  This study proposes a response-based parameter for strong motion duration
which is computed for structures and is the total time they are nonlinear
during an earthquake. Correlation between structural response and duration for
structures, subjected to a set of spectrum matched ground motions, is employed
to examine the efficiency of the proposed method. The spectral matching
procedure ensures that the influence of amplitude and frequency content of
motions on structural response variability is significantly removed. Four
concrete building type systems are studied and correlation coefficients of
structural response with the proposed duration definition are examined.
Comparison of the proposed method with other existing definitions, the
record-based and response-based metrics, shows about 15-20% improvement in the
correlation values.
