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Structural health monitoring (SHM) systems have been developed to evaluate structural responses to extreme events such as natural and man-made hazards. Additionally, the increasing volume of users and vehicle sizes can lead to the sudden damage and collapse of bridge structures. Hence, structural monitoring and dynamic characteristic analyses of bridge structures are critical and fundamental requirements for bridge safety. SHM can overcome the weaknesses of visual inspection practices, such as lack of resolution. However, because of computational limitations and the lack of data analysis methods, substantial quantities of SHM data have been poorly interpreted. In this paper, the SHM of bridges based on dynamic characteristics is used to assess the \"health state\" of bridge structures. A comprehensive SHM system using vibration-based techniques and modal identification for bridge structures are well defined. Some advanced concepts and applications regarding bridge safety evaluation methods, including damage detection and load-carrying capacity, are reviewed. For the first time, the pros and cons of each vibration technique are comprehensively evaluated, providing an advantage to the authority or structural owner when developing a bridge management database. This information can then be used for continuous structural monitoring to access and predict the bridge structure condition.

Toroidal tuned liquid column dampers (TLCDs) are recently designed devices that extend the application of TLCDs to multidirectional vibration control. Toroidal TLCDs are promising in suppressing the horizontal vibration response of structures. This study further explores the potential and optimization scheme of toroidal TLCDs for multidirectional pitching vibration mitigation. Firstly, equations of motion for a toroidal TLCD-structure system in pitching motion are presented. A non-iterative analytical closed-form solution for calculating the dynamic response of the system under harmonic loading is developed. Subsequently, optimized frequency tuning ratio and flow resistance coefficient can be obtained. The optimization results theoretically confirm the direction-independent control performance of toroidal TLCDs. A design example of toroidal TLCDs is presented in detail as a reference. Finally, a pendulum rotational structure for TLCDs testing in pitching motion is constructed. The multidirectionality, effectiveness and robustness of toroidal TLCDs in mitigating pitching vibration are verified by free vibration tests.

This article studies the vibrational behavior of composite conical-cylindrical shells (CCSs) with functionally graded coatings (FGCs) in thermal environments using the first-order shear deformation theory. Firstly, the equivalent material parameters, fundamental frequency, and resonant displacement responses of the CCSs with FGCs are derived using the mixture principle, complex modulus method, and transfer function approach. Then, detailed thermal vibration tests are performed on CCS structures with and without coatings to assess the reliability of the proposed model, revealing that the current model accurately forecasts the thermal vibration behavior of the CCSs with FGCs. Finally, the effect of key parameters on the vibrational properties of the CCSs with FGCs is investigated. The results demonstrate that increasing the functionally graded index, coating thickness, and Young’s modulus ratio can greatly enhance the vibration suppression capability of the structure.

In response to the problems of long-time consumption and poor reliability in the formulation of satellite vibration test conditions, a general method for the concave design of vibration test conditions has been solidified, and an automated implementation tool has been developed. Firstly, based on the experience of formulating satellite vibration test conditions, a general method for concave design under vibration test conditions was constructed. Then, based on the concave design method under vibration test conditions, a concave design tool for vibration test conditions was designed from the perspectives of operational convenience and visualization; Finally, the concave design tool under vibration test conditions was applied to the formulation of satellite vibration test conditions, further verifying the application effect.

Many transportation infrastructures all around the world are facing new challenges in terms of ageing and loss of performance. The infrastructural asset managers are required to perform scrupulous control of the health condition of the infrastructures over time and to execute the required maintenance works. In this context, digital twin models of the infrastructures should have a key role to simplify and speed up the procedures for proper maintenance. This paper discusses the advantages of developing digital twin models for the management of infrastructures, with a focus on bridges. In particular, the role of dynamic tests performed on bridges for the development of digital twin models is addressed, paying attention to test procedures and requirements. Issues such as the quality of instrumentation, the numerosity, and layout of sensors, and the acquisition and post-processing procedures are addressed through applications to two real bridge case studies. Both infrastructures are multi-span pre-stressed RC bridges that were dynamically tested after the restoration and seismic upgrading works. Results of ambient vibration tests and operational modal analyses are described, providing an idea of dynamic test requirements, as well as their use within the framework of the digital twin model creation.

