EFFECT OF BASE SOIL STIFFNESS ON EARTHQUAKE SPONSE OF MULTISTORY BUILDING WITH SHEAR WALL

Abstract

The frame shear wall interaction is of utmost importance in frame Shear wall multistory buildings when these are subjected to earthquake motion. Herein the response of frame shear wall building considering the base soil stiffness is investigated. The influence of' two important building parameters, namely ratio of shear wall stiffness to the column stiffness and the ratio of shear wall height to the frame height, are studied under various soil conditions. The soil stiffness is varied from a rigid base to soft clay with two intermediate values. A 15 story frame shear wall building is considered for dynamic response computations. The shear wall is treated as a wide column and the effect of finite width of shear wall is considered. The building is assumed to b.e resting on isotropic horrogenous linearly elastic half space. The soil stiffness has been represented by two springs - One translational, and other rotational. The effect of embedment depth is considered in computing the soil stiffnesses. An equivalent frame model with soil springs has been framed to calculate the dynamic characteristics of the building. First three modes of vibration are considered and the square root of sum of squares combination is used to obtain total values as a combination of modal values. Variation of displacemeirts, shears in shear wall and frame and bending moments in shear wall is studied along the height for different soil conditions. The bending moment in shear wall at its base is found to be strongly dependent on the soil stiffness, and decreases sharply for softer so is.