• Smart Structures and Systems
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• v.30 no.6
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• pp.571-582
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• 2022

Optimal life-cycle management is a challenging issue for deteriorating regional bridges. Due to the complexity of regional bridge structural conditions and a large number of inspection and maintenance actions, decision-makers generally choose traditional passive management strategies. They are less efficiency and cost-effectiveness. This paper suggests a deep reinforcement learning framework employing double-deep Q-networks (DDQNs) to improve the life-cycle management of deteriorating regional bridges to tackle these problems. It could produce optimal maintenance plans considering restrictions to maximize maintenance cost-effectiveness to the greatest extent possible. DDQNs method could handle the problem of the overestimation of Q-values in the Nature DQNs. This study also identifies regional bridge deterioration characteristics and the consequence of scheduled maintenance from years of inspection data. To validate the proposed method, a case study containing hundreds of bridges is used to develop optimal life-cycle management strategies. The optimization solutions recommend fewer replacement actions and prefer preventative repair actions when bridges are damaged or are expected to be damaged. By employing the optimal life-cycle regional maintenance strategies, the conditions of bridges can be controlled to a good level. Compared to the nature DQNs, DDQNs offer an optimized scheme containing fewer low-condition bridges and a more costeffective life-cycle management plan.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.09a
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• pp.61-69
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• 2000

It is not easy to find a good soil condition due to the shortage of suitable land for construction work. The earth structure and buildings can be constructed over the soft soil. The soft soil must be treated either using the reinforcement element or dewatering. Most of land reclamation projects are being implemented along the south coast or west coast of the Korean Peninsula. The soils in these areas are covered with the soft marine clay, so soil and site improvement is the most important things to do. Pile foundation at the bottom of embankment can be constructed either in the soft ground or in the soil contaminated area. The purpose of this research is to develop "geogrid-reinforced piled embankment method" to prevent the differential settlement and increase the bearing capacity of soil. In this study, the effectiveness of the geogrid-reinforcement was studied by varying the space between piles and reinforcement conditions. Also, the geotechnical engineering properties of the embankment material and foundation soil were determined through the laboratory tests as well as the field tests. As a result, the site that the pile-spacing S = 3b with geogrid reinforcement is the most effective to reduce the differential settlement and increase load bearing capacity.

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.514-527
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• 2007

Earth reinforcement techniques are used worldwide and offer proven solutions to a wide range of geotechnical engineering problems. Here in this paper, recent developments of three major reinforced soil retaining wall methods in Japan were introduced in order to show how the current situation of this technique in Japan is. And the statistical data for the volume of the use was also shown, such as the total volume of the use, the scales of the structures, layout of the earth reinforcement, fill materials, and foundation conditions. Some of the case histories were also introduced with photographs and figures. And then, as one of recent research activity by the author, the study on the application of X-ray CT for the problem of earth reinforcement method combined with other method such as piling and soil improvement was introduced. In this study, a series of model test for several reinforced ground with geogrids was conducted using a newly developed test apparatus. Then, the behavior in the soil box was scanned after settlement using X-ray CT scanner. Based on these test results, the reinforcing effect by the geogrids and the soil arching effect over the pile heads was discussed precisely and those are done in 3-D with nondestructive condition. Finally, the effectiveness of the use of X-ray CT scanner in geotechnical engineering was promised.

• Journal of Drive and Control
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• v.19 no.4
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• pp.110-116
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• 2022

Recently, various studies have been conducted to apply deep learning and AI to various fields of autonomous driving, such as recognition, sensor processing, decision-making, and control. This paper proposes a controller applicable to path following, static obstacle avoidance, and pedestrian avoidance situations by utilizing reinforcement learning in autonomous vehicles. For repetitive driving simulation, a reinforcement learning environment was constructed using virtual environments. After learning path following scenarios, we compared control performance with Pure-Pursuit controllers and Stanley controllers, which are widely used due to their good performance and simplicity. Based on the test case of the KNCAP test and assessment protocol, autonomous emergency steering scenarios and autonomous emergency braking scenarios were created and used for learning. Experimental results from zero collisions demonstrated that the reinforcement learning controller was successful in the stationary obstacle avoidance scenario and pedestrian collision scenario under a given condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2866-2874
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• 2000

This paper is concerned with the optimum design for external reinforcement of a nuclear reactor pressure vessel(RPV) in a severe accident. During the severe reactor accident of molten core, the temperature and the pressure in the nuclear reactor rise to a certain level depending on the initial and subsequent condition of a severs accident. The reis of the temperature and the internal pressure cause deterioration of the load carrying capacity and could cause failure of the RPV lower head. The deterioration of failure can be mitigated by the external cooling or the reinforcement of the lower head with additional structures. While the external cooling forces the temperature of an RPV to drop to the desired level, the reinforcement of the lower head can attain both the increase of the load carrying capacity and the temperature drop. The reinforcement of the lower head can be optimized to have the maximum effect on the collapse pressure and the temperature at the inner wall. Optimization results are compared to both the result without the reinforcement and the result with the designated reinforcement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.4
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• pp.179-186
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• 2008

Probing inside of concrete structures is one of the important steps in assessing condition of the structure. For the assessment, electromagnetic induction method and electromagnetic wave method are currently applied to the measurement of cover depth, and the detection of reinforcement embedded in concrete. To determine detection capability of locating reinforcement embedded in concrete, commercially available nondestructive testing (NDT) equipments have been tested. The equipments include electromagnetic wave system and electromagnetic induction system. In the tests, nine concrete specimens which have the dimensions of 1,000mm(length))${\times}$300mm(width) with thickness varying from 125mm to 150mm are used. The reinforcement are located at 45, 60, 100mm depth from the concrete surface. Horizontal reinforcement spacing has been set over 100mm. From the outcome, it is shown that error is increased as the diameter of reinforcement enlarge in case of using electromagnetic induction method. In case of using electromagnetic wave method, the detection of reinforcement embedded in deep is good in the view of reliability because of using the relative permittivity on the real cover depth.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.459-462
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• 1999

This paper presents a numerical study on the effect of live load pattern on RC flat plate under in-plane compression. Through the numerical study on various live load pattern, the load condition that governs the strength of the flat plate is determined. Effects of L.L/D.L. and arrangement of reinforcement on the behavior of the flat plate are also studied. And the efficient arrangement of reinforcement regarding to live load pattern is proposed.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.374-377
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• 2006

The measured longitudinal reinforcement tensions in the shear-critical RC beams were significantly higher than the calculated values by the beam theory. This may be attributed to the reduction of the internal-moment arm length by the development of the arch action. In this paper, the measured longitudinal reinforcement tensions in the test performed by Kim were compared with those predicted by the new truss model on the basis of the compatibility condition of the shear deformation.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.279-282
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• 2005

Experimental study is performed to investigate the variation of shear strength of reinforced concrete beams according to design parameters. The major parameters are loading condition, shear span-to-depth ratio, ratio of tensile longitudinal reinforcement, prestress and boundary rigidity.14 reinforced concrete beams without web reinforcement are tested under monotonic downward loading. The shear strength of the tested specimens were compared with the prediction by design code and Choi's method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.04a
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• pp.29-33
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• 1991

This paper reports the application study of the ground reinforement under a buried pipeline subjected to differential settlement via a finite element modelling. The Soil-reinforrement interaction helps to mimimize the differential settlement between the adjoining pipe segments. The settlement pattern and deformation slope of a pipeline have been evaluated for a boundary condition at the joint between a rigid structure and apipeline. The analysis results are compared for both non-reinforied and reinforced cases to measure the effectiveness of the soil reinforcement for restraining the settlement of the pipeline.