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Timber-framed masonry structures are widely used around the world, and their seismic performance is generally poor. Most of them have not been seismically strengthened. In areas with high seismic fortification intensity, there are great potential safety hazards. And it is urgent to carry out effective seismic reinforcement. However, due to the complicated construction process of the existing reinforcement technology, the poor durability of the reinforcement materials, and the significant disturbance to the life of the original residents, an efficient single-story timber-framed masonry structure reinforcement technology suitable for comprehensive promotion and application has not been explored. In this paper, a fiber-reinforced cement mortar (FRCM) material was proposed. A 1/2 scale model of a single-story timber-framed masonry structure was taken as the research object. The method of strengthening a single-story timber-framed masonry structure with FRCM layer was adopted. And the shaking table test of the model before and after reinforcement was carried out in turn. The dynamic characteristics, failure modes, acceleration response and displacement response of the FRCM layer-strengthened structure were analyzed through comparisons of the two cases. The experimental results showed that the FRCM layer significantly improved the seismic performance of the seismic-damaged single-story timber-framed masonry structures. The X- and Y-direction natural frequencies of the model structure were increased by 31.30% and 30.22%, respectively, after the structure was strengthened with FRCM. During a rare eight-degree earthquake, the inter-story displacement angles in the X- and Y-direction of the unreinforced model reached 1/98 and 1/577, respectively, and the structure was destroyed, while the inter-story displacement angle of the FRCM-reinforced model was only 1/2 of that the unreinforced model. During a rare nine-degree earthquake, the X-direction inter-story displacement angle of the model strengthened with FRCM reached 1/78 and the Y-direction inter-story displacement angle reached 1/178. At this time, the reinforced model structure was destroyed, but there was no collapse of the structural components, which met the seismic design objectives of "operational under the design minor seismic intensity, repairable damage under the design seismic precautionary intensity, and collapse prevention under the design rare seismic intensity", which proved that the FRCM layer was an effective and feasible way to strengthen the existing single-story wood-masonry rural building. [ABSTRACT FROM AUTHOR]

Compelling evidence has shown that geomagnetic disturbances in vertical intensity polarization before great earthquakes are promising precursors across diverse rupture conditions. However, the geomagnetic vertical intensity polarization method uses the spectrum of smooth signals, and the anomalous waveforms of seismic electromagnetic radiation, which are basically nonstationary, have not been adequately considered. By combining pulse amplitude analysis and an experimental study of the cumulative frequency of anomalies, we found that the pulse amplitudes before the 2022 Luding M6.8 earthquake show characteristics of multiple synchronous anomalies, with the highest (or higher) values occurring during the analyzed period. Similar synchronous anomalies were observed before the 2021 Yangbi M6.4 earthquake, the 2022 Lushan M6.1 earthquake and the 2022 Malcolm M6.0 earthquake, and these anomalies indicate migration from the periphery toward the epicenters over time. The synchronous changes are in line with the recognition of previous geomagnetic anomalies with characteristics of high values before an earthquake and gradual recovery after the earthquake. Our study suggests that the pulse amplitude is effective for extracting anomalies in geomagnetic vertical intensity polarization, especially in the presence of nonstationary signals when utilizing observations from multiple station arrays. Our findings highlight the importance of incorporating pulse amplitude analysis into earthquake prediction research on geomagnetic disturbances. [ABSTRACT FROM AUTHOR]

Seismic intensity measures (IMs) can directly affect the seismic risk assessment and the response characteristics of underground structures, especially when considering the key variable of burial depth. This means that the optimal seismic IMs must be selected to match the underground structure under different buried depth conditions. In the field of seismic engineering design, peak ground acceleration (PGA) is widely recognized as the optimal IM, especially in the seismic design code for aboveground structures. However, for the seismic evaluation of underground structures, the applicability and effectiveness still face certain doubts and discussions. In addition, the adverse effects of earthquakes on tunnels in soft soil are particularly prominent. This study aims to determine the optimal IMs applicable to different burial depths for horseshoe-shaped tunnels in soft soil using a nonlinear dynamic time history analysis method, and based on this, establish the seismic fragility curves that can accurately predict the probability of tunnel damage. The nonlinear finite element analysis model for the soil–tunnel interaction system was established. The effects of different burial depths on damage to horseshoe-shaped tunnels in soft soil were systematically studied. By adopting the incremental dynamic analysis (IDA) method and assessing the correlation, efficiency, practicality, and proficiency of the potential IMs, the optimal IMs were determined. The analysis indicates that PGA emerges as the optimal IM for shallow tunnels, whereas peak ground velocity (PGV) stands as the optimal IM for medium-depth tunnels. Furthermore, for deep tunnels, velocity spectral intensity (VSI) emerges as the optimal IM. Finally, the seismic fragility curves for horseshoe-shaped tunnels in soft soil were built. The proposed fragility curves can provide a quantitative tool for evaluating seismic disaster risk, and are of great significance for improving the overall seismic resistance and disaster resilience of society. [ABSTRACT FROM AUTHOR]

Beam bridges, as the primary structural form of medium and small-sized bridges, are extensively utilized for road and railway crossings over rivers and valleys. Ensuring their reliability during earthquakes is crucial not only for maintaining traffic flow but also for mitigating the seismic impact on the economy and society. Considering earthquake intensity and uncertain parameters, this paper proposes an innovative method for assessing the seismic reliability of simply-supported beam bridges under three different levels of seismic design: minor, moderate, and major earthquakes. The proposed method first estimates the probability of encountering three typical earthquake intensities during the design life of simply-supported beam bridges based on crowd intensity, benchmark intensity, and major earthquake intensity. It then introduces uncertain parameters and employs the point estimation method to calculate the probability of bridge passage under specific earthquake intensities. Finally, it combines these earthquake intensities to calculate the overall seismic reliability of simply-supported beam bridges. The effectiveness and efficiency of this method are demonstrated through calculations for a three-span, double-degree-of-freedom simply-supported beam bridge, and validated using Monte Carlo simulations. This research provides solid theoretical support for seismic assessment, design, and intensity-based reliability analysis of simply-supported beam bridges. [ABSTRACT FROM AUTHOR]

An earthquake early-warning system (EEWS) is an indispensable tool for mitigating loss of life caused by earthquakes. The ability to rapidly assess the severity of an earthquake is crucial for effectively managing earthquake disasters and implementing successful risk-reduction strategies. In this regard, the utilization of an Internet of Things (IoT) network enables the real-time transmission of on-site intensity measurements. This paper introduces a novel approach based on machine-learning (ML) techniques to accurately and promptly determine earthquake intensity by analyzing the seismic activity 2 s after the onset of the p-wave. The proposed model, referred to as 2S1C1S, leverages data from a single station and a single component to evaluate earthquake intensity. The dataset employed in this study, named "INSTANCE," comprises data from the Italian National Seismic Network (INSN) via hundreds of stations. The model has been trained on a substantial dataset of 50,000 instances, which corresponds to 150,000 seismic windows of 2 s each, encompassing 3C. By effectively capturing key features from the waveform traces, the proposed model provides a reliable estimation of earthquake intensity, achieving an impressive accuracy rate of 99.05% in forecasting based on any single component from the 3C. The 2S1C1S model can be seamlessly integrated into a centralized IoT system, enabling the swift transmission of alerts to the relevant authorities for prompt response and action. Additionally, a comprehensive comparison is conducted between the results obtained from the 2S1C1S method and those derived from the conventional manual solution method, which is considered the benchmark. The experimental results demonstrate that the proposed 2S1C1S model, employing extreme gradient boosting (XGB), surpasses several ML benchmarks in accurately determining earthquake intensity, thus highlighting the effectiveness of this methodology for earthquake early-warning systems (EEWSs). [ABSTRACT FROM AUTHOR]

