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, Hernán Garrido, Daniel Ambrosini
Published: 10 December 2021
Engineering Structures, Volume 252; https://doi.org/10.1016/j.engstruct.2021.113667

The publisher has not yet granted permission to display this abstract.
Published: 8 December 2021
by MDPI
Sensors, Volume 21; https://doi.org/10.3390/s21248211

Abstract:
Liquid dampers, such as tuned liquid dampers (TLDs), are employed to improve serviceability by reducing wind-affected building vibrations. In order to maximize the vibration suppression efficiency of the liquid damper, the tuning frequency of the liquid damper should match the natural frequency of the building. Experimental evaluation of the tuning frequency of a liquid damper performed in a factory prior to installation in a building is a critical task to ensure correct performance, and for this, multipoint measurement of the TLD is required. In this study, a novel liquid level measurement system combining Laser Doppler Vibrometer (LDV) and a stepwise rotating galvanometer scanner was developed to observe liquid sloshing in TLD. The proposed system can measure the liquid level at multiple points simultaneously with a single laser point. In the experimental phase, the liquid damper’s natural frequency and mode shape are experimentally evaluated utilizing the developed system. The performance of the proposed system was verified by comparison with the video sensing system.
Xuan-Thuan Nguyen, Nanako Miura, , Thanh-Lam Bui
Mechanics Based Design of Structures and Machines pp 1-18; https://doi.org/10.1080/15397734.2021.2002163

Abstract:
This article proposes a method for optimizing multiple tuned mass damper (TMD) devices for reducing bridge vibration as a vehicle passes over it. The method can design multiple TMD parameters simultaneously for different modes contributing to multiple resonance peaks. Moreover, the study analyzed the vibration of bridges with uncertain parameters. This study’s motivation is based on the optimal design of TMDs for bridge structures under external forces, such as the loads of moving cars and high-speed trains. In this case, the resonant response phenomenon can only happen at specific frequencies. The proposed optimization was developed based on the H2 norm method to design the TMD parameters. The target of the present method is to minimize the response peaks around the resonance frequencies. Moreover, the contribution of the excited modes to each other at their resonance frequencies is considered. The TMD parameters were found to demonstrate good performance for reducing the vibration of bridges due to moving vehicles.
Published: 9 November 2021
Journal of Sensors, Volume 2021, pp 1-12; https://doi.org/10.1155/2021/8325398

Abstract:
The delayed fracture of high-strength bolts occurs frequently in the bolt connections of long-span steel bridges. This phenomenon can threaten the safety of structures and even lead to serious accidents in certain cases. However, the manual inspection commonly used in engineering to detect the fractured bolts is time-consuming and inconvenient. Therefore, a computer vision-based inspection approach is proposed in this paper to rapidly and automatically detect the fractured bolts. The proposed approach is realized by a convolutional neural network- (CNN-) based deep learning algorithm, the third version of You Only Look Once (YOLOv3). A challenge for the detector training using YOLOv3 is that only limited amounts of images of the fractured bolts are available in practice. To address this challenge, five data augmentation methods are introduced to produce more labeled images, including brightness transformation, Gaussian blur, flipping, perspective transformation, and scaling. Six YOLOv3 neural networks are trained using six different augmented training sets, and then, the performance of each detector is tested on the same testing set to compare the effectiveness of different augmentation methods. The highest average precision (AP) of the trained detectors is 89.14% when the intersection over union (IOU) threshold is set to 0.5. The practicality and robustness of the proposed method are further demonstrated on images that were never used in the training and testing of the detector. The results demonstrate that the proposed method can quickly and automatically detect the delayed fracture of high-strength bolts.
Zhou Huang, Yang Liu, , Ming Zhang, Lei Wang
Arabian Journal for Science and Engineering pp 1-16; https://doi.org/10.1007/s13369-021-06194-2

The publisher has not yet granted permission to display this abstract.
Delong Guan, Yonghui An, Xin Xiao, Xinxin Zhao, Jinping Ou
Journal of Performance of Constructed Facilities, Volume 35; https://doi.org/10.1061/(asce)cf.1943-5509.0001601

