Sotiris Argyroudis

Assessment of socioeconomic vulnerability to landslides using an indicator-based approach: methodology and case studies

The severity of the impact of a natural hazard on a society depends on, among other factors, the intensity of the hazard and the exposure and resistance ability of the elements at risk (e.g., persons, buildings and infrastructures). Social conditions strongly influence the vulnerability factors for both direct and indirect impact and therefore control the possibility to transform the occurrence of a natural hazard into a natural disaster. This article presents a model to assess the relative socioeconomic vulnerability to landslides at the local to regional scale. The model applies an indicator-based approach. The indicators represent the underlying factors that influence a community’s ability to prepare for, deal with, and recover from the damage and loss associated with landslides. The proposed model includes indicators that characterize the demographic, social and economic setting as well as indicators representing the degree of preparedness, effectiveness of the response and capacity to recover. Although this model focuses primarily on the indirect losses, it could easily be extended to include physical indicators accounting for the direct losses. Each indicator is individually ranked from 1 (lowest vulnerability) to 5 (highest vulnerability) and weighted, based on its overall degree of influence. The final vulnerability estimate is formulated as a weighted average of the individual indicator scores. The proposed model is applied for six case studies in Europe. The case studies demonstrate that the method gives a reasonable ranking of the vulnerability. The practical experience achieved through the case studies shows that the model is straightforward for users with knowledge on landslide locations and with access to local census data.

Fragility Functions of Highway and Railway Infrastructure

The experience of past earthquakes has revealed that highway and railway elements are quite vulnerable to earthquake shaking and induced phenomena such as soil liquefaction or landslide; damages to these elements can seriously affect the transportation of products and people in both short-term (emergency actions) and long-term period. The objective of this chapter is to propose appropriate fragility functions for roadway and railway components other than bridges that are presented separately in Chap. 9. To this end, the main typological features are summarized and a short review of earthquake damages together with damage states definitions are provided for these elements. Fragility curves from literature are collected and reviewed. In some cases these functions are modified and adapted, while in other cases new fragility curves are developed. A general procedure for the derivation of analytical fragility curves that was followed in SYNER-G is described. This approach takes into account the effect of structure geometry, ground motion characteristics, soil conditions and associated uncertainties. New fragility curves are presented for tunnels in soil, embankments, cuttings and bridge abutments based on numerical analyses due to ground shaking. Finally, the proposed fragility functions are summarized and a general scheme to identify the functionality of roadway and railway elements due to different damage levels is outlined.

Impact on loss/risk assessments of inter-model variability in vulnerability analysis

Fragility 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.

Seismic vulnerability analysis in urban systems and road networks. Application to the city of Thessaloniki, Greece

During the last decades, the aggregation of human, financial and environmental losses related to natural disasters has been increased, constituting a principal threat for the function of modern society. The present paper proposes an integrated methodology for the seismic risk management in urban areas, focused on urban planning and sustainable development. In this framework, the key elements for the urban vulnerability analysis during the crisis, restoration and especially pre-earthquake period are given.Amethod for the seismic risk analysis of urban roads is also described as the transportation network is of vital importance in case of emergency. The procedure is illustrated through a pilot application to the center of Thessaloniki city, which is an area that concentrates a variety of activities and is characterized by high seismicity. The urban vulnerability is estimated based on a value analysis of the exposed elements at risk, while the functionality of roads is evaluated after the estimation of indirect closures due to possible collapses of adjacent buildings. Keywords earthquake, risk management, road network, seismic risk, urban system, vulnerability Language: en

SEISMIC RISK SCENARIOS FOR AN EFFICIENT SEISMIC RISK MANAGEMENT: THE CASE OF THESSALONIKI (GREECE)

This paper presents the methodology developed in the framework of the RISK-UE project for the creation of earthquake-risk scenarios in urban systems. The main steps of the methodology are illustrated through an application in Thessaloniki. It is shown that RISK-UE methodology is a general and modular methodology, based on seismic hazard assessment, systematic inventory and typology of the elements at risk, analysis of their global value and vulnerability, and identification of the weak points of urban systems. The vulnerability assessment of building stock, monuments, and lifelines together with the appropriate estimations of the socio-economic consequences (debris, causalities, serviceability dysfunctions, direct/ indirect losses etc) for different earthquake risk scenarios, can operate as a valuable tool for the seismic risk management in urban areas and the development of efficient mitigation plans.

Application to the City of Thessaloniki

This chapter presents the application of the SYNER-G general methodology and tools to the case study of Thessaloniki. The application includes the building stock (BDG), the electric power network (EPN), the water supply system (WSS) and the road network (RDN) with specific interdependencies between systems. The seismic hazard model is based on the seismic zones proposed in the SHARE project (Giardini et al., Seismic hazard harmonization in Europe (SHARE). Online data resource, http://portal.share-eu.org:8080/jetspeed/portal/. doi: 10.12686/SED-00000001-SHARE, 2013). For each system, the main features for the systemic analysis and the system topology and characteristics are described. Then the analysis results are presented. They include damages, casualties (deaths, injuries) and displaced people for BDG and connectivity-based Performance Indicators (PIs) for EPN, WSS and RDN systems. Apart from the average performance and the Mean Annual Frequency (MAF) of exceedance of the PIs, the distribution of estimated damages and losses for specific events is also given through thematic maps. The significant elements for the functionality of each system are defined through correlation factors to the system PIs. Finally, representative results of the shelter demand analysis are given. They are based on a multi-criteria approach that takes into account the outcomes of the systemic risk analysis for buildings and utility systems as well as other indicators.

