Search Results (5,647)

The application of tuned mass dampers (TMDs) to high-rise buildings or slender bridges can significantly decrease the dynamical vibrations due to external excitation, such as wind or earthquake loads. However, the individual properties of a TMD such as mass, stiffness and damping have to be designed carefully with respect to the dynamical properties of the investigated structure. In real-world structures, the influence of uncertain system properties might be critical for the performance of a TMD and thus the whole structure. Therefore, the design under uncertainty of such systems is an important issue, which is addressed in the current paper. For our investigations, we consider linear single-degree-of-freedom (SDOF) systems, where analytical formulas for the deterministic design already exist, and linear multi-degree-of-freedom (MDOF) systems, where a time integration and numerical optimization algorithms are usually applied to obtain the optimal TMD parameters. If the numerical optimization should be coupled with a sampling-based uncertainty quantification method, such as Monte Carlo sampling, the design procedure would require the evaluation of a coupled double-loop approach, which is very demanding from the computation point of view. Therefore, we focus the following paper on an efficient analytical uncertainty quantification approach, which estimates the mean and scatter from a Taylor series expansion. Additionally, we introduce an efficient mode decomposition approach for MDOF systems with multiple TMDs, which estimates the maximum displacements using a modal analysis instead of a demanding time integration. Different optimal design problems are formulated as single- or multi-objective optimization tasks, where the statistical properties of the maximum displacements are considered as safety margins in the optimization goal functions. The application of numerical optimization algorithms is straightforward and not limited to specific algorithms. As numerical examples, we investigate an SDOF system with single TMD and a multi-story frame with multiple TMDs. The presented procedure might be interesting for the design process of structures, where the dynamical vibrations reach a critical threshold. Full article

Earthquake prediction remains a significant challenge in seismology, and advancements in signal processing techniques have opened new avenues for improving prediction accuracy. This paper explores the application of Time–Frequency Distributions (TFDs) to seismic signals to identify diagnostic precursory patterns of major earthquakes. TFDs provide a comprehensive analysis of the non-stationary nature of seismic data, allowing for the identification of precursory patterns based on energy concentration features. Current earthquake prediction models primarily focus on long-term forecasts, predicting events by identifying a cycle in historical data, or on nowcasting, providing alerts seconds after a quake has begun. However, both approaches offer limited utility for disaster management, compared to short-term earthquake prediction methods. This paper proposes a new possible precursory pattern of major earthquakes, tested through analysis of recent major earthquakes and their respective prior minor earthquakes for five earthquake-prone countries, namely Türkiye, Indonesia, the Philippines, New Zealand, and Japan. Precursors in the time–frequency domain have been consistently identified in all datasets within several hours or a few days before the major earthquakes occurred, which were not present in the observation and analysis of the earthquake catalogs in the time domain. This research contributes towards the ongoing efforts in earthquake prediction, highlighting the potential of quadratic non-linear TFDs as a significant tool for non-stationary seismic signal analysis. To the best of the authors’ knowledge, no similar approach for consistently identifying earthquake diagnostics precursors has been proposed, and, therefore, we propose a novel approach in reliable earthquake prediction using TFD analysis. Full article

Shallow gas reservoirs exhibit low formation pressure and gas injection levels, leading to low-resistivity contrast between gas-bearing reservoirs and fully water-saturated layers. Gas-bearing formation identification and water saturation estimation face great challenges. To improve the accuracy of shallow gas reservoir identification and logging evaluation, it is essential to analyze the genesis mechanisms underlying the low-resistivity contrast. This study used the HJ Formation, a typical shallow gas reservoir located in the BY Sag of the eastern South China Sea Basin as an example. Combining the results of nuclear magnetic resonance (NMR), full rock mineral analysis and X-ray diffraction of clay minerals in the laboratory, it was determined that the genesis mechanism for the low-resistivity contrast in the gas-bearing reservoir was due to the high irreducible water saturation (S_wi) and the cation-induced supplementary conductivity. Afterwards, we integrated three methods, density–neutron correlation, calculation of the apparent formation water resistivity, and cross-plots of conventional and gas-logging curves, to identify shallow gas reservoirs. In addition, we also established a Waxman–Smits-based model to estimate water saturation. Compared with the typical Archie’s equation, the predicted water saturation curve using the Waxman–Smits-based model was more reasonable. The established methods and models can be used in target shallow gas reservoir evaluations, and it also has reference value for other types of oilfields with similar physical characteristics. Full article

