60 International Journal for Modern Trends in Science and Technology Nonlinear Analysis of RC Structure under Multiple Earthquakes Shesalu D. Vadeo 1 | M. V. Waghmare 2 1,2 Department of Civil Engineering, AISSMS COE, Pune-411004, Maharashtra, India To Cite this Article Shesalu D. Vadeo and M. V. Waghmare, “Nonlinear Analysis of RC Structure under Multiple Earthquakes”, International Journal for Modern Trends in Science and Technology, Vol. 05, Issue 09, September 2019, pp.-60-65. Article Info Received on 19-August-2019, Revised on 16-September-2019, Accepted on 25-September-2019, Published on 01-Octoberr-2019. Earthquakes in the past have shown that a strong mainshock is often followed by aftershocks forming mainshock-aftershock series type of ground motions or multiple earthquakes. Aftershocks could occur after days, months or even years and although they are normally smaller in magnitude, their intensity can be large with different energy content than mainshock and pose a seismic hazard after a mainshock. The general approach of seismic design of structures usually considers a single earthquake but recent studies have shown that the mainshock aftershock records and interaction between these two should be evaluated to determine the likely damage behavior and responses of structure.Due to successive shaking of the ground over a short period of time, the damages in the structure gets accumulated and the structure becomes vulnerable to collapse. To understand the behavior of structure under such repeated ground motions or multiple earthquakes, non-linear time history analysis is carried out. The present study considers a 12 storey reinforced concrete building. The building was analyzed for both linear and nonlinear time history analysis for 5-time history ground motions considering mainshock and mainshock-aftershock sequences. The material and geometric non linearities were accounted in terms of hinges and p-delta effects. It was found that the mainshock-aftershock sequence of ground motion has significant effect on the response of the structure in terms of top displacements and storey drifts. The analysis was carried out by ETABS 2016. Keywords: mainshock, aftershocks, nonlinear time history analysis, nonlinearities. Copyright © 2019 International Journal for Modern Trends in Science and Technology All rights reserved. I. INTRODUCTION Multiple earthquakes occur at many regions of the world where complex fault systems exist. These fault systems usually do not relieve all accumulated strains at once when the first rupture takes place. Therefore, high stresses form at different locations causing sequential ruptures until the fault system is completely stabilized. This leads to the occurrence of aftershocks after a large mainshock. Aftershock sequences could last from minutes to years and cause seismic hazard.For instance the earthquakes in California (Mammoth Lakes, 1980; Coalinga, 1983; Whittier Narrows, 1987; Northridge, 1994), Italy (Friuli, 1976; Irpinia, 1980; Umbria-Marche, 1997; L’Aquila, 2009), Japan (Kobe, 1995; Niigata, 2004; Tohoku, 2011) were followed by aftershocks with equal or even higher magnitudes, among others. These sequences of earthquakes lead to accumulation of stresses and damages on the structures. Due to the short interval between successive seismic events there is least possibility of repair and retrofitting of the structure. Hence, the structure ABSTRACT Available online at: http://www.ijmtst.com/vol5issue09.html International Journal for Modern Trends in Science and Technology ISSN: 2455-3778 :: Volume: 05, Issue No: 09, September 2019