Stiffening girder erection method of ground-anchored suspension bridge

Abstract

A stiffening girder erection method of a ground-anchored suspension bridge is provided. Clips for all hanger rods of a space main cable suspension bridge are installed such that design center lines of the clips are located in a vertical plane. A first stiffening girder section is installed at a position away from a first tower at a preset distance in a longitudinal direction. A second stiffening girder section is installed at a position away from a second tower at the preset distance along the longitudinal direction. A plurality of third stiffening girder sections are installed one by one in a direction respectively from the first stiffening girder and the second stiffening girder toward a mid-span until a mid-span closure is completed. An azimuth angle of a main cable around a central axis thereof at each of the clips is measured.

What is claimed is: 
     
         1 . A stiffening girder erection method of a ground-anchored suspension bridge, comprising:
 step (1) installing clips for all hanger rods of a space main cable suspension bridge such that design center lines of the clips are coincident with center lines of the hanger rods, respectively; wherein the design center lines of the clips are located in a vertical plane, such that a lateral pre-deflection angle of each of the clips is configured as a lateral inclination angle of a corresponding one of the hanger rods in a bridge complete state;   step (2) installing a first stiffening girder section at a position away from a first tower at a preset distance along a longitudinal direction, and installing a second stiffening girder section at a position away from a second tower at the preset distance along the longitudinal direction; and installing a plurality of third stiffening girder sections one by one in a direction respectively from the first stiffening girder and the second stiffening girder toward a mid-span until a mid-span closure is completed; wherein an azimuth angle of a main cable around a central axis thereof at each of the clips is measured after one or more of the plurality of third stiffening girder sections are installed; and a lateral deflection angle of each of the clips is calculated as a lateral inclination angle of each of the plurality of the hanger rods minus the azimuth angle of the main cable around the central axis thereof at each of the clips;   step (3) installing a plurality of fourth stiffening girder sections one by one respectively from the first stiffening girder section toward the first tower and from the second stiffening girder section toward the second tower until a stiffening girder is closed at mid-span; and   step (4) measuring an azimuth angle of the central axis of the main cable at each of the clips.   
     
     
         2 . The stiffening girder erection method of  claim 1 , wherein the step (4) is performed through steps of:
 measuring an azimuth angle of the central axis of the main cable at a hanger rod among the hanger rods corresponding to an uninstalled fourth stiffening girder section among the plurality of fourth stiffening girder sections; comparing a measured value and a theoretical value of a change of an azimuth angle of the central axis of the main cable at a certain stage relative to an azimuth angle before the first stiffening girder section and the second girder section are installed; modifying a prediction model of an azimuth angle change value of the central axis of the main cable at the hanger rod corresponding to the uninstalled fourth stiffening girder section; determining an adjustment of a lateral deflection angle of a clip of the hanger rod corresponding to the uninstalled fourth stiffening girder section followed by adjustment; and installing the uninstalled fourth stiffening girder section.   
     
     
         3 . The stiffening girder erection method of  claim 1 , wherein assuming that two points E and F on each of the clips in the bridge complete state are located on a tangent line of a configuration of a corresponding hanger rod at an upper endpoint thereof, an angle between an EF connection line in another state and an EF connection line in the bridge complete state is configured as a lateral deflection angle of each of the clips in the another state, and the lateral pre-deflection angle of each of the clips is a lateral deflection angle achieved during installation and adjustment. 
     
     
         4 . The stiffening girder erection method of  claim 1 , wherein the lateral inclination angle of each of the hanger rods is an angle between a tangent line of a configuration of each of the hanger rods at an upper endpoint thereof and a vertical line in a projection of each of the hanger rods on a vertical plane perpendicular to a bridge central axis in the bridge complete state. 
     
     
         5 . The stiffening girder erection method of  claim 1 , wherein assuming that an angle between a top-bottom connecting line AB of a section of the main cable in a tightened state and a line AB of a section of the main cable in a certain state is an azimuth angle of the section of the main cable around the central axis thereof in the certain state; and the azimuth angle of the section of the main cable around the central axis thereof is the azimuth angle of the main cable around the central axis thereof. 
     
     
         6 . The stiffening girder erection method of  claim 1 , wherein in step (2), the preset distance is not less than 60 times a diameter of the main cable. 
     
     
         7 . The stiffening girder erection method of  claim 2 , wherein the theoretical value of the lateral deflection angle of each of the clips is calculated through simulation analysis using a modified finite element model, a modified linear model or a modified nonlinear model. 
     
     
         8 . The stiffening girder erection method of  claim 2 , wherein in step (4), the adjustment of the lateral deflection angle of each of the clips is calculated through simulation analysis using a modified finite element model, a modified linear model or a modified nonlinear model. 
     
     
         9 . The stiffening girder erection method of  claim 1 , wherein the stiffening girder is a steel box girder, a steel truss girder or a steel-concrete composite girder. 
     
     
         10 . The stiffening girder erection method of  claim 1 , wherein a rise-to-span ratio f h /L of a plane projection of the main cable in the bridge complete state in a transverse direction is greater than 1/175.