Research On Construction Control Techniques Of Long-Span Steel Trussed Arch Bridges

Due to its strong vertical and lateral stiffness, the steel truss arch bridge has become a frequently used structure spanning over wide rivers. With the development of China’s bridge heading to a longer, larger and more flexible direction, the importance of the construction control becomes more noticeable, especially in the construction of long-span steel truss arch bridge crossing gorges or canyons in mountainous area where more uncertain factors involed. In order to make the constructed bridge in consistent with design requirements, the Najiehe in Guizhou was taken as the research background. The key techniques related to long-span steel truss arch bridge construction control were studied in this thesis. The main contents are as follows:1. Three common cable force calculation method were introduced and an improved method was proposed on the basis of these existing methods. This method takes "Alignment is the first priority, cable force is secondary" as the principle in the alignment control of arch ring. This method is simple but can effectively solve the problems in the three existing cable force calculation methods.2. A finite element model of this steel truss arch bridge was established according to the manufacture coordinates. The elevations of each segment and the controlling alignment of different stages of construction were calculated to obtain the value of pre-elevation for the construction. Considering the deformation of the cable tower, stress at the base of the junction pier and arch internal force as the restriction, the application of the new method in construction control was discussed. Also,the influence caused by the temperature effect in the construction has also been analyzed.3. The difficulties in closure construction control of long-span steel truss arch bridge have been analyzed. Considering the actual construction situation, two practical schemes of closure construction have been proposed. The advantages and disadvantages of the schemes have been discussed and the closure steps and adjustment method in closure process were also introduced,The impact of different cable removal orders on the alignment and internal forces of the bridge was also analyzed.4. The reasons for construction control errors of the steel truss arch bridge were analyzed and discussed. In addition,load parameters, steel truss assembly error and closure error which affect the construction condition and finished condition of the steel truss arch bridge were also analyzed.