Earthquake response of nuclear reactor building deeply embedded in soil

As for the research on earthquake response of nuclear reactor building embedded in soil, experimental and theoretical investigations has been performed on a model of size (height-3.75 meter, bottom cross section-5x5 meter, weight-173 ton) made of concrete under the financial support of Japanese government. The top of model was excited by an eccentric mass vibration that can generate maximum force of 3 ton. Earthpressures were measured at the bottom and side wall of model, and displacements were also measured at the top of model and ground surface. These tests were conducted at a field site where embedded depth was changed at 5 steps which were 0, 20, 47, 73, 100%. Using these experimental results and soil properties, we studied dynamical characteristics that included resonant frequency, radiation damping, vibrational mode, frequency response and earthpressure distribution around the model at varying embedment by lumped model, cylindrical elastic wave model and FEM models. In case of the lumped system, resonant frequency and radiation damping comparatively identified experimental results with theory at each embedded depth, but pressure distribution curves at the bottom of model must be adopted for calculation of lumped system uniform on sway and triangular on rocking motion. As for cylindrical wave theory, variance of resonant frequency was close to experiment at different levels of embedment but radiation damping was estimated smaller than experimental data in case of a deep embedment over a center of gravity of model. In case of FEM model using thin layer element, displacement on model and ground, variance of resonant frequency, radiation damping at each embedment and earthpressure distribution were identified experimental results respectively