Assessing bridge conditions using visual inspection following a risk-based methodology

Visual inspection of existing bridges is the main source of information to prioritize mainte- nance. This qualitative examination is thus a critical part of civil infrastructure management. In Switzerland, main inspections are typically made every five years on bridges. The bridge condition is scored from 1 (good condition) to 5 (alarming state) by inspectors. This global evaluation is taken as the worst score among bridge- element conditions that are individually assessed during the visual inspection. As these evaluations do not ac- count for the importance of this element to global structural safety, the bridge condition is often inaccurately evaluated by bridge inspectors. This paper proposes a methodology to assess the bridge condition in which bridge-element evaluations are coupled with element-failure consequences on the structural safety following a risk analysis. In this risk-based methodology, the bridge condition score typically depends on the conditions of the most important structural elements such as main girders and piers. Visual-inspection reports have been collected on a road including 60 bridges in Switzerland, and bridge-condition assessments are compared be- tween the conventional and the risk-based methods. Based on a new visual inspection made by the authors, results show that the risk-based methodology provides more accurate bridge-condition evaluations than con- ventional approaches. Inspection reports often concluded in over-pessimistic bridge-condition assessments, while the proposed methodology helps reduce subjectivity by providing a quantitative approach for bridge- condition evaluations. Additionally, the risk-based methodology supports decision-makers in the prioritization of maintenance on defective bridges through linking bridge condition value with appropriate intervention measures, thus improving asset management.