Processing math: 100%
  • Title/Summary/Keyword: structural damage assessment

Search Result 532, Processing Time 0.027 seconds

Assessment of Fire-Damaged Mortar using Color image Analysis (색도 이미지 분석을 이용한 화재 피해 모르타르의 손상 평가)

  • Park, Kwang-Min;Lee, Byung-Do;Yoo, Sung-Hun;Ham, Nam-Hyuk;Roh, Young-Sook
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.23 no.3
    • /
    • pp.83-91
    • /
    • 2019
  • The purpose of this study is to assess a fire-damaged concrete structure using a digital camera and image processing software. To simulate it, mortar and paste samples of W/C=0.5(general strength) and 0.3(high strength) were put into an electric furnace and simulated from 100C to 1000C. Here, the paste was processed into a powder to measure CIELAB chromaticity, and the samples were taken with a digital camera. The RGB chromaticity was measured by color intensity analyzer software. As a result, the residual compressive strength of W/C=0.5 and 0.3 was 87.2 % and 86.7 % at the heating temperature of 400C. However there was a sudden decrease in strength at the temperature above 500C, while the residual compressive strength of W/C=0.5 and 0.3 was 55.2 % and 51.9 % of residual strength. At the temperature 700C or higher, W/C=0.5 and W/C=0.3 show 26.3% and 27.8% of residual strength, so that the durability of the structure could not be secured. The results of Lab color analysis show that b increases rapidly after 700C. It is analyzed that the intensity of yellow becomes strong after 700C. Further, the RGB analysis found that the histogram kurtosis and frequency of Red and Green increases after 700C. It is analyzed that number of Red and Green pixels are increased. Therefore, it is deemed possible to estimate the degree of damage by checking the change in yellow(b or R+G) when analyzing the chromaticity of the fire-damaged concrete structures.

A Study of Evaluating Streetscape Green Environments to Improve Urban Street Green Spaces - A Case Study of Jeonju City - (도시가로녹지의 개선을 위한 녹화환경평가 연구 -전주시를 대상으로-)

  • Jeong, Moon-Sun;Lim, Hyun-Jeong
    • Journal of the Korean Society of Environmental Restoration Technology
    • /
    • v.22 no.3
    • /
    • pp.55-71
    • /
    • 2019
  • The purpose of this study is to propose an evaluation method to assess green environments of streetscapes to improve urban street green spaces in Jeonju City. Through a rapid assessment of urban street green spaces, we suggest an objective basis for expanding street green space as well as for adopting sustainable maintenance and improvement measures. We choose 12 sections of streetscapes (roads and sidewalks) to investigate existing street conditions which have more than four lanes and function as major road axes. Six large roads and six medium roads of Jeonju City center area are investigated as pilot assessment study sites. Site inventory checklists consist of environmental characteristics of streetscape, street tree status, and planting condition evaluation. Environmental characteristics of streetscapes are composed of physical and neighborhood factors. For instance, items for physical factors are types and width of road/sidewalks, paving materials, tree protection materials, and green strip. And surrounding landuse is a neighborhood factor. Assessment items for street tree status are street plant names (tree/shrubs/ground cover), size, and planting intervals. Planting condition evaluation items are tree shape, damage, canopy density, and planting types with existence of adjacent green space. Evaluation results are classified into three levels such as A(maintain or repair), B(greening enhancement), and C(structural improvement). In case of grade A, streetscapes have enough sidewalk width for maintaining green strip and a multi-layered planting(in large road only) with fairly good growing conditions of street trees. For grade B and C, streetscapes have a moderate level of sidewalk width with a single street tree planting. In addition, street tree growing conditions are appeared poor so that green enhancement or maintenance measures are needed. For median, only grade B and C are found as its planting growing foundations are very limited in space. As a result, acquiring enough sidewalk space is essential to enhance ecological quality of urban street green. Especially, it is necessary to have green strip with reasonable widths for plant growing conditions in sidewalks. In addition, we need to consider native species with multi-layer plant compositions while designing street green.

KSR-III 1단부 도로운송에 의한 진동하중

  • Chun, Young-Doo;Cho, Byoung-Gyu;Park, Dong-Soo;Hwang, Seung-Hyun;Park, Jeong-Joo
    • Aerospace Engineering and Technology
    • /
    • v.2 no.2
    • /
    • pp.105-114
    • /
    • 2003
  • It is conducted to analyze vibration loads on the 1st stage of KSR-III(KSR : Korea Sounding Rocket) during their ground transportation and various handling process. These loads may be different from the real flight environment. Inadequate assessment of these loads can cause not only local damages on the rocket system but also the critical problem like flight mission failure. Therefore, transportation and handling loads must be considered during design and attenuated to ensure that the rocket structural damage does not occur. This work is concerned with the generation of criteria and prediction of transportation and handling loads for KSR-III. The results show that the shipping container is well designed to satisfy the design requirements. The maximum vibration level recorded during whole transportation and handling for KSR-III is less than 2g, the criteria of KSR-III movement condition.

