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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.
Qingxia Zhang; Jilin Hou; Zhongdong Duan; Łukasz Jankowski; Xiaoyang Hu. Road Roughness Estimation Based on the Vehicle Frequency Response Function. Actuators 2021, 10, 89 .
AMA StyleQingxia Zhang, Jilin Hou, Zhongdong Duan, Łukasz Jankowski, Xiaoyang Hu. Road Roughness Estimation Based on the Vehicle Frequency Response Function. Actuators. 2021; 10 (5):89.
Chicago/Turabian StyleQingxia Zhang; Jilin Hou; Zhongdong Duan; Łukasz Jankowski; Xiaoyang Hu. 2021. "Road Roughness Estimation Based on the Vehicle Frequency Response Function." Actuators 10, no. 5: 89.
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.
Blazej Poplawski; Grzegorz Mikułowski; Rafał Wiszowaty; Łukasz Jankowski. Mitigation of forced vibrations by semi-active control of local transfer of moments. Mechanical Systems and Signal Processing 2021, 157, 107733 .
AMA StyleBlazej Poplawski, Grzegorz Mikułowski, Rafał Wiszowaty, Łukasz Jankowski. Mitigation of forced vibrations by semi-active control of local transfer of moments. Mechanical Systems and Signal Processing. 2021; 157 ():107733.
Chicago/Turabian StyleBlazej Poplawski; Grzegorz Mikułowski; Rafał Wiszowaty; Łukasz Jankowski. 2021. "Mitigation of forced vibrations by semi-active control of local transfer of moments." Mechanical Systems and Signal Processing 157, no. : 107733.
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.
Mariusz Ostrowski; Bartlomiej Blachowski; Blazej Poplawski; Dominik Pisarski; Grzegorz Mikulowski; Lukasz Jankowski. Semi‐active modal control of structures with lockable joints: general methodology and applications. Structural Control and Health Monitoring 2021, 28, e2710 .
AMA StyleMariusz Ostrowski, Bartlomiej Blachowski, Blazej Poplawski, Dominik Pisarski, Grzegorz Mikulowski, Lukasz Jankowski. Semi‐active modal control of structures with lockable joints: general methodology and applications. Structural Control and Health Monitoring. 2021; 28 (5):e2710.
Chicago/Turabian StyleMariusz Ostrowski; Bartlomiej Blachowski; Blazej Poplawski; Dominik Pisarski; Grzegorz Mikulowski; Lukasz Jankowski. 2021. "Semi‐active modal control of structures with lockable joints: general methodology and applications." Structural Control and Health Monitoring 28, no. 5: e2710.
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 ndings, 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 conrm the accuracy of the adopted algorithm parameters and reveal the sensor locations that provide the best control effectiveness.
Grzegorz Mikułowski; Błażej Popławski; Łukasz Jankowski. Semi-active vibration control based on switchable transfer of bending moments: study and experimental validation of control performance. Smart Materials and Structures 2021, 30, 045005 .
AMA StyleGrzegorz Mikułowski, Błażej Popławski, Łukasz Jankowski. Semi-active vibration control based on switchable transfer of bending moments: study and experimental validation of control performance. Smart Materials and Structures. 2021; 30 (4):045005.
Chicago/Turabian StyleGrzegorz Mikułowski; Błażej Popławski; Łukasz Jankowski. 2021. "Semi-active vibration control based on switchable transfer of bending moments: study and experimental validation of control performance." Smart Materials and Structures 30, no. 4: 045005.
Performance of any Structural Health Monitoring (SHM) system strongly depends on a set of sensors which are distributed over the structure under investigation. Optimal deployment of sensors on large scale structures such as tied-arch bridges is quite a challenging problem. Moreover, deployment of a sensor network consisting of different types of sensors (accelerometers, inclinometers or strain gauges) over a large scale bridge renders the task of optimization even more demanding. In the present study, a conventional sensor placement method for distribution of a homogenous sensor network is expanded to the heterogeneous case. First, the basic equations governing the estimation error will be recalled. Then, the Fisher information matrix is assembled using normalized translational and rotational mode shapes. Finally, a computational procedure is proposed which allows optimal sensor positions to be selected among thousands candidate locations. The effectiveness of the proposed strategy is demonstrated using a realistic example of a tied-arch bridge located in Poland.
Bartlomiej Blachowski; Andrzej Swiercz; Mariusz Ostrowski; Piotr Tauzowski; Lukasz Janowski. Multi-type Sensor Placement for Structural Health Monitoring of Tied-Arch Bridges. Lecture Notes in Civil Engineering 2021, 286 -297.
