Post-seismic investigations repeatedly indicate that structures having frequencies close to foundation soil frequencies exhibit significantly heavier damages (Caracas 1967; Mexico 1985; Pujili, Ecuador 1996; L'Aquila 2009).
It is clear that with increasing the shearing layer elastic coefficient of the foundation, the frequency parameters increase to some limit values and for the large values of shearing layer elastic coefficient, the frequency parameters become independent of it.
Furthermore, the efficiency of the isolation measures designed using fixed base conditions is decreased by considering SSI over a certain relative rigidity range that is quantified using the structure to soil-foundation natural frequency ratio.
Since, impedance functions are dependent on soil properties, geometry of foundation and excitation frequency, they are suitable in the stochastic response analysis considering SSI in frequency domain.
Moreover, the force transmissibility from the vibrating mass to the foundation and the frequency equation are obtained.
We also studied the effects of essential boundary conditions, sandwich dimensions, and elastic foundation coefficients on frequency behavior of sandwich plates.
The relation between the shear modulus of elastic foundation and the frequencies of the plate is investigated.
It is found that, in addition to 9% seasonal change, the turbine-tower-foundation-soil fundamental frequency can decrease by 7% when the permafrost temperature increases from −2 °C to 0 °C.
In this paper, a semi-analytical-semi-numerical formulation has been adopted to calculate the static and dynamic stiffness of pile foundations in the frequency domain, and some approximate expressions are suggested.
In addition, from the presented numerical results one can see the influence of the small scale, magnetic field and foundation coefficients on the frequency-response curve, nonlinear frequency and instability regions for the linear and nonlinear cases.
