Bridges

Assessment of heavy vehicle access is a key challenge for local government in Australia which is only becoming more critical as structure assets age and the demands associated with the freight task increase. Bridge assessment in Australia has been defined using three primary Tiers of assessment by Austroads1. Tier 1 refers to line model assessment, Tier 2 assessment is capacity assessment (e.g. grillage modelling) and Tier 3 covers advanced and non-standard approaches. Refined assessments (Tier 2, Tier 3) are seen as the gold standard but often the required information to undertake this type of assessment is not available, and the assessments are costly, can produce unexpected results and are generally not feasible for wide scale assessment of heavy vehicle permit applications. Approaches that allow appropriate assessment of vehicles requesting access to the network are needed within this constrained environment.

To meet this need, the development of rapid Tier 1 line model (heavy vehicle access) assessment methods has been progressed. Tier 1 assessment involves comparison of the heavy vehicle applying for access to one or more reference vehicles which represent the capability of a bridge. Heavy vehicles are compared to the reference set based upon comparison of line model load action effects (typically bending moment, shear force, pier reaction) and are considered for access on the basis that the vehicle requesting access does not create effects greater than the reference set. Ultimately, it would be ideal if Tier 1 line model assessment could be automated to allow for fast assessment of heavy vehicle access on a route basis to reduce the administration burden associated with assessing heavy vehicle access applications. This paper will discuss the applications, challenges and benefits of using Tier 1 assessment for local governments and other asset owning organisations to assist with the decision-making processes associated with allowing heavy vehicle access to the network.