烂泥湖高架桥水中门式墩长悬臂盖梁施工技术

Construction Techniques for Long Cantilever Capping Beam of In-Water Portal Pier of Lanni Lake Viaduct

烂泥湖高架桥水中门式墩预应力盖梁悬臂长5.975m,为确保盖梁施工顺利进行,在分析抱箍法(钢梢棒法)和钢管桩支架法的支架受力、悬臂端挠度后,确定采用钢管桩支架法施工盖梁。支架下部采用630mm钢管桩,在钢管桩上搭设双排I45a工字钢作为分配梁,分配梁横桥向上铺设2组贝雷梁,贝雷梁顺桥向上铺设I20a工字钢,在盖梁翼缘及中部拱形横梁下方搭设碗扣式脚手架并设置剪刀撑及扫地杆,脚手架顺桥向顶撑上铺设10cm×15cm方木,以支承盖梁模板;支架搭设完后安装盖梁模板,加工钢筋,浇筑盖梁混凝土。分析表明,钢管桩支架法能保证长悬臂盖梁端部挠度变形不影响盖梁线形及断面尺寸,确保长悬臂盖梁施工质量及安全。

The cantilever length of a prestressed concrete capping beam of the in-water portal pier of Lanni Lake Viaduct is 5.975 m.To ensure the smooth construction of the capping beam and after analysis of the force conditions and cantilever end deflection of the girdling method（steel tip staff method） and the steel pipe pile scaffolding method,it was determined that the steel pipe pile scaffolding method should be used for construction of the capping beam.For the lower part of the steel pipe pile scaffolding,the 630 mm steel pipe piles were used.On the pipes,the double-row I45a I-steels were laid to serve as the distribution beam.On the distribution beam in the transverse direction of the bridge,2 groups of the bailey trusses were laid and on the bailey trusses in the longitudinal direction of the bridge,the I20a I-steels were laid.On the flanges of the capping beam and under the middle arch crossing beam,the bowl-coupler scaffolding was set up,on which the cross struts and floor horizontal members were installed.On the top supports of the scaffolding in the longitudinal direction of the bridge,the square timbers of 10 cm×15 cm were laid to support the formwork of the capping beam.After the scaffolding was set up,the formwork was installed,the reinforcement was arranged and the concrete for the capping beam was cast.The results of the analysis show that the steel pipe pile scaffolding method can ensure that in the construction of the long cantilever capping beam,the deflection and deformation of the capping beam ends will not affect the geometric shape and sectional dimensions of the beams and can ensure the construction quality and safety of the beam.