Abstract:
The riveted steel truss bridge, which is commonly subjected to railway traffic loads, suffers from a potential severe threat of fatigue failure. Therefore, it is imperative to evaluate its fatigue performance. An integrated fatigue life evaluation method is proposed, and three main improvements are included: (1) fatigue evaluation is conducted with a consideration of both the stress ratio effect and load sequence effect; (2) a modified rainflow method maintaining the load sequence is introduced to consider the load sequence; and (3) a whole-range modeling methodology is applied to extend the partially known S-N curve to an S-N curve applicable to the whole range of fatigue regions, which is essential when considering the load sequence effect. To illustrate the effectiveness of the proposed method, the long-term monitoring stress data of an old riveted steel truss bridge are used in the analysis. The fatigue conditions of the monitored members are investigated, the effects of both the stress ratio and load sequence are analyzed, and a key point of fatigue life evaluation is proposed. It is shown that the longitudinal beam of the deck is the critical fatigue member among all monitored members, the stress ratio effect differs with member type and measured point, fatigue life evaluation results are obviously influenced by the effects of both the stress ratio and load sequence, and the load sequence effect is greater than that of the stress ratio effect on the fatigue life evaluation. The proposed integrated method lays a solid foundation for fatigue life evaluation of members in riveted steel truss bridges, which can provide meaningful guidance for maintenance. At the same time, sufficient attention should be devoted to the optimal sensor layout for fatigue life evaluation, which is vital for assessing a structure’s life cycle performance.
, Jie Tan, Haitao Liu, Gang Yang, Chunyi Cui
Mathematical Problems in Engineering, Volume 2021, pp 1-13; https://doi.org/10.1155/2021/6647303

Abstract:
In order to mitigate the seismic response of a cable-stayed bridge, a new type damping device named asymmetric pounding tuned mass damper (APTMD) is developed in this paper on the basis of the traditional symmetric pounding tuned mass damper. The novel APTMD has three parameters to be determined: the left-side gap, the right-side gap, and the frequency ratio. A numerical model of the APTMD damping system is established with consideration of both the computational efficiency and accuracy to enable the parametric optimization of the damper. The numerical model is based on a simplified model of the cable-stayed bridge and a nonlinear pounding force model. The genetic algorithm is utilized for the optimization of the damper. Afterwards, the cable-stayed bridge is subjected to 20 recorded ground motions to evaluate the vibration control effectiveness of the APTMD. Four systems are considered: (1) without dampers; (2) with a TMD; (3) with a PTMD; and (4) with an APTMD. Time history analysis reveals the following: (1) those dampers can all effectively suppress the vibration of the bridge and (2) the vibration control effectiveness of the APTMD is slightly better than the TMD and the PTMD.
Published: 28 February 2021
by MDPI
Actuators, Volume 10; https://doi.org/10.3390/act10030044

Abstract:
High-rise structures are normally tall and slender with a large height-width ratio. Under the strong seismic action, such a structure may experience violent vibrations and large deformation. In this paper, a spring pendulum pounding tuned mass damper (SPPTMD) system is developed to reduce the seismic response of high-rise structures. This SPPTMD system consists of a barrel limiter with the built-in viscoelastic material and a spring pendulum (SP). This novel type of tuned mass damper (TMD) relies on the internal resonance feature of the spring pendulum and the collision between the added mass and barrel limiter to consume the energy of the main structure. Based on the Hertz-damper model, the motion equation of the structure-SPPTMD system is derived. Furthermore, a power transmission tower is selected to evaluate the vibration reduction performance of the SPPTMD system. Numerical results revealed that the SPPTMD system can effectively reduce structural vibrations; the reduction ratio is greater than that of the spring pendulum. Finally, the influence of the key parameters on the vibration control performance is conducted for future applications.
Published: 4 February 2021
by MDPI
Applied Sciences, Volume 11; https://doi.org/10.3390/app11041389

Abstract:
The research paper presents a novel approach toward constructing motion equations for structures with attached MTMDs (multiple tuned mass dampers). A primary system with MDOF (multiple dynamic degrees of freedom) was reduced to an equivalent system with a SDOF (single degree of freedom) through the modal approach, and equations from additional MTMDs were added to a thus-created system. Optimization based on ℌ2 and ℌ∞ for the transfer function associated with the generalized displacement of an SDOF system was applied. The research work utilized GA (genetic algorithms) and SA (simulated annealing method) optimization algorithms to determine the stiffness and damping parameters for individual TMDs. The effect of damping and stiffness (MTMD tuning) distribution depending on the number of TMDs was also analyzed. The paper also reviews the impact of primary system mass change on the efficiency of optimized MTMDs, as well as confirms the results of other authors involving greater MTMD effectiveness relative to a single TMD.
Yin Chen, Shao-Wen Xie, Chao Tong, Hai-Hu Tan, Li-Jian Xu, , Jian-Xiong Xu
Transactions of Nonferrous Metals Society of China, Volume 30, pp 3333-3346; https://doi.org/10.1016/s1003-6326(20)65465-6

