• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 지반공학 공동 학술발표회
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• pp.613-620
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• 2005

This research is experimental paper to prepare the structural safety of the upper bridge for support type on tunnel and the effect of settlement. Unit weight test and uni-axial compression test have been performed to simulate the physical property of foundation on the tunnel. Tunnel model of slip form type for centrifuge model has been developed to performed the tunnel excavation while field stress is activated. And the support type of tunnel such as umbrella arch method and large diameter steel pipe reinforce method has been tested for the centrifuge model. After the analysis of experiment, results show that internal displacement of large diameter steel pipe reinforce method is smaller than that of the umbrella arch method.

• 대한기계학회논문집
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• 제17권12호
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• pp.2982-2994
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• 1993

Low-velocity impact responses of composite laminates are investigated using the finite element method based on various theories. In two-dimensional nonlinear analysis, a displacement field considering higher order shear deformation and large deflection of the laminate is assumed and a finite element formulation is developed using a C$^{o}$-continuous 9-node plate element. Also, three-dimensional linear analysis based on the infinitesimal strain-displacement assumptions is performed using 8-node brick elements with incompatible modes. A modified Hertzian contact law is incorporated into the finite element program to evaluate the impact force. In the time integration, the Newmark constant acceleration algorithm is used in conjuction with successive iterations within each time step. Numerical results from static analysis as well as the impact response analysis are presented including impact force histories, deflections, strains in the laminate. Impact responses according to two typical low-velocity impact conditions are compared each other.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.167-170
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• 2003

In this paper, the electromechanical displacements of curved actuators using laminated composites are calculated by finite element method to design the optimal configuration of curved actuators. To predict the pre-stress in the device due to the mismatch in coefficients of thermal expansion, the carbon-epoxy and glass- epoxy as well as PZT ceramic is also numerically modeled by using hexahedral solid elements. Because the modeling of these thin layers causes the numbers of degree of freedom to increase, large-scale structural analyses are performed in a cluster system in this study. The curved shape and pre-stress in the actuator are obtained by the cured curvature analysis. The displacement under the piezoelectric force by an applied voltage is also calculated to compare the performance of curved actuator. The thickness of composite is chosen as design factor.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.669-673
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• 2001

The objective of this paper is to predict and evaluate the sealing performance of the thermoplastic rubber component in the proto-design stage. The large strain and large deformation properties of rubber are modeled by strain energy function and the related material constants are calculated from the test data. The viscoelastic property of the rubber is also considered using the coefficients in a Prony series representation of a viscoelastic modulus ken the compression stress relaxation test. The results show that the current design of cap mount system has 2-different stiffness caused by the cap-mount contact and the viscoelastic property of rubber plays an important role in time dependent deformation.

• 방사성폐기물학회지
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• 제19권4호
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• pp.533-546
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• 2021

Large earthquakes with (M_W > ~ 6) result in ground shaking, surface ruptures, and permanent deformation with displacement. The earthquakes would damage important facilities and infrastructure such as large industrial establishments, nuclear power plants, and waste disposal sites. In particular, earthquake ruptures associated with large earthquakes can affect geological and engineered barriers such as deep geological repositories that are used for storing hazardous radioactive wastes. Earthquake-driven faults and surface ruptures exhibit various fault zone structural characteristics such as direction of earthquake propagation and rupture and asymmetric displacement patterns. Therefore, estimating the respect distances and hazardous areas has been challenging. We propose that considering multiple parameters, such as fault types, distribution, scale, activity, linkage patterns, damage zones, and respect distances, enable accurate identification of the sites for deep geological repositories and important facilities. This information would enable earthquake hazard assessment and lower earthquake-resulted hazards in potential earthquake-prone areas.

