drift

0.000088

0.000115

Shear

21525

19678

IV(0.24 SEISMIC FACTOR)

Displacement

18.164

13.693

Drift

0.000187

0.000255

Shear

34564

32120

V(0.36 SEISMICFACTOR)

Displacement

26.563

15.735

Drift

0.000175

0.000225

Shear

25654

23458

STOREY DRIFT GRAPH OF ALL THE SHAPES OF THE SHEAR WALLS IN ZONE II

STOREY DRIFT

0.0004

0.0003

0.0002

0.0001

0

L SHAPE C SHAPE F SHAPE I SHAPE

0.0003

0.00025

0.0002

0.00015

0.0001

0.00005

0

NOW GRAPHS ON ZONE III

STOREY DRIFT

L SHAPE C SHAPE F SHAPE I SHAPE

RS X RS Y RSZ RS X RSY

STOREY DISPLACEMENTS IN ZONE II

STOREY DISPLACEMENT

STOREY DISPLACEMENT

STOREY DISPLACEMENT

40

30

20

10

0

40

30

20

10

0

30

25

20

15

10

5

0

L SHAPE C SHAPE F SHAPE

L SHAPE C SHAPE F SHAPE

I SHAPE

I SHAPE

RSX

RSX

RSY

RSY

Series 3

Series 3

LSHAPE C SHAPE F SHAPE I SHAPE CATEGORY RSX RSY

3 STOREY SHEAR IN ZONE II

20000

15000

10000

5000

0

STOREY SHEAR

L SHAPE C SHAPE F SHAPE I SHAPE

RSX RSY

30000

25000

20000

15000

10000

5000

0

STOREY SHEARS

L SHAPE C SHAPE F SHAPE I SHAPE

RSX RSY Series 3

NOW THE GRAPHS ON ZONE IV NOW THE GRAPHS ON ZONE V

0.001

0.0008

0.0006

0.0004

0.0002

0

STOREY DRIFTS

L SHAPE CSHAPE F SHAPE I SHAPE

0.0012

0.001

0.0008

0.0006

0.0004

0.0002

0

STOREY DRIFTS

LSHAPE CSHAPE F SHAPE I SHAPE

RSX RSY RSX RSY

STOREY DISPLACEMENTS

50

40

30

20

10

STOREY DISPLACEMENTS

80

60

40

20

0

L SHAPE C SHAPE F SHAPE I SHAPE

0

LSHAPE CSHAPE FSHAPE ISHAPE

RSX RSY RSX RSY

40000

30000

20000

10000

0

STOREY SHEARS

L SHAPE CSHAPE F SHAPE I SHAPE

60000

50000

40000

30000

20000

10000

0

STOREY SHEARS

L SHAPE C SHAPE F SHAPE I SHAPE

RSX RSY RSX RSY

COMPARISION WITH RAFT FOUNDATION

Results of the analysis of all the described shapes of the shear walls are discussed in the below table: zone factor 0.36,zone 5,type 3 soil conditions in which the building is analysed

C shape wall

RSX

RSY

Displcement(mm)

26

17.5

Storey drift(%)

0.006727

0.027346

Storey shear(kN)

22724

38508

L shape shear wall

RSX

RSY

Displacement(mm)

8

3.5

Storey drift(%)

0.00237

0.001438

Storey shear(kN)

15232

6000

GIVEN GRAPH SHOWN IS THE STOREY DRIFTS OF ALL THE SHAPES OF SHEAR WALLS

STOREY SHEARS

60000

50000

40000

30000

20000

10000

F shape shear wall

RSX

RSY

Displacement(mm)

55.5

42.4

Storey drift(%)

0.020853

0.015571

Storey shear(KN)

38597

48981

F shape shear wall

RSX

RSY

Displacement(mm)

55.5

42.4

Storey drift(%)

0.020853

0.015571

Storey shear(KN)

38597

48981

0

I shape shear wall

RSX

RSY

Displacement(mm)

56.7

54.3

Storey drift(%)

0.025045

0.025071

Storey shear(kN)

45108

45123

I shape shear wall

RSX

RSY

Displacement(mm)

56.7

54.3

Storey drift(%)

0.025045

0.025071

Storey shear(kN)

45108

45123

C SHAPE L SHAPE F SHAPE I SHAPE RSX RSY

GRAPHS OF THE GIVEN RESULTS:

