In this paper. the dynamic response of Ruttha sand with different relative densities is studied by using equivalent linear model

The equivalent linear model is adopted in which the soil properties are strain dependent but cycle independent. The shear modulus tends to decrease as the shear strain increases, while the damping ratio tends to increase as the shear strain increases The computer program SHAKE, developed at the University of California, Berkley, is used for predicting and analyzing the problem. The study reached that the magnitude of the acceleration is increasing as the relative density is decreasing and the natural frequency of the structures that would be built on Al- Ruttba soil must ot be equal to (4 c/sec.) to avoid resonance condition