Intensity measure of ground motions based on average maximum momentary input energy to estimate nonlinear response of seismically isolated bridges

This study proposes an intensity measure of ground motions based on the average maximum momentary input energy equivalent velocity (AMIEV), computed from the linear response within the natural period band critical for evaluating the nonlinear response of seismically isolated bridges. The proposed intensity measure was assessed against 13 existing intensity measures in terms of efficiency, practicality, and proficiency. Although PGV and the maximum momentary input energy equivalent velocity at the fundamental natural period (MIEV) were more proficient than AMIEV for some structural configurations, their proficiency varied considerably across other configurations. In contrast, AMIEV showed the most stable and proficient performance for estimating the peak nonlinear responses of lead rubber bearings and reinforced concrete columns. Moreover, AMIEV remains stable and optimal despite stiffness variations owing to ageing deterioration of lead rubber bearings and changes in column height. The findings also confirm that AMIEV sufficiently estimates the peak nonlinear response both with and without ageing deterioration of lead rubber bearings.