Seismic Analysis of Reinforced Concrete Frame Building with Infill Wall using ETABS

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Seismic Analysis of Reinforced Concrete Frame Building with Infill Wall using ETABS

Prof. Sunil Payghan1

1Assistant Professor, Department of Civil Engineering,

D.Y Patil College of Engineering, Pune, India

Diksha Gore2

2Final Year Student B.E, Department of Civil Engineering,

D.Y. Patil College of Engineering, Pune, India

Girija Shivankar3

3Final Year Student B.E, Department of Civil Engineering,

D.Y. Patil College of Engineering Pune, India

Pooja Tikone4

4Final Year Student B.E, Department of Civil Engineering,

D.Y. Patil College of Engineering, Pune, India

Shubham Kalbhor5

5Final Year Student B.E, Department of Civil Engineering,

    1. Patil College of Engineering, Pune, India

      AbstractReinforced concrete frame building with masonry infill wall is a common construction practice in developing countries like India. Infill walls serve as partitions in buildings. Infill walls are typically considered as nonstructural elements and its strength and stiffness is not considered in the general design; such an approach may lead to unsafe design. This paper focuses on the study of the effect of masonry infill wall on RC frame building. Response Spectrum Method is used for analysis purpose. The analysis is done on ETABS software and the results are discussed.

      KeywordsAnalysis, ETABS, frame, infill wall, masonry, nonstructural

      1. INTRODUCTION

        Earthquake is shaking of the ground in haphazard manner both horizontally and vertically due to sudden movement in the Earths tectonic plates. This shaking may result in the destruction of buildings and break the Earths surface. The seismic activity of an area defines the frequency, type and size of the earthquakes experienced over a period of time. The areas in seismic zones are prone to severe damages.

        Masonry is a commonly used material in developing countries like India. Masonry infill walls are equivalent to compressive struts and generally consists of bricks or concrete blocks constructed between the beams and columns of a reinforced concrete frame. Masonry infill walls basically serve as partitions in buildings. The infill walls are considered as an architectural or non-structural element and their design guidelines are not mentioned in the present IS Code, IS 1893:2016. In traditional practice it is considered that infill walls do not take any loads and therefore the resistance of walls is generally ignored in the design guidelines which may lead to an unsafe design. But it has been observed that frames with MI walls contribute significantly, in terms of enhanced strength and stiffness under earthquake induced lateral

        loading. The lateral deflection and bending moments are reduced in an RC frame consisting infill wall, thereby decreasing the probability of collapse. In high rise buildings, the vertical loads such as dead load and live load do not pose much of a problem, but the lateral loads due to wind or earthquake quivers are a matter of great concern and need special consideration in the design of buildings. These lateral forces can set up undesirable vibrations as a result of horizontal and vertical shaking. Therefore, it is necessary to evaluate the effects of MI walls on the load resisting capacity of RC frames. Infill walls or panels can be modeled using different methods such as equivalent diagonal strut method, equivalent frame method, finite element method, etc.

      2. AIM

        The aim of the research is to study the effect of masonry infill wall on RC frame building using Response Spectrum Method on ETABS.

      3. RESEARCH OBJECTIVES

        1. To study the effectiveness of masonry infill to resist seismic forces.

        2. To analyze the building using Response Spectrum Method on ETABS software.

        3. To study the results of various parameters such as story drift, displacement and deflection.

      4. METHODOLOGY

        Various IS Codes like IS 1893:2016(Part 1) and IS 456:2000 was referred for design purpose. The required architectural plan, sizes of beams and columns for analysis and design purpose is collected from a construction site of a multistorey building.

        Following data is used for modelling of RC framed building: Number of storeys: Thirteen

        Seismic Zone: III Floor Height: 3m Depth of Slab: 150mm

        Size of Beam: 200x600mm Size of Column: 700x700mm Live Load on floor: 4KN/m Floor finish: 1 KN/m

        Thickness of infill wall: 230mm

        Materials: M25, M30, HYSD 415, HYSD 500

        Density of concrete: 25 KN/m3 Density of infill: 20 KN/m3

        1. Following are the steps used for modelling:

          • First the grid line plan is prepared in ETABS.

          The materials like concrete, rebars are defined.

          Frame sections as beams,columns,slab,shear walls,strut are defined.

          Properties of slab, beams, columns , shear walls and strut are assigned.

          Define the static load cases and load patterns.

          Assign the loading as Dead load, Live load ,Seismic loads.

          Assign the support conditions as fixed and Analyze the model.

          Fig. 1. Grid Plan of building

        2. Modelling of equivalent Diagonal Strut

          Equivalent Diagonal Strut Method is the most common method to model infill wall. An infill wall is assumed to be a brace frame in this method which is equivalent to a compression strut. As per IS 1893:2016 (Part 1), the width of the diagonal strut is given as,

          wds = 0.175(h)-0.4 Lds

          thickness of masonry infill wall and is the angle of diagonal strut with the horizontal.

          Fig. 2. 3D Model of building with infill wall

        3. Response Spectrum Method

          Response Spectrum Method is also known as linear dynamic analysis method. Multiple mode shapes of building are considered in this method. The contribution from each natural mode of vibration is measured which indicates the maximum seismic response of a structure. The maximum values of member forces and displacements in each mode of vibration is calculated in this method.

        4. Analysis of Model

        The prepared model is analyzed for identifying the effect of masonry infill wall to earthquake resisting buildings. Analysis is done by Response Spectrum Method using ETABS. This is the accurate method of analysis.