Structural engineers often use deep columns in high seismic areas to reduce drifts, yet this somehow contradicts what is stated in some tests in the sense that even though deep columns may satisfy current seismic provisions, they can suffer premature twisting; this is an indication that a lot of research is needed in this area. Numerical and experimental studies have been conducted to estimate the response of steel buildings with medium and deep columns under the action of static and cyclic loading; however, studies accounting for the dynamic characteristics of buildings and strong motions are not common. In addition, responses in terms of local parameters have not been considered either. In this study, the nonlinear seismic responses of steel buildings with perimeter moment-resisting frames and medium (W14) columns are numerically calculated and compared to those of similar steel buildings with equivalent deep columns in terms of cost (W27 and larger). Low-, mid-, and high-rise steel building models with different dynamic characteristics, as well as several strong motions with different frequency contents, are considered. Results indicate that the drifts of the models with medium columns may be up to 140% greater than those of the models with deep columns. Significant reductions are also observed for top displacements, normalized interstory shears, and combined normalized axial loads and bending moments. Hence, the seismic demands of the buildings with deep columns may be much smaller than those of the buildings with medium columns and, therefore, the buildings with deep columns exhibit a superior behavior, which results in more economical designs. The reduction is greater for the case of low- and mid-rise buildings than for high-rise buildings. One of the reasons for this is that as medium columns are replaced by deep columns, the stiffness and the strength increase, which are lower in the tallest model. [ABSTRACT FROM AUTHOR]

As an important part of the boundary conditions on both sides of the high-speed railway track–bridge system, the seismic response of the subgrade structure is different from that of the bridge structure. This difference has become increasingly significant with the widespread adoption of continuous welded rail technology in bridge construction. Therefore, investigating the seismic response of the bridge system, with a specific focus on the longitudinal constraint effects of the subsequent subgrade track structure, is of paramount importance. Utilizing finite element software, two distinct bridge models are developed: one incorporating the subsequent subgrade track structure and another excluding it. Through nonlinear time history analysis under varying seismic intensities, it is demonstrated that the longitudinal constraint of the subsequent subgrade track structure mitigates the longitudinal displacements and internal forces in critical components of the high-speed railway track–bridge system. Concurrently, acknowledging the heightened complexity and cost associated with post-earthquake repairs of the bridge structure compared to subgrade structure, this study uses a risk transfer connecting beam device. This device can redirect seismic damage from bridge structure to subgrade structure, thereby potentially reducing post-seismic repair expenses for the bridge. [ABSTRACT FROM AUTHOR]

Generally speaking, the traditional lever amplification damping system is installed between adjacent columns in a building, which occupies a significant amount of space in the building. In contrast to amplification devices in different forms, the damper displacement of the intermediate column damper system is smaller, and the vibration reduction efficiency is lower. In light of these drawbacks, this study proposes a new amplification device for energy dissipation and vibration reduction, which is based on an intermediate column–lever mechanism with a viscous damper (CLVD). Initially, a specific simplified mechanical model of CLVD is derived. Subsequently, an equivalent Kelvin mechanical model of CLVD is derived to intuitively reflect CLVD's damping and stiffness effect. The damping ratio added by CLVDs to the structure is calculated according to that model; the additional damping ratio and additional stiffness are utilized to calculate the displacement ratio Rd and shear force ratio Rv of the structure with CLVDs to the structure without CLVDs. Rd and Rv are introduced to evaluate the vibration reduction effect of the structure with CLVDs, and the effects of various parameters (such as intermediate column position, beam's bending line stiffness, lever amplification factor, damping coefficient, and earthquake intensity) on Rd and Rv are analyzed. The results indicate that when the ratio of the distance from the intermediate column to the edge column to the span of the beam is 0.5, CLVD owns the optimal vibration reduction effect. Increasing the beam's bending line stiffness is beneficial for CLVD to control structural displacement and shear force; when the leverage amplification factor is too large, the CLVD provides the structure with stiffness as the main factor, followed by damping. Additionally, when the ratio of the displacement amplification factor to the geometric amplification factor satisfies fd/γ = 1/21−0.5α, the CLVD has the optimal displacement control effect on the structure. After that, measures are provided to optimize the CLVD in different situations in order to effectively control the inter-story displacement and the story shear force of the structure. Consequently, a nine-story frame is taken as an example to elaborate the application of CLVDs in the design for energy dissipation and vibration reduction. The results reveal that the CLVD scheme adopting the proposed optimization method can effectively enhance the displacement amplification ability of CLVDs, resulting in an additional damping ratio of up to 12%. At the same time, the inter-story displacement was reduced by almost 40% under fortification earthquakes. Through the research in this study, designers can obtain a new choice in structural vibration reduction design. [ABSTRACT FROM AUTHOR]

Rocking walls can control the overall deformation pattern and the distribution of plastic energy dissipation in structures, suppressing the occurrence of weak layers. In the case of step-terrace frame structures, issues such as severe lateral stiffness irregularities, abrupt changes in floor-bearing capacity, and concentrated deformation in upper ground layers exist. To improve the yielding and failure modes of step-terrace frame structures in mountainous regions, this paper proposes a structural system combining step-terrace frame structures with energy dissipation rocking walls attached to their bottoms, aiming to control the yielding mechanism of the structure, further reduce the seismic response, limit residual deformation, and propose a structural system of step-terrace frame structures with buckling-restrained braces (BRBs) and energy dissipation rocking walls. Two sets of numerical models for step-terrace frame structures with different numbers of dropped layers and spans were established. Through simulating low-cycle repeated loading tests on step-terrace frame structures, the rationality of the models and parameters was verified. Incremental dynamic analysis (IDA) was employed to systematically investigate the vulnerability of step-terrace frame structures with energy dissipation rocking walls under different dropped layer and span configurations. This investigation covered aspects such as IDA curve clusters, percentile curves, seismic demand models, fragility functions, failure state probabilities, vulnerability indices, collapse resistance factors, and safety margins. The results indicated that the change in dropped layer numbers had a far greater impact on the vulnerability of step-terrace frame structures with energy dissipation rocking walls than the change in dropped span numbers. Under seismic excitations with the same peak ground acceleration (PGA), rocking walls can limit the depth of structural plasticity development, reduce the dispersion of peak responses, and lower the probability of exceeding various performance levels, thereby exhibiting good collapse resistance. The addition of buckling-restrained braces (BRBs) can further enhance the seismic performance and collapse resistance of the rocking wall frame structure. By analyzing the correlation between seismic intensity measures and peak structural responses, the validity of using peak ground acceleration as a scaling indicator for incremental dynamic analysis (IDA) has been verified. [ABSTRACT FROM AUTHOR]