  1. ZONE FACTOR 0.36

  2. ZONE 5

  3. SOIL TYPE -TYPE 3

USE OF RAFT FOUNDATION

GIVEN GRAPH SHOWS STOREY DISPLACEMENTS OF ALL THE SHAPES OF THE SHEAR WALL IN 10 STOREY BUILDING

GIVEN GRAPH INDICATES THE STOREY SHEARS OF ALL THE TYPES OF SHEAR WALLS IN 10 STOREY BUILDING DISCUSSED ABOVE

STOREY SHEARS

60000

50000

40000

STOREY DISPLACEMENT

60

50

40

30000

20000

10000

30

20

10

0

C SHAPE L SHAPE F SHAPE I SHAPE RSX RSY

0

C SHAPE L SHAPE F SHAPE I SHAPE RSX RSY

CONCLUSION

In this work, in the present study, an attempt is made to study the seismic Behavior of building with shear walls of four different shapes. First part of study included the dynamic analysis of building. The storey drift and base shear were obtained. A comparative table of these results for

all the shapes of shear wall has also been presented. In the next section conclusions obtained from the study is presented. a study on After analyzing the results obtained then it will be compared and find the seismic performance of the building.

From the graphical representations the following conclusions can be of :

PRIMARY OBSERVATION

  1. In zone 2 ,in the case of storey drift F AND shows the similar results.

  2. In the case of storey displacement ,C shape shear wall shows the better performance.

  3. In the zone3 ,case of storey drift L SHAPE has better performance.

  4. In the case of displacement,L and C has similar performances.

  5. In the case of zone 4 ,L SHAPE has shown the good results in the storey drifts and displacements.

  6. In the case of storey displacement ,L shape shows the better performance.

  7. In the zone 5,also L SHAPE has good performance in both the storey drifts and the storey displacements.

Final conclusion in primary observations:

L SHAPE SHEAR WALL HAS THE BETTER PERFORMANCE IN THE ZONE 3, ZONE 4, ZONE 5.

SECONDARY OBSERVATIONS:

From the analysis of in which the shear walls of different shapes l,c,f,i which are analysed on the weak soil with the design of the raft foundation in zone 5 ,the conclusions are:

  1. From the storey drift point of view, L shape indicates good results.

  2. From the storey displacement point of view L shape shows the good results.

  3. From the storey shear point of view, L shape shows the good results.

Overall conclusion from the secondary observations:

L SHAPE SHEAR WALL SHOW BETTER PERFORMANCES IN THE ZONE 5 ON THE WEAK SOIL WITH THE INTRODUCTION OF RAFT FOUNDATION ALSO.

FUTURE SCOPE FOR THIS STUDY

  1. Changing the size and thickness.

  2. Changing the orientation of the shear wall position and with the other shapes of them

  3. This can be extended to other irregular buildings.

  4. Other methods of the analysis can be performed.

REFERENCES

  1. Anand N. and Mightraj C. Seismic behavior of RCC shear wall under different soil conditions GEO trendz, Indian Geotechnical Conference, IGC-2010, IIT Bombay, December 16-18, 2010.

  2. A. Boominathan, G. R. Dodagoudar, A. Suganthi and R. Uma Maheswari Seismic Hazard Assessment Considering Local Site Effects for Microzonation Studies of Chennai city A Workshop on Microzonation ©Interline Publishing, Bangalore

  3. A.D. Pandey, Prabhat Kumar and Sharad Sharma Seismic soilstructure interaction of buildings on hill slopes Journal of Civil and Structural Engineering, 2011.

  4. A.D. Shirhatti and Dr. S.S. Quadri Seismic response analysis of RC frames considering soil structure interaction Proceedings of Indian Geotechnical Conference December 22-24, 2013, Roorkee.

  5. Bhattacharya, K., Dutta, S.C., and Dasgupta, S. (2004). Effect of soilflexibility on dynamic behaviour of building frames on raft foundation Journal of Sound and Vibration, 274, pp. 111135.

  6. Dutta, S.C., Maiti, A., Moitra, D. (1999). Effect of soil-structure interaction on column moment of building frames Journal of Institution of Engineers (India).

  7. IS 1893 (part 1): (2002), Criteria for Earthquake Resistant Design of Structures Part 1 General Provisions and Buildings, Bureau of Indian Standards.

  8. CSI Computers and Structures INC. Introductory Tutorial for Etabs: Linear and Nonlinear Static and Dynamic Analysis and Design of Three-Dimensional Structures 2011.

  9. B.C. Punmia, A.K. Jain, 2006, R.C.C Designs, Laxmi Publications New Delhi.

    IS-456 2000 plain and reinforced concrete code of practice. Agarwal, M.Shrinkhande, earthquake resistance design of structures, PHI larning Pvt. 2012.

  10. Theory of structures by Ramamrutham for literature review on kanis method.

  11. Reinforced and slab concrete structures by A.K. Jain and B.C. Punmia for design of beams, columns.

  12. Etabs Version 9.70 (1997), Computers and Structures, Inc, Berkeley, California, International Code Council, Inc (2000) International Building Code.

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