A new structural system conceived to control Base Isolated System vibrations under random excitat... more A new structural system conceived to control Base Isolated System vibrations under random excitations is analyzed. The new system combines the Tuned Mass Damping strategy with the Isolation concept in order to obtain a new system which principally attenuates the effects of the seismic excitation components with frequencies close to the fundamental natural vibration one. The Random response of equivalent linear Base Isolated Systems controlled by Tuned Mass Dampers subject to horizontal random excitations is analyzed. Considering the superstructure motion described by its first modal contribution, a three-degree-of-freedom linear model subject to stationary Gaussian excitations, modelled by the modified Kanai-Tajimi power density spectrum, was used in this analysis. The standard deviation response ratio of the new system respect to the one of the base isolated system was evaluated based on a wide range of parameters. Optimal parameters which minimize structural response were also obtained.
A preliminary attempt to organize innovative strategies such as Base Isolation, Supplemental Ener... more A preliminary attempt to organize innovative strategies such as Base Isolation, Supplemental Energy Dissipation, Tuned Mass Damping and other combined approaches recently proposed by the authors, in a more general theory of Structural Control, is presented. To visualize the relationships between dynamic variables and subsystems, the block-diagram representations are used in order to obtain the regulation properties of the systems. It has been proven that the Base Isolation technique applies an open-loop control law and that Tuned Mass Damping and Supplemental Energy Dissipation realize closed-loop control laws. The block-diagram of the new combined strategy Base Isolation and Tuned Mass Damping is presented. The objectives of the regulating criteria are also discussed in order to shape the dynamic response in the frequency domain. The H 2 and H ∞ methods are considered as optimal control algorithms.
ABSTRACT A rational methodology to evaluate behaviour factors for base isolated structures (BIS) ... more ABSTRACT A rational methodology to evaluate behaviour factors for base isolated structures (BIS) code design is presented. The method used in this study is to directly derive q-factors by the nonlinear response analysis of 2 d.f. isolated models subject to strong seismic excitations artificially generated according to EC8 design spectra. The influence of several parameters on the ultimate behaviour of BIS has been analysed and collapse spectra have been derived for base isolated structures. Having defined theoretical collapse conditions for a 2 d.f. system subject to a set of artificial excitations, the minimum strength spectra needed for the structural survival have been evaluated. By dividing the elastic design spectra by the inelastic response ones, reduction factors for base isolated structures can be determined. A comparison with the UBC-91 new requirements for isolated structures shows a good agreement between the recommended behaviour factors and the ones calculated in the present paper.
ABSTRACT SOMMARIO L'impiego di dispositivi passivi di dissipazione energetica nell&#3... more ABSTRACT SOMMARIO L'impiego di dispositivi passivi di dissipazione energetica nell'ambito delle costruzioni civili può essere considerata una tecnologia matura per l'applicazione su vasta scala. Questa strategia di protezione sismica ha dimostrato sul campo di consentire il conseguimento di prestazioni sismiche elevate permettendo un efficace controllo del danno. In tale ambito, il presente lavoro propone una nuova metodologia di controllo della risposta sismica di nuovi edifici ovvero di strutture esistenti mediante la disposizione ottimale di dispositivi di dissipazione energetica. Tale disposizione è perseguita massimizzando un opportuno indice prestazionale rappresentativo della potenza complessiva dissipabile dal sistema in considerazione delle caratteristiche spettrali della domanda sismica e delle proprietà dinamiche del sistema da proteggere. La nuova metodologia di progetto proposta è testata valutando la risposta sismica di strutture benchmark ad eventi sintetici rappresentativi degli spettri di risposta proposti dall'Euro Codice 8. ABSTRACT The use of passive dissipation devices in civil buildings has to be considered a mature technology for a wide practical application. Because of its high effectiveness, this seismic protection strategy could be considered with the need to control the structural damage. Therefore, there's an urgent need to define reliable methodologies for an optimal design of such devices both for existing and new structures. These new design methodologies have to produce reliable results using conceptually simple tools. This paper proposes a set of experimental numerical analysis on benchmark structures, having the double aim to point out the qualitative aspects of extrastructural damping protection strategy and to show the effectiveness of a new design methodology to optimally place dissipation devices in order to improve the seismic response of framed structures. In particular, such an optimization problem is solved by using an iterative procedure, based on the maximisation of an index related to the maximum dissipated power by the overall system.
Two different optimal control strategies defined in the frequency domain are discussed in this pa... more Two different optimal control strategies defined in the frequency domain are discussed in this paper. The general formulation of H2 and H∞ is reorganized in an easy way to be used for mechanical applications. Both the control methodologies are reviewed for general problems and applied to simple systems by showing their main mechanical aspects and differences. The two methods have been numerically compared in controlling the seismic response of a base isolated system equipped with a hybrid mass damper.
