Study On Some Key Problems In Suspender Replacement Of Arch Bridge

Since the1990s, the suspender arch bridge has developed rapidly in our country, while because of limited technical level at that time and misuse in later period, more and more suspenders have been damaged for fatigue and corrosion in recent years. To ensure the structural safety in running periods, the suspenders of those bridges have to be replaced. The research about the process of suspender replacement is still in the primary stage for its complexity and difficulty, there is no a mature system for it. Therefore, to ensure suspender replacement process safety, the further research on the suspender replacement is very imperative.This thesis firstly introduces the types and stress characteristics of suspender arch bridge, the damage of suspenders and the status of suspender replacement are also summarized, then it studies some critical problems in the process of the suspender replacement based on the real project of Third Nanxi River Bridge. The contents of this thesis are stated as follows:1) Based on the MIDAS/Civil finite element software, a simulation method for the effective stiffness of bridge deck is proposed to solve how to accurately calculate the deformation of bridge deck and the change of suspender cable force in each stage of using bridge deck support method for suspender replacement, and this paper study the influence of the construction step on the bridge deck deformation, bridge deck rotation and the change of suspender cable force.2) This thesis analyses the influence of different suspender replacement method on the deformation of bridge deck. The maximum bridge deck permissible angle calculation method which combining angle influence matrix with design loads of the bridges and a simple monitoring method especially for short suspenders are proposed.3) Using the finite element software MIDAS researches the influence of the shock absorber’s stiffness and installation position on the suspender’s frequency and effective length, and then comes up with a suspender force calculation method through numerical fitting, which take the effect of shock absorber into consideration by modifying the effective length of suspender.4) Based on the measured data in the process of suspender replacement of Third Nanxi River Bridge, the influence of the stiffness change of the ends of suspender on the suspender’s effective length is studied, which appear in the ends of suspender, the results indicates that the value measuring this influence, for the same type of suspender, is certain.5) This thesis provide experience for the similar projects in the future by summarizing the construction monitoring process of Third Nanxi River Bridge’s suspender replacement.