A. Derkiureghian et Y. Nakamura, CQC MODAL COMBINATION RULE FOR HIGH-FREQUENCY MODES, Earthquake engineering & structural dynamics, 22(11), 1993, pp. 943-956
The CQC rule for modal combination is extended to include the quasi-st
atic contribution of truncated modes and the effects of input narrow-b
andedness and cut-off frequency. A simple measure of the error in appr
oximating a high-frequency modal response by its quasi-static contribu
tion is derived. The extended rule is applicable to structures with hi
gh-frequency modes and to seismic inputs which may not be regarded as
wide band. Numerical examples demonstrate the significance of input ba
ndwidth and cut-off frequency on modal cross-correlation coefficients,
and on the error resulting from truncation of high-freqeuncy modes.