COMPARISON OF DETERMINATION METHODS FOR RAYLEIGH DAMPING COEFFICIENTS AND EFFECTS ON SEISMIC RESPONSES OF STRUCTURES

Rayleigh damping is a common orthogonal damping model. The effects of Rayleigh damping coefficients on structural seismic response accuracies are discussed for a dome structure with 90m-diameter 15m-height. The following four methods are compared: a traditional method (TM), a least squares method (LS), a weighted least squares method based on multi-reference modes (WLS) and an optimization method based on minimizing the error of structure peak displacements (OM). The numerical results under four seismic excitations indicate that the OM is significantly more accurate than the other methods when significant contribution modes of responses are the first several natural frequencies, such as displacements. In the TM, one should take great care to select the reasonable second reference frequency. It is unreasonable to calculate the Rayleigh damping coefficients for the LS. When there are many significant contribution modes and the difference in natural frequencies of significant contribution modes for different response are great, it is impossible for Rayleigh damping to construct a damping matrix which makes the dynamic responses of the lower and higher modes accuracy at the same time. In this case, it is necessary for complex structures to construct damping matrix that damping ratios in more than two modes are equal to the accurate values.