昌九高铁扬子洲赣江公铁合建连续钢桁梁桥设计研究

Design and Research of Nanchang-Jiujiang High-speed Railway Yangzizhou Ganjiang Road Railway Continuous Steel Truss Bridge

昌九高铁为时速350 km的高速铁路,其南昌扬子洲跨赣江中支主桥根据通航、防洪要求跨度采用(78+134+152+134+78) m,该桥为国内首座高速铁路公铁混层合建的大跨径平行弦连续钢桁梁桥,同时该主梁为首座采用带双层挑臂的钢桁梁断面。为掌握该类型桥梁的关键技术及总结该类型桥的设计经验,开展系列研究,运用数值分析的方法,进行结构静动力分析及车桥耦合分析。结果表明:(1)带双层挑臂的钢桁梁断面具有剪力滞效应小、结构整体性强、跨越能力大、腹杆及横梁受力小、行车视野好及造价经济等优点,带双层挑臂的钢桁梁断面为公铁合建桥的适宜断面形式;(2)带双层挑臂的钢桁梁桥,墩顶处上层桥面系、跨中处上层桥面系及跨中处下层桥面系,其轴力主要由桥面板承担,分别占比为61.4%、68.7%及60.0%,墩顶处下层桥面系轴力主要由下弦杆承担,占比为72.5%;(3)带双层挑臂的钢桁梁剪力滞系数为墩顶上桥面(1.49)>跨中下桥面(1.38)>跨中上桥面(1.13);(4)带双层挑臂的平行弦连续钢桁梁桥能满足时速350 km公铁合建桥的行车运行要求,结构静动力性能良好,适用跨径能达150 m及以上。

The speed of Nanchang-Jiujiang high-speed railway is 350 km/h.The span of the main bridge across the Ganjiang River in Nanchang Yangzi Island is(78+134+152+134+78)m according to navigation and flood control requirements.This bridge is the first large span parallel chord continuous steel truss bridge built with mixed layers of highway and railway for high-speed railway in China.At the same time,the main girder is the first steel truss girder section with double cantilever arms.In order to master the key technology of this type of bridge and summarize the design experience of this type of bridge,a series of studies have been carried out,and the static and dynamic analysis of the structure and the vehicle bridge coupling analysis have been conducted using the numerical analysis method.The results show that:(1)The section of steel truss girder with double cantilever has the advantages of small shear lag effect,strong structural integrity,large spanning capacity,small force on web members and beams,good driving vision and low cost.The section of steel truss girder with double cantilever is the appropriate section form for highway railway combined bridge;(2)For steel truss girder bridges with double deck cantilevers,the axial forces of the upper deck system at the pier top,the upper deck system at the midspan and the lower deck system at the midspan are mainly borne by the bridge deck,accounting for 61.4%,68.7%and 60.0%respectively;The axial force of the lower deck system at the pier top is mainly borne by the lower chord,accounting for 72.5%;(3)Shear lag coefficient of steel truss girder with double cantilever:deck above pier top(1.49)>lower deck at midspan(1.38)>upper deck at midspan(1.13);(4)The parallel chord continuous steel truss bridge with double cantilevers can meet the running requirements of the combined highway and railway bridge for the speed of 350 km/h,and the static and dynamic performance of the structure is good,and the applicable span can reach 150m and above.