Ayako AKUTSU’s research while affiliated with Institute of Science Tokyo and other places

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Publications (11)


VIBRATION BEHAVIOR ANALYSIS AND PROPOSAL OF DETECTION METHOD FOR BASE DAMAGE IN NOISE BARRIER POSTS遮音壁支柱の基部損傷による振動挙動解析とその検知手法の提案
  • Article

December 2024

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1 Read

Japanese Journal of JSCE

Kouichi TAKEYA

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Ayako AKUTSU

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Hideaki YASUDA

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[...]

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Eiichi SASAKI

Effective inspection of noise barriers installed along expressways and high-speed railways is required since they can suffer damage due to corrosion of anchor bolts, aging of the anchorage, and external forces caused by earthquakes, typhoons, and traffic. This study focuses on the vibration behavior of noise barrier posts and experimentally reveals that asymmetric vibrations occur due to differences in base constraint conditions. Furthermore, using a multi-degree-of-freedom model with torsional springs, asymmetric vibrations were numerically replicated. As a result of investigating damage detection focusing on modal vibration frequencies and shapes, it was shown that instantaneous vibration frequencies can be identified with less than 1% error from non-contact displacement measurements. Additionally, the potential for assessing the state of anchorage based on instantaneous displacement was demonstrated.


Numerical study of phase space analysis for the development of subsurface crack detection method using pulsed eddy current

October 2024

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13 Reads


PROPOSAL OF ENERGY HARVESTING USING THERMAL ENERGY IN STRUCTURES AND ITS APPLICATION TO STEEL DECK BRIDGES構造物の熱エネルギーを利用した温度差発電の提案と鋼床版橋梁への適用

October 2024

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1 Read

Japanese Journal of JSCE

Structures receive thermal energy from solar radiation, and temperature differences occur between structural members due to differences in solar exposure and heat capacity. This study attempted to generate electricity from this structural thermal energy, particularly targeting the temperature difference between the pavement and decks of steel deck bridges. The thermal environment of a full-scale steel deck bridge specimen was measured, and a thermal conduction analysis using a finite element model was conducted to explore the structural design for efficiently transferring heat to thermoelectric modules. The installation position that is advantageous for power generation in steel deck bridges was investigated through experiments and heat conduction analysis, followed by power generation simulations. Finally, prototype thermoelectric energy harvesters were installed on the target steel deck bridge and verification experiments demonstrated the potential for utilizing thermal energy in structures.



A STUDY ON ULTRASONIC MEASUREMENT OF COATING THICKNESS ON BACKSIDE OF STEEL PLATE AND THE FAYING SURFACE IN HIGH-STRENGTH BOLTED FRICTION JOINTS WITH MACHINE LEARNING機械学習を援用した超音波計測による鋼板裏面及び高力ボルト摩擦接合継手接合面の塗膜厚さ評価の試み

November 2022

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26 Reads

Journal of Japan Society of Civil Engineers Ser A1 (Structural Engineering & Earthquake Engineering (SE/EE))

Recently, inorganic zinc-rich paints have been increasingly applied to the faying surfaces of high-strength bolted friction joints. The coating thickness of the faying surface is said to affect the slip coefficient of the bolted joint. If the coating thickness on faying surfaces of bolts in existing joints can be measured without disassembly the joints, it is possible to evaluate the structural performance of bolted joints on the basis of the current coating thickness on the faying surfaces and the slip coefficient. Furthermore, if it becomes possible to measure areas of high contact pressure, where the coating thickness changes after joining, this information could be useful for discussing the mechanism of structural performance of bolted joints. In this study, the construction of an ultrasonic measurement method with machine learning showed the feasibility of evaluating the coating thickness on the backside of a single steel plate. Subsequently, an attempt was made to evaluate the coating thickness on faying surfaces of bolts in existing joints without disassembly.


CONSTRUCTION OF REMAINING AXIAL FORCE EVALUATION METHOD BASED ON EDDY CURRENT MEASUREMENT渦電流計測に基づく高力ボルト残存軸力評価手法の構築

August 2022

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22 Reads

Journal of Japan Society of Civil Engineers Ser A1 (Structural Engineering & Earthquake Engineering (SE/EE))

High-strength bolted joints are widely used in steel bridges since they have advantages to construction, maintenance, and replacement. On the other hand, bolt axial force may decrease after tightening due to tightening method, tightening order, relaxation, traffic load, or earthquake. The remaining axial force of high-strength bolts is a factor that includes uncertainty therefore, it is important to evaluate the remaining bolt axial force. In this study, in order to evaluate the remaining axial force of high-strength bolts non-destructively and simply, a new remaining axial force evaluation method based on eddy current measurement was constructed. In the eddy current measurement, the stress change can be obtained by using the relationship between the magnetic permeability and the stress. Therefore, authors proposed the method considering the stress state of the bolt head and simply install the eddy current probe on the bolt head. In addition, considering that the bolt head is deformed by the axial force, the relationship between the output signal and the gap between the probe and the measurement target, which is an important evaluation index in eddy current measurement, has clarified, and the influence of the axial force evaluation has also investigated.


