Research On Key Technology Of Construction Monitoring For Long Multi-span Continuous Beam Bridge With Corrugated Steel Webs

Prestressed concrete composite box girder bridge with corrugated steel webs is a steel-concrete composite structure bridge that has gradually emerged and developed rapidly in recent years.It is favored by bridge designers for its advantages of light weight,strong spanning ability and convenient construction.However,due to its novel structure,the stress mechanism between corrugated steel webs and concrete is not very clear,which puts forward higher requirements for the monitoring work in the construction process.Especially for long-span multi-span continuous beam structure,due to the long construction period and many accidental factors affecting bridge construction,it is more challenging to monitor it.In this thesis,a typical long-span multi-span continuous girder bridge with corrugated steel webs-the main bridge of Zhaojun Yellow River Bridge is taken as the engineering background,and its construction monitoring process is studied.The main research contents and conclusions are as follows :(1)Refer to a large number of relevant literature at home and abroad,the structural characteristics,development history,construction methods and monitoring research results of prestressed concrete composite box girder bridge with corrugated steel webs are elaborated in detail.Through comparative analysis,the construction control method and structural analysis method suitable for the bridge are determined.The bridge model is established by Midas / Civil finite element software,and the synchronous ectopic construction process is simulated and analyzed.The analysis results can provide numerical support for subsequent monitoring work.(2)In view of the long-span and multi-span characteristics of the bridge,different closure schemes are simulated and analyzed by finite element model.Comparing the vertical cumulative displacement of the main beam,the stress of the roof and floor and the longitudinal displacement of the bearing under different closure schemes,and combining with the actual situation,it is concluded that the order of closing from both sides to the middle is the best closure scheme.(3)The sensitivity analysis of each design parameter is carried out.By comparing the influence of each parameter on the structural deformation,it is concluded that the concrete bulk density and the prestressed tension control force are the main design parameters of the bridge.The process of parameter identification using the least square method is described in detail,which provides a theoretical basis for the later implementation of adaptive control.(4)The monitoring analysis of the maximum cantilever deformation of the main beam under the action of sunshine temperature difference shows that when the daily temperature difference reaches 15 °C,the vertical displacement of the maximum cantilever end can reach 24 mm.It shows that the long-span corrugated steel web prestressed concrete composite box girder is sensitive to temperature change,and the influence of temperature change on the structure should be paid attention to when monitoring its construction.(5)Guided by the results of simulation calculation and analysis,the whole process construction monitoring of the main bridge is carried out,and the whole bridge construction monitoring scheme is put forward.It can be seen from the monitoring of the main beam alignment during the system transformation and the external beam tension stage that the deflection deformation value of the main beam is basically consistent with the theoretical calculation value,but the measured values are less than the theoretical calculation values,indicating that the actual stiffness of the composite box girder with corrugated steel webs is greater than the model simulation stiffness.Through the comparative analysis of the monitoring measured data and the theoretical calculation data,it can be seen that the elevation of each section of the main beam and the stress of the key section meet the design requirements during the construction process and after the completion of the bridge,indicating that the bridge structure is always in a safe and controllable state during the whole construction process.The main bridge of Zhaojun Yellow River Bridge is in good condition after completion,and the alignment and internal force are in line with expectations.It shows that the construction monitoring scheme of this bridge is reasonable and the practical results are ideal.The conclusions can provide reference for the design and construction monitoring of this type of bridge.