Small-Scale Void-Size Determination in Reinforced Concrete Using GPR

Yong Yang,Rongzhe Li,Weigang Zhao,Deli Yan,Junwei Lu

doi:10.1155/2020/2740309

Yong Yang, Rongzhe Li + Show 3 more

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https://doi.org/10.1155/2020/2740309

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Journal: Advances in Civil Engineering	Publication Date: Jun 6, 2020
Citations: 8	License type: CC BY 4.0

Affiliation: Shijiazhuang Tiedao University

Abstract

The detection and evaluation of void in concrete are imperative issues in health monitoring of civil engineering. However, the void is difficult to be detected at its early stage of formation on account of its small scale and concealment. Although, in view of the remarkable performance such as precision and continuity, ground penetrating radar (GPR) is widely employed in some special fields of nondestructive testing, the strong reflection of rebar which could submerge the echo of void is now a stumbling block for the application of GPR in reinforced concrete. In order to develop the tactic of small-scale void-size determination with considerable noise originated from rebar, a two-stage regression method is proposed in this study. First, a superposition model of target echoes was established to analyze the relationship between the space-time distribution and spectrum of the rebar echo and the void echo, and a curvelet transform was employed to reduce the strong reflection of the rebar. Then, the echo amplitude of small-scale void was investigated, and a regression method was put forward to determine the void size of small scale. Finally, forward simulation and experiment were carried out to verify the feasibility of the proposed method. Results demonstrated that the spectral distribution of the rebar echo is significantly higher than that of the void echo. The curvelet-based low-pass filter can effectively ensure the discrimination of void echo. The regression method performs a high-accuracy void-size determination with more than 90% in small scale.

Highlights

In view of the remarkable performance such as durability and bearing capacity, reinforced concrete (RC) is widely used in high-rise buildings, municipal projects, dams, tunnels, high-speed railways, and other structures
D, of the rebar is small, and the interval between the rebar is far larger than d, the echo amplitude of the void defect is not disturbed by the rebar echo. erefore, the profile of ground penetrating radar (GPR) can be expressed as
Based on spectral analysis and the relationship investigation between echo amplitude and dimension characterization of small-size void, a two-stage regression method was proposed to develop the tactic of GPR-based small-scale void-size determination in RC structure, and the main conclusions are as follows: (1) e strong reflection interference of the rebar echo is the main obstacle in the identification of a void defect in RC structures

Summary

Introduction

In view of the remarkable performance such as durability and bearing capacity, reinforced concrete (RC) is widely used in high-rise buildings, municipal projects, dams, tunnels, high-speed railways, and other structures. In the existing detection methods for RC structure internal defects, core drilling and nondestructive testing are most widely used. In the impact echo method, the detection precision is related to the ratio of the depth and void size, Advances in Civil Engineering and the resolution is relatively poor. Zanzi and Arosio obtained GPR echo data using two antennas with vertical and horizontal polarization, and they developed a method based on radar cross section (RCS) to determine the size of the steel bar [6]. Is study focuses on small-scale void defect detection and determination in RC structures.

Target Echo Analysis

Simulation and Experiment

Findings

Conclusion