Earthquake-triggered landslides (ETLs) feature large quantities, extensive distributions, and enormous losses to human lives and critical infrastructures. Near-real spatial prediction of ETLs can rapidly predict the locations of coseismic landslides just after a violent earthquake and is a vital technical support for emergency response. However, near-real prediction of ETLs has always been a great challenge with relatively low accuracy. This work proposes an ensemble prediction model of EnPr by integrating machine learning tree models and a deep learning convolutional neural network. EnPr exhibits relatively strong prediction and generalization performance and achieves relatively accurate prediction of ETLs. Six great seismic events occurring from 2008 to 2022 on the southeastern margin of the Tibetan Plateau are selected to conduct ETL prediction. In a chronological order, the 2008 Ms 8.0 Wenchuan, 2010 Ms 7.1 Yushu, 2013 Ms 7.0 Lushan, and 2014 Ms 6.5 Ludian earthquakes are employed for model training and learning. The 2017 Ms 7.0 Jiuzhaigou and 2022 Ms 6.1 Lushan earthquakes are adopted for ETL prediction. The prediction accuracy merits of ACC and AUC attain 91.28% and 0.85, respectively, for the Jiuzhaigou earthquake. The values of ACC and AUC achieve 93.78% and 0.88, respectively, for the Lushan earthquake. The proposed EnPr algorithm outperforms the algorithms of XGBoost, random forest (RF), extremely randomized trees (ET), convolutional neural network (CNN), and Transformer. Moreover, this work reveals that seismic intensity, high and steep relief, pre-seismic fault tectonics, and pre-earthquake road construction have played significant roles in coseismic landslide occurrence and distribution. The EnPr model uses globally accessible open datasets and can therefore be used worldwide for new large seismic events in the future. [ABSTRACT FROM AUTHOR]

Currently, the study of analytical solutions for the seismic stability of slopes under anchorage conditions is one of the hottest subjects in engineering. In this paper, an analytical solution for the seismic safety of the three-dimensional (3D) two-stage rock slope reinforced with prestressed anchor cables governed by the nonlinear Hoek–Brown criterion was deduced, in which the analyses of seismicity were performed by the latest modified pseudo-dynamic method. This method supplements the consideration of the damping effect of the rock medium on seismic waves, which is more in line with the real seismic situation. A mathematical geometric model was developed for calculating the external forces work and internal energy dissipation acting on 3D rotating rock masses reinforced with prestressed anchor cables, in which the seismic work rate was calculated using a new layer-by-layer superposition summation method. The analytical solution of the safety factor could be collated as an explicit function of several variables, and then, the optimal value was obtained by the Particle Swarm Optimization (PSO) algorithm. To corroborate the accuracy of new analytical solutions, the results were contrasted with those of the pertinent literature. The results of the two comparisons were very close. Ultimately, the sensitivity analyses and coupling effects of seismic pseudo-dynamic factors and prestressing anchorage factors were carried out. It was found that even small seismic intensities had a large effect on the stability of rock slopes with developed joints. Increasing the number of steps and prestressing anchors can effectively improve the stability of rock slopes under seismic effects. The conclusions have significant implications for the anchorage design of the 3D two-stage rock slope as seismic events occur. [ABSTRACT FROM AUTHOR]

Cross-sea cable-stayed bridges encounter challenges associated with cable corrosion and cable-force relaxation during their service life, which significantly affects their structural performance and seismic response. This study focuses on a cross-sea cable-stayed bridge located in Hainan Province. Utilizing an LSTM deep learning model, this study aims to fill in the gaps in short-term cable-monitoring data from the past year using the available cable-force-monitoring data from the same period. The authors of this study interpolated the cable-force data in the absence of sensors and employed a SARIMA machine learning time-series-prediction model to predict the future trends of all cable forces. A finite-element model was constructed, and a dynamic time-history analysis of the seismic response of the cross-sea cable-stayed bridge was conducted, considering the influence of cable-force relaxation and cable corrosion in the future. The findings indicate that the LSTM-SARIMA model predicted an average decrease of 11.81% in the cable force of the cable-stayed bridge after 20 years. During the lifecycle of the cables, cable corrosion exerts a significant impact on the variation in cable stress within the bridge structure during earthquakes, while cable-force relaxation has a more pronounced effect on the vertical displacement of the main beam of the bridge structure during seismic events. Compared to when using the traditional model that only considers cable corrosion, the maximum negative vertical displacement of the main beam increases by 29.7% when using the proposed model if the earthquake intensity is 0.35 g after 20 years, which indicates that the proposed machine learning model can exactly determine the seismic behavior of the lifecycle cross-sea cable-stayed bridge, considering the impacts of both cable-force relaxation and cable corrosion. [ABSTRACT FROM AUTHOR]

A devastating earthquake took place on 8 April 1893, close to the town of Svilajnac, central Serbia. Over the past decade, significant historical data on the effects of this earthquake has been collected from a variety of sources, including books, scientific publications, reports, newspapers, and coeval chronicles. Additionally, this earthquake was recorded 750 km from the epicenter at the seismological station Rocca di Papa in Rome, Italy. Based on critical review and analysis of the historical data, we demonstrate that the epicentral area of this earthquake was 531 km2, and the macroseismic effects were recorded at epicentral distances up to 600 km towards the west (Vienna, Austria) towards the north, up to 500 km (Košice–Michalovce, Slovakia), towards the east up to 460 km (Brašov–Borsec, Romania); and towards the south up to about 300 km (Radoviš, North Macedonia). Finally, we show that the key parameters of the 1893 Svilajnac earthquake are as follows: (1) epicentral intensity, I0 = IX EMS-98, (2) the estimations of the moment magnitude and focal depth based on the observed intensities, MW = 6.8 and h = 13 km, respectively, and (3) the epicenter coordinates, 44.160° N and 21.354° E. [ABSTRACT FROM AUTHOR]

This study presents an updated view of the effects of the 1940 Vrancea earthquake. Recently compiled studies in the literature from the time of the event, as well as other studies, present the opportunity to gain additional and relevant information regarding this large-magnitude event. The effects of this earthquake on various locations in Romania are compared to those observed after the subsequent large Vrancea earthquake of 1977. An assessment of the economic losses caused by the seismic event is also attempted. The seismic vulnerability of some building typologies commonly used before 1940 is assessed by employing the earthquake damage data and the well-known macroseismic method. The impact of this event on the design and construction practices in Romania is evaluated using the collected information as well. Finally, the policy of repair and strengthening of buildings applied after the event is also discussed, and case studies are presented. [ABSTRACT FROM AUTHOR]

This paper investigates a method for improving the selection of seismic motions for designing earthquake-resistant underground structures. It is found that PGV alone is unreliable as a predictor of structural damage with increasing earthquake intensity. Therefore, based on characterizing seismic intensity by using PGV, another parameter, referred to here as "the severest parameter", is introduced to distinguish potential damage capacity for different seismic motions. A numerical model of a soil–underground structure system was established using the finite element software OpenSees. A total of 120 real ground motions were selected for the model, considering the influences of eight different site groups on the underground station and the rupture distances of the input seismic motions. The results show that as seismic intensity increases, substantial variability in the response of underground structures emerges under the same amplitude of PGV, diminishing the effectiveness of the relationship between PGV and structural damage. When assessing the potential damage capacity of seismic motions with similar or close amplitudes of PGV, VSI is an appropriate severest parameter for Class III sites and ASI is suitable for Class II sites. When the correlation coefficient between the severest parameter and the structural response is greater than 0.8, it can be used to reliably assess seismic damage capacity based on the size of the severest parameter. [ABSTRACT FROM AUTHOR]