AMA StyleBartlomiej Blachowski, Andrzej Swiercz, Mariusz Ostrowski, Piotr Tauzowski, Lukasz Janowski. Multi-type Sensor Placement for Structural Health Monitoring of Tied-Arch Bridges. Lecture Notes in Civil Engineering. 2021; ():286-297.
Chicago/Turabian StyleBartlomiej Blachowski; Andrzej Swiercz; Mariusz Ostrowski; Piotr Tauzowski; Lukasz Janowski. 2021. "Multi-type Sensor Placement for Structural Health Monitoring of Tied-Arch Bridges." Lecture Notes in Civil Engineering , no. : 286-297.
This contribution presents and tests experimentally a nonparametric approach for indirect identification of 2D paths of moving loads, based on the recorded mechanical response of the loaded structure. This is an inverse problem of load identification. The method to be proposed is based on multicriterial optimization with two complementary criteria. The first criterion is purely mechanical, and it quantifies the misfit between the recorded mechanical response of the structure and its predicted response under a given trajectory. The second criterion is geometric: it represents the heuristic knowledge about the expected geometric regularity characteristics of the load paths (such as related to linear and angular velocity), and in fact it can be considered to be a regularizing criterion. A multicriterial genetic search is used to determine and advance the Pareto front, which helps to strike the balance between the response fit and the geometric regularity of the path. The proposed approach is tested in an experimental laboratory setup of a plate loaded by a line-follower robot and instrumented with a limited number of strain gauges.
Michał Gawlicki; Łukasz Jankowski. Path Identification of a Moving Load Based on Multiobjective Optimization. Lecture Notes in Civil Engineering 2021, 799 -807.
AMA StyleMichał Gawlicki, Łukasz Jankowski. Path Identification of a Moving Load Based on Multiobjective Optimization. Lecture Notes in Civil Engineering. 2021; ():799-807.
Chicago/Turabian StyleMichał Gawlicki; Łukasz Jankowski. 2021. "Path Identification of a Moving Load Based on Multiobjective Optimization." Lecture Notes in Civil Engineering , no. : 799-807.
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.
Michał Gawlicki; Łukasz Jankowski. Trajectory Identification for Moving Loads by Multicriterial Optimization. Sensors 2021, 21, 304 .
AMA StyleMichał Gawlicki, Łukasz Jankowski. Trajectory Identification for Moving Loads by Multicriterial Optimization. Sensors. 2021; 21 (1):304.
Chicago/Turabian StyleMichał Gawlicki; Łukasz Jankowski. 2021. "Trajectory Identification for Moving Loads by Multicriterial Optimization." Sensors 21, no. 1: 304.
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.
Anita Orlowska; Adam Galezia; Andrzej Swiercz; Lukasz Jankowski. Mitigation of vibrations in sandwich-type structures by a controllable constrained layer. Journal of Vibration and Control 2020, 27, 1595 -1605.
AMA StyleAnita Orlowska, Adam Galezia, Andrzej Swiercz, Lukasz Jankowski. Mitigation of vibrations in sandwich-type structures by a controllable constrained layer. Journal of Vibration and Control. 2020; 27 (13-14):1595-1605.
Chicago/Turabian StyleAnita Orlowska; Adam Galezia; Andrzej Swiercz; Lukasz Jankowski. 2020. "Mitigation of vibrations in sandwich-type structures by a controllable constrained layer." Journal of Vibration and Control 27, no. 13-14: 1595-1605.
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.
Jilin Hou; Zhenkun Li; Łukasz Jankowski; Sijie Wang. Estimation of virtual masses for structural damage identification. Structural Control and Health Monitoring 2020, 27, 1 .
AMA StyleJilin Hou, Zhenkun Li, Łukasz Jankowski, Sijie Wang. Estimation of virtual masses for structural damage identification. Structural Control and Health Monitoring. 2020; 27 (8):1.
Chicago/Turabian StyleJilin Hou; Zhenkun Li; Łukasz Jankowski; Sijie Wang. 2020. "Estimation of virtual masses for structural damage identification." Structural Control and Health Monitoring 27, no. 8: 1.
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.
Jilin Hou; Haiyan Wang; Dengzheng Xu; Łukasz Jankowski; Pengfei Wang. Damage Identification Based on Adding Mass for Liquid–Solid Coupling Structures. Applied Sciences 2020, 10, 2312 .
AMA StyleJilin Hou, Haiyan Wang, Dengzheng Xu, Łukasz Jankowski, Pengfei Wang. Damage Identification Based on Adding Mass for Liquid–Solid Coupling Structures. Applied Sciences. 2020; 10 (7):2312.
