scholarly journals Determining the level of damping vibration in bridges and footbridges

2016 ◽  
Vol 15 (1) ◽  
pp. 095-103
Author(s):  
Jacek Szulej ◽  
Paweł Ogrodnik
Keyword(s):  
Collocation Method ◽  
Energy Method ◽  
Time Course ◽  
Spectral Processing ◽  
Fem Model ◽  
Equivalent Damping ◽  
Damping Parameter ◽  
Arch Bridges ◽  
Equivalent Damping Coefficient ◽  
The Given

While designing slim and slender structures such as cable-stayed, suspended and arch bridges and footbridges, data on the dynamic behavior of structure are required. One of the main quantities, included in the calculations, is the damping parameter of vibration of the structure whose corresponding value has a direct impact on the proper behavior of the facility. One of currently applied approaches in the case of complex constructions, is the use of methods defining the equivalent damping coefficient which refers to the given form of natural vibrations. Among these methods, the collocation method and energy method can be distinguished. The collocation method refers to the existing facilities and requires performing measurements of vibration and spectral processing of time course of vibrations. The energy method requires the creation of FEM model of construction and it estimates the kinetic energy of the vibrating system. The above- mentioned methods are used in the calculations of the damping level of vibration of two structures, i.e.: arch John Paul II Bridge in Pulawy and a footbridge located in Lublin.

scholarly journals A numerical technique for a general form of nonlinear fractional-order differential equations with the linear functional argument

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Khalid K. Ali ◽  
Mohamed A. Abd El salam ◽  
Emad M. H. Mohamed
Keyword(s):  
Differential Equations ◽  
Collocation Method ◽  
Fractional Order ◽  
Linear Functional ◽  
Numerical Technique ◽  
Operational Matrix ◽  
Fractional Order Differential Equations ◽  
The Given ◽  
Functional Argument ◽  
Special Case

AbstractIn this paper, a numerical technique for a general form of nonlinear fractional-order differential equations with a linear functional argument using Chebyshev series is presented. The proposed equation with its linear functional argument represents a general form of delay and advanced nonlinear fractional-order differential equations. The spectral collocation method is extended to study this problem as a discretization scheme, where the fractional derivatives are defined in the Caputo sense. The collocation method transforms the given equation and conditions to algebraic nonlinear systems of equations with unknown Chebyshev coefficients. Additionally, we present a general form of the operational matrix for derivatives. A general form of the operational matrix to derivatives includes the fractional-order derivatives and the operational matrix of an ordinary derivative as a special case. To the best of our knowledge, there is no other work discussed this point. Numerical examples are given, and the obtained results show that the proposed method is very effective and convenient.

The Calculation of the Equivalent Linear Damping Coefficient of the Magnetorheological Damper

2013 ◽  
Vol 336-338 ◽  
pp. 475-479 ◽  
Author(s):  
Yao Hui Guo ◽  
En Wei Chen ◽  
Qun Wu ◽  
Yi Min Lu ◽  
Zeng Qiang Xia
Keyword(s):  
Mr Damper ◽  
Magnetorheological Damper ◽  
Damping Coefficient ◽  
Control Voltage ◽  
Characteristic Analysis ◽  
Equivalent Damping ◽  
Equivalent Linear ◽  
Linear Damping ◽  
Damper Control ◽  
Equivalent Damping Coefficient

MR damper (magnetorheological damper) has broad application prospects, and equivalent damping coefficient is very important of its dynamic characteristic analysis. Based on the modified Bouc_Wen model, the performance of MR damper was analyzed and the equivalent linear damping coefficient of MR damper was calculated. Based on simulation date of the modified Bouc_Wen model, the relationships between the equivalent linear damping coefficient of MR damper and the parameters of control voltage and MR dampers movement amplitude were established by the curve fitting regression analysis method. Verification results prove that the equivalent linear damping coefficient model has higher accuracy. For the vibration systems using strongly nonlinear MR damper, new model can effectively improve the efficiency of calculating the vibration analysis and the stability of the system in a certain frequency. At the same time, the model provides a theoretical basis for the application of MR damper control.

EVALUATIONS OF CLUSTER STRUCTURE AND MAGNETO-RHEOLOGY OF MR SUSPENSIONS

2005 ◽  
Vol 19 (07n09) ◽  
pp. 1437-1442 ◽  
Author(s):  
HIDEYA NISHIYAMA ◽  
KAZUNARI KATAGIRI ◽  
KATSUHISA HAMADA ◽  
KAZUTO KIKUCHI ◽  
KATSUHIKO HATA ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Cluster Formation ◽  
Cluster Structure ◽  
Mr Damper ◽  
Magnetic Flux Density ◽  
Equivalent Damping ◽  
Damping Characteristics ◽  
Mr Fluids ◽  
Equivalent Damping Coefficient ◽  
Particle Shapes

In the present study, we sysnthesize two types of MR fluids with different particle shapes and sizes. The magnetic functions are evaluated circulatingly by the analysis of cluster formation, rheological properties in the applied magnetic field and damping characteristics in the MR damper, comparing with those of commercial MR fluids. Final objective is to provide the fundamental data for the development of newly advanced MR fluids. The main topics consist of geographycal cluster formation depending on particle shapes and sizes, relating to the apparent viscosity and yield stress with magnetic flux density and further equivalent damping coefficient of two newly sysnthesised MR fluids comparing with those of LORD MR fluid.