The publisher has not yet granted permission to display this abstract.
Jingkai Wang, , Chunguang Liu,
Published: 15 December 2020
Structural Health Monitoring, Volume 20, pp 2917-2935; https://doi.org/10.1177/1475921720977041

Abstract:
Acoustic emission technique, as a passive structural health monitoring technique, has been widely applied to detecting and locating the structural damage. The time difference of arrival and the wave velocity are the key factors in most of the acoustic emission localization methods, and the accuracy of these two factors will affect the accuracy of damage localization. To improve the accuracy of damage localization, this article proposes a new damage localization method based on the synchrosqueezed wavelet transform picker and the time-order method. The synchrosqueezed wavelet transform picker, which picks the time–frequency similar point based on time–frequency similarity theory in the low-noise interval of time–frequency matrix, can improve the accuracy and robustness of calculating time difference of arrival. Meanwhile, the time-order method not only measures the wave velocity in real time but also reduces the computing time by appropriately arranging the distribution of acoustic emission sensors. These advantages improve the accuracy and robustness of acoustic emission localization, which was verified by experiments. Furthermore, the new localization method was employed to study the energy distribution in the embedded section of steel bar during the pull-out test of steel bar and concrete, and the results show the types of resistance between steel bar and concrete.
Zhisong Wang, Hong-Nan Li, Gangbing Song
International Journal of Structural Stability and Dynamics, Volume 21; https://doi.org/10.1142/s0219455421300019

The publisher has not yet granted permission to display this abstract.
Published: 15 November 2020
by MDPI
Sensors, Volume 20; https://doi.org/10.3390/s20226523

Abstract:
The location of large telescopes, generally far from the data processing centers, represents a logistical problem for the supervision of the capture of images. In this work, we carried out a preliminary study of the vibration signature of the T80 telescope at the Javalambre Astrophysical Observatory (JAO). The study analyzed the process of calculating the displacement that occurs because of the vibration in each of the frequencies in the range of interest. We analyzed the problems associated with very low frequencies by means of simulation, finding the most critical vibrations below 20 Hz, since they are the ones that generate greater displacements. The work also relates previous studies based on simulation with the real measurements of the vibration of the telescope taken remotely when it is subjected to different positioning movements (right ascension and/or declination) or when it performs movement actions such as those related to filter trays or mirror cover. The obtained results allow us to design a remote alarm system to detect invalid images (taken with excess vibration).
Lingzhu Zhou, Yu Zheng, Hongwei Ma,
Journal of Intelligent Material Systems and Structures, Volume 32, pp 473-485; https://doi.org/10.1177/1045389x20953619

Abstract:
Piezoelectric enabled stress wave methods for concrete structural health monitoring have been widely researched. However, the attenuation characteristics of stress wave in cracked concrete structures have barely been studied. As a result, it is hard to quantify the damage levels of the concrete structure. In this paper, the attenuation characteristics of stress wave in cracked concrete beam are studied using stress wave with the time-reversal technique. The attenuation model of stress waves related to the focused signal amplitude and the total crack width of concrete beam is proposed. In this study, a series of 18 concrete beams were tested using a four-point loading. During the test procedure, the signals of stress wave from the piezoelectric smart aggregate transducers in all the test specimens were collected to facilitate the proposed model. The test data of 12 beams are used to determine the attenuation coefficient of stress wave per unit crack width, and the test data of the other six beams are used to validate the accuracy of the proposed attenuation model. The results indicate that the prediction results based on the stress wave attenuation model are in good agreement with the test results of cracked concrete beams.
Published: 21 September 2020
by MDPI
Sensors, Volume 20; https://doi.org/10.3390/s20185398

