제어력 포화를 고려한 병진-비틀림 모드 연계 고층구조물의 진동제어

황재승,이상현,정란 한국풍공학회 2010 한국풍공학회지 Vol.14 No.3

풍하중을 받는 구조물은 해석의 편의상 층당 3개의 자유도를 가지는 해석모델을 사용한다. 구조물의 입면 형상이 비정형이 되고, 평면내 구조재의 배치가 층에 따라 변경이 되면 각층의 질량중심과 강성중심의 차이에 의해서 병진방향상호간 또는 병진방향과 비틀림 방향이 상호연관되어 이에 따른 각 방향의 고유모드가 연계된 진동특성을 가지게된다. 본 연구에서는 풍하중에 의한 구조물의 응답에 가장 큰 영향을 미치는 저차의 3개의 병진-비틀림 모드가 연계된 구조물의 진동을 저감하기위한 능동제어기법에 대하여 다룬다. 이를 위하여 풍동실험으로부터 구한 각 방향 밑면 전도모멘트와 비틀림모멘트가 연계모드에 작용하는 모달풍하중으로 치환된 운동방정식을 유도하고, 운동방정식에 기반한 상태방정식을 통하여 제어력을 산정한다. 제어력 포화를 고려하여 위상분할 제어알고리듬과 H∞ 제어알고리듬이 합성된 새로운 제어알고리듬을 제안하였으며, 풍동실험을 수행한바 있는 대상구조물에 대해 수치시뮬레이션을 수행한 결과 기존 제어알고리듬인 LQR에 비해 대등한 제어효과를 가지면서 제어력의 크기를 줄일 수 있는 것을 검증하였다. For the simplicity of analysis, tall building structures subject to wind load can be modeled with three degrees of freedom at each floor. The structure with irregular form in the shape and the distribution of structural elements has a difference between the center of the mass and rigidity, as a result, induce the complex vibration modes coupled with the lateral-torsional direction. In this study, an active vibration control technique is provided to control the vibration of lateral-torsionally coupled system with first three fundamental modes which govern the responses of structure under wind load. For this, an equation of motion with modal wind loads obtained from lateral overturning and torsional moment is derived, the control force is calculated based on the equation. Considering the saturation of control force, a new active control algorithm synthesized the H∞ control and phase division algorithm is proposed. Through the numerical analysis for the structure which wind tunnel test performed, it is proved that the proposed control algorithm in this study has an equivalent control effect and reduce the control forces dramatically compared to the conventional control algorithm such as LQR.

Lateral-torsional coupled vibration of a propulsion shaft with a diesel engine supported by a resilient mount

한형석,이경현,전수홍,박성호 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.8

Lateral-torsional coupled vibration destabilizes a rotating system. The instability region of the rotating system is the speed range where the frequencies of the lateral and torsional modes intersect. In this study, the abnormally increased vibration of the typical diesel enginereduction gear propulsion system for a naval vessel was examined in relation to the lateral-torsional coupled vibration under the assumption that it can be approximated by the Jeffcott rotor with three degrees of freedom. Through numerical and experimental investigation, a protection method was developed to avoid the unstable region of the diesel engine-reduction gear propulsion system.

Seismic torsional vibration in elevated tanks

Dutta, Sekhar Chandra,Murty, C.V.R.,Jain, Sudhir K. Techno-Press 2000 Structural Engineering and Mechanics, An Int'l Jou Vol.9 No.6

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 ${\tau}$.

독립성분분석(ICA)법을 이용한 병진-비틀림 연계된 구조물의 모드분리 및 응답기반 시스템식별

강경수(Kang Kyung-Soo),김홍진(Kim Hong-Jin),황재승(Hwang Jae-Seung) 대한건축학회 2012 大韓建築學會論文集 : 構造系 Vol.28 No.2

The response of a lateral-torsionally coupled structure subject to dynamic wind loads can include the response for the along wind direction as well as that of the across and torsional directions. This study aims to propose a procedure to separate the modal responses from the lateral-torsionally coupled structural responses by using the independent component analysis(ICA) method and to effectively estimate the dynamic properties from the separated modal responses. The wind loads for the dynamic analysis of structure are generated from Karman wind speed spectrum for the along wind direction and an empirical overturning moment spectrum for the across wind direction. The kurtosis is introduced as the performance index for the mode separation by ICA. For the verification of the proposed method, a numerical simulation is performed. In the simulation, it is found that the lateral-torsionally coupled modal response can be separated precisely by ICA technique and very closely located modes can be also separated. From the numerical results, it is also shown that the modal properties such as natural frequencies and damping ratios are estimated effectively using the Hilbert transform and curve fitting, respectively. The results in this study show that the proposed method can be very usefully applied to the output-only system identification.