• Journal of information and communication convergence engineering
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• 제22권2호
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• pp.127-132
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• 2024

Haptic actuators for large display panels play an important role in bridging the gap between the digital and physical world by generating interactive feedback for users. However, the generation of meaningful haptic feedback is challenging for large display panels. There are dead zones with low haptic sensations when a small number of actuators are applied. In contrast, it is important to control the traveling wave generated by the actuators in the presence of multiple actuators. In this study, we propose a particle swarm optimization (PSO)-based algorithm for the haptic localization of plates with electrostatic vibration actuators. We modeled the transverse displacement of a plate under the effect of actuators by employing the Kirchhoff-Love plate theory. In addition, starting with twenty randomly generated particles containing the actuator parameters, we searched for the optimal actuator parameters using a stochastic process to yield localization. The capability of the proposed PSO algorithm is reported and the transverse displacement has a high magnitude only in the targeted region.

• 농업생명과학연구
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• 제50권1호
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• pp.273-281
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• 2016

본 연구에서는 온실시공 및 유지관리 지침마련을 위한 기초자료로 사용하기 위하여 플라스틱 필름 온실의 구조재를 대상으로 휨 시험을 실시한 후, 하중-변위의 관계를 검토하였다. 그 결과 시편의 형상에 관계없이 시편의 규격이 클수록 항복 및 최대하중이 큰 경향을 보였으며, 변위도 동일한 양상을 보였다. 강관이 각관보다 항복 및 최대하중은 적게 나타났으며, 변위는 크게 나타났으며, 강관의 경우는 항복 및 최대하중 하에서의 변위는 각각 1.42~4.20mm 및 5.80~24.13mm정도의 범위에 있었다. 각관의 경우에 변위는 각각 1.62~3.00mm 및 3.13~8.01mm정도의 범위였다. 그리고 본 시험의 결과와 기존의 연구에서 제시한 기준 값들을 보면, 동일한 부재임에도 불구하고 부재들이 사용되는 온실형태나 사용목적(예, 샛기둥)에 따라 큰 차이가 있음을 알 수 있었다. 또한 유리온실인 와이드 스팬 및 벤로 형을 대상으로 제시하고 있는 경우(h/100, h/80)에도 변형이 각각 28.0mm 및 35.0mm(기둥 길이 280cm 적용)정도로서 네델란드의 유리온실 표준 기준(14.0mm)과 비교해도 큰 차이가 있었다. 스팬이 60cm인 경우, 주서까래나 도리 부재의 본 시험결과는 기존의 연구에서 제시한 값들 보다 각각 55.7% 및 39.3%정도 크게 나타났다. 그리고 기둥의 경우, NEN의 기준 값인 14.0mm와 비교해서 본 시험결과는 43.7%정도 적은 것으로 나타났다. 따라서 변위제한은 온실의 종류나 형태 및 규격 등 다양한 요인에 의해서 다를 수 있기 때문에 이들 요인들을 반영한 연구나 시험들을 진행하여 온실 시공 및 유지관리 등에 반영할 수 있도록 하여야 할 것으로 판단되었다.

• Structural Engineering and Mechanics
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• 제62권5호
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• pp.619-629
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• 2017

This paper focuses on the study of complete dynamic modeling and maximum dynamic load carrying capacity computation of N-flexible links and N-flexible joints mobile manipulator undergoing large deformation. Nonlinear dynamic analysis relies on the Timoshenko theory of beams. In order to model the system completely and precisely, structural and joint flexibility, nonlinear strain-displacement relationship, payload, and non-holonomic constraints will be considered to. A finite element solution method based on mixed method is applied to model the shear deformation. This procedure is considerably more involved than displacement based element and shear deformation can be readily included without inducing the shear locking in the element. Another goal of this paper is to present a computational procedure for determination of the maximum dynamic load of geometrically nonlinear manipulators with structural and joint flexibility. An effective measure named as Moment-Height Stability (MHS) measure is applied to consider the dynamic stability of a wheeled mobile manipulator. Simulations are performed for mobile base manipulator with two flexible links and joints. The results represent that dynamic stability constraint is sensitive when calculating the maximum carrying load. Furthermore, by changing the trajectory of end effector, allowable load also changes. The effect of torsional spring parameter on the joint deformation is investigated in a parametric sensitivity study. The findings show that, by the increase of torsional stiffness, the behavior of system approaches to a system with rigid joints and allowable load of robot is also enhanced. A comparison is also made between the results obtained from small and large deformation models. Fluctuation range in obtained figures for angular displacement of links and end effector path is bigger for large deformation model. Experimental results are also provided to validate the theoretical model and these have good agreement with the simulated results.

