The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Gaetan Kerschen - One of the best experts on this subject based on the ideXlab platform.
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nonlinear generalization of Den Hartog s equal peak method
Mechanical Systems and Signal Processing, 2015Co-Authors: Giuseppe Habib, Thibaut Detroux, Regis Viguie, Gaetan KerschenAbstract:Abstract This study addresses the mitigation of a nonlinear resonance of a mechanical system. In view of the narrow bandwidth of the classical linear tuned vibration absorber, a nonlinear absorber, termed the nonlinear tuned vibration absorber (NLTVA), is introduced in this paper. An unconventional aspect of the NLTVA is that the mathematical form of its restoring force is tailored according to the nonlinear restoring force of the primary system. The NLTVA parameters are then determined using a nonlinear generalization of Den Hartog׳s equal-peak method. The mitigation of the resonant vibrations of a Duffing oscillator is considered to illustrate the proposed developments.
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generalization of Den Hartog s equal peak method for nonlinear primary systems
MATEC Web of Conferences, 2014Co-Authors: Giuseppe Habib, Thibaut Detroux, Gaetan KerschenAbstract:This study addresses the mitigation of one problem nonlinear resonance of a mechanical system. In view of the narrow bandwidth of the classical linear tuned vibration absorber, a new nonlinear absorber, termed the nonlinear tuned vibration absorber (NLTVA), is introduced in this paper. One unconventional aspect of the NLTVA is that the mathematical form of its restoring force is tailored according to the nonlinear restoring force of the primary system. The NLTVA parameters are then determined using a nonlinear generalization of Den Hartog’s equal-peak method. The mitigation of the resonant vibrations of a Duffing oscillator is considered to illustrate the proposed developments.
Dongwei Wang - One of the best experts on this subject based on the ideXlab platform.
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Analysis of wind attack angle increments in wind tunnel tests for the aerodynamic coefficients of iced hangers
Advances in Structural Engineering, 2019Co-Authors: Shengli Li, Dongwei WangAbstract:Wind attack angle increments are important inputs for the accurate and efficient wind tunnel test in analyzing the aerodynamic coefficients and Den Hartog galloping coefficients of iced cable struc...
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Influence of catwalk design parameters on the galloping of constructing main cables in long-span suspension bridges
Journal of Vibroengineering, 2017Co-Authors: Shengli Li, Chaoqun Wang, Yanan Hu, Dongwei WangAbstract:A main cable of a long-span suspension bridge is semi-surrounded by a catwalk during construction. Thus, design parameters of a catwalk may have influences on the galloping stability of a main cable during construction. To study the influence of catwalk design parameters on the galloping of steepled main cables, two main foci have been conducted. Firstly, the aerodynamic coefficients of the catwalk with actual design parameters are obtained by numerical simulation based on computational fluid dynamics (CFD), and the numerical results are compared with those of the previous wind tunnel test. Several typical main cables with different cross sections of a long-span suspension bridge during construction are selected, and their Den Hartog coefficients are obtained based on the numerical simulation considering the aerodynamic influences of the catwalks. Then four typical working conditions of a main cable which have great potential to occur galloping are selected based on the galloping analyze, and their aerodynamic coefficients considering the influence of the catwalk with different design parameters are obtained. The influence of the catwalk design parameters on galloping of the main cables is analyzed based on the Den Hartog criterion. Results indicate that catwalk design parameters have eviDent influences on aerodynamic coefficients and galloping of the main cables. The parameters of the catwalk which are favorable for suppressing the galloping of the main cables are determined, which establish a good guideline for the galloping-resistant design of the catwalk-main cable system on suspension bridges.
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Experimental and numerical studies on galloping of the flat-topped main cables for the long span suspension bridge during construction
Journal of Wind Engineering and Industrial Aerodynamics, 2017Co-Authors: Shengli Li, Yonghui An, Chaoqun Wang, Dongwei WangAbstract:Abstract The flat-topped main cables of the long span suspension bridge may occur galloping in the wind field during construction; however, little about galloping of the flat-topped main cables has been found in the existing literature; so it is important to address this problem. The present paper has two main parts, i.e. the numerical simulation and the wind tunnel test. In the first part, numerical simulation using the method of CFD (Computational Fluid Dynamics) is implemented to obtain the aerodynamic coefficients of six main cables with different cross sections at different wind attack angles from −5 to 5°. Then the corresponding Den Hartog coefficients of the six cables against the angle of attack are determined to predict the transverse galloping. Moreover, the Den Hartog coefficients of the six cables are compared with each other, and results show that generally the number of wind attack angles corresponded to negative Den Hartog coefficients presents a trend of increase with the progress of the construction. In the second part, models of three representative main cables are made by rigid plastics using the Three Dimension Printing Technology, and the aerodynamic coefficients of these cables are obtained by wind tunnel test; then the aerodynamic coefficients based on numerical simulation and wind tunnel test are compared together. It can be seen that the experimental results of the relationship of aerodynamic coefficients and the wind attack angles is close to the corresponding numerical results. As a result, the numerical simulation method in this paper can be used to study the galloping of main cables with different cross sections; moreover, the probability of the galloping occurrence increases with the progress of the construction. The present work lays a good foundation for safety alerts of the flat-topped main cables in construction.
