中山香山大桥主桥主梁结构设计

Design of Superstructure of Main Bridge of Xiangshan Bridge in Zhongshan

中山香山大桥主桥为双层钢桁梁公路斜拉桥,跨径布置为(136+312+880+312+136)m。桥塔采用人字形混凝土塔,下设整体式钻孔灌注桩;斜拉索采用∅7 mm高强度锌-铝合金镀层平行钢丝索;约束体系采用带纵向阻尼器的半飘浮体系。主梁采用2片N形主桁的钢桁梁结构,桁宽42.2 m,标准梁段桁高2.8 m。上、下弦杆和腹杆均采用带加劲肋的箱形截面,横梁均采用鱼腹式。边跨187.2 m范围内下层桥面采用混凝土桥面板起压重作用,其余上、下层桥面板均采用正交异性钢桥面板。下层纵向钢-混结合段位于辅助墩往跨中第4个节段,距辅助墩51.2 m,设置承压板、支撑加劲肋、预应力钢束、剪力钉和PBL板;横向钢-混结合段位于下层行车道两侧钢桥面板和混凝土桥面板之间(距下弦杆2.2 m处),设置剪力钉、PBL板和1.3 m宽UHPC后浇段。采用有限元软件进行全桥整体受力分析及桥面板局部分析,结果表明:结构满足规范要求。主梁采用大节段整体吊装施工,标准吊装节段长度为25.6 m,节段间除钢桥面板和弦杆顶板采用焊接外,其余均采用高强度螺栓连接。

The main bridge of Xiangshan Bridge in Zhongshan is a cable-stayed bridge with a main span of 880 m,two side spans of 312 m and two end spans of 136 m.Accommodating two levels of vehicle traffic,the superstructure consists of N-shaped steel trusses that measure 42.2 m wide and 2.8 m deep(typical truss segments),in which the upper and lower chords and web members are all of box cross-section with stiffeners,and the floorbeams are fish-belly shaped beams.A 187.2 m-long zone of each side span is placed with concrete deck panels which also serve as counterweight,the remaining zones are installed with orthotropic steel plates.The longitudinal steel-concrete joint section in the lower deck is located at the fourth segment counted from the auxiliary piers towards midspan,51.2 m to auxiliary piers),fitted with bearing plates,supporting stiffeners,prestressing tendons,shear studs and PBL connectors.The transverse steel-concrete joint section is located between the steel plates and concrete panels edging the traffic lanes on the lower deck(2.2 m to the lower chords),fitted with shear studs,PBL connectors and 1.3 m-wide cast-in-situ UHPC section.The pylons are concrete structure resembling the Chinese character"人",supported by bored piles.The stay cables are composed of high-strength Zn-Al alloy coated parallel steel wires of 7 mm diameter.Longitudinal dampers are installed between the pylon and the superstructure to form a semi-floating system.The load bearing behavior of the overall bridge and loading condition of local deck panels were numerically simulated.As per the analysis,the load bearing behavior of the structure meets the code requirements.The superstructure was divided into 25.6 m-long truss segments to facilitate hoisting.Apart from the upper flange of the chords and deck panels,the remaining components are all bolt-connected.