In 1999, the Attica region experienced a severe earthquake that damaged the Holy Monastery of Daphni, a UNESCO Heritage monument. The Ministry of Culture commissioned a detailed geometric documentation project using the state-of-the-art methods available at the time. More than two decades later, in 2023, a new documentation project was conducted using modern technologies and equipment. This paper makes a comparison of the two projects in terms of the equipment and the methodologies used, the personnel needed, and the hours spent documenting the same complicated monument in two different time periods, spanning 20 years. Moreover, it attempts to make a comparison between the different deliverables, focusing on regions that back then appeared damaged or cracked. Key differences include a significant reduction in field and processing time, a dramatic decrease in personnel needs, and a shift from 2D outputs to integrated 3D models. This study highlights how technological advancements have enhanced precision and efficiency in documenting complex heritage sites. Full article

Precise classification of landslide types is critical for targeted hazard mitigation, although the absence of type-specific classifications in many existing inventories limits their utility for effective risk management. This study develops a transferable machine learning approach to identify cliff-type landslides from unclassified records, with a focus on earthquake-prone regions. Using the Forest-based and Boosted Classification and Regression (FBCR) tools in ArcGIS Pro, a model was trained on 167 landslide points and 167 non-landslide points from Tokushima Prefecture, Japan. The model achieved high predictive performance, with 84% accuracy and sensitivity, an F1 score of 84%, and a Matthews correlation coefficient (MCC) of 0.68. The trained model was applied to the Kegalle District, Sri Lanka, and validated against a recently updated inventory specifying landslide types, resulting in an accuracy of 80.1%. It also enabled retrospective identification of cliff-type landslides in older inventories, providing valuable insights for early hazard assessment. Spatial analysis showed strong correspondence between predicted cliff-type zones and key conditioning factors, including specific elevation ranges, steep slopes, high soil thickness, and proximity to roads and buildings. This study integrates FBCR-based modelling with a cross-regional application framework for cliff-type landslide classification, offering a practical, transferable tool for refining inventories, guiding countermeasures, and improving preparedness in regions with similar geomorphological and seismic settings. Full article

Since the onset of gas extraction in Groningen province, the Netherlands, more than 1700 earthquakes have taken place. This has resulted in damage to properties and safety issues for almost 28,000 buildings. As a result, an extensive reinforcement and damage repair operation started, due to which, many residents were temporarily relocated. Although the need for compensation and restoration was recognized from 2012, recent years are characterized by unclear and shifting responsibilities, bureaucratic complexities, and evolving compensation standards, leading to disparity and a further escalation of social impacts. This paper examines developments in the case from 2015 onwards, when the last overview article on this case was published. We observe that even after a decade of compensation efforts, many residents experience loss of trust in the government and endure chronic stress that impacts their well-being, family dynamics, and overall quality of life. We analyze the government-led mitigation and compensation system that in essence fails to address the grievances of local people. Even after broad recognition of the flawed system, the parliament did not fundamentally change it. In nine lessons, we underscore the global imperative for robust social impact assessments, ongoing social monitoring, and well-coordinated compensation frameworks. This is not only crucial to address socio-ecological distress, but also to build more accountable and sustainable institutional responses to future extraction endeavors. Full article

This study presents a high-performance external strengthening strategy for reinforced concrete (RC) beam–column joints, integrating near-surface mounted (NSM) Carbon Fiber Reinforced Polymer (C-FRP) ropes with externally bonded C-FRP sheets. The X-shaped ropes, anchored diagonally on both principal joint faces and complemented by vertical ropes at column corners, provide enhanced core confinement and shear reinforcement. C-FRP sheets applied to the beam’s plastic hinge region further increase flexural strength and delay localized failure. Three full-scale, shear-deficient RC joints were subjected to cyclic lateral loading. The unstrengthened specimen (JB0V) exhibited rapid stiffness deterioration, premature joint shear cracking, and unstable hysteretic behavior. In contrast, the specimen strengthened solely with X-shaped C-FRP ropes (JB0VF2X2c) displayed a markedly slower rate of stiffness degradation, delayed crack development, and improved energy dissipation stability. The fully retrofitted specimen (JB0VF2X2c + C-FRP) demonstrated the most pronounced gains, with peak load capacity increased by 65%, equivalent viscous damping enhanced by 55%, and joint shear deformations reduced by more than 40%. Even at 4% drift, it retained over 90% of its peak strength, while localizing damage away from the joint core—a performance unattainable by the unstrengthened configuration. These results clearly establish that the combined C-FRP rope–sheet system transforms the seismic response of deficient RC joints, offering a lightweight, non-invasive, and rapidly deployable retrofit solution. By simultaneously boosting shear resistance, ductility, and energy dissipation while controlling damage localization, the technique provides a robust pathway to extend service life and significantly enhance post-earthquake functionality in critical structural connections. Full article

