Considering the random uncertainty of landing gear parameters in design and manufacturing, this study conducts a quantitative study on the random response of carrier-based aircraft landing impact and the buffering performance of landing gear. This study established a dynamic model of the landing vibration of a carrier-based aircraft’s main landing gear. Based on the statistical characteristics of some filling parameters of the landing gear buffer (such as the initial volume of the air chamber, pressure oil area, oil shrinkage coefficient, etc.), the representative point set is divided by the direct probability integration method (DPIM), and the deterministic structural equation and probability density integration equation on the representative point set are solved. At the same time, the accuracy of DPIM application in the landing gear stochastic model is demonstrated by using the Monte Carlo Simulation (MCS) method. By outputting the buffer stroke of the landing gear, the vertical tire force, and the axial force of the strut, the mean value, standard deviation, probability density function, and related features of these responses are obtained. It is found that although the distribution of these responses are concentrated near the mean value, there is still a possibility of significant responses leading to system failure. Therefore, a functional function is defined using the buffer stroke, vertical tire force, and the axial force of the strut, and a reliability evaluation study is conducted on the landing gear structure under different threshold values.

With the continuous development of aerospace industry, the load transfer structure of spacecraft is getting more and more complicated. In practical engineering, how to distribute the loads in a reasonable way is of great significance for the lightweight design of spacecraft and the guarantee of structural load carrying capacity, and it is also necessary to take into account the non-ideal boundary conditions of the overall structure to the local structure in the process of dynamic load transfer structure design. Based on this, this paper proposes a dynamic topology optimization design method for dynamic load transfer structure based on structural boundary condition equivalence, which can fully consider the influence of the overall structure on the local structure while designing the load transfer structure. The method firstly simplifies the connection boundary between the local structure and the overall structure into a spring unit and a centralized mass unit, optimizes the unit parameters through genetic algorithm to achieve the equivalence of boundary conditions, and finally establishes a topology optimization model of the load transfer structure based on the unit density variable in conjunction with the design objective of the dynamic compliance of the structure. Numerical examples verify the effectiveness of the new method and obtain the optimization design results with the variation of volume fraction, external load frequency and load constraint interval.

Limited by common situations of closely spaced modes and large structural dimension, damage identification based on modal parameter is difficult to perform in civil structures. A damage identification method based on multi-level modal group response reconstruction in the presence of close spaced modes is proposed. Several modes with small intervals are grouped together, and response of the entire modal group is extracted as damage sensitive characteristic. Based on the collected modal response, a multi-level damage identification strategy is adopted. In the super element level damage location, the original structure is first converted into a super element model with fewer DOFs through model reduction, and then the minimization problem is solved by defining the modal group response strain energy as a damage index to achieve the location of damaged super elements; In element level damage identification, the minimization problem is expressed as the discrepancy between reconstructed and actual modal group response to achieve elemental damage localization and quantification. A numerical simulation study and the experimental verification were conducted to demonstrate the operational process and feasibility of this method. Compared with traditional methods, the results show that the proposed method improves the accuracy and efficiency of damage identification through multi-level identification strategies and model reduction, and on the other hand, improves the shortcomings of modal-analysis-based methods that cannot accurately identify damage when faced with close spaced modes. Regardless of the presence or absence of close spaced modes. Damage identification can be performed based on multiple dynamic responses such as stress, strain, displacement, and acceleration of the structure.

A polynomial dimensional decomposition pseudo-excitation method (PDD-PEM) was established in the frequency domain to quantify the uncertainty of random vibration power spectrum density for vehicles with uncertain parameters under random road excitation. Transforming stationary random vibration analysis into harmonic load analysis through pseudo-excitation method, and transforming double random problems into single random problems; At the same time, the polynomial dimensional decomposition method is used to construct a random Surrogate model, and the explicit function of the power spectrum density response expressed by the polynomial basis is given, which effectively realizes the probabilistic evaluation of the structural response in the uncertain parameter space. In numerical examples, the method established in this paper was used to analyze the random vibration of vehicle systems with uncertain parameters under road roughness. Compared with the Monte Carlo method, the correctness and effectiveness of the established method were verified, and the influence of uncertain parameters on the structural response statistical characteristics was further discussed. These works laid a certain foundation for considering the optimization and control problems of vehicle system parameters with uncertainty.

