To study the vibration influence of urban rail transit on buildings along the line, a frame-shear wall structure near a subway was selected as the research object. Under the excitation of rail transit vehicles, vibration monitoring of typical buildings was carried out at the foundation, along the height direction and the horizontal direction of the building, and the evaluation criteria such as 1/3 octave plumb vibration acceleration level, peak acceleration, and plumb fourth power vibration dose value were used for the analysis. The research results indicate that when the structure is 55 meters away from the inner contour of the tunnel, significant subway-induced vibration can still be detected inside the structure, and the relevant evaluation values may exceed the regulatory limits. In addition, the existing regulations do not specify the selection criteria for subway vibration, and the evaluation quantities determined by different value methods may seriously underestimate the impact of subway-induced vibration. Along the height direction of the structure, the vertical vibration response of the measurement points from the first underground level to the third above ground level did not significantly decrease, and there may be amplification at the top. The vertical vibration at the center of the floor slab is significantly amplified compared to the edge of the floor slab. The plumb fourth power vibration dose value at the center of the slab can reach 345% of that at the corner of the slab, and the corresponding maximum vertical vibration acceleration level can increase by 12.9 dB.

The M_S6.8 Dingri earthquake in Xizang on January 7, 2025, caused extensive building collapses and significant casualties. To investigate the causes of seismic damage, this study analyzed the amplitude-frequency characteristics and propagation attenuation characteristics of near-field ground motions using 35 sets of strong motion records obtained from the National Intensity Rapid Reporting and Early Warning Network. Through comparative analysis with the seismic ground motion prediction model (ZYLW22 model) for southwestern China, it was found that the measured values of near-field ground motion parameters (including peak ground acceleration and response spectra) were found to be slightly lower than the model predictions, while far-field observations exhibited higher values than predicted. Spectral analysis revealed a pronounced high-frequency energy dominance in the 1.0~3.0 Hz range within high-intensity zones of the earthquake. The epicentral region of the Dingri earthquake lies in a pastoral-agricultural area, where local buildings predominantly consist of self-built low-rise stone/wood or adobe structures and simple frame residential buildings. The earthquake disaster may be attributed to the poor structural integrity of these buildings, whose natural vibration periods closely match the predominant periods of ground motions, resulting in widespread structural failures. Additionally, the near-fault ground motions of the Dingri earthquake also exhibited source rupture directivity effects.

The urban lifeline engineering system, serving as a key infrastructure that ensures the daily lives of residents, the functional operation of the city, the healthy development of the economy, and the long-term stability of society, is the cornerstone of resilient city construction. Research on seismic resilience assessment methods for urban lifeline engineering systems has achieved certain progress both domestically and internationally. However, the seismic resilience design methods for urban lifeline engineering systems remain underdeveloped. This paper expounds on the concept of seismic resilience design for urban lifeline engineering systems and delineates the differences between seismic resilience design for urban lifeline engineering systems and traditional seismic design for individual urban lifeline facilities. The basic framework of seismic resilience design, characterized by the “two dimensions”, is put forward, which ensures the structural seismic safety of individual facilities through the structural safety design of individual facilities, and guarantees the post-earthquake functionality and rapid recovery of the engineering system through the resilience coordinated design among individual facilities. The basic requirements for seismic resilience design, characterized by the “three objectives”, are established, ensuring structural seismic safety of individual facilities, meeting predetermined functionality of individual facilities and the engineering system, and enabling rapid recovery of the engineering system. The key steps of seismic resilience design, characterized by the “four components” are proposed, which include determining the seismic resilience goals for the engineering system, structural safety design for individual facilities, post-earthquake functionality verification for the engineering system, and identification of technologies and strategies for the rapid recovery of the engineering system. A unified seismic resilience design approach for urban lifeline engineering systems is established. This paper takes a road transportation system as an example to conduct seismic resilience design. The preliminary results validated the rationality and feasibility of the proposed seismic resilience design approach. The design approach enables the transition of seismic design for urban lifeline engineering systems from structural seismic design, which ensures the structural seismic safety of individual facilities, to seismic resilience design, which ensures post-earthquake functionality and rapid recovery of the engineering system. The proposed approach can also provide a practical solution to improve their seismic resilience.

