Risk Control Reserch Of Walking Type Pushing Curve Steel Box Girder

With the rapid development of traffic construction,the technical difficulty and complexity of bridge construction are increasing.When the bridge span is large,crossing specific obstacles and temporary buttresses are not allowed to be set under the bridge,a new topic is proposed for bridge construction.The walking type jacking method solves this problem with its fast and safe technical characteristics,but there are still many risks and control problems in the construction of curved girder bridge.In this paper,the construction risks and control related problems of walking type jacking curved steel box girder are studied,and the relevant conclusions are obtained.(1)In view of the influence of the "coupling effect of bending and torsion" of curved girder bridge on the stress state and deformation shape effect of the bridge,relying on the background engineering,the simulation model of the whole process of pushing construction of curved steel box girder is established by using beam element and plate shell element.Through the comparison of the calculation results of the two element analysis models and the measured data,it is found that the calculation results of plate shell element are more consistent with the measured data,and more capable The "coupling effect of bending and torsion" in pushing process of curved steel box girder is reflected.Based on the analysis of the change rule of the support reaction force and deformation form of the curved steel box girder during the jacking process,it is proposed that there are risks such as transverse bridge overturning,longitudinal bridge overturning,local buckling and instability in the construction process of the walking type jacking curved steel box girder.(2)According to the theory of "bending torsion coupling effect" of curved beam,the main factors influencing the "bending torsion coupling effect" in the process of pushing curved beam are put forward,including curvature radius,cross bridge support spacing,longitudinal bridge support arrangement,main beam section form,load action,etc.Aiming at the risk sources in the construction process of walking type pushing curved steel box girder,the "bending torsion coupling effect" is carried out Parameter analysis of influencing factors shows that: the risk of transverse bridge overturning is greatly affected by curvature radius,transverse support spacing and wind force;the risk of longitudinal bridge overturning is greatly affected by longitudinal support layout;the risk of local buckling and instability of steel box girder is greatly affected by curvature radius and longitudinal support layout.(3)According to the optimization analysis results of construction risk control of walking type pushing curve steel box girder,the anti overturning risk measures are proposed to adjust the horizontal and vertical layout of walking machine synchronously.For curved steel box girder with radius of curvature less than 300 m,stiffening ribs are added to the web and bottom of the box girder to ensure its local buckling stability.Finally,a set of collaborative risk control measures for pushing construction of curved steel box girder is formed.