Earthquake response spectra taking account of number of response cycles

Proposed is a new definition of earthquake response spectra, which takes account of the number of response cycles N. The N th largest amplitude of absolute acceleration response of a linear oscilator with natural period T and damping ratio h , which is subjected to ground motion at its base, is defined as S A ( T , h , N ). By defining a reduction factor η( T , h , N ) as S A ( T , h , N )/S A ( T , h , 1), characteristics of η( T , h , N ) were investigated based on 394 components of strong motion records obtained in Japan. Two practical empirical formulae to assess the reduction factor η( T , h , N ) are proposed.