Effects of vertical ground motion on seismic performance verification system of RC underground structures. Discussion on response of RC structures embedded in horizontally layered ground

The objective of this study is how to estimate vertical ground motion on the seismic performance verification method for crucial civil engineering structures in nuclear power plants. This paper presents the numerical study about the effects of vertical ground motion on underground RC structures. Several soil-structure interaction models embedded in horizontally layered ground were prepared, and the nonlinear earthquake response of the models were discussed under observed earthquake ground motion. Based on the numerical results, the findings are summarized as follows: Horizontal component of earthquake load is hardly affected by vertical ground motion, then the deformation angle, section force (bending moment and shear force) and curvature in RC member cause by global shear deformation on structure almost coincide with them developed by horizontal ground motion. On the other hand, the vertical ground motion brings a slight increase of axial force on upward columns, however that has little effect on limit deformation angle and shear strength of RC member which are affected by axial force fluctuation. And response and limit state values on structure are almost stable regardless of time instant difference of the peak acceleration between horizontal and vertical ground motions. (author)