He developed an approximate solution for the stiffness and damping of a pile group [23] and an approach to account for soil nonlinearity, slippage and lack of bond by introducing a cylindrical zone around the pile whose shear modulus and material damping are smaller than those of the free-field soil [24; 25]. [PERSON] and [PERSON] have studied the dynamic behavior of pile groups embedded in layered semi-infinite media [26] and obtained a formulation based on the soil flexibility matrix, as well as dynamic stiffness and flexibility matrices of the piles; in the same work, a parametrical study was carried out, reaching conclusion regarding the influence of different parameters on the behavior of the pile group. Later, [PERSON] and [PERSON] study the harmonic response of piles and pile groups embedded in halfspace to Rayleigh waves and obliquely incident body waves [27]. [PERSON] studied the behavior of pile foundations to vertical vibration [28; 29]. On the other side, multiple studies regarding SSI featured experimental approaches, seeking to obtain some kind of confirmation for the large number of theoretical and parametrical studies already available. [PERSON] and [PERSON] [30] evaluated the reliability of the impedance functions developed by the same author earlier [21]. [PERSON] has also conducted a couple of experimental studies with dynamic centrifuge tests with focus on the following different issues: the behavior of liquefiable sand [31], the evaluation of the beam on a nonlinear Winkler foundation model (p-y curves) for piles [32] and the performance of piles in laterally spreading ground [33]. While having a major contribution in the general structural dynamics field [34], [PERSON] has also studied the seismic soil-structure interaction effects for deep foundations, using a hybrid approach, which includes adding a near-field soil volume, modelled with finite elements, to the general SSI approach [35]. The interest in bridge structures for the study of dynamic soil-structure interaction began to rise, due to frequent use of deep foundations and the large size of the structures. [PERSON] and [PERSON] studied the effects a strong earthquake might have on the San Francisco-Oakland Bay Bridge East Crossing [36]. [PERSON] and [PERSON] applied the hybrid method for evaluating the soil-structure interaction effects on a bridge structure and even correlated the proposed methodology with the observed dynamic response of a laterally loaded, forced-vibration field test on a full-scale single-pile foundation [37]. Through its California Strong Motion Instrumentation Program (CSMIP), the transportation authority (California Department of Transportation, CALTRANS) managed to instrument multiple bridges across the state, thus obtaining, over the course of multiple years, actual strong motion recordings of real structures. This was a unique opportunity to the engineering community, who had the chance to verify and calibrate their models to real-life recordings of major events. [PERSON] studied the soil-structure interaction effects for a bridge foundation on piles with a substructure approach in the time domain and validated the proposed approach to recordings from two of the instrumented bridges [38; 39]. A state-of-the-art approach in the engineering field is the probabilistic approach. It offers a way to include all types of uncertainties in the analysis and assess their implications and influence over the whole problem [40]. Even though the probabilistic approach is not that new, with studies going back as far as 40-50 years ago [41; 42; 43], it started gaining more attention in recent years, due to the wide-scale availability of continually increasing computational power. It should be noted that, starting in 2016, probabilistic methods were introduced in practice for the seismic design of NPP structures, being included and recommended by the ASCE 4-16 standard for the seismic analysis of NPP structures.