• Title, Summary, Keyword: stiffness

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Analysis of the Dynamical Characteristics and Prediction of Stiffness for the Joint between Members (부재간 결합부의 동적 특성 분석 및 강성 예측)

  • Yun, Seong-Ho
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.18 no.2
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    • pp.58-64
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    • 2019
  • This paper describes the analysis of dynamic characteristics and prediction of the stiffness for the joint between structural members. In the process of deriving the governing equations, the stiffness values responsible for the moment and shear force were modelled by using linear and torsional springs in the middle of a clamped-clamped beam. The sensitivities of the natural frequency and modal assurance criterion were investigated as a function of the dimensionless linear and torsional spring stiffness. The reliability of the predictions for the linear and torsional stiffness values was verified by the inverse computations of the stiffness matrix. The predictive and exact theoretical stiffness values were compared for the stiffness element in the finite element formulation, and their results show an excellent correlation. It is strongly anticipated that although the proposed methodology is currently limited to the analytical utilization, it will provide a useful tool to estimate unknown joint stiffness values based on the experimental natural frequency and mode shape.

Stiffness model for "column face in bending" component in tensile zone of bolted joints to SHS/RHS column

  • Ye, Dongchen;Ke, Ke;Chen, Yiyi
    • Steel and Composite Structures
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    • v.38 no.6
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    • pp.637-656
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    • 2021
  • The component-based method is widely used to analyze the initial stiffness of joint in steel structures. In this study, an analytical component model for determining the column face stiffness of square or rectangular hollow section (SHS/RHS) subjected to tension was established, focusing on endplate connections. Equations for calculating the stiffness of the SHS/RHS column face in bending were derived through regression analysis using numerical results obtained from a finite element model database. Because the presence of bolt holes decreased the bending stiffness of the column face, this effect was calculated using a novel plate-spring-based model through numerical analysis. The developed component model was first applied to predict the bending stiffness of the SHS column face determined through tests. Furthermore, this model was incorporated into the component-based method with other effective components, e.g., bolts under tension, to determine the tensile stiffness of the T-stub connections, which connects the SHS column, and the initial rotational stiffness of the joints. A comparison between the model predictions, test data, and numerical results confirms that the proposed model shows satisfactory accuracy in evaluating the bending stiffness of SHS column faces.

Current Collection of Catenary System with Time-Varying Stiffness (시변강성 가선계의 집전성능)

  • 최연선
    • Journal of the Korean Society for Railway
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    • v.3 no.3
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    • pp.131-138
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    • 2000
  • The design of current collection system of high speed train requires the fundamental understandings for the dynamic characteristics of catenary system and pantograph. The stiffness of catenary system of high speed train has the varying characteristics for the change of contact point with pantograph, since the supporting pole and hanger make the different boundary conditions for the up-down stiffness of a trolley wire. The variation of stiffness results in Mathiue equation, which characterizes the stability of the system. However, the two-term variation of the stiffness due to span length and hanger distance cannot be solved analytically. In this paper, the stiffness variations are calculated and the physical reasoning of linear model and one term Mathieu equation are reviewed. And the numerical analysis for the two-term variation of the stiffness is done for the several design parameters of pantograph.

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A Study on the Behavior Properties of Residential-Commercial Building by Pushover Analysis (정적탄소성해석에 의한 복합구조물의 거동특성에 관한 연구)

  • 강병두;전대한;김재웅
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.209-216
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    • 2000
  • The purpose of this study is to investigate elasto-plastic behaviour and estimate ultimate resistance capacity of the residential-commercial building subjected to lateral force along the height of structure. Four types of residential-commercial building are chosen as analytical models and investigated by pushover analysis. Pushover analysis estimates initial elastic stiffness, post-yielding stiffness, and plastic hinges on each story of structures through three-dimensional nonlinear analysis program CANNY-99. Skeleton curve of bending stiffness model is bilinear, shear stiffness model is trilinear, and axial stiffness model is elastic. Skeleton curve of axial stiffness model has the axial compression and tension stiffness of reinforced concrete members. This study presents the change of inter story drift, story stiffness and hinge of story and member.

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Changes of Masticatory Muscle Tone and Stiffness According to Head Posture

  • Wang, Joongsan
    • Journal of International Academy of Physical Therapy Research
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    • v.10 no.2
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    • pp.1763-1767
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    • 2019
  • Background: Although previous researches have developed interventions for neck problems, headache, and temporomandibular disorder in patients with forward head posture (FHP), changes in masticatory muscle tone or stiffness as FHP worsening have not been investigated. Objective: To examine changes in masticatory muscle tone and stiffness through craniovertebral angle (CVA). Design: Cross sectional study Methods: The subjects were 21 healthy males with normal head posture. Three CVA were established for posture measurement in which the bilateral anterior temporal and masseter muscles were measured during the subjects maintained a series of postures. Results: The Right masseter muscle significantly increased in stiffness with advancing FHP (p < 0.05). No significant changes were observed in the muscle tone or stiffness of any other masticatory muscles, and no significant differences were found in bilateral masticatory muscle tone or stiffness in each measurement posture. Conclusions: This study suggests that the increased stiffness of the right masseter muscle as the FHP worsened requires consideration in physical therapy assessment and intervention.

