Strain Modal Analysis And Parameter Identification

Strain(curvature) modal parameters are more sensitive than displacement modal parameters to the changes of local characteristics in the structure, such as local strain, local structural damage. Therefore it will be more accurate to locate damage based on the change of strain(curvature) mode. The key of structural damage detection and health monitoring is how to obtain strain modal parameters directly from strain response. The paper presents theoretical and experimental study on experimental strain modal analysis and parameters detection. Strain modal parameters of the test beam are identified by both frequency-domain method and time-domain method. The result can be used in structural damage detection, finite element model updating and structural health monitoring. It has great theoretical and practical value.The main content includes:1. The modal model of strain response(strain frequency response function) is deduced, then the orthogonality of strain modal shape is testified and the frequency-domain strain modal identification method is introduced.2. A novel strain multiplier is designed which makes it feasible to apply the strain modal analysis theory in practical bridge.3. The first two order displacement modal parameters and strain modal parameters of the test beam are extracted based on stain modal experiment, and the results are compared with the theoretical solution, the validity of the frequency-domain stain modal identification method used in this paper is verified.4. The stochastic subspace identification method of strain modal identification is introduced and the first two order strain modal parameters of the test beam obtained are compared with the theoretical solution and the frequency-domain identification results. The results show that the stochastic subspace identification method can identify the structural strain modal parameters with good accuracy.