Study On Interaction Of Vehicle And Train Of Unity Of Road And Railway Viaduct

The unity of the rail transit and road urban viaduct has the advantages of making full use of land resources,saving building construction and beautiful appearance.With the development of city,this new viaduct will be increasingly popular.Different with the general rail-road dual using bridge,the upper highway beam is much wider than the lower railway beam in this new viaduct.The viaduct is inverted-trapezoid,the highway beam may appear twist phenomenon under the vehicle load,which may lead to huge vibration and affect the comfort and safety of the subway train on the railway beam.Secondly,the vehicle on highway beam may be affected by the subway train on railway beam,which can also affect the vehicle driving comfort.Thirdly,this new viaduct is usually located in the downtown city.When the subway train and the vehicle act on the viaduct at the same time,the bridge structure noise caused by structural vibration is also a big problem.The above three negative factors could be an impediment of extending this new bridge.In this thesis,the interaction of the subway train and the vehicle is mainly discussed and the driving comfort problems of the subway train and the vehicle are also researched.For the reason of that the structure noise study is on the base of structure vibration and the time is urgent,the structure noise is not researched at present.In view of the existence problems,a unity of the rail transit and road urban viaduct is studied in this thesis.On the base of the real measurement results,the finite element viaduct mode is built.The 7 degrees of freedom mode and moving load series are used to simulate vehicle on the highway beam,and the 17 degrees of freedom mode is used to simulate subway train on the railway beam.The interaction of wheel/rail is simplified as Hertz theory.The equation of vehicle-bridge is solved by the separated interaction method and different operation conditions are divided.Several problems are discussed as follows:(1)the influences between the subway train on the lower railway beam and the vehicle on the upper highway beam are analyzed;(2)the comfort problems of the subway train and the vehicle are researched;(3)the displacement responses of the highway beam and the railway beam under different irregularity grade are also studied.After all,some useful conclusions have been made:(1)In the general working condition and the most unfavorable conditions,the interaction between vehicle and subway train is insignificant.So,when designing this unity of the rail transit and road urban viaduct,we can refer to the structure type used in this thesis.And the highway beam and the railway beam can be designed independent.(2)In view of the vehicle on the highway beam,the irregularity of the road is the most important exciting source.When the vehicle is passing the viaduct at the speed of 20m/s and the irregularity of the road is better than B grade,the driving comfort can be kept in good condition;but when the irregularity of the road is inferior to C grade,the driving comfort is bad.In view of the subway train on the railway beam,when the subway train is passing the viaduct at the speed of 20m/s and the irregularity of the rail is better than 4 grade of America standard,the driving comfort can be kept in good condition;but when the irregularity of the rail is inferior to 3 grade,the train will have a strong vibration and the driving comfort is bad.(3)When the highway beam irregularity grade is considered respectively as no irregularity,A,B and C grade and the heavy vehicle fleet pass through the viaduct by only one side,the deflection of the middle of highway beam span is increasing with the irregularity grade becoming worse.The deflections are similar in no irregularity,A and B grades;but when the irregularity grade is C,the deflection increased by 24.2% compared to the condition of no irregularity.So,maintenance of pavement roughness is useful to reduce the response of bridges,extend the bridge life and ensure the normal use.(4)When the track irregularity grade is considered respectively as no irregularity,3,4,5 and 6 grade,the deflections of the railway beam span are similar.So,when we calculate the deflection of the railway beam in designing,the track irregularity can be ignored.