• 제목/요약/키워드: Stiffness predictions

검색결과 158건 처리시간 0.024초

점탄성 제진 요소의 복소동강성계수 산출을 위한 상용유한요소 코드 이용시 복소탄성계수의 정하중 의존성 반영 방법 (Consideration of Static-strain-dependent Dynamic Complex Modulus in Dynamic Stiffness Calculation of Viscoelastic Mount/Bushing by Commercial Finite Element Codes)

  • 김광준;신윤호
    • 한국소음진동공학회논문집
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    • 제16권4호
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    • pp.372-379
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    • 2006
  • Little attention has been paid to static-strain-dependence of dynamic complex modulus of viscolelastic materials in computational analysisso far. Current commercial Finite Element Method (FEM) codes do not take such characteristics into consideration in constitutive equations of viscoelastic materials. Recent experimental observations that static-strain-dependence of dynamic complex modulus of viscolelastic materials, especially filled rubbers, are significant, however, require that solutions somehow are necessary. In this study, a simple technique of using a commercial FEM code, ABAQUS, is introduced, which seems to be far more cost/time saving than development of a new software with such capabilities. A static-strain-dependent correction factor is used to reflect the influence of static-strains in Merman model, which is currently the base of the ABAQUS. The proposed technique is applied to viscoelastic components of rather complicated shape to predict the dynamic stiffness under static-strain and the predictions are compared with experimental results.

Nonlinear model to predict the torsional response of U-shaped thin-walled RC members

  • Chen, Shenggang;Ye, Yinghua;Guo, Quanquan;Cheng, Shaohong;Diao, Bo
    • Structural Engineering and Mechanics
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    • 제60권6호
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    • pp.1039-1061
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    • 2016
  • Based on Vlasov's torsional theory of open thin-walled members and the nonlinear constitutive relations of materials, a nonlinear analysis model to predict response of open thin-walled RC members subjected to pure torsion is proposed in the current study. The variation of the circulatory torsional stiffness and warping torsional stiffness over the entire loading process and the impact of warping shear deformation on the torsion-induced rotation of the member are considered in the formulation. The torque equilibrium differential equation is then solved by Runge-Kutta method. The proposed nonlinear model is then applied to predict the behavior of five U-shaped thin-walled RC members under pure torsion. Four of them were tested in an earlier experimental study by the authors and the testing data of the fifth one were reported in an existing literature. Results show that the analytical predictions based on the proposed model agree well with the experimental data of all five specimens. This clearly shows the validity of the proposed nonlinear model analyzing behavior of U-shaped thin-walled RC members under pure torsion.

반복하중을 받는 볼트 연결부에 대한 역학적인 고등해석 모델의 개발 (Development of Advanced Mechanical Analysis Models for the Bolted Connectors under Cyclic Loads)

  • 허종완
    • 대한토목학회논문집
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    • 제33권1호
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    • pp.101-113
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    • 2013
  • 반복적인 하중을 받는 볼트 연결부의 비선형적인 거동을 예측할 수 있는 역학적 고등해석 모델을 개발하는 데 주된 초점을 두어 본 연구를 수행하였다. 또한 대표적인 접합부 형태인 T-stub 접합부의 연결 컴포넌트에 대한 실제의 하중 재하 실험값을 활용한 해석으로 얻어진 거동에 대한 예측의 정확성 및 모형화의 타당성을 입증하였다. 연결부를 이루고 있는 구성요소들의 거동은 볼트의 인장변형, T-stub 플랜지의 휨변형, T-stub 몸체의 신장, 전단볼트의 지압 및 미끄러짐을 포함하며 접합부내에서 개별적인 힘-변위 메커니즘으로부터 정의된 다중 선형의 강성모델에 의하여 재현된다. 이러한 구성요소들은 그들의 거동특성을 지닌 비선형 스프링으로 모형화되어 역학적 해석 모델에 설치되어 연결부 전체의 거동을 수치해석적인 방법으로 예측하도록 한다. 해석 모델에 의한 예측값은 강성, 강도 및 변형 측면에서 실험값과 비교하여 정확성을 평가하였으며 이를 근거로 본 연구에서 제안된 역학적 해석 모델이 볼트 연결부의 거동과 성능을 만족하며 예측 가능하다는 결론을 내렸다.

