Research On Countermeasures Of Long-Term Deflection Of Large Span Continuous Rigid Frame Bridge

A bridge in Guang Zhou was taken as the actual background combined with elevation observation data from 2006 to open to 2015 in this paper to conduct a comprehensive evaluation of the concrete shrinkage and creep calculation model.Taking the bridge as the engineering background,the construction control measures such as: push load in the middle span,side span pressure,active settlement of side support of continuous rigid frame bridge were analyzed and calculated.According to the finite element model of this bridge,control effect of long-term deflection of bridge girder was analyzed,the initial design of long-term deflection method with external prestressed treatment was carried out.The main work and conclusions of this paper were listed as follows:(1)Taking a bridge in Guang Zhou as the engineering background,the long-term observation points of the main girder was set and the elevation of the main girder is observed regularly and the relationship between the middle span and ambient temperature was established by theoretical calculation and measured data.(2)The relationship between elevation curve and time was obtained by 8 observations,consider the temperature factor the main girder span deflection was converted by ambient temperature and the cumulative deflection value of the main beam is measured by the time of 2015.(3)The finite element model of the bridge was built by MIDAS / CIVIL and the construction phase was divided according to the design drawings the calculation parameters and calculate the load value of each stage were selected.(4)Based on the analysis of existing research results,the causes of prestress loss,shrinkage and creep of concrete are analyzed.Combined with the bridge,the parameters of the calculation method were analyzed and the appropriate calculation parameters were selected.(5)The shrinkage and creep mechanism of concrete were analyzed,and various kinds of the calculation methods of shrinkage and creep of precast concrete were listed.Combined with the measured data of long-term deflection of the bridge,the calculation methods are analyzed.According to the analysis results,JTG D62-2004 specification calculation model was the most close to the measured value.(6)The method of load balance method,push method,pressure reduction method,bearing active sedimentation method,tension reserve steel bars method and external prestress method are carried out and the appropriate deflection control method was selected by analysis and calculation.