CQC modal combination rule for high‐frequency modes

Department of Civil Engineering, University of California, Berkeley, CA 94720, U.S.A.
Earthquake Engineering & Structural Dynamics (Impact Factor: 1.95). 11/1993; 22(11):943 - 956. DOI: 10.1002/eqe.4290221103

ABSTRACT The CQC rule for modal combination is extended to include the quasi-static contribution of truncated modes and the effects of input narrow-bandedness and cut-off frequency. A simple measure of the error in approximating a high-frequency modal response by its quasi-static contribution is derived. The extended rule is applicable to structures with high-frequency modes and to seismic inputs which may not be regarded as wide band. Numerical examples demonstrate the significance of input bandwidth and cut-off frequency on modal cross-correlation coefficients, and on the error resulting from truncation of high-freqeuncy modes.

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