成贵铁路宜宾金沙江公铁两用桥主桥钢箱系杆拱桥设计

Design of Bowstring-Type Main Bridge with Steel Box Arch for Yibin Jinshajiang River Rail-cum-Road Bridge of Chengdu-Guiyang Railway

成贵铁路宜宾金沙江公铁两用桥为山区公铁合建桥梁,主桥为(116+120+336+120+116)m双层桥面拱桥。336 m主拱采用拱墩固结、拱梁分离的钢箱系杆拱,拱轴线为抛物线,矢跨比为1/3.36,拱肋采用钢箱结构,2片拱肋中心间距28.5 m。上层铁路桥面采用箱形边主梁、纵横梁体系的正交异性整体钢桥面板,主梁边箱内高3.0 m,内宽1.4 m;下层公路桥面采用工字形边主梁形式的正交异性板钢桥面;铁路桥面、公路桥面分别采用刚性吊杆和柔性吊索与拱肋连接,柔性吊索内穿铁路刚性吊杆。主桥基础采用3.4 m钻孔灌注桩,桥墩分为立柱与墩身两部分,上层立柱支承铁路主梁,采用预应力横梁相接,下层墩身支承公路主梁及主拱,采用钢筋混凝土横梁相接。采用空间有限元软件对该桥进行结构静力、稳定性分析,结果均满足设计要求。

The Yibin Jinshajiang River Rail-cum-Road Bridge of Chengdu-Guiyang Railway is an arch bridge with two levels of decks accommodating roadway and railway traffics.The bridge has a main span of 336 m,two spans of 120 m and two spans of 116 m.The main arch,which spans 336 m and consists of two steel box arch ribs that are transversely spaced at 38.5 m,is fixed with the piers,rather than the decks,forming a steel box bowstring arch bridge.The arch axis is a parabolic curve,with a rise-to-span ratio of 1/3.36.The upper railway deck adopts the integral orthotropic steel deck supported on a frame formed of box edge beams,stringers and cross beams,the inner dimension of the edge beam measures 3.0 m deep and 1.4 m wide.The lower roadway deck is also an orthotropic steel deck,but supported on I edge beams.Both the railway and roadway decks are connected with the arch ribs via rigid suspenders and flexible hanger cables,respectively,the flexible hanger cables carrying the lower roadway deck are threaded through the rigid suspenders on the railway deck.The foundations are composed of bored piles of 3.4 m diameter.Each pier consists of upper pillars and lower shafts,where the upper pillars are connected by a prestressed concrete cross beam that supports the railway deck,and the lower shafts are connected by a reinforced concrete cross beam that carries the roadway deck and the main arch.The static performance and stability of the bridge are numerically simulated by spatial finite element software,which are proved meeting the design requirements.