Investigation of design alternatives for a piled raft case history

This paper extends the design philosophy for piled rafts by exploring the factors that control the design of a published case history where the piled raft was instrumented. The case history studied differs from most published case histories in that concentrated column loads, rather than average "spread" loads, were considered in the foundation design. An extensive series of backanalyses was initially carried out with this case history, in order to calibrate the numerical program adopted herein. These analyses were followed by a parametric analysis for the evaluation of different design alternatives. These alternatives adopted distinctive pile characteristics (number, location, and length), which were varied for different raft thicknesses, yielding 26 different cases for cross comparison and comparison with the "reference" case history. Each of the solutions was also assessed in terms of relative costs against the reference case, allowing the establishment of conclusions of practical interest for those involved in the design of plied raft structures.