Experimental Research On Dynamic Testing And Vibration Analysis For Beam

The purpose of this dissertation is to solve the problems associated with dynamic performance of the system and its application. This study can be summarized as two parts: system simulation and system tests. The former part is mainly concerned with theoretical research. The latter part is mainly concerned with the experimentation. Two aspects are all discussed in the dissertation. Dynamic tests were carried out on simple supported reinforced concrete (RC) members. The main works of the dissertation are presented as follows:The main features of flexural stiffness function were speculated as basic facts to support theoretical research and practical application. Then using Euler-Bernoulli beam model, the response result was analyzed which of simply supported beam was subjected to impulse load. Then compared numerical result and accurate solution, respective influences were obtained clearly. How select the parameters was given proposal.The discrete Fourier transform (DFT) was deduced from the Fourier series expression. And then the physical significance of DFT was explained clearly and completely. When the signal spectrum is calculated using the type of DFT expression, the spectral coefficients and the frequency domain coordinates need be adjusted correspondingly only. The symmetrical property of the spectrum was described in principle. Key spectral lines would not be missed generally in according to the general number N/2be considered as effective spectral lines. But the understanding of the related issues is likely to be affected. Such as the quantity relations might be confused in the process of calculation in frequency domain. Base on the discussion of DFT, the improved method that would visually extract the frequency as better peak of the spectrum, zoom spectrum analysis, was further discussed here. While it was discovered that a single frequency harmonic zoom spectrum and a rectangle window spectrum was very similar. Based on this law, the digital signal included several close frequency harmonics can be identified. Furthermore, Harmonic parameters can be extracted from the most close frequency digital signal.Based on the identification of frequency and the initial phase using zoom spectral analysis and the important properties of the DFT. Discrete convolution and deconvolution principle, a new method was proposed for identifying the damping from free decay response (FDR) without dependency on a prior knowledge of damping model. The time sequence can be identified by discrete deconvolution technique which can be employed to reflect the changes of harmonic amplitude.Dynamic tests on RC composite beam have been performed to identify the system parameters using these measurements. The influences of test conditions were discussed. And the laws of dynamic testing techniques and the structural dynamic performance were summed up.