• Title/Summary/Keyword: structural safety diagnosis

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Estimation of Dynamic Characteristics Before and After Restoration of the Stone Cultural Heritage by Vibration Measurement (진동 측정에 의한 석조문화재 복원 공사 전·후의 동특성 추정)

  • Choi, Jae-Sung;Cho, Cheol-Hee
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.1
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    • pp.103-111
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    • 2021
  • Naju Seokdanggan, Treasure No. 49, was dismantled and reconstructed due to poor performance. During construction, the crack area was reinforced and the inclination was improved. It is necessary to analyze the stiffness changes before and after the reconstruction of these cultural properties, and to establish a database of related information. In addition, there is a need for research on a scientific non-destructive testing method capable of predicting or evaluating the reinforcing effect. In this study, a simple equation for estimating the overall stiffness of the structural system was derived from information on the elasticity coefficient and the natural frequency measured by vibration tests before and after reconstruction work, and the applicability of the equation was examined. If the stiffness of important cultural properties is regularly investigated by the suggested method, it is judged that it can be used as data to estimate the time when structural safety diagnosis is necessary or when repair or reinforcement is necessary.

Evaluation Using Dynamic Characteristic of Steel Structures under Periodical Impact Loads (주기적 충격하중을 받는 강 구조물의 구조건전성 평가)

  • Kim, Kang Seok;Nah, Hwan Seon;Lee, Hyeon Ju;Lee, Kang Min;Yoo, Kyung Seok
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.15 no.1
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    • pp.120-128
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    • 2011
  • Recently, safety diagnosis of the existing structures has been emerged as important issue. In particular, systematical and precise safety diagnostics for steel structures for power substation, have been required. Steel structures for power substation are under the periodical impact loads from operations of gas insulated switchgear. These loading condition accelerates damage and aging of structure. The objective of this research is to evaluate damage of structure under periodical impact loads. To evaluate the integrity of structures as organizing mathematical models including the dynamic characteristics of structures, Frequency Domain Decomposition method was choiced and an algorism was proposed. For verifying this methods and algorism, a mathematical model is composed of the development of a variety of reverse analysis and a signal processing technology reflecting physical damage of structures. A series of analysis and test results indicatge that proposed method has a confidence for applying a filed test. Therefore, it is expected to be able to take advantage of system identification to detect damage for the maintenance and management of steel structures under periodical impact loads such as power substation.

The State Attribute and Grade Influence Structure for the RC Bridge Deck Slabs by Information Entropy (정보 엔트로피에 의한 RC 교량 상판의 상태속성 및 등급 영향 구조 분석)

  • Hwang, Jin-Ha;Park, Jong-Hoi;An, Seoung-Su
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.23 no.1
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    • pp.61-71
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    • 2010
  • The attributes related to the health condition of RC deck slabs are analyzed to help us identify and rate the safety level of the bridges in this study. According to the related reports the state assessment for the outward aspects of bridges is the important and critical part for rating the overall structural safety. In this respect, the careful identification for the various state attributes make the field inspection and structural diagnosis very effective. This study analyzes the influence of the state attributes on evaluation classes and the relationship of them by the inductive reasoning, which raise the understanding and performance for evaluation work, and support the logical approach for the state assessment. ID3 algorithm applied to the case set which is constructed from the field reports indicates the main attributes and the precedence governing the assessment, and derives the decision hierarchy for the state assessment.

A Study of Measuring Vibration for Reproducing Waterhammer of Plant Equipment (플랜트 기자재 수충격 진동재현을 위한 진동측정에 관한 연구)

  • OH, Jung-Soo;Cho, Sueng-Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.11
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    • pp.145-150
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    • 2017
  • In this study, among the various types of plant equipment, valves, which are susceptible to water hammer, were selected as the diagnosis target. In order to effectively measure the vibration, an accelerometer was adapted for use in this difficult environment. The results showed that the maximum peak-to-peak vibration displacement caused by the action of water hammer on the valve was 21.40 mm, which would affect the structural stability of the valve and pipe. Meanwhile, the measured data was applied to the HIL simulator to verify the reproduction of the vibration. In the future, field data will be applied to the HIL simulator for the purpose of assessing the fatigue, durability and expected residual life of the plant equipment.

