Resilience metrics for transport networks: a review and practical examples for bridges

Climate change, diverse geohazards and structural deterioration pose major challenges in planning, maintenance and emergency response for transport infrastructure operators. To manage these risks and adapt to changing conditions, well-informed resilience assessment and decision making tools are required. These tools are commonly associated with resilience metrics, which quantify the capacity of transport networks to withstand and absorb damage, recover after disruption and adapt to future changes. Several resilience metrics have been proposed in the literature, but there is lack of practical applications and worked examples. The aim of this paper is to fill this gap and provide engineers and novice researchers with a review of available metrics on the basis of the main properties of resilience (robustness, redundancy, resourcefulness and rapidity). The main steps of resilience assessment for transport infrastructure such as bridges are discussed and the use of fragility and restoration functions to assess the robustness and rapidity of recovery is demonstrated. Practical examples are provided using a bridge exposed to scour effects as a benchmark. An illustrative example of a system of assets is provided and different aspects of resilience-based decision making are discussed, with the aim of providing a comprehensive, yet straightforward, understanding of resilience.