Earthquakes impact the stability of municipal solid waste (MSW) landfills, especially those with high water levels, and may further lead to disastrous landslides. Numerical analysis offers an efficient and cost-effective way to study the seismic stability of a landfill. In this study, the finite difference nonlinear analysis method was employed to meticulously evaluate the dynamic response of landfills under varying water levels and seismic intensities. The analysis was guided by the seismic instability and centrifuge test outcomes. The rationality of the computational model was verified by examining the responses of acceleration and pore pressure. Subsequently, the time history curve of the dynamic safety factor was derived from the dynamic response of landfills. The results indicated that a landfill was more susceptible to large earthquake effects, and its stability decreased as the water level rose, with the safety factor decreasing to a critical point under the coupling effect of strong earthquakes and high water levels. In contrast, the stability of the landfill with low water levels was good under weak earthquake conditions, with only a slight decrease in the safety factor observed. The seismic stability of a landfill was significantly influenced by both accumulative deformation and negative excess pore pressure. A certain degree of hysteresis in the landfill's instability was also observed compared to the earthquake loading process. The time history curve of the safety factor can offer a comprehensive insight into seismic stability under diverse conditions. Additionally, future research efforts are needed to better determine the values of strength parameters of MSW in seismic analysis. [ABSTRACT FROM AUTHOR]

On 15 January 2023, a shallow, moderate earthquake with a magnitude (Mw) of 4.7 and a depth of one kilometer struck the northern part of Leyte Island in the central Philippines. Originating along the northern Leyte segment of the Philippine Fault, a well-established creeping fault, the earthquake caused significant geologic, structural, and socio-economic impacts despite its low magnitude. Probable surface rupture and landslides were reported, leading to a comprehensive field investigation. Our investigation revealed an ~8 km discontinuous surface rupture along the northern Leyte segment of the Philippine Fault, with a maximum left-lateral displacement of 2 cm. This was the first documented occurrence of such a phenomenon associated with an earthquake of a magnitude less than 6, particularly along a creeping fault segment. The maximum ground shaking felt was reported on the PHIVOLCS Earthquake Intensity Scale (PEIS) to be VI (very strong), equivalent to a Modified Mercalli Intensity (MMI) of VI along the fault strike. However, strong motion accelerographs recorded a peak ground acceleration (PGA) of 0.407 g, equivalent to PEIS VIII (very destructive), attributed to local site amplification influenced by subsurface geology. In the area where the local site amplification occurred, limited liquefaction was observed on marshlands with recent and alluvial deposits. Two landslides were observed in the mountainous area west of the fault. Structural damages were noted in areas with PEIS VI intensity and areas transected by the surface rupture. Despite the earthquake's low magnitude, the event documented significant impacts, including surface ruptures, liquefaction, landslides, and severe structural damage. The peculiarities of this event are attributed to the shallowness of the earthquake source, and local site conditions, including geology, geomorphology, and soil properties, contributed to the severity of the impacts. Moderate in size, this earthquake emphasizes the importance of documenting moderate-sized earthquakes as a tool and guide for medium- and long-term earthquake risk assessment and resiliency. [ABSTRACT FROM AUTHOR]

This study develops empirical fragility curves for concrete and masonry buildings in Haiti, utilizing data from the 2021 earthquake. A dataset of 3527 buildings from the StEER database, encompassing a diverse range of building types, is used. These buildings types include reinforced concrete structures with masonry infills, confined masonry buildings, reinforced masonry bearing walls, and unreinforced masonry bearing walls. Shakemaps from the USGS are utilized to assess the earthquake's intensity at each building, with the peak ground acceleration (PGA) as the intensity measure. Damage is classified into five distinct states: no damage, minor, moderate, severe, and partial or total collapse. For each of these states, the corresponding probabilities of exceedance are calculated, and log-normal cumulative distribution functions were fitted to those data to produce empirical fragility curves. The results show a notable similarity in performance among the four types, each having high probability of failure even under low-intensity earthquakes. Total fragility curves (including all four building types) are developed subsequently and they are convolved to the probabilistic seismic hazard map of Haiti to assess the seismic risk. This includes estimating the annual probability of partial/total collapse and the probability of partial/total collapse in the event of 475-year and 2475-year earthquakes. The results indicate a significant risk, with up to 64% probability of collapse in certain areas for the 2475-year earthquake and a probability of collapse of 15% for a 475-year earthquake. These findings underscore the critical vulnerability of Haiti's buildings to seismic events and the urgent need for their retrofit. [ABSTRACT FROM AUTHOR]

As an innovative building system, the modular steel structure demonstrates a high degree of industrialization and assembly efficiency. However, no linkage exists between the components of modular units, leading to issues such as diminished load capacity and excessive steel usage in modular construction. In order to tackle these challenges, finite element numerical simulations are employed to examine the inter-column connectors and the cooperative modular steel buildings. This simulation calculates the initial stiffness across various degrees of freedom in these connectors. In addition, it analyzes the displacement response, changes in internal forces, and height of cooperative modular steel structures under varying seismic precautionary intensities. The results revealed that cooperative modular steel buildings substantially improve overall stiffness and lateral performance compared to their non-cooperative counterparts. There is a maximum reduction in the inter-story displacement angle of up to 36.1%, and the maximum reduction of the top displacement can reach 16.2%. This enhancement also increases structural stiffness, a shortened natural vibration period, and an augmented bottom shear force. Based on these findings, it is advised that the height of cooperative modular steel buildings should not exceed 21 m at 7 degrees (0.10 g), 21 m at 7 degrees (0.15 g), and 12 m at 8 degrees (0.20 g). [ABSTRACT FROM AUTHOR]

A cantilever block wall-panel attachment strip (CBW) flexible connection node was designed to connect precast concrete (PC) exterior wall panels to steel frames. To investigate the performance of the CBW flexible connection node and PC exterior wall panels during earthquakes, a partial two-storey steel frame was extracted from an actual engineering structure, and a full-scale steel frame–exterior wall panel shaking-table model was designed. Two sets of shaking-table tests were conducted under seismic intensity 7, 8, and 9 (Chinese Seismic Intensity Scale) earthquakes. The acceleration and displacement responses of the composite wall panel, open window panel, and integral wall panel along the in-plane and out-of-plane motions were analysed. The acceleration amplification factors of the PC exterior wall panels ranged from 0.753 to 1.400 (in-plane) and from 0.998 to 2.199 (out-of-plane). The CBW flexible connection node had a deformation capacity that could coordinate the deformation of the exterior wall panel and prevent severe damage. The surfaces of the PC exterior wall panels remained intact during a very strong seismic intensity 9 earthquake. [ABSTRACT FROM AUTHOR]

Intake towers, essential for hydraulic hub projects, are integral to maintaining safety and efficiency, especially under seismic conditions that are prevalent near fault zones. These structures are vital for the integrity of hydraulic hubs, effective hydropower generation, and downstream safety. The duration of seismic events notably influences the towers' structural response. In light of China's initiative to build numerous high dams and large reservoirs, understanding the interplay between seismic duration and the intake tower response is crucial. This study, utilizing a duration-dependent composite parameter method based on seismic intensity, investigates the impact of near-fault ground motion duration effects on the response characteristics of intake towers. It analyzes the correlation between three types of six duration parameters and six duration-related composite parameters with the nonlinear seismic response of the physical model of the intake tower structure, as well as the rapid seismic response of the simplified model. This study investigates the impact of near-fault ground motion duration on intake towers, which is crucial for hydraulic hub projects, particularly in seismic-prone areas like those targeted by China's dam construction initiative. Utilizing a duration-dependent composite parameter method, the study establishes a strong correlation between seismic duration parameters and the nonlinear response of intake towers, emphasizing the significance of uniform duration-related composite intensity parameters for characterizing near-fault seismic motion features. The findings reveal a pronounced correlation between the elasto-plastic response of intake towers and consistent duration-related composite strength parameters, offering crucial insights for optimizing structural design and enhancing seismic response assessment, particularly in the realm of large-scale dam projects. [ABSTRACT FROM AUTHOR]

