To study the longitudinal seismic response and damage state of the high-speed railway track-isolation bridge system, a 7-span 32 m simply supported beam bridge with CRTSⅢ type ballastless track structure laid on the bridge deck was taken as the research object. A finite element model of the track-bridge system was established, and the seismic response distribution law of each key component under different seismic waves, seismic intensity and bearing types was obtained through nonlinear time-history analysis. The results show that the longitudinal displacement of the beam body presents a stepwise distribution under longitudinal seismic excitation, with the maximum value occurring at the center of the bridge span. The maximum displacement of the fastener occurs at the expansion joint of the abutment, and extreme values appear at the expansion joint at each beam end. The displacement of the fastener is significantly affected by the spectral characteristics of different seismic waves. The maximum stress of the rail occurs at the expansion joints on both sides of the side span, and the normal stress of the composite slab section is caused by the combined action of axial force and bending moment components. After the bearing and track system enter the nonlinear state, compared with the increase in seismic intensity, the increase in longitudinal deformation of the vulnerable components shows a significant amplification effect and distribution imbalance. Considering the track system, compared with the friction pendulum bearing, the same ball direction double spherical surface bearing can significantly reduce the displacement response of the fastener, beam body and bearing. The track system has a significant inhibitory effect on the displacement of the bearing.

Mountain terrain of significantly alters the propagation path and energy distribution characteristics of seismic waves. Through interactions such as reflection, scattering, and diffraction, the seismic response of local sites exhibits notable spatial variability. This terrain effect has a significant impact on the seismic response of engineering structures in mountainous areas and is one of the key factors contributing to the intensification of earthquake damage. To consider the impact of terrain effects on ground motion parameters in engineering seismic design, this study uses a railway station building site as the example. A three-dimensional finite element model of the mountain area where the station building is located was established. A viscoelastic artificial boundary is set for the model, and historical seismic data recorded by observation stations in the region were used as the ground motion input. The seismic response of the mountain region was obtained, and a comparative analysis of the input seismic motion and response results was performed to analyze the impact of the mountain height difference on the terrain amplification effect. The results show that at higher elevations (such as the freight yard and station building locations), the amplification effect is significant, while at lower elevations, the amplification effect is weaker, displaying a characteristic distribution along the height difference from large to small. The highest elevation of the site is more sensitive to high-frequency (10~20 Hz) seismic motion components. The peak ground acceleration is significantly positively correlated with the height difference, indicating that the height difference of the mountain terrain is a key factor influencing the site amplification effect. The study concludes that the terrain amplification effect is closely related to the height difference and topographical variations in mountainous areas, providing important theoretical guidance for the seismic design of major engineering projects in mountainous regions.

Water pipelines are important lifeline engineering. In order to study the seismic dynamic response law of up-down large diameter water pipelines crossing at short distance. A series of shaking table tests with a model similarity ratio of 1∶10 were conducted to study the seismic response law of large diameter water transmission pipelines in close proximity. The acceleration response and strain response of the structure and soil layer under single pipeline structure and cross pipeline conditions were compared and analyzed. The analysis results show that underpass pipelines have a complex impact on the acceleration response of the upper pipeline, depending on the size of the load, site dynamic characteristics, etc; When the input peak values of El-Centro are 0.1 g and 0.2 g, the downward crossing of the pipeline reduces the acceleration of the upper pipeline by 28.0% and 7.9%, respectively relative to a single pipeline. However, when these valuses of El-Centro are 0.4 g and 0.6 g, the peak acceleration of the upper pipeline increases by 4.9% and 39.5% relative to the acceleration of a single pipeline. The underpassing pipeline reduces the peak value and increases the bandwidth of the Fourier spectrum of acceleration when passing through the pipeline. The maximum strain peak of the pipeline occurs at a 45° between the lower part of the pipeline and the horizontal plane, which is 3.6% to 39.0% lower than the peak strain of a single pipeline.

The Great East Japan Earthquake on March 11, 2011, triggered a massive tsunami that caused devastating destruction to buildings in coastal cities. However, in areas unaffected by the tsunami, buildings experienced relatively fewer collapses or severe damage, despite the high seismic intensity. This study explores the characteristics and impacts of seismic damage from this earthquake, reveals the intrinsic relationship between ground motion features and building damage, and analyzes the seismic damage data and spatial distribution of building clusters using a vulnerability model established based on the 1995 Great Hanshin Earthquake. Through the analysis of building collapse rate, we found that the computed results closely aligned with the actual seismic damage survey outcomes. The analysis indicates that seismic damage was concentrated in coastal areas such as Miyagi, Fukushima, and Ibaraki Prefectures, particularly in narrow inland zones near the coastline. Notably, the areas most severely affected were not always the closest to the epicenter or the zones with the highest intensity. Furthermore, significant differences in collapse rates were observed across different building codes, with buildings constructed under newer regulations showing a markedly lower collapse rate compared to those built under older standards. This research contributes to a better understanding of the seismic damage characteristics associated with offshore earthquakes, providing crucial insights for earthquake defense and disaster relief efforts.

