SEISMIC TIME HISTORY ANALYSIS OF SIX STORY SHEAR BUILDING WITH NEWMARK-? METHOD AND ETABS

Chetan Chhindam, Pankaj Autade

Abstract: Analysis of a six story shear building subjected to base ground motion excitation is shown in this study. The time history records of ground motion for Bhuj earthquake is used for understanding the response of the structural system. Modal analysis is performed using transformation of coordinates so that the MDOF system is analyzed like SDOF system. The dynamic equilibrium system of modal coordinates became an Eigen value problem and solved for characteristic equation. Newmark’s Linear Acceleration Method is used as theoretical time stepping method for obtaining response of the MDOF system under base ground motion excitation. The stability condition was checked and observed that the Newmark’s method can be satisfactorily used for this study. Step by step procedure of Newmark’s ß Method is also elaborated showing equations that were used in the study to prepare computer algorithms. This study has made an attempt to compare the analytical results of theoretical time stepping method and ETABS computer software. The vibration mode shape vectors obtained from theoretical calculations are exactly matching mode shapes obtained from ETABS analysis by normalizing at top floor. The modal time periods of ETABS and theoretical calculations are in good conformity with each other. The story shear force results of theoretical analysis by Newmark’s Method and by ETABS are showing variation of 2%. Both the analyses have shown similar response pattern for floor displacement of the MDOF system under consideration with a variation of 3% for top story. Time history of top story displacement record obtained from Newmark’s Method is similar to that of ETABS response time history.

Keywords: MDOF shear building, Modal Analysis, Time history analysis, Newmark- ß method, story displacement

DOI: https://doi.org/10.15623/ijret.2018.0703009