Abstract:
Precast concrete segmental bridges (PCSBs) have been widely used in bridge engineering due to their numerous competitive advantages. The structural behavior and health status of PCSBs largely depend on the performance of the joint between the assembled segments. However, due to construction errors and dynamic loading conditions, some cracks and leakages have been found at the epoxy joints of PCSBs during the construction or operation stage. These defects will affect the joint quality, negatively impacting the safety and durability of the bridge. A structural health monitoring (SHM) method using active sensing with a piezoceramic-based smart aggregate (SA) to detect the crack and leakage in the epoxy joint of PCSBs was proposed and the feasibility was studied by experiment in the present work. Two concrete prisms were prefabricated with installed SAs and assembled with epoxy joint. An initial defect was simulated by leaving a 3-cm crack at the center of the joint without epoxy. With a total of 13 test cases and the different lengths of cracks without water and filled with water were simulated and tested. Time-domain analysis, frequency-domain analysis and wavelet-packet-based energy index (WPEI) analysis were conducted to evaluate the health condition of the structure. By comparing the collected voltage signals, Power Spectrum Density (PSD) energy and WPEIs under different healthy states, it is shown that the test results are closely related to the length of the crack and the leakage in the epoxy joint. It is demonstrated that the devised approach has certain application value in detecting the crack and leakage in the joint of PCSBs.
Published: 7 August 2020
by MDPI
Actuators, Volume 9; https://doi.org/10.3390/act9030066

Abstract:
An active mass damper (AMD) was developed that uses a linear motor and coil spring to reduce the vertical vibration of a long-period cable-stayed bridge subjected to wind and earthquake loads. A scaled-down bridge model and AMD were fabricated, and the control effect of the AMD was investigated experimentally and analytically. The AMD was controlled via a linear quadratic Gaussian algorithm, which combines a linear quadratic regulator and Kalman filter. The dynamic properties were investigated using a 1/10 scale indoor experimental model, and the results confirmed that the measured and analytical accelerations were consistent. A vibrator was used to simulate the wind-induced vibration, and the experimental and analytical results were consistent. The proposed AMD was confirmed to damp the free vibration and harmonic load and increase the damping ratio of the bridge model from 0.17% to 9.2%. Finally, the control performance of the proposed AMD was numerically investigated with the scaled-down bridge model subjected to the El Centro and Imperial Valley-02 earthquakes. These results were compared with those of a TMD, and they confirmed that the proposed AMD could reduce excessive vertical vibrations of long-period cable-stayed bridges subjected to wind and earthquakes.
Xin-Jun Gao, Peng-Hui Duan, Hui Qian
International Journal of Structural Stability and Dynamics, Volume 20; https://doi.org/10.1142/s0219455420400131

The publisher has not yet granted permission to display this abstract.
Runzhou You, ,
Smart Materials and Structures, Volume 29; https://doi.org/10.1088/1361-665x/ab939a

Abstract:
The significance of implementing structural health monitoring (SHM) system for civil engineering, especially infrastructure engineering, has been recognized. Distributed optical fiber sensor (DOFS) based on optical frequency domain reflectometer (OFDR) offers an attractive technique for in situ strain measurement due to its high resolution and high precision. However, a main challenge that naturally arises is how to guarantee sensors survival in harsh construction and service environments. In this paper, a new, but simple, packaging technique is proposed to solve this issue. The novel sensing tape is fabricated by embedding DOFS into two fiberglass tapes and its strain transfer mechanism is analyzed in detail to provide scientific criteria for the choice of the material parameters. Then, a calibration test is carried out to evaluate the performance of the sensing tape in distributed strain measurement. Finally, the tape sensor is applied to the surface strain monitoring of the reinforced concrete (RC) beam tested in three-point bending. Experimental results verify that the sensing tape works well on concrete materials and the strain measured has the capability to reveal and localize cracks. Both analytical and experimental results demonstrate that the proposed packaging technique is feasible and effective.
Published: 28 April 2020
by MDPI
Applied Sciences, Volume 10; https://doi.org/10.3390/app10093076

Abstract:
Compared with scaled-model testing, full-scale destructive testing is more reliable since the test has no size effect and can truly record the mechanical performance of the structure. However, due to the high cost, only very few full-scale destructive tests have been conducted on the flexural behavior of prestressed concrete (PC) box girders with girders removed from decommissioned bridges. Moreover, related destructive testing on the flexural behavior of a new precast box girder has been rarely reported. To investigate the flexural behavior and optimize the design, destructive testing of a 30-meter full-scale simply supported prestressed box girder was conducted at the construction site. It is illustrated that the failure mode of the tested girder was fracture of the prestressing tendon, and the corresponding maximum compressive strain in the top flange was only 1456 μ ε , which is far less than the ultimate compressive strain (3300 μ ε ). Therefore, the concrete in the top flange was not fully utilized. A nonlinear analysis procedure was performed using the finite strip method (FSM). The validity of the analysis was demonstrated by comparing the analytical results with those of the full-scale test in the field and a scaled model test in a laboratory. Using the developed numerical method, parametric analyses of the ratio of reinforcement were carried out. The prestressing tendon of the tested girder was increased from four strands to six strands in each duct. After the optimization of the prestressed reinforcement, the girder was ductile and the bearing capacity could be increased by 44.3%.
Yang Liu, Ming Zhang, , Zhou Huang, Lei Wang
Published: 25 April 2020
Journal of Sensors, Volume 2020, pp 1-13; https://doi.org/10.1155/2020/7526703

