The central pylon Z4 of main navigation channel bridge of Maanshan Changjiang River Rail-cum-Road Bridge is a spatial A-shaped steel-concrete composite structure that has four legs,every two legs standing oppositely to each other along the bridge width are connected by a lower crossbeam,and there are three tie beams in between the two lower crossbeams.No crossbeams are installed between pylon legs along the bridge length.The lower crossbeams were cast in layers on ground scaffolds that consists of steel tubes and are fitted with a formwork system.Numerical simulation was conducted to compare and optimize the layered casting plans of the lower crossbeam,and the selected plan was to cast the concrete in two layers of 2.5 m(upper layer)and 5.5 m(lower layer)thick,and the upper and lower layers were in turn divided into two and three blocks to facilitate the casting.A series of measures were taken to effectively control the cracking of the inverse arc interface of lower crossbeam and pylon legs as well as the concrete body of the lower crossbeam,including sustaining an environment with minor temperature variation,using C60 concrete that is easy to be pumped and highly cracking resistant,optimizing the inverse arc connection between lower crossbeams and pylon legs and the joints between concrete blocks,streamlining the construction process and casting organization of the lower crossbeams and tie beams,adopting intelligent concrete temperature monitoring,and choosing appropriate timing of prestressing tendons tensioning.
维普
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