A frequency domain method is presented to compute the impulsive seismic response of circular surface mounted steel and concrete liquid storage tanks incorporating soil-structure interaction (SSI) for layered sites. The method introduces the concept of a near field region in close proximity to the mat foundation and a far field at distance. The near field is modeled as a region of nonlinear soil response with strain compatible shear stiffness and viscous material damping. The shear strain in a representative soil element is used as the basis for strain compatibility in the near field. In the far field, radiation damping using low strain soil response is used. Frequency dependent complex dynamic impedance functions are used in a model that incorporates horizontal displacement and rotation of the foundation. The focus of the paper is on the computation of the horizontal shear force and moment on the tank foundation to enable foundation design. Significant SSI effects are shown to occur for tanks sited on sof...

Lateral dynamic experiments were performed on small-scale pile groups at two different sites, one with stiff soil and the other with soft soil. The pile diameters and spacings were varied to create spacing to diameter (s/d) ratios of between 2.25 and 15.0. The results showed the group interaction effects to be negligible at s/d ratios greater than 12 for the stiff site, and greater than 16 for the soft site. The experiments are the first to alter both the pile diameter and the pile spacing and confirm that the spacing-to-diameter ratio is an important parameter when calculating group interaction effects. The dynamic testing was found to cause a permanent nonlinear response in the groups. A simple linear elastic theoretical analysis was then developed to predict the dynamic response of the groups. The analysis produced good estimates of the experimental results for a constant value of Young's modulus for each site. The values of Young's modulus used in the modeling were found to be typical of those for lat...