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The problem of assessing the structure state following potential damage occur- rence by exploiting vibration signal measurements produced by earthquake excitation is ad- dressed. A damage assessment algorithm for structures under earthquake excitation is introduced. This method is based on a residual associated with output-only subspace-based modal...
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... proposed modal identification and detection methods of Sections 2 and 3 have proven useful in a number of application examples. However, the main source of dynamic excitation for structures in all these applications is ambient excitation. In order to test the validity of the proposed algorithm for processing the seismic signal, in this paper, the algorithm is applied to a real bridge, the Painter Street Overpass Bridge. The first reason for selecting the PSO Bridge for a case study was the availability of a rich data bank of previous earthquakes. The PSO Bridge is a two span, pre-stressed concrete box-girder bridge constructed in 1973 over the four-lane US Highway 101 in Rio Dell, Northern California. Its construction is typical of the type of California bridges used to span two or four lane highways, shown on Figure 1. The bridge is 15.85 m wide and 80.79 m long. The deck is a multi-cell box girder, 1.73 m thick and is supported on monolithic abutments at each end and two-pier bent that divides the bridge into two spans of unequal length; one of the spans is 44.51 m long and the other is 36.28 m long. The abutments and piers are supported by concrete friction piles and are skewed at an angle of 38.9 degrees. Longitudinal movement of the west abutment is allowed by means of a thermal expansion joint at the foundation level. The piers are about 7.32 m high, each supported by 20 concrete friction piles. The east and west abutments are supported by 14 and 16 piles, respectively. The bridge was instrumented in 1977 as a collaborative effort between the California Strong Motion Instrumentation Program of the Division of Mines and Geology and CALTRANS to record and study strong motion records from selected bridges in California. Twenty strong motion accelerometers were installed on the bridges as shown in Figure ...
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... The FRF was also plotted as spectrograms for an effective visualization of the dynamic behavior along the test sequence of each experimental session. According to recent literature [6], the FDD technique resulted very effective in system identification of civil structures under seismic excitation. It gives fast and reliable results even in the presence of non-stationary input with limited number of samples, i.e. short time excitation. ...
The present paper focuses on the use of a 3D motion capture system for the dynamic identification and the damage monitoring of a 1:10 scaled mock-up (representing the large historic masonry structure of Hagia Irene, Istanbul) tested on shaking table at the ENEA Casaccia Research Center located near Rome, Italy.
The dynamic identification of the structure during the shaking table tests was obtained by several techniques of Experimental Modal Analysis (EMA), such as FRF, FDD and EFDD. To such purpose Displacement Data Processing (DDP) of a large number of markers of the 3DVision (the passive 3D motion capture system installed at the ENEA laboratory) was performed. Markers were located on the tested mock-up accordingly to the indications of preliminary FEM analysis and modal shapes. Also conventional accelerometers were placed on the physical model and used as reference for the analysis of 3DVision data.
In addition, the analysis of Markers Relative Displacements (MRDs) was useful to detect the occurrence and development of fractures during the tests, contributing to assessing the actual progress of the structural damage. The results from EMA techniques and MRDs analysis of 3DVision data are illustrated, showing the potentialities of this monitoring system in integrating the two complementary approaches.
... The non-stationary nature and short duration of earthquake excitation pose another challenge to system identification of civil engineering structures [26,27]. Nonparametric methods are generally more efficient, but often less accurate than parametric methods. ...
SUMMARY Civil engineering structures are often subjected to multidirectional actions such as earthquake ground motion, which lead to complex structural responses. The contributions from the latter multidirectional actions to the response are highly coupled, leading to a MIMO system identification problem. Compared with single-input, multiple-output (SIMO) system identification, MIMO problems are more computationally complex and error prone. In this paper, a new system identification strategy is proposed for civil engineering structures with multiple inputs that induce strong coupling in the response. The proposed solution comprises converting the MIMO problem into separate SIMO problems, decoupling the outputs by extracting the contribution from the respective input signals to the outputs. To this end, a QR factorization-based decoupling method is employed, and its performance is examined. Three factors, which affect the accuracy of the decoupling result, including memory length, input correlation, and system damping, are investigated. Additionally, a system identification method that combines the autoregressive model with exogenous input (ARX) and the Eigensystem Realization Algorithm (ERA) is proposed. The associated extended modal amplitude coherence and modal phase collinearity are used to delineate the structural and noise modes in the fitted ARX model. The efficacy of the ARX-ERA method is then demonstrated through identification of the modal properties of a highway overcrossing bridge. Copyright © 2013 John Wiley & Sons, Ltd.
... Another approach based on System Realization using Information Matrix (SRIM) was proposed and applied to three long-span cable-supported bridges in Japan using seismic records (Siringoringo and Fujino, 2006). Subspace-based approaches were applied to a five-story steel frame using simulated earthquake responses from shaking table tests (Huang and Lin, 2001) and to a highway overpass bridge (Anderson et al., 2007). ...
Fragility functions are one of the key technical ingredients in seismic risk assessment. The derivation of fragility functions has been extensively studied in the past; however, large uncertainties still exist, mainly due to limited collaboration between the interdependent components involved in the course of fragility estimation. This research aims to develop a systematic Bayesian-based framework to estimate high-fidelity fragility functions by integrating monitoring, modeling, and hybrid simulation, with the final goal of improving the accuracy of seismic risk assessment to support both pre- and post-disaster decision-making. In particular, this research addresses the following five aspects of the problem: (1) monitoring with wireless smart sensor networks to facilitate efficient and accurate pre- and post-disaster data collection, (2) new modeling techniques including innovative system identification strategies and model updating to enable accurate structural modeling, (3) hybrid simulation as an advanced numerical-experimental simulation tool to generate highly realistic and accurate response data for structures subject to earthquakes, (4) Bayesian-updating as a systematic way of incorporating hybrid simulation data to generate composite fragility functions with higher fidelity, and 5) the implementation of an integrated fragility analysis approach as a part of a seismic risk assessment framework. This research not only delivers an extensible and scalable framework for high-fidelity fragility analysis and reliable seismic risk assessment, but also provides advances in wireless smart sensor networks, system identification, and pseudo-dynamic testing in civil engineering applications.
This paper presents a simple method for preliminary structural assessment of bridges located in the province of British Columbia,
Canada, using ambient vibration testing. The method is applied to bridges that have been hit by trucks or showed deterioration
in some elements caused by bad construction and aging. The Earthquake Engineering Research Facility at The University of British
Columbia, UBC-EERF, carried out a testing campaign of these bridges in December 2008. The bridges were tested along the deck
taking measurements at 100 locations approximately. The damage criteria was based on identification of modal properties (mode
shapes, frequencies and damping) and evaluation of maximum vertical displacements of the deck under normal traffic load conditions.
The results show that the proposed approach can be used for preliminary evaluation of the structural integrity of the type
of bridges investigated.