Following the M_S6.8 Dingri earthquake in Xizang, China, on January 7, 2025, extensive sand liquefaction phenomena were observed in Ⅷ~Ⅸ intensity zones, providing critical field data for studying liquefaction in high-altitude settings. This investigation employed field visits and surveys to explore the macroscopic characteristics, spatial distribution, and disaster-inducing mechanisms of liquefaction. Sand boils were documented in villages, embankments, floodplains, and lakeshore areas. The microscopic morphology and mineral composition of ejected materials were analyzed. Several recommendations for seismic liquefaction disaster prevention and mitigation are proposed. Key findings include the following. Sand boils predominantly occurred in river floodplains, lakeshores, and along roads, exhibiting circular, fissure, and beaded distribution patterns. Circular features measured 10~50 cm in diameter, while fissures spanned 14~30 cm in width and 85~100 m in length, distributing in sporadic or continuous clusters. No significant sand boils were observed in surveyed towns or villages. Two liquefaction sites of comparable size, distance and volume near the G219 national highway Gading line demonstrated contrasting damage levels: one section remained intact, while the other experienced severe subsidence, pavement collapse, and guardrail deformation. the characteristics of two sand boils feature in fissure and circular patterns. To bridge the gaps between liquefaction risk assessment and anti-liquefaction strategies, characterization and analysis of disaster-inducing mechanisms should be an essential research topic for the development of seismic liquefaction disaster prevention and control technology. The information and results of the investigation provide a reference for the understanding of seismic liquefaction mechanisms and informing post-disaster reconstruction and liquefaction disaster prevention.

On December 18, 2023, a M_s6.2 earthquake occurred in Jishishan County, Gansu Province, affecting 118 towns including Dahejia Town, Liuji Town and Shiyuan Town. The areas have a relatively low level of economic development, with widespread and severely damaged brick (earth) and wood structures, resulting a significant number of casualties. In view of the large stock of brick-wood buildings in the region and their local characteristics, this study summarizes the architectural and structural characteristics of double-slope brick-wood structures and single-slope high wall brick-wood structures based on the on-site research, analyzes the typical earthquake damage phenomena and mechanisms, discusses the seismic vulnerabilities of existing brick-wood structures, and proposes the corresponding improvement measures in combination with the actual needs of rural construction. The findings indicate that in the epicentral area, most of the brick-wood structures are moderately damaged or severely damaged, and a few are destroyed. Structures with a mix of brick column and earth wall load-bearing and single-slope high-wall structures suffered more severe damage compared to double-slope brick-wood structures. The damage can be classified into four categories including overall or partial collapse, roof damage, wall damage, and other damage. The primary causes of the damage are identified as irrational structural systems, low mortar strength, poor overall integrity, and the absence of effective seismic construction measures. Consequently, this paper suggests targeted improvement measures to enhance the overall integrity, increase the collapse resistance of the walls, and prevent the collapse of roof components. These measures aim to provide a scientific basis and practical guidance for improving the seismic resilience of rural dwellings and optimizing disaster prevention and mitigation strategies.

Jishishan earthquake caused serious damages to buildings in some areas of Gansu Province and Qinghai Province. The seismic damages of rural buildings at 11 survey points were investigated in areas with seismic intensities of 7 and 8 degrees. The seismic damage investigation shows that the earthquake disaster regions are mainly areas of towns and villages, and the main types of house structures are civil structure, brick and wood structure and unfortified brick concrete structure. In areas with intensity 8 degree, houses of civil structure mainly perform as severely damaged or collapsed. Brick wood structure and unfortified brick concrete structure houses were mainly damaged moderately and severely. Fortified brick concrete and reinforced concrete frame structure houses were damaged slightly and moderately. In areas with intensity 7 degree, civil structure houses were mainly damage moderately. Brick wood structure and unfortified brick concrete structure houses mainly damage slightly and moderately. Fortified brick concrete and reinforced concrete frame structure houses were mainly damaged slightly and basically intact. The seismic damage caused by the earthquake is more severe than that of earthquakes with the same magnitude, which is related to factors such as the amplification effect of ground-motion peak values of complex terrain in the earthquake area, poor quality of building masonry, and unreasonable structural stress of buildings. It is recommended to carry out further research on site amplification effect and spectrum impact of complex terrain, and attach importance to the earthquake resistance promotion and practical technology development of non-structural components of buildings.

Strong ground motion data serve as the basis for establishing ground motion models. It is difficult to establish ground motion models in areas lacking sufficient strong motion data. This paper reviews several methods for establishing ground motion models in areas lacking strong motion data, including the numerical simulation method, the hybrid empirical method, and the referenced empirical approach. The numerical simulation method employs high-frequency and low-frequency ground motions simulated by stochastic and deterministic methods, respectively, to develop ground motion models. The hybrid empirical method can effectively solve the problem of lack of data by combining numerical simulation and actual observation data and applying the empirical ground motion model of the reference area to the target area by using the adjustment factor. The referenced empirical approach is based on the small earthquake records in the study area and adapts the existing empirical ground motion model to suit the specific regional situation with simplicity and effectiveness. Each of these three types of methods has its own characteristics, numerical simulation methods can take into account the characteristics of the seismic source, complex geological and site conditions, and the calculation results depend on the accuracy and precision of the source model and the subsurface velocity structure. The hybrid empirical method combines the flexibility of numerical simulation methods and the statistical characteristics of observed data, and can establish a relatively reliable model. The referenced empirical approach is quicker and simpler but is dependent on the data of the small earthquakes. Finally, this paper suggests that artificial intelligence and multi-source data fusion can be used to improve the accuracy and reliability of ground motion model in areas lacking strong motion data.

