宁波鄞县大道跨线桥主桥横向平移及竖向顶升关键技术

Key Horizontal Translation and Vertical Jacking Techniques for Main Bridge of a Flyover Bridge of Yinxian Avenue in Ningbo

宁波市鄞县大道原跨线桥主桥为(45+70+45)m预应力混凝土变截面连续梁桥,采用左、右幅相互独立的直腹板单箱单室箱梁,幅宽13.25 m,间隔4 m。由于鄞州大道快速路改造,桥面标高、分幅形式均不满足相应要求,为了降低对鄞县大道交通的影响,主桥采取横向平移+竖向顶升相结合的改造方式代替拆除新建,即左、右幅桥各相向平移2 m并为一幅,平移后竖向顶升7.8 m。改造施工中,采用由混凝土框架梁柱结构、液压千斤顶、钢分配梁组成的平移及顶升受力托换结构体系;应用主动施力静压支撑的机械跟随千斤顶保护技术,避免交替承力时梁体出现受力不均;利用聚四氟乙烯板与镜面钢板组成的滑移面,有效地减少了顶推力;设置平移及顶升限位措施、钢支撑钢框架稳定措施。主桥平移后横向水平误差仅为3 mm,顶升后标高误差为2 mm,结构未发生二次损伤,满足改造要求。

The main bridge of the original flyover bridge of Yinxian Avenue in Ningbo was a prestressed concrete continuous girder bridge with three spans of 45,70 and 45 m.The bridge had two identical decks that consist of variable-depth single-cell box girders with vertical webs,each deck measures 13.25 m wide and the two decks are spaced 4 m.When the Yinzhou Avenue was revamped,the deck elevation and structural configuration of the bridge could not meet the requirements.To limit traffic disruption,the selected solution was to horizontally translate the left and right decks towards each other for 2 m to merge to be an integrated deck,and then,vertically jacked up 7.8 m.During the revamp,a system composed of concrete frames,hydraulic jacks,steel distribution beams was employed for the horizontal translation and jack-up of the decks.To avoid uneven forces on the superstructure due to the alternated loading of the two decks,Teflon plates and mirror-face steel plates were placed to create a sliding surface,to effectively reduce the jacking force needed.In addition,stoppers and steel supporting frames were utilized to ensure the safety of the horizontal translation and jacking.After completion,the errors of horizontal locations and final deck elevation were 3 mm and 2 mm,respectively,and no secondary damages were observed on the bridge,meeting the revamp requirements.