• Title, Summary, Keyword: 강성

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The Modified Coefficient of the Orthotropic Rigidity for Stiffened Plates with Open Ribs (개단면 리브를 갖는 보강판의 직교이방성 강성 수정 계수)

  • Chu, Seok Beom;Choi, Young
    • Journal of Korean Society of Steel Construction
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    • v.17 no.1
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    • pp.23-32
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    • 2005
  • In this paper, the modified coefficient of the orthotropic rigidity for stiffened plates with open ribs is proposed to improve the inaccurate results of the orthotropic plate analysis. For stiffened plates with rectangular and angle ribs having various aspect ratios and boundary conditions, the aspect ratio and the rigidity ratio are selected as parameters and the parametric study on the modified coefficient is performed. Analyzed results of stiffened plates modeling with the isotropic and orthotropic plate element show that the modified coefficient can be expressed as a function of the rigidity ratio for each rib space regardless of the aspect ratio in case of the aspect ratio under 1 and can be represented as a single union function without regard to rib spaces and aspect ratios in the other case. The results also shows that the effects of the boundary condition on the modified coefficient is small and coefficient functions have different values according to rib shapes. The application to examples shows that the modified coefficient of the orthotropic rigidity improves accuracy. Therefore, the orthotropic plate analysis of stiffened plates with open ribs can easily achieve more accurate results using the coefficient function proposed in this study

A Experimental Study on the Stiffness Characteristics of Elastomeric Bearings (탄성받침의 강성특성에 대한 실험연구)

  • Yoon, Hyejin;Cho, Changbeck;Kim, Youngjin;Kwahk, Imjong
    • Journal of The Korean Society of Civil Engineers
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    • v.28 no.4A
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    • pp.475-485
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    • 2008
  • This paper intends to enhance the reliability and performance of domestic elastomeric bearings through the proposal of directions for the improvement of their stiffness regard to the Korean industrial standard KS F 4420 relative to the evaluation of design/fabrication/quality. Therefore, comparative analysis of the compressive elastic modulus, stiffness measurement method and performance evaluation method of KS F 4420 with those of Eurocode, Japanese bearing manual, and ISO code was performed, and measurement tests on the compressive stiffness and shear stiffness of common elastomeric bearings produced in Korea were conducted. The experimental results reveal that differences of about 20% and 13% occurred respectively for the compressive stiffness and shear stiffness according to the definition adopted for the stiffness. The measured values for the stiffness of the domestic elastomeric bearings were also verified to exhibit large deviation from the formula proposed by KS F 4420. Elastomeric bearings that does not have appropriate compressive stiffness required at the design can result in uneven deflection at supports of bridges and excessive stress in girders. Accordingly, the establishment of compressive elastic modulus formula and performance evaluation criteria fitted to the domestic circumstances through the execution of performance evaluation of bearings presenting diversified shapes and shape factors appears to be necessary for the domestic bearings to meet the performance required in design.

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Determination of the Strength and Stiffness Degradation Factor for Circular R/C Bridge Piers (원형 철근콘크리트 교각의 강성 및 강도감소지수 결정)

  • 이대형;정영수
    • Journal of the Earthquake Engineering Society of Korea
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    • v.4 no.2
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    • pp.73-82
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    • 2000
  • 본연구의 목적은 반복하중을 받는 철근콘크리트 교량 교각의 비선형 이력거동을 해석적으로 예측하는 것이다 이를 위해서 반복적인 횡하중이 작용하는 경우에 실험결과와 일치하는 교각의 하중-변위 이력곡선을 도출하고자 수정된 trilinar 이력거동모델을 이용하였다 철근과 콘크리트의 비선형 거동특성과 각 하중단계에 따른 교각의 중립축을 구하여 소성힌지부의 모멘트와 변형률을 구하고 반복하중하에서의 강성의 변화를 해석적으로 모형화하기 위하여 각기 다른 강성을 갖는 5가지 지선을 갖춘 형태의 이력거동모델식을 제안하였다 본 연구에서는 실험적으로 구한 하중-변위 이력곡선을 이용하여 축하중비 주철근비 및 구속철근비에 따른 강도감소지수와 강성감소지수의 영향을 회귀분석을 이용하여 일반식으로 제안하였다 새로운 이력거동 해석 모델을 프로그램 SARCF III에 적용함으로써 기존 철근콘크리트 교각에 강도 및 강성감소 현상을 정확하게 예측하였다

