Title: Ricostruire l’Appennino Centrale tra Innovazione e Sicurezza

Abstract: Il territorio italiano ha un primato assoluto in Europa: quello della maggiore sismicità continentale. Su 1.300 terremoti distruttivi di cui si ha memoria e documentazione nel secondo Millennio, nell’area del Mediterraneo, almeno 500 hanno interessato il nostro Paese. Insomma, l’Italia è un Paese quasi totalmente esposto al rischio sismico, cambia solo la frequenza attesa e la potenza liberata.

La ricostruzione da un terremoto costa in genere circa 10-100 volte di più che realizzare un adeguamento o un miglioramento antisismico. Dal terremoto del Belice in poi si stima che le ricostruzioni post sisma siano costate fino a 200 miliardi, senza contare i danni economici indiretti. 

È la prima volta che, nell’ambito di una ricostruzione post sisma di vasta portata come quella dell’Italia Centrale (la sequenza sismica 2016-2017 ha interessato un’area di 8000 kmq, distruggendo edifici per un valore di circa 28 miliardi di euro), viene pianificato un lavoro di analisi sistematica, con controlli sul campo e l’uso di tecnologie avanzate sulle aree di dissesto individuate. 

Ricostruire in sicurezza vuol dire aver sciolto definitivamente quella visione datata e irrealistica della ricostruzione “dov’era, com’era”. Dopo le indicazioni univoche offerte dalla conferenza di Sendai oggi l’attenzione si è spostata, opportunamente, sulla necessità di migliorare la comprensione del rischio di disastri in tutte le sue dimensioni di esposizione, vulnerabilità e caratteristiche di pericolosità; la responsabilità per la gestione del rischio di disastri deve avere l’obiettivo di "ricostruire meglio", laddove sia possibile e sicuro farlo. 

Nella ricostruzione in atto nel più grande cantiere edile d’Europa abbiamo due “case histories” all’avanguardia: Arquata del Tronto e Castelluccio di Norcia. Due esempi di questo innovativo percorso di messa in sicurezza prima di ricostruire. Due progettazioni ormai diventati oggetto di studio in Italia e all’estero.

Title: Large Ship Impacts on Bridge Piers

Abstract:The Key Bridge in Baltimore stood for more than half a century until it collapsed when a massive ship it was never designed to withstand collided with it. Ship collision design provisions established in 1991, well after the bridge was built, suggest that the chance of collision was extremely low, estimated to be around 1/100,000. This risk assessment, which ultimately proved to be overly optimistic, likely contributed to a false sense of security about the bridge’s vulnerability and may have impeded proactive measures to reinforce the structure.  Collapse of this bridge also highlighted the need for critical investigation through complex simulations using impact of large ships into bridge piers to determine the sufficiently of current AASHTO guideline and development of simulation tools to investigate safety of bridge piers from large ship impacts.  This presentation will highlight various critical aspects of the impact of large ships on bridge piers.

Title: Bradiseism and volcanic hazard at Campi Flegrei, Italy

Abstract: The Phlegraean Fields (Campi Flegrei) are a volcanic caldera formed by the eruptions of the Campanian Ignimbrite (39,000 years ago) and the Yellow Tuff (15,000 years ago). Subsequently, three periods of activity can be distinguished, during which about 70 eruptions occurred, separated by long periods of quiescence. The most recent eruption took place in 1538, and it is well documented through images and historical documents. The typical hazardous eruptive phenomena include the generation of pyroclastic flows, the dispersal and fallout of volcanic ash, and lava flows. More recently, the "bradyseism risk" has been officially recognized, referring to ongoing ground deformation and associated earthquakes in the area. An additional hazard that is now being discussed is the potential occurrence of phreatic explosions, which may be triggered by the rapid depressurization of shallow portions of the hydrothermal system. The presentation will illustrate the various hazards related to the possible opening of new eruptive vents and volcanic eruptions, as well as the damage associated with seismic activity, ground deformation, and gas emissions that occur during bradyseismic crises, such as the one that has been ongoing since 2005.

Title: Performance of Seismically Isolated Structures in Earthquakes.

Abstract: many seismically isolated structures have been constructed, ranging from houses, apartment buildings, hospitals, emergency facilities, architecturally and historically significant structures and tall buildings to large bridges and offshore platforms.  The observation of performance of such structures in earthquakes provides valuable information on the validity of design procedures and on the lifetime behavior of isolators and delivers lessons on actions that are needed to avoid problems and enhance reliability.

The presentation will start with a discussion of design procedures for seismically isolated structures, uncertainty and reliability in design.  This guides the audience to a better understanding of the observed performance of several seismically isolated structures that are presented next.  It is concluded that, in general, the performance of seismically isolated structures is very good but dependent on proper analysis and design, provisions for increased capacities of isolators and superstructures to meet reliability objectives, effective peer review, testing (prototype and production) of isolators, proper construction and inspection.

Tilte - Recent Developments in Site Response Analysis and Microzonation

Abstract: The basic purpose of site response analysis is to evaluate possible local site effects and the earthquake characteriscs on the ground surface to estimate probable earthquake damage for the existing building stock and for the design of new structures. The basic issues in the site response analysis are the inherent uncertainty in source characteristics, soil profile, soil properties, and site response analysis procedure. In addition, characteristics of the building inventories would introduce critical uncertainties associated with these analyses. Recent advances, with growing computational capacity, emphasize probabilistic frameworks to capture these uncertainties. The probability distribution of the related earthquake parameters on the ground surface may be determined considering all possible input acceleration time histories, site profiles, and dynamic soil properties. One option to account for the variability in earthquake source and path effects may be to consider using large number of acceleration records compatible with the site-dependent earthquake hazard partially based on  hazard deaggregation at the investigated site. Likewise, stochastic soil profiles generated via Monte Carlo simulations can be used to account for the site condition variability. A comprehensive seismic microzonation methodology is proposed based on the probabilistic assessment of these factors involved in site response analyses. The second important issue is the selection of microzonation parameters. The selection of microzonation parameters—such as Cumulative Absolute Velocity (CAV) and Housner Intensity (HI)—is emphasized for their stronger empirical correlation with structural damage. The main approach is to develop a microzonation procedure for ground shaking intensity accounting for variability in ground motion and soil response. The third issue is the reliability and correctness of the site response analysis procedure. The adopted methodology advances traditional site response analysis by integrating frequency- and stress-dependent soil behavior models to achieve a more accurate numerical model and proposing the use of 3D site response analysis to reflect the multi-directional nature of seismic loading. It also highlights the need for representative time histories with known exceedance probabilities. Even though the selected representative acceleration time histories may be scaled with respect to probabilistic acceleration spectrum or peakground acceleration obtained based on probabilistic site response analysis; the probability of the selected acceleration time histories are not known. The only possible option is to estimate probabilistic acceleration time histories with predetermined exceedance probabilities to enhance fully probabilistic site response analysis. The proposed methodology is demonstrated through case studies based on data from the Istanbul Rapid Response Network, to underline the importance of fully probabilistic site response analysis in seismic microzonation, aiming to improve the reliability of ground motion predictions and support informed decision-making in earthquake engineering.