The main bridge of Hanjiang River Bridge carrying a section of the Xi'an-Shiyan High-speed Railway is a cable-stayed bridge with span arrangement of 67,70,73,420,73,70 and 67 m.The superstructure consists of prestressed concrete box girders stiffened with steel trusses,and the two are connected via PBL connectors.The concrete sections in the side spans and the pylon zones were cast in situ on scaffolds.Three construction options for the concrete box girders in the main span,including the 5 m-long-segment cantilever casting,10 m-long-segment cantilever casting and 5 m-long-precast-segment assembly,were compared from aspects of construction conditions,structural stress,vehicle loads,deck alignment,construction schedule and costs.It is shown that the 5 m-long-segment cantilever casting leads to the shortest construction schedule,but the highest costs,and the casting is restricted by the construction sites and transportation access.The segmental cantilever casting technique has been widely used in bridge engineering and proved effective in terms of low technical and quality risks.Compared with the 5 m-long-segment cantilever casting,the 10 m-long-segment cantilever casting results in higher costs,but allows a 5-month cut-down of construction time,and the related indicators,including mechanical property of the structure,train running safety and comfort,and deck alignment reach the required levels.Furthermore,considering the construction monitoring and control accuracy as well as the alignment of the bridge after completion,the 10 m-long-segment casting was finally selected for the concrete box girders in the main span.
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