Multi‐objective risk‐informed design of floor isolation systems

Abstract

SUMMARYThe design of floor isolation systems (FISs) for the protection of acceleration sensitive contents is examined considering multiple objectives, all quantified in terms of the probabilistic system performance. The competing objectives considered correspond to (i) maximization of the level of protection offered to the sensitive content (acceleration reduction) and (ii) minimization of the demand for the isolator displacement capacity and, more importantly, for the appropriate clearance to avoid collisions with surrounding objects (floor displacement reduction). Both of these objectives are probabilistically characterized utilizing a versatile, simulation-based framework for quantifying seismic risk, addressing all important uncertainties related to the seismic hazard and the structural model. FIS performance is assessed through time-history analysis, allowing for all important sources of nonlinearity to be directly addressed in the design framework. The seismic hazard is described through a stochastic ground motion model. For efficiently performing the multi-objective optimization, an augmented surrogate modeling methodology is established, considering development of a single metamodel with respect to both the uncertain model parameters and the design variables for the FIS system. This surrogate model is then utilized to simultaneously support the probabilistic risk assessment and the design optimization to provide the Pareto front of dominant designs. Each of these designs establishes a different compromise between the considered risk-related objectives offering a variety of potential options to the designer. Within the illustrative example, the efficiency of the established framework is exploited to compare three different FIS implementations, whereas the impact of structural uncertainties on the optimal design is also evaluated.

Hazard‐compatible modification of stochastic ground motion models

“…The relevance of techniques that model acceleration time-series of seismic events has increased during the past decades due to the growing popularity of simulation-based probabilistic seismic risk assessment [1][2][3] and performance-based earthquake engineering. [4][5][6] Though the most popular methodology for performing this task is the selection of real (ie, recorded from past events) ground motions, [7][8][9][10] potentially scaled based on a target intensity measure (IM), an alternative philosophy is the use of simulated ground motions.…”

Analysis and optimization of a nonlinear dual‐mode floor isolation system subjected to earthquake excitations

“…The FIS, which is modeled as a nonlinear SDOF system attached initially to the second level, is taken to have a natural period of 3 s and damping ratio of 40% in the linear regime (). These values were selected to give a low probability of failure () for a threshold acceleration of [ 16,17,54 ] in the linear range. As previously noted, the impact parameters ( and ) and the gap () serve as the design variables and are varied in order to investigate their effects on the performance of the PS–FIS system.…”

Life‐cycle cost optimization of wind‐excited tall buildings using surrogate models

“…Gidaris et al . [ 32 ] tailored an optimization framework based on the Kriging surrogate to the design of a floor isolation system for buildings subjected to seismic loads. Micheli et al .…”

“…In their work, fragility functions parameters were estimated using the Kriging model and considering uncertainties in structural parameters and ground motion characteristics. Gidaris et al [32] tailored an optimization framework based on the Kriging surrogate to the design of a floor isolation system for buildings subjected to seismic loads. Micheli et al [33] evaluated the use of a radial basis function (RBF) metamodel for the riskassessment of a 39-story building equipped with damping devices.…”