Optimum Design of Resilient Sliding Isolation System for Seismic Protection of Equipments

Abstract

Seismic isolation is one of the effective methods to protect equipments. It helps to keep seismic response accelerations in equipment below its allowable limits. Among different types of isolation systems, the combination of restoring spring and slider, also called as resilient sliding isolation (RSI) system, is the one which has been effectively used for protection of equipment. Principal design parameters for this type of isolation system are period of system (stiffness of spring) and friction coefficient of slider. There may be number of combinations of these design parameters which can enable the isolated equipment to remain functional during and after the predicted seismic event. The optimum design of RSI system can be considered as the one which maintains the response acceleration in the equipment below its allowable limit and at the same time keeps the relative displacement between floor and the equipment to the minimum. This study deals with optimum design of resilient sliding system. First the RSI system is modeled analytically by (i) precise and (ii) simplified SDOF models. The accuracy of the model is then validated by shaking table tests. The validated simplified SDOF model is then used to determine optimum design parameters for different levels of allowable accelerations. Results show that the optimum period decreases and the optimum friction coefficient increases with higher allowable acceleration.

Optimal Friction Coefficients for Isolated Structures Depending on the Soil Condition

“…The different influence of the three soil conditions and, in particular, the increase of the statistics values of the response parameters from stiff to soft soil condition results to be consistent with the results described in [28]- [30]. The existence of an optimal value of the friction coefficient has been pointed out in many studies on systems isolated by FPS bearings [17], [21]- [24], [26] and it depends on some effects that follow an increase of the friction coefficient. In fact, an increase of the friction coefficient leads to an increase of the isolator strength (and thus of the equivalent stiffness, with a reduction of the corresponding effective fundamental vibration period (Fig.1)) and the increase of participation of higher vibration modes as well as transfer of forces towards the superstructure.…”

“…This value is influenced by the building properties and the isolation period, and it increases with the increase of the earthquake intensity. The minimization of the absolute accelerations of the isolated superstructure was employed as optimization criterion also in other works [23]- [24]. In [26], considering a tenstory shear type building as case study, a multi-objective optimization for the optimal design of sliding isolation systems for suppression of seismic responses of building structures is presented applying a genetic algorithm to minimize the building's top story displacement, its acceleration and also the base raft's displacement.…”

Reliability-based dynamical design of a singular structure for high energy physics experiments

“…The base isolation technology, [3], is in construction one of the most advanced protections against earthquakes that contain critical devices such as computer servers [4], electronic equipments [5,6], precision machinery [7], etc. According to [8], the two main challenges in the design of structures with seismic isolation are the consideration of the variability of ground motions, see [9], and the non-linear response of the isolators.…”

Protecting vibration-sensitive contents: an investigation of floor accelerations in seismically isolated buildings

“…Evidently, it is of utmost importance to design and build earthquake resistant structures in order to save lives and prevent damage in case of major earthquakes. And, equally important is the protection of the vibration-sensitive contents of hospitals, universities, air traffic control centers, industrial facilities, and technology centers which have critical functions (Ramallo et al 2002;Dolce and Cardone 2003;Veprik 2003;Iemura et al 2007;Yao and Huang 2009;Tsai et al 2010). Public may face both short-term and long-term healthcare problems in case a hospital has to stop its service due to damage to its high-tech vibration-sensitive equipment.…”