        Load Patterns Used:

        1. Dead load

        2. Live load

        3. Seismic Load (EQx)

        4. Seismic Load (EQy)

        Load Combinations Used: D.L=3.75, L. L=4

        1.5 (D. L+L.L)

        1.5 (D. L+ EQx / EQy)

        1.2 (D.L + L.L + EQx / EQy)

        where

        where, Em and Ef are the modulus of elasticity of masonry and concrete, Ic is the moment of inertia of column, t is the

      5. RESULTS

        1. Modal Analysis:

          No of modes: 40

          Rz value of 1st mode = 0.0272< 0.05 First mode: Translation

          Time period difference = (0.866 – 0.732) = 0.134>0.1 Modal mass participation of last mode = 95%-97%

          Table No. 1. Modal Participating Mass Ratio obtained from ETABS

        2. Inter-Storey Drift Ratio:

          Inter storey drift ratio should be less than 0.004 To be checked for EQx and EQy

          Drift ratio for EQx = 0.001464 Drift ratio for EQy = 0.001683 Hence, passed.

          Fig. 3. Maximum story drift in X direction

          Fig. 4. Maximum story drift in Ydirection

        3. Maximum Displacement Against Earthquake:

          Maximum Displacement Against Earthquake:

          Maximum displacement against earthquake should be less than = H / 250 mm

          H = 39000mm

          To be checked for EQx and EQy H/250= 39000/250 = 156mm

          Maximum dsplacement against earthquake EQx = 11.59mm Maximum displacement against earthquake EQy = 15.79mm Hence, Passed.

          Fig. 5. Maximum Displacement in X direction

          Fig. 6. Maximum displacement in Y direction

        4. Check for Deflection

          Load combination used = D.L =1, L.L =1

          Maximum deflection < SPAN/350 or 20 mm (AS per IS 456:2000)

          Creep Coefficient: 3 Span = 6006.8 mm

          (Deflection of slab axial deformation of nearest column) x 3

          < SPAN /350 or 20mm

          (31.13 27.088) x 3 < 6006.8/350 = 12.126 < 17.16

          Hence, passed.

          Fig. 7. Maximum Deflection

        5. Maximum Story Displacement by Response Spectrum Analysis

        Fig. 8. Maximum story displacement obtained by response spectrum in X direction

        Fig. 9. Maximum story displacement obtained by response spectrum in Ydirection

      6. CONCLUSION

To analyze the effect of infill masonry wall on the response of multi storey RC framed building the Dynamic Response Spectrum Analysis is carried out, based on the results following points are concluded:

From the results of the Response Spectrum Analysis, it was concluded that the RC framed building with Infill walls has

good resistance to earthquake and can sustain the vibrations due to earthquake.

Based on the study of seismic analysis, following points are summarized:

  1. In the modal analysis as the modal mass participation of the highest mode is more than 90% thus it indicates the stiffness is more.

  2. The masonry infill walls reduce the time period in modal analysis.

  3. It can be observed that the maximum displacement against earthquakes and the inter-storey drift ratio is very less because of infill walls as compared to the bare frames.

  4. From the graphs of Response Spectrum Analysis in X- direction and Y- direction it was observed that the displacement is lesser because of stiffness.

    Thus, the Masonry Infill Walls in RC framed buildings make the structure more stiff for Earthquake excitations and can be used to reduce the lateral deflection.

    REFERENCES

    1. Robin Davis, Praseetha Krishnan, Devdas Menon, A. Meher Prasad, Effect of infill stiffness on seismic performance of multi- storey RC framed buildings in India, 13th World Conference on Earthquake Engineering Vancouver, B.C., Canada, 2004, Paper No. 1198.

    2. J. Dorji and D.P. Thambiratnam, Modelling and analysis of infilled frame structures under seismic loads, The Open Construction and Building Technology Journal, 2009, vol. 3.

    3. Haroon Rasheed Tamboli and Umesh.N. Karadi, Seismic analysis of RC frame structure with and without masonry infill walls, Indian Journal of Natural Sciences International Bimonthly, 2012, Vol.3 / Issue 14.

    4. Md Irfanullah, Vishwanath. B. Patil, Seismic evaluation of RC framed buildings with influence of masonry infill panel,

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    5. Khubaib Ilyas Khan M and Saim Raza, Seismic performance assessment of masonry infilled reinforced concrete (RC) frame structures, International Journal of Civil and Structural Engineering, 2015, Volume 6.

    6. Girum Mindaye and Dr. Shaik Yajdani, Seismic analysis of a multistorey RC frame building in different seismic zones, International Journal of Innovative Research in Science, Engineering and Technology, 2016, Vol. 5, Issue 9.

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    9. Pavan Pawar, Irshad Nadaf, Abhishek Pilane, Amol Nemade, Nikhil Mutha, Influence of infill wall in the performance of RC structure subjected to seismic load, International Journal of Research in Engineering, Science and Management, 2018, Volume-1, Issue-10.

    10. Dr. K. Chandrasekhar Reddy And G. Lalith Kumar, Seismic analysis of high-rise buildings (G+30) by using ETABS, International Journal of Technical Innovation in Modern Engineering & Science (IJTIMES), 2019, Volume 5, Issue 03.

    11. N.A. Khan, M.F. Tahir, C. Nuti, B. Briseghella, A.V. Bergami, Influence of brick masonry infill walls on seismic response of RC structures, Technical Journal, University of Engineering and Technology (UET) Taxila, Pakistan, 2019, Vol. 24, No. 3.

    12. Sujit Suryawanshi, Pallavi Vangari, Navnath Khadake, Study and comparison of structure having different infill material using ETABS, International Research Journal of Engineering and Technology (IRJET), 2020, Volume: 07 Issue: 08.

    13. Bureau of Indian Standards, Criteria for earthquake resistant design of structures, IS 1893 (Part1):2016.

    14. Bureau of Indian Standards, Plain and reinforced concrete code of practice, IS 456:2000.

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