독립성분분석(ICA)법을 이용한 병진-비틀림 연계된 구조물의 모드분리 및 응답기반 시스템식별

강경수,김홍진,황재승,Kang, Kyung-Soo,Kim, Hong-Jin,Hwang, Jae-Seung 대한건축학회 2012 대한건축학회논문집 Vol.28 No.2

The response of a lateral-torsionally coupled structure subject to dynamic wind loads can include the response for the along wind direction as well as that of the across and torsional directions. This study aims to propose a procedure to separate the modal responses from the lateral-torsionally coupled structural responses by using the independent component analysis(ICA) method and to effectively estimate the dynamic properties from the separated modal responses. The wind loads for the dynamic analysis of structure are generated from Karman wind speed spectrum for the along wind direction and an empirical overturning moment spectrum for the across wind direction. The kurtosis is introduced as the performance index for the mode separation by ICA. For the verification of the proposed method, a numerical simulation is performed. In the simulation, it is found that the lateral-torsionally coupled modal response can be separated precisely by ICA technique and very closely located modes can be also separated. From the numerical results, it is also shown that the modal properties such as natural frequencies and damping ratios are estimated effectively using the Hilbert transform and curve fitting, respectively. The results in this study show that the proposed method can be very usefully applied to the output-only system identification.

증속 기어전동 로터-베어링 시스템에서 횡-비틀림 연성진동 특성의 상세 고찰

이안성,하진웅,최동훈 한국소음진동공학회 2002 한국소음진동공학회 논문집 Vol.12 No.2

Applying a general coupled lateral and torsional vibration finite element model of gear pair element, this paper intends to look into in detail the coupled lateral and torsional vibration characteristics of a turbo-chiller rotor bearing system, having a bull-pinion speed increasing gear. Investigations have been carried out systematically by comparing the uncoupled and coupled natural frequencies and their mode shapes upon varying the gear mesh stiffness with considerations on rotating speeds, and also by comparing the strain energies of lateral and torsional vibration modes. Results hale shown that some modes may hale the coupled lateral and torsional mode characteristics as the gear mesh stiffness Increases over a certain value, and moreover that their associated dominant modes may be different from their initial modes, j.e., a certain dominant mode may change from an initial torsional one to a lateral one or from an initial lateral one to a torsional one.

증속 기어 전동 로터-베어링 시스템의 횡-비틀림 연성 유한요소 로터다이나믹 해석

이안성,하진웅,최동훈 한국소음진동공학회 2001 소음 진동 Vol.11 No.1

In a transmission or geared rotor system a coupled phenomenon of lateral and torsional vibrations may occur due to the gear meshing effect. Particularly, in high speed or low vibration and low noise applications of geared rotor systems a coupled rotordynamic analysis is required to precisely predict their dynamic characteristics. In this paper a generalized finite element model of a gear pair element is developed, which actively couples the lateral and torsional vibrations due to the gear meshing effect. In the modeling the generalized forces due to the transmission error. geometrical eccentricities. and unbalances in the gear system are also considered. Then. using the developed gear pair element model a coupled unforced rotordynamic analysis is performed with a prototype 800 RT turbo-chiller rotor-bearing system having a hull-pinion speed increasing gear. Results show that the torsional vibration characteristics experience some changes due to the gear meshing and lateral dynamic coupling effect, but that they have no adverse effect and the lateral ones have no practical changes in an operating speed range.

축계 모의 시험 장치를 이용한 비선형 축계 진동 분석

한형석(HyungSuk Han),박성호(SungHo Park),전수홍(SooHong Jeon) 한국소음진동공학회 2018 한국소음진동공학회 학술대회논문집 Vol.2018 No.10