宮坂 享明 大同コンクリート工業(株), 技術開発部, 技術課長(技術職)
JUNJI Kiyono Yamaguchi Univ., Faculty of Eng., Associate Professor, 工学部, 助教授 (00161597)
MIYASAKA Takaaki Daodo Kogyo Co.LTD., Head Researcher
We developed a High Ductility Aseismic Jointed (HDAJ) Pile at the first stage of this study. We performed bending tests to investigate the bending moment-deflection relationships of the pile. Then we developed nonlinear finite element analysis program which can analyze the large deformation analysis. The validity of the nonlinear FEM was conformed by simulating the experimental results. Next, we modified the original HDAJ pile (X-type) to give more ductility (Y-type).
We performed parametric study to examine the effect of splicer types (X-type, Y-type), stratum thickness, pile cap connectivity, pile tip embedment depth etc.on the spilced piles when subjected to large ground deformation caused by liquefaction. In all cases, we found that HDAJ piles were effective (Y-type is more effective than X-type) compared with ordinal pile for liquefaction-induced large lateral ground displacements. At the same time, we found that the failure mechanism of piles could be categorized into 6 patterns.
In the second stage, we performed dynamic analyzes of the HDJA piles to investigate the seismic response characteristics. The HDAJ piles are more flexible than ordinal piles, therefore, the seismic responses of HDAJ may greater than those of ordinal piles. This is the reason why we performed the seismic response analyzes. But the responses, such as the maximum acceleration, velocity and displacement, of HDAJ piles to strong earthquake motions were no more than those of ordinal piles. Besides, the maximum bending moment induced in piles were greatly reduced. This means that the HDAJ piles are also effective during strong earthquake motions.