Development of a Machine Learning-Based Model for the Prediction of Chloride Diffusion Coefficient Using Concrete Bridge Data Exposed to Marine Environments (기계학습 기반 해양 노출 환경의 콘크리트 교량 데이터를 활용한 염화물 확산계수 예측모델 개발)

  • Woo-Suk Nam;Hong-Jae Yim
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.28 no.5
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    • pp.20-29
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    • 2024
  • The chloride diffusion coefficient is a critical indicator for assessing the durability of concrete marine substructures. This study develops a prediction model for the chloride diffusion coefficient using data from concrete bridges located in marine exposure zones (atmospheric, splash, tidal), an aspect that has not been considered in previous studies. Chloride profile data obtained from these bridge substructures were utilized. After data preprocessing, machine learning models, including Random Forest (RF), Gradient Boosting Machine (GBM), and K-Nearest Neighbors (KNN), were optimized through hyperparameter tuning. The performance of these models was developed and compared under three different variable sets. The first model uses six variables: water-to-binder (W/B) ratio, cement type, coarse aggregate volume ratio, service life, strength, and exposure environment. The second model excludes the exposure environment, using only the remaining five variables. The third model relies on just three variables: service life, strength, and exposure environment factors that can be obtained from precision safety diagnostics. The results indicate that including the exposure environment significantly enhances model performance for predicting the chloride diffusion coefficient in concrete bridges in marine environments. Additionally, the three variable model demonstrates that effective predictions can be made using only data from precision safety diagnostics.

A study about frequency domain analysis of impact-wave for detecting of structural defects in the concrete structure (구조물의 안전진단을 위한 충격파의 주파수 영역 탐사에 관한 연구)

  • Suh Baeksoo;;Kim Hyoungjun;Lee Sangchul
    • 한국지구물리탐사학회:학술대회논문집
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    • 2005.05a
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    • pp.165-180
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    • 2005
  • Impact seismic wave test is a method for nondestructive testing of concrete structure using of stress wave which is propagated and reflected from internal flaws within concrete structure and external surface, In this study, we performed non-destructive testing using impact seismic wave test for safety diagnosis of civil engineering structures. For this, I've compared and analized the result in the way of reflective method mostly using on one-dimension such as tunnel lining, and penetration method using the way of cross hole and tomography.

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The Examination of Load Carrying Capacity Based on Existing Data for Improved Safety Assessment Method of Expressway Bridges (고속도로 교량의 개선된 안전성 평가방안을 위한 실측자료에 기초한 공용 내하력 검토)

  • Lee, Jong Ho;Han, Sung Ho;Sin, Jae Chul
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.6A
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    • pp.597-605
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    • 2009
  • The safety of expressway bridges was estimated by checking the external condition rank based on the nondestructive inspection and material test and by measuring load carrying capacity based on the result of load test. Although the load carrying capacity of the bridges was clearly low compared to the design standard, it was examined that many of the bridges have good external condition rank relatively. Also, it can be assured that load carrying capacity shows a considerable difference according to various condition even though the bridges have similar construction year and a structural type. Therefore, this study showed various problems of the current safety measurement of expressway bridges by considering the status of the expressway bridges, external condition rank, and method of safety diagnosis and repair, rehabilitation for maintenance. Based on the existing data of over 400 expressway bridges, the load carrying capacity was analyzed quantitatively considering bridge type, serviced life, design live load, external condition rank and traffic count as variables. The result of this study will be expected to provide the basic information for a reasonable safety assessment of expressway bridge.

