Bridges

There are a considerable number of culverts on Local Government Authority (LGA) road networks throughout Australia, which vary in structural form and size. These structures have been built throughout multiple historical design eras using different standards and design approaches. There is significant variation in LGA asset management practices, availability of as-built information and knowledge of existing condition of these structures. In many circumstances no as-built information is available, resulting in challenges when establishing the capability of these structures for heavy vehicle access decision making.

Load rating assessment of existing culverts can be conducted based on various methods which range from a simple load comparison (Tier 1 assessment) to a more refined capacity assessment (Tiers 2, 3 assessments). Since the latter is often time-consuming, costly and requires the availability of as-built information as well as a high level of engineering expertise, the former approach is typically preferred.

The Tier 1 approach to determining the capability of existing culverts is focused on comparing reference vehicles that represent culvert capability to vehicles requesting access. Special care should be taken, however, when implementing this methodology, to ensure it produces valid and meaningful outcomes. Factors that need to be considered include construction age, structural type and configuration, structural actions selected as a comparison benchmark, availability of as-built information, vehicle configurations and the magnitude of the compared loads.

This paper investigates the different ways culverts can be assessed for heavy vehicle access and examines the above-mentioned factors to ensure valid and meaningful outcomes. Focus has been placed on the two most common culvert types – precast pipe and box culverts – and the paper discusses factors that influence their performance and how this affects recommendations for making access decisions based on the assessment outcomes. This work has been undertaken within the National Heavy Vehicle Regulator’s Strategic Local Government Asset Assessment Program (SLGAAP).