Investigation of resonance-enhanced magnetoelastic method in the prestress monitoring of PC structures

Abstract

Prestress provided by prestressed tendons is a critical indicator for evaluating the strength and durability of prestressed concrete (PC) structures. Most PC structures are constructed using post-tensioning techniques. Prestressed tendons, which are encased in narrow ducts, are surrounded by grouting materials, posing a challenge for prestress identification. To address this, the resonance-enhanced magnetoelastic (REME) method was developed for prestress monitoring. By combining magnetic-mechanical coupling theory and coupled-mode theory, the working principle of the REME method was analyzed. Prestress monitoring experiments were conducted on PC beams. The results showed a linear relationship between the prestress of the tendon and the induced voltage of the REME sensor, even in complex electromagnetic environments. Although the grouting material initially influenced the induced voltage, its influence diminished as the hydration reaction neared its end. Due to the sensitivity of the induced voltage-prestress relationship, a self-calibration method was proposed to establish this relationship. In the four-point bending loading, the time-varying prestress was evaluated with an error of less than 2 %. In addition, the REME method was applied to monitor the prestress of a continuous rigid-frame bridge. In the prestress application, the monitoring error was less than 8 % of the design tension. The results of the laboratory experiment and the field test demonstrated that the REME method can monitor the prestress of PC structures, providing a practical and reliable solution for prestress identification.