Study On The Key Construction Technology And Geometric Control Of Xijiuxi River Bridge

This thesis is based on the construction of Xijiuxi River Bridge in the Nanning-Kunming Railway, which is a continuous rigid-frame prestressed concrete bridge with spans of 56+88+56m. The main piers of this bridge are thin-walled high ones, with height of about 60m. Using free cantilever casting construction method to build , this bridge is one of the first long-span continuous rigid-frame PC bridge in China's railway. With structure in a novel style and high demands on construction, Xijiuxi River Bridge's technical difficulty is obvious, so many new technologies were employed when it was under construction. In order to offer useful references for similar structures' design and construction, it is necessary to make a systematic summary of these key techniques adopted by this bridge. Adhering to the principle of combining theory with practice, the major contents are made in this paper as follows.1. Many key construction techniques of continuous rigid-frame PC bridge such as the construction process of prestress, the technological measures of concrete, the construction of part of closure, the construction method of 0# part of the box girder, the design and application of self-anchored light traveling carriage, etc. are thoroughly expounded. Based on the engineering practice, the difficulties in free cantilever casting construction method for continuous rigid-frame PC bridge is comprehensively summarized.2. The geometric control method for free cantilever casting construction of PC girder is studied. Taking into consideration of the influence of dead and living load, the creep displacement of the beam segments casted in different times and prestress on girder's displacement, the caculating formulas of the adjustment of each beam segments during construction and the technical basis for geometric control is provided.3. In order to achieve good results on construction control of Xijiuxi River Bridge, many experiments such as the piping friction loss of prestress, thecharacteristics of concrete's contract and creep have been done. A lot of calculating factors which tally with the actual situation much more are supplied by these experiments. A wealth of material for study is accumulated and references for similar project are provided too. These experiments are thoroughly introduced in this paper.4. The practical methods for geometric and stress control during the construction of continuous rigid-frame prestressed concrete bridge are analyzed combining with the project of Xijiuxi River Bridge. The concrete accomplishment of these methods in practice and the comparison between theory and practice are introduced. A lot of conclusions which are valuable have been reached.