A COMPARATIVE SEISMIC PERFORMANCE OF INDIAN STEEL STANDARDS

Abstract

Steel is one of the most ductile among widely used engineering materials. The main characteristic of steel to undergo large inelastic deformations before actual failure is highly desirable from seismic point of view. However 1994 Northridge, U.S.A and 1995 Kobe, Japan earthquakes severely shook this perception of immunity of steel frames to seismic event as many of the steel frames; designed for seismicity as per the latest standards available at the time, suffered brittle damages. Damages included yielding, buckling, extensive fractures to frame elements which in case of Kobe earthquake resulted in overturning of some frames also. Reasons for these failures shed a light on design related factors such as estimation of design forces, presence of triaxial stress condition, provisions for failure hierarchy etc. In recent years; India is observing a growth in steel structures especially in metropolitan cities. Thus it is prudent to have a closer look on current seismic design provisions in Indian steel standards. The present study investigates the seismic potentialities of steel frame structure designed by different standards namely BS EN 1998-1-2004, IS 800-1984 and the latest IS 800-2007 through Pushover analysis and Non Linear Time History analysis. For this, first of all an overview of reasons of failure and seismic design provisions in European and in Indian standards is presented. A typical frame structure is designed with above mentioned standards and subjecting each codified frame to Pushover analysis (non linear static analysis) and Non Linear Time History analysis individual and comparison of performance is provided. Finally the results are reviewed with respect to latest Indian standards. It seems that latest Indian standards (IS 800-2007) caters for identified seismic design factors effectively and is more explicit for failure hierarchy, connection details and panel zone buckling thus offering superior performance in ductility criteria but a middling performance in strength criteria.