Research On Damage Detection Of Structure Based On Operational Strain Mode

The structure health monitoring technology has concerned in civil engineering field. Modal analysis is a great important method of damage detection.With the research and application going in deep, wireless sensor technology is going to be one of the popular research directions in expanding the application range of the structure health monitoring system.The key issues of structure health monitoring using operational strain mode,mainly including the fields of modal parameter identification and wireless sensor networks,are studied via theoretical derivation, modeling simulation and experimental research in this thesis.Some beneficial explorations are putted forward for real time monitoring of large constructions.Main contents are as follows:Firstly,the modal parameters identification of operational strain modes is carefully deduced with the frequency domain method based on the theory of strain mode and frequency response function.According to the peaks on frequency-amplitude characteristic curves, the natural frequencies are identified.Then, according to the ratio of strain response magnitude at the measurement point to that at the reference point,the amplitudes of operational strain mode shapes are obtained.The phases are defined by the sign of cross-spectral real part.Secondly,3D models of steel beams are built with different degree damage by the general finite element analysis software ANSYS to extract the strain mode value.The relationship between strain mode and damage is obtained by using Matlab.Thirdly,modal analysis experiments are carried out on the steel beams with preset damage under environmental excitation by using strain gauge.In the experiment, the wireless sensor technology is used to obtain the strain data of steel beams in real time.Finally,analyzing the experimental data by DHMA software to obtain the operational strain modes of steel beams.Further analysis of modal parameters is obtained with Matlab，and the relationship between strain mode and damage of simply supported beam is deduced.The research results show that operational strain mode has a good application prospect in structural damage identification.