大跨度铁路悬索桥钢桁加劲梁设计

某大跨度铁路桥位于强震山区,采用主跨1060 m的上承式钢桁梁悬索桥,主桁采用华伦式桁架,桁宽30 m、桁高12 m,节间长10 m。结合强震山区铁路悬索桥的受力特点,加劲梁约束体系采用塔梁分离、塔墩固结的半飘浮体系,桥塔处纵向阻尼器与下平联设置在同一平面,桥塔和桥台处均设置相互协调工作的横向支座与横向阻尼器,并设置地震反压结构,在桥台端横梁中央设置局部受压支座,解决了大跨度铁路悬索桥抗强震、大风作用及轨道局部平顺性问题。钢桁梁主要构件采用Q370qD钢,局部构件采用Q500qD钢,主桁杆件和联结系杆件分别采用M30和M24高强度螺栓连接。加劲梁主桁上弦杆采用箱形截面杆件、焊接整体节点,下弦杆主要采用H形截面杆件、拆装式节点;上层通过交叉平联使箱形弦杆与钢桥面组成整体断面共同受力,下层采用H形弦杆与交叉平联组成镂空层,采用斜杆受拉为主的横联,解决了铁路悬索桥钢梁的疲劳问题,同时具有较好的经济性。结合场地及运输条件,加劲梁分区段采用顶推、原位拼装、缆索吊结合的方案施工,解决了山区大跨度悬索桥的施工难题。

Design of Truss Stiffening Girder of a Long-Span Railway Suspension Bridge

A long-span railway bridge,located in the mountainous area with high seismicity,is designed as a deck-type steel truss girder suspension bridge with a main span of 1060 m.The truss stiffening girder consists of Warren trusses that measure 30 m wide and 12 m deep,and a truss panel is 10 m.To suit the mechanical properties of the railway suspension bridge in mountainous area with high seismicity,the towers and the stiffening girder are separated,and the towers and the piers are fixed,which forms a semi-floating system.The longitudinal dampers at the towers and the lower lateral bracings of the stiffening girder are installed in the same plan.At both the towers and abutments,the transverse bearings and dampers that can work collaboratively are installed,the back pressure structure that can regulate seismic forces is added,and local compression bearings are installed in the center of end floorbeams of abutments,to improve the intense seismic and heavy wind resistance of the bridge and address the issue of local track irregularity.The main components of the steel trusses are made of Q370qD steel,and components in local parts are made of Q500qD steel.The members of the main trusses and tie members are connected by M30 and M40 high strength bolts,respectively.The upper chords of the truss stiffening girder are formed of box cross-section members,with integral welding joints,while the lower chords are composed of H cross-section members,with detachable joints.In the upper level,the lateral bracings allow the box cross-section chords and the steel deck plates to form an integral cross section and share the acting loads.In the lower level,the H cross-section members and the lateral bracings form a transparent framed structure,with diagonal members in the transverse connection mainly in tension,which is beneficial to the fatigue resistance of the steel girder of railway suspension bridge and has better economic performance.Limited by the construction space and transportation access,the stiffening girder was divided into regions which could be constructed using tailored methods,including incremental launching,in-situ assembly and cableway crane construction.The proposed methods can facilitate the construction of long-span suspension bridge in mountainous area.