Study on the Application of AASHTO-LRFD and SCT Standards for the Design of Prestressed Concrete Bridges in Mexico

• DOI: https://doi.org/10.22533/at.ed.3174272407112

• Palavras-chave: -

• Keywords: -

• Abstract:

  The AASHTO-LRFD (American Association of State Highway and Transportation Officials - Load and Resistance Factor Design) and SCT (Secretaría de Comunicaciones y Transportes) standards provide guidelines for the design and construction of prestressed concrete bridges. The analysis of the application of the AASHTO-LRFD and SCT standards for the design of prestressed concrete bridges in Mexico is fundamental to determine the feasibility of implementing an improved standard in Mexico. In Mexico, the application of these standards is critical due to the challenges posed by overweight truck traffic and the deteriorating state of the bridge and roadway network. The AASHTO-LRFD standard is applicable for various beam spacings and spans, while the SCT tends to take a more conservative approach, particularly in load distribution factors and design parameters.
  In this analysis, the design criteria for prestressed concrete bridges established by the AASHTO-LRFD and the SCT were studied and applied in order to evaluate their applicability in Mexico and to determine if they are adequate for the vehicular traffic and the type of roads in the country.
  It was determined that one of the main differences between the two standards lies in their load distribution factors (LDF). The SCT FDC is generally more conservative by an average of 15% compared to AASHTO-LRFD when beam spacings exceed 2.4 meters. This conservative approach results in SCT requiring more strands in the design, which can lead to higher material costs and oversized structures. In contrast, the AASHTO-LRFD considers additional factors such as geometric properties and stiffness of composite beam and slab sections, allowing for a more optimized design that leads to a reduction in materials and a decrease in time and cost of fabrication and erection of structural elements.
   
  The applicability of the AASHTO-LRFD and SCT standards was also found to be influenced by beam spacing and span length. AASHTO-LRFD is suitable for beam spacings up to 2.4 meters and spans less than or equal to 30 meters for Type A and C roads. In comparison, SCT design criteria are more restrictive, particularly for heavier trucks, which can limit the flexibility of bridge design. As beam spacing decreases, the differences in the number of strands required between the two standards decrease, suggesting that AASHTO-LRFD may be more effective for smaller spacings.
  In conclusion, while the AASHTO-LRFD and SCT standards aim to ensure the safety and reliability of prestressed concrete bridges, their different approaches to load distribution, design parameters and strength criteria highlight the need for further research and optimization. The increasing prevalence of overweight vehicles in Mexico poses significant challenges to the effectiveness of both standards, necessitating a reevaluation of design practices. Future studies should focus on integrating finite element analysis and exploring alternative beam types to improve the performance and sustainability of bridge designs in Mexico.