Abstract:
The carbon fiber reinforced polymer- (CFRP-) strengthened nanomaterial concrete beam (SNCB) has been increasingly attracting a widespread attention because of the advantages of using the excellent properties of nanomaterials to improve structural properties. An active sensing approach based on a piezoceramic transducer is developed to detect the interfacial debonding performance of CFRP-SNCB. A CFRP-SNCB specimen was fabricated and subjected to periodic loading test to initiate the debonding damage. Three piezoceramic smart aggregates (SAs) and three piezoceramic smart nanomaterial aggregates (SNAs) are embedded in the specimen and used as an actuator and sensor. Experiments show that the nanomaterial concrete becomes a good conduit for wave propagation due to the nucleation and filling effect of nanomaterial. The stress wave signal caused by the embedded SNAs is more sensitive to the debonding performance between CFRP and concrete than SA. The attenuation of stress wave caused by the increase of the severity of debonding damage can be clearly observed from the signals received from SAs and SNAs in the frequency domain analysis. The debonding cracking of the tension end region is earlier than the bond end region, which proves the starting point of structural debonding damage. Furthermore, the debonding state can be evaluated by wavelet packet analysis. The research results demonstrate that the proposed method has potentials to detect the interfacial debonding performance of CFRP-SNCB.
Jianxiong Xu, Guo Du, Chao Tong, Showen Xie, Haihu Tan, Lijian Xu,
Journal of Photochemistry and Photobiology A: Chemistry, Volume 396; https://doi.org/10.1016/j.jphotochem.2020.112518

The publisher has not yet granted permission to display this abstract.
Published: 9 March 2020
by MDPI
Materials, Volume 13; https://doi.org/10.3390/ma13051227

Abstract:
Superelastic shape memory alloy (SMA) exhibits the ability to undergo large deformations before reverting back to its undeformed shape following the removal of the load. This unique property underlies its great potential in the seismic design and retrofitting of structure members. In this paper, superelastic SMA wires were utilized to confine concrete cylinders to enhance their axial compressive behavior. The axial carrying and deformation capacities of SMA-confined concrete cylinders are assessed by uniaxial compression testing on a total of eight SMA-confined concrete columns and one unconfined column. The influence of the amount of SMA and the prestrain level of SMA wires, as well as the reinforcing mode, on the axial carrying and deformation capacity of confined concrete columns were considered. The analysis focuses on the axial carrying capacity and deformation performance of concrete columns reinforced with superelastic SMA under different loading conditions. Based on the experimental data and analysis results, it is found that superelastic SMA wires can increase the axial loading capacity and enhance deformation performance of concrete columns. Under the same loading condition, the ultimate bearing capacity of SMA-confined concrete columns increases as the increasing of the amount of SMA wire. The results of this study verify the effectiveness of superelastic SMA in enhancing the loading capacity and deformation behavior of concrete cylinders.
Published: 3 March 2020
by MDPI
Sensors, Volume 20; https://doi.org/10.3390/s20051376

Abstract:
Underground space engineering structures are generally subject to extensive damages and significant deformation. Given that composite rocks are prone to shear failure, which cannot be accurately monitored, the piezoelectric active sensing method and wavelet packet analysis method were employed to conduct a shear failure monitoring test on composite rocks in this study. For the experiment, specimens were prepared for the simulation of the composite rocks using cement. Two pairs of piezoelectric smart aggregates (SAs) were embedded in the composite specimens. When the specimens were tested using the direct shear apparatus, an active sensing-based monitoring test was conducted using the embedded SAs. Moreover, a wavelet packet analysis was conducted to compute the energy of the monitoring signal; thus allowing for the determination of the shear damage index of the composite specimens and the quantitative characterization of the shear failure process. The results indicated that upon the shear failure of the composite specimens, the amplitudes and peak values of the monitoring signals decreased significantly, and the shear failure and damage indices of the composite specimens increased abruptly and approached a value of 1. The feasibility and reliability of the piezoelectric active sensing method, with respect to the monitoring of the shear failure of composite rocks, was therefore experimentally demonstrated in this study.
Ning Zhao, Guoqing Huang, Ruili Liu, Peng Zhang, Chengwen Lu, Gangbing Song
Journal of Engineering Mechanics, Volume 146; https://doi.org/10.1061/(asce)em.1943-7889.0001738