Giuseppe Habib - One of the best experts on this subject based on the ideXlab platform.
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nonlinear generalization of Den Hartog s equal peak method
Mechanical Systems and Signal Processing, 2015Co-Authors: Giuseppe Habib, Thibaut Detroux, Regis Viguie, Gaetan KerschenAbstract:Abstract This study addresses the mitigation of a nonlinear resonance of a mechanical system. In view of the narrow bandwidth of the classical linear tuned vibration absorber, a nonlinear absorber, termed the nonlinear tuned vibration absorber (NLTVA), is introduced in this paper. An unconventional aspect of the NLTVA is that the mathematical form of its restoring force is tailored according to the nonlinear restoring force of the primary system. The NLTVA parameters are then determined using a nonlinear generalization of Den Hartog׳s equal-peak method. The mitigation of the resonant vibrations of a Duffing oscillator is considered to illustrate the proposed developments.
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generalization of Den Hartog s equal peak method for nonlinear primary systems
MATEC Web of Conferences, 2014Co-Authors: Giuseppe Habib, Thibaut Detroux, Gaetan KerschenAbstract:This study addresses the mitigation of one problem nonlinear resonance of a mechanical system. In view of the narrow bandwidth of the classical linear tuned vibration absorber, a new nonlinear absorber, termed the nonlinear tuned vibration absorber (NLTVA), is introduced in this paper. One unconventional aspect of the NLTVA is that the mathematical form of its restoring force is tailored according to the nonlinear restoring force of the primary system. The NLTVA parameters are then determined using a nonlinear generalization of Den Hartog’s equal-peak method. The mitigation of the resonant vibrations of a Duffing oscillator is considered to illustrate the proposed developments.
J. H. G. Macdonald - One of the best experts on this subject based on the ideXlab platform.
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misconceptions and generalizations of the Den Hartog galloping criterion
Journal of Engineering Mechanics-asce, 2014Co-Authors: Nikolaos Nikitas, J. H. G. MacdonaldAbstract:Classical quasi-steady galloping analysis deals exclusively with cases of across-wind vibrations, leaving aside the more general situation where the wind and motion may not be normal. This can arise in many circumstances, such as in the motion of a power transmission cable about its equilibrium configuration that is swayed from the vertical plane as a result of the mean wind or in a tall slender structure in a skewed wind. Furthermore, the generalization to such situations, when this had been made, has only considered special issues. In this paper, the correct equations for the quasi-steady aerodynamic damping coefficients for a rotated system or wind are derived, and the differences from other variants are highlighted. Motion in two orthogonal structural planes is considered, potentially giving coupled translational galloping, for which previous analysis has often been limited or has even arrived at erroneous conclusions. For the two-degree-of-freedom case, the behavior is depenDent on the structural as well as the aerodynamic parameters, in particular the orientation of the principal structural axes and the relative natural frequencies in the two planes. For the first time, the differences in the aerodynamic damping and zones of galloping instability are quantified between solutions from the correct perfectly tuned, well detuned, and classical Den Hartog equations (and also an incorrect generalization of the latter) for a variety of typical cross-sectional shapes. It is found that although the Den Hartog summation often gives a reasonable estimate for the actual aerodynamic damping, even in the rotated situation, in some circumstances the differences can be quite large.