Chicago/Turabian StyleJilin Hou; Haiyan Wang; Dengzheng Xu; Łukasz Jankowski; Pengfei Wang. 2020. "Damage Identification Based on Adding Mass for Liquid–Solid Coupling Structures." Applied Sciences 10, no. 7: 2312.
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.
Qingxia Zhang; Jilin Hou; Łukasz Jankowski. Bridge Damage Identification Using Vehicle Bump Based on Additional Virtual Masses. Sensors 2020, 20, 394 .
AMA StyleQingxia Zhang, Jilin Hou, Łukasz Jankowski. Bridge Damage Identification Using Vehicle Bump Based on Additional Virtual Masses. Sensors. 2020; 20 (2):394.
Chicago/Turabian StyleQingxia Zhang; Jilin Hou; Łukasz Jankowski. 2020. "Bridge Damage Identification Using Vehicle Bump Based on Additional Virtual Masses." Sensors 20, no. 2: 394.
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.
Machi Zawidzki; Łukasz Jankowski. Multiobjective optimization of modular structures: Weight versus geometric versatility in a Truss‐Z system. Computer-Aided Civil and Infrastructure Engineering 2019, 34, 1026 -1040.
AMA StyleMachi Zawidzki, Łukasz Jankowski. Multiobjective optimization of modular structures: Weight versus geometric versatility in a Truss‐Z system. Computer-Aided Civil and Infrastructure Engineering. 2019; 34 (11):1026-1040.
Chicago/Turabian StyleMachi Zawidzki; Łukasz Jankowski. 2019. "Multiobjective optimization of modular structures: Weight versus geometric versatility in a Truss‐Z system." Computer-Aided Civil and Infrastructure Engineering 34, no. 11: 1026-1040.
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.
Rami Faraj; Łukasz Jankowski; Cezary Graczykowski; Jan Holnicki-Szulc. 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 2019, 356, 7855 -7872.
AMA StyleRami Faraj, Łukasz Jankowski, Cezary Graczykowski, Jan Holnicki-Szulc. 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. 2019; 356 (14):7855-7872.
Chicago/Turabian StyleRami Faraj; Łukasz Jankowski; Cezary Graczykowski; Jan Holnicki-Szulc. 2019. "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 356, no. 14: 7855-7872.
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.
Jilin Hou; Sijie Wang; Qingxia Zhang; Łukasz Jankowski. An Improved Objective Function for Modal-Based Damage Identification Using Substructural Virtual Distortion Method. Applied Sciences 2019, 9, 971 .
AMA StyleJilin Hou, Sijie Wang, Qingxia Zhang, Łukasz Jankowski. An Improved Objective Function for Modal-Based Damage Identification Using Substructural Virtual Distortion Method. Applied Sciences. 2019; 9 (5):971.
Chicago/Turabian StyleJilin Hou; Sijie Wang; Qingxia Zhang; Łukasz Jankowski. 2019. "An Improved Objective Function for Modal-Based Damage Identification Using Substructural Virtual Distortion Method." Applied Sciences 9, no. 5: 971.
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.
Jilin Hou; Zhenkun Li; Qingxia Zhang; Runfang Zhou; Łukasz Jankowski. Optimal Placement of Virtual Masses for Structural Damage Identification. Sensors 2019, 19, 340 .
AMA StyleJilin Hou, Zhenkun Li, Qingxia Zhang, Runfang Zhou, Łukasz Jankowski. Optimal Placement of Virtual Masses for Structural Damage Identification. Sensors. 2019; 19 (2):340.
Chicago/Turabian StyleJilin Hou; Zhenkun Li; Qingxia Zhang; Runfang Zhou; Łukasz Jankowski. 2019. "Optimal Placement of Virtual Masses for Structural Damage Identification." Sensors 19, no. 2: 340.
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.
Jilin Hou; Pengfei Wang; Tianyu Jing; Łukasz Jankowski. Experimental Study for Damage Identification of Storage Tanks by Adding Virtual Masses. Sensors 2019, 19, 220 .
AMA StyleJilin Hou, Pengfei Wang, Tianyu Jing, Łukasz Jankowski. Experimental Study for Damage Identification of Storage Tanks by Adding Virtual Masses. Sensors. 2019; 19 (2):220.
Chicago/Turabian StyleJilin Hou; Pengfei Wang; Tianyu Jing; Łukasz Jankowski. 2019. "Experimental Study for Damage Identification of Storage Tanks by Adding Virtual Masses." Sensors 19, no. 2: 220.
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.
