• 제목/요약/키워드: Local stiffness

검색결과 410건 처리시간 0.023초

지진과 세굴의 복합적인 영향을 받는 연속교의 동적거동분석 (Dynamic Analysis of Multi-Span Continuous Bridges under Combined Effects of Earthquake and Local Scour)

  • 김상효;마호성;이상우;심정욱
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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    • pp.166-173
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    • 2002
  • Seismic bridge failure due to the combined effects of earthquake and local scour are examined in probabilistic perspectives. The seismic responses of multi-span continuous bridge with deep foundations are evaluated with a simplified mechanical model. The probabilistic local scour depths around the deep foundations are estimated by using the Monte Carlo simulation. From the simulation results, it is found that seismic responses of a bridge slightly increase due to the local scour effect. The effect of local scour on the global motion of the continuous bridge is found to be significant under weak seismic intensity. In addition, the duration to regain its original foundation stiffness is critical in estimating the probability of foundation failure under earthquake. Therefore, the duration in recovering the foundation stiffness should be determined reasonably and the safely of the whole bridge system should be evaluated by considering the scour effect.

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차체의 유연성을 고려한 차량 승차감 해석 (Analysis of Ride Comfort for an Automobile with flexible Vehicle Body)

  • 김정훈;최광성;박성용;이장무;강상욱;강주석
    • 한국자동차공학회논문집
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    • 제13권4호
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    • pp.121-128
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    • 2005
  • In most researches on the ride comfort analysis of passenger vehicles, the flexibility of the vehicle body has been not considered as an important factor, because the resonance frequencies of the vehicle body related to pitching, yawing and rolling motions are below 10Hz while the resonance frequencies of the vehicle body related to the flexibility are above 20Hz approximately. Nevertheless, the paper shows that the consideration of the local flexibility (or local stiffness) of the 4 corners on which shock absorbers are mounted influences the ride comfort. A simple beam model is devised to qualitatively examine the effect of the change of the local stiffness of the vehicle body on the ride comfort. Based on the results obtained from the analysis of the one-dimensional model, multi-body dynamic analysis considering the flexibility of the vehicle body is performed using ADAMS and MSC/NASTRAN. Natural frequencies and mode shapes computed by MSC/NASTRAN are used as input data for multi-body dynamic analysis in ADAMS. Through simulations using ADAMS, it has been found that the ride comfort can be improved by changing the local stiffness of the vehicle body and that the simulation results agree with experiment results.

ON THE TREATMENT OF DUCTILE FRACTURE BY THE LOCAL APPROACH CONCEPT IN CONTINUUM DAMAGE MECHANICS : THEORY AND EXAMPLE

  • Kim, Seoung-Jo;Kim, Jin-Hee;Kim, Wie-Dae
    • Journal of Theoretical and Applied Mechanics
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    • 제2권1호
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    • pp.31-50
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    • 1996
  • In this paper, a finite element analysis based on the local approach concept to fracture in the continuum damage mechanics is performed to analyze ductile fracture in two dimensional quasi-static state. First an isotropic damage model based on the generalized concept of effective stress is proposed for structural materials in the context of large deformation. In this model, the stiffness degradation is taken as a measure of damage and so, the fracture phenomenon can be explained as the critical deterioration of stiffness at a material point. The modified Riks' continuation technique is used to solve incremental iterative equations. Crack propagation is achieved by removing critically damaged elements. The mesh size sensitivity analysis and the simulation of the well known shearing mode failure in plane strain state are carried out to verify the present formulation. As numerical examples, an edge cracked plate and the specimen with a circular hole under plane stress are taken. Load-displacement curves and successively fractured shapes are shown. From the results, it can be concluded that the proposed model based on the local approach concept in the continuum damage mechanics may be stated as a reasonable tool to explain ductile fracture initiation and crack propagation.

캐비닛내부응답스펙트럼을 위한 전기캐비닛 전도강성 (Rocking Stiffness of Electrical Cabinet for In-Cabinet Response Spectrum)

  • 정연하;홍기증;조성국
    • 한국지진공학회논문집
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    • 제24권2호
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    • pp.95-102
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    • 2020
  • Electrical instruments and devices contained in cabinets for controlling nuclear power plants require seismic qualification; likewise, in-cabinet response spectrum (ICRS) is necessary. Gupta et al. (1999) suggested the Ritz method, where rocking, frame bending, and plate bending behaviors of cabinets are considered, as a method for determining ICRS. This research proposes a method to determine the rocking stiffness of cabinets, which represents its rocking behavior. The cabinet is fixed on mounting frames and is connected to the base concrete by anchors. When horizontal excitation is applied to the cabinet, the mounting frames at anchors are locally deformed, the mounting frames are bent, and then rocking in the cabinet becomes evident. A method to determine equivalent vertical spring stiffness representing the local deformation of the mounting frames at anchors is then proposed. Subsequently, the rocking stiffness of this mounting frame is calculated upon assumption of the mounting frame as an indeterminate beam.

Experimental investigation of local damage in high strength concrete columns using a shaking table

  • Bairrao, Rogerio;Kacianauskas, Rimantas;Kliukas, Romualdas
    • Structural Engineering and Mechanics
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    • 제19권5호
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    • pp.581-602
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    • 2005
  • In this paper the accumulation of local damage during the cyclic loading in reinforced high-strength concrete columns is experimentally investigated. Two identical column specimens with annular cross-section and spiral reinforcement were designed and two tests, up to failure, under the action of a constant vertical concentrated force and a time-dependent concentrated horizontal force, were carried out at the LNEC shaking tables facility. Sine type signals, controlled in amplitude, frequency and time duration were used for these experiments. The concept of local damage based on local stiffness degradation is considered in detail and illustrated by experimental results. The specimens were designed and reinforced in such a way that the accumulation of damage was predicted by dominating deformations (cracking and crushing of the concrete) while the increasing of the loading values was a dominating factor of damage. It was observed that the local damage of HSC columns has exposed their anisotropic local behaviour. The damage accumulation was slightly different from the expected in accordance with the continuum damage concept, and a partial random character was observed.