  • PDF

Fragility reduction using passive response modification in a Consequence-Based Engineering (CBE) framework

  • Duenas-Osorio, Leonardo;Park, Joonam;Towashiraporn, Peeranan;Goodno, Barry J.;Frost, David;Craig, James I.;Bostrom, Ann
    • Structural Engineering and Mechanics
    • /
    • v.17 no.3_4
    • /
    • pp.527-537
    • /
    • 2004
  • Consequence-Based Engineering (CBE) is a new paradigm proposed by the Mid-America Earthquake Center (MAE) to guide evaluation and rehabilitation of building structures and networks in areas of low probability - high consequence earthquakes such as the central region of the U.S. The principal objective of CBE is to minimize consequences by prescribing appropriate intervention procedures for a broad range of structures and systems, in consultation with key decision makers. One possible intervention option for rehabilitating unreinforced masonry (URM) buildings, widely used for essential facilities in Mid-America, is passive energy dissipation (PED). After the CBE process is described, its application in the rehabilitation of vulnerable URM building construction in Mid-America is illustrated through the use of PED devices attached to flexible timber floor diaphragms. It is shown that PED's can be applied to URM buildings in situations where floor diaphragm flexibility can be controlled to reduce both out-of-plane and in-plane wall responses and damage. Reductions as high as 48% in roof displacement and acceleration can be achieved as demonstrated in studies reported below.

Spatial Variability of Soil Moisture and Irrigation Scheduling for Upland Farming (노지 작물의 적정 관개계획을 위한 토양수분의 공간변이성 분석)

  • Choi, Yonghun;Kim, Minyoung;Kim, Youngjin;Jeon, Jonggil;Seo, Myungchul
    • Journal of The Korean Society of Agricultural Engineers
    • /
    • v.58 no.5
    • /
    • pp.81-90
    • /
    • 2016
  • Due to droughts and water shortages causing severe damage to crops and other vegetations, much attention has been given to efficient irrigation for upland farming. However, little information has been known to measure soil moisture levels in a field scale and apply their spatial variability for proper irrigation scheduling. This study aimed to characterize the spatial variability and temporal stability of soil water contents at depths of 10 cm, 20 cm and 30 cm on flat (loamy soil) and hill-slope fields (silt-loamy soil). Field monitoring of soil moisture contents was used for variogram analysis using GS+ software. Kriging produced from the structural parameters of variogram was applied for the means of spatial prediction. The overall results showed that the surface soil moisture presented a strong spatial dependence at the sampling time and space in the field scale. The coefficient variation (CV) of soil moisture was within 7.0~31.3 % in a flat field and 8.3~39.4 % in a hill-slope field, which was noticeable in the dry season rather than the rainy season. The drought assessment analysis showed that only one day (Dec. 21st) was determined as dry (20.4 % and 24.5 % for flat and hill-slope fields, respectively). In contrary to a hill-slope field where the full irrigation was necessary, the centralized irrigation scheme was appeared to be more effective for a flat field based on the spatial variability of soil moisture contents. The findings of this study clearly showed that the geostatistical analysis of soil moisture contents greatly contributes to proper irrigation scheduling for water-efficient irrigation with maximal crop productivity and environmental benefits.

A Study on MPDB Compatibility Assessment of Car to Car Offset Frontal Impact Test (차 대 차 부분 정면충돌 시험의 MPDB compatibility 평가에 대한 연구)

  • Sun, Hongyul;Yoon, Ilsung;Kim, Jeasu;Lee, Mansu
    • Journal of Auto-vehicle Safety Association
    • /
    • v.11 no.4
    • /
    • pp.6-15
    • /
    • 2019
  • Since introducing the offset frontal impact test in EuroNCAP in 1997, the vehicle has been constantly changing according to its usage and purpose. As of 2019, many vehicles have been released to the public, which has led to a large structural mass difference between small, medium and large vehicles. Also, the geometry of the front of the vehicle is completely different for each vehicle and tends not to be perfectly aligned at frontal collisions. The difference in mass of each of these vehicles and less performing structures for offset crashes have led to dramatically worse outcome in a car to car offset frontal impact tests. Even though a decade later passenger cars have become much safer due to consumer test programs and regulatory requirements, the aggressiveness and compatibility that can cause damage to the opponent car in the event of car to car collision is not considered in the above-mentioned section, and therefore much improvement is needed. After many years of study to solve this problem, EuroNCAP has developed a new mode MPDB offset front test that considers the aggressiveness and compatibility that can affect the opponent cars that have collided. This paper introduces the development process of aggressiveness and compatibility evaluation method of MPDB in EuroNCAP which will be implemented from 2020. Several impact tests have been conducted at different test conditions to rate the vehicle structure performance only focused on aggressiveness and compatibility of MPDB.