Jilin Hou; Yonghui An; Sijie Wang; Zhenzhen Wang; Łukasz Jankowski; Jinping Ou. Structural Damage Localization and Quantification Based on Additional Virtual Masses and Bayesian Theory. Journal of Engineering Mechanics 2018, 144, 04018097 .
AMA StyleJilin Hou, Yonghui An, Sijie Wang, Zhenzhen Wang, Łukasz Jankowski, Jinping Ou. Structural Damage Localization and Quantification Based on Additional Virtual Masses and Bayesian Theory. Journal of Engineering Mechanics. 2018; 144 (10):04018097.
Chicago/Turabian StyleJilin Hou; Yonghui An; Sijie Wang; Zhenzhen Wang; Łukasz Jankowski; Jinping Ou. 2018. "Structural Damage Localization and Quantification Based on Additional Virtual Masses and Bayesian Theory." Journal of Engineering Mechanics 144, no. 10: 04018097.
Blazej Poplawski; Grzegorz Mikulowski; Arkadiusz Mróz; Łukasz Jankowski. 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 2018, 100, 926 -939.
AMA StyleBlazej Poplawski, Grzegorz Mikulowski, Arkadiusz Mróz, Łukasz Jankowski. 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. 2018; 100 ():926-939.
Chicago/Turabian StyleBlazej Poplawski; Grzegorz Mikulowski; Arkadiusz Mróz; Łukasz Jankowski. 2018. "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 100, no. : 926-939.
This contribution deals with the inverse problem of indirect identification of moving loads. The identification is performed based on the recorded response of the loaded structure and its numerical model. A specific feature of such problems is a very large number of the degrees of freedom (DOFs) that can be excited and a limited number of available sensors. As a result, unless the solution space is significantly limited, the identification problem is underdetermined: it has an infinite number of exact, observationally indistinguishable solutions. We propose an approach based on the assumption of sparsity of the excitation, which can be expressed in the form of a requirement of a bounded l1 norm of the solution. As long as the loads are sparse, the approach allows them to be freely moving, without the usual assumption of a constant velocity. We first test the approach in a numerical example with 10% rms measurement noise. A good qualitative agreement of the numerical results allows to proceed with experimental investigations, and the moving load identification is then carried out based on the response measured experimentally on a lab test stand.
Michał Gawlicki; Łukasz Jankowski. Identification of moving loads using the ?1 norm minimization. COMPUTER METHODS IN MECHANICS (CMM2017): Proceedings of the 22nd International Conference on Computer Methods in Mechanics 2018, 1 .
AMA StyleMichał Gawlicki, Łukasz Jankowski. Identification of moving loads using the ?1 norm minimization. COMPUTER METHODS IN MECHANICS (CMM2017): Proceedings of the 22nd International Conference on Computer Methods in Mechanics. 2018; ():1.
Chicago/Turabian StyleMichał Gawlicki; Łukasz Jankowski. 2018. "Identification of moving loads using the ?1 norm minimization." COMPUTER METHODS IN MECHANICS (CMM2017): Proceedings of the 22nd International Conference on Computer Methods in Mechanics , no. : 1.
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. In an EMS, the assembly, reconfiguration and deployment difficulty is moved towards the module, which is relatively complex and whose assembly is not intuitive. As a result, an EMS requires intensive computation for assembling its desired free-form geometrical configuration, while its advantage is the economization of construction and reconfiguration by extreme modularization and mass prefabrication. TZ is a skeletal modular system for creating free-form pedestrian ramps and ramp networks among any number of terminals in space. TZ structures are composed of four variations of a single basic module (Truss-Z module, TZM) subjected to affine transformations (mirror reflection and rotation). The previous research on TZ focused on global discrete optimization of the spatial configuration of modules. This contribution is the first attempt at structural optimization of the TZM for a single-branch TZ. The result is a multicriterial optimization, where the Pareto front provides the means to strike the optimal balance between geometric and structural assessment criteria.
Machi Zawidzki; Łukasz Jankowski. Multicriterial Optimization of Geometrical and Structural Properties of the Basic Module of a Single-Branch Truss-Z Structure. Advances in Structural and Multidisciplinary Optimization 2017, 163 -174.
AMA StyleMachi Zawidzki, Łukasz Jankowski. Multicriterial Optimization of Geometrical and Structural Properties of the Basic Module of a Single-Branch Truss-Z Structure. Advances in Structural and Multidisciplinary Optimization. 2017; ():163-174.
Chicago/Turabian StyleMachi Zawidzki; Łukasz Jankowski. 2017. "Multicriterial Optimization of Geometrical and Structural Properties of the Basic Module of a Single-Branch Truss-Z Structure." Advances in Structural and Multidisciplinary Optimization , no. : 163-174.