Prediction of Long-Term Deflections for High-Speed Railway Prestressed Concrete Beams

摘要

As the primary structure type of high-speed railway track girders, fully prestressed concrete beams have the merits of excellent stiffness, durability, and fatigue properties. Based on the age-adjusted effective modulus method and the linear creep theory, a time-dependent additional curvature formula is deduced based on cross section analysis, and then a formula of long-term deflection is derived through integral of the curvature along the beam span. The formula includes the combined effects of concrete creep and shrinkage, sectional stress differences between the upper and lower fibers, tendon relaxation, and non-prestressed reinforcement ratio. To verify the formula, a time-dependent finite element analvsis program was developed, and five fully prestressed concrete beams in high-speed railway were monitored under sustained loads for 1500 days. Based on the analysis results as well as the available laboratory measurements, the proposed formula was compared with other existing calculation methods and found to predict closer long-term deflection values.