SYNER-G: Systemic Seismic Vulnerability and Risk Assessment of Complex Urban, Utility, Lifeline Systems and Critical Facilities

<p>It is of great importance that traffic network is still functioning in post- earthquake period, so that interventions in emergency situations are not delayed. Bridges are part of the traffic system that can be considered as critical for adequate post-earthquake response. Their seismic response often dominate the response and reliability of overall transportation system, so special attention should be given to risk assessment for these structures. In seismic vulnerability and risk assessment bridges are often classified as regular or irregular structures, dependant on their configuration. Curved bridges are considered as irregular and unexpected behaviour during seismic excitation is noticed in past earthquake events. Still there are an increasing number of these structures especially in densely populated urban areas since curved configuration is often suitable to accommodate complicated location conditions. In this paper special attention is given to seismic risk assessment of curved reinforce concrete bridges through fragility curves. Procedure for developing fragility curves is described as well as influence of radius curvature on their seismic vulnerability is investigated. Since vulnerability curves provide probability of exceedance of certain damage state, four damage states are considered: near collapse, significant damage, intermediate damage state, onset of damage and damage limitation. As much as possible these damage states are related to current European provisions. Radius of horizontal curvature is varied by changing subtended angle: 25 °, 45 ° and 90 °. Also one corresponding straight bridge is analysed. Nonlinear static procedure is used for developing of fragility curves. It was shown that probability of exceedance of certain damage states is increased as subtended angle is increased. Also it is determined that fragility of curved bridges can be related to fragility of straight counterparts what facilitates seismic evaluation of seismic vulnerability of curved bridges structures.</p>

Due to increases in the number of inhabitants and their concentrations in densely populated areas, there is a growing need in modern society to be cautious towards the impact of catastrophic natural events. An earthquake is a particularly major example of this. Knowledge of the seismic vulnerability of buildings in Europe and around the world has deepened and expanded over the last 20 years, as a result of the many devastating earthquakes. In this study, a review of seismic risk assessment methods in Croatia was presented with respect to the hazard, exposure, and vulnerability of buildings in the fourth largest city (Osijek) in Croatia. The proposed algorithm for a detailed risk assessment was applied to a database and is currently in its initial stage.

Throughout its history, Iasi municipality has been subjected to many important seismic actions caused by earthquakes produced in Vrancea area, Romania. The impact of these extreme events upon the town increased in time as it developed, more buildings were constructed and the population density rose. The classes of buildings identified in Iasi municipality have been designed on different seismic standards, some of them being erected without taking into account the effect of seismic actions. The differences between the seismic norms’ regulations and the important earthquake’s history some of the buildings have, are outlining the need of seismic risk assessment in Iasi municipality. This paper aims to present some of the results of the seismic risk study in Iasi municipality, which was based on the completed seismic risk surveys and on the regulations of seismic standards. In this study, only the dwelling structures built before 1990 were considered, and the results were distributed on neighborhoods, for obtaining a general perspective on the seismic risk state of each area, by considering the buildings’ seismic vulnerability.

The majority of the existing seismic risk studies use a deterministic approach to define vulnerability functions, despite the well-recognized large variability in the probability of loss ratio conditional on ground-shaking intensities. This study explored a statistical framework to simulate this variability, considering the existing correlation between assets separated by a given distance. The impact that these vulnerability modeling approaches may have in probabilistic seismic risk assessment is evaluated considering three fictitious building portfolios with distinct characteristics. To this end, loss exceedance curves and average annualized losses are compared, and recommendations are drawn regarding the optimal vulnerability modeling approach.

Seismic vulnerability of industrial plants processing hazardous substances is widely documented, and thousands of such facilities are located in areas of medium to high seismicity near population centers. Nevertheless, with the exception of the nuclear industry, national or international standards do not establish any procedure for the overall seismic risk assessment of industrial process plants located in earthquake-prone areas. Moreover, existing Probabilistic Seismic Risk Assessment (PSRA) methods developed by the nuclear industry are not readily applicable to process plants. In order to overcome this limitation, in this paper a novel general-purpose PSRA method is presented, able to systematically generate potential starting scenarios, deriving from simultaneous interactions of the earthquake with each separate equipment, and to account for propagation of effects between distinct equipment (i.e. Domino effects) keeping track of multiple simultaneous and possibly interacting chains of accidents. This allows to dynamically generate damage scenarios, and to rank their risk levels determining the critical process units that can be involved.