A new structural system conceived to control Base Isolated System vibrations under random excitat... more A new structural system conceived to control Base Isolated System vibrations under random excitations is analyzed. The new system combines the Tuned Mass Damping strategy with the Isolation concept in order to obtain a new system which principally attenuates the effects of the seismic excitation components with frequencies close to the fundamental natural vibration one. The Random response of equivalent linear Base Isolated Systems controlled by Tuned Mass Dampers subject to horizontal random excitations is analyzed. Considering the superstructure motion described by its first modal contribution, a three-degree-of-freedom linear model subject to stationary Gaussian excitations, modelled by the modified Kanai-Tajimi power density spectrum, was used in this analysis. The standard deviation response ratio of the new system respect to the one of the base isolated system was evaluated based on a wide range of parameters. Optimal parameters which minimize structural response were also obtained.
A preliminary attempt to organize innovative strategies such as Base Isolation, Supplemental Ener... more A preliminary attempt to organize innovative strategies such as Base Isolation, Supplemental Energy Dissipation, Tuned Mass Damping and other combined approaches recently proposed by the authors, in a more general theory of Structural Control, is presented. To visualize the relationships between dynamic variables and subsystems, the block-diagram representations are used in order to obtain the regulation properties of the systems. It has been proven that the Base Isolation technique applies an open-loop control law and that Tuned Mass Damping and Supplemental Energy Dissipation realize closed-loop control laws. The block-diagram of the new combined strategy Base Isolation and Tuned Mass Damping is presented. The objectives of the regulating criteria are also discussed in order to shape the dynamic response in the frequency domain. The H 2 and H ∞ methods are considered as optimal control algorithms.
ABSTRACT A rational methodology to evaluate behaviour factors for base isolated structures (BIS) ... more ABSTRACT A rational methodology to evaluate behaviour factors for base isolated structures (BIS) code design is presented. The method used in this study is to directly derive q-factors by the nonlinear response analysis of 2 d.f. isolated models subject to strong seismic excitations artificially generated according to EC8 design spectra. The influence of several parameters on the ultimate behaviour of BIS has been analysed and collapse spectra have been derived for base isolated structures. Having defined theoretical collapse conditions for a 2 d.f. system subject to a set of artificial excitations, the minimum strength spectra needed for the structural survival have been evaluated. By dividing the elastic design spectra by the inelastic response ones, reduction factors for base isolated structures can be determined. A comparison with the UBC-91 new requirements for isolated structures shows a good agreement between the recommended behaviour factors and the ones calculated in the present paper.
ABSTRACT SOMMARIO L'impiego di dispositivi passivi di dissipazione energetica nell&#3... more ABSTRACT SOMMARIO L'impiego di dispositivi passivi di dissipazione energetica nell'ambito delle costruzioni civili può essere considerata una tecnologia matura per l'applicazione su vasta scala. Questa strategia di protezione sismica ha dimostrato sul campo di consentire il conseguimento di prestazioni sismiche elevate permettendo un efficace controllo del danno. In tale ambito, il presente lavoro propone una nuova metodologia di controllo della risposta sismica di nuovi edifici ovvero di strutture esistenti mediante la disposizione ottimale di dispositivi di dissipazione energetica. Tale disposizione è perseguita massimizzando un opportuno indice prestazionale rappresentativo della potenza complessiva dissipabile dal sistema in considerazione delle caratteristiche spettrali della domanda sismica e delle proprietà dinamiche del sistema da proteggere. La nuova metodologia di progetto proposta è testata valutando la risposta sismica di strutture benchmark ad eventi sintetici rappresentativi degli spettri di risposta proposti dall'Euro Codice 8. ABSTRACT The use of passive dissipation devices in civil buildings has to be considered a mature technology for a wide practical application. Because of its high effectiveness, this seismic protection strategy could be considered with the need to control the structural damage. Therefore, there's an urgent need to define reliable methodologies for an optimal design of such devices both for existing and new structures. These new design methodologies have to produce reliable results using conceptually simple tools. This paper proposes a set of experimental numerical analysis on benchmark structures, having the double aim to point out the qualitative aspects of extrastructural damping protection strategy and to show the effectiveness of a new design methodology to optimally place dissipation devices in order to improve the seismic response of framed structures. In particular, such an optimization problem is solved by using an iterative procedure, based on the maximisation of an index related to the maximum dissipated power by the overall system.
Two different optimal control strategies defined in the frequency domain are discussed in this pa... more Two different optimal control strategies defined in the frequency domain are discussed in this paper. The general formulation of H2 and H∞ is reorganized in an easy way to be used for mechanical applications. Both the control methodologies are reviewed for general problems and applied to simple systems by showing their main mechanical aspects and differences. The two methods have been numerically compared in controlling the seismic response of a base isolated system equipped with a hybrid mass damper.
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