Experimental Assessment of the Seismic Response of a Base-Isolated Building Through a Hybrid Simulation Technique

Abstract

Base-isolated structural systems have been more and more investigated through both numerical and experimental campaigns, in order to evaluate their effective advantages, in terms of vulnerability reduction. Thanks to the lateral response of proper isolation devices, large displacement demands can be accommodated, and the overall energy of the seismic event can be dissipated, by means of hysteretic behaviors. Among the common typologies of isolators, curved surface slider devices represent a special technologic solution, with potentially high dissipative capacities, provided by innovative sliding materials. On the other hand, the overall behavior is highly non-linear, and a number of research works have been developed, aiming at the definition of the most comprehensive analytical model of such devices. The most realistic response of a base-isolated structure could be returned by a shake table test of a full-scale building. However, dimensions of the available shake tables do not allow consideration of the common load conditions, to which the isolation devices are subjected, and consequently, scaled specimens are needed, and unrealistic responses could be found. Hybrid simulations seem to solve such an issue, by accounting for an experimental substructuring, represented by a physical device tested in a testing equipment, and a numerical substructuring, consisting of a numerical model of the superstructure. Thus, a much more realistic response of the full-scale structure can be computed. In this work, the outcomes of a number of hybrid simulations have been deeply analyzed and compared to a similar numerical model. Proper non-linear constitutive laws for isolation devices have been adopted, in order to evaluate the effectiveness of design and assessment procedures, commonly adopted in real-practice applications.

Investigation of the Response Variability of Base-A Isolated Building Equipped With Lead Rubber Bearings

“…The considered base-isolated structure has been considered as an equivalent multi degree of freedom (MDOF) oscillator [1], with statically condensed stiffness matrix. Such a stiffness matrix is able to reproduce the actual dynamic properties of the system, and approximately same results of a full time history analysis on a 3D FEM model can be obtained ( [6]). Thus, the dynamic system can be expressed as follows: No additional viscous damping matrix has been accounted for, since the non-linear hysteretic behavior of the isolation system already provides hysteretic damping, in order not to underestimate the structural response.…”

“…Isolation devices are represented by a combination of Lead Rubber Bearings and Flat Sliders. Since a large number of analyses have to be performed, the overall system has been reduced to a Multi Degree of Freedom oscillator, by applying a static condensation procedure to the full 3D FEM model of the structure ( [1], [6]). The returned stiffness matrix is a full matrix, with non-null components: this result is a direct consequence of the adopted static condensation procedure, which allows to account for the actual flexural behavior in the out-of-plane direction for beams, together with torsional behavior of each floor.…”

Modeling Strategies for the Lateral Response of Curved Surface Slider Devices Under Extreme Displacement Demands

“…The case study structure has been numerically modeled as an equivalent Multi Degree of Freedom oscillator, thanks to a special static condensation procedure, which has been applied to the full 3D FEM model of the structure ( [9]). In Table 1 the resulting mass and stiffness matrices are reported.…”

Real-Time Hybrid Simulation Analysis of Moat Impacts in a Base-Isolated Structure

“…This energy dissipation has been the focus of prior work using RTHS to analyze base isolation. Studies have focused on the use of smart energy dissipation devices in conjunction with isolation mechanisms (Lin et al, 2004;Chen et al, 2014;Asai et al, 2015), mid-story isolation techniques (Keivan et al, 2017;Zhang et al, 2017), and examination of the nonlinear characteristics of the base-isolation layer (Furinghetti et al, 2020). Even in the cases where added damping is used, if the relative displacement of the base isolation layer is large enough, the isolation layer may impact the foundation wall.…”