Study On The Closure Sequence And The Time Of System Transform Ation Of The Low Tower Cable-Stayed Bridge

With the development of bridge technology, In recent years, a new bridge structure has emerged between prestressed concrete girder bridge and cable-stayed bridge—low tower cable-stayed bridge. Low tower cable-stayed bridge has a dual structure characteristic of cable-stayed and prestressed concrete continuous beam bridge. It is a transitional bridge structure between flexible cable-stayed bridge and rigid continuous girder bridge. Because of its superior performance and good economic indicators, it shows great potential for development. Its structural characteristics determine that its main beam and continuous beam bridge construction method is basically the same. At present, the casting method is the main construction method, and the closure is a major part of cantilever cast. The different closure sequence and the time of system transform ation will result in different internal forces of the final dead load and different cumulative displacement of bridge, and directly affects the quality of bridge construction. Therefore, the study on the closure sequence and the time of system transform ation of the low tower cable-stayed bridge is necessary. Choose the best solution of closure is key to the design.Firstly, this article describes the origin,the development and construction method of the low tower cable-stayed bridge, Secondly, it describes the general layout, classification and characteristics of the low tower cable-stayed bridge, which provide a theoretical basis for the analysis of the low tower cable-stayed bridge, and describes common closure order and its feature, which provide a theoretical basis for the analysis of the displacement and the stress under the different closure sequence and the time of system transform ation.Finally, In this discourse, with the background of a existing bridge, to establish finite element model of a three-span low tower cable-stayed bridge with the process of the construction, analysis the structural stress and displacement of the main construction phase, the structural internal force,stress and displacement considering the constant load, all load effect, all the load effect after 10 years, the annual temperature difference, day sunshine temperature difference, the five types of load conditions. Then, by changing the closure sequence and the time of system transform ation, obtain 4 closure plan:close side span symmetrically, system transform ation, close mid-span; close side span symmetrically, close mid-span, system transform ation; close mid-span, close side span symmetrically, system transform ation; close mid-span, system transform ation, close side span symmetrically. contrastively analysis the structural stress and displacement of 4 closure plan, to provide a basis for the design and construction of future.