To estimate earthquake losses for regional buildings, it is important to consider the varying seismic performances of different types of buildings. To achieve this, a dynamic elastic–plastic analysis based on detailed structural modeling is more accurate than the capacity spectrum method based on a single degree of freedom to obtain the response and damage of various structures under seismic activity and provide a more precise estimate of earthquake losses for buildings. Detailed information about the building facilities is necessary to create a fine structural model. However, obtaining precise actual structural details can be challenging with existing methods, especially when there are a large number of buildings to consider. This paper proposes a new method called story-based random structure (SBRS) modeling to address this issue, which is based on the common and reasonable layout of the structure. The process involves choosing design parameters that can represent the structural arrangement of a building as variables. These parameters include the materials' type and strength, proportions, the components' size, and other relevant factors. The values for these variables are determined based on engineering experience and design specifications. The range of values for these variables is also determined to ensure that all design requirements are met. Finally, the Latin Hypercubic Sampling (LHS) method is used to randomly sample and combine the variables, establishing a detailed structural model of the building with structural uncertainty. According to the results of the analysis, this method can simulate the structure and component information of a building by using a probabilistic approach, even without knowing the specific structural design. This method can be based on a small amount of readily available building information and solves the problem of the rapid and refined modeling of a large number of buildings at the regional scale. It also makes it possible to estimate the earthquake loss of regional buildings based on their seismic capacity. [ABSTRACT FROM AUTHOR]

Ground-motion intensity measures (IMs), which quantify and describe the characteristics of earthquake ground motion, are of utmost importance in the assessment of seismic risk and the design of resilient structures with large spans. The appropriate selection of a ground-motion IM is crucial in establishing a reliable and robust correlation between seismic hazards and structural demands. The current study presents a novel ground-motion IM that incorporates the influence of multiple vibration modes and period elongation resulting from isolation based on the velocity spectrum. A comprehensive study has been conducted to examine the efficiency of 37 different ground-motion IMs on a roof-isolated large-span structure with engineering demand parameters (EDPs), using far-field ground-motion data. The initial examination of the proposed intensity measure involves a planar lumped-mass model. Subsequently, a numerical model of a large-span roof-isolated structure, specifically the Beijing Workers' Stadium, is constructed and examined. The results suggest that the proposed intensity measure (IM) demonstrates satisfactory adequacy and achieves optimal efficiency when considering three different engineering demand parameters among 37 other ground-motion intensity measures. [ABSTRACT FROM AUTHOR]

The utilization of the Monte Carlo method in conjunction with probabilistic seismic hazard analysis (PSHA) constitutes a compelling avenue for exploration. This approach presents itself as an efficient and adaptable alternative to conventional PSHA, particularly when confronted with intricate factors such as parameter uncertainties and diverse earthquake source models. Leveraging the Monte Carlo method and drawing from the widely adopted Cornell-type seismicity model in engineering seismology and disaster mitigation, as well as a seismicity model capturing temporal, spatial, and magnitude inhomogeneity, we have derived a formula for the probability of earthquake intensity occurrence and the mean rate of intensity occurrence over a specified time period. This effort has culminated in the development of a MATLAB-based program named MCPSHA. To assess the model's efficacy, we selected Baoji City, Shaanxi Province, China, as our research site. Our investigation delves into the disparity between occurrence probability and extreme probability (a surrogate commonly employed for occurrence probability) in the Baoji region over the next 50 years. The findings reveal that the Western region of Baoji exhibits a heightened hazard level, as depicted in the maps, which illustrate a 10% probability of exceedance within a 50-year timeframe. The probability of earthquake occurrence under various intensities (VI, VII, and VIII) over 50 years follows a declining trend from west to east. Furthermore, the likelihood of seismic intensity exceeding VI, VII, and VIII indicates the lowest exceeding probability in the northeast and the highest in the northwest. Notably, for intensities VI-VII, the difference between occurrence probability and extreme probability approaches twice, gradually diminishing with increasing intensity. This study underscores the MCPSHA model's efficacy in providing robust technical support for mitigating earthquake risk and enhancing the precision of earthquake insurance premium rate calculations. [ABSTRACT FROM AUTHOR]

This study focuses on the seismic safety of distributed underground reservoirs in coal mines, especially in scenarios involving the establishment of multiple reservoirs within the same mining area, spanning different coal seams. Dynamic similarity model tests and numerical simulations are employed to investigate the construction and operation of these reservoirs under extreme conditions, such as mine tremors or earthquakes. Utilizing the Daliuta coal mine underground reservoir as a case study, a similarity material model test platform is established to represent both upper and lower coal mine underground reservoirs. Stability tests are conducted on the interlayer rock mass under various levels of seismic intensity, and the safety of the interlayer rock mass at different safety distances is comparatively analyzed. Meanwhile, using the finite element method, the responses of the upper and lower coal mine underground reservoirs under different seismic intensity levels are simulated with the same conditions of model tests. Through the two types of simulations, the mechanical response and safety of the surrounding rock of the Daliuta coal mine underground reservoir under the influence of different seismic intensities are systematically analyzed, and the reasonable safety distances between the upper and lower reservoirs are obtained. This study provides a valuable scientific insight into the safe design of underground reservoir embankments in coal mines. [ABSTRACT FROM AUTHOR]

On 6 February 2023, two large earthquakes struck southern Türkiye on the same day, resulting in a considerable loss of life and property damage over a large region that included 11 cities. After these disasters, there was a requirement to define the soil-related intensity distribution, aside from manufacturing defects caused by buildings. The modified Mercalli intensity (MMI) scale results in the same intensity value (XI) when decimal values are not mathematically considered, even though the fundamental data in the AFAD and USGS sources differ. In this study, an equation based on the MMI–PGA relationship was obtained and tested with ten previously developed equations to calculate the earthquake intensity. Seven of these selected equations, depending on the earthquake magnitude, were calculated comparatively. The equation most compatible with the earthquakes that occurred on 6 February 2023 was obtained in this study. In addition, it was decided that three similar equations could also be used. Intensity distribution maps were created according to the calculated MMI values. In this way, it has been observed that different earthquake intensity values are more sensitive, reliable, objective, and sustainable. [ABSTRACT FROM AUTHOR]

Fragility curves of retaining walls constitute an efficient tool for the estimation of seismic risk and can be utilized for prevention from potential damage or for immediate decision-making. In this work, fragility curves for cantilever retaining walls of three different heights are proposed, considering cohesionless soil materials. The seismic response of the soil-wall system, in terms of permanent vertical ground displacement of the backfill soil and permanent horizontal displacement of the wall's base, is estimated by conducting non-linear time history analyses, through the 2D finite element simulation method. Five initial conditions are investigated regarding the value of the global factor of safety (FS) under static conditions. An initial value of FS equal to 1.5 is considered for dry conditions. If the presence of the water table is taken into account, the corresponding FS drops to values ranging from 1.4 to 1.1. Parameters that characterize seismic intensity are evaluated based on criteria, in order to identify the intensity measures that best correlate with the system's response. Three damage states are adopted, corresponding to minor, moderate, and extensive damage. The approach of combined damage criteria is also investigated. Finally, fragility curves are derived demonstrating the degree of dependency on initial conditions. [ABSTRACT FROM AUTHOR]

