A Network-Based Importance Measurement Index for Bridge Security Risk Assessment and Prioritisation

In the related literature, conventional approaches to assessing security risk and prioritising bridges have focused on unique characteristics. Although the unique characteristics appropriately reflect the economic and social consequences of failure, they neglect the consequences of a bridge failure at the network level. If network owners and operators prioritise bridges solely based on their unique characteristics, bridges with low object-level importance and high network-level importance have very low chances to get priority. In this paper, a bridge importance measurement index α(e) has been presented, prioritising bridges based on their unique characteristics, location and network topology. To describe how to use this index α(e), three numerical examples were provided. While the first example was related to a simple hypothetical network, the second and third examples were real networks related to the bridges of Wroclaw city. Using these examples, the results of bridge prioritisation obtained in the unique-characteristics-only state were compared to the state in which α(e) had been used. Results showed that considering the location of the bridge and the topological characteristics of the network change the bridges prioritisation. For instance, in the second example, it was observed that the use of the α(e), made bridge Bolesława Krzywoustego the essential bridge, while bridge Grunwaldzki was the essential bridge under the previous prioritisation made by researchers. However, the results of the third example showed that bridge Milenijny, which was considered the essential network bridge as stated in the previous prioritisation made by researchers, was again selected as the most critical bridge based on the α(e).