Parametric Study of G+4 Storey Structure with Vertical Geometric Irregularity Subjected to Seismic Actions

Author Name(s): Hariom Khungar, Pratik Vyas, Dr. Sharda Siddh
Author Email: khungarhp@rknec.edu

Abstract

The high rise structures are setting a trend day in and day out. Today in this era, people are fighting for building up the “tallest” high rise structure and in this fight the role of the structural design engineers comes. The scope of the paper is to understand and analyse the behaviour of high rise structures subjected to “vertical geometric irregularity”. Out of the methods prescribed by IS 1893 (Part1):2002, ESA and RSA for G+4 in all four zones with regular and irregular configurations have been taken up. To take different models in four zones was to reduce the level of inaccuracy in results. The irregularity has been adopted at all the four floors. Only linear analysis has been performed as per IS 1893. A through study has been presented and results of comparison with regular structures have been presented. For the analysis SAP2000 v14.2.4 had been used. The scope of the paper also includes the evaluation of response of structures subjected to different seismic zones having low to very severe seismic intensity.

Introduction

An earthquake is a sudden and transient motion of the earth’s surface. According to geologists, the earth has suffered earthquakes for hundreds of millions of years, even before humans came into existence. Because of the randomness, the lack of visible causes, and their power of destructiveness, ancient civilizations believed earthquakes to be supernatural phenomena – the curse of God. In terms of the geological time scale, it is only recently (the middle of seventeenth century) that an earthquake has been viewed as a natural phenomenon driven by the processes of the earth as a planet. Thus subsequent work, especially in nineteenth century, led to tremendous progress on the instrumental side for the measurement of earthquake data.[1,13] Seismological data from many earthquakes were collected and analyzed to map and understand the phenomena of earthquakes. Both seismologists and earthquake engineers use the seismological data for the understanding of an earthquake and its effects, but their aims are different. Seismologists focus their attention on the global issues of earthquakes and are more concerned with the geological aspects, including the prediction of earthquakes. Earthquake engineers, on the other hand, are concerned mainly with the local effects of earthquakes, which are capable of causing significant damage to structures. They transform seismological data into a form which is more appropriate for the prediction of damage to structures or, alternatively, the safe design of structures.

Conclusion

An attempt have been made in this paper and a G+4 storey structure in all four zones with regular and irregular configurations have been taken up. Different models in four zones were modelled to reduce the level of inaccuracy in results. Including irregularity has been adopted at all the four floors and linear analysis has been performed using SAP2000 v14.2.4 as per IS 1893 2002 (Part I).On evaluation of response of structures subjected to different seismic zones having low to very severe seismic intensity following concluding remarks can be made a) It can be seen that the base shear in X-direction is more as compared to the base shear in Ydirection as the building is more flexible in Y-direction. b) The maximum lateral displacements are observed when the irregularity was considered at bottom floors only. c) Also the maximum variation in SDR is observed as we move from the 1st floor to 2nd floor in all the four zones. d) The soft stories are subjected to the maximum bending moments and shear forces. So accordingly such soft stories must be designed for additional Shear forces and Bending moments.

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