Fabrication and characterization of highly controllable magnetorheological material in compression mode

2020 ◽  
Vol 31 (14) ◽  
pp. 1641-1661 ◽  
Author(s):  
Amin Fereidooni ◽  
Afonso Martins ◽  
Viresh Wickramasinghe ◽  
Afzal Suleman
Keyword(s):  
Magnetic Fields ◽  
Loss Factor ◽  
Magnetorheological Fluid ◽  
Loading Frequency ◽  
Magnetorheological Elastomer ◽  
Magnetorheological Elastomers ◽  
Equivalent Damping ◽  
Magnetorheological Effect ◽  
Equivalent Damping Coefficient

This article is focused on the development and characterization of highly controllable magnetorheological materials for stiffness and damping control in semi-active control applications. Two types of magnetorheological materials are developed in-house: magnetorheological elastomer with soft base elastomer, and magnetorheological fluid encapsulated in regular elastomer, namely magnetorheological fluid-elastomer. In both cases of magnetorheological elastomers and magnetorheological fluid-elastomers, the samples are evaluated using in-house-developed shear and compression test rigs, which are equipped with electromagnets and Hall effect sensors for measuring the magnetic field. These features provide the capability to precisely control a wide range of magnetic fields during the experiments. In the case of magnetorheological elastomers, the experimental results of the in-house magnetorheological elastomers are compared with commercially available counterparts made of hard base elastomer. It is shown that the controllability of the material, that is, the relative magnetorheological effect, is significantly improved in the case of magnetorheological elastomer with soft base elastomer. In addition to various magnetic fields, the samples are subjected to a range of loading amplitudes and frequencies. A general trend is observed where the frequency and strain amplitude cause an opposite effect on both the shear and compressive moduli: the increase in frequency gives rise to a higher value of modulus whereas the increase in amplitude reduces the modulus. Furthermore, the effect of bonding on the performance of the magnetorheological elastomers in compression mode is evaluated and the results indicate a significant increase in the modulus and decrease in the loss factor. In all the cases, however, the change of loss factor does not exhibit a predictable trend as a function of magnetic fields. In order to investigate a magnetorheological-based solution for controlling the damping of a semi-active system, magnetorheological fluid-elastomer samples are made in-house. These samples are fabricated using three different iron concentrations, and are tested in compression (squeeze) mode. The results of these experiments confirm that the equivalent damping coefficient of the material rises with the increase in magnetic field, and this effect becomes stronger as the iron concentration of magnetorheological fluids increases. It is also demonstrated that the magnetorheological effect is highly dependent on the loading frequency and amplitude, where the equivalent damping coefficient decreases with the increase in loading frequency and amplitude. In all the aforementioned cases, the stiffness of magnetorheological fluid-elastomers exhibits minor changes, which offers the in-house-developed magnetorheological fluid-elastomers as a damping only control option, a development that is different from the magnetorheological fluid-elastomers reported in the literature.

Calculation Analysis of Strengthening Arch Bridge Structure Based on Release Energy Method

2011 ◽  
Vol 71-78 ◽  
pp. 1732-1735
Author(s):  
Qing Ping Jin ◽  
Xian Bao Wang ◽  
Xue Jun Li
Keyword(s):  
Energy Method ◽  
Carrying Capacity ◽  
Safety Margin ◽  
Bridge Structure ◽  
Masonry Arch ◽  
Arch Bridge ◽  
Before And After ◽  
Arch Bridges ◽  
Calculation Analysis ◽  
Masonry Arch Bridge

The arch bridges were used widely for the good performance under the pressure in China. It was very sensitive to some factors as temperature , settlement etc so that the arch bridges occurred the disease, carrying capacity reduction or even structure destruction etc.In the paper, based on the characteristics of masonry arch bridges, reinforcement method was analyzed, according to the situation of a masonry arch bridge, release energy method was applied to strengthening project. By comparing the stress and the strain before and after the strengthening project, some conclusions could be drawn that the bridge structure carrying capacity had been raised, the energy accumulated in the bridge structure was released, the structure safety margin was improved.

scholarly journals Numerical Solution of Nonlinear Sine-Gordon Equation by Modified Cubic B-Spline Collocation Method

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
R. C. Mittal ◽  
Rachna Bhatia
Keyword(s):  
Numerical Solution ◽  
Collocation Method ◽  
Gordon Equation ◽  
Spline Collocation ◽  
Sine Gordon Equation ◽  
B Spline ◽  
Spline Collocation Method ◽  
B Splines ◽  
Spline Basis ◽  
The Given

Modified cubic B-spline collocation method is discussed for the numerical solution of one-dimensional nonlinear sine-Gordon equation. The method is based on collocation of modified cubic B-splines over finite elements, so we have continuity of the dependent variable and its first two derivatives throughout the solution range. The given equation is decomposed into a system of equations and modified cubic B-spline basis functions have been used for spatial variable and its derivatives, which gives results in amenable system of ordinary differential equations. The resulting system of equation has subsequently been solved by SSP-RK54 scheme. The efficacy of the proposed approach has been confirmed with numerical experiments, which shows that the results obtained are acceptable and are in good agreement with earlier studies.

