www.ijird.com August, 2014 Vol 3 Issue 8 INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH & DEVELOPMENT Page 78 Pushover Analysis of Complex Steel Frame with Bracing Using Etabs 1. Introduction Seismic Analysis is a subset of structural analysis and is the calculation of the response of a structure to earthquakes. Nowadays High Rise Steel frame building is well establishing in metro cities. For construction of high rise building bracing are constructed for stiffness and lateral load resistance purpose. Steel frame usually refers to a building technique with a “skeleton frame” of vertical steel columns and horizontal I-beams, constructed in a rectangular grid to support the floors, roof and walls of a building which are all attached to the frame. The development of this technique made the construction of the skyscraper possible. Bracings are strong in compression. Bracing with their surrounding frames has to be considered for increase in lateral load resisting capacity of structure. When bracings are placed in Steel frame it behaves as diagonal compression strut and transmits compression force to another joint. Variations in the column stiffness can influence the mode of failure and lateral stiffness of the bracing. 2. Description of the Building For the analysis work, seven models of steel frame building of 15 floors are made to know the realistic behaviour of building during earthquake. The length of the building is 84m and varying width from 12 to 36m as shown in fig.2. Height of typical story is 3.5m.Building is symmetrical about X and Y-axis. Material concrete grade M25 is used, while steel Fe 250 (mild steel) is used. Beams and columns are modelled as frame element and joined node to nodes. The columns are assumed to be fixed at the ground level. Figure 1: Plan of a Complex Structure ISSN 2278 – 0211 (Online) Vaseem Inamdar Post Graduate Student, Structural Engineering Department Civil Engineering, East West Institute of technology, Bangalore, India Arun Kumar Assistant Professor of Civil Engineering Department East West Institute of Technology, Bangalore, India Abstract: Steel bracing is economical, easy to erect, occupies less space and has flexibility to design for meeting the required strength and stiffness. In the present study, pushover analysis of complex steel frame building was investigated. These investigations were based on stiffness and ductility. This paper is intended to compare the performance of structure by using ISMB and ISNB(hollow pipes) steel sections as bracing element on 15-story complex steel frame. Displacement analyses were performed using the Extended 3D Analysis of Building Systems (ETABS) software for investigating stiffness of these system and pushover analysis were performed. The results of these outputs indicated that performance of structure greatly influenced by the way and sections adopted for bracing system. Keywords: Complex steel structure, Pushover analysis, ISNB (hollow pipes) sections, pushover curve, performance point