A Study on the Decision of Influence Range of External Temperature in the Tunnel Using Thermal Camera (열화상카메라를 활용한 외부온도의 터널내 영향범위 산정방법 연구)

  • Lee, Yu-Seok;Lee, Tea-Jong;Park, Gwang-Rim;Oh, Young-Seok;Cha, Cheol-Jun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.14 no.5
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    • pp.136-143
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    • 2010
  • There are three parts of tunnel which are influenced by outside temperature, entrance, exit and vent. These parts showed different tendency of deterioration(very rapid deterioration speed, wide range of defects, etc) compared with last parts of tunnel. Therefore, it needs to have different points of view when civil engineers analyze the defects on these parts and apply the retrofit or rehabilitation methods for them. However, when we conduct maintenance works, precise inspection and precise safety diagnosis, these defects had been neglected because those were considered as unimportant defects and caused from temporary weather and temperature change. In this study, two urban tunnels were analyzed to decide the range of tunnel which are influenced by outside temperature using a thermal camera, and to find out the causes of defects on these parts. From the results, the main points of maintenance were presented.

Development of a 3D Model-Based Demonstration DB System for Efficient Management and Utilization of Inspection and Diagnosis Data of Small and Medium-Sized Bridges (중소규모 교량의 점검·진단 데이터 효율적 관리 및 활용을 위한 3D 모델 기반 실증 DB시스템 개발)

  • Park, Se-Hyun;Jung, Dae-Sung;Seo, Jin-Sook;Kim, Tae-Hyeong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.6
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    • pp.1-11
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    • 2021
  • As the aging of large domestic SOC facilities accelerates, facility maintenance is also changing from safety evaluation based on the current condition to performance-oriented preventive and preemptive maintenance based on the prediction of the level of future obsolescence. In particular, in the case of bridges, class 1 and 2 bridges are systematically managed along with many studies, but for small and medium-sized class 3 bridges there is no collection and utilization of historical data presenting performance degradation during their service life. Therefore, in this study, 3D model-based demonstration DB system was designed and developed to intuitively check the damage change rate at the damage location by registering the maintenance history by life cycle for each member's exterior damage in the 3D bridge object and to enable API-based comprehensive performance evaluation.

Development of Low-Power IoT Sensor and Cloud-Based Data Fusion Displacement Estimation Method for Ambient Bridge Monitoring (상시 교량 모니터링을 위한 저전력 IoT 센서 및 클라우드 기반 데이터 융합 변위 측정 기법 개발)

  • Park, Jun-Young;Shin, Jun-Sik;Won, Jong-Bin;Park, Jong-Woong;Park, Min-Yong
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.34 no.5
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    • pp.301-308
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    • 2021
  • It is important to develop a digital SOC (Social Overhead Capital) maintenance system for preemptive maintenance in response to the rapid aging of social infrastructures. Abnormal signals induced from structures can be detected quickly and optimal decisions can be made promptly using IoT sensors deployed on the structures. In this study, a digital SOC monitoring system incorporating a multimetric IoT sensor was developed for long-term monitoring, for use in cloud-computing server for automated and powerful data analysis, and for establishing databases to perform : (1) multimetric sensing, (2) long-term operation, and (3) LTE-based direct communication. The developed sensor had three axes of acceleration, and five axes of strain sensing channels for multimetric sensing, and had an event-driven power management system that activated the sensors only when vibration exceeded a predetermined limit, or the timer was triggered. The power management system could reduce power consumption, and an additional solar panel charging could enable long-term operation. Data from the sensors were transmitted to the server in real-time via low-power LTE-CAT M1 communication, which does not require an additional gateway device. Furthermore, the cloud server was developed to receive multi-variable data from the sensor, and perform a displacement fusion algorithm to obtain reference-free structural displacement for ambient structural assessment. The proposed digital SOC system was experimentally validated on a steel railroad and concrete girder bridge.