Application of external magnetization EM technique for diagnosis of residual prestress in aged PSC structures (Conference Presentation)

Abstract

The actual tensile force of pre-stressed (PS) tendons of a pre-stressed concrete (PSC) girder is one of the important factors for evaluating the performance of PSC girder bridges. However, it is hard to measure the residual tensile force of outdated PSC bridges because the PS tendons were buddied in the concrete and the any sensory systems were not installed. To measure the tensile force of the outdated PSC girder bridges, this study proposed an external magnetization based tensile force estimation method using external magnetization sensor(EMS). The magnetic hysteresis of PS tendons is changed according to the residual tensile force. To measure the magnetic hysteresis of outdated PSC girder, the EMS was designed to concentrate the magnetic field to the PS tendons which located inside of girder. The 8 magnetization coils were installed to the U shape frame which can cover the both side of PSC I-shape girder and the designed currents were inputted to each magnetization coils to concentrate magnetic field. The flux density of magnetized PS tendon was measured hall sensors which located at the frame. To verify the proposed method, the in-field tests were performed. The magnetic hysteresis of PSC girder with difference tensile forces were measured using EMS and the feature was extracted to estimate residual tensile force of PSC girder. The estimated residual tensile forces were compared with reference tensile forces measured by hydraulic jacking machine which installed anchorage of PSC girder specimen. According to the measurement results, the proposed method can be a one of the solutions to measure the residual tensile force of outdated PSC I-shape girder bridges.