Seismic response of bridge abutments on surface foundation subjected to collision forces

Bridges are important components of the roadway and railway networks, as they must remain operational in the aftermath of the seismic event. Permanent movements of the backwall and the backfill soil and rotational deformations of the abutment-backfill system are well known failure modes that potentially may incite deck unseating mechanisms. However, only a few studies dealt with the modeling of deck-abutment-backfill pounding effect. In this framework, an extended parametric study was conducted on a simplified abutment-backfill analytical model. A typical seat-type abutment was analyzed using 2D nonlinear FE model in Plaxis. Simultaneously, a refined abutment-backfill model was built in commercial software SAP2000 in view to highlight significant parameters of the interaction aiming at identifying the effect of collisions on anticipated damages of the abutment. The assessment of the deckabutment-backfill response was performed on the basis of longitudinal maximum and residual movements and rotations of the abutment that may affect both the integrity and the postearthquake accessibility of the bridge. SSI effects due to the interaction of the deck with the abutment and the backfill soil were considered; analyses showed that large seismic movements during an earthquake and permanent movements of the abutment are deemed to put in danger the abutment itself, the integrity of the end spans and finally the accessibility of the bridge. Comparison of different seat-type abutment models in Plaxis and SAP2000 revealed that modeling of bridge abutments with emphasis on the geotechnical design should be properly made. Poor design assumptions may have a serious impact in the assessment of the response of the abutment-backfill-bridge system.

EVALUATION OF THE STIFFNESS AND DAMPING OF ABUTMENTS TO EXTEND DIRECT DISPLACEMENT-BASED DESIGN TO THE DESIGN OF INTEGRAL BRIDGES

Abstract. There is an urgent need for maintenance-free transportation infrastructures worldwide. Integral Abutment Bridges (IABs) are robust structures, without bearings or expansion joints that require zero or minimum maintenance. The challenge to the assessment of existing and the application of IABs is the dynamic interaction between the bridge and the backfill soil. In many cases, this interaction is misinterpreted due to the inherent non-linear behavior of the soil during the so-called in-service interaction, which modifies drastically the stresses within the backfill soil under daily displacements of the abutment. A step towards the better understanding of the seismic response of IABs is the evaluation of the resistance of the abutment, which depends upon the geometry of the abutment, the properties of the soil and the successive interactions, i.e. quasi-static, under thermal expansion and contraction of the deck, or dynamic, when the bridge is subjected to seismic excitations and/or breaking loads. Towards this end, this paper attempts to: (a) interpret the condition of the abutment and the backfill soil at the onset of the dynamic excitation based upon the antecedent in-service interaction of the components and (b) to evaluate the stiffness and the damping properties of existing and/or representative integral abutments under dynamic loads to extend the Direct Displacement-Based Design (DDBD) to the design of integral bridges. A typical geometry of the integral abutment and typical backfill soil is investigated based on 2D fully coupled FE simulations adopting a visco-elasto-plastic stress model for the soil (coupled approach) under static and dynamic loads.

Fragility Functions of Water and Waste-Water Systems

This chapter presents the state-of-the-art on the fragility models for the vulnerability assessment of the water and waste-water networks’ components. First, the main characteristics and typologies of the two networks’ components such as water sources, treatment plants, pumping and lift stations, tanks and conduits are introduced. Then, the main damage mechanisms and failure modes are summarized for each component based on the experiences from past earthquakes. A literature review of existing fragility models is performed including damage scales, seismic intensity measures and fragility functions. Finally, the fragility functions which are most suited for use in the European context are proposed, together with their parameters and relevant information.

Semi-Empirical Assessment of Road Vulnerability to Seismically Induced Slides

The present paper aims at the proposition and quantification of a semi-empirical methodology to estimate physical vulnerability of roads subjected to earthquake induced landslide hazards. It is based on a modification of the existing engineering judgmental HAZUS fragility curves using an empirical model that relates the seismic permanent ground displacement (PGD) with the peak ground acceleration (PGA) for the Newmark rigid sliding block case. In this regard, it is possible to account for the specific characteristics of soil and local topography within the estimation of road vulnerability. Various sets of fragility curves can be constructed as a function of peak ground acceleration (PGA), considering the characteristics of the slope (i.e. yield coefficient, ky) and the earthquake magnitude. A preliminary application of the proposed methodology is performed with the aid of GIS tool to the roadway system of city of Grevena in NW Greece for three different earthquake scenarios. It is observed that the level of damage predicted using the aforementioned methodology is less severe compared to the corresponding level of damage anticipated using the HAZUS methodology.