Research On Key Techniques Of Prestressed Concrete Box-section Bridge Casted By Movable Scaffolding System

Construction with movable scaffolding system has the advantages of industrial manufacture, standardized construction, short cycle of the construction and non-blocking traffic under the bridge, etc, so frequently applying to small and medium-span bridge. However, there are still many problems such as the economy of movable frame program, structural designing, box-girder concrete quality and shape control, etc, especially on the long span movable frame construction. In addition, the major accidents of safety and quality occur sometimes. These hardly restricted the promotion and application of movable framework on long span bridge construction.IN view of the technology situation and the problem of movable scaffolding system, based on Guangzhou zhujiang Huangpu bridge engineering, this paper focuses on the theoretical discussion and practical application about the designation and construction technique, the concrete quality control in the framework construction, the coupling effect of the long span framework and the beam's steel skeleton to be poured, grading construction technology, etc, due to improve the construction quality, reliability and economic of the movable framework construction method for the whole in-situ construction of long span prestressed concrete bridge.For Movable framework Casting in situ of the box-girder beam with 62.5m in length, this paper does the research and summary totally on the structure designation and construction technology, leading to supply the complete set of technical measures and solutions for entire in-situ construction of long span prestressed concrete bridge. According to its casting characteristics and special requirements, the optimal mix proposition optimization is designed by the method of dense proportion design, used for high frusta thin-walled box structures concrete casted by movable frame. The most appropriate mix proportion of concrete and the best dosage of the admixtures such as flash and slag are determined through laboratory experiment, theoretical analysis and monitoring in site. It helps to control the concrete cracking effectively and improving the durability of the structure and meanwhile decrease cement content. The coupling effect between the movable frameworks and the structures is investigated by the numerical simulation method, providing objective basis for shape control and the frameworks' stiffness. For the long span girder bridge, the application scope and construction capability of movable frame are enhanced significantly by means of the grading construction method at the contra-flexure point of the continuous girder, and it is frequently reused.This paper had researched on the key technique of the prestressed concrete bridge casted by movable framework, and successfully practiced on the construction of Guangzhou Huangpu bridge. It has valued significance and ensured the project mentioned in this text to complete, and offer the basis of the longest movable framework manufacturing (62.5m in standard span length,75m in the longest casting length,2650t in carrying capability), taking it into reality and forming of the system of the whole movable framework designation, manufacturing, construction and quality controlling, and also providing some manful references to establish the movable framework designing and construction guiding and normative.