1. |
Ahsani S.^{♦}, Claeys C.^{♦}, Zieliński T.G., Jankowski Ł., Scarpa F.^{♦}, Desmet W.^{♦}, Deckers E.^{♦}, Sound absorption enhancement in poro-elastic materials in the viscous regime using a mass–spring effect,
JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2021.116353, Vol.511, pp.116353-1-16, 2021Streszczenie: This paper investigates the mechanisms that can be used to enhance the absorption performance of poro-elastic materials in the viscous regime. It is shown that by adding small inclusions in a poro-elastic foam layer, a mass–spring effect can be introduced. If the poro-elastic material has relatively high viscous losses in the frequency range of interest, the mass–spring effect can enhance the sound absorption of the foam by introducing an additional mode in the frame and increasing its out-of-phase movement with respect to the fluid part. Moreover, different effects such as the trapped mode effect, the modified-mode effect, and the mass–spring effect are differentiated by decomposing the absorption coefficient in terms of the three energy dissipation mechanisms (viscous, thermal, and structural losses) in poro-elastic materials. The physical and geometrical parameters that can amplify or decrease the mass–spring effect are discussed. Additionally, the influence of the incidence angle on the mass–spring effect is evaluated and a discussion on tuning the inclusion to different target frequencies is given. Słowa kluczowe: meta-poro-elastic material, Biot–Allard poroelastic model, mass–spring effect, viscous regime Afiliacje autorów:
Ahsani S. | - | Katholieke Universiteit Leuven (BE) | Claeys C. | - | Katholieke Universiteit Leuven (BE) | Zieliński T.G. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN | Scarpa F. | - | University of Bristol (UK) | Desmet W. | - | Katholieke Universiteit Leuven (BE) | Deckers E. | - | Katholieke Universiteit Leuven (BE) |
| | 200p. |
2. |
Popławski B., Mikułowski G., Wiszowaty R., Jankowski Ł., Mitigation of forced vibrations by semi-active control of local transfer of moments,
MECHANICAL SYSTEMS AND SIGNAL PROCESSING, ISSN: 0888-3270, DOI: 10.1016/j.ymssp.2021.107733, Vol.157, pp.107733-1-16, 2021Streszczenie: This paper proposes and tests a semi-active method for mitigation of random and harmonic forced vibrations of frame structures. The method is based on the Prestress Accumulation-Release (PAR) strategy, and it stimulates the transfer of vibration energy from low-order into high-order natural modes of vibration. Due to their high-frequency, the target high-order modes are efficiently mitigated by standard material damping mechanisms. The control is based on local reconfiguration of nodal ability to transfer moments between adjacent beams, which might be momentarily suppressed for selected nodes: performed at the maximum of the local bending strain, such a suppression stimulates a sudden release of the accumulated strain energy into high-frequency local and global vibrations. The effectiveness of the approach is confirmed numerically and experimentally in mitigation of low-frequency vibrations, including resonance conditions, of a slender planar frame structure subjected to harmonic, sweep and random forced excitations. Słowa kluczowe: damping of vibrations, smart structures, semi-active control, decentralized control, truss–frame nodes Afiliacje autorów:
Popławski B. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Wiszowaty R. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 200p. |
3. |
Ostrowski M., Błachowski B., Popławski B., Pisarski D., Mikułowski G., Jankowski Ł., Semi‐active modal control of structures with lockable joints: general methodology and applications,
STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.2710, Vol.28, No.5, pp.e2710-1-24, 2021Streszczenie: In this study, a novel modal control strategy by means of semi-actively lockable joints is proposed. The control strategy allows for a directed flow of energy between vibrational modes, which makes it suitable not only for vibration attenuation purposes but also for energy scavenging driven by electromechanical energy harvesters. The proposed control strategy is an extension of the prestress-accumulation release (PAR) technique; however, it introduces also new concepts that increase the efficiency of the overall control system. Contrary to the PAR, the proposed method requires measurement of both strains in the vicinity of the semi-active joints and translational velocities that provide global information about system behavior. The latter aspect requires the control system to be organized within a hierarchical feedback architecture. The benefit from this higher complexity of the control system is its better performance compared to the PAR. The proposed semi-active modal control not only attenuates structural vibration faster, but it also achieves this goal with a smaller number of switches implemented in the joints. The effectiveness of the proposed methodology has been demonstrated on structures equipped with two lockable joints. Two practical examples have been investigated: one employs the concept of vibration-based energy harvesting for a two-story frame structure, while the second one reduces vibration of an eight-story frame structure subjected to kinematic excitation. Słowa kluczowe: energy harvesting, lockable joint, modal coupling, semi-active control, vibration attenuation Afiliacje autorów:
Ostrowski M. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Popławski B. | - | IPPT PAN | Pisarski D. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 140p. |
4. |
Hou J.^{♦}, Li C.^{♦}, Jankowski Ł., Shi Y.^{♦}, Su L.^{♦}, Yu S.^{♦}, Geng T.^{♦}, Damage identification of suspender cables by adding virtual supports with the substructure isolation method,
STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.2677, Vol.28, No.3, pp.e2677-1-19, 2021Streszczenie: Damage of bridge cables is mainly manifested as the decrease in cable forces. These forces are affected by the boundary conditions, cable length, cable stiffness, and cable appendages, making it hard to identify the cable forces. Based on the substructure isolation method, this study proposes an approach for cable force identification to judge cable damage by adding virtual supports to each cable so that the cables share the same length and boundary conditions. The cable forces can then be identified according to the relationship between the natural frequency and cable forces. The basic concept is that the boundary sensors are transformed into virtual supports by a linear combination of the convolution of measured responses to achieve the zero boundary response. A finite element model of a suspension bridge was used to validate the proposed method in a simulation. When the virtual supports were added to the cables, the relationship between the cable forces and the natural frequency was almost linear, and the cable damage could be successfully identified with 5% noise. Finally, the effectiveness of the proposed method was verified experimentally, and the natural frequency of the isolated cable substructure was confirmed to be a highly sensitive damage indicator. Słowa kluczowe: cable damage, cable forces, natural frequency, structural health monitoring (SHM), substructure isolation method, virtual supports Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Li C. | - | inna afiliacja | Jankowski Ł. | - | IPPT PAN | Shi Y. | - | inna afiliacja | Su L. | - | Dalian University of Technology (CN) | Yu S. | - | inna afiliacja | Geng T. | - | inna afiliacja |
| | 140p. |
5. |
Mikułowski G., Popławski B., Jankowski Ł., Semi-active vibration control based on switchable transfer of bending moments: study and experimental validation of control performance,
SMART MATERIALS AND STRUCTURES, ISSN: 0964-1726, DOI: 10.1088/1361-665X/abe33b, Vol.30, No.4, pp.045005-1-045005-22, 2021Streszczenie: This paper presents an experimental approach to assessment of semi-active vibration control systems based on the Prestress-Accumulation Release concept. The objectives are threefold: 1) to introduce an experimental validation method for control algorithms based on switchable transfer of moments, 2) to propose a method to assess experimentally the control effects on structural dynamic response under several types of excitation, and 3) to propose an approach for adequate sensor placement. A laboratory frame demonstrator equipped with dedicated semi-active nodes is used. The proposed approach is based on spectral responses and modal analysis. According to the presented findings, the investigated control is effective in reducing the vibration level while keeping the structural dynamic stiffness at a proper level. The investigation is conducted in the case of free response, as well as responses to impact loading and random excitation. The results confirm the accuracy of the adopted algorithm parameters and reveal the sensor locations that provide the best control effectiveness. Afiliacje autorów:
Mikułowski G. | - | IPPT PAN | Popławski B. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 100p. |
6. |
Gawlicki M., Jankowski Ł., Trajectory identification for moving loads by multicriterial optimization,
SENSORS, ISSN: 1424-8220, DOI: 10.3390/s21010304, Vol.21, No.1, pp.304-1-20, 2021Streszczenie: Moving load is a fundamental loading pattern for many civil engineering structures and machines. This paper proposes and experimentally verifies an approach for indirect identification of 2D trajectories of moving loads. In line with the "structure as a sensor" paradigm, the identification is performed indirectly, based on the measured mechanical response of the structure. However, trivial solutions that directly fit the mechanical response tend to be erratic due to measurement and modeling errors. To achieve physically meaningful results, these solutions need to be numerically regularized with respect to expected geometric characteristics of trajectories. This paper proposes a respective multicriterial optimization framework based on two groups of criteria of a very different nature: mechanical (to fit the measured response of the structure) and geometric (to account for the geometric regularity of typical trajectories). The state-of-the-art multiobjective genetic algorithm NSGA-II is used to find the Pareto front. The proposed approach is verified experimentally using a lab setup consisting of a plate instrumented with strain gauges and a line-follower robot. Three trajectories are tested, and in each case the determined Pareto front is found to properly balance between the mechanical response fit and the geometric regularity of the trajectory. Słowa kluczowe: structural health monitoring (SHM), moving load, trajectory identification, geometric regularity, multicriterial optimization, load identification, inverse problems, structural mechanics Afiliacje autorów:
Gawlicki M. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 100p. |
7. |
Orłowska A., Gałęzia A.^{♦}, Świercz A., Jankowski Ł., Mitigation of vibrations in sandwich-type structures by a controllable constrained layer,
JOURNAL OF VIBRATION AND CONTROL, ISSN: 1077-5463, DOI: 10.1177/1077546320946130, Vol.27, No.13-14, pp.1595-1605, 2021Streszczenie: This study presents and tests a method for semi-active control of vibrations in sandwich-type beam structures. This method adapts a strategy called prestress accumulation release. The prestress accumulation release strategy is based on structural reconfiguration: it uses short time, impulsive and localised changes of actuator properties (such as stiffness or damping), which are applied to a part of the system in the moments, when its strain energy attains a local maximum. The method has been earlier applied as a global control scheme to mitigate the fundamental vibration mode of a cantilever beam (by stiffness control) and in the task of mitigating the first four modes of a frame structure (by damping control). This study proposes a prestress accumulation release strategy and tests its effectiveness for the case of a three-layered sandwich structure, with the internal layer fabricated from a material with dissipative characteristic locally controllable through the material damping coefficient. In contrast to the earlier research, the control is applied thus at the level of material characteristics instead of a discrete set of dedicated actuators. Based on the finite element method, a numerical experiment involving a passively damped, as well as prestress accumulation release-controlled, three-layered cantilever beam excited by initial displacements was performed. The effectiveness of the approach was studied for a broad range of internal layer damping parameters. The presented results revealed a high potential of the prestress accumulation release strategy in semi-active damping of vibrations of sandwich-type structures. Słowa kluczowe: vibration control, sandwich structure, semi-active control, decentralised control, smart structures, constrained layer method Afiliacje autorów:
Orłowska A. | - | IPPT PAN | Gałęzia A. | - | Warsaw University of Technology (PL) | Świercz A. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 70p. |
8. |
Zhang Q.^{♦}, Hou J.^{♦}, Duan Z.^{♦}, Jankowski Ł., Hu X.^{♦}, Road roughness estimation based on the vehicle frequency response function,
Actuators, ISSN: 2076-0825, DOI: 10.3390/act10050089, Vol.10, No.5, pp.89-1-20, 2021Streszczenie: Road roughness is an important factor in road network maintenance and ride quality. This paper proposes a road-roughness estimation method using the frequency response function (FRF) of a vehicle. First, based on the motion equation of the vehicle and the time shift property of the Fourier transform, the vehicle FRF with respect to the displacements of vehicle–road contact points, which describes the relationship between the measured response and road roughness, is deduced and simplified. The key to road roughness estimation is the vehicle FRF, which can be estimated directly using the measured response and the designed shape of the road based on the least-squares method. To eliminate the singular data in the estimated FRF, the shape function method was employed to improve the local curve of the FRF. Moreover, the road roughness can be estimated online by combining the estimated roughness in the overlapping time periods. Finally, a half-car model was used to numerically validate the proposed methods of road roughness estimation. Driving tests of a vehicle passing over a known-sized hump were designed to estimate the vehicle FRF, and the simulated vehicle accelerations were taken as the measured responses considering a 5% Gaussian white noise. Based on the directly estimated vehicle FRF and updated FRF, the road roughness estimation, which considers the influence of the sensors and quantity of measured data at different vehicle speeds, is discussed and compared. The results show that road roughness can be estimated using the proposed method with acceptable accuracy and robustness. Słowa kluczowe: structural health monitoring, road roughness, vehicle response, frequency response function, Fourier transform Afiliacje autorów:
Zhang Q. | - | inna afiliacja | Hou J. | - | Dalian University of Technology (CN) | Duan Z. | - | Shenzhen Graduate School of Harbin Institute of Technology (CN) | Jankowski Ł. | - | IPPT PAN | Hu X. | - | inna afiliacja |
| | 20p. |
9. |
Popławski B., Mikułowski G., Orłowska A., Jankowski Ł., On/off nodal reconfiguration for global structural control of smart 2D frames,
Journal of Applied and Computational Mechanics, ISSN: 2383-4536, DOI: 10.22055/jacm.2020.32454.2016, Vol.7, No.SI, pp.1121-1129, 2021Streszczenie: This paper proposes an on/off semi-active control approach for mitigation of free structural vibrations, designed for application in 2D smart frame structures. The approach is rooted in the Prestress-Accumulation Release (PAR) control strategies. The feedback signal is the global strain energy of the structure, or its approximation in the experimental setup. The actuators take the form of on/off nodes with a controllable ability to transfer moments (blockable hinges). Effectiveness of the approach is confirmed in a numerical simulation, as well as using a laboratory experimental test stand. Słowa kluczowe: structural reconfiguration, structural control, semi-active control, frame structures, controllable nodes Afiliacje autorów:
Popławski B. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Orłowska A. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 20p. |
10. |
Hou J.^{♦}, Li Z.^{♦}, Jankowski Ł., Wang S.^{♦}, Estimation of virtual masses for structural damage identification,
STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.2585, Vol.27, No.8, pp.e2528-1-21, 2020Streszczenie: Adding a virtual mass is an effective method for damage identification. It can be used to obtain a large amount of information about structural response and dynamics, thereby improving the sensitivity to local damage. In the current research approaches, the virtual mass is determined first, and then the modal characteristics of the virtually modified structure are identified. This requires a wide frequency band excitation; otherwise the crucial modes of the modified structure might be out of the band, which would negatively influence the modal analysis and damage identification. This paper proposes a method that first determines the target frequency and then estimates the corresponding value of the additional virtual mass. The target frequency refers to the desired value of the natural frequency after the virtual mass has been added to the structure. The virtual masses are estimated by tuning the frequency response peaks to the target frequencies. First, two virtual mass estimation methods are proposed. One is to directly calculate the virtual mass, using the frequency‐domain response at the target frequency point only, whereas the second method estimates the mass using a least‐squares fit based on the frequency‐domain response around the target frequency. Both proposed methods utilize merely a small part of the frequency domain. Therefore, an impulse, a simple harmonic, or a narrow spectral excitation can be used for damage identification. Finally, a numerical simulation of a simply supported beam and experiments of a frame structure and a truss structure are used to verify the effectiveness of the proposed method. Słowa kluczowe: damage identification, frequency response, structural health monitoring (SHM), virtual distortion method (VDM), virtual mass Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Li Z. | - | Dalian University of Technology (CN) | Jankowski Ł. | - | IPPT PAN | Wang S. | - | Dalian University of Technology (CN) |
| | 140p. |
11. |
Jankowski Ł., Quality over quantity: the case of a model journal,
Computer-Aided Civil and Infrastructure Engineering, ISSN: 1093-9687, DOI: 10.1111/mice.12560, Vol.35, No.7, pp.649-649, 2020 | | 140p. |
12. |
Błachowski B., Świercz A., Ostrowski M., Tauzowski P., Olaszek P.^{♦}, Jankowski Ł., Convex relaxation for efficient sensor layout optimization in large‐scale structures subjected to moving loads,
Computer-Aided Civil and Infrastructure Engineering, ISSN: 1093-9687, DOI: 10.1111/mice.12553, Vol.35, No.10, pp.1085-1100, 2020Streszczenie: This paper proposes a computationally effective framework for load‐dependent optimal sensor placement in large‐scale civil engineering structures subjected to moving loads. Two common problems are addressed: selection of modes to be monitored and computational effectiveness. Typical sensor placement methods assume that the set of modes to be monitored is known. In practice, determination of such modes of interest is not straightforward. A practical approach is proposed that facilitates the selection of modes in a quasi‐automatic way based on the structural response at the candidate sensor locations to typical operational loads. The criterion used to assess sensor placement is based on Kammer's Effective Independence (EFI). However, in contrast to typical implementations of EFI, which treat the problem as a computationally demanding discrete problem and use greedy optimization, an approach based on convex relaxation is proposed. A notion of sensor density is applied, which converts the original combinatorial problem into a computationally tractable continuous optimization problem. The proposed framework is tested in application to a real tied‐arch railway bridge located in central Poland. Słowa kluczowe: optimal sensor placement, effective independence method, Fisher information matrix Afiliacje autorów:
Błachowski B. | - | IPPT PAN | Świercz A. | - | IPPT PAN | Ostrowski M. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Olaszek P. | - | Instytut Badawczy Dróg i Mostów (PL) | Jankowski Ł. | - | IPPT PAN |
| | 140p. |
13. |
Pisarski D., Konowrocki R., Jankowski Ł., Scalable distributed optimal control of vibrating modular structures,
STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.2502, Vol.27, No.4, pp.e2502-1-21, 2020Streszczenie: A scalable optimal control method for structural vibration mitigation is studied. The method relies on a structure's partitioning that leads to a set of dynamically interconnected subsystems. Each subsystem is operated with an individual subcontroller that collects the local state information and collaborates with the neighboring subcontrollers to estimate a short time prediction of the interconnecting forces defining the subsystem's boundary conditions. Using the extended model that represents the subsystem's dynamics together with the evolution of its boundary conditions, each subcontroller computes the control decision based on the solution to a finite‐time horizon optimal control problem. In order to cope with the changes in the boundary conditions, the optimal solution is computed repetitively according to the receding horizon scheme. The method is validated numerically for a cantilever structure equipped with actively controlled electromagnetic actuators and subjected to a variety of initial condition scenarios. The performance of the designed controller is tested by comparisons to the centralized and isolated decentralized controllers. The introduced system partitioning and distributed controller allow performing parallel computing which makes the method fully scalable and applicable to large‐scale structures. The computational complexity of the designed distributed control is studied for different settings in the modeling of the subsystem's boundary conditions. Słowa kluczowe: active control, distributed control, modular structure, scalable optimization, stabilization Afiliacje autorów:
Pisarski D. | - | IPPT PAN | Konowrocki R. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 140p. |
14. |
Hou J.^{♦}, Li Z.^{♦}, Zhang Q., Jankowski Ł., Zhang H.^{♦}, Local mass addition and data fusion for structural damage identification using approximate models,
International Journal of Structural Stability and Dynamics, ISSN: 1793-6764, DOI: 10.1142/S0219455420501242, pp.1-24, 2020Streszczenie: In practical civil engineering, structural damage identification is difficult to implement due to the shortage of measured modal information and the influence of noise. Furthermore, typical damage identification methods generally rely on a precise Finite Element (FE) model of the monitored structure. Pointwise mass alterations of the structure can effectively improve the quantity and sensitivity of measured data, while the data fusion methods can adequately utilize various kinds of data and identification results. This paper proposes a damage identification method that requires only approximate FE models and combines the advantages of pointwise mass additions and data fusion. First, an additional mass is placed at different positions throughout the structure to collect the dynamic response and obtain the corresponding modal information. The resulting relation between natural frequencies and the position of the added mass is sensitive to local damage, and it is thus utilized to form a new objective function based on the modal assurance criterion (MAC) and l1-based sparsity promotion. The proposed objective function is mostly insensitive to global structural parameters, but remains sensitive to local damage. Several approximate FE models are then established and separately used to identify the damage of the structure, and then the Dempster-Shafer method of data fusion is applied to fuse the results from all the approximate models. Finally, fractional data fusion is proposed to combine the results according to the parametric probability distribution of the approximate FE models, which allows the natural weight of each approximate model to be determined for the fusion process. Such an approach circumvents the need for a precise FE model, which is usually not easy to obtain in real application, and thus enhances the practical applicability of the proposed method, while maintaining the damage identification accuracy. The proposed approach is verified numerically and experimentally. Numerical simulations of a simply supported beam and a long-span bridge confirm that it can be used for damage identification, including a single damage and multiple damages, with a high accuracy. Finally, an experiment of a cantilever beam is successfully performed. Słowa kluczowe: structural health monitoring (SHM), damage identification, adding mass, data fusion, objective function, modal assurance criterion (MAC) Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Li Z. | - | Dalian University of Technology (CN) | Zhang Q. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN | Zhang H. | - | inna afiliacja |
