• 한국의류산업학회지
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• 제2권5호
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• pp.437-442
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• 2000

In this paper, in order to examine the torsional behaviour of twisted yarn closely, the torsional rigidity would be derived in terms of physical and mechanical characteristics of its constituent fibers and yarn structural parameters by energy-method. And the propriety of the theory will be discussed by comparing with experimental results. The torsional rigidity of yarn in both experimental and theoretical results decreases with surface helix angle increases. But the experimental values are more higher than those of the theoretical ones.

• 대한기계학회논문집A
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• 제33권11호
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• pp.1217-1224
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• 2009

This paper presents a finite element (FE) analysis of the torsional rigidity of a two-stage cycloid drive. The cycloid disk makes contact with a number of pin-rollers simultaneously and eccentric shafts transmit not only torque of the spur gear stage to the cycloid disk, but also that of the cycloid disk to the output disk. Contacts between the disk and pin-rollers are simplified as linear spring elements, and the bearing of eccentric shaft is modeled as a rigid ring that has frictional contact to the disk and an elastic support. FE analysis for an ideal solid cycloid drive was performed and verified by a theoretical calculation. Accurate contact forces were then estimated by iterating between FE analysis for contact forces and Hertz theory calculations for nonlinear contact stiffness. In addition, torsional rigidity of the cycloid drive is analyzed to show that the bearing and nonlinear Hertz contact theory should be considered in analysis and design of a cycloid drive, which was verified with experiments. Finally, the effects of contact stiffness, bearing stiffness and cycloid disk structural stiffness according to the cycloid disk rotation on the torsional rigidity were investigated.

• 대한수학회논문집
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• 제10권2호
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• pp.461-469
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• 1995

Some bounds for anisotropic torsional rigidity with one plane of elastic symmetry perpendicular to the axis of the beam are derived by making use of the isoperimetric inequalities, complementary variational principles, and the maximum principle. Upper and lower bounds are obtained by applying the isoperimetric inequalities. While the upper bound investigated by the variational principles and maximum principle. The analysis is patterned after the work of Payne and Weinbeger [J. Math. Anal. Appl. 2(1961). pp. 210-216].

• Wind and Structures
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• 제11권2호
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• pp.153-178
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• 2008

Based on the empirical formulas for power spectra of generalized modal forces and local fluctuating wind forces in across-wind and torsional directions, the wind-induced lateral-torsional coupled response analysis of a representative rectangular tall building was conducted by setting various parameters such as eccentricities in centers of mass and/or rigidity and considering different torsional to lateral stiffness ratios. The eccentricity effects on the lateral-torsional coupled responses of the tall building were studied comprehensively by structural dynamic analysis. Extensive computational results indicated that the torsional responses at the geometric center of the building may be significantly affected by the eccentricities in the centers of mass and/or rigidity. Covariance responses were found to be in the same order of magnitude as the along-wind or across-wind responses in many eccentricity cases, suggesting that the lateral-torsional coupled effects on the overall wind-induced responses can not be neglected for such situations. The calculated results also demonstrated that the torsional motion contributed significantly to the total responses of rectangular tall buildings with mass and/or rigidity eccentricities. It was shown through this study that the framework presented in this paper provides a useful tool to evaluate the wind-induced lateral-torsional coupled responses of rectangular buildings, which will enable structural engineers in the preliminary design stages to assess the serviceability of tall buildings, potential structural vibration problems and the need for a detailed wind tunnel test.

• 한국공간구조학회논문집
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• 제12권2호
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• pp.65-72
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• 2012

본 연구에서는 비틀림 거동을 일으키는 편심구조물의 효율적인 제어를 위한 비틀림 강성을 가지는 동조질량감쇠기의 제어성능을 검토하고자 한다. 이를 위하여 지진하중을 받는 편심구조물에 동조질량감쇠기의 설치위치와 비틀림강성에 따른 제어성능을 평가한다. 반복되는 시간이력해석시 소요되는 해석시간을 줄이기 위하여 등가해석 모델을 사용하였고 비비례감쇠시스템인 동조질량감쇠가 설치된 구조물의 해석을 효율적으로 수행할 수 있었다. 본 연구를 통하여 일반적인 동조질량감쇠기에서 무시되어온 동조질량감쇠기의 비틀림 속성이 비틀림 거동이 발생하는 편심구조물에서는 효과적일 수 있음을 검증하였다. 그리고 편심구조물의 경우에는 동조질량감쇠기의 최적 설치 위치가 구조물 평면의 중심이 아닐 수 있음을 확인하였다.

• Earthquakes and Structures
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• 제13권1호
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• pp.9-15
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• 2017

In this paper, the influence of the rotational component, about a vertical axis, of earthquake ground motion on the response of building structures subjected to seismic action is considered. The torsional component of ground motion is generated from the records of translational components. Torsional component of ground motion is then, together with translational components, applied in numerical linear dynamic analysis of different reinforced concrete framed structure of three stories buildings. In total, more than 40 numerical models were created and analyzed. The obtained results show clearly the dependence of the effects of the torsional seismic component on structural system and soil properties. Thus, the current approach in seismic codes of accounting for the effects of accidental torsion due to the torsional ground motion, by shifting the center of mass, should be reevaluated.

