The duration of ground motion can significantly influence the cumulative damage and failure levels of structures, but its impact on structural response is inadequately considered in current seismic design. To explore the effect of ground motion duration on structural damage, this study employs a spectral matching method combined with wavelet transform to select 115 ground motion records of varying durations from the Japan strong-motion database (K-NET). Earthquake damage spectra under two different restoring force models were calculated, and a comprehensive analysis was conducted on the effects of ground motion duration, yield strength reduction factor, structural natural period and other factors on the structural damage spectrum. Additionally, 585 natural earthquake records of varying durations and different site conditions were selected from the Pacific Earthquake Engineering Research Center (PEER) database. Taking into account the combined influences of ground motion duration, yield strength reduction factor, structural restoring force model, and site conditions, a damage spectrum prediction model was developed using a differential evolution algorithm. Compared with existing prediction models, the proposed model reduces relative errors by more than 40%, which offers improved accuracy for predicting damage spectra that consider the effect of duration. The results of this study provide valuable insights for structural seismic design and damage assessment when considering the impact of ground motion duration.

To reveal the effect of P-Δ on the residual displacement ductility demand of structures, the damage-based residual displacement ductility demand ratio spectrum μ_res of single degree of freedom (SDOF) systems was conducted based on the Park-Ang damage model. The data were statistically processed to evaluate the effect of soil type, elastic stability coefficient θ, ultimate ductility coefficient μ_u and hysteretic model on damage-based μ_res. A prediction equation was proposed to estimate damage-based μ_res of SDOF systems through regression analysis. The differences of μ_res based on damage approach and ductility approach were compared and analyzed. Results show that the error in the estimation of damage-based μ_res when mean values along the earthquake population are considered without any soil distinction is inside 10%. When the P-Δ effect is not considered, the influence of μ_u on damage based μ_res exceeds 20%. When the P-Δ effect is considered, the influence of μ_u on damage based μ_res exceeds 50%. The ductility-based μ_res tend to be conservative compared to the damage-based ones. Finally, the prediction equation for the estimate of damage-based μ_res is proposed, which can be applied to the evaluation of residual displacement ductility demand ratio and seismic resilience.

Under the offshore environment, RC structures in service experience rebar corrosion due to chloride ion penetration, and their seismic resilience is progressively weakened as service time increases. To investigate the effects of replaceable friction dampers and FRP bars on the life cycle seismic resilience of RC frame-shear wall structures, this paper examines conventional RC frame-shear wall (RCF-SW) structures and RC frame-FRP hybrid reinforced shear wall structures with replaceable friction dampers (RCF-FRSW-FD). The seismic responses of these structures at 0, 35 and 55 years of service are discussed based on the incremental dynamic analysis (IDA) method. Meanwhile, post-earthquake resilience indicators (repair cost, repair time, and casualties) of the two structures are systematically analyzed using the FEMA P-58 theoretical framework. The results show that, as service time increases, structural damage and repair costs rise significantly, repair time is prolonged, and overall resilience declines. Furthermore, the greater the ground shaking intensity, the more pronounced the impact of corrosion on structural deterioration. Compared with the RCF-SW structure, the shear wall employing the replaceable friction dampers and FRP bars can significantly reduce the seismic response and damage probability of the frame-shear wall structure. This combination also effectively enhances the seismic resilience of the structure throughout its life cycle.

Structural seismic response monitoring plays a crucial role in the earthquake damage assessment and evaluation of seismic resilience for urban building clusters. Addressing the issues of high cost and low prevalence of existing seismic sensors, this paper proposes a structural seismic response monitoring system based on surveillance cameras. The system develops a hierarchical line segment descriptor matching algorithm for building structures and introduces a time-history data extraction technique for structural seismic displacement responses based on line matching. This effectively resolves the challenge of targetless structural surfaces and indistinct natural feature points in real earthquake scenarios. Thereby, enabling real-time monitoring of inter-story drift at a sub-pixel level. The system has been successfully demonstrated in the world's first practical earthquake visual monitoring application at a middle school in Sichuan Province. The results show that even under complex and varying lighting conditions at night, the monitoring system maintains high accuracy, achieving sub-pixel-level inter-story drift monitoring with peak inter-story drift errors within 35% and structural natural frequency errors within 5%. Furthermore, the monitoring system adopts a lightweight design, with resource utilization rates of both the central processing unit (CPU) and graphics processing unit (GPU) below 15% when processing a single surveillance video, meeting the requirements for real-time multi-node processing and ensuring efficient system operation. Compared to traditional accelerometer solutions, the visual monitoring system eliminates the need for additional dedicated sensors, leveraging existing security surveillance equipment to construct a building cluster monitoring network. This approach not only enables dual-purpose use of existing surveillance cameras for both routine and emergency scenarios but also provides a new technological approach for seismic monitoring of urban building clusters.

This study investigates the influence of ground motion duration on the damping reduction factor through response spectrum analysis of single-degree-of-freedom systems with various damping ratio levels. The significant duration (D_S5-95) is chosen as the measure for ground motion duration. By using 84 pairs of long-duration (LD) and short-duration (SD) spectrally equivalent records, the effect of ground motion duration is decoupled from the acceleration spectral shape. The average damping reduction factors for the LD and SD sets are calculated within the range of natural periods from 0 to 6 seconds at different damping ratio levels. The effects of damping ratio, natural period, and D_S5-95 on the damping reduction factor are quantitatively analyzed. A nonlinear regression model is proposed to account for the influence of ground motion duration on the damping reduction factor, with the regression parameters provided. The results indicate that, for a linear single-degree-of-freedom system, the influence of ground motion duration on the damping reduction factor depends on the natural period and damping ratio. In the short-period range, D_S5-95 has no significant effect on the damping reduction factor、However, in the long-period range, the damping reduction factor tends to decrease as D_S5-95 increases.

