Displacement-based Seismic Design of Building using Elastic Response Spectra

Abstract

The traditional earthquake resistant design is quantified by obtaining ductility demands based on calculated force demand-capacity ratio. These approaches completely miss an important parameter, structural displacement, which is a measure of damage in structures subjected to earthquake excitations. A codal based spectral acceleration procedure has following deficiencies - (1) The initial stiffness is used to estimate the time period of the structure, (2) Seismic code use empirical expressions for the time period, T, (3) Response reduction factor (R), is appear to be arbitrary and are difficult to justify. Therefore, recently a design procedure known as Displacement-based Design (DBD) has been developed with the aim of removing the deficiencies of widely used codal based spectral acceleration provisions. This method is based on displacement, since it is basic quantity and can be easily obtained. . DBD defines the structure under consideration by a single-degree-of-freedom (SDOF) representation and consider its performance at peak displacement response, instead of its initial elastic characteristics. This is realized by Substitute Structure Approach. In the present paper, the spectral acceleration based method given in IS 1893 (Part 1): 2002 is reviewed and its limitations are discussed. DBD is implemented for SDOF system using elastic design spectra. The major focus of the paper is to compare DBD method with codal based spectral acceleration based method prescribed in IS 1893 (Part 1): 2002.