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: 2.31). 11/1993; 22(11):943 - 956. DOI: 10.1002/eqe.4290221103


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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Available from: Yutaka Nakamura, Dec 15, 2014
    • "account issues related to angle of incidence in response spectrum based response analysis has also been tackled (see, for example, Kiureghian and Nakamura 1993, Menun and Kiureghian 1998, 2000, Lopez et al. 2000, Gonzalez et al. 2015). The study by Athanatopoulou (2005) proposes an analytical procedure to determine the critical angle of incidence in terms of response of the structure to two specific loading cases. "
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    • "It follows that to date it is not possible to predict a priori the number of modes necessary for an accurate evaluation of the stochastic response. Moreover, the most efficient approach in the stochastic seismic analysis of large structural systems via modal analysis is nowadays based on the utilization of modal correction methods [6] [7] [8] [9] [10]. These methods improve the response taking into account approximately the contribution of the neglected higher modes. "
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