전단슬립 효과를 고려한 합성보의 유효강성 (Effective Stiffness of Composite Beams Considering Shear Slip Effects)

  • 허병욱;배규웅;문태섭
    • 한국강구조학회 논문집
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    • 제16권5호통권72호
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    • pp.671-682
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    • 2004
  • 본 연구는 부분 전단연결을 가지는 강-콘크리트 합성보의 처짐에 미치는 전단슬립의 영향을 조사하는 것이다. 현재 각국의 설계규준에서는 합성보의 처짐 계산시 전단연결재의 강도와 관련되어 있지만, 본 연구에서는 하중조건에 상관없는 전단연결재의 강성에 기반을 둔 정확한 해를 유도하였다. 우선, 평형조건, 곡률의 적합조건에 기반을 둔 3가지 하중조건에서의 합성보의 등가강성을 유도하고, 이로부터 하중조건에 상관없이 슬립의 영향을 적용할 수 있는 간편한 제안식을 유도하였다. 이러한 제안식의 타당성을 검증하기 위해서 현재 AISC에서 사용하고 있는 합성보의 유효강성 및 Nie가 제안한 식과 비교하였다. 일반적으로 사용되는 보의 경우, 전단슬립의 영향은 스팬이 짧을 경우, AISC에 비해서 최대 18%까지의 강성의 감소를 나타냄을 알 수 있었다. 완전합성보의 경우, AISC의 제안 값이 본 연구의 결과 보다 크게 나타났는데, 이는 안전측이 되지 못함을 알 수 있었으며, 불완전 합성보의 경우, AISC 제안식이 본 연구보다 강성을 과소 평가하는 결과를 나타내었다.

심포일을 갖는 가스 포일 저널 베어링의 성능 예측 (Performance Predictions of Gas Foil Journal Bearing with Shim Foils)

  • 황성호;문창국;이종성;김태호
    • Tribology and Lubricants
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    • 제34권3호
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    • pp.107-114
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    • 2018
  • This paper presents a computational model of a gas foil journal bearing with shim foils between the top foil and bumps, and predicts its static and dynamic performance. The analysis takes the previously developed simple elastic foundation model for the top foil-bump structure and advances it by adding foil models for the "shim foil" and "outer top foil." The outer top foil is installed between the (inner) top foil and bumps, and the shim foil is installed between the inner top foil and outer top foil. Both the inner and outer top foils have an arc length of $360^{\circ}$, but the arc length of the shim foil is shorter, which causes a ramp near its leading edge in the bearing clearance profile. The Reynolds equation for isothermal and isoviscous ideal gas solves the hydrodynamic pressure that develops within the bearing clearance with preloads due to the ramp. The centerline pressure and film thickness predictions show that the shim foil mitigates the peak pressure occurring at the loading direction, and broadens the positive pressure as well as minimum film thickness zones except for the shortest shim foil arc length of $180^{\circ}$. In general, the shim foil decreases the journal eccentricity, and increases the power loss, direct stiffness, and damping coefficients. As the shim foil arc length increases, the journal eccentricity decreases while the attitude angle, minimum film thickness, and direct stiffness/damping coefficients in the horizontal direction increase.

슬래브의 시공하중에 대한 동바리 강성 및 슬래브 균열의 영향 II: 계측 및 비교 (Effects of Shore Stiffness and Concrete Cracking on Slab Construction Load II: Measurements and Comparisons)

  • 황현종;홍건호;박홍근;김용남;김재요
    • 콘크리트학회논문집
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    • 제22권1호
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    • pp.51-58
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    • 2010
  • 연계 논문에서는 슬래브의 시공하중을 산정하는 간략화한 방법을 개발하였다. 기존 방법과 달리, 제안 방법은 동바리 강성과 시공하중에 의한 콘크리트 균열 효과를 고려할 수 있다. 이 연구에서는 실제 플랫 플레이트 슬래브에서 시공하중을 계측하였다. 제안 방법의 입증을 위하여, 계측된 동바리 하중은 제안 방법과 기존 방법으로 예측한 결과와 비교되었다. 또한, 제안 방법은 기존 연구에서 측정된 벽식 구조에도 적용되었고, 예측 결과는 계측 결과와 비교되었다. 비교 결과, 제안 방법은 시공하중을 잘 예측하였고, 기존 방법에 비해 더 우수한 예측 결과를 보여주었다.

