耐震極限設計におけるモーダル・アナリシスの適用性について

Abstract

The energy input due to earthquake depends only on the total mass and the fundamental natural piriod of malti storied shear systems whether it is the elastic system or not. Distribution of optimum yield-shear force coefficients, which makes cumulative inelastic deformation ratio of each story of multi-storied shear systems nearly equal, is equivalent to distribution of shear force coefficients of elastic systems. In the Building Standard Code of Japan, the criterion of safety of building against the strong earthquake is described by following formulas. Q'_<un>≧Ds・F_<es>・Q_<ud> Q_<ud>=C_0,・Z・R_t・A_i・W_i, C_0≧1.0 where Q_<un>' : yield shear force of each story of a building. D_s : a value pertaining to damping characteristics and ductility. F_<es> : a value pertaining to eccentricity-ratio and rigidity-ratio. Q_<ud>' : shear force in each story of a building calculated on the assumption that the building remains elastic. Z : seismicity index. R_t : shape function of acceleration response spectra. A_t : distribution function of shear force coefficients. W_i : total weight resting on the story. It is important to verify whether it is possible to adopt the shear force response of elastic systems instead of Q_<ud> in general systems including flexural system. If it's possible to do so, we can replace C_0・R_i・A_i with shear force coefficient by the model analysis. In this paper, we examine the effectiveness of the model analysis to obtain Q_<ud> for general systems including flexural system. The essential matter which must be examined is summarized as follows : 1. The total energy input into inelastic systems can be estimated by the modal analysis. 2. Distribution of optimum yield-shear force coefficient can be estimated by the modal analysis.