青山长江公路大桥无下横梁桥塔设计关键技术

Key Design Techniques for Pylon without Lower Cross Beam for Qingshan Changjiang River Highway Bridge

青山长江公路大桥主桥为主跨938m的双塔双索面混合梁斜拉桥,采用七跨连续全飘浮体系。结合主桥大跨、超宽、重载以及下塔柱短的技术特点,主桥桥塔采用无下横梁的A形桥塔,通过设置于桥塔中心处的0号斜拉索为主梁提供桥塔处竖向支撑。根据桥塔的结构形式及受力特点,将桥塔上横梁设置于桥面以上塔柱中点位置处,塔顶结合段总高设置为20m。根据主桥斜拉索索力及角度变化范围大等特点,设置3种不同的斜拉索锚固方式,采用变高的钢锚梁设计(取消了滑动侧四氟滑板的设置)。为精确分析桥塔受力特点,建立全桥三维模型,对桥塔施工及运营阶段进行有限元分析,并对塔顶结合段、斜拉索锚固区及钢锚梁进行实体有限元局部分析,结果表明桥塔的强度及刚度均满足规范要求。

The main bridge of Qingshan Changjiang River Highway Bridge is a hybrid girder cable-stayed bridge of a seven-span continuous full-floating system.The bridge has two pylons,creating a main span of 938 m,and the stay cables are fanned out in double cable planes.To accommodate the technical features of the main bridge,such as long span length,very wide deck width,heavy load bearing capacity and short lower pylon columns,the pylon is designed as the A-shaped pylon without lower cross beam,which can provide vertical support at the pylon to the main girder via the No.0 stay cable located at the center of the pylon.Based on the structural form and load bearing behavior of the pylon,the upper pylon cross beam is located at the central points of the upper pylon columns and the full height of the pylon-top joint section is 20 m.Due to that the variation of cable forces and angles of the stay cables of main bridge is great,three different cable anchoring ways are used and the variable-height steel anchor beams are designed(the teflon sliding plate at the sliding side is removed.).To accurately analyze the load bearing characteristics of the pylon,the three-dimensional model of the overall bridge was established,to carry out finite element analysis of the pylon at both the construction and operation stages.And to the pylon-top joint section,cable anchorage zone and steel anchor beam,local solid finite element analysis was conducted.The results of analysis demonstrate that the strength and stiffness of the pylon can meet the code requirements.