Influence analysis on displacement ratio spectra of constant yielding strength for evaluation of existing structures

In the evaluation of existing structures with known lateral strength, the displacement ratio spectra of constant yielding strength that provide inelastic displacement ratios to estimate maximum lateral inelastic displacement demands on existing structures from maximum elastic displacement demands are particularly useful. The influence of site conditions, period of vibration, level of lateral yielding strength, damping and hysteretic model et. al on displacement ratio spectra of constant yielding strength are investigated in this paper. And the special emphasis is given to influence analysis of structure damping and hysteretic model on the inelastic spectra. A statistical study are performed of inelastic displacement ratios computed for SDOF systems with different levels of lateral yielding strength normalized to strength required to retain elastic when subjected to a large number earthquake accelerations recorded in four groups of soil conditions. Different damping ratio and hysteretic model of systems are considered. It is concluded that the damping and hysteretic model effects on displacement ratio spectra of constant yielding strength are rather complex. It depends on not only site conditions but also the level of yielding strength and the natural period of structures as well. Finally, results from non-linear regression analysis are presented that provide a simplified expression to be used to approximated quantify the mentioned effects influence.