Seismic Analysis of Multistoried Symmetrical Building Based on Shear Wall Positions

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Seismic Analysis of Multistoried Symmetrical Building Based on Shear Wall Positions

Reeba Mary Cherian1,

1

PG Scholar,

Department of Civil engineering SBCE Elavumthitta, Pathanamthitta, Kerala, India

Aswathy S Kumar2

2

Assistant Professor,

Department of Civil engineering SBCE Elavumthitta, Pathanamthitta, Kerala, India

Abstract: The behaviour of a structure when subjected to some action can be obtained by structural analysis. The dynamic loads mainly consists of wind, waves, traffic, earthquakes, and blast loads. Any structure can be subjected to dynamic loading. Structural symmetry can be a major reason for buildings poor performance under severe seismic loading. Asymmetry contributes significantly to increased lateral deflections, increased member forces and ultimately the buildings collapse. This project is concerned with the study of seismic analysis in an irregular symmetrical building. Multi-storied buildings are behaved differently depending upon the various parameters like mass-stiffness distribution, foundation types and soil conditions. For this study, the parameters involved for analysis is storey displacement, base shear and storey drift. Here, the main aim is to make an analysis based on the different positions of the shear wall.

Keywords: Structural symmetry, seismic analysis, storey displacement, base shear, storey drift

  1. INTRODUCTION

    A building should consists of four main parameters, mainly simple and regular configuration, sufficient lateral strength, stiffness and ductility. Buildings having simple regular geometry suffer much less damage than the irregular configuration. Structural analysis is mainly concerned with finding out the behaviour of a structure when subjected to some action. Structural symmetry can be a major reason for buildings poor performance under severe seismic loading. Asymmetry leads to increased lateral deflections, increased member forces and ultimately the buildings collapse. Failure of structures starts at the points of weakness during an earthquake. This weakness mainly occurs due to discontinuity in mass, stiffness and geometry of structure. These discontinuities makes the structures an Irregular structure. During earthquakes, vertical irregularities are one of the major reasons of structural failures. During sudden collapse, structures with soft storey are the most prominent structures to get destructed. So, the effect of vertical irregularities in the seismic performance of structures becomes really important. This project is concerned with the study of seismic analysis and design of multi storey symmetric building. Etabs software is used here. In the present study, the Response Spectrum Analysis (RSA) of irregular RC building is carried out with shear walls provided at different positions of the building.

    • To perform seismic analysis on a multistoreyed symmetrical building with regular shear walls and stiffness irregularity

    • To develop different building models with shear walls provided at 3 different positions

    • To analyse the building by Response Spectrum Method

    • To identify the best position of shear wall in building by comparing the results.

  2. METHODOLOGY

    Methodology employed is Response Spectrum method using ETABS software.

      1. Modelling of Buildings

        Here, the study is carried out for the behaviour of G+15 RC buildings. Floor height provided is 3m and also properties are defined for the building structure.. Building is modelled for Indian seismic zone V from IS 1893-2002.

      2. Building Plan And Dimensions

    Fig.1. Plan of building

    Table 1. Building details

    Type of building

    Commercial building

    Size of beam

    300mm× 500mm

    Size of column

    900mm × 900mm

    Height of each storey

    3m

    Slab thickness

    150mm

    Wall thickness

    230mm

    Soil

    Medium

    Zone

    V

    Fig.2 Plan and 3D view of building with shear wall provided at the core (full height of the building)

    Fig.3 Plan and 3D view of building with shear wall provided at the core (soft storey)

    Fig.4 Plan and 3D view of building with shear wall provided at sides (full height of the building)

    Fig.5 Plan and 3D view of building with shear wall provided at sides (soft storey)

  3. COMPARISON OF RESULTS

    Table 2.Storey drift values for different positions of shear wall

    Core(full height)

    Core(soft storey)

    Sides(full height)

    Sides(soft storey)

    Max. storey drift

    0.000857

    0.000588

    0.000319

    0.00041

    The percentage reduction of storey drift for shear wall provided at sides(full height of the building) is 62.77% compared to shear wall provided at core position(full height of the building), 45.74% compared to shear wall provided at core(soft storey) and 22.19% compared to shear wall provided at sides (soft storey).

