Abstract
This paper discusses more quantitatively by means of various aspects on the first natural periods and damping coefficients obtained by vibration test, microtremors observations and seismic observations in actual buildings. Some of the significent aspects of the results of this paper are summarized as follows : 1) The experimental values are smaller than structural design values, the average rate of those values of SRC and S buildings are 60% and 80%, respectively. The seismic values are larger than the experimental values, the average rate of those values are about 20% against medium earthquake (70〜110 gal). 2) In the San Fernando Earthquake, the relation between the maximum acceleration on the top floor and the first natural periods (T_B) or the predominant periods (T_P) during the earthquake are obtained as follows, respectively : α_<mzx>=2.0×10^2T^<-0.45>_B…(7), α_<mzx>=2.4×10^2T^<-0.37>_B…(8) 3) The values of the predominant periods and first damping coefficients of actual buildings show a tendency to increase with the acceleration of the earthquake motion. 4) The empirical formura concerning the first natural periods of actual SRC and RC buildings are obtained as follows, respectively : SRC buildings : T(sec)=0.058N_1…(5) RC buildings : T(sec)=0.073(N+03N_0)…(6) in which N_1, N and N_0 represent number of stories of main structure part, above the G. L. and underground part, respectively.
