ABSTRACT
Transportation lifelines play a key role for carrying out economic and strategic activities, and also immediately after a catastrophic event for allowing rescue operations. Such lifelines, which serve large geographic regions, are however characterized by a not negligible vulnerability to a variety of hazardous natural events like earthquakes, tsunamis, hurricanes and floods. Network vulnerability is generally a function of individual network component vulnerabilities: in transportation lifelines, bridges are the most vulnerable components and, in addition, they can experience structural problems due to environmental conditions and ageing.
Bridges are indeed usually subjected to humidity and temperature fluctuations, significantly exposed to chloride ions in coastal areas and CO2 in highly anthropic environments: such aggressive agents may cause extensive deterioration on their structural members over time.
Ageing involves a related improvement of bridge vulnerability and can lead in some cases to structural failure if a hazardous event – like an earthquake – occurs (Pellegrino et al. 2014; Shafei and Alipour 2014). The estimation of the structural and seismic capacity reduction induced by deterioration for existing structures is therefore a matter of recent interest due to the increasing number of ageing bridges, and the need to define rational strategies for the allocation of limited economical resources in the structural retrofit of existing bridge stocks. For such reasons, the aim of this work is to assess direct losses to a portfolio of existing bridges, taking into account deterioration as influencing parameter in the definition of bridges’ seismic vulnerability and estimate how portfolio direct losses increases over years.
