Damping properties of high-rise steel buildings are investigated, based on vibration tests and earthquake observations. First, damping in micro-amplitude is examined by statistical analyses of vibration test data. In the first mode, relationship between damping factor h_1 (%) and natural frequency f_1, (Hz) is obtained as h_1, = 1. 84f^^2__1 + 0. 39, and n-th mode damping factor h_n (%) is obtained as h_n = 1. 2^<n-1>・h_1. Second, damping in large-amplitude is examined by identification technique to earthquake observation data. Compared with micro-amplitude, level, natural period and damping factor become larger, and 2 〜 3 % value is given for the first mode damping factor. Finally, damping in vertical vibration is examined from earthquake observation data.
