What differentiates a 'direct' method from a 'substructure' method in Soil-Structure Interaction (SSI) analysis?

The key difference between a 'direct' method and a 'substructure' method in Soil-Structure Interaction (SSI) analysis lies in how the soil and the structure are modeled and analyzed. In a direct method, the soil and the structure are modeled together in a single finite element model. The entire soil-structure system is analyzed simultaneously, capturing the interaction effects directly. This approach requires a large computational domain to accurately represent the soil'....