Structural damage detection from experimental modal data

Abstract

In this dissertation, two damage detection approaches are developed to localize and quantify structural damage. Both approaches make use of experimental modal data, such as modal frequency and mode shape, correlated with the corresponding parameters of the finite element model to form the damage indicators to localize structural damage sites first and then to quantify the damage extent. The main objective of this dissertation research is to develop techniques on damage localization. The first approach of damage detection is developed from the elemental modal strain energy by using the complete mode shapes. The contributions in this research are: 1. To present a damage localization approach using the elemental modal strain energy change ratio. 2. To develop two damage quantification algorithms also using the elemental modal strain energy change. 3. To complete an eigenvector expansion method using the projection technique and a minimization approach. Another approach is to use minimal sensor information (incomplete mode shape) without any mode shape expansion to localize structural damage. The placements of the sensors are prioritized and selected based on their ability to collect damage information. Contributions in this research are: 1. To develop a damage localization algorithm by a sensitivity and statistical-based method using the incomplete mode shapes. 2. To present a sensor placement optimization approach incorporated with the damage location method. To gain insight into the features of the two proposed methods, numerical examples have been studied to show the ability of detecting various damages in different structures. Apart from numerical examples, an experiment on a three-dimensional eight-bay frame structure is also carried out. Various damage cases have been studied to verify the proposed methods under the real situation. The proposed methods have been found to be successful in localizing the damage with either one or more damages in the structure. The implementation process and results of the verification studies are also included in this thesis.