• Structural Engineering and Mechanics
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• 제9권6호
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• pp.615-636
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• 2000

Some elevated water tanks have failed due to torsional vibrations in past earthquakes. The overall axisymmetric structural geometry and mass distribution of such structures may leave only a small accidental eccentricity between centre of stiffness and centre of mass. Such a small accidental eccentricity is not expected to cause a torsional failure. This paper studies the possibility of amplified torsional behaviour of elevated water tanks due to such small accidental eccentricity in the elastic as well as inelastic range; using two simple idealized systems with two coupled lateral-torsional degrees of freedom. The systems are capable of retaining the characteristics of two extreme categories of water tanks namely, a) tanks on staging with less number of columns and panels and b) tanks on staging with large number of columns and panels. The study shows that the presence of a small eccentricity may lead to large displacement of the staging edge in the elastic range, if the torsional-to-lateral time period ratio $({\tau})$ of the elevated tanks lies within a critical range of 0.7< ${\tau}$ <1.25. Inelastic behaviour study reveals that such excessive displacement in some of the reinforced concrete staging elements may cause unsymmetric yielding. This may lead to progressive strength deterioration through successive yielding in same elements under cyclic loading during earthquakes. Such localized strength drop progressively develop large strength eccentricity resulting in large localized inelastic displacement and ductility demand, leading to failure. So, elevated water tanks should have ${\tau}$ outside the said critical range to avoid amplified torsional response. The tanks supported on staging with less number of columns and panels are found to have greater torsional vulnerability. Tanks located near faults seem to have torsional vulnerability for large ${\tau}$.

• Wind and Structures
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• 제28권2호
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• pp.71-87
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• 2019

The yaw and interference effects of blades affect aerodynamic performance of large wind turbine system significantly, thus influencing wind-induced response and stability performance of the tower-blade system. In this study, the 5MW wind turbine which was developed by Nanjing University of Aeronautics and Astronautics (NUAA) was chosen as the research object. Large eddy simulation on flow field and aerodynamics of its wind turbine system with different yaw angles($0^{\circ}$, $5^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$ and $45^{\circ}$) under the most unfavorable blade position was carried out. Results were compared with codes and measurement results at home and abroad, which verified validity of large eddy simulation. On this basis, effects of yaw angle on average wind pressure, fluctuating wind pressure, lift coefficient, resistance coefficient,streaming and wake characteristics on different interference zone of tower of wind turbine were analyzed. Next, the blade-cabin-tower-foundation integrated coupling model of the large wind turbine was constructed based on finite element method. Dynamic characteristics, wind-induced response and stability performance of the wind turbine structural system under different yaw angle were analyzed systematically. Research results demonstrate that with the increase of yaw angle, the maximum negative pressure and extreme negative pressure of the significant interference zone of the tower present a V-shaped variation trend, whereas the layer resistance coefficient increases gradually. By contrast, the maximum negative pressure, extreme negative pressure and layer resistance coefficient of the non-interference zone remain basically same. Effects of streaming and wake weaken gradually. When the yaw angle increases to $45^{\circ}$, aerodynamic force of the tower is close with that when there's no blade yaw and interference. As the height of significant interference zone increases, layer resistance coefficient decreases firstly and then increases under different yaw angles. Maximum means and mean square error (MSE) of radial displacement under different yaw angles all occur at circumferential $0^{\circ}$ and $180^{\circ}$ of the tower. The maximum bending moment at tower bottom is at circumferential $20^{\circ}$. When the yaw angle is $0^{\circ}$, the maximum downwind displacement responses of different blades are higher than 2.7 m. With the increase of yaw angle, MSEs of radial displacement at tower top, downwind displacement of blades, internal force at blade roots all decrease gradually, while the critical wind speed decreases firstly and then increases and finally decreases. The comprehensive analysis shows that the worst aerodynamic performance and wind-induced response of the wind turbine system are achieved when the yaw angle is $0^{\circ}$, whereas the worst stability performance and ultimate bearing capacity are achieved when the yaw angle is $45^{\circ}$.