• Smart Structures and Systems
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• v.17 no.1
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• pp.107-122
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• 2016

We propose an effective methodology using electromechanical impedance characteristics for estimating the remaining tensile force of tendons and simultaneously detecting damages of the anchorage blocks. Once one piezoelectric patch is attached on the anchor head and the other is bonded on the bearing plate, impedance responses are measured through these two patches under varying tensile force conditions. Then statistical indices are calculated from the impedances, and two types of relationship curves between the tensile force and the statistical index (TE Curve) and between statistical indices of two patches (SR Curve) are established. Those are considered as database for monitoring both the tendon and the anchorage system. If damage exists on the bearing plate, the statistical index of patch on the bearing plate would be out of bounds of the SR curve and damage can be detected. A change in the statistical index by damage is calibrated with the SR curve, and the tensile force can be estimated with the corrected index and the TE Curve. For validation of the developed methodology, experimental studies are performed on the scaled model of an anchorage system that is simplified only with 3 solid wedges, a 3-hole anchor head, and a bearing plate. Then, the methodology is applied to a real scale anchorage system that has 19 strands, wedges, an anchor head, a bearing plate, and a steel duct. It is observed that the proposed scheme gives quite accurate estimation of the remaining tensile forces. Therefore, this methodology has great potential for practical use to evaluate the remaining tensile forces and damage status in the post-tensioned structural members.

• Smart Structures and Systems
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• v.15 no.1
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• pp.99-117
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• 2015

The Stonecutters Bridge (SCB) in Hong Kong is the third-longest cable-stayed bridge in the world with a main span stretching 1,018 m between two 298 m high single-leg tapering composite towers. A Wind and Structural Health Monitoring System (WASHMS) is being implemented on SCB by the Highways Department of The Hong Kong SAR Government, and the SCB-WASHMS is composed of more than 1,300 sensors in 15 types. In order to establish a linkage between structural health monitoring and maintenance management, a Structural Health Rating System (SHRS) with relevant rating tools and indices is devised. On the basis of a 3D space frame finite element model (FEM) of SCB and model updating, this paper presents the development of an SHR-oriented 3D multi-scale FEM for the purpose of load-resistance analysis and damage evaluation in structural element level, including modeling, refinement and validation of the multi-scale FEM. The refined 3D structural segments at deck and towers are established in critical segment positions corresponding to maximum cable forces. The components in the critical segment region are modeled as a full 3D FEM and fitted into the 3D space frame FEM. The boundary conditions between beam and shell elements are performed conforming to equivalent stiffness, effective mass and compatibility of deformation. The 3D multi-scale FEM is verified by the in-situ measured dynamic characteristics and static response. A good agreement between the FEM and measurement results indicates that the 3D multi-scale FEM is precise and efficient for WASHMS and SHRS of SCB. In addition, stress distribution and concentration of the critical segments in the 3D multi-scale FEM under temperature loads, static wind loads and equivalent seismic loads are investigated. Stress concentration elements under equivalent seismic loads exist in the anchor zone in steel/concrete beam and the anchor plate edge in steel anchor box of the towers.

• Journal of the Korean Geosynthetics Society
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• v.22 no.4
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• pp.17-26
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• 2023

To consider the risk of damage and fracture of P.C strands, the existing post-maintenance system alone has the limitations, hence it is necessary to quantitatively evaluate and predict the deterioration, durability and safety of facilities and establish a reasonable maintenance system considering the asset value of facilities. Therefore, it is worth considering a preventive maintenance plan that allows proactive measures to be taken before a major defect occurs in the temporary anchor. This study devised a preventive over tension method, reviewed its effectiveness through design and field tests, by calculating the resistance factors by performing a reliability-based optimization design. At this time, the over tension anchor method was evaluated using the ratio of the residual tension force after the fracture of P.C strands to the effective tension force before the fracture of P.C strand, followed by the resistance factor calculated by the optimal solution for each random variables using Excel solver and applying it to the limit state equations. As a result of the study, if the over tension ratio is 125% to 130%, the remaining strands showed a high resistance effect even after the fracture of P.C strand. As a result of the optimization design, it was found that it is appropriate to apply the load factor (γ) of 1.25, and the resistance factors of Φ₁, Φ₂, Φ₃ as 0.7, 0.5, 0.6.

• Tunnel and Underground Space
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• v.34 no.3
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• pp.218-230
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• 2024

Recently, many studies have been conducted for safety management in construction sites by incorporating computer vision. Anchor box parameters are used in state-of-the-art deep learning-based object detection and segmentation, and the optimized parameters are critical in the training process to ensure consistent accuracy. Those parameters are generally tuned by fixing the shape and size by the user's heuristic method, and a single parameter controls the training rate in the model. However, the anchor box parameters are sensitive depending on the type of object and the size of the object, and as the number of training data increases. There is a limit to reflecting all the characteristics of the training data with a single parameter. Therefore, this paper suggests a method of applying multiple parameters optimized through data split to solve the above-mentioned problem. Criteria for efficiently segmenting integrated training data according to object size, number of objects, and shape of objects were established, and the effectiveness of the proposed data split method was verified through a comparative study of conventional scheme and proposed methods.

