Estimation of Equivalent Stiffness of Pile Groups in Piled Raft Foundations Using Numerical Methods and Introduction of a Transfer Approach to Structural Modeling in SAFE

Estimation of Equivalent Stiffness of Pile Groups in Piled Raft Foundations Using Numerical Methods and Introduction of a Transfer Approach to Structural Modeling in SAFE

Abstract:
In the design of piled raft foundations, accurate analysis of the soil–pile–raft interaction is of particular importance, as the combined system utilizes the bearing capacity of both the raft and the piles, resulting in behavior different from isolated foundations. One of the main challenges in the practical use of such systems is the estimation of the effective stiffness of pile groups for use in structural analysis software like SAFE. Conventional approaches often neglect the actual behavior of the soil, leading to inaccurate results.While advanced geotechnical software such as PLAXIS 3D can simulate the nonlinear behavior of soil and the complex interaction between foundation components, structural software like SAFE typically lacks such capabilities and instead uses simplified spring elements to model soil behavior. Therefore, extracting the equivalent stiffness of pile groups numerically and transferring it to the structural analysis environment is essential for accurate, safe, and economical design. In this study, the behavior of pile groups in a piled raft foundation under static loading was analyzed using 3D numerical modeling in PLAXIS 3D. The equivalent stiffness values were derived considering various soil parameters and pile geometries. A practical approach was then proposed for implementing these stiffnesses in the SAFE structural model, ensuring that the actual behavior of the soil–foundation system is adequately reflected in structural analyses. The findings of this research offer a practical solution for structural engineers to incorporate precise stiffness data into foundation modeling without the need for full-scale geotechnical simulations, thereby enabling more reliable and efficient structural designs.

Keywords:Equivalent stiffness, Piled Raft Foundation, Numerical analysis, PLAXIS 3D, Structural modeling, SAFE software, Settlement, Soil–structure interaction

[1]Ph.D. Candidate in Civil Engineering, Department of Civil Engineering, Islamic Azad University, Kerman, Iran 

alimahdizadeh356@gmail.com