Risk-based methodology to assess bridge condition based on visual inspection

The visual inspection of existing infrastructure is a critical step for asset management, as the detection and quantification of damage must be useful to prioritise maintenance. In Switzerland, main inspections are made every five years for all road bridges. For each bridge, a condition value ranging from 1 to 5 is given. As only element-based degradations are currently taken into account in bridge-condition evaluations, inaccurate assessments of global structural safety are often provided by bridge inspectors. In this paper, a risk-based methodology is introduced to evaluate bridge conditions based on visual-inspection data. Degradation states of bridge elements are coupled with element-failure consequences on the global structural safety in risk analysis to accurately assess the bridge condition. A case study of a strategic road involving sixty bridges is used to assess bridge-condition evaluations using the risk-based methodology based on recent visual inspections. The study reveals that including element-failure consequences in bridge-condition assessments supports more accurate evaluations of the impacts of damage on the global structural safety, leading to more objective decisions on asset management actions. Analyses of four damaged bridges show that inspection reports are often over-pessimistic in terms of structural damage, and this can lead to unnecessary rehabilitation interventions.