瓯江北口大桥中塔设计及索鞍施工预偏量影响研究

Design and Research on Intermediate Tower & Pre-Deflection of Saddles in the Construction of Oujiang River North Estuary Bridge

温州瓯江北口大桥主桥为缆跨布置(230+800+800+348)m的三塔四跨连续弹性支承体系悬索桥。该桥中塔采用四柱式钢筋混凝土A形刚性塔,总高142m,纵向为A形,横向为门形。由于刚性中塔的采用,在提高中塔自身抗推刚度的同时,提高了结构的整体刚度,活载作用下加劲梁挠跨比1/588,中塔单根主缆的最大不平衡力达到35 003kN;与此同时,结构扭转基频提高到0.486Hz,颤振临界风速达到113.9m/s,抗风性能得到很大改善。采用BNLAS软件对中塔索鞍预偏与否进行分析,结果表明:中塔顶主鞍座的理论预偏量为0.239m,预偏与否对中塔受力影响很有限、对边塔受力基本无影响,因此设计建议取消中塔索鞍预偏及顶推。

The main bridge of the Oujiang River North Estuary Bridge in Wenzhou is a suspension bridge with the three-tower four-span system of continuous elastic support,and cable span arrangement of(230+800+800+348)m.A-shaped rigid RC tower with four columns is adopted for the intermediate tower.The height of the tower is 142 m,and the longitudinal and transverse shapes of the tower are A-shape and door shape,respectively.Because of the adoption of rigid middle tower,the integral stiffness of the structure is improved while the thrust stiffness of the tower itself is increased.The ratio of deflection to span is only 1/588 while the maximum unbalanced force of the single main cable of the middle tower reaches 35 003 kN under the action of live load.At the same time,the torsional fundamental frequency of the structure increases to 0.486 Hz,and the critical flutter wind speed is 113.9 m/s.The performance of resisting wind has been greatly improved.The software BNLAS was used to analyze the pre-deflection of the saddle of the middle tower.The results show that the theoretical pre-deflection of the main saddle of the top of the middle tower is 0.239 m.The pre-deflection has a limited influence on the force of the middle tower and has a negligible effect on the force of the side tower.Therefore,the pre-deflection and incremental launching of intermediate-tower-saddle are suggested to be canceled in the design.