Potential Improvement in Rating Factors of Concrete T-Beam Bridges through Refined Analysis: Evaluation of Distribution Factors

Abstract

This study explores the use of refined analysis methods to potentially increase load ratings of concrete T-beam bridges by obtaining a decrease in live-load distribution factors. The studied T-beam bridges are vulnerable to posting under consideration of the new federal regulations and when using conventional, simplified equations for load distribution factors. Finite-element models for a total of 25 in-service bridges were developed and analyzed under different vehicle loadings, including special hauling vehicles (SHVs). The effect of transverse positioning of the vehicle load on the computation of the distribution factors was also considered. The moment and shear effects in each girder were extracted and the distribution factors for the interior and exterior girders of the selected bridges were computed. These distribution factors were compared with those obtained from the AASHTO code-specified equations. The results were used to develop regression models to predict the percent change in distribution factors if a refined analysis is implemented. Furthermore, a support vector machine (SVM) is used to identify the governing truck type based on geometrical properties of bridges. Results indicate that moment distribution factors obtained from refined analysis will likely improve rating factors for SHVs, while the shear distribution factors will likely be larger.