Research On The Stiffening Girder Construction Method Of Long-Span Railway Suspension Bridge

Due to high stiffness requirement, large live and dead load for the long-span railway suspension bridge, steel truss structure is commonly used as stiffening girder in the bridge, which makes the bending stiffness of stiffening girder much larger than the general highway suspension bridge. For the construction of stiffening girder in the railway suspension bridge, if adopting the construction methods commonly used in highway suspension bridge, there will be a large number of troubles, such as difficulties in connecting, too large equivalent weights, unsatisfactory stability of wind resistance and so on. In order to apply railway suspension bridge in the construction of long-span bridges better, more attention should be paid on the stiffening girder erection process, which is one of the most important parts in the construction of suspension bridges. Then the suitable construction method for the stiffening girder erection of long-span railway suspension bridge could be determined, so as to ensure the safety of the construction and the quality of the bridge.In this thesis, the reasonable construction method of stiffening girder was analysed from the following aspects:(1) The characteristics of suspension bridge construction process were described, as well as the calculation methods and procedures of simulating the construction process. Several factors affecting the construction process of long-span railway suspension bridge were analysed, including the connections between the segments, the erection sequences, the installed units and the erection methods.Sling adjusting and pulling operation method of the rigid connections scheme was proposed and analytical method for determining a reasonable setting position of hinge connection in the combined rigid and hinge connections scheme was discussed.(2) The model of construction process was established with the bridge nonlinear analysis software BNLAS by taking a Strait rail-cum-suspension bridge as the research object. The construction process was simulated detailedly in three different stiffening girder connection types, including the hinge connection, the rigid connection and the combined rigid and hinge connection.The internal force, displacement, stability of wind resistance and dynamic characteristics of the structure during the construction process in three different connection types were compared. The influence of different connection types for long-span railway suspension bridge on construction process was discussed. The optimum connection types for the construction of long-span railway suspension bridge were determined. (3) The model of construction process was established with the bridge nonlinear analysis software BNLAS by taking Jinsha River railway suspension bridge as the research object. The construction process was detailedly simulated in two different construction sequences, including erection of the girder from the tower to the mid-span and erection of the girder from the mid-span to the tower.The internal force, displacement, stability of wind resistance and dynamic characteristics of the structure during the construction process in two different construction sequences were compared. The influence of different construction sequences of the stiffening girder for long-span railway suspension bridge on construction process was discussed. The optimum construction sequence for the construction of long-span railway suspension bridge was determined.(4) The parameters influencing construction process were analysed, including different railway deck systems, erection methods, etc. And then the influence of different parameters on the static and dynamic characteristics of long-span railway suspension bridge during the construction process was discussed.Based on the research of this thesis, the reasonable construction method of long-span railway suspension bridge was obtained. Research suggests that construction method of long-span railway suspension bridge is affected by many factors. In order to determine the reasonable construction method, various factors should be taken into consideration synthetically. The rigid connection or combined rigid and hinge connection between the beam segments should be adopted during the stiffening girder erection process of long-span railway suspension bridge, as well as the erection of the girder from the tower to the mid-span. The influence of different railway deck systems and erection methods should be taken into consideration during the design and formulation of construction scheme.