Study Of Construction Control And Deterioration Of Continuous Rigid Frame Bridge With High-pier And Large-span

Continuous rigid frame bridge has various advantages like reasonable force, greatspanning capacity, strong adaptability to the environment and comfortable driving. It isone of the mainly used bridge types in recent decades at home and abroad. However,with its increasing span and high pier, some problems of the continuous rigid framebridge have gradually appeared. For instance, the segmental elevation is difficult tocontrol during cantilever casting construction phase, the deflection increases duringoperation stage, and the web cracks, etcIn this paper, the relevant construction control theory and technology of home andabroad are firstly introduced and summarized. Then the writer uses Midas/Civil finiteelement simulation software to establish simulation analysis model according to theformal calculation method based on the engineering background, You fang gou bridge.Furthermore, structural stress and linear variation are calculated and analyzed and themechanical properties of the structure and the stability of high pier are also checkedduring the whole process of construction. Meanwhile, the writer makes detaildescription about the selection of monitoring cross section, the layout of testcomponents, and the filtering of influential factor during the construction monitoringof this bridge. The simulation analysis results are taken as the guidance of actualconstruction and carefully compared with real-time monitoring results. On this basis,the calculation method for the elevation of formwork is emphatically analyzedaccording to the grey prediction theory with the cosine curve distribution ofprefabricated camber. The influence of the line-type of built bridge when dismantlingthe temporary loads at different time is thus calculated.For the long-span continuous rigid-framed bridge, two common problems, bodycracking and serious girder downwarping, often appear. In addition, it is usuallyaffected by various factors and difficult to control. The writer, in this paper, has made adetail analysis of the factors which lead to the above two problems and summed up thereasonable measures of prevention and remedy according to relevant references. Theresults of this study show that right method of construction has a good inhibitory effectto the above two problems. What’s more, the vertical prestressing effect can beimproved because of the right method.Through the above research, due to the effects of web cracking, shrinkage andcreep and prestress loss, the mid span of long-span continuous rigid frame bridge has serious down warping and its deck forms a change of wave shape. Therefore, the writerdoes not recommend setting the pre-camber with the camber difference of long-termdeflection and the prestress according to the combination of short-term load effects onthe basis of General Code for Design of Highway Bridges and Culverts, but proposesto use cosine curve to distribute pre-camber of bridge. It can be said to be an idealprogram to dismantle hanging basket after the closure of middle span as it benefitsboth deflection of side span and mid span. The analysis shows that the verticalprestress of the wed loses seriously (persistent stress is less than60%), thus the writerdoes not recommend using vertical prestress to replace web bending tendon entirely.