Development of heavy truck models and their effects on girder bridges

The traffic on highway bridges has been increasing in both volume and magnitude, which even has become one of the main reasons leading to damages and collapse of bridges. Most of the existing regulations for overloading checking are carried out based on various limits of gross vehicle weights and axle loads. However, the results of relevant researches show that weight is only a potential factor but not the dominating factor in threatening the safety of bridges. In this study, the concept of load-effect-based heavy truck is proposed for overloading checking, and then three years of WIM data were collected and used to develop heavy truck models for each truck type, based on the understanding of the characteristics and configurations of heavy trucks as well as the distribution of their main parameters. Furthermore, the typical heavy truck models selected and their possible combinations are applied to a simply supported pre-stressed concrete T-beam bridge model with three loading levels, considering one-lane, two-lane and three-lane loaded respectively, then the induced load effect, deflection and stress are discussed for 20 loading cases. The results show the bending moment caused by heavy trucks moving on multiple lanes is 1.6 times the value of the standard truck model in Chinese specification, and the eccentric loading due to a very heavy vehicle moving on single lane usually lead to more severe effect.