Study On Structural Calculation And Safety Control Of Curved Steel Box Girder Bridge During Launching Construction

Curved steel box girder bridges have the characteristics of large stiffness,light weight,and rapid construction,and have been widely used in bridge construction in recent years.However,their curved characteristics cause difficulties in complex beam structure and difficult to control the alignment.These difficulties create difficulties in the construction process,such as various construction techniques and uneven stress on the beam.Therefore,it is necessary to carefully compare and select their construction schemes,Carry out targeted structural calculations and safety control during the construction process.In this paper,a curved steel box girder bridge crossing an expressway is taken as the research object,with the main purpose of safety construction,the selection and design of construction schemes are carried out,the simulation of construction structure calculation is conducted for the selected jacking construction scheme,and local analysis,anti overturning analysis,and construction monitoring analysis are conducted for potential hazardous conditions.Safety construction control measures are proposed.The main research contents and achievements are as follows:(1)The construction schemes of curved steel box girder bridges are compared and selected based on technical safety and economic cost as the main indicators,and the construction design of the construction scheme of the step jacking+support method is carried out.(2)According to the construction scheme settings,Midas Civil is used to simulate the structural calculation of the launching beam segment,analyze the support reaction force,deflection,internal force,stress,and other values during the launching process,judge the rationality of the construction scheme,and serve as a basis for subsequent construction monitoring and control.(3)Based on the change of the maximum support reaction during the jacking construction,the safety of the temporary pier support under the most unfavorable working conditions was explored,and the safety of the foundation bearing capacity was reviewed.(4)Conduct buckling analysis for dangerous working conditions determined in structural calculations,analyze possible local instability failures,and conduct local instability control research for possible instability points.It is recommended to use 60 cm × A 60 cm steel gasket increases the compression area of the box girder bottom plate.(5)The layout of temporary pier supports is optimized by analyzing the anti overturning stability of the launching beam section under the most dangerous working conditions.The spacing of the launching type temporary pier supports LSD1,LSD3,LSD5,and LSD7(8)along the bridge is 20 m,and the transverse bridge spacing of the launching support points is 7m.In order to reduce the risk of overturning of the beam section during the launching construction process,the axis deviation of the launching beam section should not exceed 25 cm,When the cantilever section at the front end of the guide beam is long,it is necessary to focus on monitoring LSD7(8)to avoid accidental disengagement of the jacking point here.(6)During the construction process,the displacement,stress,and axis offset of the launching beam segment are monitored and controlled during construction.The bridge construction safety is ensured through the cyclic verification process of structural calculation theoretical value prediction → construction monitoring and control →feedback control results.