Modal Identification and Damage Detection for Structural Health Monitoring under Ambient Vibration Environment

In this paper, a new health monitoring strategy has been suggested integrating NExT/ERA technique with a model based damage identification method. It consists of four major steps: 1) measurements of ambient vibration response; 2) modal identification using output-only techniques NExT/ERA in time domain; 3) damage localization using a new parameter subset selection method; 4) damage quantification formulated into optimization problems. Additionally, to distinguish physical true modes from non-physical comutational modes in the NExT/ERA technique, an improved consistency indicator that is better consistent in a wide range of damping ratios has been suggested through investigative parametric studies. A finite element model of a truss bridge structure has been built for numerical case studies. A series of numerical case studies with four different damage scenarios have been conducted under ambient vibration. Finally, the proposed methodology has shown potentials for either of damage diagnosis or finite model updating for model-based condition assessment of the remaining structural life.