復元力特性の負勾配が地震応答性状に及ぼす影響

概要

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The most basic and simple model of restoring force characteristics will be a straight line model which is described by the linear expression such as Q= kX+Qo. And also, the skeleton curves in large deformation region have been idealized by such a linear expression, with negative value for spring constant k, in many studies on earthquake response analysis. This paper deals with the EQUIVALENT TWO MASS systems which can stand for any ordenary low or middle rise building. Analytical solutions for differential equation of motion are obtained by the method called MORDAL ANALYSIS in the case of negative stiffness characteristics. The divergence phenomenon of response is also discussed from several view points, and some useful conclusions are obtained. The most important results of this investigation is drawn basically from the fact that the response should be expressed by the sum of HYPERBOLIC FUNCTION and SINUSOIDAL FUNCTION in the situation of negative spring constant, which consists in negative slope of restoring force characteristics. If the hyperbolic function of velocity response consists of cosh function instead of sinh function, velocity respose will hardly come to zero even if after the sufficient time elaspes, which means that there is no or.very small possibilty for the response to be inverted. Consequently in such situation, the response will grow monotonicly up to divergence.
1981-12-01