Study On Construction Control Technology Of Cable Stayed Bridge With Large Space Warped Steel Pylons

Accompanied by rapidly development progress of urbanization in China since new century,the construction scale of urban bridge was increased accordingly.Except basic traffic functions,the bridge was also incorporated into the elements of urban architecture,with more symbolic functions and cultural connotations.Great attention has been received by large-span steel pylon cable-stayed bridge with the aesthetic appeal of space modeling.Traditional technology of cable-stayed bridge construction control facing new challenges with the strict requirements on the construction accuracy of the complex-shaped cable-stayed bridge was imposed,which was affected by bridge safety and sensitivity of the aesthetics to the geometric appearance.This thesis is a study on technical problems faced by urban cable-stayed bridges with complex space modeling in the period of construction monitoring,which will enrich and develop its construction control technology.Main research achievements and results are listed as follows:To obtain the geometry state control data in manufacturing and erection of cable-stayed bridge with large space warped steel pylons,a three-dimensional finite element model with combination of shell elements and beam elements was established.The manufacturing geometry state of pylon was calculated based on the life-and-death element technology.While reviewing the geometry state of erection,the weight influence of current segment should be taken into consideration.So does the manufacturing geometry influence and the pre-camber of the lane load while calculating the unstressed length of the cable,in addition,the adjustment range of unstressed length also should be checked.The rapid positioning of the three-point segment space,and long-distance measurement of the surface coordinates of the "double prism" shaped member,as well as the height difference measurement of "ground vertical elevation transmission plus port positive and negative pressure transmitter" were the main measurement techniques of warped steel pylon geometry state proposed in this thesis.The ratio between deduced point difference and maximum threepoint difference was 1.5,the additional standard deviation of surface coordinate measured in long-distance was 0.94 mm by "double prism" shaped member,and the standard deviation of the tilt port elevation measured in the range of 200 m height difference is 1.64 mm.The accuracy requirements of the axis deviation of the background bridge steel tower is less than H/4000 and height deviation should not more than 20 mm was realized with the combination of control methods.The method proposed in this thesis was that combine manufacturing deviation of the segment to be erected and the erecting deviation of installed segment with dynamic prediction and error optimization of the steel frame.3D model drives whole process,and the deformation correction module constructs the objective function which based on the minimum deviation of the feature point distance,to avoid the defects that virtual pre-assembly only takes unstressed state into consideration which leads to the fail prediction of in the field erection,BFGS quasi-Newton optimization algorithm was used to find the optimal segment to be erected;The erected segment error after welding was in the scope of prediction module consideration,the deformed plane was fit with the least squares method,and set the optimization constraints parameter based on the connection port matching error in the local coordinate system constructed in the fitting plane with the minimum objective function,BFGS quasi-Newton optimization algorithm was used to predict the segment to be erected and reprocess the segment based on the space deviation.Based on analytical algorithm,the corner pad height can be calculated by error adjustment module accurately in order to realize axisadjustment of upper port.An accurate cutting calculation method for the space-warped closure segment that considers the erection deviation of the closure port was proposed in this thesis,which follows the optimal matching gap principle.To obtain the optimization model dived by the internal penalty function method and to calculate ridge line cutting length of closure segment accurately,objective function with distance between characteristic points of closure port to ridge lines of closure segment was constructed,and the constraints of the erection deviation of the closure segment were satisfied.The key influencing factor was the temperature field indicated by the analysis of deformation sensitivity of the background bridge closure port,and closure time was determined by correlation analysis of the temperature field and deformation with 72 hours' measured data.The temperature influence correction method of the cutting length was proposed based on weather forecast and the correlation analysis between temperature field and ambient temperature.The steel pylon closure with zero additional stress and high precise came into fact due to closure segment cutting calculation method with the spatial fitting based on the coordinates of the multi-feature point of the 8 ridge lines.In terms of the problem that the anchor bar force of locking function of the background bridge deviating from the expected in temporary anchorage system composed of “permanent bearings +temporary bearings + anchor bars”,the special physical parameters of the temporary anchorage system were tested.The deformation of the bearing plate satisfies the characteristics of the spatial flat plane assumption was proved by the data,as well as the plane fitting correction coefficient was ₍6?95?=0.9320.Based on the spatial plane assumption and the displacement method to construct balance equation,the vertical bearing stiffness parameters of the permanent and temporary bearings was identified.The results indicate that the compression stiffness of the permanent and temporary bearings are 30083kN/mm and 3370kN/mm respectively,and the compression modulus of the permanent bearing is 8278 MPa.Adjustment of background bridge construction step was made in order to ensure reliability of the locking effect of the anchor bars,which turn out to be necessary and effective from theoretical calculations and measured datas.In addition,the influence of the actual stiffness parameters should be taken in to consideration while controlling the geometry state of the pylon.