## 1 Background  
Structural vulnerability to earthquakes may be significantly reduced by the application of base isolation, as demonstrated since the first studies by [PERSON] [1, 2]. However, when isolation technique is applied on structures founded on deformable soil, its benefits may be reduced, as shown in [3, 4, 5, 6, 7]. Moreover, the role of Soil Structure Interaction (SSI) on base isolation has been assessed by experimental studies [8]. In this regard, SSI effects has been demonstrated [9, 10, 11] to consist of two important mechanisms: lengthening the structural periods and increasing the damping of the system. Moreover, ref. [12] analyzed the interaction between SSI and base isolation (BI) by performing numerical analyses, ref. [13] studied the multi-story buildings with and without sliders in the cases of ground shock due to tunnel explosions. [PERSON] et al. [14, 15] investigated the effect of SSI on the response of base-isolated buildings by considering equivalent fixed-base systems. In addition, ref. [16] assessed the local site conditions of the soil and their effects in the isolated structures. In addition, since the first contribution by [17], seismic resilience has been applied as a parameter to assess the seismic performance of buildings. Moreover, ref. [18] defined resilience as the capacity to reduce the consequences of events, and to recover quickly from a damaged to an operational state. More recently, the resilience-based earthquake design initiative (REDi) rating system proposed a methodology to design resilient structures based on several criteria [19]. Many applications have been developed from this framework for assessing the seismic resilience of single structural configurations [20, 21, 22]. In particular, ref. [23] proposed an integrated approach to assess the seismic resilience of acute-care facilities with fragility functions. In this background, there are still few contributions that assess the resilience of base isolated configurations. In particular, [24] proposed a methodology to assess the seismic resilience of conventional and base-isolated steel structures by considering the aspects of sustainability (economic, social and environmental). However, the assessment of the role of SSI on base isolated buildings by considering a resilience-based approach is still a hole in literature and thus the principal goal of this paper is to propose a framework that may calculate resilience of based-isolated structures founded on deformable soil. In this regard, numerical simulations are performed with Opensees, enabling to consider the mutual effects of structural properties and soil deformations. In particular, the soil is represented with non-linear hysteretic materials and advanced plasticity models as to assess the mutual effects of BI and soil non-linearity at the same time. The models have been implemented in Opensees that may reproduce soil hysteretic elasto-plastic shear response, foundation impedances, realistic boundary conditions and advanced interface between the soil and the structure. The main objective is to assess these two dynamic mechanisms by investigating the cases where BI becomes detrimental. In particular, isolated structures on rigid soil are compared with the same structural schemes on soil with decreasing deformability showing the effects on the periods and on the damping of the performed systems. In this regard, historically, ref. [25] showed that period elongation depends mainly on the so-called structure to soil stiffness ratio (depending on the height and the shear velocity of the flexible layer). Later, ref. [26] extensively investigated the formulas in ASCE 7-05 for several buildings by considering over 800 fundamental periods. Moreover, ref. [27] proposed an empirical formula for assessing the fundamental period of reinforced concrete structures by performing 3D numerical simulations of SSI effects. Additionally, ref.