폐단면리브로 보강된 일축압축을 받는 복합적층판의 국부좌굴강도 증가효과 (Increasing Effect in Local Buckling Strength of Laminated Composite Plates Stiffened with Closed-section Ribs under Uniaxial Compression)

  • 황수희;김유식;최병호
    • 복합신소재구조학회 논문집
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    • 제4권2호
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    • pp.39-44
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    • 2013
  • This study is aimed to examine the influence of the rotational stiffness of U-shaped ribs on the local buckling behaviors of laminated composite plates. Applying the orthotropic plates with eight layers of the layup $[(0^{\circ})4]s$ and $[(0^{\circ}/90^{\circ})2]s$, 3-dimensional finite element models for the U-rib stiffened plates were setup by using ABAQUS and then a series of eigenvalue analyses were conducted. There is a need to develope a simple design equation to establish the rotational stiffness effect, which could be easily quantified by comparing the theoretical critical stress equation for laminated composite plates with elastic restraints based on the Classical laminated plate theory. Through the parametric numerical studies, it is confirmed that there should clearly exist an increasing effect of local plate buckling strength due to the rotational stiffness by closed-section ribs. An applicable coefficient for practical design should be verified and proposed for future study. This study will contribute to the future study for establishing an increasing coefficient for the design strength and optimum design of U-rib stiffened plates.

동적 및 정적 실험 방법으로 평가한 지반의 초기 강성 비교 (Comparison of dynamic and static methods in the measurement of the initial stiffness of soil)

  • 주진현;정영훈;정충기
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2009년도 춘계 학술발표회
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    • pp.940-951
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    • 2009
  • A comparative study on dynamic and static measurement of initial stiffness was conducted. Because soil stiffness decreases even at very small strains, the initial stiffness has been measured by dynamic tests using shear wave velocity measurement. On the other hand, due to the advance of local strain measurement, the triaxial testing device is capable of measuring the static initial stiffness. It has been known that initial stiffness measured by static triaxial tests is generally lower than that measured by dynamic tests possibly due to the limitation of static measurement of displacement at very small strains. This study presents experimental results indicating that the elastic shear moduli could be the same both in dynamic and static measurements owing to the soil anisotropy induced by anisotropic stresses.

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위치별 진동 측정을 통한 차체강성평가 (Evaluation of Vehicle Body Stiffness by Measuring Local Vibration)

  • 이경태;전용두;최두석
    • 한국자동차공학회논문집
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    • 제21권6호
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    • pp.195-200
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    • 2013
  • Road loads data are indispensable in the evaluation of BSR (Buzz, Squeak, and Rattle) of automotive parts/modules. However, there are uncertainties on the best measurement locations for representative body motion and for seat systems. In the present study, we measure road loads at four different locations of a body. A-pillars on the driver and passenger sides and left and right frame fronts of the front passenger seat mountings are selected to study the acceleration behavior at different locations. The measurements are conducted with passenger cars driving local roads at 50km/hr. The measured time-acceleration data are then transformed into PSD (power spectral density) data to compare the characteristics of local accelerations. By defining the deviated acceleration components from rigid body motion, the stiffness of vehicle body could be simply expressed in a quantitative basis. Measured data from two different vehicles are presented to demonstrate their relative vehicle body stiffness.

Vanishing 혼합재의 강성 특성 (Stiffness Characteristics of Vanishing Mixtures)

  • 쭝꽝훙;엄용훈;이창호;이종섭
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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    • pp.71-77
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    • 2008
  • Microstructural changes may arise due to the particle vanishing, fluid diffusion, heating, etc. This study focuses on the changes in small-strain shear stiffness in k0 loading produced by local straining in particular system made of sand-salt mixtures. Local strains were induced by dissolution of salt particles. Experiments were carried out in a conventional oedometer cell equipped with bender elements. Axial displacement and shear wave signals are recorded at each loading stage and during saturation process. Experimental data showed that microstructural changes due to particle vanishing were clearly captured by using shear wave measurement. Saturation of sand-salt mixture at a larger axial stress did not always create a more condense soil at the end of loading stage. Sand-salt mixture is useful for laboratory test on controlled artificial specimen.

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교량 토공 접속부에서 궤도강성변화에 대한 실험적 연구 (Experimental Study on the Variation of Track Stiffness between Earthwork and Bridge)

  • 나성훈;서사범;손기준;김정환
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2001년도 춘계학술대회 논문집
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    • pp.281-288
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    • 2001
  • In order to evaluate the effect of impact load at support stiffness transition area, the field estimations are performed at the transition zone between earthwork and bridge on test operation of KTX. Due to differential settlement caused by the variations of track support stiffness, large impact forces are investigated. However, the measured values such as wheel load, rail stress, displacement and acceleration in the transition area shows that the stiffness changes in the transition area are not abrupt, and the stiffness in the infra track structure varies continuously. In this experimental study, the parameters influencing safety of transition area are not governed by partial or local stiffness because cumulative passing loads are not sufficient on test operation of KTX.

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