Study on Vortex-Induced Vibration Predictions for Ship Rudders

  • Jang, Won-Seok;Hong, Suk-Yoon;Song, Jee-Hun;Kwon, Hyun-Wung;Choi, Woen-Sug
    • 한국해양공학회지
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    • 제34권5호
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    • pp.325-333
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    • 2020
  • As regulations concerning ship vibration and noise are becoming stricter, considerable attention is being drawn to prediction technologies for ship vibration and noise. In particular, the resonance and lock-in phenomena caused by vortex-induced vibration (VIV) have become considerably important with increases in the speed and the size of ships and ocean structures, which are known to cause structural problems. This study extends the fluid-structure interaction (FSI) analysis method to predict resonances and lock-in phenomena of high modes and VIV of ship rudders. Numerical stability is secured in underwater conditions by implementing added mass, added damping, and added stiffness by applying the potential theory to structural analysis. An expanded governing equation is developed by implementing displacements and twist angles of high modes. The lock-in velocity range and resonant frequencies of ship rudders obtained using the developed FSI method agree well with the experimental results and the analytic solution. A comparison with local vibration guidelines published by Lloyd's Register shows that predictions of resonances and lock-in phenomena of high modes are necessary in the shipbuilding industry due to the possible risks like fatigue failure.

Vibration behaviour of cold-formed steel and particleboard composite flooring systems

  • AL Hunaity, Suleiman A.;Far, Harry;Saleh, Ali
    • Steel and Composite Structures
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    • 제43권3호
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    • pp.403-417
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    • 2022
  • Recently, there has been an increasing demand for buildings that allow rapid assembly of construction elements, have ample open space areas and are flexible in their final intended use. Accordingly, researchers have developed new competitive structures in terms of cost and efficiency, such as cold-formed steel and timber composite floors, to satisfy these requirements. Cold-formed steel and timber composite floors are light floors with relatively high stiffness, which allow for longer spans. As a result, they inherently have lower fundamental natural frequency and lower damping. Therefore, they are likely to undergo unwanted vibrations under the action of human activities such as walking. It is also quite expensive and complex to implement vibration control measures on problematic floors. In this study, a finite element model of a composite floor reported in the literature was developed and validated against four-point bending test results. The validated FE model was then utilised to examine the vibration behaviour of the investigated composite floor. Predictions obtained from the numerical model were compared against predictions from analytical formulas reported in the literature. Finally, the influence of various parameters on the vibration behaviour of the composite floor was studied and discussed.

Axial compressive behavior of high strength concrete-filled circular thin-walled steel tube columns with reinforcements

  • Meng Chen;Yuxin Cao;Ye Yao
    • Structural Engineering and Mechanics
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    • 제88권1호
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    • pp.95-107
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    • 2023
  • In this study, circular thin-walled reinforced high strength concrete-filled steel tube (RHSCFST) stub columns with various tube thicknesses (i.e., 1.8, 2.5 and 3.0mm) and reinforcement ratios (i.e., 0, 1.6%, 2.4% and 3.2%) were fabricated to explore the influence of these factors on the axial compressive behavior of RHSCFST. The obtained test results show that the failure mode of RHSCFST transforms from outward buckling and tearing failure to drum failure with the increasing tube thickness. With the tube thickness and reinforcement ratio increased, the ultimate load-carrying capacity, compressive stiffness and ductility of columns increased, while the lateral strain in the stirrup decreased. Comparisons were also made between test results and the existing codes such as AIJ (2008), BS5400 (2005), ACI (2019) and EC4 (2010). It has been found that the existing codes provide conservative predictions for the ultimate load-carrying capacity of RHSCFST. Therefore, an accurate model for the prediction of the ultimate load-carrying capacity of circular thin-walled RHSCFST considering the steel reinforcement is developed, based on the obtained experimental results. It has been found that the model proposed in this study provides more accurate predictions of the ultimate load-carrying capacity than that from existing design codes.

Analysis of mechanical performance of continuous steel beams with variable section bonded by a prestressed composite plate

  • Tahar Hassaine Daouadji;Rabahi Abderezak;Benferhat Rabia
    • Steel and Composite Structures
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    • 제50권2호
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    • pp.183-199
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    • 2024
  • In this paper, a closed-form rigorous solution for interfacial stress in continuous steel beam with variable section strengthened with bonded prestressed FRP plates and subjected to a uniformly distributed load is developed using linear elastic theory and including the variation of fiber volume fractions with a longitudinal orientation of the fibers of the FRP plates. The results show that there exists a high concentration of both shear and normal stress at the ends of the laminate, which might result in premature failure of the strengthening scheme at these locations. The theoretical predictions are compared with other existing solutions. Overall, the predictions of the different solutions agree closely with each other. A parametric study has been conducted to investigate the sensitivity of interface behavior to parameters such as laminate and adhesive stiffness, the thickness of the laminate and the fiber volume fractions where all were found to have a marked effect on the magnitude of maximum shear and normal stress in the composite member. This research gives a numerical precision in relating to the others studies which neglect the effect of prestressed plate and the shear lag impact. The physical and geometric properties of materials are taken into account, and that may play an important role in reducing the interfacial stresses magnitude.