CQC MODAL COMBINATION RULE FOR HIGH-FREQUENCY MODES

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.