The structural performance of shield tunnel structures is highly susceptible to degradation under complex environmental loads, with the most common manifestation being bolt preload loss. In this study, a shield tunnel numerical simulation model was established to analyze the seismic response of shield tunnels with varying degrees of bolt preload loss. Firstly, the deformation patterns of shield tunnel structures under seismic loads were analyzed. Subsequently, ellipticity and joint opening were selected as seismic resilience assessment indicators based on the mechanical response. A seismic resilience assessment model was then established, including three states: normal state, affected state, and recovered state. The results show a direct relationship between the recovery capacity of tunnel structures and the initial performance of the lining structure, as well as the magnitude of the load. The lower the degree of structure degradation, the greater the structural recovery capacity. Additionally, there is a positive correlation between residual deformation and the initial performance loss of shield tunnel structures, as well as the intensity of seismic loads. This study contributes to enriching the theoretical framework for the seismic resilience assessment of shield tunnels, which have significant implications and provide valuable references for engineering safety. [ABSTRACT FROM AUTHOR]

Early disaster responses in damaged areas after a large earthquake are indispensable for stakeholders to assess and grasp the impacts such as building and infrastructure damage and disrupted community functionality as soon as possible. This study introduces a quick estimation model for mapping seismic intensities and building losses in Bogotá, the capital city of Colombia. The model uses ground motion records in the seismic network, soil maps of average shear-wave velocity in the upper 30 m (Vs30) with site amplifications, building inventory, and vulnerability functions for all building types. The spatial distribution of ground motion intensities, including spectral accelerations, was estimated by interpolating the observed seismic intensities with the Vs30-based site amplifications. The losses (repair cost) for all the buildings were evaluated by integrating the estimated spectral accelerations, the building inventory, and the vulnerability functions. The spatial distributions of seismic intensities and building losses can be computed within a few minutes immediately after triggering earthquake motions in the seismic network. The proposed model demonstrates evaluations of the impacts for the Mw6.0 earthquake that occurred on December 2019 and an earthquake scenario with Mw7.0 from an active fault near the Bogotá region. [ABSTRACT FROM AUTHOR]

This manuscript investigates the bias introduced by scaling aftershock ground motions when evaluating the performance of structures subjected to earthquake sequences. The study focuses on different hysteretic behaviors exhibited by structures and selects eight intensity measures as scale indicators. A benchmark database comprising 274 recorded mainshock–aftershock ground motions is utilized for analysis. The findings reveal that scaling aftershock records using intensity measures such as SI (seismic intensity), PGV (peak ground velocity), IC (Arias intensity), and Sa (spectral acceleration) relative to mainshock records effectively controls the mean bias within 30% throughout the entire period range, given a maximum scale factor of 10.0. However, it is observed that the additional damage in systems exhibiting un-degrading hysteretic behavior is more significantly affected by aftershock ground motion scaling compared to systems with degrading hysteretic behavior. Furthermore, scaling aftershock ground motions upwards using relative Sa tends to overestimate the additional damage incurred by structures. These results emphasize the importance of considering the specific hysteretic behavior of structures when applying aftershock ground motion scaling, as well as selecting appropriate intensity measures for accurate evaluation of structural performance. [ABSTRACT FROM AUTHOR]

This paper investigates the seismic damage behavior of steel pipe pile wharves after pitting corrosion. The seismic intensity is treated as random, and a probabilistic strength model for randomly pitting corroded steel is utilized to assess the seismic response of a typical steel pipe pile wharf. By analyzing the internal force response of each pile and the deformation response of the deck and soil slope, the process of seismic failure in steel pipe pile wharves with different pitting corrosion ratios is investigated. The results demonstrate that pitting corrosion amplifies the internal force within the steel pipe piles, leading to more severe seismic damage. Additionally, probabilistic seismic demand functions are established for the most vulnerable row of piles affected by random pitting corrosion, and the seismic fragility of the pipe pile wharves considering different pitting corrosion ratios is evaluated. These findings provide valuable insights for the design and strengthening of steel pipe pile wharves. [ABSTRACT FROM AUTHOR]

Damage identification plays an important role in enhancing resilience by facilitating precise detection and assessment of structural impairments, thereby strengthening the resilience of critical infrastructure. A current challenge of vibration-based damage detection methods is the difficulty of enhancing the precision of the detection results. This problem can be approached through improving the noise reduction performance of algorithms. A novel method based partially on the errors-in-variables (EIV) model and its total least-squares (LS) algorithm is proposed in this study. Compared with a classical damage detection approach involving adoption of auto-regressive (AR) models and the least-squares (LS) method, the proposed method accounts for all the observation errors as well as the relationships between them, especially in an elevated level of noise, which leads to a better accuracy. Accordingly, a shaking table test and its corresponding finite element simulation of a full-scale web steel structure were conducted. The acceleration time-series output data of the model after suffering from different seismic intensities were used to identify damage using the presented detection method. The response and identification results of the experiment and the finite element analysis are consistent. The finding of this paper indicated that the presented approach is capable of detecting damage with a higher accuracy, especially when the signal noise is high. [ABSTRACT FROM AUTHOR]

The western region of China is rich in hydropower resources and characterized by unique geological conditions. For the construction or planned construction of high dams in this region, different types of cover layers are formed due to special geological structures, most of which are located in high seismic intensity zones. This study focuses on four different site conditions: hard ground, medium–hard ground, medium–soft ground, and weak ground. By simulating the dynamic response of concrete-face rockfill dams under near-fault earthquake excitation, the vertical settlement of the dam and the attenuation of seismic motion under different site conditions are analyzed. The research findings reveal a consistent trend where the vertical settlement of the dams progressively escalates with increasing dam height across all four site conditions. This settlement phenomenon is especially pronounced in weak ground conditions, posing a potential risk of failure. Furthermore, when subjected to near-fault pulse-type earthquake motions, the existence of weak soil layers significantly dampens the seismic forces experienced by the dam. This finding suggests that the weaker the geological conditions of the site, the more pronounced the attenuation effect of the seismic motion. Additionally, the overburden layers have a noticeable amplification effect on near-fault pulse-type earthquake motion. However, this amplification effect is not significant in weak ground, possibly due to the presence of weak soil layers restricting the propagation and amplification of seismic motion. In conclusion, these research findings have practical significance for the dynamic response of high dam construction in different site conditions in the western region of China. They provide a scientific basis for the design and construction of high dams and serve as a reference for the implementation of seismic mitigation measures and earthquake disaster prevention in engineering projects. [ABSTRACT FROM AUTHOR]

In this study, a shaking table test was conducted to investigate the presence of a liquefied soil layer at a subway station bottom plate. The seismic responses to soil and station structure were investigated by inputting seismic waves of different intensities. The following test results were obtained. As the intensity of the seismic response increases, liquefaction occurs in the soils located at the base of the station. The remainder of the soil liquefies to a lesser degree but still results in soil subsidence and damage to the soils on both sides of the station. In seismic loading conditions, the pore water pressure undergoes a process of "rapid growth and slow dissipation". As the seismic intensity increases, the main frequency of the soil near the structure develops from a high to a low frequency, and the main frequency of the soil far away from the structure does not change significantly, indicating that the presence of the structure has a significant effect on the working conditions of the soil. The peak acceleration, as well as the peak maximum dynamic strain in the center column of the station, occurs at the bottom of the center column at the platform level, and the maximum dynamic strain in the slab occurs at the bottom slab at the concourse level. [ABSTRACT FROM AUTHOR]