With the development of performance-based earthquake engineering, the ‘risk-probabilistic’ oriented performance evaluation method has gradually gained the attention of researchers, an important part of which is seismic vulnerability analysis. At this stage, there are different kinds of vulnerability methods, and more researches focus on how to combine probability theory with earthquake engineering, but the reasonable comparison for the accuracy and applicability of different methods still requires further research. Based on the nonstationary random mainshock-aftershock sequences, this paper compares three methods commonly used in seismic vulnerability at this stage: linear fitting method, maximum likelihood estimation, and Monte Carlo method. Then, based on a reinforced concrete frame, a case study is carried out, and the applicability of these three methods as well as the influence of random aftershocks are discussed. Generally speaking, the results obtained by the three methods are similar, and the development trends are relatively consistent, which also proves the effectiveness of these three methods to a certain extent. The Monte Carlo method has a long calculation period, the maximum likelihood estimation is more suitable for the performance level of minor damage, and the linear fitting method is more accurate after excluding the scattered points in the collapse state. After considering non-stationary random aftershocks, the obtained structural vulnerability shows an overall left-shifting trend. If the influence of random aftershocks is not considered, the probabilistic risk caused by earthquake sequences will be greatly underestimated.

This study extends the filtered white noise model by proposing a time-frequency hybrid dimensionality reduction model for fully nonstationary seismic ground motion random fields, thereby overcoming the limitation of simulating only ground motion processes without capturing spatially distributed ground motion fields. Specifically, to address the difficulty in directly representing the spatial coherence of seismic random fields within the impulse response function of the filtered white noise model, a proper orthogonal decomposition (POD)-based dimensionality reduction simulation method is introduced. This approach enables a frequency-domain representation of spatially coherent white noise random vector processes. By applying the impulse response functions and modulation functions corresponding to different locations within the seismic random field to filter and modulate the respective white noise components, an efficient time–frequency hybrid dimensionality reduction representation of fully nonstationary seismic random fields is achieved. Numerical examples validate the accuracy and engineering applicability of the proposed model by comparing mean values, standard deviations, auto-/cross-correlation functions, as well as response spectra and coherence functions.

A novel data-driven method for simulating non-Gaussian stochastic processes is proposed in this paper. The sample conversion model and power spectrum conversion model are established by using artificial neural network models respectively. A neural network model is constructed based on sample data to transform Gaussian samples into non-Gaussian samples. The distribution function of the samples is modeled using the shifted generalized lognormal distribution, and the latent Gaussian power spectrum is directly obtained through the backpropagation neural network model. The Gaussian stochastic process samples are generated using the spectral representation method, and then transformed into non-Gaussian process samples using the sample conversion neural network model. This method is capable of generating non-Gaussian stochastic process samples based on limited sample data, addressing the challenge of determining latent Gaussian power spectrum, and solving the problems such as poor accuracy and limited application range of the central moments-based transformation models. Through numerical simulations and validation in turbulent wind fields, the accuracy and effectiveness of the proposed method are further demonstrated.

