控制点晃动状态下斜拉桥索导管精密定位技术

平潭海峡公铁大桥元洪航道桥为(132+196+532+196+132)m公铁两用跨海斜拉桥,桥塔斜拉索锚固区底部3层为索导管结构,索导管采用无缝钢管制造。由于所处地理位置为台湾海峡风口处,常年大风,施工要求在8级风下能正常进行索导管定位测量,且受环境影响控制点只能布设在斜拉桥边墩墩顶及塔柱下横梁顶。在8级风下对控制点进行晃动测试分析,分析不同测回数取均值后的坐标偏差限值、内符合精度及外符合精度,得出20测回取均值可满足索导管安装精度5 mm的要求。索导管安装过程中,对其结构尺寸进行检查验收并制作定位板,采用塔柱施工面高程传递、距离投影改正等技术,确保了索导管锚固点三维坐标偏差在5 mm内,索导管锚固点与出塔点中心坐标的相对偏差在3 mm内,精度满足规范要求。

Precise Positioning Techniques for Cable Conduits of Cable-Stayed Bridge with Wobbling Control Points

The Yuanhong Navigational Channel Bridge of Pingtan Straits Rail-cum-Road Bridge is a sea-crossing rail-cum-road bridge with spans of 132,196,532,196 and 132 m.The three layers below the base of the pylon-cable anchor zone consist of conduits that are made from seamless steel tubes.Due to that the bridge is located at the wind mouth of Taiwan Straits where is frequently visited by heavy winds,the positioning measurement of the cable conduits should be normally conducted under the wind condition of Beaufort scale 8,and the control points must be placed on the tops of the side piers and the tops of the lower cross beams of the pylons of the cable-stayed bridge considering the environmental influence.Under the winds of Beaufort scale 8,the wobbling of control points were tested and analyzed,the mean values of the measured data were analyzed to obtain the limit values of coordinates differences as well as the internal and external accord precision.And the results show that the mean values of data measured by a number of 20 times can meet the installation precision of 5 mm for cable conduits.During the installation of the cable conduits,the dimension of the conduits were checked and accepted,and poisoning plates were prepared.By using a series of techniques,including the elevation transmission of the components under construction and distance projection,the error of 5 mm for the 3D coordinates of the anchor points of cable conduits was ensured.The relative error of the anchor points of the cable conduits and the openings on the pylon for threading cables out the conduits is within 3 mm,and the precision meets the code requirements.