The Influence Analysis Of Stiff Skeleton On The Closure Section Of The Bridge By Cantilever Construction Method

Locking device is also used to closure the bridge constructed by cantilever method.As the end-point of the construction stage, the defects is of common occurrence because of the complex forced state and external affecting factors on the closure of the large span presstressed concrete bridge.The extensive research is developed by scholars wordwide with the understanding of defects on the large span prestressed concrete bridge, especially continuous rigid frame bridge, but the experiment or numerical simulation about the influence of the types of stiff skeleton on the concrete of the closure. As a part of the western communition construction technology project--< The Detection Technique on Large and Medium Span PC Bridge>, to get the time-dependent rules of concrete stress which is impacted by the locking device exactly, the research work is developed on the change of internal forces and stress brought by the stiff skeleton basing on the structural analysis program of a continous rigid frame bridge in Shanxi Province (span arrangement:72m+120m+72m).According to analyze the influence of the skeleton stiffness on closure concrete stress, the relation cures that concrete stress varies with the steel ratio is obtained. The affected area, the differences and changes of internal forces and stress by the stiff skeleton in ten years is caculated in this paper by chosing two types of stiff skeleton as representative based on the engineering example.The stress distribution of the concrete of the boxgirder located at mid span is studied and the change of the section normal stress is compared by the basis of section internal force which is produced by the permanent action when the bridge is on the using stage. The result shows that the absorption of prestress is obvious because of the inner stiff skeleton, and this phenomenon give cause for the decrease of effective stress and the defects on closure.From the viewpoint of Designer and combined with the checking habit of design institute, the stress analysis of closure is done to forecast the risk brought by inner stiff skeleton. The result shows that the stiff skeleton has a obvious effect on the normal stress of the bottom concrete. This influence should be claimed attention in design and construction control.