This paper investigates the effects of spatial effects of seismic ground motions on the seismic responses of long-span cable-stayed bridges, considering their large range and notable variations in local site conditions. Shaking table tests were conducted on a cable-stayed bridge, and the dynamic responses (acceleration, displacement, and strain) of critical sections of the cable-stayed bridge were compared and analyzed. The results demonstrate the significant influence of spatial effects of ground motion on the dynamic responses of the cable-stayed bridge. Specifically, the analysis reveals that the wave passage effect has the least impact on the dynamic responses of the cable-stayed bridge, followed by the combined effect of the wave passage and coherence, while the combined effects of the wave passage, coherence, and local site conditions exert the largest influence. Taking the main tower as an example, the maximum acceleration, displacement, and strain responses increased by 55.69%, 62.37%, and 67.37%, respectively, when spatial seismic motions incorporating the wave passage effect, coherence effect, and local site effects were considered, as compared to uniform excitation. Consequently, the seismic responses of cable-stayed bridges may be underestimated if only uniform excitation or the wave passage effect is considered. It is therefore imperative to comprehensively account for the effects of wave passage, coherence, and local site conditions of the spatial ground motion in the dynamic response analysis of long-span cable-stayed bridges.

As more and more water conservancy projects are constructed in the seismogenic fault zone in the western region, the probability of water conservancy projects encountering near-site vibration is also increasing. Due to the shallow buried depth of near-fault ground motions, the assumption of vertical incidence of seismic waves is no longer applicable. At present, there is little research on the seismic response of the intake tower under the oblique incidence of near-fault ground motions. In this paper, taking an engineering intake tower as an example, a three-dimensional plastic damage finite element analysis model of the intake tower is established, and the nonlinear response analysis of near-fault pulse ground motion SV wave under multi-angle oblique incidence is carried out. The results show that the displacement response of tower top under the oblique incidence of near-fault ground motion SV wave increases significantly, and the damage area and damage degree of tower body increase with the increase of angle.

By combining the partial self-centering shape memory alloy(SMA) braces (SCB) with the shear slotted bolted connection-very short shear link (SSBC-VSSL), an innovative self-centering shear link (SC-SL) used in the eccentrically braced frame (EBFs) that has an advantage of good energy dissipation capacity and self-centering capacity, low damage and excellent seismic resilience capacity is developed. Cyclic tests were carried on SC-SL specimens designed by the proposed method, so the deformation modes and hysteresis curves can be obtained. Based on the test results, ten SC-SL models with the effect of SMA areas, high-strength bolt pretensions and shim friction coefficients were designed and analyzed by the validated finite analysis (FE) method. The results show that the VSSL is in the relative static during the slip stage, then the development process of very short shear link (VSSL) in SSCB-VSSL including yield, bearing, energy dissipation and inelastic deformation are appeared sequentially during the non-slip stage, while the SMAs in SCB are always subjected to elongation, thus increasing the energy dissipating capacity and self-centering capacity. Finally, the simplified mechanical models of SC-SL in the slip stage and non-slip stage are proposed by using the FE results, which can provide a new way to give important seismic design reference for EBFs.

In this study, based on the extended Kalman filter (EKF), an approach is proposed for identifying unknown ground motion time history and structural parameters by using the absolute acceleration measurements. First, the interfacial force of the lower boundary of the 1st floor is considered as the unknown excitation. The EKF-based approach is employed for the identification of this unknown excitation and the remaining structural stiffness parameters. Then, by using Fourier transform, the structural natural frequencies can be obtained from the acceleration measurements and used for identifying structural stiffness of the 1st floor. Finally, based on these identified structural parameters, the unknown interfacial force mentioned above is updated and employed for identifying ground acceleration with the aid of Newmark-β method. The effectiveness of the proposed approach is validated via a numerical frame structure and a five-story experimental model under shaking table tests.

