System identification of two large-scale bridges before and after seismic testing using target-Tracking digital image correlation

This paper presents recent research activities conducted in the Earthquake Engineering Laboratory of University of Nevada, Reno in the field of dynamic monitoring and system identification of two-span concrete and steel bridges. A 3D target tracking didigtal image correlation (DIC) system was used for monitoring and DIC data was used for the system identification presented in this paper. Two 1/3-scale bridges were tested under several intenisty levels of earthquake loading using multiple shake tables. Before and after each seismic test, low amplitude white noise base excitation tests were conducted. A quasi-linear response of the system was assumed because of the low intensity of the white noise base excitations, and the structural modal parameters were estimated accordingly. Using the target-Tracking DIC measured response, FFT and SSI identification methods were used to estimate and compare the eigenfrequency, damping ratio and mode shape of the bridges before and after the seismic tests.