金阳河特大桥超高桥墩设计关键技术

Key Design Techniques of High-Rise Piers of Jinyanghe River Bridge

金阳河特大桥主桥为(106+2×200+115+40)m连续刚构桥,位于高山峡谷地带,桥址处50年超越概率10%地震烈度7.7度,5~7号主墩分别高113、196、182 m。针对横桥向抗震响应突出且墩高差异大的特点,主墩采用钢管混凝土组合墩,对墩高较大的6号、7号主墩横桥向双侧放坡,各主墩顺桥向尺寸保持恒定以方便施工,梁端设置粘滞阻尼器以实现顺桥向耗能减震;各主墩刚度经匹配设计,控制截面的地震响应达到合理比例。主墩为外包混凝土的四肢钢管混凝土柱及柱间腹板形成的箱形构造,竖向每间隔12 m设置1道钢筋混凝土横隔板;墩梁固结采用钢管混凝土柱置于主梁0号块腹板外侧的连接构造,钢管混凝土柱与承台连接采用承压板+PBL剪力键的构造。大桥整体结构计算结果表明:持久状况和E2地震作用下,钢管混凝土组合墩满足承载能力极限状态要求,主墩墩顶水平位移小于规范规定的变形容许值。主墩施工先安装钢管骨架,再采用液压爬模工艺施工钢管外包层和柱间腹板,研发了多点同步重型提升系统代替大型塔吊,以降低高空作业安全风险,节省施工费用。

Located in a valley of a high mountain area,the main bridge of Jinyanghe River Bridge is a continuous rigid-frame bridge with two main spans of 200 m,and three side spans of 106,115 and 40 m,capable of withstanding 7.7 magnitude earthquakes,with 10%probability of exceedance in 50 years.The main piers No.5-No.7 measure 113,196 and 182 m high,respectively,and the three piers exhibit significant transverse seismic responses.The higher piers No.6 and No.7 are sloped on two sides along the bridge width,and all the three piers keep constant dimension along the bridge length to facilitate construction.Dampers are installed in the superstructure to achieve seismic energy dissipation along bridge length.All the main piers are endowed with matched stiffness to allow the cross-sectional seismic responses to be with a rational proportion.All the main piers are rectangular composite piers,each consisting of four concrete-filled steel tubes,reinforced concrete webs,and reinforced concrete diaphragms installed every 12 m along the heights of the piers.The piers are consolidated with the pier-top girder segments,with dapped ends,while connected with the pile caps via bearing plates and PBL connectors.The calculations of the entire bridge structure indicate that the piers meet the load bearing demands at the serviceability limit state and the ultimate limit state as well as under the action of E2 earthquakes,and the pier-top horizontal displacements are smaller than the deformation allowances given in the codes.During the construction of the piers,the steel tubular skeletons were sequentially installed,encased with concrete using hydraulic climbing formwork,and connected by webs.A multi-point synchronous heavy lifting system was applied,instead of the large-scale tower cranes,to reduce the safety risk of mid-air work and cut down construction costs.