Effect of identification on seismic performance assessment of a tall building

In this study, a twenty-six story, core-wall tall building was instrumented with data acquisition system. Modal parameters were obtained by using Enhanced Frequency Domain Decomposition (EFFD) method and a detailed FEM of the structure was updated based on the identified modal characteristics in order to represent the actual dynamic characteristics of the building. Updating of a fine FEM allows to minimize the uncertainties in structural parameters such as the effects of soil springs and seismic gaps with frictional plates which are usually omitted in updating procedures. Along this line, nonlinear time history (NLTH) analyses were performed with the updated and the non-updated FEM with 5% damping ratio. Additionally, NLTH analyses were carried out with updated FEM considering the identified (2%) and 5% damping ratios in order to observe the effect of damping ratio separately. Probability density functions in terms of interstory drift ratios were established in order to quantify the probability of failures under different ground motions. Results highlight that incorporation of system identification and model updating techniques into seismic performance assessment is crucial. Results also show the significant sensitivity of higher modes to the changes in structural parameters during updating procedure of tall buildings and excitation of higher modes due to seismic motions. In addition, recorded seismic response of the building demonstrated the dynamic excitation (vibration amplitude) of higher modes may be higher than the one of fundamental mode.