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Ruiz R.O.,University of Santiago de Chile | Ruiz R.O.,University of Notre Dame | Taflanidis A.A.,University of Notre Dame | Lopez-Garcia D.,University of Santiago de Chile | Lopez-Garcia D.,National Research Center for Integrated Natural Disaster Management 15110017
Journal of Sound and Vibration | Year: 2016

A recently proposed new type of liquid mass damper, called Tuned Liquid Damper with Floating Roof (TLD-FR), is the focus of this paper. The TLD-FR consists of a traditional TLD (tank filled with liquid) with the addition of a floating roof. The sloshing of the liquid within the tank counteracts the motion of the primary structure it is placed on, offering the desired energy dissipation in the vibration of the latter, while the roof prevents wave breaking phenomena and introduces an essentially linear response. This creates a dynamic behavior that resembles other types of linear Tuned Mass dampers (TMDs). This investigation extends previous work of the authors to consider TLDs-FR with arbitrary tank cross-sections, whereas it additionally offers new insights on a variety of topics. In particular, the relationship between the tank geometry and the resultant vibratory characteristics is examined in detail, including the impact of the roof on these characteristics. An efficient mapping between these two is also developed, utilizing Kriging metamodeling concepts, to support the TLD-FR design. It is demonstrated that the overall behavior can be modeled through introduction of only four variables: the liquid mass, the frequency and damping ratio of the fundamental sloshing mode of the TLD-FR, and the efficiency index, which is related to the portion of the total mass that participates in this mode. Comparisons between TLDs-FR and other types of mass dampers are established through the use of the latter index. A design example is presented considering the dynamic response of a structure under stationary excitation. It is illustrated in this example that for complex tank cross-sectional geometries there exists a manifold of tank configurations leading to the same primary vibratory characteristics and therefore same efficiency of the TLD-FR. Considerations about excessive displacements of the roof can be then incorporated to indicate preference towards some of these candidate configurations. © 2016 Elsevier Ltd. Source

Ruiz R.O.,University of Santiago de Chile | Ruiz R.O.,University of Notre Dame | Lopez-Garcia D.,University of Santiago de Chile | Lopez-Garcia D.,National Research Center for Integrated Natural Disaster Management 15110017 | Taflanidis A.A.,University of Notre Dame
Acta Mechanica | Year: 2016

This paper introduces a new type of tuned liquid damper (TLD) having a relatively simple, easy-to-model behavior and high effectiveness in controlling structural vibrations. It consists of a traditional TLD with addition of a floating roof. Since the roof is much stiffer than water, it prevents wave breaking, hence making the response linear even at large amplitudes. The roof also facilitates the incorporation of supplemental devices with which the level of damping of the liquid vibration can be substantially augmented. This newly proposed TLD, denoted as tuned liquid damper with floating roof (TLD-FR), maintains the traditional advantages of TLDs (low cost, easy installation and tuning), but its numerical characterization is much simpler because the floating roof suppresses higher sloshing vibration modes, resulting in a system that can be represented by a single-degree-of-freedom model. An efficient numerical scheme, where the dynamic behavior of the TLD-FR is expressed as a second-order lineal system of equations, is discussed and validated by scaled experimental tests. The equations of motion of a structure equipped with a TLD-FR are then derived and manipulated to offer a unifying representation dependent upon only four model characteristics of the TLD-FR: The first three (mass, frequency and damping ratios) are common for all type of mass dampers, whereas the final one, termed efficiency index, is related to a similar parameter used to characterize liquid column dampers. Through this approach, the behavior of the proposed TLD-FR can be easily correlated with the behavior of other well-known linear mass damper devices. The relationship between these parameters and the geometrical characteristics of the TLD-FR is also examined. Finally, the identification of the optimal characteristic of the TLD-FR (natural frequency and damping) under stationary stochastic excitation is discussed. © 2016 Springer-Verlag Wien Source

Ruiz R.,University of Notre Dame | Ruiz R.,University of Santiago de Chile | Taflanidis A.A.,University of Notre Dame | Lopez-Garcia D.,University of Santiago de Chile | And 2 more authors.
Bulletin of Earthquake Engineering | Year: 2016