• International journal of advanced smart convergence
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• v.11 no.4
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• pp.1-9
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• 2022

The recent development of information and communication technology is also affecting audio/video systems used in industry. The audio/video device configuration system changes from analog to digital, and the network-based audio/video system control has the advantage of reducing costs in accordance with system operation. However, audio/video systems released on the market have limitations in that they can only control their own products or can only be performed on specific platforms (Windows, Mac, Linux). This paper is a study on a device (Network Audio Video Integrated Control: NAVICS) that can integrate and control multiple audio / video devices with different functions, and can control digitalized audio / video devices through network and serial communication. As a result of the study, it was confirmed that individual control and integrated control were possible through the protocol provided by each audio/video device by NAVICS, and that even non-experts could easily control the audio/video system. In the future, it is expected that network-based audio/video integrated control technology will become the technical standard for complex audio/video system control.

• Journal of the Earthquake Engineering Society of Korea
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• v.18 no.1
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• pp.19-28
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• 2014

The seismic evaluation of electric power facilities in the switchyard of nuclear power plants is currently insufficient. In order to evaluate the seismic performance of lightning arrester subjected to four types of earthquake (near- and far-fault earthquakes, NEHRP Site Class A&B and D earthquakes), seismic fragility analysis using maximum likelihood estimation is performed considering various damage states. The comparison of the seismic fragility curves for three main parts of lightning arrester that are the busing, anchor and steel frame, reveals that the failure of lightning arrester is governed by the bushing damage mode such as porcelain cracking.

• IEIE Transactions on Smart Processing and Computing
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• v.6 no.2
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• pp.93-101
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• 2017

This paper proposes an algorithm for adaptive loop filter (ALF) complexity reduction in the decoding process. In the original ALF algorithm, filtering for I frames is performed in the frame unit, and thus, all of the pixels in a frame are filtered if the current frame is an I frame. The proposed algorithm is designed on top of the local gradient calculation. On both the encoder side and the decoder side, homogeneous areas are checked and skipped in the filtering process, and the filter coefficient calculation is only performed in the inhomogeneous areas. The proposed algorithm is implemented in Joint Exploration Model (JEM) version 3.0 future video coding reference software. The proposed algorithm is applied for frame-level filtering and intra configuration. Compared with the JEM 3.0 anchor, the proposed algorithm has 0.31%, 0.76% and 0.73% bit rate loss for luma (Y) and chroma (U and V), respectively, with about an 8% decrease in decoding time.

• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.90.2-90.2
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• 2010

흙막이 굴착 및 절취사면의 보강공법으로 많이 적용되고 있는 앵커의 장력을 측정하는 전기저항식 로드셀과 스트레인게이지, 바이브레이팅 와이어 (vibrating wire) 타입의 모니터링 방법은 안전관리를 위한 장기적인 모니터링에 한계를 가지고 있어 이를 개선할 수 있는 방안으로 광섬유 센서를 이용하여 강연선의 변형률을 측정할 수 있는 스마트 텐던이 개발되었다(김재민 등, 2007). 앵커를 구성하는 7연 강연선(텐던)의 중앙케이블에 삽입된 광섬유브래그격자(Fiber Bragg Grating ; FBG)센서는 기존 스트레인게이지 타입에 비해 크기가 작고 내구성이 우수하며 전자기파에 의한 노이즈 발생이 없고 하나의 리드선으로 다중점 측정(multiplexing)이 가능하여 장기모니터링에 효과적인 장점이 있다. 본 연구에서는 FBG센서를 내장한 스마트 텐던을 실대형(Prototype) 앵커(L=11.5m)에 적용하여 현장 인발실험에 의해 시공중 장력 모니터링을 수행하고 로드셀 측정결과와 비교하였고 정착부에 설치된 FBG 센서로부터 앵커의 하중전이 계측을 수행하였다.

• Journal of the Korean GEO-environmental Society
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• v.25 no.4
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• pp.29-35
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• 2024

This is an analytical study to confirm the passive resistance effect before post-tensioning of steel bar anchors. When using a steel bar as a permanent anchor, if displacement occurs within the slope even before the head load is applied, the displacement is suppressed by the passive resistance caused by the interaction between the steel bar, grout, and surrounding soil. Accordingly, the shape of the failure surface and changes in the safety factor were examined using limit equilibrium analysis and finite element analysis targeting sites where steel bar anchors were actually applied. It was found that the safety factor of the slope reinforced with steel bar anchors is 2.02 using finite element analysis, which is about 5.9% smaller than 2.14 using limit equilibrium analysis. Also, the location of the failure surface was found to be deeper compared to the unreinforced slope. Likewise, the factor of safety has a 153% and 163% increase using finite element method and limit equilibrium analysis, respectively. In addition, the maximum displacement occurs in the lower unreinforced section within the slope, and the displacement is found to be reduced by 42 to 83% at the location where the steel bar anchors are installed.

• Smart Media Journal
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• v.9 no.2
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• pp.9-15
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• 2020

In this paper, we propose a network model composed of Multi path Encoder-Decoder branches that can recognize each instance from the image. The network has two branches, Dot branch and Segmentation branch for finding the center point of each instance and for recognizing area of the instance, respectively. In the experiment, the CVPPP dataset was studied to distinguish leaves from each other, and the center point detection branch(Dot branch) found the center points of each leaf, and the object segmentation branch(Segmentation branch) finally predicted the pixel area of each leaf corresponding to each center point. In the existing segmentation methods, there were problems of finding various sizes and positions of anchor boxes (N > 1k) for checking objects. Also, there were difficulties of estimating the number of undefined instances per image. In the proposed network, an effective method finding instances based on their center points is proposed.