Space Stress Analysis Of The Pier Top Block By Cantilever Construction

Large span prestressed concrete girder bridge has attracted more and more attention during middle and small span bridges, The cantilever construction constantly improves with practice, this technology is now becoming one of the preferred solution for bridge construction. The change of stress and displacement within the structure is very complex during cantilever construction, because of the influences by concrete dead weight, construction loads, prestress and temperature. As a starting point for bridge superstructure construction, the characteristic of pier top block leads to a greater obstacle to an understanding of its internal force, which has a big concrete volume, variable structure type and intensive prestressed pipes. Previous studies has limitations for the pier top block stress analysis, most of them use full-bridge truss model to calculate the stress. Based on a continuous rigid frame bridge named You fang-gou bridge, a system study for the pier top block spatial stress distribution was practiced with the finite element analysis software Midas/Civil and Midas/FEA in this article, by using a combination method of plane frame model and space entity models.This paper first introduces the characteristic of the development status for continuous rigid frame bridges at home and abroad, cantilever construction method and design elements, of which contains construction features and design principles for continuous rigid frame bridges. Secondly, the steps of the finite element analysis is expounded by taking the displacement method for example, then, the static characteristics for the full bridge model under the largest cantilever state is analyzed according to computation theory. Finally, variation of the overall internal force and displacement is found, which provides data support for the pier top block stress analysis. According to analyze the spatial stress for this bridge under the largest cantilever state again, examine pier top block overall stress distribution and study the normal stress and the principal stress on roof, webs, floor and diaphragms for pier top block, stress distribution and the most unfavorable region was found during construction process. At the same time, the stress result contributes to analyze form and location where cracks probably emerge, which provide practical engineering optimization tips. In the last part of this article, Multi-group model for parallel comparison was established to find the method for similar structure meshing and model simplification. Different pier top block stress calculated data was contrast between different models; the modeling method was verified reasonable. Recommendations were given to select the length when similar model will be established, by studying the influence for calculation accuracy when model is selected.The conclusion of this article provide data support for related project, meanwhile, the conclusion can supply reference for design of pier top block in large span prestressed continuous girder bridge, computational analysis and construction.