Advancement of Eddy Current Based Evaluation of Axial Force of High-Strength Bolts

January 2022

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40 Reads

IABSE Symposium Report

p>High-strength bolted joints are widely used in steel bridges. However, bolt axial force may decrease during the service life of a bridge for many reasons including relaxation, traffic load, and earthquake. Consequently, the remaining bolt axial force is considered a factor with uncertainty that is important to evaluate. In a previous study, the authors proposed an axial force evaluation method using eddy current. In this study, to apply the proposed axial force evaluation method to the actual measurements, new evaluation indices with the possibility of reducing measurement errors and simplifying measurement have been considered. The applicability of the improved method for high- strength bolts using weathering steel has also been examined. An experiment using both high- strength bolts and weathering steel high-strength bolts was conducted to investigate the possibility of evaluating the stress change due to the axial force with the new indices.</p


Eddy current based evaluation of axial force of high-strength bolts

January 2021

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87 Reads

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2 Citations

IABSE Congress Report

p>Many bridges have been in service for over 40 years and face to the repapering or reinforcing period due to deterioration. Particularly, in a high-strength bolts used for joints may be loosened due to co-rotation, corrosion, or vibration caused by the vehicles. Thus, it is important to evaluate an axial force of the high-strength bolts. In this research, an axial force evaluation of high-strength bolt using eddy current that does not require measurement preparation has been investigated. The eddy current method is capable of capturing the change in permeability of steel members due to the stress change. Further, the stress distribution of the bolt head is assumed uniform without directionality. Therefore, a numerical simulation and an experiment that measures the output signal of the eddy current probe while introducing axial force to the high-strength bolt has conducted.</p


DEVELOPMENT OF AN ADVANCED CORROSION DAMAGE EVALUATION METHOD FOR STEEL MEMBERS FOCUSED ON PHASE CHARACTERISTICS OF LOW FREQUENCY EDDY CURRENT

February 2018

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39 Reads

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3 Citations

Journal of Japan Society of Civil Engineers Ser A1 (Structural Engineering & Earthquake Engineering (SE/EE))

The authors have proposed a corrosion damage evaluation method for corroded steel members to estimate rust layer and residual thickness. In this method, detected voltage signal obtained by a low frequency eddy current of 500 Hz or less was used as an index. In this research, in order to further advance the method and to simplify the measurement system, a more sophisticated method utilizing a phase characteristic which is considered to be able to simultaneously estimation of thickness information together with the detected voltage has been investigated. Firstly, to clarify the low frequency eddy current characteristics assuming the difference in damaged condition by numerical simulation was performed. Then evaluation method focusing on the phase between the detected voltage and the input current and the detected voltage as an index to capture the differences has investigated. Based on results of all process, a corrosion damage evaluation method focused on phase characteristics which can obtain information of rust layer and residual thickness simultaneously was proposed. Finally, the applicability of proposed method was clarified by experiment.


ANALYSIS OF CORROSION DAMAGE CONDITION OF STEEL MEMBERS USING LOW FREQUENCY EDDY CURRENT TESTING

May 2017

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30 Reads

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5 Citations

Journal of Japan Society of Civil Engineers Ser A1 (Structural Engineering & Earthquake Engineering (SE/EE))

In this research, a method which is able to analyze corrosion damage condition such as local thickness reduction or formation of rust layer of steel members of steel members at same time has been investigated. Considering eddy current testing which uses especially low frequency eddy current such as 1~1000Hz, corrosion damage condition analysis method which performs inspection from only one side of steel members has investigated to become easy non-destructive testing method. Firstly, differences of dynamic magnetic field characteristics due to damage form was clarified using numerical simulation, and further data analyzing method to obtain the differences was investigated. Then sweep wave and frequency step wave were designed as induced wave and analysis using both detected voltage and wavelet coefficient was performed. Based on results of all process, a corrosion damage condition analysis method was proposed. Finally, in the applicability of proposed method was clarified by experiment.


Citations (3)


... Therefore, a different solution was proposed as follows. The developed probe consists of a coil placed inside a ferrite pot core [38][39][40][41]. The application of the core reduced magnetic flux losses and directed it directly towards the surface of the coating. ...

Reference:

Eddy Current Testing in the Quantitive Assessment of Degradation State in MAR247 Nickel Superalloy with Aluminide Coatings
Numerical study for development of subsurface crack detection using pulsed eddy current and swept frequency eddy current
  • Citing Article
  • June 2023

... Various non-destructive testing methods such as ultrasonic testing, X-ray diffraction, and eddy current testing have been developed and employed for structural health monitoring of steel structures [3][4][5][6]. Among these, the eddy current testing has been selected in the present study because it is a non-contact method that does not require the use of coupling agent nor surface preparation such as clearing off the top rust layer, thus proving itself time and cost efficient, particularly for field inspection of large structures with damages such as corrosion and cracking that are widespread [6,7]. ...

ANALYSIS OF CORROSION DAMAGE CONDITION OF STEEL MEMBERS USING LOW FREQUENCY EDDY CURRENT TESTING
  • Citing Article
  • May 2017

Journal of Japan Society of Civil Engineers Ser A1 (Structural Engineering & Earthquake Engineering (SE/EE))

... For example, wheeled robots, which are limited to inspecting horizontally flat surfaces (e.g., bridge decks) with several NDT methods, are described in [21,22]. For locations that are difficult to access, other forms of propulsion were used in which the robotic platform stays in contact with the concrete surface [23][24][25][26]. However, these robots might be limited to applications where the robot remains on a continuously smooth surface and must be manually moved around a corner (e.g., from a column to the underside of a bridge). ...

A comprehensive study on development of a small-sized self-propelled robot for bridge inspection
  • Citing Article
  • October 2016