EFFECT OF SOIL-STRUCTURE INTERAC- TION ON DYNAMIC BEHAVIOUR OF ELEVATED WATER TANKS

摘要

Effect of soil-structure interaction on dynamic behaviour of elevated water tanks is attempted to be studied. The dynamic characteristics and seismic response of two tanks, of approximately same capacity, one supported by shaft-type staging and the other by frame-type staging, are first studied with fixed base condition. Considering the effect of soil-structure interaction, the dynamic characteristics as well as seismic response of the same tanks are then evaluated and compared with the results of the previous cases. The concept of a rigid circular plate resting on a semi-infinite elastic medium is used to idealize the raft foundation system. These effects are studied for tanks resting on different types of clayey soil. The shaft-supported tank exhibits considerable increase in impulsive lateral period and seismic base shear due to the effect of soilstructure interaction. However, the change is marginal for the elevated tank supported on frame-type staging. The consideration of soil-structure interaction is also found to change the ratio of impulsive torsional and impulsive lateral periods. This ratio plays a very significant role in assessment of seismic torsional vulnerability of elevated tanks due to any accidental eccentricity, as explained in the literature.