Traditional computer vision methods usually focus on the in-plane dynamic response of structures. Therefore, this paper proposes an image phase-based stereo matching temporal analysis method to achieve targetless robust monitoring of three-dimensional structural deformation. This method uses 2D-Gabor filters and Gaussian pyramid gradient algorithms for image preprocessing, applies a phase-based dense optical flow tracking algorithm and an improved semi-global block matching (SGBM) algorithm to realize full-field measurement of structural displacement in the region of interest, and further proposes an intuitive displacement-strain conversion method to measure three-dimensional strain of structures. Through virtual reality experiments based on physics-based graphics models (PBGM), it is verified that the error of this method compared with 3D-DIC and finite element analysis deformation is less than 2%; in vibration tests of outdoor bridge structures in the laboratory, the deformation error compared with traditional testing methods can be controlled within 8%, meeting engineering application accuracy. Without compromising accuracy, this method achieves targetless robust monitoring of three-dimensional structural deformation, and better solves the problems of large environmental impact and high cost in traditional structural deformation monitoring.

Real-time hybrid test has been applied to the performance test of high-speed train running on the bridge in recent year. In order to avoid the damage of specimens or loading systems caused by instability, it is necessary to study the stability of real-time hybrid test on traveling train-bridge system. The time-varying characteristic of the traveling train-bridge system poses challenges to the stability analysis of real-time hybrid test. Therefore, it is necessary to develop suitable stability prediction methods for the time-varying system. Firstly, the time-varying discrete state space equation of the real-time hybrid test on traveling vehicle-bridge system was established, which can accurately describe the changes of all state quantities of the test system over time. Then a stability criterion based on the spectral radius of the cumulative state transition matrix was proposed, and then by combining the stability criterion with the dichotomy method, a relative stability prediction method for the time-varying real-time hybrid test was developed. A serial of practical real-time hybrid tests on traveling vehicle-bridge system was conducted based on a shaking table. The results show that the critical stability obtained by the practical tests was in good agreement with the predicted results based on the developed stability prediction method. The developed method can accurately predict the stability of RTHT on vehicle-bridge coupled system.

Environmental microvibration affects the accuracy of precision instruments, making microvibration measurement and assessment crucial. Microvibration level measurement is based on the octave spectrum of the velocity signal. However, the frequency-domain FFT method used in traditional octave analysis suffers from shortcomings such as fixed resolution and low-frequency spectrum leakage. Therefore, a complex-analysis ZFFT correction algorithm based on ratio correction was proposed. Simulations show that this algorithm improves spectral resolution while maintaining the same number of FFT analysis points. While maintaining the same number of sampling points, the computational effort is significantly reduced, and the spectrum amplitude error is as low as one thousandth. Frequency-band octave analysis is employed to suppress low-frequency spectrum leakage and increase the number of spectral lines. A microvibration monitoring and analysis system was developed, comprising a low-frequency microvibration sensor, the MI-7208 intelligent measurement device, and microvibration level measurement and assessment software. Field measurements verified the system's ability to detect VC-F-level microvibration signals and its long-term measurement stability.

The fractional nonlinear Zener model is used to describe the nonlinear and viscoelastic constitutive relation of the vibration isolation system. The variation law of system amplitude-frequency response and backbone under the combined action of constant excitation and harmonic excitation is discussed, and the influence of constant excitation on the dynamic behavior of vibration isolation system is discussed significantly. The fractional-order derivative term is made equivalent to a term in the form of trigonometric function, the steady-state response of the system is solved by harmonic balance method, and the results are compared with a variety of other methods. The influences of different parameters on the coexistence frequency band range of the amplitude-frequency response multi-state solution are summarized, and the dynamic behaviors of the system under the combined excitation are obtained by using numerically simulation. The results show that there are five solutions co-existence region in the amplitude-frequency response solution under the combined effect of constant excitation and harmonic excitation, and the system shows a phenomenon of coexistence of softening characteristic and hardening characteristic, and the backbone of the amplitude-frequency curve is tilted firstly to the left and then to the right. Additionally, it is found that the periodic motion and chaos coexist in the system under the combined excitation, and the transition laws of the polymorphic coexistence region and its adjacent regions are summarized explicitly. Affected by constant excitation, the diversity of periodic motion of the system under the combined excitation is significantly different from the dynamic behavior under the action of simple harmonic excitation alone, and the transition rules of periodic motion of the system under the action of combined excitation are summarized based on the Lyapunov exponent.

