Long-term creep prediction for a PC bridge with stiffened steel truss based on field testing

To mitigate excessive long-term deflection observed in segmentally erected box girder bridges globally, engineers have proposed a novel structural form: the prestressed concrete bridge with a stiffened steel truss. Exhibiting enhanced rigidity, these bridges are particularly well-suited for high-speed rail applications, exemplified by successful implementations in northwest China. However, a comprehensive understanding of their long-term creep behavior remains a critical research gap. This study investigates a substantial four-span bridge on a high-speed railway line in northwest China as a representative case study. Utilizing in-situ concrete creep test data, a comparative analysis of the creep coefficient and classical creep models is performed. Subsequently, finite element modeling, incorporating optimized creep model parameters, is employed to analyze the long-term creep response of the reinforced steel truss prestressed concrete bridge, focusing on vertical deflection, longitudinal deformation, and prestress loss. The results indicate strong agreement between the in-situ creep coefficient and predictions derived from the ACI209 (1992) model. Finite element analysis, based on the ACI209 (1992) creep model, demonstrates that the incorporated stiffened steel truss significantly enhances bridge stiffness and mitigates vertical deflection. Furthermore, the stiffened steel truss prestressed concrete bridge exhibits reduced sensitivity to loading age and environmental humidity compared to conventional prestressed concrete bridges. These findings demonstrate that reinforced steel trusses effectively mitigate the adverse effects of creep in concrete bridge structures.