To systematically study the influence of near-fault pulse characteristics on the seismic response of skew bridges, a four-span highway skew continuous girder bridge was taken and finite element models of the skew bridges with different skew angles were established by using OpenSees. The near-fault pulse-like ground motions with high-frequency components were artificially synthesized by using the decomposition-incorporation method. The effects of the moment magnitude and fault distance to the piers, main girders, beam-abutment collisions and exterior shear keys of skew bridges are analyzed. The results show that the sensitivity of the top displacement of the middle pier to the moment magnitude is greater than that of the side piers, but the sensitivity to the fault distance is not much different. The increase of the moment magnitude increases the displacement and rotation ratio of the main girder, as well as the maximum pounding force between the girder and the abutment. The results of increasing the fault distance are opposite to the previous results and the rotation ratio of the girder varies most when the skew angles is 15°. It is suggested to strengthen the shear reinforcement of the exterior shear keys for skew bridges with skew angles greater than 15°. As the moment magnitude is greater than 6.0 or the fault distance is 2~7 km, the exterior shear keys are in a state of failure under the near-fault ground motion.

Ground motion has significant uncertainty, and different ground motion response spectra under the same amplitude have significant differences, which have a significant impact on the estimation of seismic damage to regional buildings. This study developed a regional building seismic damage simulation program suitable for multiple-story masonry and concrete frame structures, which can conveniently and quickly simulate regional buildings seismic damage under set earthquakes, and performed regional building damage simulations and probabilistic analysis with motion uncertainties. A typical urban region in Chifeng city was selected as the research area: 30 ground motions were selected to consider their uncertainty, and the ground motions amplitudes were modulated to the set intensity (0.05 g, 0.10 g, 0.20 g, and 0.40 g). Then seismic damage simulation of regional buildings under single and multiple seismic inputs were conducted respectively, the impact of seismic uncertainty on the seismic damage results of regional buildings was analyzed. Based on the seismic damage results under the set intensities, a probability density distribution model of regional buildings damage index based on Beta distribution was established. Results indicate that multiple seismic inputs take into account the uncertainty of seismic motion, which can more scientifically and objectively reflect the seismic damage situation of regional buildings; The established Beta distribution model can be used to estimate the post-earthquake damage of buildings in similar areas. The research results can provide reference for regional buildings safety assessment and seismic fortification.

To address the issue of brittle failure induced by welding residual stress and inherent buckling failure of thin steel plates in conventional shear panel dampers (SPD), this paper proposes a novel prefabricated angle steel-constrained shear panel damper (PASPD). The structural configuration, operational mechanism, and distinctive features of the PASPD are comprehensively elucidated. Two prototype specimens were designed and manufactured for experimental investigation. Quasi-static low-cycle reversed loading tests were performed to evaluate the hysteretic behavior, energy dissipation capacity, and failure characteristics of the PASPD. Experimental results demonstrate that the PASPD exhibits stable hysteretic performance and superior energy dissipation characteristics. The study reveals that increasing the web plate thickness can delay the initiation of corner cracks but does not alter the fundamental failure mode of the PASPD. Appropriate boundary constraints using angle steel significantly regulate the stress and strain distribution within the PASPD, concentrating the deformation and energy dissipation in the central region. Compared with the traditional steel plate shear dampers, PASPD exhibits superior ductility performance and higher cumulative energy dissipation. The finite element simulation analysis demonstrates that the synergy between the flange connection plate and the side angle steel can optimize the shear force transmission path of the PASPD, guide the stress and strain distribution of its web to be more uniform, and form an ideal web shear energy dissipation mechanism, thereby enhancing the stability and hysteretic energy dissipation performance of PASPD.

Estimating the epicentral distance from a single station is a critical task in real-time earthquake early warning systems. To address the limitations of the traditional B-Δ method, which relies on limited P-wave information and exhibits significant prediction errors, this study utilizes strong-motion data from the Japan K-NET network. A 3-second time window of three-component acceleration waveforms is used as input to a convolutional neural network (CNN), which directly extracts feature information from the waveforms to establish a CNN-based epicentral distance estimation model (CNN-Dis). The results show that in the test dataset, by normalizing both the input data and labels, the CNN-Dis model achieves an mean absolute error (MAE) of 28.119 6 km and a standard deviation of 34.682 7 km, outperforming the model without normalization. Compared to the traditional B-Δ method, the CNN-Dis model improves the reliability of epicentral distance estimation. Moreover, the CNN-Dis model provides relatively reliable results for offshore earthquakes, in contrast to inland events. The CNN-Dis model enhances the accuracy of epicentral distance estimation to a certain extent and provides strong support for the iteration and performance optimization of earthquake early warning technologies.