178 research outputs found
Salvatore Puliatti: la formazione e l'attività istituzionale. La produzione scientifica
No full text
Effects of deep excavation on seismic vulnerability of existing reinforced concrete framed structures
No full textIn this paper the effects of deep excavation on seismic vulnerability of existing buildings are investigated. It is well known that deep excavations induce significant changes both in stress and strain fields of the soil around them, causing a displacement field which can modify both the static and dynamic responses of existing buildings. A FEM model of a real case study, which takes into account geometry, non-linear soil behavior, live and dead loads, boundary conditions and soil–structure interaction, has been developed in order to estimate the soil displacements and their effects on seismic behavior of a reinforced concrete framed system close to deep excavation. Considering a significant accelerometric seismic input, the non-linear dynamic responses of the reinforced concrete framed structure, both in the pre and post-excavation configurations, have been evaluated and, then, compared to estimate the modification in seismic vulnerability, by means of different seismic damage indices and inter-story drifts
Approccio prestazionale per la progettazione integrata di sistemi strutturali dotati di dispositivi viscosi lineari
No full textSi sviluppa una procedura di progettazione integrata del sistema strutturale ad un grado di libertà e del sistema di controllo passivo costituito da dispositivi viscosi lineari, basata su un approccio prestazionale. Le variabili di progetto considerate sono la rigidezza laterale della struttura rappresentativa del suo comportamento lineare in campo dinamico, la rigidezza della diagonale (brace) e la costante di viscosità del dispositivo viscoso costituenti la serie "viscous damper-brace component", il cui comportamento dinamico non lineare viene esplicitamente tenuto in conto. Lo studio viene condotto su un sistema ad un singolo grado di libertà (SDOF) mediante analisi dinamiche al passo considerando un set di registrazioni accelerometriche storiche non scalate compatibili, in termini di media, con lo spettro elastico relativo allo SLV definito dalle NTC08 per uno specifico sito in Italia. L'ottimo progettuale, relativo ad una prefissata prestazione, è rappresentato dai valori delle tre grandezze di progetto che minimizzano il costo totale della struttura valutato sulla media dei risultati ottenuti prendendo in esame il set di registrazioni accelerometriche selezionate
Measuring and improving community resilience: A fuzzy logic approach
No full textDue to the increasing frequency of natural and man-made disasters, the scientific community has paid considerable attention to the concept of resilience engineering. On the other hand, authorities and decision-makers have been focusing their efforts on developing strategies that can help increase community resilience to different types of extreme events. Since it is often impossible to prevent every risk, the focus is on adapting and managing risks in ways that minimize impacts to communities (e.g., humans and other systems). Several resilience strategies have been proposed in the literature to reduce disaster risk and improve community resilience. Generally, resilience assessment is challenging due to uncertainty and the unavailability of data necessary for the estimation process. This paper proposes a Fuzzy Logic method for quantifying community resilience. The methodology is based on the PEOPLES framework, an indicator-based hierarchical framework that defines all aspects of a community. A fuzzy-based approach is implemented to quantify the PEOPLES indicators using descriptive knowledge instead of complex data, accounting for the uncertainties involved in the analysis. To demonstrate the applicability of the methodology, three cases with different levels of data availability are performed to obtain a resilience curve and resilience index of two out of seven dimensions of the PEOPLES framework. When numerical data does not exist, descriptive data based on expert knowledge is used as input. Results show that the proposed methodology can cope with both numerical and descriptive input data with different uncertainty levels providing good estimates of resilience. The methodology can be used as a decision-support tool to assist decision-makers and stakeholders in assessing and improving their communities' resilience for future events, focusing on specific indicators that suffer from resilience deficiencies and need improvements.System Engineerin
Analisi della domanda sismica inelastica del terremoto de L’Aquila su sistemi dimensionati secondo le NTC2008
No full textThe study investigates on the inelastic response of equivalent Simple Degree Of Freedom systems (SDOF) to some L'Aquila earthquake accelerograms recorded in the epicentral area. According to recent statistical analysis, L'Aquila earthquake is considered as a seismic event having a return period of about 475 years. The aim of the paper is to give a first interpretation to the high damage levels (IX-X MCS) due to the earthquake, in spite of its moderate magnitudo (ML = 5.8) and the correct historical seismic classification of the stroked area. The study thus analyzes the inelastic seismic demand of a SDOF designed according to the NTC08 to four near-fault accelerograms recorded during the L'Aquila earthquake main shock, by varying SDOF capacity in terms of strength, ductility and viscous damping, in order to assess the performance targets imposed by the same NTC08. Two well-known damage indices have been used to estimate seismic effects on built environment: Park & Ang and low-cycle fatigue indices. The results highlight the high seismic inelastic demand, well beyond the limit specified in NTC08, both for the design of new buildings and for seismic upgrading of existing ones. This highlights the need for a revision of the actual seismic hazard map taking into account the near-fault and site amplification effects, which are not considered within the seismic hazard methods adopted by the NTC08
