• Title/Summary/Keyword: Mode Shapes

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Test Results on the Type of Beam-to-Column Connection using SHN490 Steel (SHN490강종의 보-기둥 접합부 형태에 따른 실험적 연구)

  • Kim, So Yeong;Byeon, Sang Min;Lee, Ho;Shin, Kyung Jae
    • Journal of Korean Society of Steel Construction
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    • v.27 no.3
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    • pp.311-321
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    • 2015
  • In this study, an experimental study to evaluate the seismic performance of beam-to-column connection for medium and low-rise building was conducted. Five connections using SHN490 steel were made with test variables such as flange welded or bolted, web welded or bolted. Specimen SHN-W-W is web welded and flange welded type. Specimen SHN-W-B is web welded and flange bolted type. Specimen SHN-B-W is web bolted and flange welded type. Specimen SHN-B-B is web bolted and flange bolted type. Specimen SHN-EP is a connection with the end plate to the beam ends. Cyclic loadings was applied at the tip of beam following KBC2009 load protocol. The load vs rotation curves for different connection are shown and final failure mode shapes are summarized. The connections are classified in terms of stiffness and strength as semi-rigid or rigid connection. Energy dissipation capacities for seismic performance evaluation were compared.

A numerical study on the 3-Dimensional shape characteristics of small underground cavities (소규모 지하공동 3차원 형상 특성을 반영한 수치해석에 관한 연구)

  • An, Joon-Sang;Kang, Kyung-Nam;Son, Ki-Il;Kim, Woo-Seok;Kim, Byung-Chan
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.5
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    • pp.787-807
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    • 2018
  • When conducting the underground safety impact assessment under the special law in Korea, it is essential to investigate the occurrence of underground cavities. When underground cavities were discovered, the underground safety was assessed through numerical analysis. The previous study has suggested the stability evaluation based on the factor of safety by changing the 2D shape of the small underground cavity. In this study, the effects of small underground cavities considering 3D shapes were examined using a continuum analysis program and compared with the 2D results presented in previous study. If the 3-Dimensional shape of the underground cavity is found close to the sphere type, it would be reasonable to evaluate the factor of safety by the shear strength reduction method regardless of the size and position of the cavity. If a high-aspect ratio underground cavity with a depth of 2 m or more from the ground surface and an aspect ratio (a/b) of 2.0 or more is in the vertical direction, not only the factor of safety but the failure mode shape should be cautions in the stability evaluation using the shear strength reduction method. The results of this study are expected to be basic data on underground safety impact assessment.

Palaeoenvironmental Implication of the Quaternary Gravel Sequences on the Basis of Gravel Shape (역의 형태에 의한 제4기 역층준의 고환경적 고찰)

  • Ju Yong Kim;Duck Keun Choi
    • The Korean Journal of Quaternary Research
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    • v.4 no.1
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    • pp.41-57
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    • 1990
  • Gravel shapes of the terrace gravel sequences are compared with the present river gravels and beach gravels in the Pohang and its surrounding areas. Seventeen gravel textural parameters are divided into 5 groups based on R-mode factor analysis. Among them, three parameters (RDm, MPSm, SZstd) are selected for a test of discriminant possibility of palaeoenvironment of the terrace gravel deposits. Marine gravels are in the range of 0.49 to 0.75 in mean roundness, 0.46 to 0.78 in mean maximum projection sphericity and 0.39 to 1.85 in standard deviation of size, whereas river gravels are 0.28 to 0.51 in mean roundness, 0.66 to 0.72 in mean maximum projection sphericity and 1.04 to 1.81 in standard deviation of size. For practical access to the palaeoenvironment discrimination, a bivariant diagram between mean roundness and mean maximum projection sphericity is the most effective. The marine terrace gravels are plotted within the variation range of present beach gravels and show 0.49 to 0.71 in mean roundness and 0.59 to 0.66 in mean maximum projection sphericity. The gravels of river terrace vary within the range of gravels derived from present river bed and are characterized as 0.36 to 0.48 in mean roundness and 0.66 to 0.71 in mean maximum projection sphericity.

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Variation of Seismic Behavior of Continuous Skew Plate Girder Bridges According to the Arrangement of Bearings (받침배치에 따른 연속 플레이트 거더 사교의 지진거동 변화)

