Development of a Remote Coil Magnetoelastic Stress Sensor for Monitoring Steel Cables and Tendons

用于钢索和斜拉索监测的远程线圈磁弹性应力传感器的研制尽管斜拉桥日益普及，但还没有准确或简单的方法来直接测量斜拉索中的应力(力)。力的测量对于监测过量的风或交通荷载、测量地震后存在的重分布力以及通过横截面的损失来检测腐蚀是重要的。伊利诺伊大学芝加哥分校开发了一种用于直接测量钢索和钢索应力的远程(便携式)磁弹性传感器，该传感器基于圆柱螺线管几何结构，适用于现有电缆的施工或现场缠绕时安装。该技术是基于结构钢的磁性与应力状态直接相关的依赖性。通过将钢置于脉冲或周期磁化磁场中来测量磁性能。通过钢材周围或邻近电路的磁通变化，可以测量磁特性。在-40(F)至140(F)的温度范围内，不同尺寸的传感器在弹性极限以下通常可获得1%(相对于称重传感器)的精度。在几个项目的建设过程中，这些传感器已被接受进行现场测试。该项目将探索将磁弹性测量原理扩展到一种新的传感电路的方法，该电路不需要将其缠绕在电缆上。它是可移植和可重复使用的。非常需要在屈服后区域使用这种线圈几何形状进行应力测量，以评估由于意外载荷造成的电缆损坏。

Development of a Remote Coil Magnetoelastic Stress Sensor for Monitoring Steel Cables and TendonsABSTRACTDespite the increasing popularity of cable-stayed bridges, no accurate or simple method is available for directly measuring the stresses (forces) in the cable stays. The measurement of the forces is important for monitoring excessive wind or traffic loadings, to gage the redistribution forces present after seismic events, and for detecting corrosion via loss of the cross section. It is planned to develop a remote (portable) magnetoelastic sensor for the direct measurement of stress in steel cables and tendons.A magnetoelastic sensor based on a cylindrical solenoidal geometry, which is suitable for installation at the time of construction or winding in-situ for existing cables has been developed at the University of Illinois at Chicago. The technique is based upon the dependence of the magnetic properties of structural steels directly related to the state of stress. The magnetic properties are measured by subjecting the steel to a pulse or periodic magnetising field. Changes in flux through circuits surrounding or adjacent to the steel allow the magnetic properties to be measured. Accuracy within 1% (against a load cell) in the temperature range of -40 (F) to 140(F) are routinely achieved with different sizes of sensor below the elastic limit. These sensors have been accepted for field testing during the construction of several projects. This project will investigate avenues to extend the magnetoelastic measurement principles to a new sensing circuit which does not require winding it around the cable. It is portable and reusable. It is highly desirable to perform the stress measurement using this coil geometry in the post-yield regime for damage assessment of cables due to unanticipated loadings.