Bridge Assessment Beyond the AS 5100 Deterministic Methodology

Bridge assessments to AS 5100 express safety as a binary (yes/no) measure. The management of bridges deemed unsafe using this deterministic method is outside the scope of the standard. From international practice, the most holistic approach that provides quantifiable measures of safety is the probabilistic approach or structural reliability method.
This report investigates the use of probability-based bridge assessment (PBBA) as a viable option for bridge assessment beyond the AS 5100 deterministic methodology. First, the implied safety levels of a selected set of historical and contemporary bridges most prevalent in the Australian bridge inventory were obtained. Then, the current safety levels of these bridges under as-of-right (HML) road freight access were quantified. Ultimate bending and shear limit states for the superstructures were considered.
It was found that a reserve in safety exists compared to deterministic measures for some bridge designs. Further, rational asset management decisions can be based on the quantified safety metric. This demonstrates the benefit of using PBBA as the higher-tier bridge safety assessment framework. This framework provides more fit-for-purpose assessments, better utilising bridge assets, thereby facilitating an optimally productive road transport network.