温州瓯江北口大桥中塔结构形式比选

Comparison and Selection of Structural Type for Middle Tower of Oujiang River North Estuary Bridge in Wenzhou

温州瓯江北口大桥主桥为主跨2×800m的三塔双层桥面钢桁梁悬索桥,为选择该桥合理的中塔结构形式,从结构受力、经济性、施工便捷性等方面对纵向A形混凝土中塔、纵向人字形钢中塔和纵向I形钢-混凝土混合中塔3种中塔方案进行综合比选。结果表明:若采用纵向A形混凝土中塔方案,结构整体刚度较大,但需保证名义摩擦系数≥0.3以满足主缆抗滑的要求,若采用其他2种中塔方案,名义摩擦系数取0.2即可;3种中塔方案均可通过调整相关结构尺寸满足自身的受力要求;结合中塔沉井基础,纵向A形混凝土中塔方案经济性最优,且桥梁施工过程中可保证施工塔吊不超高。经综合比选,该桥中塔最终采用纵向A形混凝土塔,通过在中塔鞍座中增加竖向摩擦板的方法保证主缆的抗滑安全。

The main bridge of the Oujiang River North Estuary Bridge in Wenzhou is a three- tower and double-deck steel truss girder suspension bridge with the main spans of 2X800 m. To select the reasonable structural type for the middle tower of the bridge, 3 schemes of the longitudi-nal A-shape concrete tower, longitudinal inverted Y-shape steel tower and longitudinal I-shape steel and concrete hybrid tower are comprehensively compared in aspects of the structural force conditions, cost effectiveness and construction convenience. The results of the comparison yield that if the scheme of the A-shape concrete tower is selected, the global stiffness of the structure will be great, but the nominal friction coefficient ^0. 3 should be guaranteed so that the anti-slip requirement of the main cables on the tower can be met. If the schemes of the other 2 towers are selected, the nominal friction coefficient of 0. 2 will be okey. For the 3 schemes, the relevant structural dimensions of the towers can be adjusted so as to meet the structural force condition re-quirements of the tower of each scheme. With regard to the open caisson foundation designed for the middle tower, the scheme of the A-shape concrete tower is deemed to be most cost-effective and in the construction, the tower crane for the construction will not be arranged higher than the tower of the bridge. According to the comparison, the A-shape concrete tower is finally selected and the anti-slip safety of the main cables will be guaranteed by adding the vertical friction plates in the middle tower saddle.