2024 年 10 巻 48 号 p. 1786-1791
One of the authors has been developing a new composite foundation composed of piles and soil bags. The purpose of developing this foundation is to reduce bending moment of piles and response acceleration of structures by cutting off fixed connections between piles and footings. In particular, soil bags are laid between pile heads and footings to mitigate stress concentration to particular piles, etc. The effectiveness of this method for piers has been confirmed by an in-situ loading test and numerical simulations. When the proposed method is applied to frame structures, however, the seismic response such as uplifting behavior of footings is considered to be quite different from that of piers. In this study, therefore, shake table tests in 1/20-scale gravity field were conducted on frame structures supported respectively by a conventional cast-in-place piles foundation and the proposed foundation, and their seismic response characteristics were compared. The response acceleration and displacement of the structure, strains of the columns were measured to clearly identify the differences in seismic response characteristics between the frame structures supported by the conventional cast-in-place pile foundation and the proposed foundation. The test results showed that the response acceleration of the structure and the bending moment of the columns can be reduced dramatically in the proposed method compared to those in the conventional cast-in-place pile foundation, although the residual displacement increased in the proposed method due to the structure sliding during an earthquake.
