分离式双层桥面公铁两用拱桥桥面活载相互影响研究

Research on Interaction of Upper Roadway Live Loads and Lower Railway Live Loads of Rail-cum-Road Arch Bridge

为确保分离式双层桥面公铁两用桥的运营安全,以主跨336 m刚架系杆拱桥--成贵铁路宜宾金沙江公铁两用桥为背景,对公路、铁路活载作用下上、下层桥面的相互影响进行研究。采用3D-Bridge软件建立有限元模型,分析下层公路活载和上层铁路活载作用下,2层桥面的主梁变形、主要构件内力、桥面预拱度设置、铁路桥面列车走行性。结果表明:公路活载对铁路桥面变形的影响较大,计算铁路桥面的梁端转角及挠度时应同时考虑公路活载的影响;总体受力构件内力占比与对应活载占比较为接近,主梁、吊杆和吊索等构件的内力占比与对应活载占比差别较大,主要与桥面和拱肋的连接方式有关;公路和铁路活载均会引起另一层桥面变形,宜按总活载设置预拱度以减少线路不平顺;考虑公路活载时,铁路桥面列车竖向加速度增大9%,竖向舒适指标降低。

The Yibin Jinshajiang River Rail-cum-Road Bridge of Chengdu-Guiyang Railway,which is a rigid-truss tied arch bridge with a main span of 336 m,is used as a case to investigate the operation safety of the rail-cum-road bridge with two levels of decks.The interaction of the upper roadway live loads and lower railway live loads was analyzed.A finite element model was developed using 3D-Bridge software to analyze the girder deformation of the two levels of decks,internal forces in primary components,precambers of decks and train running behavior under the action of the upper roadway live loads and lower railway live loads.The results demonstrate that the roadway-deck live loads have a remarkable impact on the deformation of the railway deck,which should be considered in computing the girder-end rotation and deflection of the railway deck.The internal force proportion of the overall load bearing components approximates the proportion of corresponding live loads,while there is a big gap between the internal force proportions of the main girder,suspenders and hanger cables and the corresponding live load proportion,which can be attributed to the connection patterns of the deck and arch.Either the roadway-deck live loads or the railway-deck live loads can cause the deformation of the other deck,hence,it is better to set precambers in accordance with the overall live loads so as to prevent track irregularity.When the roadway live loads is counted,the vertical acceleration of the trains on the railway deck is increased by 9%,indicating that the vertical comfort index is lowered.