Bridges

The interaction between vehicles and bridges remains a complex yet important concept in the assessment of dynamic loading on existing structures. The dynamic impact of vehicular loading on a structure is typically accounted for in the assessment procedure by the application of a dynamic load allowance (DLA) factor to the assessment load, with a factor of 0.4 specified in the Australian bridge design code AS 5100. This factor is historically based on empirical dynamic load test data. The Queensland Department of Transport and Main Roads (TMR) has adopted the AS 5100 DLA factor at its base level, Tier 1 Bridge Heavy Load Assessment Brief (2013). However it is looking to improve understanding of a family of bridges for higher-order bridge assessments when adopting dynamic load factors, accounting for various vehicles, structures and dynamic influences. This in turn may lead to a review of vehicle access and ensure efficient use of resources. To address these issues, TMR has initiated a three-year research program in conjunction with ARRB Group. This paper presents the findings from the first year of the program.In summary, the findings of a detailed literature review regarding influential factors in bridge-vehicle interactions and the background behind the currently adopted DLA factors are presented. A gap analysis has shown that little has been published regarding the dynamic impact of road trains and pneumatic cranes on bridges. Collated historical national and international load test reports revealed that various structure types, vehicle types, and materials may influence the structure’s dynamic response. A recent load test on Canal Creek Bridge in Cloncurry, Queensland, may support some of these observations. Finally, the viability of developing a vehicle-bridge interaction model for TMR use has been investigated. Further field tests will be conducted to continue to improve understandings on bridge-vehicle interactions.