Abstract:
Traffic signal structures are very susceptible to wind-induced vibration because of their slenderness and low damping. In the wind, the vertical vibration is usually dominant, which affects driving safety and structural fatigue life. To suppress the vibration, a new type of pounding tuned mass damper (PTMD) is proposed in this study. It is specially designed for a cantilevered traffic signal structure with two improvements based on the original PTMD. First, the proposed PTMD has a hidden design and is housed inside the cantilevered mast arm of traffic signal structures, which can avoid visual interference and potential safety risks to drivers and pedestrians. Second, the static equilibrium position of PTMD is relocated so that its mass block just touches the lower boundary of mast arm, which makes it effective at any level of amplitude. Concretely, the mass block pounds the lower boundary of the mast arm under small-amplitude vibrations, while it pounds both the lower and upper boundaries under large-amplitude vibrations. The model experiment on a traffic signal structure was designed to verify the performance of the proposed PTMD in free and forced vibrations. Further, the corresponding numerical simulations were also carried out, where a nonlinear viscoelastic model was established to model the impact force and the related model parameters were obtained by the experimental results. Both numerical and experimental results show that the proposed PTMD is very effective in reducing the vibration of traffic signal structures.
Published: 29 February 2020
by MDPI
Applied Sciences, Volume 10; https://doi.org/10.3390/app10051625

Abstract:
In this paper we develop a new approach to directly detect crash hotspot intersections (CHIs) using two customized spatial weights matrices, which are the inverse network distance-band spatial weights matrix of intersections (INDSWMI) and the k-nearest distance-band spatial weights matrix between crash and intersection (KDSWMCI). This new approach has three major steps. The first step is to build the INDSWMI by forming the road network, extracting the intersections from road junctions, and constructing the INDSWMI with road network constraints. The second step is to build the KDSWMCI by obtaining the adjacency crashes for each intersection. The third step is to perform intersection hotspot analysis (IHA) by using the Getis–Ord Gi* statistic with the INDSWMI and KDSWMCI to identify CHIs and test the Intersection Prediction Accuracy Index (IPAI). This approach is validated by comparison of the IPAI obtained using open street map (OSM) roads and intersection-related crashes (2008–2017) from Spencer city, Iowa, USA. The findings of the comparison show that higher prediction accuracy is achieved by using the proposed approach in identifying CHIs.
Published: 13 January 2020
by MDPI
Applied Sciences, Volume 10; https://doi.org/10.3390/app10020572

Abstract:
Many engineering systems, from subsea pipelines to space structures, from moving vehicles to stationary skyscrapers, are subject to unwanted vibration excitations. Often vibration control can be considered as a problem of energy dissipation and vibration damping. The aims of this issue are to accumulate, disseminate, and promote new knowledge about vibration control, especially for topics related to energy dissipation methods for vibration damping. Topics in this issue reflect the start-of-the-arts in the field of vibration control, such as inerter dampers and pounding tuned mass dampers (PTMDs). This special issue also reports other types of new energy dissipation devices, including a multi-unit particle damper, a nonlinear eddy current damper, and layered dampers. Also reported in this issue are structural elements with innovative designs to dissipate energy. In addition, this special issue also reports two research studies on the dynamic responses of a structural foundation and an earth-retaining structure. Though most papers in this special issue are related to passive methods, one paper reports a semi-active vibration control via magnetorheological dampers (MRDs), and another two papers report active vibration controls using piezoelectric transducers and inertial actuators, respectively.
Published: 9 January 2020
by MDPI
Nanomaterials, Volume 10; https://doi.org/10.3390/nano10010125

