Vibration acceleration method is employed to measure the vibration frequency, damping ratio, shape of amplitude, acceleration, velocity and displacement at different point of the pipe bridge structures, and parameters relating to vibration displacement and tension of staying cables of the pipe bridge in different conditions of bridge cleaning.

Experiments demonstrate that it is practical to detect the foundation compactedness in real time by measuring the change of the damping ratio of the soil.

③ Frequency ratio of TMD to bridge and damping ratio of TMD have both effects on the control effectiveness,and the effect of the former is greater than that of the latter.

A universal estimation approach has been configured to depict the relationship among the equivalent modal damping ratio, RMS cable deflection, the optimal parameter of MR dampers (marker, mounting position and voltage applied), the first frequency of cables (tensile force, length and mass per unit length), Irvine parameter, excited loads (type, frequency and amount).

Secondly, it analyzes the parameters of Bu-Liu River Bridge’s coupling vibration of vehicle-bridge, which include some influencing factors such as vehicle speed、vehicle quality、its type and damping ratio、bridge’s damping ratio and so on.

The structural modal damping ratio is calculated using the modal strain energy method in conjunction with the finite element method. The dynamic response of vehicle bridge system with and without viscoelastic damper is performed by computer. The simulating results preliminary show: It is effective that using the suggested method to reduce the short or middle span steel bridge displacement out of limited causing by velocity increasing.

The damping will be defined by the shear damping ratio for the soil D, analogous to the critical viscous damping ratio for a single degree of freedom c/c0.

Thus, only two tests would be necessary in order to obtain both the maximum damping ratio, introduced by the piezo device, and the natural frequency of the whole system.

Therefore, several tests (experimental or numerical) ought to be carried out in order to determine the resistor which provides the maximum damping ratio for a mode of interest, and in turn the natural frequency of the whole structure.

A damping ratio of less than 0.05 percent of critical damping is proved to be valid for the aluminum panel.

The modal damping ratio is improved from below 0.2 percent to above 4 percent.

This report presents the procedure and main results of in situ vibration test on Xinfengjiang Dam. The first ten natural frequencies, damping ratios and mode shapes of the dam were measured through steady forced vibration test using multiple vibrators. It was shown from the test that deformation of the dam was in linear elastic state and the dam under forced vibration might be considered as a monolithic body; the first ten frequencies ranged from 5.5 to 16.0 c/s; and the average damping ratio of...

This report presents the procedure and main results of in situ vibration test on Xinfengjiang Dam. The first ten natural frequencies, damping ratios and mode shapes of the dam were measured through steady forced vibration test using multiple vibrators. It was shown from the test that deformation of the dam was in linear elastic state and the dam under forced vibration might be considered as a monolithic body; the first ten frequencies ranged from 5.5 to 16.0 c/s; and the average damping ratio of the dam was about 0.05. Moreover, the effects of various exciting points were compared in this report also.

The main teaching building of Northeast Forestry University was built in 1956 and came into use. By our observation, so far,the building is working well. The main building has been bnilt for 30 years, nevertheless, its dynamic property parameters——natural frequency,normal modes,damping are unknown yet.We carried out a study on its dynamic property parameter with a surrounding random excitation;here, its (1st)natural frequency,(1st) normal modes and damping ratio are given in this paper. We find its account...

The main teaching building of Northeast Forestry University was built in 1956 and came into use. By our observation, so far,the building is working well. The main building has been bnilt for 30 years, nevertheless, its dynamic property parameters——natural frequency,normal modes,damping are unknown yet.We carried out a study on its dynamic property parameter with a surrounding random excitation;here, its (1st)natural frequency,(1st) normal modes and damping ratio are given in this paper. We find its account as a reference in the maintenance and use of the main building preventing it from the seisin damage and its life-span estimation.

A method, which uses the damping ratios and frequency of freedecaying oscillations as basic information to identify the flutter derivatives of a two dimensional bridge deck, is proposed. In this method, noncoupled flutter derivatives are identified by the Scanlan's method, while the coupled ones are determined by solving a system of nonlinear equations and using the parameters of the predominant modes for a given reduced wind speed. Compared with Scanlan's method in current use, the proposed method not...

A method, which uses the damping ratios and frequency of freedecaying oscillations as basic information to identify the flutter derivatives of a two dimensional bridge deck, is proposed. In this method, noncoupled flutter derivatives are identified by the Scanlan's method, while the coupled ones are determined by solving a system of nonlinear equations and using the parameters of the predominant modes for a given reduced wind speed. Compared with Scanlan's method in current use, the proposed method not only reduces the technical requirements to the wind tunnel tests, but also increases the accuracy of the identification.