• Earthquakes and Structures
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• 제9권4호
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• pp.753-766
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• 2015

An investigation has been carried out for the propagation of torsional surface waves in an inhomogeneous prestressed layer over an inhomogeneous half space when the upper boundary plane is assumed to be rigid. The inhomogeneity in density, initial stress (tensile and compressional) and rigidity are taken as an arbitrary function of depth, where as for the elastic half space, the inhomogeneity in density and rigidity is hyperbolic function of depth. In the absence of heterogeneities of medium, the results obtained are in agreement with the same results obtained by other relevant researchers. Numerically, it is observed that the velocity of torsional wave changes remarkably with the presence of inhomogeneity parameter of the layer. Curves are compared with the corresponding curve of standard classical elastic case. The results may be useful to understand the nature of seismic wave propagation in geophysical applications.

• Coupled systems mechanics
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• 제8권1호
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• pp.19-38
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• 2019

The influence of torsional rigidity of hinged flexible appendage on the linear dynamics of flexible spacecrafts with liquid on board was analyzed by considering the spacecraft's main body as a rigid tank, its flexible appendages as two elastically supported elastic beams, and the onboard liquid as an ideal liquid. The meniscus of the liquid free surface due to surface tension was considered. Using the Lagrangian of the spacecraft's main body (rigid tank), onboard liquid, and two beams (flexible appendages) in addition to assuming the system moved symmetrically, the coupled system frequency equations were obtained by applying the Rayleigh-Ritz method. The influence of the torsional rigidity of the flexible appendages on the spacecraft's coupled vibration characteristics was primary focus of investigation. It was found that coupled vibration modes especially that of appendage considerably changed with torsion spring parameter ${\kappa}_t$ of the flexible appendage. In addition, variation of the main body displacement with system parameters was investigated.

• Steel and Composite Structures
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• 제7권3호
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• pp.241-251
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• 2007

The purpose of this study is to calculate the torsional rigidity of arbitrarily shaped composite sections on the basis of hybrid finite element approach. An analogy is used between the torsion problem and deformation of a plate which exhibits only shear behavior. In the analysis a simple hybrid finite element based on Hellinger-Reissner functional is presented and a set of numerical examples are performed to demonstrate and asses the performance of the developed element in practical applications.

• Journal of Biosystems Engineering
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• 제27권4호
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• pp.283-292
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• 2002

Mechanical and physical properties of various parts of jujube (Zizyphus jojoba Miller) such as fruits, leaves, secondary branches, and leafy stems were measured and analyzed. The physical dimensions of the fruits were measured using a digital caliper, and the detachment force of the fruit and leafy stems was measured using a force gauge. The physical characteristics of the secondary branches such as the modulus of elasticity and the torsional rigidity were tested using a universal testing machine (UTM). The physical characteristics of leafy stems such as length and weight were also measured using a digital caliper and a digital scale, respectively. The detachment force of leafy stems and the area of the leaf also measured. The terminal velocities of the jujube fruits, leaves, and leafy stems were measured using a custom made terminal velocity experiment system. Diameter of the major and minor axis of the jujube fruit, weight of the fruit, and detachment force of the fruit stem was average of 32.02 mm, 23.92 mm. 10.0 ${\times}$ 10$\^$6/ ㎥, 8.99 g, and 5.43 N. respectively. The detachment forces of the jujube fruits increased and the force-to-weight ratio of the jujube fruits decreased as the weight of the jujube fruits increased. The modulus of elasticity of the secondary branches of the jujube was average of 7.01 ${\times}$ 10$\^$8/ N/㎡ and decreased as diameter of the secondary branches increased. The average torsional rigidity of the secondary jujube branches was 5.2 ${\times}$ 10$\^$-/ N/㎡, and the torsional rigidity decreased as the secondary branch diameter increased. The distribution of the torsional rigidity data associated with the diameter of the branches, however. widely scattered and it was difficult to find any relationship between the diameter of the branches and the torsional rigidity of tile branches. The weight of the leafy stems, number of loaves attached to the leafy stems, diameter of the stem side of the leafy stems, diameter of the leafy stem end was average or 0.7 g, 6.6 ea, 12.2 cm, 4.5 mm, and 2.7 mm, respectively. The major and minor axis of the .jujube loaves, area of leaves, weight of the leaves. and detachment force of the leaves was average of 5.7 cm, 3.3 cm, 12.98 cm$^2$, 0.20 g, and 4.39 N, respectively. The terminal velocity of the .jujube fruits increased as the weight of the fruits increased. The terminal velocity of the leafy stems, however, did not show a relationship with the weight of the leafy stems and the number of leaves attached to the leafy stem. The terminal velocity, however, slightly increased as the length of the leafy stems increased.