• Title/Summary/Keyword: 면외 고유진동

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Seismic Performance Evaluation of Unreinforced and ECC-jacketed Masonry Fences using Shaking Table Test (진동대실험을 사용한 비보강 및 ECC 자켓 보강 조적담장의 내진성능평가)

  • Yonghun Lee;Jinwoo Kim;Jae-Hwan Kim;Tae-Sung Eom;Sang-Hyun Lee
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.27 no.6
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    • pp.182-192
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    • 2023
  • In this study, the efficacy of Engineered Cementitious Composite(ECC) jacket for masonry fences subjected to lateral dynamic load was experimentally verified through a shaking table test, comparing it with the performance of an unreinforced masonry(URM) fence. Firstly, dominant frequencies, modal damping ratios and deformed shapes were identified through an impact hammer test. URM and ECC-strengthened fences with heights of 940mm and 970mm had natural frequencies of 6.4 and 35.3Hz, and first modal damping ratios of 7.0 and 5.3%, respectively. Secondly, a shaking table test was conducted in the out-of-plane direction, applying a historical earthquake, El Centro(1940) scaled from 25 to 300%. For the URM fence, flexural cracking occurred at the interface of brick and mortar joint(i.e., bed joint) at the ground motion scaled to 50%, and out-of-plane overturning failure followed during the subsequent test conducted at the ground motion scaled to 30%. On the other hand, the ECC-jacketed fence showed a robust performance without any crack or damage until the ground motion scaled to 300%. Finally, the base shear forces exerted upon the URM and ECC-jacketed fences by the ground motions scaled to 25~300% were evaluated and compared with the ones calculated according to the design code. In contrast to the collapse risk of the URM fence at the ground motion of 1,000-year return period, the ECC-jacketed fence was estimated to remain safe up to the 4,800-year return period ground motion.

Optical technique of precision measurement using Electronic Speckle Pattern Interferometry (ESPI를 이용한 광학식 정밀 계측 기술)

  • 은재정;정영환;최평석;박해수
    • Journal of the Institute of Convergence Signal Processing
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    • v.4 no.4
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    • pp.40-46
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    • 2003
  • In this research, we accomplished the interpreting about the vibration of the object, which is the out of plane displacement in the Electronic Speckle Pattern Interferometry(ESPI), one of the optical measuring technique. The vibrating object has a inherent nodal line, therefore we can get the information about the vibration of the object by interpreting it. we used a speaker and a cantilever plate for a measurement object, and interpreted it qualitatively by using the Time-Average ESPI. In this experimental result, the speaker has the lower mode of fringe at 550Hz, 570mV, and the higher mode of fringe at 950Hz, 570mV This ESPI is a non-destructive test, and because of using the laser at measuring, it has a high resolution. The ESPI can test vibration mode regardless of the test object size, because the area which illuminated laser is the test area.

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An Eigen Analysis with Out-of-Plane Deformable Ring Element (면외변형 링 요소를 이용한 고유해석)

  • Moon, Won-Joo;Min, Oak-Key;Kim, Yong-Woo
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.7 s.94
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    • pp.1719-1730
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    • 1993
  • This paper presents the theoretical natural frequencies of out-of-plane deformable ring based on the variables such as out-of-plane deflection, torsional rotation and shear rotation. Based on the same variables, a finite element eigen analysis is carried out by using the $C^0$-continuous, isoparametric element which has three nodes per element and three degrees-of-freedom at each node. Numerical experiments are peformed to find the integration scheme which produces accurate natural frequencies, natural modes and correct rigid body motion. The uniformly reduced integration and the selective reduced integration give more accurate numerical frequencies than the uniformly full integration, but the uniformly reduced integration produces incorrect rigid body motion while selective reduced integration does correct one. Therefore, the ring element based on the three variables which employes selective reduced integration is recommended to avoid spurious modes, to alleviate the error due to shear locking and to produce correct rigid body motion, simultaneously.