Analysis of Effects of Stiffness Increment Factors for Deciding the Initial Structural System of Tall Buildings (초고층건물 초기 구조시스템 선정을 위한 강성증가요인 효과 분석)

  • Lee, Jae-Cheol;Jung, Jong-Hyun
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.857-862
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    • 2007
  • The purpose of this research is to compare the stiffness increment effects with the floor plan shapes by the stiffness increment factors. For this, we generated the standard floor plans with Box and T type shapes. Then applied the stiffness increment factors -outrigger, material strength, member section- to those floor plans, and generated several alternative analysis models that make the effects of the factors to the lateral displacement exposed. Finally, we analyzed the stiffness increment effects and compared with each other by the stiffness increment factors. As a result, we found that the increment effects have not influence to floor plan shapes, and orders of stiffness increment effects are outrigger, core wall and material strength. We expect that the results of this study could be effectively utilized in the schematic structural design of tall buildings.

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Investigation for the Restriction of the Stiffness and Mechanical Impedance of the Shipboard Floor and Foundation Considering Dynamic Stiffness of the Anti-Vibration Mount (방진 마운트의 동적 강성을 고려한 선체 바닥 및 받침대의 강성과 임피던스 규제에 대한 고찰)

  • Han, Hyung-Suk;Son, Yoon-Jun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.511-517
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    • 2009
  • The mechanical impedance and stiffness of the foundation of shipboard equipments and hulls supported by anti-vibration mount are very important so that the anti-vibration mount can accomplish its performance effectively. But, it is frequently argued how much stiffness and mechanical impedance are necessary for those foundations and hulls. In this research, it is discussed by evaluating the dynamic stiffness of the commercial anti-vibration mounts used in a naval vessel. Consequently, in this research, the minimum level of the mechanical impedance and stiffness of the foundation of shipboard equipments and hulls are suggested considering the dynamic stiffness of the mount which varies as frequency.

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Estimation of Hysteretic Interfacial Stiffness of Contact Surfaces

  • Kim, Nohyu
    • Journal of the Korean Society for Nondestructive Testing
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    • v.33 no.3
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    • pp.276-282
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    • 2013
  • This paper proposes an ultrasonic method for measurement of linear and hysteretic interfacial stiffness of contacting surfaces between two steel plates subjected to nominal compression pressure. Interfacial stiffness was evaluated by the reflection and transmission coefficients obtained from three consecutive reflection waves from solid-solid surface using the shear wave. A nonlinear hysteretic spring model was proposed and used to define the quantitative interfacial stiffness of interface with the reflection and transmission coefficients. Acoustic model for 1-D wave propagation across interfaces is developed to formulate the reflection and transmission waves and to determine the linear and nonlinear hysteretic interfacial stiffness. Two identical plates are put together to form a contacting surface and pressed by bolt-fastening to measure interfacial stiffness at different states of contact pressure. It is found from experiment that the linear and hysteretic interfacial stiffness are successfully determined by the reflection and transmission coefficient at the contact surfaces through ultrasonic pulse-echo measurement.

The Influence of Suspension Stiffness on the Gearbox Input Loads in a 3-Point Suspension Wind Turbine Drive Train (풍력발전기용 3점 지지 드라이브 트레인의 지지 강성이 기어박스 입력하중에 미치는 영향)

  • Nam, Ju Seok;Nam, Yong Yun
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.24 no.5
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    • pp.514-520
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    • 2015
  • The effects of suspension stiffness on the reaction load of the gearbox suspension for a three-point suspension wind turbine drive train were investigated by finite element analysis. The reaction forces of the gearbox suspension appear to increase as the gearbox suspension stiffness increases; however, the main bearing stiffness has a reverse effect on the reaction forces. The influence of the gearbox suspension stiffness is greater than that of the main bearing. Since the suspensions must provide the gearbox with proper support, it is not practical to use soft gearbox suspension for small reaction forces. It is more feasible to use stiff main bearings. As a guideline for the main bearing stiffness in the present study, we propose a relative stiffness of 100-150% of the reference.

Stability Analysis of High-speed Driveshafts under the Variation of the Support Conditions (초고속 구동축의 지지 조건에 따른 안정성 분석)

  • Shin, Eung-Su
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.20 no.1
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    • pp.40-46
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    • 2011
  • This paper is to investigate the effects of the asymmetrical support stiffness on the stability of a supercritical driveshaft with asymmetrical shaft stiffness and anisotropic bearings. The equations of motion is derived for a system including a rigid disk, a massless flexible asymmetric shaft, anisotropic bearings and a support beam. The Floquet theory is applied to perform the stability analysis with the variation of the support stiffness, the shaft asymmetry, the shaft damping and the shaft speed. The results show that the asymmetric support stiffness is closely related to the stability caused by primary resonance as well as the supercritical operation. First, the stiffness variation can stabilize the system around primary resonance by weakening the parametric resonance from the shaft asymmetry. Second, it also improve the stability characteristics at a supercritical operation when the support stiffness is not so high relative to the shaft stiffness.