Strong aftershocks have the potential to cause accumulated damage in structures, a feature which has been reported in post-earthquake reconnaissance studies, particularly for eccentric or irregular structures. This study aims to investigate the seismic behaviors of eccentric RC structural models under mainshock–aftershock (MSAS) sequences. In this study, three-dimensional structural models with eccentricities of 5%, 10%, 15%, 20%, 25%, and 30%, and an eccentricity of 0 (symmetric structural model) are developed by changing the positions of the centers of the structural mass. A static pushover analysis and a nonlinear time history analysis are conducted on the structural models with different eccentricities considering unidirectional and bidirectional earthquake loading (including mainshock ground motion and MSAS sequences). The amplitude of the aftershock ground motion is scaled according to the structural damage levels calibrated with the inter-story drift ratio (IDR). Furthermore, the differences in seismic responses between the unidirectional and bidirectional eccentric structures are discussed. The results show that the peak displacements of the unidirectional eccentric structures under MSAS sequences are nearly 1.4 times higher than those under mainshock ground motions. The structural seismic responses under unidirectional earthquake loading are more sensitive to the intensity of aftershock ground motions than those under bidirectional earthquake loading. Compared with unidirectional eccentric structures, bidirectional eccentric structures are more sensitive to the intensity of aftershock ground motions and have larger torsional angles and more complex displacement trends. The maximum displacement and the maximum IDR of bidirectional eccentric structures under MSAS sequences can reach 1.5 times and 1.4 times of those under mainshock ground motions, respectively. [ABSTRACT FROM AUTHOR]

On 6 February 2023, two major earthquakes occurred in the Turkish province of Kahramanmaraş. The first earthquake with a magnitude of Mw 7.7 occurred in the center of Kahramanmaras, while the second earthquake with a magnitude of Mw 7.5 occurred in the region of Elbistan. These earthquakes caused heavy damage and loss of life in the affected regions. In particular, the Elbistan region experienced both earthquakes with great severity. Following the earthquakes, damage analyses were carried out on the earthquake-affected structures in this region. In the region, 1045 buildings were destroyed, 2640 buildings were heavily damaged, and 463 buildings were moderately damaged by the earthquakes. In this study, the relation between the material quality and the damage status of the affected buildings in the Elbistan region was investigated. A total of 20 buildings with heavy and moderate damage, built both before and after the year 2000, were selected for analysis. Samples were taken from these buildings, and the compressive strength values of the samples were obtained. Further, in situ experiments featuring the Schmidt and UPV tests were performed in the buildings. The results found that the buildings lacked adequate concrete strength. In particular, the post-2000 structures recorded concrete strength values below the established standard. This study proves the necessity of following established regulations in the design and construction of buildings in earthquake-prone zones, especially with respect to the construction materials used. [ABSTRACT FROM AUTHOR]

Fluid viscous dampers (FVDs) have shown their efficiency as energy-dissipating systems, reducing the effects induced on structures by dynamic loading conditions like earthquakes and winds. In this paper, the evolution of this technology is reviewed, with a focus on the current trends in development from passive to semi-active and adaptive systems and an emphasis on their advances in adaptability and control efficacy. The paper examines the implementation of semi-active FVDs such as electrorheological, magnetorheological, variable stiffness, and variable damping dampers. These devices have a high potential to mitigate the vibrations caused by earthquakes of different intensities. In addition, adaptive FVDs are presented. As semi-active devices, the adaptive ones can adjust their behavior according to the dynamic excitations' intensity; however, they are able to do that autonomously without the use of any external equipment. [ABSTRACT FROM AUTHOR]

The performance-based seismic design pretends to take care of the lives of the occupants and reduce the cost of damage caused by earthquakes. Several ways of estimating damage and economic losses have been developed, but most of them lack objectivity and have great dispersion in the results. In the last decade, the advancement of technology has allowed the appearance of new methodologies, such as the one developed by the Pacific Earthquake Engineering Research Center (PEER methodology). However, the information regarding application and scope is scarce. In the present investigation, the economic seismic performance for a steel building was determined by applying the PEER methodology with different levels of seismic intensity. A multi-family residential model of special moment frames (SMF) was used, and the structure was designed by means of modal analysis. Spectral, incremental dynamic non-linear analysis was performed where the structural response was determined, with the help of the PACT software. The seismic performance, expressed as the repair costs, repair times, deaths, and injuries, was defined. The results obtained indicate that buildings designed with traditional structural standards can be demolished after the action of an earthquake because the repair costs exceed 40% of the replacement cost. Rare and very rare seismic events can cause the total suspension of the service and a considerable number of deaths and injuries. [ABSTRACT FROM AUTHOR]

The assessment of rocking response is a challenging task due to its high nonlinearity. The present study investigates two methodologies to evaluate finite rocking rotations and overturn of three typical rocking systems. In particular, fuzzy linear regression (FLR) with triangular fuzzy numbers and a hybrid model combining logistic regression and fuzzy logic were adopted. To this end, three typical rocking structures were considered, and nonlinear time history analyses were performed to obtain their maximum response. Eighteen seismic intensity measures (IMs) extracted from recorded seismic accelerograms were considered to predict the responses. In the absence of rocking overturn, the finite rocking rotations and similarity ratios were calculated by adopting the FLR method. Moreover, extensive analysis was performed to evaluate the influence of each IM on the model's predictions. On the other hand, rocking overturn was evaluated by logistic regression to compute the probability of collapse, followed by the FLR method to estimate the similarity between the different rocking-based structural systems. The root mean square error (RMSE) parameter and the log loss function were determined for every model to assess the predictions that emerged from the two fuzzy methods. As indicated, both methods demonstrated satisfactory results, presenting minimal deviations from the observed values. Finally, in the case of finite rocking rotation predictive models, remarkably high similarity ratios were observed among the various structures, with a median value of 0.96. [ABSTRACT FROM AUTHOR]

Türkiye experienced great destruction during the Kahramanmaraş earthquake couple which occurred as Pazarcık (Mw = 7.7) and Elbistan (Mw = 7.6) on 6 February 2023. The weak structural characteristics and the magnitude of the earthquakes caused more than 50,000 casualties. Significant damage occurred in both urban and rural building stock in 11 different provinces that were primarily affected by the earthquakes. The dominant building stock is masonry structures in the rural areas of the earthquake region. Structural damages at various levels have occurred in adobe masonry structures built using local labours and resources without any engineering service. The main purpose of this study is to examine the failure and collapse mechanisms of adobe structures after Kahramanmaraş earthquakes in detail. First of all, information about both earthquakes was given. The earthquake intensity for all provinces was obtained by using the peak ground acceleration-intensity relation suggested for Türkiye, taking into account the measured PGAs in earthquakes. The observed structural damages were evaluated in terms of earthquake and civil engineering in adobe structures. Damage classification was conducted using European Macro-Seismic Scale (EMS-98) for a total of 100 adobe buildings. Of these structures, 25% were destroyed, 49% were heavily damaged, 15% were damaged moderately, and 11% were damaged slightly. In addition, the rules regarding adobe structures were compared considering the last two earthquake design codes used in Türkiye. In the study, suggestions were also presented to prevent structural damage in the adobe buildings in the earthquake region. Low strength of adobe material, usage of heavy earthen roofs, failure to comply with earthquake-resistant building design principles, and insufficient support of load-bearing walls are the main causes of damage. [ABSTRACT FROM AUTHOR]

