A Stress Measurement Method for Steel Strands Based on LC Oscillation

Can Yuan,Xingxing Li,Zongbao Liang,Wenzhao Li,Chong Tu,Benniu Zhang,Zhixiang Zhou,Dongjun Chen

doi:10.1155/2018/1584903

Abstract

The prestress loss is one of the main factors affecting the safety of prestressed concrete structure. While the detecting signals like sound and light are difficult to spread in steel strands, there is no effective method for prestress detection of the bonded prestressed steel strands in existing structures yet. In this paper, taking into consideration that the electromagnetic oscillation characteristic can make the signal propagate effectively on the bonded prestressed steel strands, a nondestructive prestress detection method based on the electromagnetic effect to detect oscillation frequency is proposed. In a detection circuit, the steel strands are simulated as an inductance component, in which an induced electromagnetic signal passes through the steel strands to form resonance. And then, a frequency meter is used to detect the oscillation frequency of the resonant circuit. The oscillation frequency is supposed to have relationship with the prestress loading on the steel strands. A section of steel strands with a length of 1.2 m is adopted to test the correlation of stress and oscillation frequency. Both the theoretical and experimental results show that the resonant frequency of the circuit decreases with the increase of the stress of the strand and is linear in a certain range.

Highlights

Prestressed concrete structures are widely used in civil engineering and hydraulic engineering because of their advantages of reducing deformation, improving bearing capacity and cracking resistance
Saiedi et al [9] have tested the performance of three 13-year-old concrete T-beams in the low-temperature environment. eir results show that the prestressed structures which were exposed to low temperature may reduce the strength by about 19%
The prestress loss has not been solved well, so it is important to detect the prestressed concrete structure effectively. e traditional method for detecting the prestressing force of the steel strand in the existing structure is complex, and the equipment that is used to obtain the prestressing force is expensive and inconvenient to carry. e vibration frequency of the oscillating circuit is used to detect the loss of prestress in the steel strand, which avoids the damage to the structure caused by the prestress detection and provides a timely and accurate method for detecting prestress

Summary

Introduction

Prestressed concrete structures are widely used in civil engineering and hydraulic engineering because of their advantages of reducing deformation, improving bearing capacity and cracking resistance. A series of studies [3,4,5,6,7,8] show that the performance of prestressed concrete structures will be affected by the prestressed reinforcement corrosion and crack propagation. The cracks of the prestressed structure will further expand It will reduce the stiffness of the concrete structure. Eir results show that the prestressed structures which were exposed to low temperature may reduce the strength by about 19%. Hou et al [10] have done a series of studies on the mechanical performance of the prestressing tendons at 20–800°C. In their findings, the strength and stiffness loss of prestressed tendons are slower than those of traditional prestressed steel strands. The prestress will decrease as the time goes by

Methods

Results

Conclusion