In this paper, torsional vibration characteristics of a seismically-isolated building constructed on an inclined bearing layer are investigated based on strong motion records and microtremor measurements. In order to elucidate the generation mechanism of torsional vibration, the torsional response of the building was reproduced using a 3D-frame model of the building and a 2D-FEM model of the subsurface structure. It is found that several types of torsional vibrations were generated in different frequency ranges. The warping torsional vibration, which was generated at 6.7 Hz, was found to be affected by the phase difference of the input motions.
This paper proposes an application method of the seismic deformation method for pile top seismic isolation buildings. In this paper, the bending moments of the piles are compared with earthquake response analyses and the conventional seismic deformation method, and some problems are revealed in the conventional method. As a result of examining the causes of problems, we propose the static analytical models and an application method of the seismic deformation method for pile top seismic isolation buildings. In addition, the validity of the proposed application method is clarified by comparison with earthquake response analyses.
This paper describes the dynamic behavior of the seismically isolated building constructed on soil with inclined bedrock based on strong motion records along with an evaluation of pile stresses. Seismic motions in soil deposit overlying inclined bedrock are evaluated using 2-D FEM. Seismic response analyses are then performed using the three-dimensional frame structure. The 3-D model is validated by comparison with strong motion records. The results show that the layer depth of the inclined bedrock, the direction of the incline, and the rigidity of the bottom plate of the foundation affect the displacement distribution and stress distribution in the piles.
The dynamic behavior of a super high-rise RC building was examined focusing on flexural deformation based on strong motion and microtremor records and seismic response analysis of a three-dimensional model. Using strong motion data, the flexural and shear deformation variations with nonlinear behavior of the building were investigated before and after the 2011 Tohoku Earthquake. The normalized top rotational angle tends to decrease as top drift becomes larger because shear deformation caused by crack and yielding of RC members increase. Microtremor measurements including plural points at the rooftop reveal the detailed distribution of vertical displacement regarding the flexural deformation.
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