  • Moon, Seong Kwon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.15 no.5
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    • pp.124-135
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    • 2011
  • The capacity of bearings installed at abutments and piers for continuous bridges is usually determined by the magnitude of the maximum vertical reaction at each support and the capacity of bearings placed at piers is higher than that at abutments. In this study, the possibility of the improved seismic performance of base-isolated continuous skew bridges was investigated by analysing the variation of the seismic behavior of them according to three arrangements of bearings. Based on the conventional arrangement of bearings(Case A), three arrangements of bearings such as Case A, Case B and Case C were selected considering the variation of the horizontal stiffness of the lead rubber bearing(LRB) installed at the pier. The seismic behavior of the total 36 skew bridges was investigated by conducting the response spectrum analysis using the hybrid response spectrum considered the effect of LRB's damping. Results of analyses show that a more desirable seismic behavior of base-isolated continuous skew bridges can be obtained by reducing the magnitude of the horizontal stiffness of LRB placed at the pier to similar to or less than that of LRB installed at abutments. The variation of LRB's stiffness at the pier brings about period elongation and the change of mode shapes of base-isolated skew bridges and results in the reduction of the total base shear, the maximum base shear at the pier and the girder stresses. Although positive effects on the seismic behavior of base-isolated skew bridges caused by the change of arrangement of bearings decreased slighty with an increase in the flexibility of the substructure, the proposed arrangements of bearings bring about the improved seismic performance of base-isolated continuous skew plate girder bridges with less than 10m height of piers.

Curing Behavior and Interfacial Properties of Electrodeposited Carbon Fiber/Epoxy Composites by Electrical Resistivity Measurement under Tensile/Compressive Tests (전기증착된 탄소섬유/에폭시 복합재료의 인장/압축 하중하에서의 전기저항 측정법을 이용한 경화 및 계면특성)

  • Park, Joung-Man;Lee, Sang-Il;Kim, Jin-Won
    • Journal of Adhesion and Interface
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    • v.2 no.1
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    • pp.9-17
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    • 2001
  • Curing behavior and interfacial properties were evaluated using electrical resistance measurement and tensile/compressive fragmentation test. Electrical resistivity difference (${\Delta}R$) during curing process was not observed in a bare carbon fiber. On the other hand, ${\Delta}R$ appeared due to the matrix contraction in single-carbon fiber/epoxy composite. Logarithmic electrical resistivity of the untreated single-carbon fiber composite increased suddenly to the infinity when the fiber fracture occurred under tensile loading, whereas that of the ED composite reached relatively broadly up to the infinity. Comparing to the untreated case, interfacial shear strength (IFSS) of the ED treated composite increased significantly in both tensile fragmentation and compressive Broutman test. Microfailure modes of the untreated and the ED treated fiber composite showed the debonding and the cone shapes in tensile test, respectively. For compressive test, fractures of diagonal slippage were observed in both untreated and the ED treated composite. Sharp-end shape fractures exhibited in the untreated composite, whereas relatively dull fractures showed in the ED Heated composite. It is proved that ED treatments affected differently on the interfacial adhesion and microfailure mechanism under tensile/compressive tests.

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Three Dimensional Vibration Analysis of Thick, Circular and Annular Plates with Nonlinear Thickness Variation (비선형 두께 변분을 갖는 두꺼운 원형판과 환형판의 3차원적 진동해석)

  • 장승환;심현주;강재훈
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.17 no.2
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    • pp.119-129
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    • 2004
  • A three dimensional (3D) method of analysis is presented for determining the free vibration frequencies and mode shapes of thick, circular and annular plates with nonlinear thickness variation along the radial direction. Unlike conventional plate theories, which are mathematically two dimensional (2D), the present method is based upon the 3D dynamic equations of elasticity. Displacement components u/sub s/, u/sub z/, and u/sub θ/ in the radial, thickness, and circumferential directions, respectively, are taken to be sinusoidal in time, periodic in θ, and algebraic polynomials in the s and z directions. Potential (strain) and kinetic energies of the plates are formulated, and the Ritz method is used to solve the eigenvalue problem thus yielding upper bound values of the frequencies by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four digit exactitude is demonstrated for the first five frequencies of the plates. Numerical results we presented for completely free, annular and circular plates with uniform linear, and quadratic variations in thickness. Comparisons are also made between results obtained from the present 3D and previously published thin plate (2D) data.

Measurement System of Dynamic Liquid Motion using a Laser Doppler Vibrometer and Galvanometer Scanner (액체거동의 비접촉 다점측정을 위한 레이저진동계와 갈바노미터스캐너 계측시스템)

  • Kim, Junhee;Shin, Yoon-Soo;Min, Kyung-Won
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.31 no.5
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    • pp.227-234
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    • 2018
  • Researches regarding measurement and control of the dynamic behavior of liquid such as sloshing have been actively on undertaken in various engineering fields. Liquid vibration is being measured in the study of tuned liquid dampers(TLDs), which attenuates wind motion of buildings even in building structures. To overcome the limitations of existing wave height measurement sensors, a method of measuring liquid vibration in a TLD using a laser Doppler vibrometer(LDV) and galvanometer scanner is proposed in this paper: the principle of measuring speed and displacement is discussed; a system of multi-point measurement with a single point of LDV according to the operating principles of the galvanometer scanner is established. 4-point liquid vibration on the TLD is measured, and the time domain data of each point is compared with the conventional video sensing data. It was confirmed that the waveform is transformed into the traveling wave and the standing wave. In addition, the data with measurement delay are cross-correlated to perform singular value decomposition. The natural frequencies and mode shapes are compared using theoretical and video sensing results.