In order to study the mechanism of pile-soil-structure dynamic interaction and analyze its influencing factors, the horizontal dynamic response laws of pile-soil-structure system under different superstructure mass, different input wave frequency and acceleration peak input are analyzed and discussed by using the method of shaking table test and numerical simulation analysis. The soil model of the test foundation is medium hard soil, and the shear speed is about 213 m/s. The pile group foundation is composed of five foundation piles with a length of 1.35 m and a diameter of 0.1 m arranged in cross shape. The superstructure model is simulated by mass block. The experimental results show that the bending moment and shear force of pile body are the largest at the pile-bearing joint, and decrease with increasing depth. With the increase of the superstructure mass, the acceleration reaction between soil and pile foundation increases significantly, and the bending moment and shear force of the pile body also show an increasing trend. With the increase of the input sine wave amplitude and frequency, the motion interaction becomes larger, and the bending moment and shear force in the pile body become larger. The change of superstructure quality has the greatest impact on the dynamic interaction of the pile-soil-structure system, followed by amplitude and frequency.

To investigate the impact of socket depth on the seismic performance of socket structures, a group of a cast-in-place pier and precast piers considering the variation of socket depth were designed and fabricated, of which the socket depths of the socket piers were 1.0d (where d represents the side length of the square pier), 0.8d, and 0.6d, respectively. Pseudo-static tests were conducted to analyze the damage patterns, hysteresis performance, and energy dissipation capacity of the piers, allowing for an examination of the influence of socket depth on their behavior. The test results demonstrate that the bearing capacity of the four groups of specimens is similar. The socketed piers with a socket depth of 1.0d exhibit damage patterns and hysteresis curves that are comparable to those of cast-in-place piers, indicating equivalent seismic performance. However, the ductility of the socket piers with embedment depths of 0.8d and 0.6d is weaker than that of the cast-in-place piers due to damage to the footing. By comparing the damage phenomenon, the relative relationship between the shear bearing capacity of the footing sidewall and the ultimate bearing capacity of the column is analyzed under the existing reinforcement ratio. As the socket depth of the pier decreases, the shear capacity of the groove sidewall decreases. This increases the probability of damage to the groove sidewall due to the reduced shear bearing capacity. Therefore, it is crucial to consider the relative relationship of the bearing capacity between the footing and the column when selecting the socket depth in the design to prevent damage in the footing position.

The braking behavior of trains will notably affect the longitudinal movement of suspension bridges. Therefore, it becomes imperative to delve into the longitudinal movement of kilometer-level railway suspension bridges under the influence of train braking. This study takes a long-span railway suspension bridge with a main span of 1060 meters as its research object, and explores the response characteristics of its longitudinal movement at the girder end when subjected to train braking forces and the controlling effect of a fluid viscous dampers (FVDs) by numerical simulation. Firstly, the engineering background of the kilometer-level railway suspension bridge and the finite element model established using ANSYS software are introduced. Then, the loading and solution methods for the longitudinal movement of the long-span railway suspension bridge, the finite element simulation methods for bearing friction and FVDs, and the simulation method for braking force are described. Subsequently, the effects of different braking positions and consideration of bearing friction on the longitudinal movement response of the suspension bridge are investigated. Finally, the control effect of FVDs on longitudinal movement is studied, and parameter analysis is conducted. The results show that as the braking position approaches the point where the train exits the bridge, the shape of the longitudinal displacement curve becomes more similar to a sine function. Bearing friction has a certain control effect on the displacement response at the girder end under train braking, but its control effect on the velocity response is not ideal. The utilization of FVDs effectively controls both displacement and velocity responses at the girder end of the suspension bridge under train braking. The optimal control effect is achieved when using a FVD with a damping coefficient of 2500 kN•(m/s)^-α and a velocity exponent of 0.1.