Quasi-zero-stiffness (QZS) isolators have excellent vibration isolation performance in the low-frequency range. However, in complex excitation environments, such as load mismatch condition, vibration isolation performance and corresponding stability deteriorate. To improve the vibration isolation performance of electromagnetic zero-stiffness isolators (E-QZS) and reduce the sensitivity to load, a load adaptive sliding mode control method of E-QZS is proposed. The theoretical model of an electromagnetic zero-stiffness isolator is established and a sliding mode control is designed. The range of gain coefficients for stable operation is determined using Lyapunov’s theorem. Additionally, we have devised a load-adaptive control law and conducted a corresponding stability analysis. Through simulation and experimental research, the results demonstrate that setting appropriate gains can enhance vibration isolation performance by 90%. Furthermore, the introduction of a load-adaptive sliding mode controller effectively reduces the impact of sudden load changes on isolation performance, thereby improving the robustness of the isolation system.

In this paper, a new concentrated mass-bent beam model of aircraft pylon is proposed, which is an effective mode reduction method for the analysis of vibration characteristics of continuous structures of pylon. Firstly, according to the periodic structure and the stress characteristics of pylon structure under actual working conditions, pylon structure is simplified into a concentrated mass-bent beam model which consists of 12 mass elements and 11 beam elements in series by using the concentrated mass method. The two simply supported boundary conditions reflect the true constraints of pylon-wing front and rear lifting points. The transfer equation and characteristic equation of the model are established based on the transfer matrix method. After using the parameter sensitivity method to correct and optimize the uncertain parameters of bending stiffness, the effectiveness of pylon concentrated mass-bent beam model is verified by comparing with the lower order natural frequencies of the finite element model. On this basis an engine is connected to the front and rear lifting points of pylon-engine through the installation section as the basic excitation, and engine-pylon concentrated mass-bent beam coupled model is established. Transfer matrix method is applied to study the natural frequency of the coupled model and the vibration response of pylon structure under the take-off, cruise and flight idle conditions of the engine. The vibration envelope lines of pylon structure mass elements under different conditions and different times and the vibration response of the representative mass element are obtained. In addition, the effectiveness of the new model is further verified by comparing with the finite element method. The research results provide theoretical support for the vibration reduction design of the pylon structure.

With the advantages of small size, light weight, flexible design and excellent frequency selectivity, surface acoustic wave devices are widely used in radar, communication, non-destructive testing, electronic countermeasures, TV signal processing and other fields. For exploring the application of surface acoustic wave (SAW) devices in mass sensing, the Love wave propagation in a piezoelectric layered structure is systematically investigated from perspectives of theoretical analysis and numerical examples. As for the theoretical model consisting of an additional mass layer, a piezoelectric sensing layer and a semi-infinite elastic half-space, the exact solution that simultaneously satisfy the dynamic governing equations and the continuous conditions between layers is established, and the phase velocity of Love waves is obtained.Then,the three-layer structure is degenerated into two-layer structure by stepwise degradation method, and the correctness of the theory is verified by comparing with the results of previous paper. After validation, the influence of structural and material parameters of the additional mass layer on Love wave phase velocity is conducted, including the thickness, shear modulus, density, and dielectric coefficient. Finally, an approximate method with only consideration of the inertial effect of the additional mass layer is developed, with its applicable condition demonstrated. It is revealed via numerical examples that the Love wave is very sensitive to the thickness of the additional mass layer, while the dielectric coefficient has minimal influence on the phase velocity. Additionally, the phase velocity decreases linearly when the density of the additional mass layer increases. The approximate method proposed in this paper exhibits good universality, which simplifies the wave solving, and can possess high computational accuracy when the additional mass layer is thin. The results and methods in this paper can provide guidance for the application of SAW devices in mass sensing.

