Search

Resonance of multi-degree-of-freedom system or structure is a basic and important concept in structural vibration theory, but it lacks a complete and rigorous definition. In order to establish an accurate concept of structural resonance, based on the concept of single-degree-of-freedom system resonance and modal orthogonality, this paper discusses the necessary conditions of system resonance by analyzing the displacement response of multi-degree-of-freedom vibration system, that is, while ensuring that the vibration frequency of the system (a certain natural frequency) is equal to the excitation frequency, its displacement response should also present the corresponding modal shape. An example of simply supported beam is used to illustrate its rationality. At the same time, the theoretical method of pure modal resonance of multi-degree-of-freedom system is given by rational allocation of excitation force. The pure modal resonance of multi-degree-of-freedom system or structure can be realized, which can be used to accurately identify the modal parameters of the structure. It is of great theoretical significance and engineering application value to discriminate the concept of multi-degree-of-freedom system or structure resonance. [ABSTRACT FROM AUTHOR]

This study established the transfer laws of vibration waves in a linear system under simple harmonic loading. Then, a method based on multipoint delivery in the frequency domain was proposed to predict the vibrations of historical timber buildings induced by traffic loads, in which the transfer function between two delivery points of different single frequencies is obtained. Finally, the vibration responses of the Feiyun pavilion induced by traffic loads were predicted and compared with experimental field test results. The results indicate that the predicted vibration responses and experimental field tests at the measurement point in the Feiyun pavilion correspond well in the concerned frequency bands and that the proposed prediction method can be used to predict the structural vibration responses under the influence of complex traffic loads. [ABSTRACT FROM AUTHOR]

Vibrational power flow contains two types of information, namely, vibration velocity and structural internal force, and is an important parameter for measuring vibration level and transmission. Structures are often under stress because of the working environment. This stress changes the vibration velocity and internal force of the structure. As a result, this stress affects the power flow. In practical engineering, structural stress often has a complex distribution. However, earlier studies mainly focused on the overall uniformly distributed stress, which cannot be applied to practical engineering vibration problems. The finite element method can handle this problem, but has several shortcomings, such as the lack of a clear explanation of the essential relationship between structural stress and vibration, the complicated process of applying specific stress, and the large number of calculations. This study considers the effect of general structural stress and determines the dynamic equation of a structure undergoing stress. By utilizing the orthogonality of specific order modes to decouple, we obtain the power flow analytical solution, which can be applied to structures with arbitrary distributed stress. Finally, we calculate and analyze the effect of structural stress on a welding plate. Results show that structural stress has a more significant effect on power flow than velocity and inner force and should be taken into account when considering vibration prediction and reduction in practical engineering. [ABSTRACT FROM AUTHOR]

In recent years, several solutions for structural vibration control of buildings have been proposed. In particular, the combination of base-isolated structures with complementary variable damping devices has been successful in reducing the base isolator displacements without increasing the building superstructure response when subjected to earthquake loads. In this paper, a magnetorheological device is installed on a 2-DOF mechanical model mounted on an experimental uniaxial shaking table. A simple numerical simulation model is derived for the experimental setup and it represents a typical base-isolated structure with a semi-active vibration controller. The control law combines a force tracking integral action with a clipped on–off adaptation rule that changes the magnetorheological damping in real time. The effectiveness of the proposed solution is demonstrated for both earthquake-like and real earthquake input ground motions. A comparison between the numerical and the experimental results validates the numerical simulations and it gives confidence in using this model for validation and evaluation of other semi-active control solutions based on magnetorheological dampers. [ABSTRACT FROM AUTHOR]

The active control of vibro-acoustic response using sound pressure feedback is numerically studied. An output feedback approach based on sound pressure measurement for modal pole placement is proposed. The control performance is evaluated for the case of a baffled plate. The finite element method and the Rayleigh integral are used to model the structural vibration and sound radiation. Measures of observability of a mode in pressure outputs and the effect of time delay in the pressure feedback loop are discussed. Numerical results show that the chosen poles may be assigned to predetermined values by the active control with complex gains. It is also demonstrated that the pressure feedback control may make a very large reduction in acoustic radiation and structural vibration of the controlled modes in a wide frequency band when using constant gain at a lower frequency. [ABSTRACT FROM AUTHOR]