Frontier of Research

Vol.3
Non-Destructive Testing -- Inspection techniques for soundness of infrastructure without damage

Construction and Maintenance Engineering LaboratoryLecturer Shinya Uchida

[2014/02/04]

In Japan, chances to draw attention from the community on the problem of deteriorating infrastructure are increasing, as exemplified by the accident of the ceiling boards falling down in Sasago Tunnel on December 2nd, 2012. In situations where the budget devoted to public infrastructure maintenance is not sufficient, to continue maintenance in a reasonably efficient way has become a pressing issue. In order to continue proper maintenance over a long period of time, concrete structures need periodic physical examinations, just like humans do. Use of non-destructive testing is quite effective to make reasonable plans for maintenance in existing concrete structures. Therefore, the role of non-destructive inspection to keep safety and reliability of concrete structures is supposed to become greater.

Non-Destructive Testing

Non-Destructive testing is an inspection techniques that uses elastic waves, electromagnetic waves, electrochemical properties, and other means in order to investigate about the internal defects of the structure without damaging it.

Elastic Wave Methods

A non-destructive test using elastic wave is called elastic wave methods. In order to investigate about the internal defects of the concrete members, a frequency spectra calculated by frequency analysis of the received waveform, measuring propagation time and maximum amplitude (wave energy) is used.

Elastic wave methods - evaluation indices

Figure 1 - Elastic wave methods - evaluation indices


This method can be divided into four groups: ultrasonic method, impact elastic-wave method, impact acoustics method, and AE method.

Classification of elastic wave methods

Figure 2 - Classification of elastic wave methods


Electromagnetic Pulse Method

Electromagnetic pulse method is one of the impact elastic-wave method. In this method, the magnetic materials such as steel bars or anchor bolts inside the concrete member are vibrated without direct contact using electromagnetic force generated by exciting coil. Magnetic field is generated instantaneously around the coil by flowing of large pulsed current. The elastic wave caused by vibration of magnetic material is received by sensor installed at the surface of target member. By analysis of received waveform, defects on interface of magnetic material can be evaluated by non-destructive testing.

Figure 3 - Overview of electromagnetic pulse method

Figure 3 - Overview of electromagnetic pulse method


Electromagnetic pulse method - Rebar excitation

Analysis-Aided Elastic Wave Method and Case Study

Elastic wave method is a non-destructive testing to evaluate quality and internal defects of concrete. The range of application of this method is large and therefore, particularly in actual concrete structures, it is expected to be actively investigated. However, in some cases, it is found that evaluation results by this method are not similar to those of visual inspection such as drilling in the actual field. Because condition of existing structures (form or materials) or cracks or internal defects of concrete members are different for each target. Therefore, measurement condition of elastic wave method should be properly set for each concrete members. Against this background, in order to evaluate defects in concrete members accurately and efficiently, before measurements by elastic wave methods, impact response analysis is applied to determine input and detection techniques of elastic wave, evaluation indices and detection performance of defects (range of application).

Figure 4 - Overview of analysis-aided elastic wave method

Figure 4 - Overview of analysis-aided elastic wave method


Figure 5 - Analysis results: distribution of magnetic force (electromagnetic force) acting on the sheath by electromagnetic Pulse Method

Figure 5 - Analysis results: distribution of magnetic force (electromagnetic force) acting on the sheath by electromagnetic Pulse Method


Taking advantage of the above ideas, the purpose of this study is to establish measurement technique by electromagnetic pulse method in order to evaluate soundness of adhesive portion around anchor bolts in concrete by impact response analysis.

Equipment developed to measure type of adhesive used and construction anchor (Joint research done by West Nippon Expressway Company, Osaka University, and Ritsumeikan University)

Measurement system developed to evaluate soundness of adhesive portion around anchor bolts in concrete (Joint research performed by West Nippon Expressway Company, Osaka University, and Ritsumeikan University)

Professor’s profile

Construction and Maintenance Engineering Laboratory - Lecturer

Shinya Uchidaうちだ しんや

In 2001, he graduated from Gifu University, and in that same year began his master's course, conducting research on monitoring methods for setting and hardening of concrete by ultrasonic method. After completing graduate school he began to work for PS Mitsubishi Construction Co., Ltd., and enrolled at Gifu University's doctoral program in 2005.
He became a research fellow at the Japan Society for the Promotion of Science studying horizontal cracks that occur in the interior of RC slabs of highway bridges using elastic wave methods, and using non-destructive testing for evaluating the condition of PC grout on PC members of railway bridges. From 2009 to 2011 at Osaka University Graduate School, and from 2011 to 2013 at Saga University Graduate School, he worked on developing non-destructive testing using electromagnetic pulse method, as well as focusing on building prediction methods for strength of existing RC members exposed to marine environment based on non-destructive testing. He began at Ritsumeikan University in 2013, and is currently working on developing analysis-aided elastic wave methods, non-destructive testing apparatus and tools for visualizing non-destructive testing results.
Through education and research, I want to help students improve their ability to think logically, communication skills, the mental strength to not give up until the end, the ability to gather information, presentation skills, and writing ability. Especially in research, we give the students the chance to participate in projects and joint research with industry, government, and off-campus academia. Ensuring our flexibility in allowing students to participate in diverse ways is just one of the ways we make a great effort in developing human resources who can play an active part in the real world.
Ritsumeikan's goal is to train the leaders of tomorrow about the maintenance of our infrastructure in Japan.
We hope to inspire students to find their own dreams to follow and make a difference in the world.

http://research-db.ritsumei.ac.jp/Profiles/104/0010309/profile.html

内田 慎哉 講師

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