Optimal integrated design of structural and viscoelastic bracing-damper systems: theoretical principles
No full textPassive structural control techniques are generally used as seismic rehabilitation and retrofit methodologies of existing structures. An exciting consequence of structural seismic control research is that it opens the mind to new possibilities in structural forms and configurations, such as slender buildings or bridges with longer spans, without compromising on structural performance through an integrated design of systems. In this paper, with reference to the viscous or viscoelastic dampers, the possibility of achieving the seismic protection through the integration of the elastic lateral stiffness resources and the viscoelastic properties of a dissipative bracing-damper system is investigated. The innovative aspect consists of considering the viscoelastic damping resources as a design variable in order to control the dynamic response. It is thus proposed and developed an integrated design methodology to ensure a preassigned performance, within the displacement based design approach, which explicitly takes into account the dynamic behavior both of the structural and control systems. The optimal design criterion is defined by determining the combination of the variables which minimizes a total cost function. Application of the proposed design approach on a SDOF system is described to show its effectiveness
Robust design of a Single Tuned Mass Damper for controlling torsional response of asymmetric-plan systems
No full textA new robust design methodology to control the seismic performance of asymmetric structures
equipped with a Single Tuned Mass Damper (STMD) is presented in this paper. This design
approach aims to control the seismic response of such systems by reducing both flexible and stiff
edge maximum displacement. The dynamic problem has been investigated in the state space
representation showing that the TMD works as a closed-loop feedback control action. A synthetic
index to estimate the seismic performance of the main system has been defined by using H„V norm.
Wide-ranging parametric numerical experimentation has been carried out to obtain design formulae
for the STMD in order to minimize such a performance index. These formulae allow for a simple
design of STMD position and stiffness to optimally control both translational and rotational motion
components, whereas two mass devices are generally considered to improve the seismic
performance of asymmetric structural systems The effectiveness and efficiency of the obtained
design formulae have been tested by investigating the dynamic behavior of the asymmetric structure
after being subjected to different recorded seismic inputs
An Energy-based Approach to the Seismic Control of One-Way Asymmetrical Structural Systems using Semi-Active Devices
No full textThe study proposes a semiactive approach to control the dynamic response of a one-way plan-wise asymmetrical structural system by defining a set of closed-form analytical control algorithms to drive semi-active viscous devices in order to optimize different energy rates of the system to be protected, namely damping energy, elastic energy, kinetic energy and input energy. These algorithms are tested by means of a large numerical experimentation by modifying the main structural parameters of asymmetrical system and considering different accelerometric input signals. Finally, the seismic response both in terms of relative displacement and energy rates, has been comparatively evaluated in the case of uncontrolled and semiactivelly controlled systems, by using the proposed algorithms. Results showed the efficiency of the strategy, especially when flexible systems and high spread device configurations are taken into account
EFFETTI DI SCAVI PROFONDI SULLA RISPOSTA SISMICA DELL'EDIFICATO ADIACENTE
No full textSi esamina l'effetto di scavi profondi sulla risposta sismica dell'edificato adiacente. In particolare si studia la modificazione della vulnerabilità sismica dell'edificato esistente in seguito all'esecuzione di scavi profondi in aree adiacenti per la realizzazione di grandi opere sotterranee. E' noto infatti che l'esecuzione di scavi profondi comporta l'insorgere in superfice di un campo di spostamenti in grado di modificare l'assetto statico dell'edificato circostante. L'obiettivo dello studio è quello di valutare le eventuali variazioni di vulnerabilità sismica degli edifici esistenti per effetto di scavi posticipati rispetto alla loro edificazione. Si esamina un caso studio di interazione suolo-scavo-edificato, modellato in PLAXIS, analizzando in una prima fase gli effetti dei movimenti del suolo indotti dallo scavo su di un edificio e simulando la risposta non lineare ad una eccitazione sismica dello stesso edificio prima e dopo l'esecuzione dello scavo al fine di una valutazione comparativa della vulnerabilità sismica
- …
