抄録
Recently, the researches on the filtering effect of rigid foundation slab have become active in United States of America, keeping the development of a rational design method for nuclear power plants in mind. One of the authors presented this effect in 1969 using the observed earthquake records. In order to authorize the theory, this paper tried a proof of the filtering effect of foundation slab using two earthquake records at Hachinohe Technical College Bldg. during the after-shock of Tokachioki earthquake in 1968 and at Hollywood Storage Bldg. during San Fernando earthquake in 1971. The effective input motions to the building foundation were computed from the free field motions by passing through the numerical filter that represents the filtering effect of foundation slab. The foundation motions thus theoretically obtained were compared with the observed records at building foundation that obtained simultaneously with free field motions. The both were proved to be very similar to each other. It is well known that the earthquake response of structure is much or less influenced by the soil-structure interaction effect. However, the filtering effect should be distinguished from the soil-structure interaction effect. To make sure of the above, the building was represented by the mathematical model including foundation soil, and the transfer function of free field motion to the foundation response was presented. The transfer function thus theoretically obtained was proved not to be similar to that obtained from observed record. It was found that the transfer function in which the filtering effect and soil-structure interaction were taken into consideration gives the best similar tendency toward that obtained from observed record. In order to substantiate this effect for the design application, it is hoped that the additional research to make clear the general characteristics of this effect is promoted on the basis of several kinds of earthquake observation.
