Equipment Group, Industrial Materials Team 2, Materials Division, Samsung C&T Corporation, Seoul 05510, Korea.
Department of Convergence Engineering for Future City, Sungkyunkwan University, Suwon 16419, Korea.
Sensors (Basel). 2022 Jan 27;22(3):1005. doi: 10.3390/s22031005.
The free cantilever method (FCM) is a bridge construction method in which the left and right segments are joined in sequence from a pier without using a bottom strut. To support the imbalance of the left and right moments during construction, temporary steel rods, upon which tensile force is applied that cannot be managed after construction, are embedded in the pier. If there is an excessive loss of tensile force applied to the steel rods, the segments can collapse owing to the unbalanced moment, which may cause personal and property damage. Therefore, it is essential to monitor the tensile force in the temporary steel rods to prevent such accidents. In this study, a tensile force estimation method for the temporary steel rods of an FCM bridge using embedded Elasto-Magnetic (EM) sensors was proposed. After the tensile force was applied to the steel rods, the change in tensile force was monitored according to the changing area of a magnetic hysteresis curve, as measured by the embedded EM sensors. To verify the field applicability of the proposed method, the EM sensors were installed in an FCM bridge pier under construction. The three sensors were installed in conjunction with a sheath tube, and the magnetic hysteresis curve was measured over nine months. Temperature data from the measurement period were used to compensate for the error due to daily temperature fluctuations. The estimated tensile force was consistent with an error range of ±4% when compared with the reference value measured by the load cell. Based on the results of this experiment, the applicability of the proposed method was demonstrated.
自由悬臂法（FCM）是一种桥梁施工方法，在该方法中，左右节段从桥墩处依次连接，无需使用底撑。为了支撑施工过程中左右弯矩的不平衡，在桥墩中嵌入了临时钢棒，这些钢棒承受着无法在施工后管理的拉力。如果施加到钢棒上的拉力过大，由于不平衡的弯矩，节段可能会倒塌，从而可能导致人员伤亡和财产损失。因此，必须监测临时钢棒的拉力，以防止此类事故发生。在本研究中，提出了一种使用嵌入式弹性磁（EM）传感器估算 FCM 桥梁临时钢棒拉力的方法。在对钢棒施加拉力后，通过嵌入式 EM 传感器测量的磁滞回线变化面积来监测拉力的变化。为了验证所提出方法的现场适用性，在在建的 FCM 桥墩中安装了 EM 传感器。三个传感器与护套管一起安装，并在九个月内测量了磁滞回线。测量期间的温度数据用于补偿由于日常温度波动而导致的误差。与通过称重传感器测量的参考值相比，估算的拉力与误差范围在±4%以内。基于该实验结果，证明了所提出方法的适用性。