When the finite element method is employed to calculate the mechanical behaviors of a corrugated sandwich panel structure, the numerical model occupies a large amount of computational resources, which usually causes the problem of long-time solution. In order to reduce the scale of the finite element model and to quickly perform the dynamic analysis of such type structures, in this paper the middle corrugated sandwich layer is simplified into a homogeneous orthotropic plate. Then, based on the third-order shear deformation theory, the equivalent stiffness matrix of the corresponding laminated plate element is formulated from adequate performance analyses of the corrugated sandwich plate. Afterwards, the natural frequencies of two corrugated sandwich plate structures in typical boundary status are obtained respectively through the test and numerical calculation. By comparing with the experimental results, the effectiveness of the equivalent finite element model is verified. It turns out that the obtained results are much better than those based on the first-order shear deformation model. Moreover, the method proposed in this work can be utilized efficiently for modal parameter computations of the corrugated sandwich plates with the high accuracy.

It is often difficult to suppress vibration of flexible rotors at high-order critical speeds through conventional low-speed balancing, especially in the case of the rotor with initial bending. In this paper, a low-speed dynamic balancing method for flexible rotors with initial bending is presented first. Combining the modal information of the rotor with the measurement data at speeds below the critical speeds, the low-speed dynamic balancing method is able to balancing the critical speeds without directly measuring the vibrations at the critical speeds and the initial bending of the rotor. Based on this, a mode-by-mode forward higher-order-extra-trial-weight-free method is proposed for balancing the higher modes simultaneously. In the proposed method, the lower-mode balancing weights on different balancing planes are used as trial weights and linked by the modal ratios of the measuring points. This avoids the potential severe vibration when pass through the critical speeds if any additional trial weights are used for balancing the higher-order modes. The proposed method is validated by numerical simulation and experimental tests respectively. The results show that the proposed method is better than the traditional influence coefficient method in balancing performance. In addition, it also avoids potentially high resonant vibration response, thus providing a safer approach for the high order dynamic balancing of flexible rotors.

Impacts between the flexible rotor and stator will excite the internal resonance of the forward and backward modes, resulting in asynchronous vibration, i.e, intermittent contact between the rotor and stator. To reveal the internal resonance mechanisms of the forward modes and backward modes, a mathematical model of the rotor system is established, Runge-Kutta numerical solution is used to solve the equation of motion, and the event detection function is used to detect the contact and non-contact motions. Through the coordinate system transformation, the Campbell diagrams of the rotor system under the stationary coordinate system and the rotating coordinate system are obtained, and the internal resonance speeds in the forward modes and backward modes are analyzed. Through the numerically calculated bifurcation diagram, the trajectory and frequency domain characteristics of the rotor when the asynchronous contact motion occurs are analyzed. The results show that the main resonance amplitude jumps at the critical speed, and there are two asynchronous contact response speed ranges. The rotor exhibits a closed continuous precession law in the stationary coordinate system and a periodic motion law in the rotating coordinate system, and there is a frequency doubling relationship in the rotation coordinate system, and the system has 2：1 and 3：1 internal resonance phenomena. The numerical simulation analysis verifies the correctness of the rotating speed predictions corresponding to the internal resonance, and the rotating speeds corresponding to the internal resonance can be predicted by this calculation method to avoid the internal resonance phenomenon caused by asynchronous contact.

The wedge-shaped oil film in sliding bearings induces uneven heating effects on the journal of a rapidly rotating rotor, resulting in circumferential temperature variations in the journal. The thermal bending caused by these temperature differences exacerbates rotor vibration, leading to a phenomenon known as ‘Morton effect’ or rotor thermal instability. This effect is particularly severe in cantilevered rotors. Initially, an elliptical bearing’s thermal fluid lubrication model is established, and its dynamic coefficients and oil film temperature field are calculated. Subsequently, based on Fourier heat conduction theory, using the obtained oil film temperature as a boundary condition, a finite element method is employed to solve the three-dimensional transient temperature field of the journal to determine the thermal deformation and thermal stress. The thermal stress is then integrated to obtain an equivalent moment for rotor dynamic analysis. Additionally, the sliding bearing oil film thickness is updated based on thermal deformation. Repeating these steps completes the fluid-solid-thermal multi-field coupling analysis of the rotor-bearing system, and the effectiveness of the simulation model is validated against experimental data. Finally, parameter analysis is conducted on the rotor-bearing system with the rotor’s cantilever length and suspended mass as variables. The results indicate that reducing the cantilever length or decreasing the suspended mass effectively reduces system vibration.