Estimating High-Frequency Damping of a Beam through Electro-Mechanical Signatures of Piezoelectric Wafer Mounted on the Beam (보에 부착된 압전웨이퍼의 전기역학적 신호를 통한 고주파수 대역 감쇠 추정)

  • Shin, Yong Jae;Park, Hyun Woo
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.37 no.1
    • /
    • pp.217-229
    • /
    • 2017
  • The high-frequency electro-mechanical signatures, which are excited and received by piezoelectric wafers mounted on a beam, are sensitive to incipient defect in a beam. Predicting the sensing range of the piezoelectric wafers is needed to effectively conduct damage assessment of a beam through utilizing their advantage. Damping of a beam plays the most important role in determining the sensing range among other features. This paper has proposed a scheme for estimating high-frequency damping of a beam through electro-mechanical signatures of piezoelectric wafers mounted on the beam. Considering damping effect while resonance of a beam evolves, wave perspective is adopted to formulate the electro-mechanical signatures of piezoelectric wafers. The damping of a beam is estimated through the least squares method minimizing the difference between the calculated and the measured damping ratio function values which are obtained from formulated and measured electro-mechanical signatures, respectively. The validity of the proposed scheme has been demonstrated through numerical and experimental examples using an aluminum beam with collocated piezoelectric wafers.

Fragility Analysis for Evaluation and Comparison of Seismic Performance of Building Structures (취약도 해석을 통한 빌딩구조물의 내진성능 비교 및 평가)

  • Park, Joo-Nam;Choi, Eun-Soo
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.11 no.3 s.55
    • /
    • pp.11-21
    • /
    • 2007
  • Potential damage and losses associated with structural systems caused by earthquake can be reduced by application of seismic design to the structures. Because the building cost required for seismic design is generally higher than the cost for non-seismic design, the application of seismic design must be justified considering both seismic performance and cost. This paper presents a risk-based fiamework for evaluation and comparison of seismic performance of structures such that necessary data can be supplied for decision making on seismic design. Seismic fragility curve is utilized for seismic risk assessment of structures, and the process for decision analysis on adaptation of seismic design is presented based on the equivalent cost model.

Earthquake risk assessment of concrete gravity dam by cumulative absolute velocity and response surface methodology

  • Cao, Anh-Tuan;Nahar, Tahmina Tasnim;Kim, Dookie;Choi, Byounghan
    • Earthquakes and Structures
    • /
    • v.17 no.5
    • /
    • pp.511-519
    • /
    • 2019
  • The concrete gravity dam is one of the most important parts of the nation's infrastructure. Besides the benefits, the dam also has some potentially catastrophic disasters related to the life of citizens directly. During the lifetime of service, some degradations in a dam may occur as consequences of operating conditions, environmental aspects and deterioration in materials from natural causes, especially from dynamic loads. Cumulative Absolute Velocity (CAV) plays a key role to assess the operational condition of a structure under seismic hazard. In previous researches, CAV is normally used in Nuclear Power Plant (NPP) fields, but there are no particular criteria or studies that have been made on dam structure. This paper presents a method to calculate the limitation of CAV for the Bohyeonsan Dam in Korea, where the critical Peak Ground Acceleration (PGA) is estimated from twelve sets of selected earthquakes based on High Confidence of Low Probability of Failure (HCLPF). HCLPF point denotes 5% damage probability with 95% confidence level in the fragility curve, and the corresponding PGA expresses the crucial acceleration of this dam. For determining the status of the dam, a 2D finite element model is simulated by ABAQUS. At first, the dam's parameters are optimized by the Minitab tool using the method of Central Composite Design (CCD) for increasing model reliability. Then the Response Surface Methodology (RSM) is used for updating the model and the optimization is implemented from the selected model parameters. Finally, the recorded response of the concrete gravity dam is compared against the results obtained from solving the numerical model for identifying the physical condition of the structure.

Safety Effect Evaluation of Existing Metro Tunnel by Deep Urban Tunnelling (대심도 도심지 터널시공에 의한 기존 지하철 터널 안전영향 평가)

  • Han, Sang-Min;Lee, Dong-Hyuk;Lee, Sung-Ho
    • Journal of the Korean Geotechnical Society
    • /
    • v.37 no.9
    • /
    • pp.37-50
    • /
    • 2021
  • Recently, due to the expansion of urban infrastructure using underground spaces in urban areas, many adjacent constructions and excavations have been made carried out between existing facilities, and complaints related to the stability of existing facilities due to close construction have become significant issues. In this study, it was closely reviewed for the existing metro tunnel structure in the new Dongbuk urban metro railway to determine the behavioral characteristics of tunnel structure according to adjacent tunnel construction. Also, it was analysed the evaluation of the safety zone and excavation method for metro tunnel structure. And after a detailed damage assessment, track irregularities and structural calculation by using a numerical analysis, stability of the metro tunnel structure according to nearby tunnel excavation was evaluated to be secured for safety. This study is expected to be applied as practical reference to review the evaluation of safety effects of existing tunnel structure and buildings according to adjacent construction in complex deep urban tunnelling.