Abstract
Steel strands are crucial components of a prestressed structure, but their performance degrades inevitably with time. Among the existing nondestructive testing methods for measuring the stress state of steel strands, ultrasonic guided wave methods have received the most research attention and are most likely to be applied to actual engineering. This work views the propagation of ultrasonic guided wave as an individual system, and the variations in the stress state in steel strands can be related to the parameters gained by the system identification model. The finite element simulation and experimental results show the propagation characteristics of the guided wave are influenced distinctly by the stress state. The index constructed by the system parameters exhibits good monotonic linear with stress level variation, and the slope of the fitted line from experimental data is similar to the simulation result. The sensor placement and loading path have a limited effect on the stress state and the proposed index.
Highlights
Prestressed steel strands are used widely in civil engineering buildings and are the most important mechanical components of long-span bridges, acting as the main prestressed tendons of girder bridges, suspenders of arch bridges, and cables of cable-stayed bridges
Stress measuring of steel strands based on the ultrasonic guided wave is conducted mostly using the theory of cylindrical waveguide, but the di erence between those two waveguides is obvious, such as the contact condition among wires and energy leaks at the contact area, which enhances the di culty in establishing a theoretical resolution in steel strands
The propagation of the guided wave in steel strands is considered as an individual system and the parameters of this system are extracted using the system identi cation model. ese parameters are used to propose a stress index
Summary
Prestressed steel strands are used widely in civil engineering buildings and are the most important mechanical components of long-span bridges, acting as the main prestressed tendons of girder bridges, suspenders of arch bridges, and cables of cable-stayed bridges. While the anticorrosion performance is enhanced, inspecting and monitoring the steel strands during periodical inspections can be difficult. E detection and evaluation of the stress of in-service steel strands have long been a technical problem in the field of civil engineering. E relatively mature technology for measuring the stress of steel strands focuses on the detection of stress increment and should adopt embedments in its early stage, making it difficult to be applied to in-service prestressed and cable-supported bridges [1]. E change in guided wave velocity has been applied to monitor stress in plates with biaxial loads [2], bolts (to verify tightening) [3], rails [4,5,6], steel strands [7,8,9], grouted tendons [10], and pipes [11]. Chen et al [13] conducted an early study on the fundamental longitudinal guided model (0, 1) excited within the individual wires of a strand
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