The seismic damage of rural dwellings in the M_s 6.2 earthquake in Jishishan is explored. The structural characteristics, construction habits and construction techniques of the rural dwellings in the disaster area were summarized. The collapse and typical earthquake damage characteristics of rural dwellings with different structural forms were analyzed. The mechanisms of traditional building practices on the seismic resistance and disaster prevention capability of residential houses were studied. The results of the research and analysis show that the structural systems of rural dwellings are mostly “tiger hugging head” style brick-wood structure, accounting for 50.9% of the total number of researched houses, and there are fewer cases of earthen structure and brick-concrete structure, accounting for 28.2% and 20.9%, respectively. There are many cases of the overall collapse of the earthen structure in the study area, fewer cases of overall collapse of brick-wood structure, and no cases of total collapse of brick-concrete structures. The earthquake damage of brick-wood dwellings mainly consists of cracking at the corners of the gable walls, dislodging at the joints, partial collapse of the gable walls, and cracking of roof laps. The main earthquake damage to earthen dwellings is damage to the corner of the gable wall, collapse of the gable wall, and collapse of the roof. Earthquake damage to brick-concrete structure mainly consists of wall cracking, wall collapse and floor (roof) damage. Bad construction habits such as mud joints, thick-covered loess roofs, and large-weight door decorations exacerbated the earthquake damage to residential houses and should be improved in the subsequent restoration and reconstruction work. Measures and suggestions to improve the earthquake-resistant and disaster-preventive capacity of rural dwellings were put forward with regard to the seismic damage characteristics of different structural systems and construction habits, with a view to providing reference for the construction，strengthening and renovation of rural dwellings in the disaster areas.

To study the comfort level of human-induced vibration of a variable section steel-truss pedestrian bridge and the vibration reduction effect of tuned mass damper (TMD), a steel truss girder pedestrian bridge on the Beijing Hangzhou Grand Canal was taken as the research object. Finite element simulation and on-site measurement were used to study the human-induced vibration response of the steel truss pedestrian bridge. Based on the finite element model, the vibration response of the bridge before installation of TMD was analyzed, the pedestrian comfort level was determined, and the influence of pedestrian density, damping ratio and crowd excitation frequency on the bridge was discussed. In this way, the TMD design parameters were given, and the influence of TMD mass ratio on the vibration reduction effect was analyzed. On site measurements were conducted on the pedestrian bridge after the installation of TMD, and based on which acceleration time history and frequency spectrum analysis were used to study the human-induced vibration response of the bridge under corresponding operating conditions. Comparison of the results shows that before installing the TMD, the acceleration response of the bridge exceeds the specification limit, and the effect of human-induced vibration should be considered. In a certain range, the acceleration response increases with the increase of pedestrian density and decreases with the increase of damping ratio. The vibration response increases significantly when the pedestrian step frequency is close to a certain order of the vibration frequency of the bridge. After the installation of TMD, the measured human-induced vibration response of the bridge is reduced, and its response is consistent with the simulation results. The research results in this paper can provide theoretical support for the study of human-induced vibration of variable section steel truss bridge.

On Dec. 18th, 2023, a magnitude 6.2 earthquake hit Jishishan Town of Linxia City in Gansu Province, and caused an unusual mud sliding disaster in Jintian Village and Caotan Village of Zhongchuan Town in Qinghai Province. The mud flowslide resulted in catastrophic consequences as casualties and demolishing and burying of residential houses. Such large mud sliding phenomenon has not been frequently reported in historical earthquakes. Through field investigation, it is confirmed that the underlain soil liquefied and triggered the disastrous phenomenon which has already been termed liquefaction-induced flowslide. Nevertheless, the massive liquefaction-induced flowslide is the first time been reported and verified by field evidence in recent 70 years. The investigation and analytical results demonstrate that the underlain soil layer in the upstream area liquefied, triggering instability and catastrophic flowslide, and the soil and water conditions in the flowing channel potentially accelerated the sliding. It is deduced that liquefaction possibly occurred in many a place, that is, the sliding channel was suspected of liquefying in various spots. The ground shaking intensity in the sliding area maintained relatively high, and that the peak ground-motion acceleration was estimated around 0.4 (±0.1) g. The findings and investigation results are useful to help understanding the mechanism and process of the uncommon flowslide disaster.