Analysis of Out-of-plane Motion of a Disc Brake System Considering Contact Stiffness (접촉 강성을 고려한 디스크브레이크의 면외진동 해석)

  • Joe, Yong-Goo;Oh, Jae-Eung;Shin, Ki-Hong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.05a
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    • pp.597-600
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    • 2004
  • A two-degree-of-freedom out-of-plane model with contact stiffness is presented to describe dynamical interaction between the pad and disc of a disc brake system. It is assumed that the out-of-plane motion of the system depends on the friction force acting along the in-plane direction. Dynamic friction coefficient is modelled as a function of both in-plane relative velocity and out-of-plane normal force. When the friction coefficient depends only on the relative velocity, the contact stiffness has the role of negative stiffness. The results of stability analysis show that the stiffness of both pad and disc are equally important. Complex eigenvalue analysis is conducted for the case that the friction coefficient is also dependent on the normal force. The results further verify the importance of the stiffness. It has also been found that increasing the gradient of friction coefficient with respect to the normal force makes the system more unstable. Nonlinear analysis is also performed to demonstrate various responses. Comparing the responses with experimental data has shown that the proposed model may qualitatively well represent a certain type of brake noise.

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Aeroelastic Behaviors of Self-anchored Suspension Bridge with Lateral Sag of Main Cable(II) - Focused on the Behavior of Tower - (횡방향 새그를 가진 자정식 현수교의 공탄성 거동(II) - 주탑의 거동을 중심으로 -)

  • Kwon, Soon Duck;Chang, Sung Pil
    • Journal of Korean Society of Steel Construction
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    • v.9 no.2 s.31
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    • pp.269-275
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    • 1997
  • Wind tunnel test results and their interpretations, which were performed to study the aerodynamic stability of tower of self-anchored suspension bridge, are presented in this paper. Tower and full models were tested under smooth and turbulent flow conditions. In the case of the tower with inclined two columns, the vibration due to wakes were occurred at wide velocity zone because the wakes with various frequencies were generated by inclined upstream column. It has to be emphasized that the vibration characteristics of the tower in the self-anchored suspension bridge may be very sensitive to the longitudinal boundary conditions of the girder at the supports. Because of the two natural frequency of the tower, out-of-plane bending and torsional, were not well separated, coupled motions were observed in a wide range of wind velocity. The effectiveness of corner cut, countermeasure to reduce the tower vibrations, was also studied. It has been found that 1:10, comer cut size to column width, may be the most effective ratio for reducing the vibrations.

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Analysis of the Crankshaft Behavior on In-plane and Out-plane Mode at the Firing Stage (엔진 운전시 크랭크샤프트의 면내.외 모드의 거동 해석)

  • Abu Aminudin;Lee, Hae-Jin;Lee, Jung-Youn;Oh, Jae-Eung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.4 s.109
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    • pp.319-328
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    • 2006
  • This paper presents a method for analysis of the mechanical behavior of a crankshaft in a four-cylinder internal combustion engine. The purpose of the analysis was to study the characteristics of the shaft in which the pin and arm parts were assumed to have a uniform section in order to simplify the modal analysis. The results of natural frequency transfer function and mode shape were compared with those obtained by experimental work. The results obtained from the comparison showed a good agreement with each other and consequently verified the analysis model. Furthermore, a prediction of crankshaft characteristics under the firing condition, by using the model, was performed. This study describes a new method for analyzing the dynamic behavior of crankshaft vibrations in the frequency domain based on the initial firing stages. The new method used RMS values to calculate the energy at each bearing journal and counter weight shape modification under the operating conditions.

Topology Design Optimization of Plate Buckling Problems Considering Buckling Performance (좌굴성능을 고려한 평판 좌굴문제의 위상설계최적화)

  • Lee, Seung-Wook;Ahn, Seung-Ho;Cho, Seonho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.28 no.5
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    • pp.441-449
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    • 2015
  • In this paper we perform a linearized buckling analysis using the Kirchhoff plate theory and the von Karman nonlinear strain-displacement relation. Design sensitivity analysis(DSA) expressions for plane elasticity and buckling problems are derived with respect to Young's modulus and thickness. Using the design sensitivity, we can formulate the topology optimization method for minimizing the compliance and maximizing eigenvalues. We develop a topology optimization method applicable to plate buckling problems using the prestress for buckling analysis. Since the prestress is needed to assemble the stress matrix for buckling problem using the von Karman nonlinear strain, we introduced out-of-plane motion. The design variables are parameterized into normalized bulk material densities. The objective functions are the minimum compliance and the maximum eigenvalues and the constraint is the allowable volume. Through several numerical examples, the developed DSA method is verified to yield very accurate sensitivity results compared with the finite difference ones and the topology optimization yields physically meaningful results.