The Research On Arch Centering Cantilever Technology And Early Crakes Of Concrete Arch Rib

The cantilever construction method is widely used in the valley for its mature technology. It is the key technology to control cable tension, set arch camber and design the arch placement program.Based on a certain bridge in Guizhou Province, this article does some research on the cracks appearing in the early web during the cantilever construction. Main tasks are:1 Verify cable elastic-rigidity strut method its scientificity by the comparative study and analysis on the cable forces during the process of cantilever construction. Study the setting of temporary buckle cable program based on the method and conduct a feasibility study program through the finite element method.2 Analyze the stiffening of floor and arch during the web casting process through the finite element method. The analysis shows that the stiffness ratio between arch and floor is lto 288, the arch bears 43.71% of the load frame and the floor bears 56.29% during the web casting process.3 Do numerical value analysis on the deformation of the arch and floor during the web casting process through the finite element method. The analysis shows that the web plate is easily to crack in the interval L/4-3L/8 and 5L/8-3L/4 for the gap effect between the floor and the arch during the web casting program implemented one section after another, so it is optimally designed on the length of the web longitudinal section.4 Study the reason why the concrete web cracks in the early stage. Deduce the temperature shrinkage stress formula of catenary arch ring web through the arc coordinates according to long concrete wall thermal stress formula.5 Study the temperature shrinkage stress in the early stage of the casting web with the theorical formula and the finite element method. It is found that the main reanson results in the cracks is the early average temperature drop and shrinkage in the cross section of the web plate.6 Probe into the control effect on the web cracks by the back strip with the finite element method according to the project background. It shows in the study that it can avoid the cracks with the principal tensile stress of back strip and reasonable distance mode in the early web casting stage.