• Title/Summary/Keyword: Damping

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Effects of viscous damping models on a single-layer latticed dome during earthquakes

  • Zhang, Huidong;Wang, Jinpeng;Zhang, Xiaoshuai;Liu, Guoping
    • Structural Engineering and Mechanics
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    • v.62 no.4
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    • pp.455-464
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    • 2017
  • Rayleigh damping model is recommended in the recently developed Performance-Based Earthquake Engineering (PBEE) methodology, but this methodology does not provide sufficient information due to the complexity of the damping mechanism. Furthermore, each Rayleigh-type damping model may have its individual limitations. In this study, Rayleigh-type damping models that are used widely in engineering practice are discussed. The seismic performance of a large-span single-layer latticed dome subjected to earthquake ground motions is investigated using different Rayleigh damping models. Herein a simulation technique is developed considering low cycle fatigue (LCF) in steel material. In the simulation technique, Ramberg-Osgood steel material model with the low cycle fatigue effect is used to simulate the non-uniformly distributed material damping and low cycle fatigue damage in the structure. Subsequently, the damping forces of the structure generated by different damping models are compared and discussed; the effects of the damping ratio and roof load on the damping forces are evaluated. Finally, the low cycle fatigue damage values in sections of members are given using these damping models. Through a comparative analysis, an appropriate Rayleigh-type damping model used for a large span single-layer latticed dome subjected to earthquake ground motions is determined in terms of the existing damping models.

Dynamic characteristics of hybrid tower of cable-stayed bridges

  • Abdel Raheem, Shehata E.
    • Steel and Composite Structures
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    • v.17 no.6
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    • pp.803-824
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    • 2014
  • The dynamic characterization is important in making accurate predictions of the seismic response of the hybrid structures dominated by different damping mechanisms. Different damping characteristics arise from the construction of the tower with different materials: steel for the upper part; reinforced concrete for the lower main part and interaction with supporting soil. The process of modeling damping matrices and experimental verification is challenging because damping cannot be determined via static tests as can mass and stiffness. The assumption of classical damping is not appropriate if the system to be analyzed consists of two or more parts with significantly different levels of damping, such as steel/concrete mixed structure - supporting soil coupled system. The dynamic response of structures is critically determined by the damping mechanisms, and its value is very important for the design and analysis of vibrating structures. An analytical approach capable of evaluating the equivalent modal damping ratio from structural components is desirable for improving seismic design. Two approaches are considered to define and investigate dynamic characteristics of hybrid tower of cable-stayed bridges: The first approach makes use of a simplified approximation of two lumped masses to investigate the structure irregularity effects including damping of different material, mass ratio, frequency ratio on dynamic characteristics and modal damping; the second approach employs a detailed numerical step-by step integration procedure in which the damping matrices of the upper and the lower substructures are modeled with the Rayleigh damping formulation.

A Study on the Vibration Damping of Multilayer Damping Sheet (다층 제진판의 제진성 연구)

  • Kim, Won-Ho;An, Byeong-Hyeon;Ahn,
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.32 no.4
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    • pp.457-464
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    • 1996
  • The vibration damping of various multilayer damping sheet with different constraining layer and viscoelastic layer were investigated by Rheovibron and vibration test. Damping increased as dynamic loss tangent increased. Constrained type damping sheet showed better damping than extensional type damping sheet. Aluminum foil attached asphalt impregnated paper pad showed best damping.

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Vibration and Damping Characteristic of Composite Laminates Embedding Directional Damping Materials (방향성 있는 감쇠재료가 삽입된 복합적층판의 진동 및 감쇠특성)

  • 김성준
    • Composites Research
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    • v.16 no.5
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    • pp.39-44
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    • 2003
  • Embedding viscoelastic-damping materials into composites can greatly increase the damping properties of composite structures. Usually viscoelastic-damping materials behave isotropically so that their damping properties are the same in all directions. In these days, there is a desire to develop viscoelastic-damping materials that behave orthotropically so that damping properties vary with material orientation. These orthotropic damping materials can be made by embedding rows of thin wires within the viscoelastic materials. These wires add significant directional stiffness to the damping materials. where the stiffness variation with wire orientation follows classical lamination theory. In this paper, the loss factor of composite laminate was evaluated based on Ni and Adams' theory. To investigate the effect of directional damping material, the low-velociy impact response analysis was also performed. The present analysis results show that directional damping material has a great influence on vibration and damping characteristic of composite laminate.

An Optimal Placement of passive Constrained Layer Damping Treatment for Vibration Suppression of Automotive Roof (차량루프의 진동저감을 위한 수동구속감쇠처리의 위치 최적화)

  • Lee, Ki-Hwa;Kim, Chan-Mook;Kang, Young-Kyu
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.11a
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    • pp.349-353
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    • 2004
  • A study on optimal placement of constrained layer damping treatment for vibration control of automotive panels is presented. The effectiveness of damping treatment depends upon design parameters such as choice of damping materials, locations and size of the treatment. This paper proposes a CAE (Computer Aided Engineering) methodology based on finite element analysis to optimize damping treatment. From the equivalent modeling technique, it is found that the best damping performance occurs as the viscoelstic patch is placed by means of the modal strain energy method of bare structural panels to identify flexible regions, which in turn facilitates optimizations of damping treatment with respect to location and size. Different configurations of partially applied damping layer treatment have been analyzed for their effectiveness in realizing maximum system damping with minimum mass of the applied damping material. Moreover, simulated frequency response function of the automotive roof with and without damping treatments are compared, which show the benefits of applying damping treatment. Finally, the optimized damping treatment configuration is validated by comparing the locations and the size of the treatment with that of an experimental modal test conducted on roof compartment.