The assessment of the effectiveness of mass dampers for the Chilean region within a multi-objective decision framework utilizing life-cycle performance criteria is considered in this paper. The implementation of this framework focuses here on the evaluation of the potential as a cost-effective protection device of a recently proposed liquid damper, called tuned liquid damper with floating roof (TLD-FR). The TLD-FR maintains the advantages of traditional tuned liquid dampers (TLDs), i.e. low cost, easy tuning, alternative use of water, while establishing a linear and generally more robust/predictable damper behavior (than TLDs) through the introduction of a floating roof. At the same time it suffers (like all other liquid dampers) from the fact that only a portion of the total mass contributes directly to the vibration suppression, reducing its potential effectiveness when compared to traditional tuned mass dampers. A life-cycle design approach is investigated here for assessing the compromise between these two features, i.e. reduced initial cost but also reduced effectiveness (and therefore higher cost from seismic losses), when evaluating the potential for TLD-FRs for the Chilean region. Leveraging the linear behavior of the TLD-FR a simple parameterization of the equations of motion is established, enabling the formulation of a design framework that beyond TLDs-FR is common for other type of linear mass dampers, something that supports a seamless comparison to them. This framework relies on a probabilistic characterization of the uncertainties impacting the seismic performance. Quantification of this performance through time-history analysis is considered and the seismic hazard is described by a stochastic ground motion model that is calibrated to offer hazard-compatibility with ground motion prediction equations available for Chile. Two different criteria related to life-cycle performance are utilized in the design optimization, in an effort to support a comprehensive comparison between the examined devices. The first one, representing overall direct benefits, is the total life-cycle cost of the system, composed of the upfront device cost and the anticipated seismic losses over the lifetime of the structure. The second criterion, incorporating risk-averse concepts into the decision making, is related to consequences (repair cost) with a specific probability of exceedance over the lifetime of the structure. A multi-objective optimization is established and stochastic simulation is used to estimate all required risk measures. As an illustrative example, the performance of different mass dampers placed on a 21-story building in the Santiago area is examined. © 2015, Springer Science+Business Media Dordrecht. Source

Becerra A.,University of Santiago de Chile | Podesta L.,University of Santiago de Chile | Monetta R.,Diego Portales University | Saez E.,University of Santiago de Chile | And 4 more authors.
Natural Hazards | Year: 2015

This paper focuses on a geophysical-based analysis of the soils in Arica and Iquique, both main cities in northern Chile. The large seismogenic coupling and the 136-year seismic gap predispose the north of the country to the highly likely seismic activity that could affect this area. This seismotectonic scenario highlights the importance of the assessment of earthquake hazards in urban domains. In this context, seismic microzoning emerges as a tool to identify areas that are more or less susceptible to ground motion amplification. In both cities, 148 sites were chosen to perform geophysical surveys based on surface wave methods, namely the spatial autocorrelation, frequency-wave number and H/V spectral ratio techniques. By inverting the measurements, local shear wave velocity profiles and predominant frequencies were derived. Additionally, seven boreholes were drilled to further complement the gathered data. With the available results, the cities were subdivided into different zones with similar properties in terms of the average shear wave velocity on the upper 30 m (Vs30) and the predominant site’s frequency $$F_0$$F0; these were parameters that were found consistent with the geology of each city. The collected information suggests zones that are more prone to ground motion amplification, namely: the northern side of Arica, the south-east area of Iquique, the northern limit of Iquique and the artificial landfill of the port of Iquique. The microzoning was compared to the ground motion records of the April 1, 2014, Iquique earthquake and showed to be consistent with the expected motion amplification in Iquique. © 2015, Springer Science+Business Media Dordrecht. Source

Pacheco C.,National Research Center for Integrated Natural Disaster Management 15110017 | Karelovic P.,University of Santiago de Chile | Cipriano A.,National Research Center for Integrated Natural Disaster Management 15110017 | Cipriano A.,University of Santiago de Chile
2015 European Control Conference, ECC 2015 | Year: 2015

A comparative study of dynamic evacuation control strategies for emergency situations such as fires or earthquakes is presented. © 2015 EUCA. Source

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