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Pnevmatikos N.♦, Konstandakopoulou F.♦, Błachowski B., Papavasileiou G.♦, Broukos P.♦, Multifractal analysis and wavelet leaders for structural damage detection of structures subjected to earthquake excitation,
Soil Dynamics and Earthquake Engineering, ISSN: 0267-7261, DOI: 10.1016/j.soildyn.2020.106328, Vol.139, pp.106328-1-4, 2020Streszczenie: This work is an effort to join, for the first-time, multifractal analysis and damage detection in civil structures subjected to strong ground seismic motions. Specifically, based on the singularity spectrum quantitative and qualitative criteria are proposed. The qualitative criteria are based on the concave of singularity spectrum of damage and undamaged structure. The proposed quantitative criterion is based on calculation of damage index taken the parameters of singularity spectrum. In order to achieve the above goal, a robust signal processing method, which is known as multifractal wavelet leader (MFWL) is used. The multifractal analysis is a tool to calculate fractal properties as well as scaling behavior of the structural response excited by an earthquake. The singularity spectrum is obtained from the Legendre-transformation to Holder exponents. In this paper, a parameter which is based on the shape of singularity spectrum and can identify the damage in the structure is proposed. The proposed method is an output-only approach for damage detection. Considering that the dynamic behavior of an inelastic system subjected to strong ground motion appears to be a non-stationary process, the above procedure of multifractal wavelet leader is suitable to retrieve the simulation response data. The findings from the analysis show that the MFWL is an appropriate scheme for structural damage detection. Słowa kluczowe: multifractal wavelet leader, damage detection, singularity spectrum, earthquake engineering, structural safety Afiliacje autorów:
Pnevmatikos N. | - | Technological Educational Institute Athens (GR) | Konstandakopoulou F. | - | inna afiliacja | Błachowski B. | - | IPPT PAN | Papavasileiou G. | - | University of the Highlands and Islands (GB) | Broukos P. | - | inna afiliacja |
| | 100p. |
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Błachowski B., Pnevmatikos N.♦, Neural network based vibration control of seismically excited civil structures,
Periodica Polytechnica Civil Engineering, ISSN: 0553-6626, DOI: 10.3311/PPci.11601, Vol.62, No.3, pp.620-628, 2018Streszczenie: This study proposes a neural network based vibration control system designed to attenuate structural vibrations induced by an earthquake. Classical feedback control algorithms are susceptible to parameter changes. For structures with uncertain parameters they can even cause instability problems. The proposed neural network based control system can identify the structural properties of the system and avoids the above mentioned problems. In the present study it is assumed that a full state of the structure is known, which means the at each floor horizontal displacements and rotations about the vertical axis are measured. Additionally, it is assumed the acceleration signal coming from the earthquake is also available. The proposed neural control strategy is compared with the classical linear quadratic regulator (LQR) not only in terms of displacement responses, but also required control forces. Moreover, the influence of different weighting matrices on performance of the proposed control strategy has been presented.
The effectiveness of the neuro-controller has been demonstrated on two numerical examples: a simple single degree of freedom (DOF) structure and a multi-DOF structure representing a twelve story building. Both structures under consideration have been excited with El Centro acceleration signal. The results of numerical simulations on the SDOF system indicate that using neuro-controller it would be possible to obtain smaller amplitudes as compared with the LQ regulator, but it would require higher control effort. Słowa kluczowe: vibration control, artificial neural networks, seismic excitation Afiliacje autorów:
Błachowski B. | - | IPPT PAN | Pnevmatikos N. | - | Technological Educational Institute Athens (GR) |
| | 15p. |
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Pnevmatikos N.G.♦, Błachowski B., Hatzigeorgiou G.D.♦, Świercz A., Wavelet analysis based damage localization in steel frames with bolted connections,
SMART STRUCTURES AND SYSTEMS, ISSN: 1738-1584, DOI: 10.12989/sss.2016.18.6.1189, Vol.18, No.6, pp.1189-1202, 2016Streszczenie: This paper describes an application of wavelet analysis for damage detection of a steel frame structure with bolted connections. The wavelet coefficients of the acceleration response for the healthy and loosened connection structure were calculated at each measurement point. The difference of the wavelet coefficients of the response of the healthy and loosened connection structure is selected as an indicator of the damage. At each node of structure the norm of the difference of the wavelet coefficients matrix is then calculated. The point for which the norm has the higher value is a candidate for location of the damage. The above procedure was experimentally verified on a laboratory-scale 2-meter-long steel frame. The structure consists of 11 steel beams forming a four-bay frame, which is subjected to impact loads using a modal hammer. The accelerations are measured at 20 different locations on the frame, including joints and beam elements. Two states of the structure are considered: healthy and damaged one. The damage is introduced by means of loosening two out of three bolts at one of the frame connections. Calculating the norm of the difference of the wavelet coefficients matrix at each node the higher value was found to be at the same location where the bolts were loosened. The presented experiment showed the effectiveness of the wavelet approach to damage detection of frame structures assembled using bolted connections. Słowa kluczowe: complex bolted lap connection, frame structure, wavelet analysis, damage detection Afiliacje autorów:
Pnevmatikos N.G. | - | Technological Educational Institute Athens (GR) | Błachowski B. | - | IPPT PAN | Hatzigeorgiou G.D. | - | Hellenic Open University (GR) | Świercz A. | - | IPPT PAN |
| | 30p. |