    Max. storey drift

    0.001

    0.0008

    0.0006

    0.0004

    0.0002

    0

    Max. storey

    drift

    Position of shear wall

    Max.Storey drift

    Fig.5 Variation of storey drift for building with different positions of shear wall

    Table 3.Storey shear values for different positions of shear wall

    Core(full ht)

    Core(soft storey)

    Sides(full ht)

    Sides(soft storey)

    Max. storey shear (kN)

    4165.171

    3485.604

    5699.043

    5709.352

    Max. storey shear (kN)

    6000

    5000

    4000

    3000

    2000

    Max.Storey Shear(kN)

    The percentage reduction of storey drift for shear wall provided at core (soft storey) is 16.31% compared to shear wall provided at core position(full height of the building), 38.83% compared to shear wall provided at sides (full height of the building) and 38.94% compared to shear wall provided at sides (soft storey).

    Position of shear wall

    Max. storey

    shear (kN)

    1000

    0

    Fig.6 Variation of storey shear for building with different positions of shear wall

    Table 4 : Storey displacement values for different positions of shear wall

    Core(full ht)

    Core(soft storey)

    Sides( full ht)

    Sides (soft storey)

    Storey displace ment

    50.31

    24.54

    36.90

    40.68

    Max.Storey displacement(mm)

    The percentage reduction of storey drift for shear wall provided at core (soft storey) is 51.23% compared to shear wall provided at core position(full height of the building), 33.49% compared to shear wall provided at sides (full height of the building) and 39.67% compared to shear wall provided at sides (soft storey).

    60

    50

    40

    30

    20

    10

    0

    Max. storey

    displacement(mm)

    Position of shear wall

    Max. storey

    displacement( mm)

    Fig.7 Variation of storey displacement for building with different positions of shear wall

    RESULTS AND DISCUSSIONS

    Maximum Storey Shear and Maximum Storey Displacement are lowest when the shear wall is placed in the core position having soft storey and greater when the shear wall is placed at the core (full height of the building), sides (full height of the building) and sides (soft storey). Maximum storey drift is lower when the shear wall is placed at the sides (full height of the building) when compared to shear walls placed at the core (full building height, soft storey) and also at sides (soft storey). The shear walls provided at core (soft storey) will give the best results to overcome the destruction occuring during an earthquake.

  4. CONCLUSIONS

In the present study, an attempt is made to study the dynamic behavior of building with shear walls provided at

4 different positions, i.e., at core(full height of the building), core (soft storey) , sides(full height of the building) and sides (soft storey). The parameters obtained from the analysis includes storey drift, storey shear and storey displacement. The best position of shear wall is obtained from the analysis. The best results obtained during analysis overcomes the destruction occuring during an earthquake. A comparative table of these results for the analysis has also been presented. The main conclusions obtained from the study are given below:

  • Maximum storey shear and maximum storey displacement is lowest when the shear wall is placed in the core position(soft storey) and greater when the shear wall is placed at the sides (soft storey as well as full height of the building) and also the core(full height of the building).

  • Maximum storey drift is lowest when the shear wall is placed at the sides(full height of the building) when compared to shear walls placed at the core(full height of the building, soft storey) and sides(soft storey).

  • Shear walls provided at core (soft storey) will give the best results to overcome the destruction occuring during an earthquake

ACKNOWLEDGEMENT

I am thankful to my guide, Asst. Professor, Aswathy S Kumar in Civil Engineering Department for her constant encouragement and able guidance. I am greatful to the Head of the department, Mini-project Coordinators and all the teachers of the Civil Engineering Department for their valuable suggestions and encouragement. I also thank my parents, friends for their continuous support in making this work a success. Above all, I thank the almighty God without whose blessing, I would never have been able to complete this work successfully.

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