| | 100p. |
15. |
Zhang Q.^{♦}, Hou J.^{♦}, Jankowski Ł., Bridge damage identification using vehicle bump based on additional virtual masses,
SENSORS, ISSN: 1424-8220, DOI: 10.3390/s20020394, Vol.20, No.2, pp.394-1-23, 2020Streszczenie: Structural damage identification plays an important role in providing effective evidence for the health monitoring of bridges in service. Due to the limitations of measurement points and lack of valid structural response data, the accurate identification of structural damage, especially for large-scale structures, remains difficult. Based on additional virtual mass, this paper presents a damage identification method for bridges using a vehicle bump as the excitation. First, general equations of virtual modifications, including virtual mass, stiffness, and damping, are derived. A theoretical method for damage identification, which is based on additional virtual mass, is formulated. The vehicle bump is analyzed, and the bump-induced excitation is estimated via a detailed analysis in four periods: separation, free-fall, contact, and coupled vibrations. The precise estimation of bump-induced excitation is then applied to a bridge. This allows the additional virtual mass method to be used, which requires knowledge of the excitations and acceleration responses in order to construct the frequency responses of a virtual structure with an additional virtual mass. Via this method, a virtual mass with substantially more weight than a typical vehicle is added to the bridge, which provides a sufficient amount of modal information for accurate damage identification while avoiding the bridge overloading problem. A numerical example of a two-span continuous beam is used to verify the proposed method, where the damage can be identified even with 15% Gaussian random noise pollution using a 1-degree of freedom (DOF) car model and 4-DOF model. Słowa kluczowe: structural health monitoring, damage identification, vehicle bump, additional virtual mass, bridge Afiliacje autorów:
Zhang Q. | - | inna afiliacja | Hou J. | - | Dalian University of Technology (CN) | Jankowski Ł. | - | IPPT PAN |
| | 100p. |
16. |
Hou J.^{♦}, Wang H.^{♦}, Xu D.^{♦}, Jankowski Ł., Wang P.^{♦}, Damage identification based on adding mass for liquid-solid coupling structures,
Applied Sciences, ISSN: 2076-3417, DOI: 10.3390/app10072312, Vol.10, No.7, pp.2312-1-20, 2020Streszczenie: Damage identification for liquid–solid coupling structures remains a challenging topic due to the influence of liquid and the limitation of experimental conditions. Therefore, the adding mass method for damage identification is employed in this study. Adding mass to structures is an effective method for damage identification, as it can increase not only the experimental data but also the sensitivity of experimental modes to local damage. First, the fundamental theory of the adding mass method for damage identification is introduced. After that, the method of equating the liquid to the attached mass is proposed by considering the liquid–solid coupling. Finally, the effectiveness and reliability of damage identification, based on adding mass for liquid–solid coupling structures, are verified through experiments of a submerged cantilever beam and liquid storage tank. Słowa kluczowe: structural health monitoring, damage identification, liquid-solid coupling, adding mass, sensitivity Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Wang H. | - | inna afiliacja | Xu D. | - | inna afiliacja | Jankowski Ł. | - | IPPT PAN | Wang P. | - | Dalian University of Technology (CN) |
| | 70p. |
17. |
Ostrowski M., Błachowski B., Jankowski Ł., Pisarski D., Modal energy transfer by controlled structural connections,
DIAGNOSTYKA, ISSN: 1641-6414, DOI: 10.29354/diag/116692, Vol.21, No.1, pp.61-70, 2020Streszczenie: This paper describes a semi-active control strategy that allows to transfer the vibration energy from an arbitrarily induced to a selected structural mode. The intended aim of the proposed control strategy is energy harvesting from structural vibrations. Another potential application is related to structural safety. In the paper, a mathematical model is first introduced to describe the phenomenon of vibrational energy transfer, and then, based on this model, an efficient semi-active control strategy is proposed. Finally, some problems related to measurement techniques are discussed. The effectiveness of the proposed methodology is demonstrated in an example of energy transfer between vibrational modes of a three-bar planar frame structure. Słowa kluczowe: vibration energy, modal control, lockable joint, modal coupling Afiliacje autorów:
Ostrowski M. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN | Pisarski D. | - | IPPT PAN |
| | 20p. |
18. |
Błachowski B., Ostrowski M., Tauzowski P., Świercz A., Jankowski Ł., Sensor placement for structural damage identification by means of topology optimization,
AIP Conference Proceedings, ISSN: 0094-243X, DOI: 10.1063/5.0007817, Vol.2239, No.1, pp.020002-1-11, 2020Streszczenie: The success of virtually all structural health monitoring (SHM) methods depends on the information content of the measurements, and thus on the placement of the available sensors. This paper presents an efficient method for finding optimal sensor distribution over structural system with many degrees of freedom (DOFs). The objective function is based on the classical Fisher information matrix. Originally, this yields a computationally hard discrete optimization problem. However, the proposed numerical solution method is based on a concept taken from structural topology optimization, where a discrete optimization problem is replaced with a continuous one. Two numerical examples demonstrate the effectiveness of the proposed methodology. These are a 5-bay truss with 24 DOFs and a two-story frame structure whose finite element model has been condensed to 14 DOFs. Słowa kluczowe: optimal sensor placement, structural damage identification, topology optimization Afiliacje autorów:
Błachowski B. | - | IPPT PAN | Ostrowski M. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Świercz A. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| |
19. |
Zawidzki M., Jankowski Ł., Multiobjective optimization of modular structures: weight versus geometric versatility in a Truss-Z system,
Computer-Aided Civil and Infrastructure Engineering, ISSN: 1093-9687, DOI: 10.1111/mice.12478, Vol.34, No.11, pp.1026-1040, 2019Streszczenie: This paper proposes an approach for multicriterial optimization of modular structures with respect to their structural and geometrical properties. The approach is tested using the quickly deployable and reconfigurable modular ramp system Truss-Z intended for pedestrian traffic. The focus is on modular structures composed of a moderate number of relatively complex modules, which feature an irregular, noncuboidal geometry. Such modules can be assembled into a variety of geometrically different configurations which do not adhere to any predefined spatial grid; their global geometry can be treated as free-form and determined in situ during construction. The optimization variables represent local-level geometrical and structural properties of a single module. The Pareto front is used to balance between two kinds of objectives. The geometrical objective quantifies the ability of the modules to generate geometrically versatile global structures that are well-suited to comply with spatial constraints of real construction sites. The structural objective is formalized in analogy to the minimum weight problem with upper bound constraints imposed on the von Mises stress and the Euler buckling load ratio. A two-level optimization scheme is employed with NSGA-II at the top level and a simulated annealing with adaptive neighborhood at the lower level. Słowa kluczowe: modular structures, multicriterial optimization, shape optimization, sizing optimization, NSGA-II, simulated annealing with adaptive neighborhood Afiliacje autorów:
Zawidzki M. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 140p. |
20. |
Faraj R., Jankowski Ł., Graczykowski C., Holnicki-Szulc J., Can the inerter be a successful shock-absorber? The case of a ball-screw inerter with a variable thread lead,
Journal of the Franklin Institute, ISSN: 0016-0032, DOI: 10.1016/j.jfranklin.2019.04.012, Vol.356, No.14, pp.7855-7872, 2019Streszczenie: This paper investigates an application of a ball-screw inerter for mitigation of impact loadings. The problem of impact absorption is to provide a minimum reaction force that optimally decelerates and eventually stops an impacting object within the available absorber stroke. It significantly differs from vibration mitigation problems which are typical application of inerters. The paper demonstrates that the optimum absorption can be achieved by fully passive means. For known values of the object mass and inerter parameters, the obtained solution is independent of the impact velocity. The optimum passive absorption is achieved by employing a variable thread lead. As a result, two force components emerge, the typical inertance-related force and a damping-like term, and sum up to provide the optimum constant deceleration force. This result is relatively unique: conventional absorbers do not provide a constant force even with complex active control systems. Finally, an optimization problem is formulated to reduce the influence of process uncertainties (range of possible mass values, unknown friction). The results are verified and analyzed in a numerical example. Afiliacje autorów:
Faraj R. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN | Graczykowski C. | - | IPPT PAN | Holnicki-Szulc J. | - | IPPT PAN |
| | 100p. |
21. |
Hou J.^{♦}, Li Z.^{♦}, Zhang Q., Zhou R.^{♦}, Jankowski Ł., Optimal placement of virtual masses for structural damage identification,
SENSORS, ISSN: 1424-8220, DOI: 10.3390/s19020340, Vol.19, No.2, pp.340-1-18, 2019Streszczenie: Adding virtual masses to a structure is an efficient way to generate a large number of natural frequencies for damage identification. The influence of a virtual mass can be expressed by Virtual Distortion Method (VDM) using the response measured by a sensor at the involved point. The proper placement of the virtual masses can improve the accuracy of damage identification, therefore the problem of their optimal placement is studied in this paper. Firstly, the damage sensitivity matrix of the structure with added virtual masses is built. The Volumetric Maximum Criterion of the sensitivity matrix is established to ensure the mutual independence of measurement points for the optimization of mass placement. Secondly, a method of sensitivity analysis and error analysis is proposed to determine the values of the virtual masses, and then an improved version of the Particle Swarm Optimization (PSO) algorithm is proposed for placement optimization of the virtual masses. Finally, the optimized placement is used to identify the damage of structures. The effectiveness of the proposed method is verified by a numerical simulation of a simply supported beam structure and a truss structure. Słowa kluczowe: damage identification, sensor optimization, virtual distortion method (VDM), particle swarm optimization (PSO) algorithm, sensitivity Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Li Z. | - | Dalian University of Technology (CN) | Zhang Q. | - | IPPT PAN | Zhou R. | - | Dalian University of Technology (CN) | Jankowski Ł. | - | IPPT PAN |