Shafting Vibration Simulation for Hydro Turbine Generating Sets

2013 ◽  
Vol 444-445 ◽  
pp. 1171-1176
Author(s):  
Yun Zeng ◽  
Li Xiang Zhang ◽  
Jing Qian ◽  
Cheng Li Zhang
Keyword(s):  
Vibration Amplitude ◽  
Angular Speed ◽  
Transient Model ◽  
Integrated Simulation ◽  
Hydro Turbine ◽  
Equivalent Damping ◽  
Generating Sets ◽  
Mass Eccentricity ◽  
Equivalent Damping Coefficient ◽  
Vibration Simulation

Based on the transient model of hydro turbine generating sets (HTGS), the integrated simulation system of HGTS is built to study shafting stability. Given different bearing stiffness, equivalent damping coefficient and mass eccentricity, the change characteristics of shafting vibration at rated angular speed in steady and maximum angular speed in transient are simulated, and which are applied to study inferences shafting parameters and angular speed on shafting vibration. Simulation results show that the relationship between shafting vibration amplitude and angular speed is linear. however, the vibration amplitude increment produced by angular speed error will be amplified while the shafting stiffness is weaker, mass eccentricity of the runner and rotor is larger.

An Iterative Algorithm to Determine Hot Strand Pressures during Continuous Casting of Round Blooms

2011 ◽  
Vol 284-286 ◽  
pp. 1196-1204
Author(s):  
Ke Liu ◽  
Zhan Guang Han ◽  
Jia Quan Zhang
Keyword(s):  
Quantitative Analysis ◽  
Iterative Algorithm ◽  
Normal Force ◽  
Force Distribution ◽  
Cooling Zone ◽  
Secondary Cooling ◽  
Fem Model ◽  
Secondary Cooling Zone ◽  
The Given

Ovality defect of round bloom castings is the haunting defect of demanding grades steel, which can be attributed to excessive mechanical stress imposed by the roll containment especially at the unbending region. A 2-D elastic-plastic FEM model has been developed for the quantitative analysis of the effects of hot strand pressures on the ovality deformation and the contact normal force distribution. It is shown that higher friction force and smaller reduction deformation can be expected through the adoption of grooved rolls for given hot strand pressures as compared with plain rolls. For the determination of whether the given hot strand pressures can meet the requirement of strand downslide control in the caster, the resistances generated in the mold, secondary cooling zone and unbending zone are analyzed. Accordingly, an iterative algorithm has been presented to modify the hot strand pressures for given caster. A set of modified hot strand pressures has been computationally determined, which has been proved to be safe in production for casting round bloom with diameter up to Φ400mm with better roundness and less roller mark.

A new type of damper combining eddy current damping with rack and gear

2020 ◽  
pp. 107754632093711
Author(s):  
Yafeng Li ◽  
Shouying Li ◽  
Jianzhong Wang ◽  
Zhengqing Chen
Keyword(s):  
Eddy Current ◽  
Permanent Magnets ◽  
Air Gap ◽  
Damping Coefficient ◽  
Apparent Mass ◽  
Damping Force ◽  
Equivalent Damping ◽  
Eddy Current Damping ◽  
New Type ◽  
Equivalent Damping Coefficient

A new type of damper combining eddy current damping with rack and gear, which can simultaneously export damping and inertial forces, is proposed. Eddy current damping with rack and gear is supposed to be installed between the building superstructure and foundation to mitigate the seismic response of the building. First, the concept of eddy current damping with rack and gear is introduced in detail and its apparent mass and equivalent damping coefficient are both theoretically investigated. Second, a prototype of eddy current damping with rack and gear is manufactured, and a series of tests on the prototype are carried out to verify its structural parameters. The experimental and theoretical results of the apparent mass of the prototype agree well with each other. The experimental result of the equivalent damping coefficient of the prototype is slightly lower than the numerical results obtained from COMSOL Multiphysics and its maximum relative differences are 11.3% and 13.6% for α = 0° and 45°, respectively. Third, detailed parametric studies on the damping force, including the effects of the thickness of the conductor plate, air gap, and number and location of permanent magnets, are conducted. The results show that the damping force keeps a linear relationship with velocity if it is lower than 0.15 m/s, and with the increase of the velocity, a strong nonlinear relationship between the damping force and the velocity is observed. The available maximum damping force can be increased by decreasing the thickness of the conductor plate and the air gap, increasing the number of permanent magnets. There is an optimal location about the permanent magnets for the available maximum damping force. In addition, the hysteretic curves of the eddy current damping with rack and gear obtained from the test indicate that the ability of energy dissipation is considerable.

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