宁波三官堂大桥施工控制关键技术

Key Construction Control Techniques for Sanguantang Bridge in Ningbo

宁波三官堂大桥主桥为(160+465+160)m连续钢桁架桥,主梁采用2片主桁,变高、N形桁式,全焊结构,一跨过江。该桥主梁采用悬臂拼装,江中不设临时墩。采用MIDAS Civil软件建立主桥空间模型,模拟桥梁施工过程,结合有限元计算进行该桥施工控制。施工中,通过设置制造预拱度、凌晨安装、采用角度法控制安装坐标、控制焊缝变形等进行预拱度控制;合龙后通过边墩顶升0.8m的方式调整主梁受力;通过在边墩设置高强拉杆及张拉进行抗倾覆控制;采用温度配切法进行合龙控制。通过以上施工控制关键技术,合龙前两岸弦杆相对高差为7mm;桥梁抗倾覆系数不小于1.3;上弦实测最大拉应力由266 MPa降到142 MPa;合龙后合龙口实测误差10mm,满足要求。

The main bridge of Sanguantang Bridge in Ningbo,a continuous steel truss bridge,has a main span of 456 m and two side spans of 160 m,which crosses the river with no piers in water.The superstructure consists of two fully-welded N-shaped trusses that are variable in depth and erected by cantilever assembly method without the assistance of temporary piers.The main bridge spatial model was built up by MIDAS Civil to simulate the construction process of the bridge,and based on which the construction control was conducted.The pre-camber of the trusses were kept under control by taking multiple measures,such as reserving pre-camber in the manufacturing process,installing the trusses in the early morning,and utilizing the angle method to control the coordinates and weld deformation.After closure,the side piers were jacked up by 0.8 m to adjust the load bearing condition of the main girder.High-strength tension bars were added in the side piers and tensioned to improve the overturning capacity of the main girder.The closure of the main girder was realized by cutting and pushing.By implementing all these techniques,before closure,the relative height difference between the chords on the two banks was 7 mm,the overturning coefficient of the bridge was no less than 1.3,and the measured maximum tensile stress in the upper chord decreased from 266 MPa to 142 MPa.After closure,the measured elevation error at the closure gap was 10 mm,meeting the code requirements.