1,721,043 research outputs found
Systemic Vulnerability and Risk Assessment of Transportation Systems Under Natural Hazards Towards More Resilient and Robust Infrastructures
No full textAbstractTransportation infrastructures are complex systems of various connected components like bridges, roads, tunnels, embankments, retaining walls in case of a highway system or wharfs, cranes, buildings, utility systems in case of port facilities. Due to their spatial extent, they are exposed to variable natural hazards such as earthquakes, tsunami or landslides. Experience from past disastrous events shows that transportation infrastructures are quite vulnerable due to the lack of redundancy, the lengthy repair time, the rerouting difficulties or the cascading failures and interdependencies. Their damage could be greatly disruptive in terms of safety of life, business disruption, access to emergency services and key lifelines utilities, rescue operations and socio-economic impacts. Therefore, in terms of resilience it is important to recognize and quantify the risks and global losses associated to damages of transportation systems and to establish efficient risk mitigation strategies. These include, among others, enhancement of emergency preparedness, strengthening of existing structures and improvement of the recovery planning.Herein an integrated framework for the probabilistic systemic vulnerability and risk assessment of transportation and utility networks is presented, based on the achievements of the recently completed EC project SYNER-G (www.syner-g.eu) and the ongoing EC project STREST (www.strest-eu.org). The infrastructure is modeled according to a detailed taxonomy. The framework encompasses in an integrated fashion all aspects in the chain, from regional hazard to fragility assessment of components to the socio-economic impacts of a natural disaster, accounting for relevant uncertainties within an efficient quantitative simulation scheme, and modeling interactions between multiple component systems in the taxonomy. Selected Performance Indicators (PIs) are calculated for each network based on the estimated damages and functionality losses of the different components under the given hazards.The methodology and tools are demonstrated through case studies in the road network and the harbor of Thessaloniki city, Greece, under seismic hazard and associated geotechnical hazards (i.e. soil liquefaction). The applications include assessments of systems’ performance considering the spatial seismic hazard with correlation of ground motion intensities, the vulnerability of the network components, and the effect of interactions within the system, as well as, between components of different systems. In particular, road disruptions can be caused due to direct damage of road segments and bridges, as well as building and overpass collapses. Harbor operations can be disturbed due to failures of waterfront structures and cargo handling equipment, as well as disruptions to the electric power supply and building collapses. The systemic risk for the road network and harbor is calculated, specifically focusing on the short-term impact of seismic events (just after the earthquake) and the risk curves (i.e. mean annual rates of exceedance for loss in performance of the infrastructures) are provided. The significant elements for the functionality of each system are defined through correlation factors to the system PIs. Such results can contribute to the decision-making regarding the enhancement of existing and the robust development of new infrastructures in the frame of safety and resiliency
Evaluation of earthquake ground motion and site effects in the Thessaloniki urban area by 3D finite-fault numerical simulations
No full textIn this study earthquake ground motion in the Thessaloniki urban area is evaluated using a 3D spectral element numerical approach. The availability of detailed geotechnical/geophysical data from past microzonation studies together with the seismological information regarding the relevant fault sources allowed for the creation of a large-scale 3D numerical model suitable for generating finite-fault physics-based ground shaking scenarios within the city of Thessaloniki up to maximum frequencies of about 1.5 Hz. As a representative case study, the simulation of the historical MW6.5 June 20th 1978 Volvi earthquake is addressed. The results show that reasonable estimates can be obtained in terms both of ground motion time histories at the only available strong motion station and of spatial distribution of peak ground motion parameters, as compared to the regional map of macroseismic intensity and to the predictions of attenuation laws. The numerical model is, then, used to provide insights into 3D site effects occurring in the city of Thessaloniki, by showing the comparison between synthetic and experimental Standard Spectral Ratios (SSR) as well as the effect of non-linear visco-elastic soil behavior and the spatial variability of amplification factors with respect to outcrop bedrock basement. The results of this study demonstrate the potentialities of 3D physics-based numerical modelling for deterministic-based seismic hazard assessment studies in large urban areas characterized by complex geological configurations, such as the Thessaloniki area
Issues of Geotechnical Engineering and Soil – Monument Interaction
No full textBouckovalas G., Gazetas G., Pitilakis K., Konstantopoulos I., Kavvadas M., Anastasopoulos I., Dimitriadi V., (2009). “Issues of Geotechnical Engineering and Soil – Monument Interaction”. Co‐financed by the European Centre on Prevention & Forecasting of Earthquakes (E.C.P.F.E.) and the Earthquake Planning & Protection Organization of Greece (E.P.P.O.
