3D Radar Reveals Defects Within Bridges - IEEE Spectrum

 

This prototype 3D ground penetrating radar system uses
sophisticated software to discover potential bridge
defects otherwise buried in concrete. Xinghua Shi et al./IEEE

 

3D Radar Reveals Defects Within Bridges - IEEE Spectrum

summary

This article discusses a new ground-penetrating radar (GPR) system developed by researchers in China that can create 3D images of the interior of reinforced concrete bridges to detect defects and anomalies. The key points are:

1. Bridges require extensive inspection techniques to ensure safety, including visual inspection, ultrasonic testing, infrared thermography, and radar.
2. Radar is a good non-invasive method, but challenges exist when trying to penetrate the steel mesh within reinforced concrete bridges.
3. The researchers developed a 3D GPR system that uses a 1.3 GHz antenna array and multi-channel radar control to create detailed 3D images of the interior concrete structure, including reinforcement, pipes, and defects.
4. The system was tested successfully on both lab samples and real-world bridge structures, demonstrating its ability to detect various anomalies and quality issues within the reinforced concrete.
5. While interpreting the 3D images still requires expertise, the researchers plan to use deep learning in the future to automatically classify different types of defects.
6. The new 3D GPR technology provides an advanced and reliable tool for bridge inspection and monitoring, helping to ensure the safety and quality of these critical infrastructure assets.

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Many people around the world cross bridges on a daily basis without a second thought–but behind the scenes, engineers are conducting a battery of tests to ensure bridge safety. To support these efforts, one group of researchers in China has created a new radar device that can penetrate the concrete of bridges to create 3D images of its interior. The new tech, which was able to reconstruct detailed internal images of real-world bridges, is described in a study published May 9 in IEEE Sensors Journal.

Currently, there are several bridge inspection techniques for assessing and monitoring the condition of bridge structures, including visual inspection, ultrasonic testing, infrared thermography, aerial inspection, and radar.

Radar is an especially good method for non-invasive testing of bridges, whereby electromagnetic signals are directed toward it. “These pulses penetrate the surface and bounce back when they encounter changes in material density, like defects or voids in the reinforced concrete of a bridge,” explains Xinghua Shi, a senior engineer at the China Research Institute of Radiowave Propagation and PhD candidate at Xi’an Jiaotong University.

However, there are some challenges when it comes to using the technology to probe inside reinforced concrete. Due to the presence of steel mesh in bridges, low-frequency radar may not be able to effectively penetrate the steel mesh and detect defects below it.

To overcome these challenges, Shi and his colleagues sought to develop a novel 3D ground-penetrating radar device that works at frequencies of 1.3 Gigahertz. It emits radar signals that emanate out at a wide range of angles. Although this approach produces background noise and scattered return signals, the researchers’ data analysis package translates the returning signals into 3D images of defects lurking behind the steel mesh.

Next, the researchers tested their device in the lab using a slab of reinforced concrete with known defects, which the system detected. “Our system produces detailed images of subsurface structures, allowing engineers to visualize defects, voids, and other anomalies within the reinforced concrete,” Shi says, noting that when his team went on to test the device on real bridges with pre-stressed concrete T-beams, its ability to detect defects was “outstanding.”

Despite the steel mesh in the bridge’s concrete structure, the system developed by Shi and his colleagues generates 3D images up to 60 centimeters deep, via a portable device that boasts real-time imaging.

Shi also notes that interpreting data from their device still requires a high level of expertise. “Identifying and distinguishing between different types of anomalies in the radar images can be challenging,” he says. “[While] 3D imaging can provide a more intuitive visualization of steel reinforcement, other anomalies may require careful human judgment for identification.”

Therefore, he hopes to use deep learning to analyze the images and provide automatic classification of defects in future work.

“Reinforced concrete, being the cornerstone of bridge structures, plays a pivotal role in ensuring their quality and safety. It is imperative to introduce new, convenient, efficient, and accurate non-destructive testing technologies and equipment to identify defects and weaknesses in the reinforced concrete components of bridges,” he says.

X. Shi, A. Zhang, G. Han, Y. Yin and W. Chen, "The Design of 3D Ground Penetrating Radar System for Bridge Inspection," in IEEE Sensors Journal, doi: 10.1109/JSEN.2024.3396467.

Abstract: Highway bridges are primarily reinforced concrete structures. They have multi-layer steel mesh sheets, corrugated pipes, and steel strands inside. As a result, detecting defects in bridge concrete structures requires high technical expertise and can be challenging. 

This paper presents a new device of Ground penetrating radar designed specifically for highway bridge inspection. It employs antenna array technology, multi-channel radar control technology, and real-time 3D data acquisition and display technology to achieve reliable detection of various concrete structures commonly found in bridges. Using a 1.3 GHz central frequency antenna array and a multi-channel control unit, the system enables simultaneous surveying along five lines, the detection depth can exceed 600 mm in concrete. This significantly enhances detection efficiency. 