A Study of the Failure Distribution and the Failure Difference by the Stress on the K-1 Tracked Vehicle (K-1전차의 고장분포와 부하에 따른 고장률 차이에 대한 연구)

  • Lee, Sang-Jin;Choi, Seok-Yoon
    • Journal of the military operations research society of Korea
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    • v.35 no.2
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    • pp.33-49
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    • 2009
  • The objective of this study is as follows. First, the hazard function on the failure probability density function of the K-1 tracked vehicles can be occurred in the form of the bathtub curve. Second, the failure mode may be different under two different operational situations. The research result shows that the bathtub curve can be fitted in the Weibull distribution, that assumes different shapes according to the specific stage of the system's life cycle. The K-1 tracked vehicle has a relatively high hazard(failure) rate at the time of its first service. The failure rate starts decreasing for a time immediately after it goes into service. After the break-in period, the surviving components have a fairly constant hazard rate. As the K-1 system ages, deterioration of its various parts takes place and the hazard rate starts Increasing. Second, the result shows the failure rate in the harsh operational environment is higher than that in the mild operational environment. In conclusion, the bathtub curve can be logically appropriate in establishing the depot overhaul cycle. Moreover, it is necessary for determining the right time of the depot overhaul to consider not only the age of defense equipment but also the different operational environment.

Mode of Occurrence and Chemical Composition of Electrums from the Gubong Gold-Silver Deposits, Republic of Korea (구봉 금-은광상에서 산출되는 에렉트럼의 산출상태와 화학조성)

  • 유봉철;최선규;이현구
    • Economic and Environmental Geology
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    • v.35 no.3
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    • pp.191-201
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    • 2002
  • The Gubong gold-silver deposits if gold-silver-bearing hydrothermal massive quartz veins which were filled the fractures along fault shear (NE, NW) zones within Precambrian banded or granitic gneiss of Gyeonggi massif. Ore mineralization of this deposits is contained within a single stage of quartz vein which was formed by multiple episodes of fracturing and healing. Ore minerals are comported mainly of arsenopyrite, pyrite, sphalerite, chalcopyrite, galena with minor amounts of pyrrhotite, marcasite and electrum. The frequency and volume percentages of electrum associated with ore minerals from this deposits are recognized as follows; 44.5% and 54.3% with arsenopyrite, 24.3% and 33.8% with quartz, 12.6% and 0.1% with pyrite, 11.0% and 4.8% with galena, 5.0% and 7.0% with sphalerite and 2.5% and 0.02% with chalcopyrite, respectively. They show irregular (41.6%), subround (34.7%), elongate (17.0%) and granular (6.6%) shapes, respectively. Their grain size ranges from 2 to 150 um, but 90.9 percent of the grains are below 30 um. The chemical composition of electrums ranges from 26.39 to 72.51 Au atomic %. These composition (Au atomic %) on the basis of associated minerals are from 44.97 to 71.75 with arsenopyrite, pyrite, sphalerite and quartz, from 44.37 to 72.51 with quartz, from 35.40 to 41.01 with sphalerite and chalcopyrite, from 26.39 to 54.84 with pyrite, chalcopyrite, quartz and galena, from 28.49 to 53.28 with galena, respectively. We suggest that optimum recovery of gold would be obtained with reference to these results.

Calculation of Expected Life of Hydrogen Pressure Vessels by Fracture and Fatigue Mechanics assuming Semi-elliptical Cracks and Analysis of the Effect of Thickness and Radius (반타원형 균열을 가정한 파괴 및 피로역학에 의한 수소 압력용기의 예상 수명 계산과 두께와 내경이 미치는 영향 분석)

  • Kim, Jeong Hwan;Lee, Hwa Young;Lee, Min-Kyung;Lee, Jae-Hun;Lyu, Geunjun
    • Journal of the Korean Institute of Gas
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    • v.25 no.6
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    • pp.53-65
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    • 2021
  • While the hydrogen refueling station is rapidly expanded and installed, the safety inspection of the hydrogen pressure vessel in the station should be very important. Of these, according to ASME, hydrogen embrittlement tests must be performed for hydrogen vessel that store hydrogen above a certain pressure. The main test method for hydrogen embrittlement inspection is to carry out fracture tests and fatigue fracture tests in a high pressure hydrogen atmosphere, which allows the durability limit of the pressure vessel to be measured and the endurable limit to be determined in the hydrogen atmosphere. In detail, the critical crack depth can be calculated by the stress intensity factor(K), and the service life can be determined by da/dN (fatigue growth rate). API579-1/ ASME FFS-1 part 9 exemplifies the calculation method according to the mode of crack-like flaws, but for various shapes such as plates and cylinders, there are about 55 modes according to the shape and location of the crack. Due to the fairly complex formula, it is not easily accessible. In this study, we will show you how to calculate fracture mechanics numerically via Excel and VBA. In addition, this was applied to analyze the effects of the thickness and inner diameter of the pressure vessel on the service life.