悬索桥索夹螺杆轴力超声识别的影响因素分析及应用

Influence Factor Analysis and Application of Ultrasonic Method for Identifying Cable Clamp Blot Axial Force in Suspension Bridge

为有效评估悬索桥索夹螺杆轴力的损失程度,对悬索桥索夹螺杆轴力超声识别方法进行了影响因素分析及实桥应用。首先,基于声弹性效应建立螺杆轴力计算公式,并用于螺杆轴力识别;然后,分析无应力声时差异和应力系数差异对识别精度的影响;最后,将该方法用于识别螺杆张拉效率和梁段吊装过程中的螺杆轴力损失。结果表明:1)悬索桥索夹螺杆声弹性效应明显,螺杆轴力识别误差均在1.1%以内。2)传感器耦合状态和螺杆几何、材料参数差异均会影响螺杆无应力声时,从而影响螺杆轴力识别精度,二者引起的轴力识别偏差分别为47.7和43.7 kN。3)不同螺杆应力系数存在差异,标定螺杆与待测螺杆应力系数差异引起的轴力识别偏差为4.75%。4)通过实测声时计算螺杆张拉效率来控制螺母拧紧程度,螺杆张拉效率达到94%以上,较未控制螺母拧紧程度前最大增加了95.93%;索夹螺杆轴力随梁段重量的增加损失严重,实测索夹平均轴力最低为424.32 kN,仅达到设计轴力的56.58%,在梁段吊装过程中应及时对索夹螺杆进行补张拉,确保施工安全。

To effectively evaluate the loss of axial force for the bolts in cable clamp of suspension bridge,the influence factors analyses and application of ultrasonic identification method for cable clamp blot axial force in suspension bridge were carried out.Firstly,the axial force calculation formula was established based on the acoustic elastic effect,and the accuracy of this formula was verified by experiments.Then,effects of the non-stress acoustic time difference and stress coefficient difference on the recognition accuracy was analyzed.Finally,this method was utilized to identify the tension efficiency and the axial force loss during the lifting process.The results show that:1)The acoustoelastic effect of bolts is obvious and the recognition error of screw axial force is less than 1.1%.2)Identification errors caused by the coupling state of sensors and the blot geometry and material parameters are 47.7 kN and 43.1 kN,respectively.3)The stress coefficients of different bolts are different.Identification deviation caused by the difference of stress coefficients between calibrated bolts and tested bolts is 4.75%.4)With the increase of screw nut tightening degree,the tension efficiency can reach more than 94%,which is 95.93%higher than that before the tightening degree of nut is not controlled.The bolt axial force is seriously lost with the increase of beam weight.The measured minimum average axial force of cable clamps is 424.32 kN,which is only 56.58%of the designed axial force.In the process of beam section hoisting,the cable clamp bolts should be tensioned in time to ensure construction safety.