In order to reduce the excessive vibration responses of a reinforced concrete frame structure induced by several vibrating screens working simultaneously, field vibration monitoring and some vibration reduction measures are carried out. The results of field vibration monitoring show that the maximum vertical vibration of the structure exceeds 106% of the limitation of building vibration. The results of the structural response analysis show that the excessive structural vibration is attributed to the resonance, as the frequency of the vibrating screens coincides with vertical natural frequency of the floors of the factory structure. Based on this fact, three vibration control measures, including damping, active vibration isolation of vibrating screens and structural vibration absorption, are proposed to mitigate the excessive vibration. In order to analyze the vibration control performance of the proposed schemes, the finite element dynamic model of the factory building structure is established, and the model is verified by the results of vibration and mode tests. Then, the damping system, vibration isolation system and vibration absorption system are set up in the models, and the vibration control performance of the three schemes are investigated. The results show that the measures, including vibration isolation and absorption, can reduce the vibration by more than 80%. Combined with the demand for a short construction period, the active vibration isolation of vibrating screens is finally selected. After the implementation of the scheme, the field monitoring data show that the structural vibration response is consistent with the finite element result and obviously weakened to meet the limitation. This study can provide a reference for the vibration control design for similar screening factory buildings.

In-service prestressed concrete box girder bridges have received increasing attention in recent years due to a large number of bridges reaching decades in service. Therefore, the ageing of infrastructure demands the development of robust condition assessment methodologies based on affordable technology such as vehicle-induced vibration tests (VITs) in contrast with more expensive existing technologies such as tests using hammers or shakers. Ambient vibration tests (AVTs) have been widely used worldwide, taking advantage of freely available ambient excitation sources. However, the literature has commonly reported insufficient input energy to excite the structure to obtain satisfactory modal identification results, especially in long-span concrete bridges. On the other hand, the use of forced vibration tests (FVTs) requires more economic resources. This paper presents the results of field measurements at optimally selected locations in VITs consisting of a 32-ton truck and a springboard with a height of 50 mm. AVTs using optimal sensor placement (OSP) provide similar results to VITs without considering OSP locations. Additionally, the VIT/AVT cost ratio is reduced to 2 since a shorter data collection time is achieved within a one-day (8 h) test framework, which minimizes temperature effects, thus leading to improvements in AVT identification results, especially in vertical modes.

A vibration test, which does not require a complex measuring technique, is a simple and nondestructive method for measuring elastic constants. The strength of wood can be estimated using a vibration test because of the positive relationship between the dynamic Young’s modulus and strength. The vibrational properties of wood are affected by inhomogeneities in the specimen (knots and holes), grain angle, dimensions of the specimen, temperature, humidity (moisture content) and end conditions. Frequency equations that consider additional mass and defects in a wood specimen were shown for various vibration modes. The effects of sections of differing quality within a wood specimen, such as knots and holes on the results of vibration tests can be discussed using the aforementioned frequency equations, the shapes of bending vibration waves generated by the tapping of wood specimens determined using a transfer function, resonance frequency shifts of a power spectrum due to defects, and the dependence of Young’s modulus on the resonance mode number. The mass and Young’s modulus of the lumber in a stack and beams of timber guardrails can be estimated without weighing.

Structures and their components experience substantially large vibration amplitudes at resonance, which can cause their failure. The scope of this study is the utilization of silicone-coated steel balls in concrete as damping aggregates to suppress the resonance vibration. The heavy steel cores oscillate with a frequency close to the resonance frequency of the structure. Due to the phase difference between the vibrations of the cores and the structure, the cores counteract the vibration of the structure. The core-coating inclusions are randomly distributed in concrete similar to standard aggregates. This mixture is referred to as metaconcrete. The main goal of this work is to validate the ability of the inclusions to suppress mechanical vibration through laboratory experiments. For this purpose, two small-scale metaconcrete beams were cast and tested. In a free vibration test, the metaconcrete beams exhibited a larger damping ratio compared to a similar beam cast from conventional concrete. The vibration amplitudes of the metaconcrete beams at resonance were measured with a frequency sweep test. In comparison with the conventional concrete beam, both metaconcrete beams demonstrated smaller vibration amplitudes. Both experiments verified an improvement in the dynamic response of the metaconcrete beams at resonance vibration.

The landing gear system is one of the most critical systems of the aircraft. The need to design a landing gear with high performance, longer life and with a significant reduction in terms of weight, production and maintenance costs represents a real challenge for a sustainable future that Europe is heralding. This paper presents the results of the experimental campaign of vibration tests performed on the main and side landing gear system, in both extended and retracted configurations, to be installed on the AIRBUS Group/Helicopter RACER compound helicopter demonstrator and it is part of the Project ANGELA within the European Research Program Clean Sky 2 Fast-Rotorcraft. Furthermore, in this paper will be described the tailoring of the standard. The hybrid nature of the RACER, not envisaged in any of the categories of the standard, required a tailoring phase to test the landing gear systems in a conservative condition. Thus, it will be shown how this phase led to defining a test sequence, a test setup and the vibration loads. The test campaign, conducted with RTCA DO 160-G tailoring, is part of a wider experimental activity aimed at the development, production and qualification of processes and materials that will allow the landing gear system to achieve the “Permit to Flight”.