牛田洋大桥主桥钢桁梁设计

Design of Steel Truss Girder of Main Bridge of Niutianyang Bridge

汕头市牛田洋大桥主桥为(77.5+166.1+468+166.1+77.5)m公轨两用钢桁梁斜拉桥。主桥采用双层桥面布置,上层为双向8车道一级公路兼城市快速路,下层为双线跨座式轨道交通。该桥采用半飘浮体系,纵、横向正交分离的减隔震约束体系。主梁采用带副桁的板桁结合钢桁梁结构,主桁采用三角桁,桁高11 m,2片主桁中心间距16 m;副桁上弦杆采用平行四边形箱形截面,弦杆顶板中心线间距37.2 m。主梁共63个节间,标准节间长15.1 m,主跨及次边跨公路桥面系采用纵横梁体系正交异性整体钢桥面板,边跨公路桥面系采用纵、横梁支撑的混凝土桥面板;下层轨道交通无桥面板,设置下平纵联。索梁锚固采用锚拉板式钢锚箱。主梁标准节段采用两节间大节段全焊制造。边跨、次边跨钢桁梁采用顶推法施工,主跨钢桁梁采用悬臂吊装法施工。

The main bridge of Niutianyang Bridge in Shantou is a steel truss girder cable-stayed bridge with a main span of 468 m,two side spans of 166.1 m and two end spans of 77.5 m.The bridge is a double-decker,with the upper deck accommodating 8 lanes of Grade A highway/urban fast track and the lower deck carrying double straddle-type light rails.The cable-stayed structure is a semi-floating system,fitted with a seismic isolation system that orthogonally separates the force transmission in the longitudinal and transverse directions.The superstructure consists of steel trusses which act compositely with the orthotropic steel deck plates equipped with secondary trusses.The two lateral trusses of 11 m deep are spaced center-to-center at 16 m,and a standard truss panel is 15.1 m long,and a total of 63 panels are used.The upper chords of secondary trusses are of parallelogram cross-section,the transverse distance of two lateral upper chords is 37.2 m(between the center lines of the two top plates).The roadway deck in the main span and two end spans is formed of orthotropic steel plates supported on stringers and floor beams,while the roadway deck in the side spans is composed of concrete slabs supported on stringers and floor beams.The lower deck carrying the light rails consists of bottom lateral bracings.The stay cables are linked to the main girder via steel anchor boxes of tensile plate type.Each and every two truss panels were fully welded together to form a large segment.The steel trusses in the side and end spans were incrementally launched into position,while the steel trusses in the main span were erected by cantilever assembly method.