A time-domain viscous damping model based on frequency-dependent damping ratios

This paper introduces the mathematics and procedures used in developing a t ime-dependent damping model for integration analyses of structural response . To establish the time-dependent viscous damping model, frequency-dependen t damping ratios of the structure under a series of steady-state unit impul ses corresponding to actual loads are first calculated. For simplicity, the ratios can be incorporated with the static stiffness of the structure to m odel approximately the impulse induced damping spectrum. According to the n ature of the problem, these ratios can be calculated from the theoretical i mpedance functions and experimental observations. With the computed damping spectrum, the damping coefficient in the time domain can be obtained with the Fourier transform technique. Adopting the impulse-response method, the damping can be modeled rationally through integration with changing loads. Numerical examples are presented to show the feasibility of this model whil e the transform criterion is satisfied. (C) 2000 Elsevier Science Ltd. All rights reserved.