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

摘要尽管斜拉桥越来越受欢迎，但没有准确或简单的方法可以直接测量斜拉索中的应力（力）。力的测量对于监测过大的风或交通载荷，测量地震事件后存在的再分配力以及通过截面损失检测腐蚀非常重要。计划开发一种远程（便携式）磁弹性传感器，用于直接测量钢索和肌腱中的应力。芝加哥伊利诺伊大学开发了一种基于圆柱形螺线线几何结构的磁弹性传感器，该传感器适用于施工时安装或在现有电缆的原位缠绕。该技术基于结构钢的磁性能与应力状态直接相关的依赖性。磁性能是通过将钢置于脉冲或周期性磁场中来测量的。通过钢周围或邻近电路的磁通变化可以测量磁性能。在-40 (F)至140(F)的温度范围内，对于弹性极限以下的不同尺寸的传感器，通常可以实现1%以内的精度（相对于称重传感器）。这些传感器已在几个项目的施工过程中接受了现场测试。该项目将研究将磁弹性测量原理扩展到新的传感电路的途径，该电路不需要将其缠绕在电缆上。它是便携式和可重复使用的。在屈服后使用这种线圈几何形状进行应力测量是非常理想的，用于评估由于意外载荷引起的电缆损伤。

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.