By employing specialized software processing, the detection results are presented in a specific and visually com-prehensive 3D format. Moreover, the system provides 3D slice images from any position and direction, facilitating the interpretation of detection results for various targets, including reinforcement layout, protective layer thickness, corrugated pipes, steel strands, and other quality defects. It provides advanced and reliable technical means for construction quality control and bridge health monitoring of highway bridges. The results indicate that the device performs well not only in controlled experimental environments, but also in real-world bridge structure environments.

keywords: {Bridges;Concrete;Antenna arrays;Antennas;Inspection;Radar antennas;Dipole antennas;Ground Penetrating Radar (GPR);Bridge Inspection;Array antenna;Surface rendering},
URL: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10528240&isnumber=4427201


 Boldrin, P.; Fornasari, G.; Rizzo, E. Review of Ground Penetrating Radar Applications for Bridge Infrastructures. NDT 2024, 2, 53–75. https://doi.org/10.3390/ndt2010004

Abstract: Infrastructure bridges play a crucial role in fostering economic and social development. However, the adverse effects of natural hazard and weather degradation, coupled with escalating rates of traffic, pose a significant threat. The resultant strain on the structure can lead to undue stress, elevating the risk of a critical asset failure. Hence, non-destructive testing (NDT) has become indispensable in the surveillance of bridge infrastructure. Its primary objectives include ensuring safety, optimizing structural integrity, minimizing repair costs, and extending the lifespan of bridges. NDT techniques can be applied to both existing and newly constructed bridge structures. However, it is crucial to recognize that each NDT method comes with its own set of advantages and limitations tailored to specific tasks. No single method can provide an effective and unequivocal diagnosis on its own. Among the various NDT methods, Ground Penetrating Radar (GPR) has emerged as one of the most widely employed techniques for monitoring bridges. In fact, recent technical regulations now mandate the use of GPR for bridge monitoring and characterization, underscoring its significance in ensuring the structural health and longevity of these critical infrastructures. Ground Penetrating Radar (GPR) stands out as one of the most highly recommended non-destructive methods, offering an efficient and timely assessment of the structural conditions of infrastructure. Recognizing the pivotal role of non-destructive testing (NDT) in this context, this paper aims to elucidate recent scientific endeavors related to the application of GPR in bridge engineering structures. The exploration will commence with a focus on studies conducted both at the model level within laboratory settings and on real cases. Subsequently, the discussion will extend to encompass the characterization and monitoring of the bridge’s main elements: slab, beam, and pillar. By delving into these scientific experiences, this paper intends to provide valuable insights into the efficacy and applicability of GPR in assessing and ensuring the structural integrity of bridges. This paper provides a concise survey of the existing literature on the application of Ground Penetrating Radar (GPR) in the assessment of bridges and viaducts constructed with masonry and reinforced concrete, taking into account papers of journal articles and proceedings available on open databases. Various approaches employed in both laboratory and field settings will be explored and juxtaposed. Additionally, this paper delves into discussions on novel processing and visualization approaches, shedding light on advancements in techniques for interpreting GPR data in the context of bridge and viaduct evaluations.

 Summary

This review article provides an overview of the use of ground-penetrating radar (GPR) for the assessment and monitoring of masonry and reinforced concrete bridges. The key points are:

1. GPR is a widely used non-destructive testing technique for evaluating the condition of bridge infrastructure, including detecting defects, corrosion, and structural anomalies.

2. For masonry bridges, GPR has been applied to identify unknown geometries, analyze restoration and moisture conditions, assess foundations, and detect cracks and voids.

3. For reinforced concrete bridges, GPR is used to locate reinforcement bars, evaluate concrete cover thickness, and identify areas of deterioration and delamination.

4. The review covers both laboratory studies on concrete samples as well as real-world case studies on actual bridge structures.

5. Challenges in interpreting GPR data due to the complexity and heterogeneity of bridge materials are discussed, along with the use of numerical modeling and advanced processing techniques to enhance data analysis.

6. While most research has focused on bridge slabs and beams, the review highlights the need for more investigation into the application of GPR for assessing bridge pillars/piers, which play a critical structural role.

7. The article also reviews emerging data processing and visualization methods, including automated algorithms and circular data representation, to improve the interpretation of GPR results for bridge inspection and maintenance.

8. Overall, the review demonstrates the value of GPR as a powerful non-destructive tool for comprehensive bridge evaluation and condition assessment, supporting evidence-based decision making for infrastructure management.

 The article discusses the use of various ground-penetrating radar (GPR) systems and instruments, including:

1. MALA Geoscience GPR system with 1.6 GHz and 900 MHz antennas
2. GSSI SIR-20 GPR system
3. GSSI SIR-3000 GPR system with 1.5 GHz, 1.6 GHz, and 2.6 GHz antennas
4. RAMAC GPR system with 250 MHz, 500 MHz, and 800 MHz antennas
5. IDS Alladin GPR system with 2 GHz antennas
6. IDS Georadar DXG1820 system with an antenna array from 200 MHz to 3 GHz
7. MALÅ ProEx GPR system with 2.3 GHz antennas
8. Penetradar IRIS GPR system with 100 Hz sampling frequency
9. Georadar Research Pty Ltd. GPR system with 1.5 GHz antennas
10. GSSI BridgeScan GPR system
11. SFR GPR system

The article highlights that the selection of the appropriate GPR frequency and antenna configuration is crucial for optimizing the depth of penetration, resolution, and suitability for the specific bridge inspection requirements.