斜拉索相对拔出量控制二张索力技术研究

Study of Technique of Using Relative Pull-Out Length to Control Force of Second Cable Tensioning for Cable-Stayed Bridge

为能及时张拉且准确控制斜拉桥主梁悬臂拼装过程中斜拉索的二张索力,以某混合式结合梁斜拉桥为背景,推导斜拉索相对拔出量与对应索力增量的计算公式,采用有限元法分析了主梁悬臂拼装阶段桥塔偏位、主梁悬臂端位移以及对应索力三者之间的关系,并根据桥塔偏位、主梁悬臂端位移具有相对独立性的关系对相对拔出量公式进行了简化。实践表明,采用相对拔出量简化公式控制斜拉索的二张索力,有效地克服了温度对斜拉索二张索力的影响,实测值与理论值较吻合;张拉时间不受限制,节省了工期。

In order to ensure the timely tensioning of the stay cables for the second time as well as the accurate control of the tensioning forces during the process of the cantilever assembly of the main girder of cable-stayed bridge, a hybrid type cable-stayed bridge with composite girder was cited as an example. The computing formula of the relative pull-out length of stay cables and the corresponding cable force increment was derived. The finite element method was adopted to analyze the relations among the pylon offsetting, the displacement at the ends of the main girder cantilevers and the corresponding cable forces in the cantilever assembling stage of the main girder. Considering that the pylon offsetting and displacement at the ends of the main girder cantilevers are relatively independent, the formula of the relative pull-out length was simplified. It is proved that the application of the simplified formula of relative pull-out length to control the second tensioning forces of the stay cables effectively overcomes the impact of temperature on the force of the second tensioning of stay cables, the calculated values and the measured data are basically agreed, the time of the stay cable tensioning is not restricted by other construction procedures, thereby, the construction time is saved.