In order to effectively control the vibration transmitted by the elastic supports of the aero-engine rotor, an active magnetic dry friction damper (AMDFD) is employed to tune the support damping. On the basis of the traditional dynamics model of the dual rotor system, an AMDFD-dual rotor-bearing seat dynamics model that can characterize the transmitted vibration of the support is established. The effectiveness of AMDFD in suppressing the transmitted vibration of the rotor supports is simulated by using a speed interval switching controller and a model-free adaptive controller, and the intrinsic principle in realizing suppression is elucidated. Using the AMDFD-twin-rotor system test rig, the test of transmitted vibration control when rotor passes through the multi-order critical speeds was carried out. The results show that the AMDFD controlled by aforementioned two controllers can effectively reduce the transmitted vibration at each bearing position, and the reduction is more than 52%.

The vibration and radiation noise caused by the mechanical power equipment running on the ship have great harm, and seriously reduce the stealth performance and combat ability of the ship. The feedforward control algorithm which depends on the precise model will fail due to the adverse factors such as the long running of the power plant without stopping or the external impact. The traditional method of on-line system identification using auxiliary white noise not only reduces the control performance, but also increases the convergence time of the identification process. The method proposed in this paper uses the control signal to model the controlled system required by the FxLMS algorithm online in the noise frequency band, with faster convergence speed and identification accuracy. When the controlled system changes abruptly, that is, when the phase frequency characteristics of the controlled system change beyond ±90°, the algorithm can also track the changes of the system in real time and maintain the stability of the control. The active vibration control of the single-layer power unit vibration isolation platform was studied. The experimental results showed that the online identification of FxLMS control algorithm achieved 20.44 dB noise reduction at the motor operating frequency (50 Hz) when there was no secondary path model. The on-line identification algorithm can also maintain the control stability and quickly identify the changes in the phase frequency characteristics of the system after the mutation of secondary path.

Bearing fault diagnosis is an important research topic in aviation engine prediction and health management. Signal processing algorithms and deep learning models in this field rely on datasets. However, publicly available datasets generally cover narrow speed ranges, large speed intervals, single loads, and a lack of composite fault data, making it difficult to support the practical development of fault diagnosis methods. This article discloses a vibration dataset of aircraft main shaft bearings with a wide speed range. In addition to providing single fault data, this dataset also provides multiple composite bearing fault data, covering multi-channel bearing vibration signals with a wide speed range under different loads. The dataset well supports the research of classic fault diagnosis algorithms, and due to the large speed range covered by the data and high-speed sampling rate, it is more conducive to training deep learning fault diagnosis models.

Traditional algorithms are difficult to effectively separate and extract the composite fault features of bearings with overlapping resonance bands, an adaptive rolling bearing composite fault feature separation and extraction method combining adaptive variational mode extraction (AVME) and optimized multi-point optimal minimum entropy deconvolution adjusted (OMOMEDA) is proposed in this paper. The initial value of the center frequency of the VME parameter is determined by using the autocorrelation energy spectrum of S transform spectrum, and the desired modes related to the fault are extracted. Then the desired modes are linearly superimposed to reconstruct the original signal to realize the noise reduction of the signal. Extract periodic pulse signals from the reconstructed signal using OMOMEDA, and obtain fault characteristic frequencies by combining with envelope demodulation. The simulation and test signals verify that the method can effectively separate and extract the composite fault features of bearings with overlapping resonance bands. And compared with four other existing algorithms such as VMD-MCKD, the superiority of the proposed method is demonstrated.