The generalized Pareto distribution is frequently used for modeling extreme values above an appropriate threshold level. Since the process of determining the appropriate threshold value is difficult, a mixture of extreme value models rises to prominence. In this study, mixture extreme value models based on exponentiated Pareto distribution are proposed. The Weibull, gamma, and log-normal models are used as bulk densities. The parameter estimates of the proposed models are obtained using the maximum likelihood approach. Two different approaches based on maximization of the log-likelihood and Kolmogorov–Smirnov p-value are used to determine the appropriate threshold value. The effectiveness of these methods is compared using simulation studies. The proposed models are compared with other mixture models through an application study on earthquake data. The GammaEP web application is developed to ensure the reproducibility of the results and the usability of the proposed model. Full article

Volcano-tectonic seismic events (VT) are quite rare at Stromboli, numbering about ten events per year and generally with low magnitude. Using a dataset of 98 events from the 2005–2024 period, we report an improved relocation of VT events here. Relocated earthquakes are mainly distributed on the island and in an area located SSW of Stromboli. These VT events are related to the activation of seismogenic structures by a stress increase related to magma ascent. The shallowest seismicity (4–5 km) is positioned under the Stromboli summit, with a high occurrence in 2006–2007 and in 2019–2024, suggesting a major recharge of the HP magma reservoir. The deepest VT seismicity affects a depth of 7–12 km located in the submerged edifice SSW of the summit and is attributable to the dynamics of the LP magma reservoir, which was more active in 2006–2014 and much less so in the successive years. The increase in the occurrence rate of VT shallow seismicity seems to precede the most significant Stromboli activities, such as the 2007 and 2024 lava effusions followed by paroxysms. For these episodes, VT seismicity would appear to indicate a recharging in the first 4–5 km during the months preceding them, thereby representing a medium–short-term warning signal. Full article

Pumping station structures are widely employed to supply circulating cooling water systems in nuclear power plants (NPPs) throughout China. Investigating their seismic performance under complex heterogeneous site conditions and load scenarios is paramount to meeting nuclear safety design requirements. This study proposes and implements a novel, efficient, and accurate viscous-spring boundary methodology within the ANSYS 19.1 finite element software to assess the seismic safety of NPP pumping station structures. The Maximum Initial Time-step (MIT) method, based on Newmark’s integration scheme, is employed for nonlinear analysis under coupled static–dynamic excitation. To account for radiation damping in the infinite foundation, a Compact Viscous-Spring (CVs) element is developed. This element aggregates stiffness and damping contributions to interface nodes defined at the outer border of the soil domain. Implementation leverages of ANSYS User Programmable Features (UPFs), and a comprehensive static–dynamic coupled analysis toolkit is developed using APDL scripting and the GUI. Validation via two examples confirms the method’s accuracy and computational efficiency. Finally, a case study applies the technique to an NPP pumping station under actual complex Chinese site conditions. The results demonstrate the method’s capability to provide objective seismic response and stability indices, enabling a more reliable assessment of seismic safety during a Safety Shutdown Earthquake (SSE). Full article

The analysis of earthquake source mechanisms is key for seismotectonic studies, but it is often limited to traditional methods plagued with issues of precision and automation. This is particularly true in low-seismicity areas with deep and/or hidden seismogenic sources, where the identification of precise source mechanisms is a difficult and non-trivial task. In this study, we present a detailed application of TESLA (Tool for automatic Earthquake low-frequency Spectral Level estimAtion), a novel tool designed to overcome these limitations. We demonstrated TESLA’s effectiveness in defining source mechanism analysis by applying it to seismic sequences that occurred near Asti (AT), in the Monferrato area (Southern Piedmont, Italy). Our analysis reveals that the observed clusters consist of two distinct seismic sequences, occurring in 1991 and 2012, which were activated by the same seismogenic source. We relocated a total of 36 events with magnitudes ranging from 1.1 to 3.7, using a 3D velocity model, and computed 12 well-constrained focal mechanism solutions using the first motion polarities and the low-frequency spectral level ratios. The results highlight a relatively small seismogenic source located at approximately 5 km north of Asti (AT), at a depth of between 10 and 25 km, trending SW–NE with strike-slip kinematics. A smaller cluster of three events shows an activation of a different fault segment at around 60 km of depth, also showing strike-slip kinematics. These findings are in good agreement with the regional stress field acting in the Monferrato area and support the use of investigation tools such as TESLA for microseismicity analysis. Full article

