Enhancing Live Load Distribution Predictions for Press-Brake-Formed Tub Girder Bridges for Moments in Interior Girders: A Statistical Approach

Field testing conducted on press-brake-formed tub girder (PBFTG) bridges across various states reveals that the empirical live load distribution factor (LLDF) prediction equations recommended by the AASHTO LRFD Bridge Design Specifications ( BDS) are conservative when applied to PBFTG bridges. The paper explores the potential to enhance AASHTO LRFD BDS provisions regarding PBFTGs and their LLDFs by developing simplified yet robust prediction equations for moment in the interior beams of PBFTG bridges. The preparatory steps for estimating the prediction equations include developing rigorous three-dimensional finite-element analysis tools and benchmarking them against field implementations, as well as analyzing the live load distribution behavior of the interior girders in 19,152 PBFTG bridges. This paper provides a summary of these preparatory steps. Additionally, the paper presents an overview of the development of the proposed simplified empirical equations for predicting live load moment distribution in PBFTGs under one- and two-lane loaded scenarios, along with the validation of their improved predictions through rigorous statistical analyses. Overall, the results of this study provide strong statistical evidence that the proposed equations have superior predictive accuracy, and thus, support the recommendation for adopting these equations in AASHTO LRFD BDS Section 4. Integrating the proposed equations can substantially streamline the design process for shallow steel tub girder bridges, broadening their applicability.