Abstract: The 2025 National Bridge Inventory identifies approximately 39,000 reinforced concrete (RC) T-beam bridges nationwide. Of these, 1,446 bridges have superstructures classified in "Poor" condition (rated 4 or less on a 9-point scale). In Pennsylvania, T-beam bridges represent ~ 7% of the state's ~23,000 bridges, and 226 of them are classified as "Poor". Common deterioration mechanisms include concrete delamination, spalling, reinforcement corrosion, rebar debonding, and fractured stirrups.  Load rating analysis (LRA) quantifies bridge capacity to carry live loads using bridge design, construction, and inspection data. Three LRA procedures are currently in use: Allowable Stress Rating (ASR), Load Factor Rating (LFR), and Load and Resistance Factor Rating (LFR). Conventional LRA employs two-dimensional (2D) models of controlling members with distribution factors to estimate load effects, an approach that may be overly conservative.  In this research, detailed three-dimensional (3D) finite element (FE) models of three Pennsylvania T-beam bridges were developed to perform static analyses and to conduct comprehensive load rating evaluations. The 3D modeling more accurately accounted for actual structural behavior, deck participation and load distribution effects. Results are compared with existing LRAs. Additionally, this study examined four structural condition scenarios: (1) original geometry without damage, (2) current physical condition based on recent inspections, (3) severe deterioration representing potential future conditions, and (4) material deterioration with concrete and steel strengths reduced by 20% relative to design values. For each scenario, load rating analyses are performed using ASR, LFR, and LRFR methodologies with stresses induced by dead loads and Pennsylvania legal truck loads. The comparative analysis established the accuracy and reliability of 3D modeling approaches for bridge load rating and evaluated whether current posting requirements based on conventional 2D analyses are overly conservative.