Nonlinear seismic response of stiffening SDOF systems

Abstract

Stiffening behavior can result from interaction between a structure (base system) and its surrounding environment as in the bridge soil-structure interaction. In this paper the base single-degree-of-freedom (B-SDOF) systems are designed for several ductility factors and then the effects of different interacting environments (defined in terms of stiffness, strength and gap size) on its dynamic response are investigated. For this, nonlinear time history analyses are performed using an earthquake record scaled to an elastic design response spectrum at each period. Several damage criteria, namely, displacement ductility, dissipated hysteretic energy, and low-cycle fatigue concepts are considered. On average the displacement ductility is lower for stiffening systems, consistent with push-over analysis based on seismic codes. However, it is shown that considering other seismic damage criteria than displacement ductility, it is quite likely that a stiffening single-degree-of-freedom (S-SDOF) system (i.e., a base system with an interacting environment) will sustain more damage than an elastic-plastic B-SDOF system (i.e., a base system alone). Design implications and the needs for future research are also discussed.