International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 04 Issue: 08 | Aug -2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 621 SEISMIC ANALYSIS OF MULTISTOREYED RC BUILDING DUE TO MASS IRREGULARITY BY TIME HISTORY ANALYSIS Sampath Nagod 1 , Prof. A.J.Zende 2 ¹Student of Master of Technology in Structural Engineering BLDEA’s V.P. Dr. P.G Halakatti College of Engineering and Technology, Vijayapur - Karnataka, India. ²Professor at Civil Engineering Department BLDEA’s V.P. Dr. P.G Halakatti College of Engineering and Technology, Vijayapur - Karnataka, India. ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - From earthquakes history, it can be observed that if the structures are not appropriately analyzed and constructed with necessary quality, then it may lead great damage and loss to human lives. We can see many of structures are fully or partially damaged due to earthquake. So, there is need to establish seismic responses of buildings. Seismic analysis of the structure is done to determine seismic responses by time history analysis which is one of the important techniques for structural seismic analysis especially when the evaluated structural response is non- linear in nature. To perform such an analysis, a representative earthquake time history is required for the structure being evaluated. In this present work non-linear dynamic analysis of 12 storeyed RC building having mass irregularity considering Bhuj earthquake time history is carried out using ETABS software. Then, Lead Rubber Bearing is manually designed and isolator properties are assigned to the building. Various parameters like Base shear, Time period and Storey displacement are determined for regular and mass irregular buildings with fixed base and base isolated condition and compared with each other. Key Words: Base isolation, Mass irregularity, Time history analysis, Bhuj earthquake. 1. INTRODUCTION 1.1 General All over the world, there is much need of construction of high-rise multi-storey buildings due to the urbanization and increase in population. These multi-storey structures are unsafe when they are subjected to the earthquakes. While earthquake engineering is noticeably progressed, structures failures are found wherever strong disturbances caused due to the motion of the earth. Earthquake forces are unpredictable. Environmental loads like an earthquake are harmful and last only for the small duration but cause severe damage to the structures and harm lives of people. Yearly near 1.5 crore, people lose their lives due to the earthquake that strikes the earth. The multi-storey structure generally subject to failure due to seismic forces at the location where there is a weakness. The weakness of structures is due to the presence of irregularities in stiffness, strength and mass. Earthquake code IS 1893 is used to design multi-storey buildings. But Ahmedabad during Bhuj earthquake, because of mass irregularity the buildings got severely damaged. Excess mass leads in reduction of ductility of vertical load resisting elements and increase inertia forces and thus increase the tendency towards collapse. Excess mass on upper floors has a more unfavorable effect than those at lower floors. Thus there is the necessity of designing these structures for earthquake loading so that they sustain moderate to strong earthquake forces. Multi-storey buildings and their structural members can be protected against earthquake forces by installing structural isolation devices. The technique used to avoid earthquake damage by separating the structure from the ground known as base isolation. 1.2 Base Isolation Base isolation is a technique in which during an earthquake, separating the superstructure or reducing the lateral movements of building superstructure from the movement of ground or foundation is done. The bearings of base isolation are designed in such a way that they are stiff vertically and flexible horizontally to allow for the difference in lateral movement while still supporting the superstructure. The structures with base isolation are different than that of fixed base structure, in which the connection between the superstructure and the foundation are rigid and the superstructure translation in all direction is constrained. Behavior of the building with base isolators is shown in below fig Figure 1.1: Behaviour of the building with Base Isolators