Seismic risk sensitivity of structures equipped with anti-seismic devices with uncertain properties

Abstract

Damping and isolation devices are often employed to control and enhance the seismic performance of structural systems. However, the effectiveness of these devices in mitigating the seismic risk may be significantly affected by manufacturing tolerances, and systems equipped with devices whose properties deviate from the nominal ones may exhibit a performance very different than expected. The paper analyzes this problem by proposing a general framework for investigating the sensitivity of the seismic risk of structural systems with respect to system properties varying in a prescribed range. The proposed framework is based on the solution of a reliability-based optimization (RBO) problem, aimed to search for the worst combination of the uncertain anti-seismic device parameters, within the allowed range of variation, that maximizes the seismic demand hazard. A hybrid probabilistic approach is employed to speed up the reliability analyses required for evaluating the objective function at each iteration of the RBO process. This approach combines a conditional method for estimating the seismic demand at a given intensity level, with a simulation approach for representing the seismic hazard. The proposed method is applied to evaluate the influence of the variability of the properties of linear and nonlinear fluid viscous dampers on the seismic risk of a low-rise steel building. The study results show that the various response parameters considered are differently affected by the damper property and unveil the capability of the proposed approach to evaluate the potentially worst conditions that jeopardize the system reliability.

Analysis of the Influence of Viscous Dampers Properties Variability via Reliability-Based Optimization Method

“…Moreover, this work, along with some previous studies made by the authors [1,3], provide useful insights for a future revision of the reliability factors proposed by the current seismic codes, whose values could be better calibrated in order to properly account for the tolerances allowed on the devices' constitutive parameters…”

“…The influence of the uncertain parameters on the system seismic demand hazard is investigated by means of the constrained reliability-based optimization (RBO) method recently proposed in [1]. According to this approach, the objective function fObj that must be maximized is expressed as the variation of the MAF of exceedance of an EDP value d*, normalized with respect to the MAF of exceedance corresponding to the reference design values 0 ( , * ) =…”

“…In light of the aforementioned gap in the regulatory framework, and given the scarce literature available on this topic [1,10,16], the aim of this study is that of analyzing the sensitivity of the seismic risk of structural systems with respect to uncertain damper properties (including the variability of ), in order to assess the effectiveness of the tolerance criteria provided by the international seismic regulations in controlling the structural performance parameters variation.…”

“…To this aim, an innovative approach recently proposed in [1] is used to assess the seismic risk sensitive with respect to uncertain parameters for which a statistical characterization is not available [17,18]. This approach exploits a reliability-based optimization (RBO) tool, in which the optimization is carried out to search for the worst combination of the uncertain damper parameters, within the allowed range of variation, that maximize a probabilistic objective function expressing the variation of the mean annual frequency of exceedance of some relevant performance demand thresholds.…”

A Design Method for Viscous Dampers Connecting Adjacent Structures

“…The effectiveness for seismic protection purposes of such class of devices has been extensively analyzed in the past decades (Symans and Constantiou, 1998;Pekcan et al, 1999;Lin and Chopra, 2002;Christopoulos and Filiatrault, 2006;Takewaki, 2009), and specific issues have been also studied. These include the effect of the ground motion variability on the response of systems equipped with linear or non-linear viscous dampers Dall'Asta et al, 2016) and the influence of the variability of the damper properties, due to the device manufacturing process, on the seismic performance of the system (Lavan and Avishur, 2013;Dall'Asta et al, 2017;Scozzese et al, 2019).…”