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Deformation and Stress Distribution on Multi-Layered Foundation with Different Rigidity (강성(剛性)이 다른 다층토(多層土) 지반(地盤)의 변형(變形) 및 응력전달(應力傳達))

  • Park, Byong Kee;Chang, Yong Chai;Park, Jong Cheon;Park, Seon Bae
    • Journal of The Korean Society of Civil Engineers
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    • v.12 no.2
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    • pp.205-215
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    • 1992
  • Load tests for fourteen small-scale foundation models combined with geotextile, sand mat and rigid mat were conducted to study the effect of geotextile(G/T), sand mat(S/M), and foundation types on deformation of foundation soils. In addition, the experimental results were compared with those obtained from numerical analysis using a software program. The main conclusions were summarized as follows: 1. The restraint effect on G/T is more outstanding on the lateral displacement than on the vertical one. 2. The single use of S/M has better effect on the restraint of vertical displacement than lateral one. 3. The use of both S/M and G/T is required for the restraint of lateral and vertical displacement. 4. Multi-layered foundation with large rigidity shows similar tendency to that of foundation reinforced with S/M and G/T.

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Seismic Analysis of Mid Rise Steel Moment Resisting Frames with Relative Stiffness of Connections and Beams (접합부와 보의 상대강성을 고려한 중층 철골 모멘트 골조의 내진해석)

  • Ha, Sung-Hwan;Kang, Cheol-Kyu;Han, Hong-Soo;Han, Kweon-Gyu;Choi, Byong-Jeong
    • Journal of Korean Society of Steel Construction
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    • v.23 no.5
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    • pp.595-606
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    • 2011
  • This study was conducted to investigate the seismic behavior of steel member resisting frames considering the relative stiffness of the connection and beams. Six-story steel moment frames were designed to study the seismic behavior. The connections were classified into Double Web-Angle connections (DWAs), Top- and Seat-angles with double Web-angles (TWSs), FEMA-Test Summary No. 28, Specimen ID: UCSD-6 (SAC), and Fully Restrained (FR). The rotational stiffness of the semi-rigid connections was estimated using the Three-Parameter Power Model adopted by Chen and Kishi. The relative stiffness, which is the ratio of the rotational stiffness of the connections to the stiffness of the beams, was used. Push-over, repeated loading, and time history analysis were performed for all the frames. The seismic behavior of each frame was analyzed with the story drift, plastic hinge rotation, and hysteretic energy distribution.

An Experimental Study to Evaluate the Stiffness of Fastening Systems - Translational Stiffness along the Vertical Axis of Rail, Rotational Stiffness along the Strong Axis of Rail - (체결장치의 강성 평가를 위한 실험적 연구 - 레일 연직방향 병진강성, 레일 강축에 대한 회전강성 -)

  • Kim, Jung-Hun;Han, Sang-Yun;Lim, Nam-Hyoung;Kang, Young-Jong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.4
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    • pp.71-78
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    • 2008
  • In the case of the railway bridges, uplift forces were occurred at the edge of the segments when vehicular loads were applied. These forces caused the compressive and tensile forces in the fastening system. In the past, a structural analysis has been performed to investigate the safety of fastening system which was modeled with one directional spring elements based on the compressive test of fastening system. In this case, the stiffness of the spring element was obtained from experimental study which was conducted by compressive load. Therefore, to perform rational and exact structural analysis, the translational stiffness of the fastening system obtained from the experimental study applied the tensile load and the rotational stiffness should be considered because it was occurred the tensile force as well as the compressive force in fastening system. In this study, an elastic and inelastic experimental study was performed for six specimens. The translational stiffness along the vertical axis of rail and the rotational stiffness along the strong axis of rail were investigated, also structural behavior of the fastening system was analyzed.