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Misconceptions and Generalizations of the Den Hartog Galloping Criterion
Journal of Engineering Mechanics, 2014Co-Authors: Nikolaos Nikitas, J. H. G. MacdonaldAbstract:Classical quasi-steady galloping analysis deals exclusively with cases of across-wind vibrations, leaving aside the more general situation where the wind and motion may not be normal. This can arise in many circumstances, such as in the motion of a power transmission cable about its equilibrium configuration that is swayed from the vertical plane as a result of the mean wind or in a tall slender structure in a skewed wind. Furthermore, the generalization to such situations, when this had been made, has only considered special issues. In this paper, the correct equations for the quasi-steady aerodynamic damping coefficients for a rotated system or wind are derived, and the differences from other variants are highlighted. Motion in two orthogonal structural planes is considered, potentially giving coupled translational galloping, for which previous analysis has often been limited or has even arrived at erroneous conclusions. For the two-degree-of-freedom case, the behavior is depenDent on the structural as well as the aerodynamic parameters, in particular the orientation of the principal structural axes and the relative natural frequencies in the two planes. For the first time, the differences in the aerodynamic damping and zones of galloping instability are quantified between solutions from the correct perfectly tuned, well detuned, and classical Den Hartog equations (and also an incorrect generalization of the latter) for a variety of typical cross-sectional shapes. It is found that although the Den Hartog summation often gives a reasonable estimate for the actual aerodynamic damping, even in the rotated situation, in some circumstances the differences can be quite large. ? 2013 American Society of Civil Engineers.
Shengli Li - One of the best experts on this subject based on the ideXlab platform.
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Analysis of wind attack angle increments in wind tunnel tests for the aerodynamic coefficients of iced hangers
Advances in Structural Engineering, 2019Co-Authors: Shengli Li, Dongwei WangAbstract:Wind attack angle increments are important inputs for the accurate and efficient wind tunnel test in analyzing the aerodynamic coefficients and Den Hartog galloping coefficients of iced cable struc...
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Influence of catwalk design parameters on the galloping of constructing main cables in long-span suspension bridges
Journal of Vibroengineering, 2017Co-Authors: Shengli Li, Chaoqun Wang, Yanan Hu, Dongwei WangAbstract:A main cable of a long-span suspension bridge is semi-surrounded by a catwalk during construction. Thus, design parameters of a catwalk may have influences on the galloping stability of a main cable during construction. To study the influence of catwalk design parameters on the galloping of steepled main cables, two main foci have been conducted. Firstly, the aerodynamic coefficients of the catwalk with actual design parameters are obtained by numerical simulation based on computational fluid dynamics (CFD), and the numerical results are compared with those of the previous wind tunnel test. Several typical main cables with different cross sections of a long-span suspension bridge during construction are selected, and their Den Hartog coefficients are obtained based on the numerical simulation considering the aerodynamic influences of the catwalks. Then four typical working conditions of a main cable which have great potential to occur galloping are selected based on the galloping analyze, and their aerodynamic coefficients considering the influence of the catwalk with different design parameters are obtained. The influence of the catwalk design parameters on galloping of the main cables is analyzed based on the Den Hartog criterion. Results indicate that catwalk design parameters have eviDent influences on aerodynamic coefficients and galloping of the main cables. The parameters of the catwalk which are favorable for suppressing the galloping of the main cables are determined, which establish a good guideline for the galloping-resistant design of the catwalk-main cable system on suspension bridges.
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Experimental and numerical studies on galloping of the flat-topped main cables for the long span suspension bridge during construction
Journal of Wind Engineering and Industrial Aerodynamics, 2017Co-Authors: Shengli Li, Yonghui An, Chaoqun Wang, Dongwei WangAbstract:Abstract The flat-topped main cables of the long span suspension bridge may occur galloping in the wind field during construction; however, little about galloping of the flat-topped main cables has been found in the existing literature; so it is important to address this problem. The present paper has two main parts, i.e. the numerical simulation and the wind tunnel test. In the first part, numerical simulation using the method of CFD (Computational Fluid Dynamics) is implemented to obtain the aerodynamic coefficients of six main cables with different cross sections at different wind attack angles from −5 to 5°. Then the corresponding Den Hartog coefficients of the six cables against the angle of attack are determined to predict the transverse galloping. Moreover, the Den Hartog coefficients of the six cables are compared with each other, and results show that generally the number of wind attack angles corresponded to negative Den Hartog coefficients presents a trend of increase with the progress of the construction. In the second part, models of three representative main cables are made by rigid plastics using the Three Dimension Printing Technology, and the aerodynamic coefficients of these cables are obtained by wind tunnel test; then the aerodynamic coefficients based on numerical simulation and wind tunnel test are compared together. It can be seen that the experimental results of the relationship of aerodynamic coefficients and the wind attack angles is close to the corresponding numerical results. As a result, the numerical simulation method in this paper can be used to study the galloping of main cables with different cross sections; moreover, the probability of the galloping occurrence increases with the progress of the construction. The present work lays a good foundation for safety alerts of the flat-topped main cables in construction.