Research On Key Technologies For Construction Control Of Long Span Steel Concrete Mixed Continuous Beam Bridge Using Suspension Casting Method

Mixed steel continuous beam is widely applied in bridge construction in recent years,a new type of structure in the steel composite beam structure combined with steel structure,prestressed concrete structure of two kinds of structure forms of advantages,compared with common prestressed concrete box girder due to a part of the steel structure,the beam body weight reduction,greatly improved the girder spanning capacity.At the same time,the structure also has good economic benefits and has become one of the preferred structural forms of long span girder bridge.The structure system of steel-concrete continuous beam is complex,which generally consists of prestressed concrete beam section,steel box beam section and steel-concrete combination section.Therefore,it is necessary to establish a complex monitoring and control system in the construction process to ensure that the linear shape and internal force of the bridge reach the expected goal of the design.The main bridge of Binzhou Yellow River Bridge adopts 80m+5×190m+80m steel-mixed continuous beam.This paper takes the bridge as the engineering background to carry out research on the key technical links of construction control of steel-mixed continuous beam bridge.The main research contents and results are as follows:(1)Based on the analysis of the structural characteristics and construction technology of each component of the steel-concrete continuous beam,the difficulties in the construction control of the steel-concrete continuous beam are put forward,and the influence of the creep of concrete,prestress loss and other factors on the shape of the steel-concrete continuous beam is more significant than that of the ordinary prestressed concrete continuous box beam.The hoisting of steel box girder segment has a prominent effect on the shape of bridge.(2)On the basis of fully considering all adverse factors,the finite element model of Binzhou Yellow River Bridge is established according to the actual construction process,and the theoretical stress and theoretical deformation values of each construction stage are analyzed.On this basis,the theoretical precamper of the prestressed concrete overcast section and the steel-concrete combined section are calculated,which provides a theoretical basis for the implementation of site monitoring.The influence of steel box girder hoisting and temperature gradient effect on the forming line of steel box girder section is analyzed.The analysis results show that the influence of the two on the forming line of steel box girder section is significant,and the influence of the two must be taken into account when calculating the precamp of steel box girder section.(3)ANSYS model was established to analyze the local stress of the steel-concrete composite section in the hoisting stage of steel box girder.The analysis results show that the stress of the top,bottom and web of the concrete section is mainly compressive stress,and the stress level in most areas is between-4MPa and-15 MPa.The local tensile stress appears at the bottom of the web,but the distribution range is small.The Miss stress in most areas of the top and bottom plate of the steel section is between 4MPa～40MPa,and the maximum Miss stress is 62.17 MPa,which has a high safety reserve.(4)The ANSYS model was used to analyze the influence of temperature effect on the stress of steel-hybrid section through the overall temperature rise of 10℃,20℃,30℃and 40℃.The results show that with the increase of temperature,the maximum principal compressive stress of concrete section has a tendency to decrease,but the amplitude is small.However,the influence of temperature rise on the stress of steel section is significant,and the correlation is positive.(5)The structural characteristics of steel-concrete continuous beam are analyzed,and the detailed programs of stress and linear monitoring for different beam sections are drawn up,and the specific programs of stress,linear monitoring and jack lifting force monitoring in the process of steel box beam hoisting are specially drawn up.In the process of the construction of the prestressed concrete suspension section,according to the feedback information of the completed beam section alignment monitoring,the grey theory is used to predict the correction value of the theoretical model elevation in the next construction stage.The analysis of the measured stress and the linear monitoring data shows that the structural stress level is low in the whole construction process,and the deviation between the formed line and the theoretical line is small,achieving the expected goal of the design.Under strict construction control,the hoisting process of all steel box girder is safe and smooth,and the closing is smooth.