SEISMIC BEHAVIOUR OF SYMMETRICAL AND UNSYMMETRICAL STRUCTURE WITH CANTILEVER SECTION USING ETABS SOF

International Research Journal of Engineering and Technology (IRJET) e-ISSN:2395-0056

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SEISMIC BEHAVIOUR OF SYMMETRICAL AND UNSYMMETRICAL STRUCTURE WITH CANTILEVER SECTION USING ETABS SOFTWARE

1M.Tech Scholar, Department of Civil Engineering, Sushila Devi Bansal College of Engineering, Indore

2Assistant Professor, Department of Civil Engineering, Sushila Devi Bansal College of Engineering, Indore

3Assistant Professor, Department of Civil Engineering, Sushila Devi Bansal College of Engineering, Indore ***

ABSTRACT

In this project two buildings of storey (G+12) are used, likes Symmetrical with cantilever section and Unsymmetrical with cantilever section. The distribution of mass, stiffness, and strength in both the horizontal and vertical planes of a multi-story framed building affect its performance during study seismic events. Strong earth shaking occurs during earthquakes, necessitating earthquake-resistant structural design. As a result, research into the seismic behaviour of unsymmetrical structures with cantilever sections is required. The building's centre of mass does not match to the centre of resistance in such structures. In comparison to symmetrical structures, this causes excessive edge deformation and shear forces in unsymmetrical structures. The goal of this research is to compare the sections used in wide span unsymmetrical cantilever constructions in order to reduce torsion analyzing wide span cantilevers with asymmetrical structures.

Keywords: Mass, Stiffness, Eccentricity, Earthquake, Multistoried Frame. ETABS, Torsion

1. INTRODUCTION

Inthecurrentsituation,anasymmetricalbuildingwithalongspancantileversectionisbeingbuilt,resultinginabnormalities such as soft storey, asymmetrical layout, and torsion irregularity, among others. As a result, seismic analysis of a long-span cantilever in an asymmetrical structure is critical. Because strong earth shaking occurs during earthquakes, seismic analysis and structure design are required to withstand this shaking. The seismic behaviour of unsymmetrical structures with cantilever sections has been investigated in this article. The centre of mass of the building does not match to the centre of resistance in this type of structure, resulting in excessive edge deformation and shear force in unsymmetrical buildings. The torsioneffectsincreaseastheeccentricitybetweenthecentreofstiffnessandthecentreofmassincreases.Torsioneffectscan thus be minimised by minimising the difference between the centre of mass and the centre of stiffness. This research also looks at the deflection characteristics of broad span cantilevers in asymmetrical structures under various loading circumstances.

2. OBJECTIVE OF STUDY

The major goal of this work is to investigate the seismic response of unsymmetrical structures with cantilever sections and examinethebehaviourofthestructuresusingresponsespectrumanalysisasatooltoreducetheeffectsofseismicforces.



Tostudyseismicbehaviorofsymmetricalstructure&unsymmetricalstructurewithcantileversectionbasedonmaterial andgeometry.



Tostudytheeffectoftorsionforsymmetricandunsymmetricmulti-storiedR.C.C.buildinginahighseismiczone.



To compare the response parameters such as storey drift, storey shear, displacement, of Symmetrical and conventional building.



To compare the torsional moment & overturning moment of Symmetrical and unsymmetrical structure with cantilever section.

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Toanalyzeparameterssuchasbendingmomentsandshearforcesinsymmetricalstructures&unsymmetricalstructures withcantileversections. 

To study the response of the symmetrical structure & unsymmetrical structure with cantilever sections subjected to gravityloadsandseismicloadingusingcomputer-aidedsoftware.

3. MODELLING APPROACH

3.1 Modelling Approach In ETABS

3.1.1 Modelling of Symmetrical Structure.

Fig. (3.1) Isometric view Symmetrical structure plan.

Fig.(3.2) Symmetrical structure plan upto storey 8.

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Fig.(3.3) Symmetrical structure plan storey 9 & Above.

MODEL INFORMATION

3.2.2 Modelling Of Unsymmetrical Structure.

Fig. (3.4) Isometric view Unsymmetrical Structure.

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Fig. (3.5) Unsymmetrical structure plan upto storey 8.

Fig. (3.6) Unsymmetrical structure plan storey 9 & above.

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Loads Combination

Loadcombinationfordesignpurposeshallbethoseproducemaximumforcesandeffectsandconsequentlymaximumstress anddeformations.AsperIS:456(Table18),IS:875(Part5)andIS:1893(Table6.3.1.2)thefollowingloadcombinationsare considered.