The safety of cross-active fault tunnels poses a significant challenge in current railway engineering construction. Research on such tunnels primarily relies on numerical simulation. However, the refinement level of the finite element structural models used to analyze cross-fault tunnels is often inadequate, and it is difficult to accurately reflect the actual stress and deformation characteristics of the tunnel structure under fault displacement. The influence of invert-filling, railway track foundation, and steel rails are considered in this paper. Three tunnel structure models with different levels of refinement are established by using the finite element software ABAQUS, and the simplified and commonly used ring structure models are compared. The stress and deformation characteristics of the cross fault tunnel structure and its associated track system under the action of active reverse faults are analyzed in detail. The results indicate that the refinement level of the model significantly affects the stress levels and deformation calculation results of the tunnel structures. The longitudinal stiffness and integrity of the tunnel structure are strengthened when considering bottom filling layers and internal auxiliary structures, and the ability of the structure to resist fault is improved. Meanwhile, in light of the severe damage to tunnel tracks and ancillary facilities during the M6.9 earthquake in Menyuan, Qinghai, in 2022, a dedicated study is undertaken to further examine the mechanical behavior and deformation characteristics of tracks under strike-slip fault displacement. This analysis is based on a refined tunnel model, aiming to gain a deeper understanding of how tracks respond and deform under such geological forces.

Aiming to accurately differentiate between natural and non-natural earthquakes, a neural network model based on one-dimensional convolution and residual structures, named ResNet-1D, was constructed. This model automatically extracts features from three-component seismic records using convolutional layers with convolutional kernels of different lengths, pooling layers composed of max-pooling, and residual structures. The adaptive moment estimation method (Adams) is used to optimize parameters, and a linear discriminant function (Linear) is applied to distinguish between natural and non-natural earthquakes. Using 40000 velocity records of natural and non-natural earthquakes, compiled by the China Earthquake Networks Center from 2008 to 2020, the data was randomly divided into training, validation, and test datasets in a 6∶2∶2 ratio. The test results show that the classification accuracy for natural and non-natural earthquakes is 92.65% and 94.30%, respectively. Compared with traditional machine learning methods, the ResNet-1D model significantly improves the test results in terms of accuracy, precision, recall, and F1 score, effectively enhancing the accuracy of identifying natural and non-natural earthquakes. Moreover, variations in magnitude and epicentral distance also affect the classification accuracy of the model, with higher magnitudes and greater distances resulting in lower accuracy. The model proposed in this paper offers higher accuracy and provides technical support for accurately distinguishing between natural and non-natural earthquakes in seismic monitoring.

In order to study the seismic performance of the new adobe wall structural system. A one-story foot-scale new adobe wall building test model with plan size of 3.6 m×3.0 m and storey height of 2.45 m was designed and fabricated for the shaking table test, and El Centro waves and Yunnan Ludian (LD) waves were selected for the test to carry out unidirectional loading of seismic waves in the X and Y directions, respectively, and the test model was measured to be under the peak acceleration of 0.10、0.22、0.40、0.62、0.90 g, the spectral characteristics, acceleration response, displacement response, torsion response, and strain response of the dark column reinforcement were measured. The results show that: the model is only slightly damaged in the exceeding 9 degree rarefied intensity, and there is no obvious cracking and damage phenomenon under other seismic excitations. With the increase of seismic excitation, there is no obvious change in the self-resonance frequency of the model, and the acceleration amplification coefficient gradually decreases, with the maximum amplification coefficient of 3.666 at the roof. The angle of the interstorey displacement reaches the maximum of 1/399 when the peak acceleration is 0.62 g. The overall structural torsion is 1.599 at the peak acceleration of 0.62 g, and the displacement angle of 0.62 g reaches the maximum of 1/399. Because of the basic homogeneous symmetry, the structural torsion is 0.666 at the roof. Because the model is basically homogeneous and symmetric, the overall torsional effect of the structure is not obvious. The strain value of the steel reinforcement of the dark columns increases gradually with the increase of the seismic excitation, but the strain value of the steel reinforcement is small and the performance of the steel reinforcement fails to give full play. In summary, the new adobe wall model has good seismic performance, and the study provides a test basis for expanding the application range of adobe buildings.