EFFECTS OF SIMULTANEOUS ACTION OF HORIZONTAL AND VERTICAL GROUND MOTION ON UPLIFT OF ISOLATOR OF BASE ISOLATED HIGH-RISE APARTMENT HOUSES

摘要

Since the Hyogoken-nanbu earthquake, a large number of base isolated high-rise apartment houses hae been built in Japan. In any seismic design of such base isolated buildings of large aspect ratio, full attention should be paid with respect to the possible uplift of an isolator. It this paper, the authors, making use of strong ground mon data in Japan and abroad for input, and making analysis of earthquake respons based on a simultaneous input of both horizontal and vertical accelerograms, prpose to show records of strong ground motion that had the effects of uplift on isolatiors, and to point out ground motion characteristics of fluctuation of preses on isolators. The analysis by the authors indicates that any strong ground moion with uplifting effects takes place when both horizontal and vertical components strike it simultaneously or with a time lag of several seconds. Uplifting efts on an isolator are also observed in no small number of cases where a base isolated building is struck by either horizontal or vertical component of strong ground motion.