抄録
A large number of super high-rise residential buildings have been constructed in Japan and quick damage evaluation is required after the future massive earthquake predicted in urbanized cities. In order to evaluate the general overview of nonlinear earthquake responses of super high-rise RC residential buildings, average models of nonlinear multi-degree-of-freedom system are constructed based on the structural characteristics of nonlinear earthquake response models used in the past structural design of the existing 39 buildings. By using the proposed average models, nonlinear earthquake responses of the eight super high-rise residential buildings in Kyushu Island during the 2016 Kumamoto earthquake are evaluated.
The conclusions of this study are summarized as follows:
1) The masses, linear and nonlinear springs per unit area are statistically compiled in terms of normalized height-wise distribution using the nonlinear earthquake response models. Bending shear springs used in some of the models are converted into equivalent shear springs. Modal participation factors from these models are also compared and their variation is found to be small. From above database, average models of nonlinear multi-degree-of-freedom system are proposed.
2) Proposed average models of nonlinear multi-degree-of-freedom system are validated from the nonlinear response analyses using input earthquake motions for the structural design. Structural responses using these models are consistent with recorded motions obtained at plural super high-rise residential buildings in the Tokyo Metropolitan area during the 2011 Tohoku earthquake.
3) For the nonlinear earthquake responses of the three super high-rise residential buildings in Kumamoto City, effects of the consecutive seismic input motions of the foreshock and the mainshock are investigated using strong motion records during the 2016 Kumamoto earthquake. The maximum inter-story drift angle is larger than that for only the mainshock, implying that effects of the foreshock were not ignorable.
4) Maximum floor responses and inter-story drift angles of the proposed average system models were verified in comparison with those estimated from the results of questionnaire survey for residents in these buildings, e.g., scattering of small items on tables, action difficulty, overturning of furniture and cracks in wallpaper. Height-wise distribution is consistent between nonlinear responses and detected responses from the regression based on the 2011 Tohoku earthquake.