Support matrix machine is an advanced matrix learning model that can fully utilize the intrinsic structural information in matrix data. However, it is susceptible to noise and outliers, and lacks generalization ability in imbalanced data. To this end, a robust cost-sensitive support matrix machine (RCSSMM) model is proposed and applied to intelligent diagnosis of wind turbine gearbox faults. RCSSMM improves the robustness to noise and outliers by evaluating the prior distribution of the matrix input with assembled matrix distance, and assigning different sample weights to different samples. Additionally, RCSSMM introduces the cost-sensitive loss function that assigns different penalty factors to different categories of matrix data. The optimal values of the penalty factors are adaptively determined with the Harris hawk optimization algorithm to focus on minority class samples and improve the diagnostic performance on imbalanced data. The proposed method is validated using simulated experimental data and real measured data of wind turbine gearboxes. The experimental results demonstrate that the RCSSMM model exhibits more outstanding fault diagnosis performance even under the presence of noise, outliers, and imbalanced data.

Tuned Liquid Damper (TLD) is a simple and effective passive vibration control device. By adding thickening agents to the TLD, the effect of liquid viscosity on the damping ratio and frequency of the TLD system is studied. Firstly, the relationship between thickener concentration and liquid viscosity is measured by a viscometer. Then, rectangular, circular, circular and U-shaped TLD tanks are designed and tested on a unidirectional harmonic excitation vibration table.The influence of parameters on the performance of the TLD is analyzed, such as thickener concentration, water depth ratio of the tank, external excitation frequency, relative excitation amplitude and placement time. Finally, CFD numerical simulation of TLD system is carried out to study the influence of tank size. The results show that increasing the concentration of thickener can effectively improve the damping ratio of TLD, and has little effect on the frequency of TLD. Water depth ratio has little effect on frequency and damping ratio of TLD. The external excitation amplitude and frequency have little effect on the frequency and damping ratio of the TLD system, but can significantly change the liquid surface wave height. The TLD placement time of the thickener liquid increased, resulting in a decrease in the viscosity of the liquid in the TLD, resulting in a decrease in the damping ratio of the TLD, partial volatilization of the liquid in the TLD, and a decrease in the water depth ratio, resulting in a phenomenon of TLD frequency mismatch. As the size of the tank decreases, the TLD damping ratio gradually increases, and the damping ratio remains basically stable when the size is larger.

The seismic performance tests of reinforced concrete (RC) shear walls and BFRP bars reinforced concrete (BFRP-RC) shear walls with different horizontal reinforcement ratios (0.25% and 0.50%) were carried out to explore the similarities and differences in seismic performance between RC and BFRP-RC shear walls. And the horizontal reinforcement ratio was expanded to 0% and 1.00% in meso-scale numerical simulation. The influence of reinforced materials type on the seismic performance of shear walls was discussed, and the shear capacity, deformation capacity, energy dissipation capacity, stiffness and recovery performance of RC and BFRP-RC shear walls were compared. The test results show that the shear failure and compressive shear failure occurred respectively in the shear walls with horizontal reinforcement ratios of 0%~0.25% and 0.50%~1.00% under horizontal cyclic load. The horizontal reinforcement ratio has the same effect on the failure mode, shear capacity, deformation capacity and energy dissipation capacity of RC shear wall and BFRP-RC shear wall; that is, increasing the horizontal reinforcement ratio can enhance the seismic performance of shear walls. However, the seismic performance of RC and BFRP-RC shear walls is different. Under the two horizontal reinforcement ratios, the shear capacity of the BFRP-RC shear wall is about 74%~78% of that of the RC shear wall, the deformation capacity is about 47%~84%, and the initial stiffness is about 77%~84%. Because the BFRP bar is always in the elastic deformation stage during loading, the recoverability of the BFRP-RC shear wall is significantly stronger than that of the RC shear wall. When the horizontal reinforcement ratio is 0.25% and 0.50%, the residual deformation of BFRP-RC shear walls is 62% and 13% of that of RC shear walls, respectively. The recoverability of the BFRP-RC shear wall is more in line with the requirement of recoverable functional aseismic structure in practical engineering.