| | 100p. |
22. |
Hou J.^{♦}, Wang P.^{♦}, Jing T.^{♦}, Jankowski Ł., Experimental study for damage identification of storage tanks by adding virtual masses,
SENSORS, ISSN: 1424-8220, DOI: 10.3390/s19020220, Vol.19, No.2, pp.220-1-17, 2019Streszczenie: This research proposes a damage identification approach for storage tanks that is based on adding virtual masses. First, the frequency response function of a structure with additional virtual masses is deduced based on the Virtual Distortion Method (VDM). Subsequently, a Finite Element (FE) model of a storage tank is established to verify the proposed method; the relation between the added virtual masses and the sensitivity of the virtual structure is analyzed to determine the optimal mass and the corresponding frequency with the highest sensitivity with respect to potential damages. Thereupon, the damage can be localized and quantified by comparing the damage factors of substructures. Finally, an experimental study is conducted on a storage tank. The results confirm that the proposed method is feasible and practical, and that it can be applied for damage identification of storage tanks. Słowa kluczowe: damage identification, storage tanks, sensitivity analysis, frequency Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Wang P. | - | Dalian University of Technology (CN) | Jing T. | - | Dalian University of Technology (CN) | Jankowski Ł. | - | IPPT PAN |
| | 100p. |
23. |
Popławski B., Mikułowski G., Pisarski D., Wiszowaty R., Jankowski Ł., Optimum actuator placement for damping of vibrations using the prestress-accumulation release control approach,
SMART STRUCTURES AND SYSTEMS, ISSN: 1738-1584, DOI: 10.12989/sss.2019.24.1.027, Vol.24, No.1, pp.27-35, 2019Streszczenie: This paper proposes a quantitative criterion for optimization of actuator placement for the Prestress–Accumulation Release (PAR) strategy of mitigation of vibrations. The PAR strategy is a recently developed semi-active control approach that relies on controlled redistribution of vibration energy into high-order modes, which are high-frequency and thus effectively dissipated by means of the natural mechanisms of material damping. The energy transfer is achieved by a controlled temporary removal of selected structural constraints. This paper considers a short-time decoupling of rotational degrees of freedom in a frame node so that the bending moments temporarily cease to be transferred between the involved beams. We propose and test a quantitative criterion for placement of such actuators. The criterion is based on local modal strain energy that can be released into high-order modes. The numerical time complexity is linear with respect to the number of actuators and potential placements, which facilitates quick analysis in case of large structures. Słowa kluczowe: semi-active control, damping of vibrations, actuator placement, smart structures, prestress-accumulation release (PAR) Afiliacje autorów:
Popławski B. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Pisarski D. | - | IPPT PAN | Wiszowaty R. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 70p. |
24. |
Hou J.^{♦}, Wang S.^{♦}, Zhang Q.^{♦}, Jankowski Ł., An improved objective function for modal-based damage identification using substructural virtual distortion method,
Applied Sciences, ISSN: 2076-3417, DOI: 10.3390/app9050971, Vol.9, No.5, pp.971-1-17, 2019Streszczenie: Damage identification based on modal parameters is an important approach in structural health monitoring (SHM). Generally, traditional objective functions used for damage identification minimize the mismatch between measured modal parameters and the parameters obtained from the finite element (FE) model. However, during the optimization process, the repetitive calculation of structural modes is usually time-consuming and inefficient, especially for large-scale structures. In this paper, an improved objective function is proposed based on certain characteristics of the peaks of the frequency response function (FRF). Traditional objective functions contain terms that quantify modal shapes and/or natural frequencies. Here, it is proposed to replace them by the FRF of the FE model, which allows the repeated full modal analysis to be avoided and thus increases the computational efficiency. Moreover, the efficiency is further enhanced by employing the substructural virtual distortion method (SVDM), which allows the frequency response of the FE model of the damaged structure to be quickly computed without the costly re-analysis of the entire damaged structure. Finally, the effectiveness of the proposed method is verified using an eight-story frame structure model under several damage cases. The damage location and extent of each substructure can be identified accurately with 5% white Gaussian noise, and the optimization efficiency is greatly improved compared with the method using a traditional objective function. Słowa kluczowe: structural health monitoring (SHM), damage identification, substructure, virtual distortion method (VDM), frequency response Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Wang S. | - | Dalian University of Technology (CN) | Zhang Q. | - | inna afiliacja | Jankowski Ł. | - | IPPT PAN |
| | 70p. |
25. |
Popławski B., Mikułowski G., Mróz A., Jankowski Ł., Decentralized semi-active damping of free structural vibrations by means of structural nodes with an on/off ability to transmit moments,
MECHANICAL SYSTEMS AND SIGNAL PROCESSING, ISSN: 0888-3270, DOI: 10.1016/j.ymssp.2017.08.012, Vol.100, pp.926-939, 2018Streszczenie: This paper proposes, tests numerically and verifies experimentally a decentralized control algorithm with local feedback for semi-active mitigation of free vibrations in frame structures. The algorithm aims at transferring the vibration energy of low-order, lightly-damped structural modes into high-frequency modes of vibration, where it is quickly damped by natural mechanisms of material damping. Such an approach to mitigation of vibrations, known as the prestress-accumulation release (PAR) strategy, has been earlier applied only in global control schemes to the fundamental vibration mode of a cantilever beam. In contrast, the decentralization and local feedback allows the approach proposed here to be applied to more complex frame structures and vibration patterns, where the global control ceases to be intuitively obvious. The actuators (truss–frame nodes with controllable ability to transmit moments) are essentially unblockable hinges that become unblocked only for very short time periods in order to trigger local modal transfer of energy. The paper proposes a computationally simple model of the controllable nodes, specifies the control performance measure, yields basic characteristics of the optimum control, proposes the control algorithm and then tests it in numerical and experimental examples. Słowa kluczowe: Damping of vibrations, Smart structures, Semi-active control, Decentralized control, Truss-frame nodes Afiliacje autorów:
Popławski B. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Mróz A. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 45p. |
26. |
Hou J.^{♦}, An Y.^{♦}, Wang S.^{♦}, Wang Z.^{♦}, Jankowski Ł., Ou J.^{♦}, Structural Damage Localization and Quantification Based on Additional Virtual Masses and Bayesian Theory,
JOURNAL OF ENGINEERING MECHANICS-ASCE, ISSN: 0733-9399, DOI: 10.1061/(ASCE)EM.1943-7889.0001523, Vol.144, No.10, pp.04018097-1-9, 2018Streszczenie: In vibration-based damage identification, a common problem is that modal information is not enough and insensitive to local damage. To solve this problem, an effective method is to increase the amount of modal information and enhance the sensitivity of the experimental data to the local damage. In this paper, a damage identification method based on additional virtual masses and Bayesian theory is proposed. First, the virtual structure with optimal additional mass and high sensitivity to local damage is determined through sensitivity analysis, and then a large number of virtual structures can be obtained by adding virtual masses; thus, a lot of modal and statistical information of virtual structures can be obtained. Second, the Bayesian theory is used to obtain the posterior probability distribution of the damage factor when structural a priori information is considered. Third, by finding the extreme value of the probability density function, the damage factor is derived based on the a priori information and the statistical information of virtual structures. Finally, the effectiveness of the proposed method is verified by numerical simulations and experiments of a 3-story frame structure. Experimental and numerical results show that the proposed method can be used to identify the damage severity of each substructure and thus damaged substructures can be localized and quantified; the error in damage factor is basically within 5%, which shows the accuracy of the proposed method. The proposed method can not only provide the structural damage localization and quantification result (i.e., the damage factor), but also the probability distribution of the damage factor; moreover, it has high sensitivity to damage and high accuracy and efficiency. Słowa kluczowe: Structural health monitoring, Damage identification, Bayesian theory, Virtual distortion method (VDM), Virtual mass Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | An Y. | - | Dalian University of Technology (CN) | Wang S. | - | Dalian University of Technology (CN) | Wang Z. | - | Chalco Shandong Engineering Technology Co., Ltd. (CN) | Jankowski Ł. | - | IPPT PAN | Ou J. | - | Dalian University of Technology (CN) |
| | 30p. |
27. |
Zawidzki M., Jankowski Ł., Optimization of modular Truss-Z by minimum-mass design under equivalent stress constraint,
SMART STRUCTURES AND SYSTEMS, ISSN: 1738-1584, DOI: 10.12989/sss.2018.21.6.715, Vol.21, No.6, pp.715-725, 2018Streszczenie: Truss-Z (TZ) is an Extremely Modular System (EMS). Such systems allow for creation of structurally sound free-form structures, are comprised of as few types of modules as possible, and are not constrained by a regular tessellation of space. Their objective is to create spatial structures in given environments connecting given terminals without self-intersections and obstacle-intersections. TZ is a skeletal modular system for creating free-form pedestrian ramps and ramp networks. The previous research on TZ focused on global discrete geometric optimization of the spatial configuration of modules. This paper reports on the first attempts at structural optimization of the module for a single-branch TZ. The internal topology and the sizing of module beams are subject to optimization. An important challenge is that the module is to be universal: it must be designed for the worst case scenario, as defined by the module position within a TZ branch and the geometric configuration of the branch itself. There are four variations of each module, and the number of unique TZ configurations grows exponentially with the branch length. The aim is to obtain minimum-mass modules with the von Mises equivalent stress constrained under certain design load. The resulting modules are further evaluated also in terms of the typical structural criterion of compliance. Słowa kluczowe: Extremely Modular System, Truss-Z, structural optimization, modular structures, minimum mass design, frame structures Afiliacje autorów:
Zawidzki M. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 30p. |
28. |
Hou J.^{♦}, Jing T.^{♦}, Wang P.^{♦}, Zhang Q.^{♦}, Jankowski Ł., Damage identification method for storage tanks based on additional virtual masses,
