平潭海峡公铁两用大桥主桥整节段全焊钢桁梁设计

Design of Full Block and All-Welded Steel Truss Girder of Main Bridge of Pingtan Straits Rail-cum-Road Bridge

平潭海峡公铁两用大桥元洪航道主桥采用(132+196+532+196+132)m钢桁梁斜拉桥。斜拉桥主梁为带副桁的板桁结合钢桁梁结构,双层桥面布置,上层为6车道高速公路,下层为双线铁路。3号桥塔与主梁间设纵向固定支座,4号桥塔与主梁间设纵向阻尼器。主桁采用N形桁式,桁高13.5m,桁宽15m,标准节间长度14m;副桁架上弦杆顶板中心线间距35.7m。有索区公路桥面及铁路桥面采用密横梁支撑正交异性整体钢桥面结构;无索区公路桥面采用密横梁支撑混凝土桥面结构。在铁路桥面系压重区设封闭钢箱,箱内采用素混凝土集中压重。桥墩处主桁架的竖杆上设置板式桥门架。梁端锚固采用锚拉板结构。该桥采用两节间大节段全焊制造及吊装,最大吊重1 250t,双悬臂架设。

The Yuanhong Ship Channel Main Bridge of Pingtan Straits Rail-cure-Road Bridge is a steel truss girder cable-stayed bridge with span arrangement （132 ＋ 196 ＋ 532 ＋ 196 ＋132） m. The main girder of the cable-stayed bridge is the plate and truss composite steel truss girder struc- ture provided with a secondary truss and is arranged into double decks. The upper deck of the bridge carries 6-lane expressway while the lower deck carries 2-track railway. In between the pylon No. 3 and main girder, the longitudinal fixed bearings are arranged and in between the pylon No. 4 and main girder, the longitudinal dampers are arranged. The main truss of the bridge is the N- shape truss that is 13.5 m high, 15 m wide and the typical panel length of the truss is 14 m. The center-to-center line distance of the upper chord top plates of the secondary truss is 35.7 m. In the areas of the highway and railway floor systems with stay cables, the integral orthotropic steel deck structures that are supported by the densely arranged cross beams are applied. In the area of the highway floor system without stay cables, the concrete deck structure that is supported by the densely arranged cross beams is applied and in the counterweight areas of the railway floor system, the closed steel box girders are arranged, in which the plain concrete is placed to serve as the con- centrated counterweight. On the vertical members of the main truss at the piers, the plate type portal frames are arranged and the anchorage at the girder ends are the anchor tensile plate struc- tures. The steel truss girder of the bridge is manufactured by all-welding and is lifted in large blocks in each two panels, the maximum lifting weight of the panels is 1 250 t and the panels are eretted by the two-side cantilever method.