Three Prestressed Continuous Beam Bridge System Cantilever Construction Control Technology

With the rapid development of China railway in recent years, especially the construction summit of a new round of passenger dedicated line coming, the application of pre-stressed concrete structure in China railway project has become more and more widespread, hence the research of construction for pre-stressed concrete structure is of great importance in promoting Chinese pre-stressed technology。This paper will take over-crossing airport expressway of Zhengzhou-Wuhan passenger dedicated line and Beijing-Guangzhou continuous girder with single box and cabinet, inclined web plate, changing height and cross-sections as an example, in order to systematically research the construction technology of cast-in-situ continuous girders in terms of three pre-stress systems。This thesis starts by introducing the development status and tendency of cantilever construction at home and abroad, and then combines the project general situation of Beijing-Guangzhou continuous girders, and then elaborately designs the construction method statement of this project by adopting light-triangle hanging basket and proposing the concept of anchor longitudinally moving with hanging basket, in addition, the comprising structure of hanging basket is introduced by the method of trial pressing, and then the bearing capacity as well as stress performance are tested, which provides reference basis for the setting of formwork and elevation during concrete construction in further stages; in the aspect of pre-stress tensioning, the preparatory work before tensioning, the manufacture of steel strands, the tensioning sequence, the tensioning stress and calculation of extension length, the tensioning procedure as well as items to be paid attention to during tensioning are researched in detail. At the same time, the stress channel frication loss during tensioning is tested and determined, and this testing result provides reliable assurance for stress tensioning reaching designing requirements.Furthermore, the construction technology in closing segment is massively researched, based on the setting principle of'concreting under low temperature, pulling and staying', the construction sequence in closing segment is determined. During construction, a series of measures are adopted to provide assurance for the smooth construction in closing segment, such as optimizing the design of mix proportion, establishing accurate temperature field in advance, strengthening the monitoring of all technical indexes during construction course. In the example adopted in this thesis, the pre-reserved foundation bolt and the technology of '工'-type steel skeleton welding with steel stiffness are used to effectively handle a series of problems during locking. The specific practice in this project demonstrates that all measures used during closing construction are practical and feasible, as well as easily operated, so these measures are of great popularizing and applying value for the construction of similar projects.