Risk-based approach to selecting bridge barrier performance levels

Austroads project TT1601 – Standardise bridge barrier design aims to provide a set of standard practice design guidelines for bridge barriers and promote harmonisation throughout the Australian and New Zealand jurisdictions. This paper presents one part of the project – the development of a guideline for risk assessment and selection of the bridge barrier performance level. Current practice shows that most jurisdictions determine the required bridge barrier performance levels based on a risk assessment procedure specified in the Australian Standard Bridge Design (AS 5100.1:2004). In this procedure, the charts are provided for most site conditions; however, for site-specific, medium to high risk situations, only descriptive advice is available. As a consequence, several jurisdictions have developed their own guidelines which lead to variations in undertaking barrier risk assessments and hence may result in different barrier performance levels for similar situations. This paper presents a comprehensive procedure for undertaking risk assessment for determining bridge barrier performance levels, which can be used consistently throughout the jurisdictions. The following topics are discussed in this paper: 1. methodology and flowchart for selection of barrier performance level; 2. process to determine site condition categories; 3. chart-based procedure; 4. specifications for higher performance levels based on risk assessment and benefit-cost (B/C) analysis. Several examples are presented to demonstrate how the procedure works.