AbstractLoad distribution factor for truck loads is a key parameter in evaluating the load-carrying capacity of existing bridges. This study aimed to investigate load rating procedures for reinforced concrete bridges using the tools of numerical analysis. In this study, three-dimensional finite-element modeling was used to estimate shear and bending moment demands and capacities for a sample of 10 (five flat slab and five T-beam) reinforced concrete bridges. The results were compared with those obtained using current rating procedures in accordance with AASHTO specifications. This comparison showed that the current two-dimensional analysis with the distribution factor approach resulted in lower estimates of the bridge rating, mainly due to the simplified representation of structural members and lack of consideration of the contribution of nonstructural elements. To further explore the impact of this observation, a focused parametric study was conducted to investigate the effect of geometrical features such as edge elements on moment and shear estimates. The findings confirmed the sensitivity of calculated demand considering superstructure edge elements primarily, railings, curbs, and sidewalks found in these bridges.