Damage identification study of a seven-story full-scale building slice tested on the UCSD-NEES shake table

Abstract

A full-scale seven-story reinforced concrete building section was tested on the UCSD-NEES shake table during the period October 2005 -January 2006. The shake table tests were designed to damage the building progressively through four historical earthquake records. At various levels of damage, ambient vibration tests and low amplitude white noise base excitations with root-mean-square accelerations of 0.03g and 0.05g were applied to the building, which responded as a quasi-linear system with parameters evolving as a function of structural damage.Modal parameters (natural frequencies, damping ratios and mode shapes) of the building were identified at different damage levels based on the response of the building to ambient as well as low amplitude white noise base excitations, measured using DC coupled accelerometers. This paper focuses on damage identification of this building based on changes in identified modal parameters. A sensitivity-based finite element model updating strategy is used to detect, localize and quantify damage at each damage state considered. Three sets of damage identification results 1. Corresponding author. Tel.: +1 858-822-4545; fax: +1 858-822-2260. E-mail address: jpconte@ucsd.edu 2 are obtained using modal parameters identified based on ambient, 0.03g, and 0.05g RMS white noise test data, respectively. The damage identification results obtained in all three cases do not exactly coincide, but they are consistent with the concentration of structural damage observed at the bottom two stories of the building. The difference in the identified damage results is mainly due to the significant difference in the identified modal parameters used in the three cases. The assumption of a quasi-linear dynamic system is progressively violated with increasing level of excitation. Therefore, application of nonlinear FE model updating strategies is recommended in future studies to resolve the errors caused by structural response nonlinearity.

Parameter Estimation of Nonlinear Large Scale Systems Through Stochastic Methods and Measurement of Its Dynamic Response

“…Specifically, the two measures of fit are given by experimentally identified and estimated mode shapes for the r -th mode. Alternative measures of fit can easily be used and found in literature [18][19][20][21][22].…”

Finite-Element Model Updating for Assessment of Progressive Damage in a 3-Story Infilled RC Frame

“…Outputonly system identification methods, which have been successfully applied for system identification of linear systems (He et al 2009;Moaveni et al 2011), are based on the assumption of a broadband (ideal white-noise) input excitation. However, in this set of experiments, the white-noise base excitation inputs were significantly modified by the shake table system dynamics, and consequently, the table motions did not satisfy the broadband assumption as illustrated in Fig.…”

“…Furthermore, actual construction practices often cannot be reproduced in small-/medium-scale test specimens. The few instances of successful application of FE model updating methods for the condition assessment of large-scale structures include the damage identification studies on the Z24 Bridge in Switzerland (Teughels and De Roeck 2004), the use of dynamic strain measurements from fiber optic sensors for FE model updating of the Tilff Bridge (Reynders et al 2007), the use of a neural network method based on modal frequencies and a validated FE model to identify the stiffness reduction in a one-third-scaled one-story concrete frame (Zhou et al 2007), and FE model updating based on identified modal properties of a full-scale composite beam (Moaveni et al 2008) and a full-scale seven-story RC shear wall building slice (Moaveni et al 2010).…”

Variability of updated finite element models and their predictions consistent with vibration measurements

“…For the second group, the measure of fit I 2 ðyÞ is selected to represent the difference between the measured and the model predicted mode shape components for all modes. Specifically, the two measures of fit are given by Alternative measures of fit [3,[19][20][21][22] can easily be accommodated in the proposed formulation. In particular, it is straightforward to show that…”

“…This case study demonstrates that unidentifiability issues arise in updating FE models with a large number of DOFs, build for realistic structures and using real measurements. As it is noted in Figure 8(a), the unidentifiable solutions corresponding to the flat horizontal portion (points [12][13][14][15][16][17][18][19][20] in the objective space and the associated manifold in Figure 8(b) are readily estimated by the NBI method. From the engineering point of view, the most important point from this flat portion is the most left point 12 in Figure 8(a) since all other points in the flat portion deteriorate the fit in the objective function J 1 ðyÞ without altering the fit in J 2 ðyÞ.…”