TOWARDS FLOOD RESILIENCE OF TRANSPORTATION NETWORKS: Bridge fragility modelling and design.

In recent years, communities have been coping with increasing extreme weather events such as floods, hurricanes and storms as a result of global warming and growing urbanisation. These natural hazards lead to damages, loss of functionality, potential casualties, and direct and indirect economic crisis. Community’s flood resilience strongly depends on the transportation network functionality, which in turn lies on the capacity of its roadway and railway bridges. Worldwide bridge failures (USA, 2018; England, 2019; China, Italy and Japan, 2020; South Africa and Wales, 2021) have shown the cascading effects on communities, such as isolation, due to a lack of redundancy. Considering that each country is responsible for a large number of riverine bridges, an efficient flooding risk assessment framework for portfolio of bridges is advisable and currently lacking. Various studies and projects have investigated the estimation of flood risk effects on transportation networks; however, fragility functions and hindcasting of network analyses with disaster data are lacking.This research project aims at estimating how flood-induced damages of bridges affect a transportation network using risk and reliability analyses. Considering the four key elements of infrastructure resilience, namely resistance and reliability of structures, redundancy, response & recovery capacity, this project will develop a framework and tools to: i) identify the bridge classes in several UK counties; ii) derive archetype riverine bridges for developing damage curves; iii) develop flood fragility and vulnerability functions for the archetypes derived under realistic flood scenarios; iv) understand the available redundancy in a transportation network after an event occurred, and thus supporting local authorities and infrastructure owners in decision making such as safely re-reouting of vehicles. The methodology emerged could also be adapted to other flood-prone countries’ reality.This project includes four Stages, in particular: in Stage 1, the bridge population is identified based on several bridge databases of UK counties and asset owners; in Stage 2, archetype riverine bridges are derived grouping structures with similar flood performances; Stage 3 focuses on the development of flood fragility and vulnerability functions for each archetype bridge through numerical simulations, also considering ageing of the structures, and both fragility and vulnerability functions will be validated using data collected from past events; Stage 4 sees the integration of the outputs of the Stage 3 with existing roadways flood vulnerability functions available from the literature within a GIS-network based analysis framework for transportation network analyses, as shown in the attached figure. Please, feel free to contact us for further info.