Comparison of different numerical methodologies to derive fragility curves of RC buildings with soil-structure interactions

摘要

In order to assess the physical vulnerability of buildings, the general methodology consists in deriving fragility curves, representing the probabilities of exceeding some predefined structural damage states as a function of a parameter representing the hazard levels (e.g. PGA). In general, these curves do not account for soil-structure interactions (SSI). This paper intends to quantify their influence on the dynamic response of inelastic building-foundation systems and on the resulting fragility curves. We will compare the results obtained with two different numerical methodologies, considering a combination of two different RC building typologies (low-rise/high-rise) and underlying layered soils (shear wave velocities ranging from 100 to 300 m/s): 1) A two-step analysis, in which the bed-rock response is first propagated in superficial layers using CyberQuake program. The resulting waveform is transferred at the building foundation through an empirical adjustment factor. Then, the nonlinear dynamic response of a 3D building model is computed with the finite element program SeismoStruct, with link elements to account for soil deformation patterns (rocking and sway). 2) A one-step analysis, in which the soil and building are modeled at once using the finite element software GEFDYN, considering 1D simplified building models (MDOF stick) over a 2D soil model. The fragility curves computed in this paper, compared with the ones derived from fixed base models, will permit to quantify the effects (favorable or not) of SSI with respect to various relevant parameters identified.