飞雁式异形钢箱拱制作线形控制关键技术研究

Analysis on Manufacturing Control of Flying Geese Shaped Steel Box Arch

钢结构桥梁采用大节段分段施工,工厂化预制,板块线形的精确放样是钢结构制作线形精准控制的关键因素。飞雁式异形钢结构拱肋曲线复杂,拱肋截面高度随拱轴线线性变化,给钢结构制作加工带来很大困难。桥梁拱肋设计成桥线形和预拱度线形的理论求解可为后续解决钢结构拱肋顶、底板加工制作,板块精确放样提供理论支持,为成桥后钢结构拱肋受力稳定提供保障。预制钢箱拱拱肋理论制作线形是确保偏态抛物线异形变截面钢箱拱桥顺利安装和桥梁服役阶段受力合理的重要技术指标。通过设计计算软件MIDAS建立桥梁理论计算模型,采用正装分析计算的方法计算出张拉预应力系杆、拆除拱肋安装支架、张拉吊杆、卸除主梁桥下支架、二次张拉吊杆等施工工序转换对拱肋成桥线形的影响,得到钢拱肋在施工、架设期间体系转换的理论预拱度值。再结合设计图纸给出的异形钢箱拱肋拱轴线计算方程式,通过坐标转换的方法,建立拱轴线上任一点O点的坐标系1和拱轴线上无限接近O点的相邻点B的坐标系2,以及全桥原始坐标系三者之间的联系。通过原始坐标系中O点位置坐标(x 1,z 1),B点位置坐标(x 2,z 2)以及O点处的截面高度H之间的关系,结合坐标系1和坐标系2确定出三者之间的三角形相似关联,从而求得成桥状态下异形钢箱拱肋制作的顶、底板,横隔板及吊杆与拱轴线计算方程式之间的几何关系,确定出钢箱拱拱肋顶、底板独立的成桥线形的计算方程式。运用此计算式求出的拱肋成桥曲线与设计院给出的设计线形吻合良好,当x 2-x 1=0.5 m时计算线形与成桥线形的最大偏差为2 mm,证明了此种方式的正确性。再通过成桥状态下的计算式,结合MIDAS模型计算出的拱肋曲线各点的预拱度值,求解出钢结构拱肋无应力状态下顶、底板,横隔板;吊杆的计算方程式。此计算方程式确定出的曲线状态就是钢拱肋无应力状态下线形,运用此计算结果求得的无应力状态曲线比成桥设计线形长出80 mm。此计算方法有效地解决了异形钢箱拱肋工厂预制过程中无应力状态板块线形精确放样的难题。

Steel structure bridges are constructed in large sections and are prefabricated in factories.The precise setting out of the line shape of the plates is the most important for the precise control of the line shape of the steel structure manufacturing.The flying geese shaped steel structure arch rib curve is complex,and the height of the arch rib section changes linearly with the arch axis,which brings great difficulties to the manufacture and processing of the steel structure.The theoretical solution of the design of the bridge arch ribs to the bridge line and the pre-curvature line can provide the theoretical support for the subsequent processing and manufacturing of the steel structure arch rib top and floor,and the precise layout of the plates,and provide the guarantee for the stability of the steel structure arch rib after the bridge completed.The theoretical manufacturing line shape of prefabricated steel box arch ribs is an important technical indicator to ensure the smooth installation of the parabolic parabolic deformed section steel box arch bridge and the reasonable stress on the bridge during the service period.Through the software MIDAS,the bridge theoretical calculation model was established,and the influence of construction process transformation on the arch rib bridge line shape,such as tensioning the prestressed tie bar,removing the arch rib mounting bracket,tensioning the suspender,removing the main beam under the bridge support,secondary tensioning suspender and so on,was analyzed.And the theoretical camber value of steel arch rib system transformation during construction and erection was obtained.Combined with the calculation equation of the arch axis of the special-shaped steel box arch rib given in the design drawings,the coordinate system of any point O point on the arch axis and the coordinate system B of the adjacent point B on the arch axis that was infinitely close to O point through the coordinate conversion method 2,and the original coordinate system of the whole bridge established the connection between the three.The triangle similarity relationship between the three was determined through the relationship between the position coordinate of point O in the original coordinate system,the position coordinate of point B,and the cross-sectional height H at point O in combination with coordinate system 1 and coordinate system 2.In order to obtain the geometric relationship between the top,bottom,diaphragm and hanger manufactured by the special-shaped steel box arch rib under the bridge state and the arch axis calculation equation,the independent bridge line shape of the steel box arch rib top and bottom plate determined the calculation equation.The curve of the arch rib formed by this calculation formula was in good agreement with the design line given by the design institute.When x 2-x 1=0.5 m,the maximum deviation is 2 mm,which proved the correctness of this method.Then,through the calculation equations under the bridge completion state,combined with the pre-camber value of each point of the arch rib curve calculated by the MIDAS model,the calculation equations of the roof,bottom plate,diaphragm,and hanger of the steel structure arch rib without stress were solved.The curve state determined by this calculation equation was the line shape of the rigid arch rib without stress.Using this calculation result,the curve of the unstressed state was 80 mm longer than the design line of the completed bridge.This calculation method effectively solved the problem of precise setting out in the unstressed linear manufacturing process of the prefabricated factory of special-shaped steel box arch ribs.