Study On Long-term Operation Performance Of 56m Simply Supported Box Girder For High-speed Railway

With the rapid development of high-speed railway in China,the position of bridge in high-speed railway is becoming more and more important,and the simple-supported beam is widely used in high-speed railway.The track is not smooth due to the creep arch deformation of concrete,which will not only affect the maintenance and maintenance of the bridge in the later period,but also make the vertical vibration of the bridge aggravate the driving comfort and even endanger the safe running of the high-speed train on the bridge.Therefore,in this paper,the long-term deflection and creep deformation of a 56 m simply supported box girder of a high-speed railway are predicted by MIDAS,and the vehicle-bridge model is established based on ANSYS and UM software,and the corresponding influence of creep arch on the dynamic of the bridge is studied.The main conclusions are as follows:(1)For different prediction models of creep coefficient,the final value of Zhongtie 05 standard creep coefficient is about 1.5 times of that of Zhongjiao 04 standard.There is little difference between the creep coefficient value of the gauge of Zhongjiao 04 and CEB-FIP(1990),and the difference is about 0.1.At the same calculated age,the order of creep coefficient from large to small is as follows: Zhongtie 05 standard,CEB-FIP(1978),Zhongjiao 04 standard,CEB-FIP(1990).(2)The measured deflection data of the control section of the 56 m prestressed concrete simply supported beam bridge are basically in agreement with the theoretical data obtained by the Zhongtie 05 standard,and the error is about 1%,and there is a difference between the measured data and the theoretical data obtained by Zhongjiao 04 Code and CEB-FIP(1990),and the difference is less than 1.5mm.(3)Considering the influence of creep effect on the deflection of the beam,the total deflection of the beam is the upper arch deformation after the pre-stressed steel bundle tension is completed.As the creep increases slowly with the increase of time after the tension is completed,the deformation value of the upper arch of the beam increases slowly under the action of creep.After the second-stage dead load is applied in the subsequent construction of the bridge,the deflection of the whole beam will fall down because the second-stage dead load will lead to the deflection of the beam.However,with the development of creep,the deflection of the whole beam will increase slowly at the later stage of development.The creep gradually reached a stable state with the development of time,and after three years,the mid-span deformation of the beam tended to be stable.Numerical analysis shows that the ultimate deflection of the beam is 15.1mm,and the deformation caused by creep is 7.5mm.So the deformation caused by creep accounts for about 50% of the total deformation.(4)With the increase of time,the deflection of the beam increases slowly,and thedeformation tends to be stable after 3 years of completion of the bridge.The change value of beam deflection caused by creep effect is about 9%,and the change value of beam deflection caused by prestressed loss is about 11% of the total deformation within 3 years after completion of the bridge,and the change value of beam deflection caused by creep effect is about 9% of the total deformation.Overall,the deflection of the beam caused by loss of prestress accounts for about 10% of the total deformation.(5)With the increase of the speed,the dynamic response of the bridge increases as a whole,but not linearly,there will be a peak at a certain speed,and the corresponding peak velocities of the various responses are not the same.The dynamic responses of trains show an increasing trend,only the acceleration response of the vehicle body does not increase linearly.When the speed increases to a certain extent,it will appear a peak value.(6)When the track irregularity caused by creep arch is considered,the influence on the vertical displacement and the vertical acceleration of the bridge in the span is greater,and this effect is more obvious when the speed is larger,and the influence on the lateral response of the bridge is less.The influence on the dynamic response of the train is greater than that on the bridge.When the creep effect is considered,the vertical force of the wheel-rail increases by about 4%,and the vertical acceleration of the vehicle body increases by about one time,and the influence on the other responses is small.