Creep Effects On CFT Arch-Continuous Beam Combination Bridge In High-Speed Railway

CFT arch-continuous beam combination bridges are used in high-speed railway in recent years. Especially for ballastless track on the bridge, the deflection caused by creep of CFT arch-continuous beam combination system, which has complex time-dependent behavior, increases the track irregularity and it affects the dynamic response of the vehicle-bridge system when across the high-speed vehicles. The forecast and control of concrete creep and its effect on the structure performance is very complicated and difficult to get accurate answers. The creep of concrete-filled composite arch system is poorly studied. This paper studies the creep calculation method of the combination system using real engineering bridge as the background, analyzing creep effects on concrete-filled composite arch bridge. The works of this paper are as follows:Using Model B3considering temperature effects on concrete creep, the influence of creep on structural static behavior is analyzed on the basis of the age-adjusted effective modulus method. Results show that creep lead larger deflection both of the girder and the arch, meanwhile, the stress of steel pipe and concrete also changed with time.According to analysis of the temperature effects,creep calculated by using data of monthly average temperature is slightly higher than that by annual average temperature.Creep effects on dynamic response of the composited bridge are analyzed. Results show that natural frequency of the bridge decrease after creep. The vibration modes of the structure are relatively complex. The vibration of the arch ribs and the girder can affect each other.Finally, the creep influences on track irregularity is analyzed. Change of the irregularity along track direction is small after creep, which can be neglected. But creep effect on the irregularity in vertical direction of track is rather big. So it is necessary to consider creep effect on the track vertical irregularity when study the driving safety of long-span bridges in high-speed railway.