Development of Elastic Design Spectrum for Indian Context and Its Comparison with Other Codes

Abstract

Earthquake is one of the most destructive natural hazards that claims human lives and cause damages to almost all manmade structures. It is important to estimate seismic demand pose by an earthquake on structures in order to present damages. Seismic code of various countries provide Design Spectrum or Response Spectrum to estimate seismic demand on structures. However, for critical facilities, site specific response spectrum should be developed to estimate seismic demand more accurately. For Indian subcontinent, seismic demand is estimated as per design spectrum given in IS:1893(Part I)-2002, whose basis are unknown. In the present study, site specific response spectrum is developed using past records of earthquakes of Indian subcontinent. Earthquakes are classified to strong ground excitation based on Peak Ground Acceleration (PGA), Root Mean Square, Amplitude and Duration. A response spectrum is generated by classifying strong motion excitations to four zones, namely, North, East, West and South-East regions as per their locations. The mean and mean plus one standard deviation response spectrum for each regions are developed for acceleration, velocity and displacement quantities. A design spectrum for each region is developed from response spectrum. Appropriate amplification factors are determined from first principle. Comparison among developed design spectrum for East and North region and design spectrum specified in IS:1893 (Part-I) - 2002 is carried out through numerical example. Comparison shows that mean response spectrum yields base shear value lower than the IS based design spectrum for highest seismic zone V. However, the IS based design spectrum yields lower base shear value when compared with mean plus one standard deviation design spectrum. Comparison among developed mean response spectrum for West and South-East region shows the later yields lower base shear value as compared to IS based design spectrum while former yields higher base shear value. Apart, important provisions of seismic code of countries like Mexico, United States of America, Chile, Philippines and China are studied and compared. It is observed that United States of America and Philippines Code is based on Uniform Building Code (UBC).