Design of Bridge with 50 m-Long Simply-Supported Spans of U-Shaped UHPC-NC Composite Girders
This paper presents a new type of U-shaped ultra-high performance concrete-normal concrete(UHPC-NC)composite girder,which can be rapidly erected and exhibits sound structural performance and economy,leading to simplified construction and improved durability of U-shaped concrete girders.In the Chahuashan Overpass of Hezhou-Bama Expressway in Guangxi Province,the 50 m-long main span consists of U-shaped UHPC-NC composite girders,the UHPC stringers measure 3.2 m deep at midspan and grow thinner to 1.95 m at the supports,with webs of 10 cm thick in the midspan zone and localized web thickness of 25 cm,and the thickness at supports reaches 60 cm.Each stringer was divided into three sections to facilitate the girder fabrication,each and every two sections were connected by shear studs and epoxy pouring.Two UHPC stringers are composed of 12 prestressed concrete floor beams that measure 40 cm wide and 65 cm deep,and connected via cast-in-situ UHPC stitches.The deck panels consist of 7.7 cm-thick steel-NC prefabricated formwork and 16.5 cm-thick NC slabs.The structural analysis demonstrates that the shear-torsion coupling effect of the stringers and floor beams is significant,with bending dominating the midspan zone and the shear-torsion coupling effect governing the support zones,and the shear forces and torsional moments reveal an asymmetric distribution.The load bearing capacity,stability,anti-cracking performance of all the components meet the code requirements.Compared to the steel-concrete composite girder and steel box girder,the costs per unit of the U-shaped UHPC-NC composite girder were reduced by 32％and 44％,respectively,indicating sound economy.
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