Study On Wind-induced Response And Safety Control Of Cantilever Casting Construction Of Hancheng River Bridge

With the growing of importance principle on base installation in China,the adhibition of large span rigid frame bridges with high piers is becoming more and more comprehensive.Majority of large span rigid frame bridges with high are built in hilly areas in the Midwest areas.The wind of hilly areas have a huge effect on the the bridge,thus threatening the safety of the bridge during the cantilever casting construction.The wind opposing security of large span rigid frame bridges with high piers during suspended casting construction should be noticed,and it is particularly necessary to study its wind characteristics.This thesis is researching for the Hancheng River Bridge on Mianchi expressway.The numerical simulation software is Fluent for the wind environment characteristics of the Hancheng River Bridge.Then,the model of the bridge and rhombic hanging basket during the cantilever casting construction is built with Midas.The simulated wind load is added to the model of the bridge and the hanging basket to research its wind environment features.The main contents are as follows:(1)The bridge model and the rhombic hanging basket model are established by Gambit,and coupled with the terrain surface.After meshing,the Mesh file is input into Fluent for simulating the surround atmosphere of the wind,and get the wind data.(2)The wind field characteristics of bridge site area in winter and summer were preliminarily studied,and the distribution law of wind field characteristics of box girders with different sections under different wind attack angles was preliminarily studied.The static force coefficient of the bridge under the condition of 0°wind attack angle is calculated,and its law is analyzed:the resistance coefficient increases from15~#to 0~#block section,and decreases from 0~#to-15~#block section;the lift coefficient increases first and then decreases from 15~#to-15~#block sections,and the maximum value basically appears in the mid-span section of box girder.The torque coefficient changes irregularly.The wind characteristic data obtained from Fluent were transformed into wind load and imported into the bridge Midas finite element model to preliminarily discuss the static wind response of box girders 1~#,8~#and 15~#during the cantilever casting construction period.The transverse and vertical bending of the bridge vibration mode occurs,and the transverse and vertical bending occurs later,indicating that the main beam is greatly affected by the construction load and wind load.(3)The wind characteristic data obtained from Fluent is transformed into wind load,and added to the Midas finite element model of the diamond hanging basket.The stress characteristics and displacement values of each component of the hanging basket under pouring and walking conditions are obtained.The small program of fluctuating wind is compiled by commercial software and input into Fluent to obtain the data of fluctuating wind environment characteristics.The wind characteristics data are imported into the finite element model of the rhombic hanging basket to obtain the wind-induced characteristics of the hanging basket under pouring conditions and walking conditions.From the analysis of vibration mode characteristics,under pouring conditions,the rhombic hanging basket swings up and down along the z direction and swings more along the x direction.Under walking conditions,the diamond hanging basket will produce large deformation along the y direction,arching along the z direction,and swinging more along the x direction.