Rapid evaluation and damage assessment of instrumented structures

This work focuses on the use of strong motion data recorded during earthquakes and aftershocks to provide a preliminary assessment of the structural integrity and possible damage in structures. A system identification technique is used to determine dynamical characteristics and high-fidelity first-order linear models of a structure from low level earthquake excitations. Finite element (FE) models are developed and updated using a genetic algorithm optimization scheme to match the frequencies and mode shapes identified. In the case that records from strong excitations are not available, the FE model is also updated to simulate data from a damaging earthquake for the structure. A wavelet analysis is used to track instantaneous frequencies obtained from the local maxima of the wavelet coefficients. Three criteria are used to determine the state of the structure. The first criteria uses the error between data recorded or simulated by the calibrated nonlinear FE model and data predicted by the first-order linear model. The second criteria compares relative displacements of the structure with displacements thresholds identified using a pushover analysis and the third criteria detects damage by identifying changes in the fundamental frequency of the structure using a wavelet analysis. The use of this technique can provide an almost immediate, yet reliable, assessment of the structural health of an instrumented structure after a seismic event.