Ground motions caused by seismic waves propagating to the near surface due to the rupture of an uncertain seismic source also have uncertainty. In this paper, the uncertainties of asperity intensity and rupture velocity are represented by random variables, and three rupture scenarios are set up to consider the uncertainties of asperity location and initial rupture location. The spatial distribution of ground motion parameters in the valley near a dip-slip fault with uncertainty is investigated. The influences of the fault distance and the dip angle on the uncertainty of the ground motion parameters in the valley are analyzed. The multiplicative dimensional reduction method is used to improve the computational efficiency of the uncertainty quantification problem, and the physical process from fault rupture to site response is simulated based on the boundary element method. The results reveal that the uncertainty of seismic source leads to the uncertainty of ground motions. The scattering of seismic waves by the valley leads to the non-uniform amplification of the uncertainty. The coefficient of variation (COV) of the peak acceleration of the vertical ground motion at the center of the valley can reach 0.27. There are violent fluctuations in the spatial distribution of the COVs of the peak velocities of the vertical ground motions of the mountains. The variability of the ground motion at the valley decreases with the increase of the fault distance, and it tends to stabilize when the fault distance is greater than 4 km. The variability decreases with the increase of the fault dip angle, and the maximum variability of the peak ground acceleration can be up to 4 times the COV of the asperity intensity.

As a typical slender structure, solar towers, which have been widely applied in recent years, are highly prone to significant vibrations under wind loads. Based on a 228.5 m-high solar tower, the wind-induced vibration control performance of Tuned Liquid Dampers (TLDs) was studied by wind tunnel tests. Firstly, a 1∶200 full aeroelastic test model of the solar tower was designed and fabricated, and the corresponding optimal parameters of the TLD were analyzed. Then, a miniature and multi-container TLD was designed for the aero-elastic test model, and wind tunnel tests for the model, both with and without the miniature TLD, were conducted respectively. Wind-induced responses of the tower, including top acceleration, displacement, base shear force and moment were measured. It was found that significant vortex-induced vibrations occurred within the range of the design wind speed (33 m/s). The results showed that wind-induced responses of the tower could be significantly suppressed by the TLD both in the cross-wind direction and the along-wind direction. With the installation of the TLD, the peak values of the top acceleration and displacement in the cross-wind could be reduced by 56.3% and 53.5%, respectively, and the corresponding reduction ratios for the base shear force and moment were 58.7% and 56.5%. At the design wind speed, the peak crosswind top acceleration and displacement were reduced by 48.4% and 40.3% , respectively, and the peak base shear force and bending moment were reduced by 65.4% and 45.5%.

Existing studies have shown that near-fault impulsive ground motions have a significant impact on the seismic performance of concrete gravity dams. However, current research on the vulnerability of concrete gravity dams under near-fault ground motions remains limited, and most studies use a single response parameter as the performance indicator, which makes it difficult to comprehensively characterize the seismic performance of gravity dams. Taking a certain engineering concrete gravity dam as an example, this paper establishes a unified plastic damage model of the dam-foundation system. Multiple measured near-fault impulsive and non-impulsive ground motions are selected. Then, it calculates the comprehensive damage index of the gravity dam is calculated using the method of efficacy coefficient combined with the modified weighting model. A logarithmic probability seismic demand model is established for PGA (peak ground acceleration) and three single indices including accumulated base sliding, relative displacement of the dam crest, and overall damage index, as well as a comprehensive response index. By combining the criteria for dividing damage levels for each index, vulnerability curves are obtained. The paper compares the characteristics of near-fault ground motion pulses and the influence of single and comprehensive response indices on the seismic performance of concrete gravity dams. The results indicate that the probability of concrete gravity dams experiencing minor, moderate, and severe damage under near-fault impulsive ground motions is higher than that under non-impulsive ground motions. Evaluating seismic performance using a single index may lead to overestimation of the dam's seismic resistance under certain PGAs. Using a comprehensive damage index as the performance indicator for evaluating the probability of damage and ultimate seismic capacity of gravity dams is more reasonable.

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.

This study analyzes 6 436 offshore ground motion records from 496 seismic events observed by seafloor observation network for earthquakes and tsunamis along the Japan Trench (S-net), aiming to investigate the frequency content characteristics of vertical ground motion components. Using random-effects regression with consideration of key factors like water depth and sediment layer thickness, we developed empirical models for vertical frequency content parameters. Significance tests and the Akaike Information Criterion (AIC) were employed to evaluate parameter validity and model goodness-of-fit. Results show that significant differences exist between horizontal and vertical frequency content distributions, highlighting the significance of the water depth parameter and setting condition. For S-net ocean-bottom stations (water depth: 102~7830 m), vertical frequency parameters shift toward shorter periods at depths less than 1500 m, while longer-period (longer than 0.8 s) records increase significantly at depths greater than 1 500 m. The water depth significantly affects vertical frequency content. Predictions for different tectonic types show consistent differences between vertical and horizontal models. Site terms exhibit significant differences between inner-trench and outer-trench stations, possibly influenced by the propagation paths of seismic waves and the topographical features associated with the outer ridge of the trench rather than sediment layer thickness. This study provides support for understanding offshore ground motion characteristics and assessing offshore seismic hazards.