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Rangaraj, R.; Pokale, Bharat; Banerjee, Anuradha; Gupta, Sayan
doi: 10.1002/stc.1733pmid: N/A
Summary This study focuses on crack identification in beams from vibration measurements using principles of dynamic state estimation. The FEM is used to model the beam with cracked‐beam elements that account for the presence of an edge crack under near‐tip elasto‐plastic conditions. The crack size and its location are treated as the variables that are identified using a particle filter algorithm. A parametric study is first carried out with synthetic measurements to numerically analyze the performance of the algorithm. Subsequently, using measurements acquired from physical experiments involving a cantilever beam subjected to arbitrary excitations, the proposed algorithm is used to identify the size and location of crack‐like defects. The proposed method does not require measurements of the undamaged beam, hence, can be used for crack identification in beams for which no earlier measurements are available. Copyright © 2015 John Wiley & Sons, Ltd.
Moosavi, Hadi; Mirza Hessabi, Reza; Mercan, Oya
doi: 10.1002/stc.1731pmid: N/A
Summary In order to investigate the dynamic behavior of complex structural systems experimental testing is indispensable and real‐time pseudodynamic (PSD) and real‐time hybrid simulation (RTHS) are versatile testing methods to address this need. Accurate control of hydraulic actuators is essential for the accuracy and stability of these methods. This paper introduces a nonlinear state‐space controller to control hydraulic actuators under displacement control, specifically for real‐time testing applications. The proposed control design process uses the nonlinear state‐space model of the system, and utilizes state feedback linearization through a transformation of the state variables. As such, it can efficiently handle the nonlinearities associated with the servo‐hydraulic system and the test structure. Comparisons of numerical simulation results for linear state‐space and nonlinear state‐space controllers are provided. The improved tracking performance of the proposed controller will contribute to more accurate real‐time test results, which in turn will enable a more accurate assessment of dynamic characteristics of complex structural systems. Copyright © 2015 John Wiley & Sons, Ltd.
doi: 10.1002/stc.1734pmid: N/A
Summary This paper analyzes the properties of the dynamic behavior of two adjacent buildings of different height connected by viscous/viscoelastic dampers located at the top of the shortest building. The adjacent structures are described through a continuum approach as two interconnected uniform shear beams. This permits to identify the set of characteristic parameters describing the building and damper properties that completely control the dynamic behavior of the system. An analytical solution is derived for solving the eigenvalue problem via complex modal analysis, and a parametric study is carried out to evaluate the influence of these characteristic parameters on the properties of the dynamic system. A reduced‐order model of the system is also developed, and simplified formulas are obtained for estimating the damping ratios of the first two modes of the coupled system. Two case studies consisting of realistic shear‐type adjacent buildings coupled by viscous dampers are finally analyzed. The estimates of the modal properties obtained by using the proposed analytical approach and a finite element formulation are compared with each other. It is shown that the proposed approach provides information useful for the preliminary design of the damper properties ensuring the optimal control against seismic loadings. Copyright © 2015 John Wiley & Sons, Ltd.
Torres‐Arredondo, M.‐A.; Sierra‐Pérez, Julian; Tibaduiza, D.‐A.; McGugan, Malcolm; Rodellar, José; Fritzen, C.‐P.
doi: 10.1002/stc.1735pmid: N/A
Summary Damage assessment can be considered as the main task within the context of structural health monitoring (SHM) systems. This task is not only confined to the detection of damages in its basic algorithms but also in the generation of early warnings to prevent possible catastrophes in the daily use of the structures ensuring their proper functioning. Changes in environmental and operational conditions (EOC), in particularly temperature, affect the performance of SHM systems that constitutes a great limitation for their implementation in real world applications. This paper describes a health monitoring methodology combining the advantages of guided ultrasonic waves together with the compensation for temperature effects and the extraction of defect‐sensitive features for the purpose of carrying out a nonlinear multivariate diagnosis of damage. Two well‐known methods to compensate the temperature effects, namely optimal baseline selection and optimal signal stretch, are investigated within the proposed methodology where the performance is assessed using receiver operating characteristic curves. The methodology is experimentally tested in a pipeline. Results show that the methodology is a robust practical solution to compensate the temperature effects for the damage detection task. Copyright © 2015 John Wiley & Sons, Ltd.
Yang, Yongchao; Nagarajaiah, Satish; Ni, Yi‐Qing
doi: 10.1002/stc.1737pmid: N/A
Summary The intrinsic low‐dimensional structure, which is implicit in the large‐scale data sets of structural seismic and typhoon responses, is exploited for efficient data compression. Such a low‐dimensional structure, empirically, stems from few modes that are active in the structural dynamic responses. Originally, limited to the sensor and time‐history dimension, the structural seismic and typhoon response data set generally does not have an explicit low‐rank representation (e.g., by singular value decomposition or principal component analysis), which is critical in multi‐channel data compression. By the proposed matrix reshape scheme, the low‐rank structure of the large‐scale data set stands out, regardless of the original data dimension. Examples demonstrate that the developed method can significantly compress the large‐scale structural seismic and typhoon response data sets, which were recorded by the structural health monitoring system of the super high‐rise Canton Tower. Copyright © 2015 John Wiley & Sons, Ltd.
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