DYNAMIC PROPERTIES OF A FULL-SCALE BUILDING TESTED ON A SHAKE TABLE: FROM CONSTRUCTION TO INCIPIENT COLLAPSE

This paper discusses the system identification of a full-scale 5-story reinforced concrete building tested on the unidirectional NHERI-UCSD shake table. The purpose of the test program, carried out in 2012, was to study the seismic response of the structure and nonstructural components and systems (NCSs) and their dynamic interaction at different levels of seismic excitation. The building specimen was tested under base-isolated (BI) and fixed-base (FB) configurations. Sequences of seismic tests of different intensities were performed for both base configurations of the building and were complemented with ambient vibration, impact/free vibration, and low amplitude white noise base excitation tests and detailed visual inspections of structural and nonstructural damage before and after each seismic test. Vibration data were collected and modal parameters of the test specimen were identified using input-output and output-only methods. Time-variant modal properties of the building during seismic tests were also identified by using an input-only methodology. The results show that the modal properties obtained by different methods are in good agreement. Moreover, the effects of nonstructural components, amplitude of excitation, nonlinear response of the isolation system, and structural/nonstructural damage progression can be related to changes in the estimated modal parameters of the building.