Influence of the construction process and nonstructural components on the modal properties of a five‐story building

Struct. Control Health Monit.

Ebrahimian

Conte

et al. 2015

Self Cite

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-ofthe-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. frequencies, damping ratios, and mode shapes) from recorded structural vibration data. A comprehensive and detailed literature review on vibration-based DID can be found in [1] and [2].Most vibration-based DID studies have been conducted using idealized theoretical models and numerically simulated data, or using experimental data from small-scale tests of single structural components, subassemblies, and systems (e.g. [3][4][5]). Only a few studies have used experimental data obtained from real structures or large-scale shake table tests. Most full-scale damage-controlled tests have been conducted on bridge structures [6][7][8][9][10][11] by progressively inducing artificial damage (e.g. partial saw cuts in steel beams and/or partial cuts of post-tensioning tendons).Building structures are even more complex than bridges. Several factors hinder robust vibrationbased DID studies for building structures: (i) the impossibility to perform progressive damage tests on existing non-decommissioned structures; (ii) the high risk and complexity to conduct such tests on decommissioned structures; (iii) and the scarcity of recorded dynamic response of earthquakedamaged buildings. This lack of data has been somewhat addressed by shake table tests that have provided importan...

Section: System Identification Resultssupporting

confidence: 93%

“…This observation confirms the amplitude‐dependent characteristic of identified damping ratios observed in other studies (e.g. ,).…”

Section: System Identification Resultssupporting

confidence: 92%

Section: System Identification Resultsmentioning

confidence: 99%

Section: Damage Statesmentioning

confidence: 99%

See 2 more Smart Citations

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

Struct. Control Health Monit.

Ebrahimian

Conte

et al. 2015

Self Cite

“…Among the NCSs installed in the building were partition walls laid out in various configurations on each floor, and an exterior façade composed of cold formed steel studs overlaid with gypsum board and finishing, which spanned from the bottom of the first floor to the top of the third floor. These NCSs provided additional stiffness to the building [25] because of the connection points spanning vertically between floors and were anticipated to contribute to the system energy dissipation. A dense network of sensors, including accelerometers, a global positioning system (GPS), load cells, linear and string potentiometers, and strain gauges, was installed throughout the building to monitor the structural response.…”

Section: Building Description and Test Programmentioning

confidence: 99%

Predominant period and equivalent viscous damping ratio identification for a full‐scale building shake table test

Chen

Earthq Engng Struct Dyn

Restrepo

et al. 2017

Self Cite

Summary The predominant period and corresponding equivalent viscous damping ratio, also known in various loading codes as effective period and effective damping coefficient, are two important parameters employed in the seismic design of base‐isolated and conventional building structures. Accurate determination of these two parameters can reduce the uncertainty in the computation of lateral displacement demands and interstory drifts for a given seismic design spectrum. This paper estimates these two parameters from data sets recorded from a full‐scale five‐story reinforced concrete building subjected to seismic base excitations of various intensities in base‐isolated and fixed‐base configurations on the outdoor shake table at the University of California, San Diego. The scope of this paper includes all test motions in which the yielding of the reinforcement has not occurred and the response can still be considered ‘elastic’. The data sets are used with three system identification methods to determine the predominant period of response for each of the test configurations. One of the methods also determines the equivalent viscous damping ratio corresponding to the predominant period. It was found that the predominant period of the fixed‐base building lengthened from 0.52 to 1.30 s. This corresponded to a significant reduction in effective system stiffness to about 16% of the original stiffness. The paper then establishes a correlation between predominant period and peak ground velocity. Finally, the predominant periods and equivalent viscous damping ratios recommended by the ASCE 7‐10 loading standard are compared with those determined from the test building. Copyright © 2017 John Wiley & Sons, Ltd.

Influence of the construction process and nonstructural components on the modal properties of a five‐story building

Earthq Engng Struct Dyn

Ebrahimian

Conte

et al. 2016

Self Cite

Summary A full‐scale five‐story reinforced concrete building was built and tested on the NEES‐UCSD shake table during the period from May 2011 to May 2012. The purpose of this test program was to study the response of the structure and nonstructural components and systems (NCSs) and their dynamic interaction during seismic base excitation of different intensities. The building specimen was tested first under a base‐isolated condition and then under a fixed‐based condition. As the building was being erected, an accelerometer array was deployed on the specimen to study the evolution of its modal parameters during the construction process and placement of major NCSs. A sequence of dynamic tests, including daily ambient vibration, shock (free vibration) and forced vibration tests (low‐amplitude white noise and seismic base excitations), were performed on the building at different stages of construction. Different state‐of‐the‐art system identification methods, including three output‐only and two input‐output methods, were used to estimate the modal properties of the building. The obtained results allow to investigate in detail the effects of the construction process and NCSs on the dynamic parameters of this building system and to compare the modal properties obtained from different methods, as well as the performance of these methods. Copyright © 2015 John Wiley & Sons, Ltd.