Study On Causes Of Cracking Under Construction Of Long-Span Presstressed Concrete Continuous Rigid Frame Bridge

With the rapid development of the transportation career, the pre-stressed concrete continuous rigid frame bridge has become a competitive type of the long-span bridges with its economical and practical. But along with more and more long-span pre-stressed concrete continuous rigid frame bridges being built, the concrete of box girder have appeared all sorts of different problems of crack.The destroyed the beauty of bridges and affected the safety and durability of the structure of the bridges, so this thesis takes the the Tuojiang Bridge as background to study the long-span pre-stressed concrete continuous rigid frame bridge on the web crack under construction. The main contents are as follows:1、This thesis introduced the basic concept and the causes of formation of cracks. According to the different emphasis of the classification, it introduced the different classification methods of cracks. It focused on analyzing the vertical prestressed, the longitudinal prestressed reinforcement configuration, temperature load, the creep and shrinkage effect, the local structure of box girder and the permitted principal tensile stress. And laying the foundation for the study about cracks after.2、This thesis took the the Tuojiang Bridge as background. It induced and analyzed the result of cracks being detected in construction site, and set up the planar calculation model by doctor bridge for the plane stress anslyzing and checking.3、This thesis simulated the construction phase of the Tuojiang Bridge by ANSYS. It compared the results from Doctor Bridge and the results from ANSYS. Discussing the main factors which the Tuojiang Bridge has cracked in the construction process.For example, the vertical prestress loss, temperature gradient, the thickness of the web.And comparing the different impact of these factors for the principal tensile stress of the web.4、After reading lots of books and literature materials about controlling cracks, this thesis puts forword some measures which include the design method, the improvement of vertical prestress, the reasonable box cross section, the configuration of the reinforced and the improvement of the construction process to control the web cracks appeared on construction.