In recent years, researchers have taken advantage of the nonlinear characteristics of the underlying soil to mitigate the excessive seismic force demands on the superstructure under earthquake excitation. For this purpose, the conventionally designed foundation can be replaced with rocking foundation. This is achieved by under proportioning the shallow foundation. Although the mechanism of rocking foundations has been well documented, there remains a gap in developing a methodology for reduction of foundation sizes in multi storey Reinforced Concrete (RC) shear wall framed structure. Therefore, this study focuses on the seismic responses of a shallow foundations supporting a multistorey RC shear wall framed structure. The foundation for RC shear wall is proportioned by gradually reducing the earthquake load considered for the foundations to enhance the increased rocking effect and to mitigate seismic force demands. Thereafter, key parameters responsible for seismic behavior of sub-structure are being compared with conventionally designed foundation with increasing foundation rocking, by varying type of underlying soil and with increasing height. Seismic behavior obtained by implementing a series of nonlinear time history analyses indicates that the foundation rocking greatly influences the dynamic properties. With increasing degree of foundation rocking, natural fundamental period of the overall structure gets lengthened, with decreasing peak roof acceleration, thereby mitigating the peak base moment and base shear experienced at the shear wall compared to conventionally designed foundation. On the other hand, it is observed that there is an increase in roof displacement and shear wall settlement at the foundation level. It is found that the foundation of shear wall can be designed by considering 40%, 60% of earthquake loads for zone V and zone II structural designs, respectively without encountering excessive settlements. From the sensitivity analysis it is highlighted that the foundation size and design seismicity impact the base shear contribution ratios between shear wall and column members, fundamental natural period and foundation settlement.

Resonance occurs when the natural frequency of an offshore wind turbine matches its rotational or blade passing frequency, potentially causing severe structural damage. Existing research on the resonance frequency characteristics of offshore wind turbines has mainly focused on elastic analysis, neglecting the nonlinear dynamic interaction between the foundation and soil. Based on the dynamic Winkler foundation model, the hyperbolic soil resistance around the pile-lateral displacement (p-y) backbone curve was used to consider the stiffness nonlinear of the pile-soil system. The shear strain-dependence of hysteretic damping was considered for soil energy dissipation. A simplified nonlinear frequency domain analysis method for calculating the resonance frequency of monopile-supported offshore wind turbines was proposed. The validity of the method was confirmed through comparisons with model test results and field measurements from the Lely (A2) offshore wind turbine. A parametric study was conducted to investigate the influence of sand density, pile length and pile diameter on the nonlinear resonance frequency of offshore wind turbines. The results show that the resonance frequency of the offshore wind turbine system decreases with increasing loading amplitude. Additionally, the influence of soil nonlinearity on the resonance frequency for systems is more obvious when the sand is looser, the pile length is shorter, or the pile diameter is smaller.