Importance of Using Accurate Soil Profiles for the Estimation of Pile Kinematic Input Factors

The influence of the variability of the soil profile on the translational and rotational kinematic interaction factors of pile foundations is analyzed. Variable-with-depth profiles representative of different soil types are considered, and their results are compared to those of equivalent homogeneous soils presenting the same average shear wave velocity. The seismic response of the foundation is computed through an efficient numerical model based on the integral reciprocity theorem in elastodynamics and specific Green's functions for layered half-spaces. The assumption of the variable soil profile generally leads to a higher filtering effect of soil lateral displacements and increases the rotation of the foundation. The importance of the soil variability on the response of the supported structure is also analyzed in terms of its pseudo-spectral accelerations. The homogeneous assumption is found to be conservative for structures with low periods, while for other systems, especially those with an important contribution of the foundation rotation to the structural response, significantly higher maximum accelerations are obtained when considering the variable profile.