The Research Of Key Problems In The Incremental Launching Of Cable-stayed Bridge With Steel Box Girder

The method of Incremental launching is widely used in the construction of prestressed concrete continuous bridges, and has made considerable progresses in recent years. However, the utilization of incremental launching in steel box girder has outpaced its theory research. In this paper, some key problems of applying incremental launching in cable-stayed bridge with steel box girder are studied and discussed, for the design and construction of bridges alike.The paper exploited some key problems such as internal force, local stress and local stability in incremental launching. We proposed a analytical model which focuses on the internal force to analyze how nose girders affects the stress of main girder and reaction of supports.Then, we integrate the conclusion of analytical model with the effective width distribution theory, and give a simple calculation method of internal force for incremental launched bridge. Based on the analysis above,the finite element method is used to analyze local stress and local stability ,as well as the effect of some parameters to local stability, which will supports the design of section structure and constructing project.Generally, the design and construction are considered separately in the process of bridge girder designing using the incremental launching construction method, and local constructional detail below construction standard can be reinforced. However, separate consideration can not fully reflect how incremental launching influences the designation of section, and increases the constructing cost. Based on the prior analysis, this paper improves the rational section pattern of bridge with flat steel box girder by adopting incremental launching method, and provides certain enlightening results for the research and engineering in this area..