Design of Long Composite Box Girders with Steel Bottom Plates and Corrugated Steel Webs
The main bridge of Tongshunhe River No.3 Bridge carrying a section of the Wuhan-Songzi Expressway is a continuous girder bridge that has two superstructures arranged in three spans of 95,170 and 95 m.The superstructures,which measures 16.75 m wide each,9.2 m deep at the intermediate pier and 3.8 m at midspan and side piers,consist of single-cell box girders with steel bottom plates and corrugated steel webs that act compositely with concrete slabs via PBL connectors.To accommodate the river shores,the piers of one superstructure do not stand in line with their counterparts of the other superstructure,revealing a staggered arrangement.The steel main girders are composed of upper flanges,corrugated steel webs,steel bottom plates and diaphragms,with typical segment length of 4.8 m.The 1600-type corrugated steel webs are connected with the top flanges with double PBL connectors,and the steel bottom plates are stiffened by plate-and T-ribs.Inside the steel girders,the solid and truss diaphragms are installed.The C60 concrete slabs are 32 cm thick,containing pretensioned prestressing tendons,while the posttensioned prestressing tendons are arranged in the chamber of box girders.The steel-concrete joint section is located over the piers,the corrugated steel webs of which are embedded into the concrete webs,at the intermediate pier,the steel-concrete joint section consists of a steel chamber,shear studs and post bearing plate,while at the side piers,shear studs are installed on the steel bottom plates,and poured with concrete to encase the structure to form a steel-concrete joint transition.The main piers are portal piers,mounted on integral pile caps supported by bored piles of 2.2 m diameter.The pier-top segments and cast-in-situ segments in side spans were cast on scaffolds,and the cantilevers were assembled/cast with form travelers that did not work in parallel.The side spans were closed ahead of the central span.The numerical simulation based on the link-element model of the main bridge and solid element model of the side spans were conducted,verifying that all the indexes of the bridge meet the code requirements.
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