Abstract

Damping correction factors (dcfs) are used to adjust response spectral values corresponding to damping 5% of critical to other damping levels. Trends in the analytical response of viscously damped, linear-elastic sdof oscillators subjected to finite-duration, sinusoidal base excitations show that dcfs depend on both the frequency and duration of the ground motion, where the latter becomes significantly less influential as damping increases. These analytical trends, in conjunction with correlations relating duration and frequency content to earthquake magnitude, site- to-source distance, site classification, and tectonic setting, are used to explain/study observations in dcfs computed from a large ground-motion database for the central- eastern and western United States. For ξ ≥ 2%, the dcfs proposed by the authors depend on earthquake magnitude, site classification, and tectonic setting, all of which significantly influence the frequency content of ground motions. For ξ = 1%, the dcfs proposed by the authors additionally depend on site-to-source distance, which significantly influences the duration of ground motion. In comparison with the dcfs proposed by the authors, commonly used and recently proposed dcfs were shown to be both too low and too high, depending on the relation, period range, damping ratio, earthquake magnitude, site classification, and tectonic setting. Additionally, the dcf relations proposed in the literature for ground motions exhibiting near-fault effects should not be used for ξ < 5%, and will likely be significantly too high for periods close to that of the near-fault velocity pulse(s) for ξ ≥ 5%.

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