Effect of non-linear soil response and pile post-cracking behavior on seismically induced bending moments in fixed-head long piles

Recent studies showed that kinematic interaction is relevant for the design of large-diameter concrete piles in soft soils both in homogeneous and layered deposits. Especially, it was found that exists a range of admissible pile diameters able to resist to combined inertial and kinematic bending at the pile-head. Most of these studies assume that the soil is a linear-viscoelastic material and the pile nonlinear behavior is neglected. Here a BEM-based code, called KIN SP, is used to provide new insights about pile-soil interaction under seismic loads. The analyses are performed in the time domain and nonlinear soil response is modelled with the Ramberg-Osgood constitutive law. Moreover, a constitutive model for reinforced concrete piles has been introduced to consider the cyclic variation of the pile stiffness after the first cracking of the cross-sectional area. This paper highlights the importance of considering both soil and pile nonlinear behavior in kinematic interaction analyses.