This paper summarizes the analytical and experimental dynamic analyses carried out to assess the actual dynamic behaviour of a curved cable-stayed bridge,recently erected in the commercial harbour of Porto Marghera ( ...This paper summarizes the analytical and experimental dynamic analyses carried out to assess the actual dynamic behaviour of a curved cable-stayed bridge,recently erected in the commercial harbour of Porto Marghera ( Venice,Italy). Ambient vibration tests were carried out to determine the dynamic characteristics of the bridge and more than 20 modes were identified in the frequency range 0～10Hz. In the theoretical study,a 3D FE model of the bridge was developed using an integrated CAD-FEA approach; subsequently,the information obtained from the field tests,combined with simple manual tuning,provided a linear elastic model,accurately fitting the modal parameters of the bridge in its present condition.展开更多
The effect of tire repeated root modal（RRM）on tire modeling with an experimental modal is studied.Firstly,a radial tire with radial and tangential RRMs is tested and analyzed.By multi-point exciting of the radial ti...The effect of tire repeated root modal（RRM）on tire modeling with an experimental modal is studied.Firstly,a radial tire with radial and tangential RRMs is tested and analyzed.By multi-point exciting of the radial tire,a multiple reference frequency domain method based on a least squares（LMS PolyMAX）algorithm is used to identify modal parameters.Then,modal stability diagram（MSD）,modal indication function（MIF）and modal assurance criteria（Auto-MAC）matrix are utilized to induce multiple inputs multiple outputs（MIMO）frequency response function（FRF）matrixes.The tests reveal that notable repeated roots exist in both radial and tangential response modes.Their modal frequencies and damping factors are approximately the same,the amplitudes of modal vectors are in the same order of magnitude,and the mode shapes are orthogonal.Based on the works mentioned,the method of trigonometric series modal shapes fitting is adopted,the effects of RRM model on tire modeling with a vertical experimental modal are discussed.The final results show that the effects of considering the RRM shapes are equivalent to the tire mode shapes depended on rotating the tire’s different exciting points during tire modeling,and since considering the RRM,the tire mode shapes can be unified and fixed during tire modeling.展开更多
The dipole magnet of the China Spallation Neutron Source(CSNS) Rapid-cycling Synchrotron(RCS) will be operated at a 25 Hz sinusoidal alternating current which causes severe vibration.The vibration will influence the l...The dipole magnet of the China Spallation Neutron Source(CSNS) Rapid-cycling Synchrotron(RCS) will be operated at a 25 Hz sinusoidal alternating current which causes severe vibration.The vibration will influence the long-term safety and reliable operation of the dipole magnet.By taking the dipole magnet and magnetic measurement girder as specific model system,a method for analyzing and studying the dynamic characteristic of the system is put forward by combining theoretical calculation with experimental testing.This paper established the mechanical model of the system,and the top six step natural frequency and vibration mode were obtained through theoretical modal analysis(ANSYS).Then according to testing modal analysis,the natural frequency,damping ratios and vibration mode of the system structure were obtained too.The theoretical modal analysis results coincide with the experimental testing results.Besides,the 6th step natural frequency is close to the exciting frequency of the magnet,so the resonance phenomenon may take place at the actual working conditions.The dynamic characteristic data of the structure can provide an analysis basis for the further study and the formal dipole magnet girder optimal design of RCS.展开更多
基金support provided by the Italian Ministry of University and Research,under the grant PRIN 2006
文摘This paper summarizes the analytical and experimental dynamic analyses carried out to assess the actual dynamic behaviour of a curved cable-stayed bridge,recently erected in the commercial harbour of Porto Marghera ( Venice,Italy). Ambient vibration tests were carried out to determine the dynamic characteristics of the bridge and more than 20 modes were identified in the frequency range 0～10Hz. In the theoretical study,a 3D FE model of the bridge was developed using an integrated CAD-FEA approach; subsequently,the information obtained from the field tests,combined with simple manual tuning,provided a linear elastic model,accurately fitting the modal parameters of the bridge in its present condition.
文摘The effect of tire repeated root modal（RRM）on tire modeling with an experimental modal is studied.Firstly,a radial tire with radial and tangential RRMs is tested and analyzed.By multi-point exciting of the radial tire,a multiple reference frequency domain method based on a least squares（LMS PolyMAX）algorithm is used to identify modal parameters.Then,modal stability diagram（MSD）,modal indication function（MIF）and modal assurance criteria（Auto-MAC）matrix are utilized to induce multiple inputs multiple outputs（MIMO）frequency response function（FRF）matrixes.The tests reveal that notable repeated roots exist in both radial and tangential response modes.Their modal frequencies and damping factors are approximately the same,the amplitudes of modal vectors are in the same order of magnitude,and the mode shapes are orthogonal.Based on the works mentioned,the method of trigonometric series modal shapes fitting is adopted,the effects of RRM model on tire modeling with a vertical experimental modal are discussed.The final results show that the effects of considering the RRM shapes are equivalent to the tire mode shapes depended on rotating the tire’s different exciting points during tire modeling,and since considering the RRM,the tire mode shapes can be unified and fixed during tire modeling.
文摘The dipole magnet of the China Spallation Neutron Source(CSNS) Rapid-cycling Synchrotron(RCS) will be operated at a 25 Hz sinusoidal alternating current which causes severe vibration.The vibration will influence the long-term safety and reliable operation of the dipole magnet.By taking the dipole magnet and magnetic measurement girder as specific model system,a method for analyzing and studying the dynamic characteristic of the system is put forward by combining theoretical calculation with experimental testing.This paper established the mechanical model of the system,and the top six step natural frequency and vibration mode were obtained through theoretical modal analysis(ANSYS).Then according to testing modal analysis,the natural frequency,damping ratios and vibration mode of the system structure were obtained too.The theoretical modal analysis results coincide with the experimental testing results.Besides,the 6th step natural frequency is close to the exciting frequency of the magnet,so the resonance phenomenon may take place at the actual working conditions.The dynamic characteristic data of the structure can provide an analysis basis for the further study and the formal dipole magnet girder optimal design of RCS.
