167 research outputs found
DIBRAST: A Computer-Aided Seismic Design Procedure for Frame Structures Equipped With Hysteretic Devices
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Smart hybrid isolation of a case study highway bridge exploiting seismic early warning information
No full textAn innovative technique for seismic retrofit of a case study highway bridge is presented herein. It is done by means of the friction pendulum isolators (FPS) combined with smart magnetorheological dampers (MR), the latter calibrated through the use of a Seismic Early Warning System (SEWS). Hybrid systems, widely investigated by researchers in last years, generally represent a suitable solution in case of base-isolated bridges. As a matter of facts, the introduction of an isolation system allows to reduce shear and bending moment in piers, but may increase decks’ relative displacements. A possible effective strategy for limiting this undesired effect may be the adoption of a dissipative system. Herein the passive smart use of MR devices is proposed. The MR dampers are smart in the sense that their mechanical properties can be tuned almost in real time, once before the earthquake strikes the site. A properly designed control algorithm modifies dampers' characteristics according to the intensity of the seismic event is going to occur, as forecasted by the SEWS. This retrofit strategy makes the structure someway adaptive, leading to a significant enhancement of the seismic performance against earthquakes even very different one each other. The case study is an existing reinforced concrete highway bridge built in the 70’s, located in the city of Naples, southern Italy
Use, Effectiveness and Long Term Reliability of MR Dampers for Seismic Protection of Framed Structures
No full textThe implementation, operation and efficacy of semi-active (SA) structural control
systems based on the adoption of magnetorheological (MR) devices are still object of research.
For a such system, generally a complex electronic equipment is required to acquire then elaborate
then generate signals to properly command the smart devices in real time. Given this, the
effectiveness of these control systems in reducing the seismic response of structures is often
called into question. And one wonders about the performance of these systems in the long term,
i.e. when called to respond to seismic actions after many years since their installation. Will the
devices be ready to respond? Is their dissipative capacity still that exhibited before their installation?
This work attempts to present a comprehensive description and offer suitable solutions
for a number of specific aspects that characterize the implementation of SA control systems.
Authors also highlight undesired and unavoidable effects and provide insights on the way to
reduce their incidence. The performance of such system is then showed via a shaking table test
of a full-scale steel structure. These tests allowed to measure the actual short-term effectiveness
of this system. After 10 years of inactivity of those MR devices, these have been subjected characterization
tests once again, in order to assess the evolution of their mechanical behaviour
over time and the decay of performance. The long-term response in terms of readiness, dissipative
capacity and reaction force was measured, leading to positive conclusions about the
reliability of the control system after years of inactivity
A friction-based passive control technique to mitigate wind induced structural demand to wind turbines
No full textA BIM-based decision-making framework for optimal seismic retrofit of existing buildings
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Selezione dell’intervento di adeguamento sismico: il ruolo del BIM nel processo decisionale
No full textIn questo lavoro si presenta uno strumento innovativo, implementato in ambiente BIM, per il supporto alla
decisione in ambito di adeguamento sismico di opere esistenti. Oggi esistono, difatti, numerose tecnologie di
retrofit sismico, anche molto differenti tra loro, e l’individuazione di quella ottimale, contestualizzata rispetto allo
specifica struttura, è quasi sempre un problema complesso a causa della molteplicità di criteri socio-economici e
tecnici da dover considerare, spesso in conflitto tra loro. L’implementazione di un metodo decisionale multi-criterio
consente, in quest’ottica, di confrontare soluzioni alternative in funzione dei vari criteri ritenuti significativi,
assegnando a ciascuno di essi dei pesi e individuando, infine, la soluzione migliore nei confronti di questi. In
quest’ottica, il BIM è ritenuto uno strumento molto efficace per fornire informazioni di natura anche molto
differente, in un unico modello integrato. L’integrazione del problema decisionale in ambiente BIM consente non
solo di attingere una notevole semplificazione nell’implementazione dello stesso, per quanto fornisce una
completezza di informazioni necessaria al decisore per realizzare una scelta quanto più consapevole ed informata
Fire and seismic assessment of an existing steel-concrete composite structure
No full textAn existing steel-concrete composite structure is analyzed in order to assess its level of protection
against both fire and earthquakes. The building has been designed and built more than thirty years
ago, implying that both these hazards may not be adequately verified with respect to the current
codes. As concerns the fire protection, intumescent coating (IC) was applied on steel members,
while an original passive energy dissipation system was employed against seismic actions. In
particular, special devices were introduced to sustain the floors, which are suspended at reticular
beams on the top of concrete pillars. A Fire Safety Engineering approach has been adopted to assess
the structural resistance to fire. To define the thermal properties of the protective, experimental tests
were carried out on the existing IC and a new IC. Moreover, thermomechanical analyses of the
existing steel structure were carried out, under different fire scenarios, selected according to the fire
risk of the different occupancy class of the structure. Non-linearities and large displacements effects
were taken into account. The seismic structural response has been investigated by implementing a
dynamic nonlinear analysis according to the current Italian Code. In particular the seismic passive
protection system, consisting in dissipative hysteretic devices combined with isolators, has been
modelled as a parallel elastic and elasto-plastic springs’ system. Mechanical parameters adopted for
the analyses are the result of a wide bibliography study
Strategie pragmatiche di introduzione di un Topic Discorsivo in dialoghi task-oriented: lingue a confronto
No full textThe purpose of this study is to analyse qualitatively and quantitatively how speakers of different languages introduce new Discourse Topics in dialogical speech. For the qualitative analysis, we present some functional-pragmatic continua as reliable means of accountingfor the dynamics of communicative strategies. With respect to the quantitative analysis, we examine the percentage of occurrences of pragmatic moves used to introduce a Discourse Topic. The study examines a multilingual corpus of task-oriented dialogues in Italian, Spanish, German and English. The analysis of Discourse Topics introduction allows to identify in-teresting textual characteristics. Speakers of all languages prefer moves which are oriented to successful task completion, without being impolite or aggressive. However, in each language speakers choose a different pragmatic pattern to signal attention to the interlocutor
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