Soil–Structure Interaction and Structural Design of Raft-Foundation and Reinforced Concrete Superstructure

Raft foundations can be analyzed using the conventional, Winkler, and continuum methods. In the conventional method, it is assumed that the raft is rigid and settles uniformly. In the Winkler method, commonly employed in structural analysis software packages, soil is represented by a series of springs. On the other hand, in computer-aided continuum analysis, soil below the raft is modeled using solid elements available in finite element–based software. In the present study, analyses of the raft as a single unit and the raft together with the superstructure as a combined unit are carried out separately for a wide range of soil strength parameters employing the Winkler and continuum methods. The results of the analyses and subsequent designs were compared for different models. The variations in the quantity of reinforcement required for the raft and superstructure, corresponding to changes in soil stiffness values in different modeling methods, are investigated. Useful recommendations are presented to increase the effectiveness of Winkler model for structural design. The need for modeling the raft and superstructure as a combined unit is also highlighted.