JOURNAL OF VIBRATION AND SHOCK, ISSN: 1000-3835, DOI: 10.13465/j.cnki.jvs.2018.13.002, Vol.37, No.13, pp.7-13, 2018Streszczenie: A damage identification method based on additional virtual masses was proposed aiming at storage tanks' features of space-symmetry, dense lower-order modes and being insensitive to local damages. Firstly, magnitudes of additional masses were determined through sensitivity analysis of storage tanks' structural modes. Then based on the virtual deflection method (VDM), the tanks' frequency responses after attaching additional virtual masses were constructed and their natural frequencies were identified with the original structures' excitation time histories and the original structures' corresponding positions' acceleration response time histories. Furthermore, using the tanks' features of space-symmetry, their damage positions were preliminarily determined according to the distribution law of their natural frequencies after attaching virtual masses. The sensitivity analysis of the tanks' finite element model was used to solve iteratively damages' level. Finally, the tanks' finite element models were used to perform numerical simulations and correctly predict their damage locations and levels. The effectiveness of this proposed method was verified. Słowa kluczowe: storage tanks, damage identification, sensitivity analysis, frequency Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Jing T. | - | Dalian University of Technology (CN) | Wang P. | - | Dalian University of Technology (CN) | Zhang Q. | - | inna afiliacja | Jankowski Ł. | - | IPPT PAN |
| |
29. |
Suwała G., Jankowski Ł., Nonparametric identification of structural modifications in Laplace domain,
MECHANICAL SYSTEMS AND SIGNAL PROCESSING, ISSN: 0888-3270, DOI: 10.1016/j.ymssp.2016.09.018, Vol.85, pp.867-878, 2017Streszczenie: This paper proposes and experimentally verifies a Laplace-domain method for identification of structural modifications, which (1) unlike time-domain formulations, allows the identification to be focused on these parts of the frequency spectrum that have a high signal-to-noise ratio, and (2) unlike frequency-domain formulations, decreases the influence of numerical artifacts related to the particular choice of the FFT exponential window decay. In comparison to the time-domain approach proposed earlier, advantages of the proposed method are smaller computational cost and higher accuracy, which leads to reliable performance in more difficult identification cases. Analytical formulas for the first- and second-order sensitivity analysis are derived. The approach is based on a reduced nonparametric model, which has the form of a set of selected structural impulse responses. Such a model can be collected purely experimentally, which obviates the need for design and laborious updating of a parametric model, such as a finite element model. The approach is verified experimentally using a 26-node lab 3D truss structure and 30 identification cases of a single mass modification or two concurrent mass modifications. Słowa kluczowe: structural health monitoring (SHM), nonparametric model, inverse problem, virtual distortion method (VDM), structural reanalysis, sensitivity analysis, Laplace domain Afiliacje autorów:
Suwała G. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 45p. |
30. |
Michajłow M., Jankowski Ł., Szolc T., Konowrocki R., Semi-active reduction of vibrations in the mechanical system driven by an electric motor,
OPTIMAL CONTROL APPLICATIONS & METHODS, ISSN: 0143-2087, DOI: 10.1002/oca.2297, Vol.38, No.6, pp.922-933, 2017Streszczenie: In this paper, a semi-active damping approach is used for reduction of vibrations in a laboratory drivetrain system. The considered drivetrain system is powered by an electric, asynchronous motor at the one side and loaded with a harmonically varying torque on the other side. Here, an influence of electromechanical interaction, i.e., an electromechanical coupling, between the electric motor and the mechanical system has been taken into consideration. The harmonic load signal induces torsional vibrations in the system, which in the steady-state phase of motion become periodic. The aim of the work is to determine the optimal control function for a semi-active damping element, leading to vibration reduction and considering only the steady-state phase of system motion. The optimal control is derived by using a semi-analytical approach based on the optimal control theory aided with supplementary numerical computations. The proposed methodology is fully general, and it can be directly applied to any type of a periodically oscillating system. Słowa kluczowe: electric motor, electromechanical coupling, optimal control, periodic torsional vibrations, semi-active damping Afiliacje autorów:
Michajłow M. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN | Szolc T. | - | IPPT PAN | Konowrocki R. | - | IPPT PAN |
| | 30p. |
31. |
Zhang Q., Jankowski Ł., Damage identification using structural modes based on substructure virtual distortion method,
ADVANCES IN STRUCTURAL ENGINEERING, ISSN: 1369-4332, DOI: 10.1177/1369433216660018, Vol.20, No.2, pp.257-271, 2017Streszczenie: A damage identification approach is presented using substructure virtual distortion method which takes the advantage of the fast structural reanalysis technique of virtual distortion method. The formulas of substructure virtual distortion method are deduced in frequency domain, and then the frequency response function of the damaged structure is constructed quickly via the superposition of the frequency response function of the intact structure and the frequency responses caused by the damage-coupling virtual distortions of the substructures. The structural damage extents are identified using the measured modal parameters. Two steps are adopted to increase the efficiency of optimization: the modals of finite element model are estimated quickly from the fast constructed frequency response function during the optimization and the primary distortions of the substructures are extracted by contribution analysis to further reduce the computational work. A six-story frame numerical model and an experiment of a cantilever beam are carried out, respectively, to verify the efficiency and accuracy of the proposed method. Słowa kluczowe: damage identification, frequency domain, structural health monitoring, substructure, virtual distortion method Afiliacje autorów:
Zhang Q. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 20p. |
32. |
Holnicki-Szulc J., Ichchou M.^{♦}, Duan Z.^{♦}, Jankowski Ł., Adaptive Impact Absorption,
MATHEMATICAL PROBLEMS IN ENGINEERING, ISSN: 1024-123X, DOI: 10.1155/2016/4871549, Vol.2016, pp.4871549-1-2, 2016Streszczenie: The surging quest for safety is a clearly visible trend in modern societies. One of the related areas of research is the design of systems protecting against heavy dynamic loads such as low and medium velocity traffic-related impacts and environmental loadings. Commonly applied passive systems are typically designed to withstand a specified, well-defined heavy load scenario, which limits their performance over any wider range of loads, including the less heavy loads that are encountered in the lifetime of a typical structure much more often than the maximum limiting loads. Afiliacje autorów:
Holnicki-Szulc J. | - | IPPT PAN | Ichchou M. | - | École Centrale de Lyon (FR) | Duan Z. | - | Shenzhen Graduate School of Harbin Institute of Technology (CN) | Jankowski Ł. | - | IPPT PAN |
| | 20p. |
33. |
Michajłow M., Szolc T., Jankowski Ł., Konowrocki R., Semi-Active Reduction of Vibrations of Periodically Oscillating System,
Solid State Phenomena, ISSN: 1662-9779, DOI: 10.4028/www.scientific.net/SSP.248.111, Vol.248, pp.111-118, 2016Streszczenie: Periodical vibrations are common phenomenon affecting a wide range of mechanical systems. Most frequently it affects machines designed to work in a steady-state conditions like: turbine, pump, rail vehicle, etc. In those kinds of machines it is always possible to decompose the system motion to basic average-speed constant component and oscillatory component. Usually the second term is treated as undesirable and various techniques are applied in order to minimize it as far as it is possible. These techniques refers to both the hardware selection – meaning the type of damping system (active, semi-active, passive) and the control method selection – meaning the damping system control method. Concerning the control methods, there are many algorithms available in literature devoted to transient systems. One of typical application is to use them in systems experiencing sudden, external force excitation. After destabilization of the system, caused by excitation, the role of the control algorithm is to restore the system stable position and additionally to reach the extreme of some additional criterion. Typical criterions are minimization of the time, of restoring the stable position, minimizing the consumed control energy, etc. On the other hand, considering the steady-state systems, especially based on semi-active damping elements, there are not so many control methods available.This paper focuses on developing the proper methodology for deriving the optimal control strategy of semi-active damping element, to be used in periodically vibrating mechanical system. The control strategy is developed on the basis of the Optimal Control Theory. Numerical computations are involved in order to solve the optimal control problem for the considered test system. Problem solution reveals the periodical nature of optimal control function. Słowa kluczowe: Optimal Control Theory, Periodical Vibrations, Vibration Reduction Afiliacje autorów:
Michajłow M. | - | IPPT PAN | Szolc T. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN | Konowrocki R. | - | IPPT PAN |
| |
34. |
Hou J.^{♦}, Jankowski Ł., Ou J.^{♦}, Frequency-domain substructure isolation for local damage identification,
ADVANCES IN STRUCTURAL ENGINEERING, ISSN: 1369-4332, DOI: 10.1260/1369-4332.18.1.137, Vol.18, No.1, pp.137-153, 2015Streszczenie: This paper proposes a frequency-domain method of substructure identification for local health monitoring using substructure isolation method (SIM). The first key step of SIM is the numerical construction of the isolated substructure, which is a virtual and independent structure that has the same physical parameters as the real substructure. Damage identification and local monitoring can be then performed using the responses of the simple isolated substructure and any of the classical methods aimed originally at global structural analysis. This paper extends the SIM to frequency domain, which allows the computational efficiency of the method to be significantly increased in comparison to time domain. The mass-spring numerical model is used to introduce the method. Two aluminum beams with the same substructure are then used in experimental verification. In both cases the method performs efficiently and accurately. Słowa kluczowe: structural health monitoring (SHM), damage identification, substructuring frequency domain, boundary Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Jankowski Ł. | - | IPPT PAN | Ou J. | - | Dalian University of Technology (CN) |
| | 20p. |
35. |
Chen G.Y.^{♦}, Codemard C.A.^{♦}, Lewis R.J.^{♦}, Jankowski Ł., Chan J.S.^{♦}, Gorman P.M^{♦}, Zervas M.N.^{♦}, Enhanced responsivity with skew ray excitation of reflection- and transmission-type refractometric sensors,
OPTICS LETTERS, ISSN: 0146-9592, DOI: 10.1364/OL.39.003822, Vol.39, No.13, pp.3822-3825, 2014Streszczenie: The responsivity of optical fibers to refractive index can be enhanced using high-order skew rays compared with using meridional rays. Skew rays can have a much higher number of reflections with increased interaction length along the core–cladding interface, which gives rise to stronger interactions with the external medium. Reflection/transmission-type refractometric sensors based on twin-coupled-core and multimode fibers showed one/two orders of magnitude increase in responsivity with skew ray excitation. The responsivity and sensitivity for the two types are ∼2000%/RIU, ∼1400%/RIU, and 4.9×10−5 RIU, 7.0×10−5 RIU, respectively. Słowa kluczowe: Fiber optics sensors, Fiber properties, Remote sensing and sensors, Propagation, Biological sensing and sensors Afiliacje autorów:
