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A series of reinforced concrete specimens has been subjected to static tests as well as periodic and simulated earthquake motions to develop realistic analytical models for the earthquake response of the elements and materials involved. During some of the dynamic tests the specimen responded with a displacement of the order of six times the initial yield deflection. The stiffness and energy absorbing capacity of the specimens changed considerably and, at times, very rapidly during the dynamic tests. A realistic conceptual model for predicting the dynamic response of a reinforced concrete member should be based on a static force-displacement relationship which reflects the changes in stiffness for loading and unloading as a function of the previous loading history. The dynamic response calculated on the basis of the proposed force-displacement relationship resulted in satisfactory agreement with the measured response. With the hysteresis loops defined by the proposed force-displacement relationship, it was not necessary to invoke additional sources of energy absorption for a satisfactory prediction of the dynamic response.
Takeda et al. (Tue,) studied this question.