空间扭曲结构钢桥的制造工艺

Research on Manufacturing Process of Space Twisting Structural Steel Bridge

随着人们生活水平的提高,以及公园城市概念的提出,对建筑景观的需求日益提升,越来越多的城市景观桥梁也随之出现,钢桥的空间造型呈现出复杂化的趋势,受其复杂的受力情况影响,往往伴随着特厚板(60 mm以上)压型等制造问题,故空间扭曲结构钢桥制作工艺值得深入探索。西一线跨绛溪河大桥位于成都绛溪河上,大桥采用三跨连续下承式梁拱组合体系钢桥,跨径为(55+175+55)m,宽51 m,平面位于半径R=400 m圆曲线上,边纵梁及拱肋呈空间扭曲形态,极不规则,空间构型完全由建筑景观决定,并不存在常规意义上的拱轴线,拱肋与边纵梁浑然一体,中心桩号处拱顶距桥面30 m,北侧拱肋内倾角度约47.69°,南侧拱肋内倾角度约24.85°,两拱于跨中交汇,结合段长度为14 m,拱间无其他横向联系。南、北拱肋采用单箱单室钢箱结构,以拱顶结合段为界,两拱小里程侧均为四边形断面,大里程侧均为五边形断面,拱肋空间形态十分复杂,除拱顶结合段壁板为单曲面,其余均为扭曲的双曲面板。在拱梁结合段造型最复杂区域,钢板最厚处达80 mm,两钢板夹角为22°,作为钢结构景观桥梁,本项目空间扭曲结构特征明显,钢板厚度大,故以此项目为依托进行研究具有借鉴意义。项目初期调研厚钢板主要压型方式为热压及冷压两种方式,因其制作模具成本太高以及加热对钢板性能的影响,最终项目采用趋势分析法+火矫的成型工艺以达到设计造型。具体工艺如下:首先采用三维软件分析压型钢板的曲率趋势划分压型分割区,再将压型分割区按照50~100 mm间距等分绘制压型控制线,并标记压型方向,用大吨位压力机压制压型线,伴随检验样板检查钢板曲率是否满足。合格后将钢板转至立式胎架火矫精调合格后转至组装区。组装前应根据钢桥线形制作胎架,胎架基础要有足够的承载力,防止在组装的过程中胎架发生沉降等现象,同时胎架要有足够的刚性以支撑钢桥。胎架支撑密度与隔板间距相同,胎架需要连续制作。因其为不规则形状,故壁板板肋要在壁板与隔板组装后再组装,同时钢梁需在胎架上焊接完成后,根据其环口匹配情况做适当修整以保证其造型的连续性。根据此工艺制造的西一线跨绛溪河大桥避免了模具制作,压型工序可以形成系统化流水施工,大大节省了模具制作费用,节省了施工周期,且成桥后线形美观,可为类似钢结构工程施工提供一定的借鉴。

With the improvement of people′s living standards,and the concept of park city,the demand for architectural landscape is increasing,more and more urban landscape bridges are also appearing,the spatial shape of steel bridges presents a trend of complexity,affected by its complex force situation,often accompanied by manufacturing problems such as ultra-thick plate(more than 60 mm thickness)pressing,and the production process of steel bridges with solid space distortion structure is worth exploring in depth.The west line span Jiangxi River Bridge is located on the Jiangxi River in Chengdu,the bridge adopts a three-span continuous downward bearing beam and arch combination system steel bridge,the span diameter is(55+175+55)m,the width is 51 m,the plane is located in the radius R=400 m circular curve,the side longitudinal beam and arch rib are in a spatial distortion form,extremely irregular,the spatial configuration is completely determined by the architectural landscape,and there is no arch axis in the conventional sense,the arch rib and the side longitudinal beam are seamlessly integrated.The vault at the center pile is 30 m from the bridge deck,and the inverted angle of the north side arch rib is about 47.69°.The angle of inversion of the rib on the south side is about 24.85°,and the two arches meet in the middle of the span,the length of the joint section is 14 m,and there is no other transverse connection between the arches.The south and north arch ribs adopt a single-box single-chamber steel box structure,bounded by the vault joint section,the two arches are quadrangular sections on the small mileage side,and the large mileage side is a pentagonal section,and the space shape of the arch ribs is very complex.Except for the wall plate of the vault joint section,the rest are twisted hyperboloid versions.In the most complex area of the arch beam joint section,the thickest part of the steel plate is 80 mm,and the angle between the two steel plates is 22°,as a steel structure landscape bridge,the spatial distortion structure of this project has obvious characteristics,the thickness of the steel plate is large,and it is of reference significance to study based on this project.At the beginning of the project,the main pressing methods of thick steel plate are hot pressing and cold pressing.Because the cost of making molds is too high and the impact of heating on the performance of steel plates,finally the project adopts the trend analysis method+fire correction molding process to achieve the design modeling.The specific process is as follows:firstly,the threedimensional software is used to analyze the curvature trend of the profiled steel plate and divide the profiled segmentation area,and then the profiled segmentation area is divided into equal parts according to the 50~100 mm spacing to draw the profiled control line,and mark the profiled direction,press the profiled line with a large-tonnage press,and check whether the curvature of the steel plate is satisfied with the inspection sample.After qualifying,the steel plate will be transferred to the vertical tire frame,and after the fire adjustment is fine-tuned,it will be transferred to the assembly area.Before assembly,the tire frame should be made according to the linear shape of the steel bridge,and the tire frame foundation should have enough bearing capacity to prevent the tire frame from settling in the process of assembly,and the tire frame should have enough rigidity to support the steel bridge.The support density of the tire frame is the same as the spacing of the partition,and the tire frame needs to be made continuously.Because it is an irregular shape,the wall plate rib should be assembled after the wall plate and the partition plate are assembled.At the same time,steel beam needs to be welded on the tire frame after the completion of the appropriate trimming according to its ring mouth matching situation to ensure the continuity of its modeling.According to this process,the west line across the Jiangxi River bridge manufactured avoids the mold making,and the pressing process can form a systematic flow construction,which greatly saves the mold production cost and construction period.The linear shape is beautiful after the bridge is completed,and can be used as a certain reference for the construction of similar steel structure engineering.