Chen G.Y. | - | University of Southampton (GB) | Codemard C.A. | - | Advanced Laser Laboratory SPI Lasers (GB) | Lewis R.J. | - | Cardiff University (GB) | Jankowski Ł. | - | IPPT PAN | Chan J.S. | - | University of Southampton (GB) | Gorman P.M | - | Advanced Laser Laboratory SPI Lasers (GB) | Zervas M.N. | - | University of Southampton (GB) |
| | 40p. |
36. |
Hou J.^{♦}, Jankowski Ł., Ou J.^{♦}, Substructure isolation and damage identification using free responses,
Science China Technological Sciences, ISSN: 1674-7321, DOI: 10.1007/s11431-014-5622-1, Vol.57, No.9, pp.1698-1706, 2014Streszczenie: Structural health monitoring (SHM) has become a hot and intensively researched field in civil engineering. Thereinto, damage identification play an important role in maintaining structural integrity and safety. Many effective methods have been proposed for damage identification. However, accurate global identification of large real-world structures is not easy due to their complex and often unknown boundary conditions, nonlinear components, insensitivity of global response to localized damages, etc. Furthermore, global identification often requires lots of sensors and involves large number of unknowns. This is costly, rarely feasible in practice, and usually yields severely ill-conditioned identification problems. Substructuring approach is a possible solution: substructuring methods can focus on local small substructures; they need only a few sensors placed on the substructure and yield smaller and numerically much more feasible identification problems. This paper proposed an improved substructure method using local free response for substructure damage identification. The virtual supports are constructed by Substructure Isolation Method (SIM) using the linear combination of the substructural responses. The influence of the global errors is isolated by adding the virtual supports on the main degree of freedoms (DOFs) of the substructure. Through the correlation analysis, the substructural modes are selected and used for damage identification of the substructure. A plain model of cable stayed bridge is used for the verification of the proposed method. Słowa kluczowe: structural health monitoring (SHM), damage identification, substructure, cable stayed bridge, free response Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Jankowski Ł. | - | IPPT PAN | Ou J. | - | Dalian University of Technology (CN) |
| | 25p. |
37. |
Hou J.^{♦}, Jankowski Ł., Ou J.^{♦}, Structural health monitoring based on combined structural global and local frequencies,
MATHEMATICAL PROBLEMS IN ENGINEERING, ISSN: 1024-123X, DOI: 10.1155/2014/405784, Vol.2014, pp.405784-1-13, 2014Streszczenie: This paper presents a parameter estimation method for Structural Health Monitoring based on the combined measured structural global frequencies and structural local frequencies. First, the global test is experimented to obtain the low order modes which can reflect the global information of the structure. Secondly, the mass is added on the member of structure to increase the local dynamic characteristic and to make the member have local primary frequency, which belongs to structural local frequency and is sensitive to local parameters. Then the parameters of the structure can be optimized accurately using the combined structural global frequencies and structural local frequencies. The effectiveness and accuracy of the proposed method are verified by the experiment of a space truss. Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Jankowski Ł. | - | IPPT PAN | Ou J. | - | Dalian University of Technology (CN) |
| | 25p. |
38. |
Zhang Q., Duan Z.^{♦}, Jankowski Ł., Substructure damages and excitations identification using measured response,
APPLIED MECHANICS AND MATERIALS, ISSN: 1662-7482, DOI: 10.4028/www.scientific.net/AMM.501-504.843, Vol.501-504, pp.843-846, 2014Streszczenie: This paper proposes a methodology on simultaneous identification of substructure excitation and damage. Structural damages are simulated by virtual distortions which are computed together with unknown excitations using the measured responses through the intact isolated substructure model; the damage extent and type is then recovered by a comparison of the virtual and actual distortions. Unknown factors are reduced greatly which allows the method to be applied on practical complex structure. The computational cost is cutoff sharply. A damaged nonlinearity aluminum beam is used in the experimental verification. Both load and damage are successfully identified. Słowa kluczowe: Damage Identification, Load Identification, Structural Health Monitoring (SHM), Substructure Afiliacje autorów:
Zhang Q. | - | IPPT PAN | Duan Z. | - | Shenzhen Graduate School of Harbin Institute of Technology (CN) | Jankowski Ł. | - | IPPT PAN |
| | 7p. |
39. |
Hou J.^{♦}, Jankowski Ł., Ou J.^{♦}, An online substructure identification method for local structural health monitoring,
SMART MATERIALS AND STRUCTURES, ISSN: 0964-1726, DOI: 10.1088/0964-1726/22/9/095017, Vol.22, No.9, pp.095017-1-11, 2013Streszczenie: This paper proposes a substructure isolation method, which uses time series of measured local response for online monitoring of substructures. The proposed monitoring process consists of two key steps: construction of the isolated substructure, and its identification. The isolated substructure is an independent virtual structure, which is numerically isolated from the global structure by placing virtual supports on the interface. First, the isolated substructure is constructed by a specific linear combination of time series of its measured local responses. Then, the isolated substructure is identified using its local natural frequencies extracted from the combined responses. The substructure is assumed to be linear; the outside part of the global structure can have any characteristics. The method has no requirements on the initial state of the structure, and so the process can be carried out repetitively for online monitoring. Online isolation and monitoring is illustrated in a numerical example with a frame model, and then verified in a cantilever beam experiment. Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Jankowski Ł. | - | IPPT PAN | Ou J. | - | Dalian University of Technology (CN) |
| | 40p. |
40. |
Zhang Q., Jankowski Ł., Duan Z.^{♦}, Simultaneous identification of moving vehicles and bridge damages considering road rough surface,
MATHEMATICAL PROBLEMS IN ENGINEERING, ISSN: 1024-123X, DOI: 10.1155/2013/963424, Vol.2013, pp.963424-1-12, 2013Streszczenie: A method for the simultaneous identification of moving vehicles and the damages of the supporting structure from measured responses is presented. A two-axle vehicle model with two degrees of freedom (DOF) is adopted. The extent of the damage and the vehicle parameters were chosen as the optimisation variables, which allow ill conditioning to be avoided and decrease the number of sensors required. The identification is performed by minimising the distance between the measured responses and the computed responses to given optimisation variables. The virtual distortion method (VDM) was used, such that the response of the damaged structure can be computed from comparison with the intact structure subjected to the same vehicle excitation and to the response-coupled virtual distortions. These are related to the optimisation variables by the system impulse response matrix and are expressed by a linear system, which allowed both types of optimisation variables to be treated in a unified way. The numerical cost is reduced by using a moving influence matrix. The adjoint variable method is used for fast sensitivity analysis. A three-span bridge numerical example is presented, where the identification was verified with 5% root mean square (RMS) measurement, and model, error whilst also considering the surface roughness of the road. Afiliacje autorów:
Zhang Q. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN | Duan Z. | - | Shenzhen Graduate School of Harbin Institute of Technology (CN) |
| | 30p. |
41. |
Hou J.^{♦}, Jankowski Ł., Ou J.^{♦}, Structural damage identification by adding virtual masses,
STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, ISSN: 1615-147X, DOI: 10.1007/s00158-012-0879-0, Vol.48, No.1, pp.59-72, 2013Streszczenie: This paper presents a method for damage identification by adding virtual masses to the structure in order to increase its sensitivity to local damages. The main concept is based on the Virtual Distortion Method (VDM), which is a fast structural reanalysis method that employs virtual distortions or pseudo loads to simulate structural modifications. In this paper, the structure with an added virtual mass is called the virtual structure. First, the acceleration frequency response of the virtual structure is constructed numerically by the VDM using local dynamic data measured only by a single excitation sensor and a single acceleration sensor. Second, the value of the additional mass is determined via sensitivity analysis of the constructed frequency responses of the virtual structure with respect to damage parameters; only the natural frequencies with high sensitivity are selected. This process is repeated for all the considered placements of the virtual mass. At last, the selected natural frequencies of all the virtual structures are used together for damage identification of the real structure. A finite element (FE) model of a plane frame is used to introduce and verify the proposed method. The damage can be identified precisely and effectively even under simulated 5 % Gaussian noise pollution. Słowa kluczowe: Structural health monitoring (SHM), Damage identification, Virtual distortion method (VDM), Virtual mass, Sensitivity analysis Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Jankowski Ł. | - | IPPT PAN | Ou J. | - | Dalian University of Technology (CN) |
| | 30p. |
42. |
Zhang Q., Hou J.^{♦}, Duan Z.^{♦}, Jankowski Ł., Substructural virtual distortion method for damage identification,
Engineering Mechanics, ISSN: 1000-4750, DOI: 10.6052/j.issn.1000-4750.2012.08.0613, Vol.30, No.12, pp.176-182, 2013Streszczenie: 针对大型土木结构损伤识别优化效率低的问题，提出了子结构虚拟变形方法。虚拟变形方法是一种结构
快速重分析的方法，该方法利用单元的虚拟变形模拟结构的损伤，可以在不重新建立有限元模型的情况下，快速
计算出结构参数改变后的结构响应。该文基于虚拟变形法的基本思想，对子结构的刚度矩阵进行分解和对损伤后
结构运动方程进行整理，推导出利用子结构的虚拟变形刻画损伤的方法，扩展了虚拟变形方法的适用范围；并且
给出了虚拟变形和结构响应的相关性计算公式，通过相关性分析提取主要的虚拟变形，减少参与计算的子结构虚
拟变形的数目，提高计算效率；最后利用一个五十层框架的数值仿真验证方法的有效性 Afiliacje autorów:
Zhang Q. | - | IPPT PAN | Hou J. | - | Dalian University of Technology (CN) | Duan Z. | - | Shenzhen Graduate School of Harbin Institute of Technology (CN) | Jankowski Ł. | - | IPPT PAN |
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43. |
Suwała G., Biczyk J.^{♦}, Jankowski Ł., Nonparametric identification of added masses in frequency domain: a numerical study,
Prace IPPT - IFTR Reports, ISSN: 2299-3657, Vol.4f, pp.1-6, 2013Streszczenie: This paper presents a theoretical derivation and reports on a numerical verification of a model-free method for identification of added masses in truss structures. No parametric numerical model of the monitored structure is required, so that there is no need for initial model updating and fine tuning. This is a continuation and an improvement of a previous research that resulted in a time-domain identification method, which was tested to be accurate but very time-consuming. A general methodology is briefly introduced, including the inverse problem, and a numerical verification is reported. The aim of the numerical study is to test the accuracy of the proposed method and its sensitivity to various parameters (such as simulated measurement noise and decay rate of the exponential FFT window) in a numerically controlled environment. The verification uses a finite element model of the same real structure that was tested with the time-domain version of the approach. A natural further step is a lab verification based on experimental data. Afiliacje autorów:
Suwała G. | - | IPPT PAN | Biczyk J. | - | Adaptronica Sp. z o.o. (PL) | Jankowski Ł. | - | IPPT PAN |
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44. |
