THE ROLE OF NON-LINEARITY IN THE SEISMIC ASSESSMENT OF A BASE ISOLATED BENCHMARK BUILDING WITH SOIL STRUCTURE INTERACTION EFFECTS

摘要

Advanced 3D numerical simulations of a soil-structure systems aim to assess nonlinear behaviors of soil and structure and ultimately to describe realistic scenarios. The paper purpose is to simulate the effects of Soil Structure Interaction (SSI) on an ordinary base-isolated shear type building (BI), driving the assessment of the isolators by evaluating both their linear and non-linear behaviour. Non-linearity is also considered in the description of the soil which is modelled with hysteretic materials and advanced plasticity models that enable to reproduce soil hysteretic elasto-plastic shear response (including permanent deformations) and damping foundation impedances. Credited non-linear theories are applied in order to take into account appropriate flow rules as to reproduce the observed strong dilation tendency and resulting increase in cyclic shear stiffness and strength. The paper applies the open-source computational interface OpenSeesPL, implemented within the FE code OpenSees. The interface performs the 3D spatial soil domain, boundary conditions and input seismic excitation definition with convenient post-processing and graphical visualization of analysis results including deformed ground response time histories. Reproduce wave propagation adopting realistic boundaries is of crucial importance and significance in order to realistically reproduce SSI effects. The ultimate goal of the paper is the assessment of cases where BI becomes detrimental with particular attention to the structural performance by considering accelerations and displacements at various heights.