Energy-period-ductility relationships in single degree -of- freedom systems subjected to ground motion

ABSTRACT This study is intended to determine the energy-period-ductility relationships for an inelastic single-degree-of-freedom (SDOF) system subjected to an earthquake ground motion (EQGM). The SDOF system is subjected to seven different EQGMs having different characteristics such as frequency content, magnitude, peak ground acceleration, strong motion duration, predominant ground motion period and different soil conditions. Non-linear time history analysises are carried out to determine the energy demands for SDOF systems. First, the nature of the earthquake problem and the problems encountered in earthquake resistant design (EQ-RD) are briefly discussed and then energy based EQ-RD philosophy is introduced. The response analysises are carried out for a SDOF system subjected to an ensemble of ground motions in an attempt to establish a simple relation between the energy response parameters and structural response. In this study, three different strength indices and five different target displacement ductility values are selected. The SDOF systems with different periods from 0.1 sec to 3.0 sec at 0.1 sec increments are investigated. The results are presented for all EQGMs for the following response measures; hysteretic energy, energy input and scaled peak ground acceleration. Furthermore, an energy spectrum is also obtained by using equivalence velocity concept. Analysis results are determined by using DRAIN-2DX computer program. Keywords: Energy demand, hysteretic energy, ductility, ground motion, SDOF systems. xiv