Comparative seismic analysis study of G+ 20 story building with flat slab and conventional slab using ETABS

Abstract

In the study, three dimensional analytical models of G+20 story buildings have been generated and analysed using CSI ETABS software version 2016. The earthquake zone III in India is considered for buildings during analysis. Here, the analysis and design is done of G+20 story building with flat slab(with drops) and conventional slab system. In earthquake zone the displacement and drift of the structures will be more so to have more stiffness to the structure shear wall is to be provided therefore a study is made by comparing between conventional slab & flat slab (with drops) building. Comparison of various parameters like story drift, story displacement, story stiffness and time period is done. The equivalent static method is used to design and analyze the structures, as categorized by Indian Standard Code for earthquake resistant structures. The study shows that story drift is 10% more in conventional slab as compared to flat slab; story displacements is observed linearly increasing with height of the building and is 11% more in conventional slab as compared to flat slab .

Introduction

I. INTRODUCTION

About 65% of portion of India is susceptible to damaging the structure levels of seismic hazards. The structure which do not withstand the seismic pressure might endure extensive damages, break or even collapse. In this study, the structural analysis of G+20 storyed reinforced concrete frame building with flat slab(with drops)  and conventional slab system is done with the help of ETABS software. To cope with the situation maximum utilization of space vertically calls for construction of multi-storey building (High rise building) in large number is taken place. In high rise buildings lateral loads like wind loads, earthquake loads and blast forces are attaining importance and every designer is facing with the problems of providing stability and adequate strength against lateral loads. Therefore, it is very important for the structure to have sufficient strength against vertical loads together with adequate stiffness to resist lateral forces. A flat slab could be a reinforced concrete slab supported directly by concrete column without usage of beam.

In the present paper, an attempt is made to study and compare the effects of earthquake on a multi storied building comparing between conventional slab & flat slab (with drops) building for various parameters such as story drift,  story displacement, story stiffness and time period. Analysis is been carried out as per the IS 1893:2002[6], IS 456:2000[9] and using ETABS v2016 software.

A Analysis And Design Of Flat Slab By Using Etabs Software by B.Anjaneyulu et.al.is done using ETABS software. In this paper it is found that Flat plate/slab construction is a developing technology in india flat slabs has manyadvantages over conventional slabs and hence it can be a very good option for modern constructions.[1]

A Comparative Study of Seismic Analysis Between Conventional and Flat Slab with Drop and without Drop Framed Structures with Different Masonary Infills by M Vinod Kumar Reddy et.al.is done using ETABS software. In this paper it is found that Base shear of the conventional framed structures are having more than Flat slab with drop and without drop framed structures.[2] 

Use of flat slabs in multi-storey commercial building by A.C.Thakur et.al.. In this paper it is concluded that The reduction in time period in Flat slab without drop, Flat Slab with Drop with opening and Flat Slab without Drop is 3%,6% and 7% as compared with Flat Slab with Drop.[3]

A Comparative Analysis of RCC and Steel-Concrete-Composite (B+G+ 11 Storey) Building is done by N.A.Mohite et.al. using ETABS software. The conclusion drawn out of this paper is that Still roof displacement and drift with earthquake in X and Y direction are less in Composite framed structure as to R.C.C. framed structure. This may be due to more ductility in case of Composite structure as compared to the R.C.C. which is best suited under the effect of lateral forces.[4]

A study on Assessment of Response Reduction Factor of Flat Slab Structures by Pushover Analysis by A.M. Balate et.al. is done using ETABS software for seismic zones II, III and IV. The conclusion drawn out of this paper is that the flat slab gives maximum bending moment at end corner as it behaves similarly to cantilever slab.[5]

II. MODELLING AND ANALYSIS OF MULTI?STOREY BUILDING

The three-dimensional reinforced concrete structure is modelled and analysed in Equivalent Static Method using CSI ETABS version 2016 software to indicate the likely maximum seismic response of the said structure.

For the present study work, G+ 20 stories with conventional slab and flat slab with drops have been modelled. Description of structure like Structure details, Material properties, section properties, and loads for conventional slab and flat slab with drops are shown in Table 1,2,3 and 4 respectively.

IV. RESULTS AND DISCUSSIONS

Following are the results of analysis. Comparison of parameters mentioned is tabulated in following tables.

A. Story Displacement

Table 5 demonstrates the maximum displacement for conventional slab building and flat slab building. The results of conventional slab building model shows that at top floor as compared with the flat slab building model produces 18mm and  16mm displacement with 11% difference.

B. Story Drift

Table 6 demonstrates the maximum story drift occurs at story 1 in conventional slab building with a difference of 10.63% as compared to flat slab building.

C. Story Stiffness

Table 7 demonstrates the story stiffness . Story stiffness is more for Flat Slab Building as compared to Conventional Slab building.

D. Time Period

Time period for conventional slab model is 2.535sec.and 2.406 sec. for flat slab model which is 5.36 % more than flat slab model.

Conclusion

A. The maximum story drift is 10% more in conventional slab model as compared to flat slab. B. The story displacement increases linearly and the results of conventional slab building model shows that at top floor as compared with the flat slab building model produces 18mm and 16mm displacement with 11% difference. . C. The story stiffness is less in conventional slab building model as compared to flat slab building model. D. The time period in conventional slab building model structure is 1.05times more than the flat slab building model.

References

[1] B.Anjaneyulu, K Jaya Prakash : “Analysis And Design Of Flat Slab By Using Etabs Software” , International Journal of Science Engineering and Advance Technology, IJSEAT, Vol. 4, Issue 2, February 2016. [2] M V. K. Reddy , Dr. V. G. Ghorpade:” Comparitive Study of Seismic Analysis Between Conventional and Flat Slab with Drop and without Drop Framed Structures with Different Masonary Infills”, International Journal of Engineering Research & Technology (IJERT) Vol. 3 Issue 10, October- 2014. [3] A. C. Thakur, R. John:” Use Of Flat Slabs In Multi-Storey Commercial Building ”, International Journal of Engineering Applied Sciences and Technology, Vol. 4, Issue 3, July 2019. [4] Mr. Nitish A. Mohite, Mr. P.K.Joshi, Dr. W. N. Deulkar:” Comparative Analysis of RCC and Steel-Concrete-Composite (B+G+ 11 Storey) Building”, IJSRP Volume 5, Issue 10, October 2015 edition. [5] Ajinkya M. Balate, H. R. Magar Patil:” Assessment of Response Reduction Factor of Flat Slab Structures by Pushover Analysis”, International Journal of Engineering and Advanced Technology (IJEAT), Volume-9 Issue-6, August 2020 [6] IS 1893 (Part – I):2002 – “Criteria for Earthquake Resistant Design of Structures” – Bureau of Indian Standards, New Delhi, India. [7] IS-875 (Part 1):1987 – “Dead Loads on Buildings and Structures” – Bureau of Indian Standards, New Delhi, India. [8] IS-875 (Part 2):1987 – “Live Loads on Buildings and Structures” – Bureau of Indian Standards, New Delhi, India. [9] IS-456:2000 – “Plain and Reinforced Concrete – Code of Practice” - Bureau of Indian Standards, New Delhi, India.

Copyright

Copyright © 2022 Mr. Nitish A. Mohite, Mr. Mayur M. More, Mr. Vidyanand S. Kadam, Mr. Satish S. Kotwal, Mr. Vinayak B. Patil. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.