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Hydrodynamic Forces Characteristics of a Circular Cylinder with a Damping Plate (감쇠판이 부착된 원기둥의 동유체력 특성)

  • Cho, Il-Hyoung
    • Journal of Ocean Engineering and Technology
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    • v.25 no.1
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    • pp.1-7
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    • 2011
  • The radiation of water waves by a heaving truncated circular cylinder with damping plate is solved in the frame of the three-dimensional linear potential theory. The damping plate has a distinct advantage in reducing the motion response of a floating circular cylinder by increasing the added mass and the damping coefficient. Using the matched eigenfunction expansion method, the characteristics of hydrodynamic added mass and the damping coefficient are investigated with various system parameters, such as the radius and submergence depth of the damping plate. It is found that both added mass and the damping coefficient are significantly increased due to the arranged features of the larger damping plate with shallow submergence, which are positive factors as a motion reduction device of the floating offshore platform. Also the numerical results for an oscillating submerged disk show that the added mass is negative and that the damping coefficient has a peak value at resonant frequency when submergence depth is sufficiently small.

Seismic analysis of bridges based on stress-dependent damping

  • Su, Li;Wang, Yuanfeng;Li, Pengfei;Mei, Shengqi;Guo, Kun
    • Structural Engineering and Mechanics
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    • v.62 no.3
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    • pp.281-289
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    • 2017
  • Damping value has considerable influence on the dynamic and seismic behaviors of bridges. However, currently the constant damping ratios that are prescribed by most bridge seismic design codes can't truly represent the complicated damping character of actual structures. In this paper, a cyclic loading experiment was conducted to study the effect of stress amplitude on material damping of concrete to present an analyzing model of the material damping of concrete. Furthermore, based on the fundamental damping of structure measured under ambient vibration, combined with the presented stress-dependent material damping concrete, the seismic response of a bridge pier was calculated. Comparison between the calculated and experiment results verified the validity of the presented damping model. Finally, a modified design and analysis method for bridge was proposed based on stress-dependent damping theory, and a continuous rigid frame bridge was selected as the example to calculate the actual damping values and the dynamic response of the bridge under different earthquake intensities. The calculation results indicated that using the constant damping given by the Chinese seismic design code of bridges would overestimate the energy dissipation capacity of the bridge.

Application of Strain Energy for Determining the Location of Damping Material (스트레인 에너지를 이용한 제진재 위치 결정)

  • Kim, Joong-Bae;Ryu, Kuk-Hyun;Park, Sang-Kyu;Lee, Sang-Jo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.11
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    • pp.1199-1205
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    • 2008
  • The vehicle design engineers have studied the method of applying damping materials to the vehicle bodies by computer simulations and experimental methods in order to improve the vibration and noise characteristics of the vehicles. The unconstrained layer damping, being concerned with this study, has two layers(base layer and damping layer) and proyides vibration control of the base layer through extensional damping. Generally this kind of surface damping method is effectively used in reducing structural vibration at frequencies beyond 150Hz. The most important thing is how to apply damping treatment with respect to location and size of the damping material. To solve these problems, the current experimental methods have technical limits which are cumbersome, time consuming, and expensive. This Paper proposes a method based on finite element method and it employes averaged ESE(element strain energy) percent of total of dash panel assembly for 1/1 octave band frequency range by MSC/NASTRAN. The regions of high ESE percent of total are selected as proposed location of damping treatment. The effect of damping treatment is analyzed by comparing the frequency response function of the SPCC bare Panel and the damping treated panels.

Estimation of Damping Matrices for Dynamic Systems (동적 시스템의 감쇠행렬 추정)

  • Lee, Gun-Myung;Kim, Kyung-Ju;Ju, Young-Ho
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.10
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    • pp.1021-1027
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    • 2009
  • Finite element models of dynamic systems can be updated in two stages. In the first stage, mass and stiffness matrices are updated neglecting damping. In the second stage, a damping matrix is estimated with the mass and stiffness matrices fixed. Methods to estimate a damping matrix for this purpose are proposed in this paper. For a system with proportional damping, a damping matrix is estimated using the modal parameters extracted from the measured responses and the modal matrix calculated from the mass and stiffness matrices from the first stage. For a system with non-proportional damping, a damping matrix is estimated from the impedance matrix which is the inverse of the FRF matrix. Only one low or one column of the FRF matrix is measured, and the remaining FRFs are synthesized to obtain a full FRF matrix. This procedure to obtain a full FRF matrix saves time and effort to measure FRFs.

A Study on the Application of Semi-active Suspension System to a 3-D Full Vehicle Model (전차 모델에 대한 반능동 현가장치의 적용에 대한 연구)

  • 방범석;백윤수;박영필
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1994.10a
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    • pp.938-944
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    • 1994
  • Active damping has been shown to offer increased suspension performance in terms of vehicle isolation, suspension packaging, and road-tire contract force. Many semi-active damping strategies have been introduced to approximate the response of active damping with the modulation of passive damping parameters. This study investigates the characteristics of semi-active suspension control through the simulation of passive, skyhook active, and semi-active damping models. A quarter car model is studied with the conrolled damping replacing both passive and active damping. A new semi-active scheme is suggested to eliminate the abrupt changes in semi-active damping force. It is shown that the new strategy performs almost identically to the so called "force controlled" semi-active law without steep changes in damping force or body acceleration.eleration.

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