Seismic coefficient of foundation for designing piles evaluated by seismic observation records and its evaluation method

It is important to estimate an appropriate lateral load acting on piles of pile foundation during earthquake. The lateral load consists of an inertial force of structure and ground deformation. This paper describes the equivalent seismic coefficient of the foundation used in the pseudo-static analysis for piles design which are evaluated rationally by using seismic observation records. The evaluated seismic coefficients of the foundation were significantly smaller than the observed maximum accelerations divided by gravity accelerations. The reasonable evaluation method of the seismic coefficient was proposed considering the phase difference between oscillation of the superstructure and the foundation.