Loadcombination:-

1. DL+LL

2. 1.5(DL+LL)

3. 1.2(DL+LL-0.5WLX)

4. 1.2(DL+LL+0.5WLX) 5. 1.2(DL+LL-0.5WLY)

6. 1.2(DL+LL+0.5WLY)

7. 1.2(DL+LL-0.5EQLX)

8. 1.2(DL+LL+0.5EQLX)

9. 1.2(DL+LL-0.5EQLY)

10. 1.2(DL+LL+0.5EQLY)

11. 1.5(DL-WLX)

12. 1.5(DL+WLX) 13. 1.5(DL-WLY) 14. 1.5(DL+WLY) 15. 1.5(DL-EQLX) 16. 1.5(DL+EQLX) 17. 1.5(DL-EQLY) 18. 1.5(DL+EQLY) 19. 0.9DL-1.5WLX 20. 0.9DL+1.5WLX 21. 0.9DL-1.5WLY 22. 0.9DL+1.5WLY 23. 0.9DL-1.5EQLX 24. 0.9DL+1.5EQLX 25. 0.9DL-1.5EQLY 26. 0.9DL+1.5EQLY

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4. RESULT & DISCUSSION

4.1 STOREY DISPLACEMENT DETAIL OF STRUCTURE

Table 4.1 STOREY DISPLACEMENT OF SYMMETRICAL STRUCTURE IN ZONE 3

Table 4.2 STOREY DISPLACEMENT OF UNSYMMETRICAL STRUCTURE IN ZONE 3

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Thevariationofdisplacementthroughouttheheightof symmetrical structure&unsymmetrical structurewithrespecttono. ofstoreysinthestructureisshowninfig(4.1).Themaximumdisplacementisfoundtobehigherinstorey8ofthestructure, insymmetricalstructurewithseismiczone3.Andalsothemaximumdisplacementisfoundtobehigherinthehigheststorey ofthestructure,inunsymmetricalstructurewithseismiczone3.

DISPLACEMENT ZONE

3

symmetrical structure unsymmetrical structure

Fig.(4.1) Table 4.3 STOREY DISPLACEMENT OF SYMMETRICAL STRUCTURE IN ZONE 4

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Table 4.4 STOREY DISPLACEMENT OF UNSYMMETRICAL STRUCTURE IN ZONE 4

Displacement zone 4

unsymmetrical structure symmetrical structure

Thevariationofdisplacementthroughouttheheightof symmetrical structure&unsymmetrical structurewithrespecttono. of storeys in the structure is shown in fig.(4.2). The maximum displacement is found to be higher in the storey 8 of the structure, in symmetrical structure with seismic zone 4. And also the maximum displacement is found to be higher in the higheststoreyofthestructure,inanunsymmetricalstructurewithseismiczone4. Fig.(4.2)

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4.2 STOREY DRIFT DETAIL OF STRUCTURE

Table 4.5 STOREY DRIFT OF SYMMETRICAL STRUCTURE IN ZONE 3

Table 4.6 STORY DRIFT OF UNSYMMETRICAL STRUCTURE IN ZONE 3

Thevariationofstoreydriftthroughouttheheightofsymmetricalstructure&unsymmetricalstructurewithrespecttono.of storeys in the structure shown in fig (4.3). The maximum storey drift is found to be higher in storey 1 of the structure, in symmetricalstructurewithseismiczone3.

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Storey drift zone 3

symmetrical structure unsymmetrical structure

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Table 4.8 STOREY DRIFT OF UNSYMMETRICAL STRUCTURE IN ZONE 4

Thevariationofstoreydriftthroughouttheheightofsymmetricalstructure&unsymmetrical structurewithrespecttono.of storeys in the structure shown in fig (4.4). The maximum storey drift is found to be higher in storey 1 of the structure, in symmetricalstructurewithseismiczone4.

Storey drift zone 4

Storey drift mm

Fig.(4.4)

symmetrical structure unsymmetrical structure

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4.3 STOREY SHEAR DETAIL OF STRUCTURE

Table 4.9 STOREY SHEAR OF SYMMETRICAL STRUCTURE IN ZONE 3

Table 4.10 STOREY SHEAR OF UNSYMMETRICAL STRUCTURE IN ZONE 3

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Thevariationofstoryshearthroughouttheheightofsymmetricalstructure&unsymmetricalstructurewithrespecttono.of story in the structure is shown in fig (4.5). The maximum storey drift is found to be higher in story 1 of the structure, in unsymmetricalstructurewithseismiczone3.

Storey shear zone 3

symmetrical structure unsymmetrical structure

shear (kN)

Fig.(4.5)

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Table 4.12 STOREY SHEAR OF UNSYMMETRICAL STRUCTURE IN ZONE

4

Thevariationofstoreyshearthroughouttheheightofsymmetricalstructure&unsymmetricalstructurewithrespecttono.of storeys in the structure is shown in fig (4.6). The maximum storey drift is found to be higher in storey 1 of the structure, in unsymmetricalstructurewithseismiczone4.

Storey shear zone 4

shear (kN)

Fig.(4.6F)

symmetrical structure unsymmetrical structure

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4. CONCLUSIONS

Fromtheabovediscussionfollowingconclusionscanbemade. 

StoreyDisplacementofunsymmetricalstructureismoreascomparedtoasymmetricalstructure. 

StoreyDriftofunsymmetricalstructureismoreascomparedtoasymmetricalstructure 

Storeyshearofunsymmetricalstructureismoreascomparedtoasymmetricalstructure 

TheLoadDistributionintheSymmetricmodelismoreuniformascomparedtotheUnsymmetricalmodel. 

TherequirementofreinforcementismoreintheUnsymmetricalframethanthesymmetricframe. 

The Symmetric model is More Cost-Effective with respect to the Unsymmetrical model as the volume of material being usedismoreintheUnsymmetricalmodel. 

TheperformanceofaSymmetricalbuildingisbetterthananunsymmetricalbuilding.

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