Hou J.^{♦}, Ou J.^{♦}, Jankowski Ł., Model updating experiment of space truss using global and local dynamic information,
JOURNAL OF VIBRATION AND SHOCK, ISSN: 1000-3835, Vol.32, No.16, pp.100-105, 2013Streszczenie: 由于土木工程结构的复杂性、传感器测点的有限性以及局部损伤的不敏感性等问题，大型结构的模型修正存在一定困难。针对空间桁架结构，为克服上述问题，对其进行整体和局部的动力测试试验，然后联合实测的结构整体和局部动态信息进行模型修正：首先进行空间桁架整体的动力测试试验，获得反应整体特性的低阶模态；然后为了提高局部杆件的动态特性，在杆件上附加一定质量，获得附加质量后杆件的局部主频率，并在各类杆件中选取一定数目进行动态测试；最后联合所有实测结构整体的低阶模态和杆件的局部主频率，对空间桁架结构进行模型修正。修正后的模态参数与实测模态吻合良好，验证了方法的有效性。 Słowa kluczowe: 结构健康监测, 模型修正, 桁架, 频率, 振型 Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Ou J. | - | Dalian University of Technology (CN) | Jankowski Ł. | - | IPPT PAN |
| |
45. |
Zhang Q., Duan Z.^{♦}, Jankowski Ł., Fast simultaneous identification of structural damages and loads,
JOURNAL OF VIBRATION AND SHOCK, ISSN: 1000-3835, Vol.32, No.2, pp.33-38, 2013Streszczenie: 本文仅以损伤因子为优化变量，提出一种结构损伤和荷载同步识别的方法。首先通过时域荷载识别的方法将未知荷载转化为损伤因子的函数，将近似荷载作用下的结构响应和实测响应的平方距离作为目标函数，从而降低了需要识别未知参数的数目；然后在目标函数的计算过程中，利用虚拟变形法（VDM）可进行结构快速重分析的思想，快速构造给定损伤因子下系统的脉冲响应，避免每步迭代重新集装系统矩阵，并通过荷载形函数方法进一步提高荷载识别的效率；最后利用二次多项式插值近似结构每个时刻的响应方法和推导对应目标函数的梯度表达式来提高优化搜索的速度。本文利用刚架模型进行数值模拟，准确识别了结构中柱子单元刚度损伤、附加质量以及梁上的未知移动荷载，并通过一个悬臂梁试验进一步验证所提出方法的准确性和可行性。 Słowa kluczowe: 结构健康监测, 荷载识别, 损伤识别, 虚拟变形法(VDM) Afiliacje autorów:
Zhang Q. | - | IPPT PAN | Duan Z. | - | Shenzhen Graduate School of Harbin Institute of Technology (CN) | Jankowski Ł. | - | IPPT PAN |
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46. |
Hou J.^{♦}, Ou J.^{♦}, Jankowski Ł., The experiment of substructure isolation and identification using local time series,
Engineering Mechanics, ISSN: 1000-4750, DOI: 10.6052/j.issn.1000-4750.2011.10.0722, Vol.30, No.4, pp.129-135, 2013Streszczenie: 针对大型复杂结构的整体监测常常面临测量信息不足等困难,提出只利用局部动态响应进行子结构损伤识别的约束子结构方法。约束子结构方法是通过子结构响应的卷积组合限制子结构边界的响应为零,来实现施加虚拟支座,从而将子结构分离出整体,然后利用构造的相应子结构内部响应,进行子结构损伤识别。该文利用先分段提取结构响应的子时间序列,再延时排列Toeplitz矩阵的方式,使基于不同响应的构造约束子结构的方程具有相同表达式,统一了约束子结构方法的基本思想。通过测量悬臂梁的局部动力响应,利用局部响应的时间序列实现了子结构的快速准确地分离和识别,验证了方法的实用性和有效性。 Słowa kluczowe: 结构健康监测, 损伤识别, 子结构, 时间序列, 脉冲响应 Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Ou J. | - | Dalian University of Technology (CN) | Jankowski Ł. | - | IPPT PAN |
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47. |
Hou J.^{♦}, Ou J.^{♦}, Jankowski Ł., Structural damage identification using additional virtual supports,
JOURNAL OF VIBRATION AND SHOCK, ISSN: 1000-3835, Vol.32, No.10, pp.118-129, 2013Streszczenie: 针对土木工程中实测模态相对较少，很难进行大型结构的损伤识别的困难，提出附加虚拟支座的损伤识别方法。该方法利用约束子结构方法在结构上附加虚拟支座来增加结构形式的方法，增加识别模态的数量，从而实现结构的准确损伤识别。约束子结构方法的基本思想是通过响应的卷积组合为零将传感器转化为虚拟支座。将附加虚拟支座后的结构定义为虚拟结构，每个虚拟支座对应一个虚拟结构，那么在结构上不同位置附加虚拟支座，则可以获得多个虚拟结构的模态；联合所有虚拟结构和对应的频率即可准确快速的识别出整体结构的损伤。最后通过三层空间框架模型验证方法的有效性。 Słowa kluczowe: 结构健康监测, 损伤识别, 约束子结构方法, 灵敏度分析, 频率 Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Ou J. | - | Dalian University of Technology (CN) | Jankowski Ł. | - | IPPT PAN |
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48. |
Zhang Q., Jankowski Ł., Duan Z.^{♦}, Simultaneous identification of excitation time histories and parametrized structural damages,
MECHANICAL SYSTEMS AND SIGNAL PROCESSING, ISSN: 0888-3270, DOI: 10.1016/j.ymssp.2012.06.018, Vol.33, pp.56-68, 2012Streszczenie: This paper presents and experimentally verifies an effective method for simultaneous identification of excitations and damages, which are two crucial factors in structural health monitoring and which often coexist in practice. The unknowns are identified by minimizing a time-domain square distance between the measured and the computed responses. Even though both damage and excitation are unknown, only damage parameters are treated here as the optimization variables: given the damage, the excitation is uniquely determined from the measured responses. As a result, all unknowns are of the same type, which allows standard optimization algorithms to be used and obviates the need for two-step procedures. The sensitivity analysis is facilitated by interpolating in each iteration the relation between structural responses and damage parameters. The numerical costs are further decreased by the fast reanalysis approach of the virtual distortion method (VDM), which is used to compute exact impulse responses of the damaged structure. The proposed methodology is verified both numerically (using a multi-span frame) and experimentally (using a cantilever beam). Stiffness-related damages and mass-related modifications are identified successfully together with the three tested types of external excitation. Słowa kluczowe: Structural health monitoring, Load identification, Damage identification, Virtual distortion method (VDM) Afiliacje autorów:
Zhang Q. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN | Duan Z. | - | Shenzhen Graduate School of Harbin Institute of Technology (CN) |
| | 45p. |
49. |
Hou J.^{♦}, Jankowski Ł., Ou J.^{♦}, Experimental study of the substructure isolation method for local health monitoring,
STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.443, Vol.19, No.4, pp.491-510, 2012Streszczenie: This paper extends and studies experimentally the substructure isolation method. Local health monitoring is significant for large and complex structures, since it costs less and can be easily implemented compared with global analysis. In contrast to other substructuring methods, in which the substructure is separated from the global structure, but coupled to it via the interface forces, the substructure isolation method isolates the substructure into an independent structure by placing virtual fixed supports on the interface. Model updating or damage identification can be then performed locally and precisely using the constructed responses of the isolated substructure and any of the existing methods aimed originally at global identification. This paper discusses and further extends the approach to improve its performance in real applications. A new type of virtual interface support (free support) is proposed for isolation. Relaxation of the original requirements concerning the type and placement of the isolating excitations is discussed. Previously, the method relied on the linearity of the global structure; here, only the substructure is required to be linear, the global structure besides the substructure can be non-linear, yielding, changing or unknown. A damaged cantilever beam is used in the experimental study. Up to three modified global structures with the same substructure are used to test the robustness of the isolation with respect to unknown modifications and non-linearities of the outside structure. Two typical global health monitoring methods are applied at the substructural level. A comparison with the results obtained from a generic substructure separation method is offered. Słowa kluczowe: Structural Health Monitoring (SHM), substructure isolation method, substructural identification, virtual distortion method (VDM), local monitoring, virtual supports Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Jankowski Ł. | - | IPPT PAN | Ou J. | - | Dalian University of Technology (CN) |
| | 30p. |
50. |
Suwała G., Jankowski Ł., A model-free method for identiﬁcation of mass modiﬁcations,
STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.417, Vol.19, No.2, pp.216-230, 2012Streszczenie: In this paper, a model-free methodology for off-line identification of modifications of structural mass is proposed and verified experimentally. The methodology of the virtual distortion method is used: the modifications are modeled by the equivalent pseudo-loads that act in the related degrees of freedom of the unmodified structure; their influence on the response is computed using a convolution of the pseudo-loads with the experimentally obtained local impulse responses. As a result, experimentally measured data are directly used to model the response of the modified structure in a non-parametric way. The approach obviates the need for a parametric numerical model of the structure and for laborious initial updating of its parameters. Moreover, no topological information about the structure is required, besides potential locations of the modifications. The identification is stated as a problem of minimization of the discrepancy between the measured and the modeled responses of the modified structure. The formulation allows the adjoint variable method to be used for a quick first- and second-order sensitivity analysis, so that Hessian-based optimization algorithms can be used for fast convergence. The proposed methodology was experimentally verified using a 3D truss structure with 70 elements. Mass modifications in a single node and in two nodes were considered. Given the initially measured local impulse responses, a single sensor and single excitation were sufficient for the identification. Słowa kluczowe: mass identification, structural health monitoring (SHM), virtual distortion method (VDM), model-free, non-parametric modeling, adjoint variable method Afiliacje autorów:
Suwała G. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 30p. |
51. |
Zhang Q., Duan Z.^{♦}, Jankowski Ł., The study on simultaneous identification of structural damages and loads,
Engineering Mechanics, ISSN: 1000-4750, DOI: 10.6052/j.issn.1000-4750.2011.05.0275, Vol.29, No.12, pp.316-321, 2012Streszczenie: 针对结构中同时存在未知损伤和荷载的情况，基于虚拟变形法(VDM)发展一种两者共同识别的时域方法。VDM方法利用虚拟变形模拟结构损伤，可快速计算模型改变后的响应。该文首先结合有限元理论把VDM方法拓展到具有多个单元变形的结构中；然后考虑结构存在未知荷载时，利用未损伤理论模型同时识别荷载和虚拟变形，继而由虚拟变形和单元实际变形的关系来识别判断损伤类型和识别损伤大小；最后通过一个悬臂梁的试验进行方法验证，试验中未知荷载和损伤(包括其类型和大小)均能够被有效识别，并利用提出的移动时间窗和荷载形函数方法实现损伤与荷载的在线识别。 Słowa kluczowe: 结构健康监测, 虚拟变形法(VDM), 荷载识别, 损伤识别, 荷载形函数 Afiliacje autorów:
Zhang Q. | - | IPPT PAN | Duan Z. | - | Shenzhen Graduate School of Harbin Institute of Technology (CN) | Jankowski Ł. | - | IPPT PAN |
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52. |
Hou J.^{♦}, Ou J.^{♦}, Jankowski Ł., The study and experiment of substructure damage identification based on local primary frequency,
Engineering Mechanics, ISSN: 1000-4750, DOI: 10.6052/j.issn.1000-4750.2010.12.0928, Vol.29, No.9, pp.99-105, 2012Streszczenie: 针对大型复杂结构的整体监测常常面临测量信息不足等困难,提出只利用局部动态响应进行子结构损伤识别的局部主频率方法.子结构的局部主频率指：如果整体模态中含有以局部子结构位移为主的模态,即等价于在局部激励作用下,整体结构的振动主要体现为子结构的振动,并且主要以这阶局部模态振动为主,那么对应的该阶频率即定义为子结构的局部主频率.局部主频率主要反映子结构的局部特性,对子结构损伤的灵敏度高,所以只利用局部主频率就可以识别子结构.当子结构特征不明显时,提出通过附加质量使子结构具有局部主频率的有效方法.该文进行了大型空间桁架的局部动力测试试验,试验中通过附加质量使杆件子结构具有局部主频率,并能准确地识别出杆件损伤的位置和程度. Słowa kluczowe: 结构健康监测, 损伤识别, 子结构, 模态分析, 频率响应 Afiliacje autorów:
Hou J. | - | Dalian University of Technology (CN) | Ou J. | - | Dalian University of Technology (CN) | Jankowski Ł. | - | IPPT PAN |
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53. |
Zhang Q., Duan Z.^{♦}, Jankowski Ł., Parameter identification of moving vehicles considering road roughness of bridge,
Journal of Vibration Engineering, ISSN: 1004-4523, Vol.25, No.2, pp.146-153, 2012Streszczenie: 基于虚拟变形(VDM)方法中移动动态影响矩阵的概念,利用双自由度质量-弹簧阻尼模型模拟移动车辆,系统推导和阐述了车-桥耦合系统中粗糙路面上移动体参数的识别方法。以移动体参数的修正因子为优化变量,通过最小化桥体结构实测响应和计算响应的平方距离进行识别,识别精度高,对噪声鲁棒性强,且较少的传感器就能识别多个移动体参数。利用移动动态影响矩阵,每步优化中无需时时重构系统参数矩阵,计算效率高。利用一个三跨连续梁模型验证该方法的有效性,在5%的噪声影响下,利用一个传感器可以准确地识别多个移动体参数和移动荷载。此外,通过比较平坦路面与粗糙路面上的移动体参数的识别方法和结果,结合车体参数的灵敏度分析,说明了路面粗糙度、移动体参数对结构响应的影响及不同情况下参数识别中优化变量的选取原则。 Słowa kluczowe: 结构健康监测, 移动车辆(荷载)识别, 虚拟变形法(VDM), 影响矩阵, 粗糙路面 Afiliacje autorów:
Zhang Q. | - | IPPT PAN | Duan Z. | - | Shenzhen Graduate School of Harbin Institute of Technology (CN) | Jankowski Ł. | - | IPPT PAN |
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54. |
Jilin Hou^{♦}, Jankowski Ł., Jinping Ou^{♦}, A substructure isolation method for local structural health monitoring,
STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.389, Vol.18, No.6, pp.601-618, 2011Streszczenie: This paper describes an effective method of substructure isolation for local structural health monitoring (SHM). In practice, often only a small part of a larger structure is critical and needs monitoring. However, typical low-frequency SHM methods require modeling and analysis of the global structure, which can be costly, time-consuming and error-prone. The proposed approach is based on the virtual distortion method (VDM) and uses force distortions to model fixed supports in the boundary nodes to isolate the considered substructure from influences of the rest of the structure. Therefore, given an excitation of the substructure and the measured response of the global structure, the response of the substructure treated as fixed supported can be computed. Local-only monitoring is then possible using virtually any of the existing methods. However, consistently with the isolation methodology, strain distortions are used here for modeling of damages of the isolated substructure. The discrete adjoint variable method is used for the first time within the framework of the VDM in order to perform fast analytical sensitivity analysis and improve the computational effectiveness of the damage identification by one order of magnitude. A numerical example of a frame-truss with 5 and 10% noise level and an experiment of a cantilever beam are presented to validate the isolation methodology. Słowa kluczowe: substructure isolation, damage identification, virtual distortion method (VDM), structural health monitoring, adjoint variable method Afiliacje autorów:
Jilin Hou | - | inna afiliacja | Jankowski Ł. | - | IPPT PAN | Jinping Ou | - | inna afiliacja |
| | 30p. |
55. |
Zhang Q., Duan Z.^{♦}, Jankowski Ł., Moving mass identification of vehicle-bridge coupled system based on virtual distortion method,
Chinese Journal of Theoretical and Applied Mechanics, ISSN: 0459-1879, DOI: 10.6052/0459-1879-2011-3-lxxb2009-481, Vol.43, No.3, pp.598-610, 2011Streszczenie: 利用双自由度质量-弹簧阻尼模型模拟移动车辆, 并基于虚拟变形(VDM)方法的结构快速重分 析思想, 提出一种车-桥耦合系统的移动质量快速识别的有效方法. 该方法以双自由度车体模 型的质量为变量, 通过最小化桥体结构实测响应和计算响应的平方距离来识别移动质量 (载荷), 避免了识别载荷时常遇到的病态问题, 对噪声鲁棒性强, 且需要传感器信息少. 每步优化 中, 利用在VDM方法基础上提出的移动动态影响矩阵概念, 无需时时重构车-桥耦合系统的时 变系统参数矩阵, 显著提高了计算效率. 利用数值框架梁模型, 通过比较不同车辆简化模型 对移动体质量及等效移动载荷的识别效果, 验证了该方法的可行性和有效性, 即使在5% 的噪声影响下, 利用一个传感器可以准确地识别多个移动体的质量. Słowa kluczowe: 结构健康监测, 移动车辆识别, 结构重分析, 虚拟变形法, 影响矩阵 Afiliacje autorów:
Zhang Q. | - | IPPT PAN | Duan Z. | - | Shenzhen Graduate School of Harbin Institute of Technology (CN) | Jankowski Ł. | - | IPPT PAN |
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56. |
Zhang Q., Duan Z.^{♦}, Jankowski Ł., Wang F.^{♦}, Experimental validation of a fast dynamic load identification method based on load shape function,
JOURNAL OF VIBRATION AND SHOCK, ISSN: 1000-3835, Vol.30, No.9, pp.98-102, 154, 2011Streszczenie: 在动态荷载识别中常常由于矩阵的病态性影响识别的精度，利用有限元理论中的形函数逼近荷载曲线，将识别离散的荷载历程转化为计算有限的形函数权重，从而显著改善反卷积法识别荷载中存在的采样时间长或采样频率高时数值求解困难的问题；并能改善反问题的病态性，提高对噪音的鲁棒性。一个连续梁的数值算例比较验证了该方法在5%的高斯噪声影响下能精确地识别未知荷载。悬臂梁试验中，通过实测的结构动态响应，在移动时间窗内利用荷载形函数方法可以实现激励的在线识别。 Słowa kluczowe: 结构健康监测, 荷载识别, 在线识别, 反卷积法, 形函数 Afiliacje autorów:
Zhang Q. | - | IPPT PAN | Duan Z. | - | Shenzhen Graduate School of Harbin Institute of Technology (CN) | Jankowski Ł. | - | IPPT PAN | Wang F. | - | Dalian University of Technology (CN) |
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57. |
Zhang Q., Jankowski Ł., Duan Z.^{♦}, Simultaneous identification of moving masses and structural damage,
STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, ISSN: 1615-147X, DOI: 10.1007/s00158-010-0528-4, Vol.42, pp.907-922, 2010Streszczenie: A method for simultaneous identification of moving masses and damages of the supporting structure from measured responses is presented. The interaction forces between the masses and the structure are used as excitation. Masses and damage extents are used as the optimization variables; compared to the approaches based on identification of the interaction forces, it allows ill-conditioning to be avoided and decreases the number of required sensors. The virtual distortion method is used; the damaged structure is modeled by the intact structure subjected to response-coupled virtual distortions and moving forces. These are related to the optimization variables via a linear system, which allows the optimization variables of both kinds to be treated in a unified way. A moving dynamic influence matrix is introduced to reduce the numerical costs. The adjoint variable method is used for fast sensitivity analysis. A numerical experiment of a three-span beam with 10% rms measurement error and three types of model errors is presented. Słowa kluczowe: Moving load identification, Damage identification, Mass identification, Virtual distortion method (VDM), Structural health monitoring (SHM) Afiliacje autorów:
Zhang Q. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN | Duan Z. | - | Shenzhen Graduate School of Harbin Institute of Technology (CN) |
| | 32p. |
58. |
Zhang Q., Jankowski Ł., Duan Z.^{♦}, Identification of coexistent load and damage,
STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, ISSN: 1615-147X, DOI: 10.1007/s00158-009-0421-1, Vol.41, pp.243-253, 2010Streszczenie: Load reconstruction and damage identification are crucial problems in structural health monitoring. However, it seems there is not much investigation on identification of coexistent load and damage, although in practice they usually exist together. This paper presents a methodology to solve this problem based on the Virtual Distortion Method. A damaged structure is modeled by an equivalent intact structure subjected to the same loads and to virtual distortions which model the damages. The measured structural response is used to identify the loads, the distortions and to recover the stress-strain relationship of the damaged elements. This way both the damage type and extent are identified. The approach can be used off-line and online by repetitive applications in a moving time window. A numerical experiment of a truss with 5% measurement error validates that the two tested damage types (constant stiffness reduction and breathing crack) can be identified along with the loads. Słowa kluczowe: Structural health monitoring, Load identification, Damage identification, Virtual Distortion Method (VDM) Afiliacje autorów:
Zhang Q. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN | Duan Z. | - | Shenzhen Graduate School of Harbin Institute of Technology (CN) |
| | 32p. |
59. |
Zhang Q., Duan Z.^{♦}, Jankowski Ł., Moving mass identification based on Virtual Distortion Method,
Journal of Vibration Engineering, ISSN: 1004-4523, Vol.23, No.5, pp.494-501, 2010Streszczenie: 在车-桥耦合系统的移动质量（荷载）识别反问题中,识别移动质量会面临重构系统、优化缓慢的问题;而若直接识别移动荷载常常会遇到病态问题且对噪音敏感。针对这些缺陷,根据虚拟变形法（VDM）的结构快速重分析思想,提出移动动态影响矩阵,实现利用较少的传感器即可快速而准确地识别移动质量（荷载）。以移动质量为优化变量,避免了识别荷载常遇到的病态问题,对噪音鲁棒性强;且需要传感器信息少。每步优化中,利用移动动态影响矩阵,无需时时重构车-桥耦合系统的时变系统参数矩阵,优化效率高。VDM方法的思想是将实际结构的响应计算转化为初始结构模型在相同外荷载作用下的响应,与在结构模型发生改变的位置施加相关的虚拟变形或虚拟力引起的响应的线性叠加。通过简支梁模型和框架梁模型验证了该方法的可行性和有效性,即使在5%的噪声影响下,利用一个传感器就可以很好地识别多个移动质量。 Słowa kluczowe: 结构健康监测, 结构重分析, 影响矩阵 Afiliacje autorów:
Zhang Q. | - | IPPT PAN | Duan Z. | - | Shenzhen Graduate School of Harbin Institute of Technology (CN) | Jankowski Ł. | - | IPPT PAN |
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60. |
Jankowski Ł., Off-line identification of dynamic loads,
STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, ISSN: 1615-147X, DOI: 10.1007/s00158-008-0249-0, Vol.37, No.6, pp.609-623, 2009Streszczenie: This paper considers off-line identification of spatial and temporal characteristics of a dynamic load, and is focused on the case of a limited number of sensors. Both elastic and elasto-plastic structural behaviours are taken into account. The identification is performed off-line, based on optimisation of modelled local structural responses, and—in the case of limited number of sensors—identifies an observationally equivalent load, which in a given sense optimally approximates the actual load. Compared to previous researches this approach allows to identify general dynamic loads of unknown locations, including multiple impacts and moving loads, and gives more insight into the identification process by distinguishing between the reconstructible and unreconstructible load components. Additionally, the problem of optimum sensor location is discussed. Słowa kluczowe: Load identification, Inverse dynamics, Elasto-plastic structures, Black box, Forensic engineering Afiliacje autorów:
| | 32p. |
61. |
Suwała G., Jankowski Ł., A model-less method for added mass identification,
SOLID STATE PHENOMENA, ISSN: 1012-0394, DOI: 10.4028/www.scientific.net/SSP.147-149.570, Vol.147-149, pp.570-575, 2009Streszczenie: This paper present and validates experimentally a model-less methodology for off-line identification of modifications of nodal masses. The proposed approach is entirely based on experimentally measured data; hence no numerical modeling and tedious fine-tuning of the model are necessary. The influence of the added mass is modeled using virtual distortion forces and experimentally obtained system transfer matrices. The identification amounts to solving an optimization problem of minimizing the mean square distance between measured and modeled structural responses, the latter is based on previously recorded responses of the unaffected structure. Słowa kluczowe: mass identification, model-less SHM, virtual distortion method (VDM), inverse dynamics Afiliacje autorów:
Suwała G. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 20p. |
62. |
Mikułowski G., Jankowski Ł., Adaptive Landing Gear: optimum control strategy and potential for improvement,
SHOCK AND VIBRATION, ISSN: 1070-9622, DOI: 10.3233/SAV-2009-0460, Vol.16, No.2, pp.175-194, 2009Streszczenie: An adaptive landing gear is a landing gear (LG) capable of active adaptation to particular landing conditions by means of controlled hydraulic force. The objective of the adaptive control is to mitigate the peak force transferred to the aircraft structure during touch-down, and thus to limit the structural fatigue factor. This paper investigates the ultimate limits for improvement due to various strategies of active control. Five strategies are proposed and investigated numerically using a~validated model of a real, passive landing gear as a reference. Potential for improvement is estimated statistically in terms of the mean and median (significant) peak strut forces as well as in terms of the extended safe sinking velocity range. Three control strategies are verified experimentally using a laboratory test stand. Słowa kluczowe: Adaptive landing gear, adaptive impact absorption, shock absorber, load mitigation Afiliacje autorów:
Mikułowski G. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 20p. |
63. |
Szolc T., Jankowski Ł., Active control of transient torsional vibrations due to run-up of a rotor machine driven by the electric motor,
VIBRATIONS IN PHYSICAL SYSTEMS, ISSN: 0860-6897, Vol.23, pp.341-346, 2008Streszczenie: In the paper active control of transient torsional vibrations induced by the electric motor during run-ups of the radial compressor drive system is performed by means of couplings with the magneto-rheological fluid. The main purpose of these studies is a minimisation of vibration amplitudes in order to increase the fatigue durability of the most responsible elements. The theoretical investigations are based on a hybrid structural model of the vibrating mechanical system and sensitivity analysis of the response with respect to the damping characteristics of the control couplings. Słowa kluczowe: active control, transient vibrations, drive system, electric motor Afiliacje autorów:
Szolc T. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
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64. |
Jankowski Ł., Wikło M., Holnicki-Szulc J., Robust post-accident reconstruction of loading forces,
KEY ENGINEERING MATERIALS, ISSN: 1662-9795, DOI: 10.4028/www.scientific.net/KEM.347.659, Vol.347, pp.659-664, 2007Streszczenie: The paper presents a novel methodology for robust post-accident reconstruction of spatial and temporal characteristics of the load. The methodology is based on analysis of local structural response, and identifies an observationally equivalent load, which in a given sense optimally approximates the real load. Compared to previous researches this approach allows to use a limited number of sensors to reconstruct general dynamic loads of unknown location including multiple impacts and moving loads. Additionally, the problem of optimum sensor location is studied. Słowa kluczowe: impact identification, inverse dynamics, smart systems, structural health monitoring Afiliacje autorów:
Jankowski Ł. | - | IPPT PAN | Wikło M. | - | IPPT PAN | Holnicki-Szulc J. | - | IPPT PAN |
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