Abstract:
In this paper, an electrochemical method for the measurement of tryptophan (Trp) was developed based on a glassy carbon electrode modified with polyvinylpyrrolidonefunctionalized graphene (PVP-GR)/glassy carbon electrode (GCE). In 0.1 M phosphate buffer solution (PBS, pH = 2.2), compared with bare GCE, PVP/GCE, and GR/GCE, the oxidation peak current of Trp increased dramatically at PVP-GR/GCE. The oxidation mechanism of Trp on the PVP-GR/GCE was discussed and the experimental conditions were optimized. Under the best experimental conditions, the oxidation peak current of Trp was proportional to its concentration in the range of 0.06 µM–10.0 µM and 10.0–100.0 µM, and the limit of detection (LOD) was 0.01 µM (S/N = 3). The target modified electrode with excellent repeatability, stability and selectivity, was successfully applied to detectTrp in drugs and biological samples.
Published: 8 January 2020
by MDPI
Biomolecules, Volume 10; https://doi.org/10.3390/biom10010110

Abstract:
A novel tantalum pentoxide nanoparticle-electrochemically reduced graphene oxide nanocomposite-modified glassy carbon electrode (Ta2O5-ErGO/GCE) was developed for the detection of oxytetracycline in milk. The composition, structure and morphology of GO, Ta2O5, and Ta2O5-ErGO were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Oxytetracycline electrochemical behavior on the bare GCE, GO/GCE, ErGO/GCE, and Ta2O5-ErGO/GCE was studied by cyclic voltammetry. The voltammetric conditions (including scan rate, pH, deposition potential, and deposition time) were systematically optimized. With the spacious electrochemical active area, the Ta2O5-ErGO/GCE showed a great magnification of the oxidation signal of oxytetracycline, while that of the other electrodes (GCE, GO/GCE, ErGO/GCE) could not reach the same level. Under the optimum conditions, the currents were proportional to the oxytetracycline concentration in the range from 0.2 to 10 μM, and a low detection limit of 0.095 μM (S/N = 3) was detectable. Moreover, the proposed Ta2O5-ErGO/GCE performed practically with satisfactory results. The preparation of Ta2O5-ErGO/GCE in the current work provides a minor outlook of detecting trace oxytetracycline in milk.
, Liangfu Zheng, Peng Zhou, Huigang Xiao
Journal of Aerospace Engineering, Volume 33; https://doi.org/10.1061/(asce)as.1943-5525.0001104

Abstract:
Stay cables are prone to parametric vibrations, which might severely affect the serviceability and safety of cable-stayed bridges. This paper investigates the stability and dynamic characteristics of in-plane parametric vibrations for stay cables in cable-stayed bridges with superlong span under axial excitations. First, the nonlinear motion equation of a stay cable under axial harmonic excitation is derived on the basis of an established cable sag curve equation with the chord component of cable self-weight considered. Next, the equation is solved theoretically using a multiscale method, which reveals the conditions for the existence of the constant solution in parametric resonances. Subsequently, the sufficient conditions for the existence of the asymptotic steady solution are further obtained according to the Lyapunov’s first approximate stability criterion. Moreover, a numerical analysis is performed to assess the influences of the cable’s damping ratio, excitation frequency, and amplitude on the cable vibration using the longest cable, S36, in the Hutong Yangtze River Railway Bridge. The results show that the minimum external excitation amplitude exists for parametrical vibrations of stay cables, while the damping does not effectively suppress the amplitude of large-scale parametrical vibrations. Therefore, controlling the excitation amplitude may be an effective way to inhibit the parametrical vibrations of stay cables.
Published: 19 December 2019
by MDPI
Applied Sciences, Volume 10; https://doi.org/10.3390/app10010050

Abstract:
The application of reinforced concrete (RC) beam with near-surface mounted (NSM) pre-stressed carbon fiber reinforced polymer (CFRP) plates has been increasingly widespread in civil engineering. However, debonding failure occurs easily in the early loading stage because of the prestress change at the end of CFRP plate. Therefore, it is important to find reliable, convenient and economical technical means to closely monitor the secure bonding between CFRP and concrete. In this paper, an active sensing approach for generating and sensing stress wave by embedded smart aggregates (SAs) is proposed, which provides a guarantee for the secure connection between CFRP and concrete. Two specimens with different non-pre-stressed bond lengths were fabricated in the laboratory. Six SAs were installed at different positions of the structure to monitor the degree of debonding damage during the loading process. The experiments showed that the optimal length of non-pre-stressed CFRP bond section (300 mm) can significantly improve the load characteristics and enhance the service performance of the structure. The theoretical analysis of wavelet packet shows that increasing the length of non-pre-stressed CFRP bond section can slow down the occurrence and propagation of debonding cracks. The debonding crack in the tension end region is earlier than that in the bond end region. The research results reflect that the developed approach can monitor the damage process caused by debonding cracks and provide early warning for the initial damage and the debonding failure.
, Osamah Alsalih, Ammar Dakhil
Journal of King Saud University - Engineering Sciences, Volume 33, pp 30-36; https://doi.org/10.1016/j.jksues.2019.12.003