The present paper proposes an hybrid base isolation system referred to as BRB+NFVD+BIS, consisting of the buckling restrained braces (BRB), nonlinear fluid viscous dampers (NFVD), and base isolation system (BIS) to study both the damping and isolation effects of the hybrid base isolation system on prefabricated high-rise buildings. Defined are the ratios of both BRB yield strength to base isolation yield strength and the total damping index of NFVD to base isolation yield strength, respectively designate as BIR and NIR. Based on the dynamic elastic-plastic seismic response analysis of the corresponding systems, the effects of BIR, NIR, and NFVD parameters on the seismic performance of BRB+NFVD+BIS tall buildings have been revealed, and the ranges of BIR, NIR, and NFVD parameters are suggested. Results demonstrate that with respect to the non-isolated prefabricated high-rise buildings, the BRB+NFVD+BIS system can significantly enhance the seismic performance of beam-column connections, reduce both the inter-story drift ratios and floor accelerations of the superstructure. Compared with the base-isolated prefabricated high-rise structures, the BRB+NFVD+BIS system substantially reduces base isolation layer displacement while maintaining almost the same seismic performance to each other in terms of the beam-column connections, inter-story drift ratios, and floor accelerations Therefore, the BRB+NFVD+BIS system processes better displacement control ability of isolation layer. Simultaneously, the results show that the BRB+NFVD+BIS system has better robustness of both the seismic mitigation and isolation.

There exists the nonlinear failure correlation among the multiple monitoring points of bridge components. Considering the influence of this factor on the reliability indices of the bridge, this paper adopts the Bayesian optimized long short-term memory (BO-LSTM) network model in machine learning to dynamically predict the monitoring data of the bridge, and establishes a three-dimensional Gaussian Copula model based on Copula theory to calculate the time-varying reliability indices and failure probability of the bridge construction. The rationality of the model and method is verified by applying the monitoring data of Fumin Bridge in Tianjin.

This study aims to investigate the life-cycle seismic performance degradation behaviour of reinforced concrete (RC) girder bridges under chloride-induced corrosion. Based on the Duracrete model and existing research results, the time-dependent deterioration models for the mechanical properties of longitudinal reinforcement, transverse reinforcement, cover concrete, and core concrete are determined. A three-span RC continuous girder bridge is taken as an example, and its nonlinear analysis models corresponding to different characteristic time points are established by the OpenSees platform. Four analysis cases are investigated to study the effects of chloride-induced corrosion on the girder bridge's seismic capacity and seismic demand. Among these cases, one involves the omission of considering the deterioration of ultimate tensile strain of reinforcing steel, while the remaining three consider this deterioration using three diverse degradation models. The results show that: in the presence of chloride-induced corrosion, the degradation of the ultimate tensile strain of reinforcing steel manifests markedly more severe than the deterioration observed in its yield strength; the girder bridge suffers a more significant decrease in ultimate curvature, a greater increase in curvature demand, and a lower curvature demand-to-capacity ratio of pier when considering the deterioration of ultimate tensile strain of reinforcing steel; disregarding the degradation of the ultimate tensile strain of reinforcing steel would render the life-cycle seismic performance evaluation results of girder bridge structures unreliable and unsafe; additionally, the applicability of these three deterioration models varies, and there are significant differences in the degree of degradation of curvature demand-to-capacity ratio among these models. Therefore, the choice among these three models should be grounded in the research application scenario. As a result, it is necessary to consider the deterioration characteristics of the ultimate tensile strain of reinforcing steel in the time-dependent seismic performance evaluation of RC girder bridges.