Stiffness Degradation during Deep Excavation in Urban Area (도심지 깊은 굴착에 따른 지반 강성의 변화)

  • Choi, Jongho;Koo, Bonwhee;Kim, Taesik
    • Journal of the Korean GEO-environmental Society
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    • v.16 no.2
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    • pp.27-31
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    • 2015
  • In urban area, many design projects related to geotechnical projects are controlled by serviceability rather than stability requirements. Accordingly, control of ground deformation has become more crucial and many researchers have studied soil stiffness. Recent experimental studies on the stress-strain response of Chicago glacial clays showed that the nonlinearity and anisotropy are the two key factors in evaluating the soil stiffness. In this study, experimental results are applied to analyze the deep excavation site locating in downtown Chicago. The stress paths observed from the observation points located behind and front of the supporting wall yield typical stress paths. Changes in soil stiffness nonlinearity and anisotropy were discussed by comparing experimental and computed stress paths. The stiffness anisotropy were significant even at the first few excavations. The stiffness degradation characteristics are significantly different according to relative location to the support wall even at the same elevation.

Prediction of the Ratios of Increase in Lateral Stiffness for Preliminary Structural Design of Tall Buildings (초고층건물의 초기 구조설계를 위한 횡강성 증가율 예측)

  • Jung, Jong-Hyun
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.20 no.4
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    • pp.453-462
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    • 2007
  • The purpose of this study is to predict the ratios of increase in lateral stiffness for preliminary structural design of tall buildings. For this, the basic models of tall buildings with 60 stories are generated. The basic models have typical floor plan of Box or T type. And the factors for increase in lateral stiffness are selected as follows; the addition of outriggers, increase in material strength, and increase in member size of core walls, outrigger columns, and outrigger walls. Then these factors are applied to the basic models and their effects are investigated using the results of structural analysis. Finally, based on the investigation, the ratios of increase in lateral stiffness for preliminary structural design of tall buildings are proposed and applied to examples of tall building for verification of the ratios.

Experimental and Numerical Study on the Structural Stiffness of Composite Rotor Blade (복합재 로터 블레이드의 구조 강성도에 대한 실험적/수치적 연구)

  • Jeon, Hyeon-Kyu;Jeon, Min-Hyeok;Kang, Min-Song;Kim, In-Gul;Park, Jae-Sang;Seok, Jin-Young
    • Composites Research
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    • v.32 no.4
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    • pp.191-198
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    • 2019
  • The basic mechanical properties of helicopter rotor blade are important parameters for the analysis of helicopter performance. However, it is difficult to estimate these properties because the most of rotor blades consist of various materials such as composite materials and metals, etc. In this paper, the bending/torsional stiffness for composite rotor blade of unmanned helicopter were evaluated through experimental and analytical studies. In finite element analysis, the bending/torsional stiffness were evaluated through the relationship of load-displacement and element stiffness matrix. The evaluated stiffness from the measured strains and displacements in bending and torsional test agreed well with the derived results of FEA.

Proposed Deterioration-induced Axial Stiffness of Existing Piles in Vertical Extension Structures (수직증축 공동주택 하부 기존말뚝의 열화를 고려한 축강성 제안)

  • Jeong, Sang-Seom;Kim, Do-Hyun;Cho, Hyun-Chul
    • Journal of the Korean Geotechnical Society
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    • v.35 no.12
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    • pp.25-33
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    • 2019
  • In this study, the axial stiffness of existing piles (Kve) of vertical extension remodeled building was quantified through theoretical and experimental approaches. Theoretically induced upper and lower boundary of the pile axial stiffness was estimated by using the formula proposed by Randolph and Wroth (1978), which can estimate the axial stiffness of rigid and flexible pile subjected under soil confinement. In addition, 38 cases of field measurement data on deteriorated piles with various diameters constructed in the period between 1995 - 1997 were taken in to account by overlapping the field data with the theoretical boundary of the axial stiffness. Through this the maximum axial stiffness of existing pile due to deterioration and long service time was presented for various slenderness ratio (L/D), which can be used in estimating the necessary axial stiffness of reinforcing piles(Kvr) for the vertical extension remodeling. The lower 95% value of the estimated axial stiffness of existing pile will be induced through statistical processing.