System identification of a full-scale five-story reinforced concrete building tested on the NEES-UCSD shake table

This paper presents the identification of modal properties of a full-scale five-story reinforced concrete building fully outfitted with nonstructural components and systems (NCSs) tested on the NEES-UCSD shake table. The fixed base building is subjected to a sequence of earthquake motions selected to progressively damage the structure and NCSs. Between seismic tests, ambient vibration response is recorded. Additionally, low-amplitude white noise (WN) base excitation tests are conducted during the test protocol. Using the vibration data recorded, five state-of-the-art system identification (SID) methods are employed, including three output-only and two input-output. These methods are used to estimate the modal properties of an equivalent viscously-damped linear elastic time-invariant model of the building at different levels of damage and their results compared. The results show that modal properties identified from different methods are in good agreement and that the estimated modal parameters are affected by the amplitude of excitation and structural/nonstructural damage. Detailed visual inspections of damage performed between the seismic tests permit correlation of the identified modal parameters with the actual damage. The identified natural frequencies are used to determine the progressive loss of apparent global stiffness of the building, and the state-space models identified using WN test data are employed to investigate the relative modal contributions to the measured building response at different damage states. This research provides a unique opportunity to investigate the performance of different SID methods when applied to vibration data recorded in a real building subjected to progressive damage induced by a realistic source of dynamic excitation. Copyright (c) 2015 John Wiley & Sons, Ltd.