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.

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%.

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.

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.

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.

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.

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.

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.

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.