Displacement-based design of soil-foundation-structure systems

In this paper a displacement-based design procedure is presented to rationally account for the effects of soil-foundation-structure interaction (SFSI) in the seismic design of shallow foundations. The non-linear deformations at the soil-foundation interface, such as foundation uplift, soil yield and soil-foundation shear deformation can dramatically alter the dynamic response of a building. The lack of consideration of the modifying factors of SFSI and an absence of procedures for controlling foundation and soil behaviour under seismic loads have resulted in inadequate designs for buildings sited on soft soil. A soil-foundation macro-element model was used to calibrate expressions to quantify the non-linear foundation rotational stiffness as well as the effects of foundation energy dissipation and soil-foundation shear deformation on the response of the soil-structure system. A series of concrete wall buildings were designed with the proposed design procedure and numerically assessed to validate the suitability of the design procedure. The simple hand calculation procedure presented here quantifies the modifying factors of SFSI in an intuitive and direct manner to allow engineers to design building-foundation systems with a clear understanding of their expected performance.