Seismic Damage Detection of a Full-Scale Shaking Table Test Structure

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.

Section: Introductionmentioning

confidence: 99%

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

Chen

Astroza

Restrepo

et al. 2017

“…Using measured vibration responses, various damage detection methods to date have been proposed, such as modal parameter-based method [3], interstory drift ratio-based method [4], seismic wave propagation method [5], and time series analysis method [6]. For example, through a series of shaking table testing in which various levels of realistic seismic damage were reproduced for a high-rise steel building specimen at the E-Defense facility in Japan, Ji et al [9] demonstrated that the natural frequencies of the specimen decreased by 4.1%, 5.4%, and 11.9% on average for three damage levels, respectively, while the mode shapes changed very little. However, damage estimation based on the global characteristics of buildings can only provide rough assessments because of large uncertainties in the hysteresis behaviors of individual members and connections.…”

Section: Introductionmentioning

confidence: 99%

Evaluating damage extent of fractured beams in steel moment‐resisting frames using dynamic strain responses

Kurata

Nakashima

2014

Self Cite

Summary Delays in the postearthquake safety estimations of important buildings significantly increase unnecessary disorder in economic and social recovery following devastating earthquakes. Providing promptness and objectivity in evaluation procedures, damage detection through a structural health monitoring system using sensors attracts attention from building owners and other stakeholders. Nonetheless, local damage on individual structural elements is not easily identifiable, as such damage weakly relates to the global vibrational characteristics of buildings. The primary objectives of this research are to present and verify a method that quantifies the amount of local damage (i.e., fractures near beam–column connections) for the health monitoring of steel moment‐resisting frames that have undergone a strong earthquake ground motion. In this paper, a novel damage index based on the monitoring of dynamic strain responses of steel beams under ambient vibration before and after earthquakes is firstly presented. Then, the relation between the amount of local damage and the presented damage index is derived numerically with a parametric study using a nine‐story steel moment‐resisting frame model. Finally, the effectiveness of the damage index and an associated wireless strain‐sensing system are examined with a series of vibration tests using a five‐story steel frame test bed. Copyright © 2014 John Wiley & Sons, Ltd.

“…The method first quantifies the damage severity of a beam by computing the dynamicstrain-based damage index. Global monitoring tracks the overall behavior or modal properties of a structure, often using acceleration or displacement measurements at each floor (e.g., [5][6][7]) while local monitoring senses the responses of individual structural members to identify damage location and severity (e.g., acceleration or strain at beams or columns [8][9][10]). The residual structural capacity is then estimated in terms of changes in stiffness and strength, which can be applied by structural engineers, via a nonlinear static analysis of the updated model.…”

mentioning

confidence: 99%

Residual structural capacity evaluation of steel moment‐resisting frames with dynamic‐strain‐based model updating method

Suzuki

Kurata

et al. 2017

Summary This paper presents a method for evaluating the residual structural capacity of earthquake‐affected steel structures. The method first quantifies the damage severity of a beam by computing the dynamic‐strain‐based damage index. Next, the model used to analyze the structure is updated based on the damage index, to reflect the observed damage conditions. The residual structural capacity is then estimated in terms of changes in stiffness and strength, which can be applied by structural engineers, via a nonlinear static analysis of the updated model. The main contributions of this paper are in performance evaluation of the dynamic‐strain‐based damage index for seismically induced damage using a newly developed substructure testing environment, consideration of various damage patterns in composite beams, and extension of a local damage evaluation technique to a residual capacity estimation procedure by incorporating the model‐updating technique. In laboratory testing, the specimens were damaged quasi‐statically, and vibration tests were conducted as the damage proceeded. First, a bare steel beam–column connection was tested, and then a similar one with a floor slab was used for a more realistic case. The estimated residual structural capacities for these specimens were compared with the static test results. The results verified that the proposed method can provide fine estimates of the stiffness and strength deteriorations within 10% for the specimen without the floor slab and within 30% for that with the floor slab. Copyright © 2017 John Wiley & Sons, Ltd.