Earthquake hazards, such as strong ground motion, liquefaction, and landslides, pose significant threats to structures built on seismically vulnerable, loose, and saturated sandy soils. Therefore, a structural failure evaluation method that accounts for site-specific seismic responses is essential for developing effective and appropriate earthquake hazard mitigation strategies. In this study, a real-time assessment framework for structural seismic susceptibility is developed. To evaluate structural susceptibility to earthquakes, seismic fragility functions are employed as thresholds for structural failure and are linked to a geotechnical spatial grid that incorporates correlation equations for seismic load determination. The real-time assessment consists of the following procedures. First, the geotechnical spatial grid is constructed based on the geostatistical method to estimate the site-specific site response to be correlated with the earthquake hazard potential. Second, the peak ground accelerations are determined from seismic load correlation and assigned to the geotechnical spatial grid. Third, the damage grade of structure is determined by calculating the failure probabilities of defined damage levels and integrating the geotechnical spatial grids for the target structure in real time. The proposed assessment was simulated at Incheon Port, South Korea, using both an actual earthquake event (the 2017 Pohang Earthquake) and a hypothetical earthquake scenario. Full article

The storage conditions of multi-floor grain warehouses change frequently during grain circulation. This paper investigates the effects of various storage conditions on the seismic performance of multi-floor grain warehouses. The numerical results indicate that the higher the storage material distribution position, the greater the damping ratio of the structural model and the more obvious the contribution of storage material movement to the damping of the structure. The intensity of earthquake action and the spatial height of the floor where the storage material is located are negatively correlated with the acceleration response of the structure. Under full-silo conditions, when the peak ground acceleration (PGA) is 0.4 g, the acceleration amplification factor at the top of the structure is 69.7% of the corresponding parameter at 0.1 g. The discontinuity in the storage space of the structure results in a torsional effect on the structure. When PGA = 0.22 g, the peak inter-story displacement angle of the first floor differs by nearly 1.7 times under different operating conditions, and the peak inter-story displacement angle of the second floor during an earthquake with PGA = 0.40 g differs by about 1.5 times under different operating conditions. The lateral pressure of the silo wall at different burial depths under earthquake action shows a highly nonlinear distribution trend, and the overpressure coefficient at the same burial depth of the warehouse wall is proportional to the PGA of the earthquake action. During 0.1 g, 0.22 g, and 0.40 g earthquakes, the maximum overpressure coefficients at the bottom of the warehouse wall on different floors are 1.13, 1.21, and 1.66, respectively. Full article

Seismic waves induce pore pressure changes in aquifers, leading to water level oscillations in wells. These oscillations are often used to estimate the poroelastic properties of aquifers, but their interpretation is influenced by factors such as aquifer properties, seismic wave characteristics, and wellbore storage. The aim of this study is to evaluate the effect of wellbore storage on seismically induced water level oscillations. We analyze water level responses to similar seismic forcing in two adjacent deep wells (~1000 m) tapping the same confined aquifer: one open (artesian) and one closed (flowing artesian). Seismic forcing was characterized using ground motion velocity data from a nearby seismic station. The results show that the wells differ by three orders of magnitude in their wellbore storage. In the open well, pore pressure oscillations are reliably detected only for teleseismic events, while in the closed well, they are also reliably recorded for regional earthquakes. Under these conditions, it is possible to estimate the first-order approximation of the aquifer’s poroelastic coefficients. These findings emphasize the importance of accounting for wellbore storage when interpreting seismically induced water level fluctuations. Full article

Staggered floor frame structures with good spatial adaptability are widely used in large-space civil buildings such as conference halls and terminal buildings. However, the short columns formed by staggered floor slabs significantly affect load transfer, which is unfavorable to the seismic performance of the structure. To address this issue, based on a practical project, this paper establishes a finite element analysis model, sets up steel-tube-reinforced concrete (ST-RC) columns at staggered floors to improve the insufficient ductility of short columns, and adopts the dynamic time–history analysis method combined with performance-based evaluation methods to study the effects of different seismic input angles (0°, 30°, 60°, 90°) on the seismic performance of local staggered floor frame structures at both the overall and member levels. The research results show that at the overall level, the fourth floor of the staggered floor frame structure is the weak floor, and the most unfavorable seismic input angle is 60°; additionally, at the member level, the damage of each member meets the performance objectives. Frame beams are more severely damaged under 0° and 90° seismic input, frame columns are more severely damaged under 30° and 60° seismic input, and the damage degree of ST-RC columns is similar in the four directions. As energy-dissipating members, frame beams have a significantly higher proportion of nonlinear strain energy than frame columns and ST-RC columns, which can effectively consume a large amount of seismic energy and enable the structure to retain more safety reserves. Therefore, for irregular buildings such as staggered floor frame structures that are prone to damage due to insufficient ductility of short columns, setting ST-RC columns at staggered floors can effectively reduce structural damage. The adoption of evaluation methods at both the overall structural and member levels enables a comprehensive understanding of the damage status of staggered floor structures. Full article