Systemic seismic risk assessment of road networks considering interactions with the built environment
No full textThis article presents an integrated approach for the probabilistic systemic risk analysis of a road network considering spatial seismic hazard with correlation of ground motion intensities, vulnerability of the network components, and the effect of interactions within the network, as well as, between roadway components and built environment to the network functionality. The system performance is evaluated at the system level through a global connectivity performance indicator, which depends on both physical damages to its components and induced functionality losses due to interactions with other systems. An object-oriented modeling paradigm is used, where the complex problem of several interacting systems is decomposed in a number of interacting objects, accounting for intra- and interdependencies between and within systems. Each system is specified with its components, solving algorithms, performance indicators and interactions with other systems. The proposed approach is implemented for the analysis of the road network in the city of Thessaloniki (Greece) to demonstrate its applicability. In particular, the risk for the road network in the area is calculated, specifically focusing on the short-term impact of seismic events (just after the earthquake). The potential of road blockages due to collapses of adjacent buildings and overpass bridges is analyzed, trying to individuate possible criticalities related to specific components/subsystems. The application can be extended based on the proposed approach, to account for other interactions such as failure of pipelines beneath the road segments, collapse of adjacent electric poles, or malfunction of lighting and signaling systems due to damage in the electric power network
3D numerical modelling of the seismic response of the Thessaloniki urban area: the case of the 1978 Volvi earthquake
Full text linkThis study aims at showing the numerical modelling of earthquake ground motion in the Thessaloniki urban area, using a 3D spectral element approach. The availability of detailed geotechnical/geophysical data together with the seismological information regarding the relevant fault sources allowed us to construct a large-scale 3D numerical model suitable for generating physics based ground shaking scenarios within the city of Thessaloniki up to maximum frequencies of about 2 Hz. Results of the numerical simulation of the destructive MW6.5 1978 Volvi earthquake are addressed, showing that realistic estimates can be obtained. Shaking maps in terms of ground motion parameters such as PGV are used to discuss the main seismic wave propagation effects at a wide scale.</jats:p
Impact on loss/risk assessments of inter-model variability in vulnerability analysis
No full textFragility curves (FCs) constitute an emerging tool for the seismic risk assessment
of all elements at risk. They express the probability of a structure being damaged beyond a
specific damage state for a given seismic input motion parameter, incorporating the most
important sources of uncertainties, that is, seismic demand, capacity and definition of damage
states. Nevertheless, the implementation of FCs in loss/risk assessments introduces other
important sources of uncertainty, related to the usually limited knowledge about the elements
at risk (e.g., inventory, typology). In this paper, within a Bayesian framework, it is developed
a general methodology to combine into a single model (Bayesian combined model, BCM) the
information provided by multiple FC models, weighting them according to their credibility/
applicability, and independent past data. This combination enables to efficiently capture
inter-model variability (IMV) and to propagate it into risk/loss assessments, allowing the
treatment of a large spectrum of vulnerability-related uncertainties, usually neglected. As
case study, FCs for shallow tunnels in alluvial deposits, when subjected to transversal seismic
loading, are developed with two conventional procedures, based on a quasi-static numerical
approach. Noteworthy, loss/risk assessments resulting from such conventional methods show
significant unexpected differences. Conventional fragilities are then combined in a Bayesian
framework, in which also probability values are treated as random variables, characterized by
their probability density functions. The results show that BCM efficiently projects the whole
variability of input models into risk/loss estimations. This demonstrates that BCM is a
suitable framework to treat IMV in vulnerability assessments, in a straightforward and
explicit manner.Published723-7464.1. Metodologie sismologiche per l'ingegneria sismicaJCR Journalope
Application of stress test concepts for port infrastructures against natural hazards. The case of Thessaloniki port in Greece
No full textAn engineering risk-based methodology for stress testing critical infrastructures is introduced and applied to the port of Thessaloniki in Greece exposed to seismic, geotechnical and tsunami hazards. The methodology workflow consists of four phases: Pre-Assessment, Assessment, Decision and Report phase. In the pre-assessment phase, all the necessary information is collected and archived. For the pilot study, the inventory includes the main port components namely buildings, waterfronts, cranes and the electric power system. Generic or site-specific fragility models are used for all exposed elements and considered hazards. Risk metrics and objectives are defined related to the functionality of the system and the structural losses. In the first level of the assessment phase, the performance of each component is evaluated using a risk-based approach. Then, a system level probabilistic risk analysis is conducted separately for earthquake and tsunami hazards. A complementary scenario-based risk analysis is carried out aiming to investigate the impact of site-specific response and extreme seismic events to the performance of the port. In the Decision phase, the results are compared with predefined objectives to decide whether the infrastructure passes, partly passes or fails the test. Guidelines and strategies to improve the performance and resilience of the port are summarized
PERPETUATE Project: the proposal of a performance-based approach to earthquake protection of cultural heritage
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