Given the high seismicity in South-Eastern Europe, and Greece in particular, which corresponds to more than 80% of the seismic energy released at the European level, and the significant direct and indirect cost of damage and loss associated with a major earthquake, the development of methods and tools for the mitigation of earthquake loss is of paramount importance. This is a complex, essentially stochastic problem, not only due to the inherent probabilistic nature of earthquake itself, but also due to the complexity of modern multi-layered economy and social life, facts that render it difficult to assess in advance, quantify, manage and finally minimize the potential earthquake-induced consequences. For this reason, during the last decade, significant research effort has been made worldwide towards the development of a methodology to predict the expected earthquake losses, inclusive of structural and non-structural damage, human loss, infrastructure service disruption and indirect socio-economic cost, as a means to minimize what is called Seismic Risk, i.e., the overall Risk to elements of given Seismic Vulnerability that are exposed to certain levels of Seismic Hazard. A large number of the so-called fragility curves relating the probabilistic vulnerability of specific structural systems to seismic intensity is currently available both in Europe and the US, primarily for buildings but also for bridges ( Moschonas et al., 2009; Kwon & Elnashai, 2006 ), some of them additionally considering soil-structure interaction effects (Aygun et al., 2010 ), surface fault rupture and pre-earthquake strengthening (Kim & Shinozuka, 2004; Pinto & Mancini, 2008; Padgett & DesRoches, 2008 , 2009). Numerous earthquake loss scenarios have also been developed for many European cities (Bard et al.1995; Barbat et al.,1996; D’Ayala et al. 1996 ; Dolce et al. 2003, 2004; Faccioli et al. 1999; Kappos et al. 2002, 2008 ), all of them focusing solely on the expected loss due to building damage. In contrast to the research work on the vulnerability of buildings and bridges, significantly fewer developments have been achieved on (a) predicting the physical vulnerability of lifelines and infrastructures, including the roadway and railway networks, and (b) estimating the interdependent behaviour of buildings, lifelines and infrastructures at a system level. Given the fact that potential failure of lifelines and infrastructure may have a tremendous financial impact (i.e., Northridge, US 1994; Kobe, Japan, 1995; Kocaeli, Turkey, 1999; Chile (Maule) 2010; Christchurch, New Zealand, 2010; Fukushima, Japan, 2011), all developed societies are increasingly less tolerant to the large associated economic loss, especially during the particular period of economic instability.
Figure 1: Earthquake-induced damage in motorway systems
The proposed work aims at developing a systematic and comprehensive approach for the assessment and management of seismic risk to urban and interurban roadway networks in Greece. More specifically, a holistic methodology will be developed for the assessment of losses in the various components of the urban and interurban roadway network (inclusive of roads, motorways, bridges, overpasses, embankments and abutments, tunnels, retaining walls, slopes) exposed to the risk associated with a strong earthquake. The methodology will include development of earthquake scenarios and maps indicating the distribution of seismic action in the areas under consideration, assessment of the vulnerability of all structural and geotechnical components of the network and final assessment of the (urban and interurban) direct and indirect losses: damage to structures/infrastructures, socio-economic consequences due to network operation disruptions (road and tunnel closures, bridge serviceability and downtime etc). Once the methodology is developed, it will be implemented through a freely distributable, multi-level software for management of the data and their visualization in space within a GIS system, which will permit, among others, the identification, at a time prior to the occurrence of the earthquake, of the most vulnerable components of the network exposed to seismic risk and/or of the components whose failure is associated with a very high loss. This methodology will also facilitate the authorities in charge in setting up emergency plans for mitigating the consequences of the earthquake and rationally managing traffic flow under crisis conditions. The methodology and software to be developed will be utilised for assessing seismic risk to the urban and interurban roadway networks of the Western Macedonia Region in Greece, which has been previously struck by strong earthquakes, the most recent one being that in 1995 (Ms=6.5). These pilot applications will serve the purposes of (i) verifying and optimising the methodology and the software developed, and (ii) offering the local authorities and the companies (private or state-owned) responsible for the management of the roadway networks, vital, ready-to-use data for a more rational management of their network prior and subsequent to a major earthquake event.
More specific objectives of the proposed research are the following:
- analytical assessment of the seismic vulnerability of the main (structural, geotechnical and transportational) components of an urban and interurban roadway network, and the associated risk, inclusive of the direct and indirect (socio-economic) consequences to urban areas, using refined probabilistic models.
- development of an innovative methodology for assessing the systemic vulnerability of large roadway networks, with due consideration of the different components or subsystems and the interdependence of their earthquake-induced damage and losses.
- utilization of real or quasi-real time measurements obtained on critical network components to update the post-earthquake decision-making process related to both quick inspection and rehabilitation.
- definition and assessment of the “total value” and the “total cost” of an urban and interurban roadway network exposed to seismic risk.
- development of a new software for the vulnerability assessment (including both safety and serviceability related damage states) of the urban and interurban roadway network, with an open architecture, that can be used all over Greece, and be easily parameterized for subsequent use in other European areas as well.
- validation of the methodology developed using (free-field and on-structure) high quality measurements and earthquake records available from instrumented bridges.
- verification and optimization of the proposed methodology through the foreseen pilot study.
- development of a seismic risk scenario for the urban and interurban road network of the area studied.
- minimization, through prioritized prevention and recovery actions, carried out jointly with the authorities in charge, of the cost associated with seismic risk that can be an enormous, additional financial burden for the country, in case of a future earthquake.
It is clear that achieving these objectives requires a multi-disciplinary approach, hence the consortium set up in the framework of this proposal includes researchers (and their teams) with many years of experience in the thematic areas relating to various aspects of the proposal (engineering seismology, geotechnical earthquake engineering, structural engineering, transport planning, urban planning, and information technology). Importantly, the consortium in addition to well-established academic groups, also includes a major company (Egnatia Motorway S.A., www.egnatia.gr) responsible for the construction, operation and management, of the eponymous 680km motorway in Northern Greece, the longest in the region.