Comparative Evaluation of Traffic Loads and Load Factors in the Design of Roadway Truss Bridges under International Standards

This study presents a comparative evaluation of traffic loads and load factors in the design of roadway bridges under three major international standards: AASHTO LRFD (2024), the Egyptian Code (2015), and Eurocode (EN 1991). The analysis highlights differences in lane width specifications, load model formulations, impact factor treatment, and fatigue assessment. AASHTO LRFD allows wider lanes (3.65 m) and employs independent impact factors, simplified fatigue models, and higher partial safety factors, emphasizing conservative yet straightforward design. The Egyptian Code adopts narrower lanes (3.0 m) with integrated impact effects and moderate safety factors, balancing serviceability and realism. Eurocode enforces stricter restrictions on loaded length and width, incorporates diverse load models including crowd and special vehicle loads and utilizes multiple fatigue models with moderate factors, providing high flexibility and accuracy. The study also compares tire contact areas, lane adjustment factors, and force application methods, revealing varying approaches to modeling braking and centrifugal forces. Overall, the findings illustrate the distinct philosophies of American, Egyptian, and European bridge design standards, offering insights for optimized and context-specific structural design.