Abstract:
Differential settlement is a common problem in the bridge-roadway transition zone. Approach slabs are often constructed to mitigate the uneven settlement in this problematic zone. An appropriate simulation of the dynamic response of moving loads, approach slab and soil materials is necessary for realistic results. In the present study, the performance of the slab under traffic flow is investigated by a 3D dynamic analysis. For this purpose, the slab is modelled as a plate element while Mohr-Coulomb material model is adopted for base, subbase and subgrade soils. A number of parameters were considered to study the sensitivity of the proposed model to some soil, slab and moving load parameters that contribute to the behaviour of the approach slab. The main variables investigated in this study were the slab thickness, the restriction condition of the slab, the subgrade stiffness, weight of the passing vehicles and the analysis method adopted in such problems. Analysis results including predicted deformations and slab bending moments provide engineers with the necessary engineering knowledge to understand the response of approach slabs under different conditions.
Yang Liu, , , Chuang Hei,
Mathematical Problems in Engineering, Volume 2019, pp 1-11; https://doi.org/10.1155/2019/8725021

Abstract:
An active sensing approach using piezoceramic induced stress wave is proposed to provide monitoring and early warning for the development of interface debonding damage of precast segmental concrete beams (PSCBs). Three concrete specimens with toothed interfaces were fabricated and bonded with high-strength epoxy resin adhesive to form PSCBs. Smart aggregates (SAs) embedded in concrete specimens are used as actuators and sensors. The PSCBs are subjected to periodic loading with hydraulic jack to test the different degrees of debonding damage. The experimental results of time-domain and frequency-domain analysis clearly show that the amplitude of the signal received by the piezoceramic sensor is reduced when debonding crack occurs. The energy analysis and damage index based on wavelet packet can be used to determine the existence and severity of interface debonding damage in PSCBs. The experimental research validates the feasibility of monitoring the interface debonding damage in PSCBs using SA transducers based on active sensing technique.
Wen-Yu He, Jian He, Wei-Xin Ren
International Journal of Structural Stability and Dynamics, Volume 19; https://doi.org/10.1142/s0219455419501244

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Published: 2 August 2019
by MDPI
Applied Sciences, Volume 9; https://doi.org/10.3390/app9153144

Abstract:
The Active Rotary Inertia Driver (ARID) system is a novel vibration control system that can effectively mitigate the swing vibration of suspended structures. Parametric analysis is carried out using Simulink based on the mathematical model and the effectiveness is further validated by a series of experiments. Firstly, the active controller is designed based on the system mathematical model and the LQR (linear quadratic regulator) algorithm. Next, the parametric analysis is carried out using Simulink to study the key parameters such as the coefficient of the control algorithm, the rotary inertia ratio. Lastly, the ARID system control effectiveness and the parametric analysis results are further validated by the shaking table experiments. The effectiveness and robustness of the ARID system are well verified. The dynamic characteristics of this system are further studied, and the conclusions of this paper provide a theoretical basis for further development of such unique control system.
Published: 28 April 2019
by MDPI
Sensors, Volume 19; https://doi.org/10.3390/s19091990

Abstract:
The negative pressure wave (NPW) signals generated by a pipeline leakage often have a long signal duration. When these signals are utilized to compute the leakage position, the long signal duration will result in a large area being considered as leakage area. The localization resolution is low. A novel high-resolution localization algorithm is developed for pipeline leakage detection using piezoceramic transducers in this paper. The proposed algorithm utilizes multiple temporal convolutions to decrease the localization functional values at the points close to the leakage, in order to reduce the range of the leakage area revealed by the proposed algorithm. As a result, the localization resolution is improved. A measured experiment was conducted to study the proposed algorithm. In the experiment, the proposed algorithm was used to monitor a 55.8 m pressurized pipeline with two controllable valves and two Lead Zirconate Titanate (PZT) sensors. With the aid of the piezoceramic sensor, the experimental results show that the proposed algorithm results in a resolution which is better than that of the traditional method.
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