Verification of Tensile Force Estimation Method for Temporary Steel Rods of FCM Bridges Based on Area of Magnetic Hysteresis Curve Using Embedded Elasto-Magnetic Sensor.

Won-Kyu Kim,Jooyoung Park,Ju-Won Kim,Seunghee Park,Junkyeong Kim

doi:10.3390/s22031005

Abstract

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.

Highlights

IntroductionAs the construction industry develops, the importance of effective and efficient maintenance techniques for the structures is increasingly emphasized
Prestressed Concrete (PSC) has been used in numerous bridges since the late 1960s [3] when the post-tension method was first used in bridge construction
To apply the embedded EM sensors to the site, a tensile force monitoring experiment was conducted by measuring the magnetic hysteresis curve at the construction site of a PSC bridge where the free cantilever method (FCM) was applied

Summary

Introduction

As the construction industry develops, the importance of effective and efficient maintenance techniques for the structures is increasingly emphasized. In the case of bridges, the need for more advanced maintenance technology is gradually increasing as construction methods progress [1,2]. Prestressed Concrete (PSC) has been used in numerous bridges since the late 1960s [3] when the post-tension method was first used in bridge construction. PSC is characterized by a higher tensile strength than plain concrete because the initial 4.0/).

Methods

Results

Conclusion