The objective of this study is to present a novel fragility analysis method that combines principal component analysis (PCA) and the K-means clustering algorithm for a probability assessment of seismic damage in high-pier bridges undergoing pulse-like ground motions. Firstly, the method uses the correlation coefficient and the condition number as judgment indices to eliminate those seismic intensity measures (IMs) with weak correlation and multicollinearity from all 29 of the initial candidate seismic IMs, the optimal combination of IMs that satisfies the requirements for the PCA method is determined. Secondly, the method utilizes PCA to reduce the dimensionality of the optimal combination of IMs to obtain the principal components, after which the K-means algorithm is applied to classify the original group of selected pulse-like ground motions into four classes. Thirdly, a 3D finite element model of the exemplary high-pier bridge is developed via OpenSees, while incremental nonlinear dynamic time-history analyses are conducted to record the maximum cross-section curvatures of high piers under the influence of various categories of ground motions. Finally, based on the analytical procedures used in the increment dynamic analysis (IDA) method, this study develops and compares the fragility curves for the various classes of pulse-like ground motions. The results indicate the necessity of utilizing the PCA and K-means approach for classifying pulse-like ground motions in the seismic fragility analysis of high-pier bridges. This approach also significantly improves the precision and accuracy of damage probability analysis. [ABSTRACT FROM AUTHOR]

During intense ground motion excitations, the pounding between adjacent buildings may result in extensive structural damage. Despite the provision of regulations regarding the minimum separation gap required to prevent structural collisions, the majority of existing structures are poorly separated. The modern seismic design and assessment of structures are based on the definition of acceptable response levels in relation to the intensity of seismic action, which is usually determined by an acceptable probability of exceedance. From this point of view, the seismic performance of a typical eight-storey reinforced concrete (RC) frame structure is evaluated in terms of pounding. In particular, the performance is evaluated using six different separation gap distances as a fraction of the EC8 minimum distance. As the height of the adjacent structure affected the required separation distance, the examined RC structure was assumed to interact with four idealized rigid structures of one to four storeys. The typical storey height was equal between the examined structures; therefore, collision could occur at the diaphragm level. To this end, incidental dynamic analyses (IDAs) were performed, and the fragility curves for different limit states were obtained for each case. Finally, the seismic fragility was combined with the hazard data to evaluate the seismic performance probabilistically. [ABSTRACT FROM AUTHOR]

On February 6, 2023 (local time), two earthquakes (Mw7.8 and Mw7.7) struck central and southern Turkey, causing extensive damage to several cities and claiming a toll of 40,000 lives. In this study, we propose a method for seismic building damage assessment and analysis by combining SAR amplitude and phase coherence change detection. We determined building damage in five severely impacted urban areas and calculated the damage ratio by measuring the urban area and the damaged area. The largest damage ratio of 18.93% is observed in Nurdagi, and the smallest ratio of 7.59% is found in Islahiye. We verified the results by comparing them with high-resolution optical images and AI recognition results from the Microsoft team. We also used pixel offset tracking (POT) technology and D-InSAR technology to obtain surface deformation using Sentinel-1A images and analyzed the relationship between surface deformation and post-earthquake urban building damage. The results show that Nurdagi has the largest urban average surface deformation of 0.48 m and Antakya has the smallest deformation of 0.09 m. We found that buildings in the areas with steeper slopes or closer to earthquake faults have higher risk of collapse. We also discussed the influence of SAR image parameters on building change recognition. Image resolution and observation geometry have a great influence on the change detection results, and the resolution can be improved by various means to raise the recognition accuracy. Our research findings can guide earthquake disaster assessment and analysis and identify influential factors of earthquake damage. [ABSTRACT FROM AUTHOR]

Single-column elevated station structures are irregular structures with long-span cantilever beams and individual pier columns in the transverse section. The uneven mass and stiffness in the horizontal and vertical planes necessitate research on the seismic performance of these structures. This study performed a nonlinear response-history analysis (NRHA) of a single-column elevated station structure using the finite element program MSC.MARC and analysed its seismic performance under different seismic intensities. The stress states of the primary components were evaluated, and the effect of vertical earthquake motion on the seismic performance of the structure was considered. The torsional behavior caused by the uneven mass and stiffness in both horizontal and vertical directions should be considered, and energy dissipation measures should be taken to reduce the internal force and deformation of the bottom-pier columns and second-floor columns in the process of designation to improve the seismic performance of the structure. A bidirectional pushover analysis (BPA) was applied. The load amplification factor was adjusted to optimize the BPA results. The results of the modified BPA were similar to those of the NRHA, indicating the computational reliability of the modified BPA. The modified BPA method was accurate, applicative, and efficient. The BPA can improve computational efficiency compared to NRHA and can be widely applied in the structural design process for practical engineering applications. [ABSTRACT FROM AUTHOR]

A comprehensive assessment of a city's vulnerability and resilience is a prerequisite for an effective response to a natural disaster, such as an earthquake. However, an appropriate method for assessing the seismic performance of a complex urban system is still being researched. To address this gap, the purpose of this paper is to introduce a method for seismic performance assessment of a city as a socio-physical system. Therefore, various studies of individual urban components and their interactions were combined into a holistic framework and presented in a case study of a small mid-European town. The seismic vulnerability of the building inventory was assumed or assessed based on the fragility curves adopted from the literature on similar European building stock. Seismic scenarios of different earthquake intensity (PGA of 0.15 g and 0.30 g) combined with conservative and risky approaches were applied. Considering the human perspective, urban performance was evaluated on the basis of accessibility to urban services that satisfy basic human needs (for survival and protection) via graph theory measures of global efficiency and the shortest path. The temporal aspect (before the earthquake, immediately after it, after evacuation, and after recovery) was also included to obtain a comprehensive resilience assessment. It turned out that a stronger earthquake (PGA of 0.30 g) would have far-reaching consequences for the urban performance of the investigated town, and the old city center would be particularly affected. Following the event, the system's performance is less than half as effective compared to the initial level, indicating a sharp deterioration in the quality of life as reflected in the possibility of meeting basic human needs. [ABSTRACT FROM AUTHOR]

The present work aims to assess the large-scale seismic vulnerability of a set of 55 reinforced concrete educational establishments of different typologies (approximately 516 constructions) located within the urban perimeter of the city of Mostaganem. Among them, 328 buildings were constructed in accordance with the Algerian seismic regulation (built after 1980), while 188 constructions were built without a seismic design code (built before < 1980). This classification corresponds to the application/creation of this regulation following a major earthquake in Chlef (El Asnam) in 1980. Using the RISK-UE lm1 method, the vulnerability index was assessed based on a visual inspection for each building using an on-site inventory form to determine the general sources of seismic vulnerability. This strategy allows the prioritization of constructions according to their typologies, considering the structural system of the building and modifying factors, such as code level, maintenance condition, number of floors, plan and elevation irregularities, soil morphology, etc. The application of this methodology generated several seismic scenarios expressing the probable damage to the constructions, and the following results were suggested: The first two seismic scenarios have no damage corresponding to intensities I = 5; 6. The third scenario is characterized by low to negligible damage corresponding to intensity I = 7. Moderate damage was observed for the fourth seismic scenario (I = 8), while the fifth scenario generated by seismic intensity I = 9 presents moderate to heavy damage. The sixth scenario, with intensity I = 10, exhibits a relatively heavy damage balance. Starting from intensity I = 11, the damage becomes heavy to very heavy for the seventh scenario. Finally, the eighth scenario describes total destruction of the constructions. The results obtained from the application of this methodology on the educational buildings have been integrated into a Geographic Information System (GIS) environment to better understand the seismic behavior of the structures and to estimate the magnitude of seismic risk. This facilitates simulation and enables efforts to be made to take concrete preventive measures to strengthen existing educational buildings, thus reducing the negative impact of future earthquakes. [ABSTRACT FROM AUTHOR]

For buildings that meet the requirements of current seismic design codes, damage to nonstructural components and the internal objects of buildings often become the main source of the seismic economic losses of these buildings. However, the current specifications only consider the safety of 'no collapse under strong earthquake' and do not consider 'functional recoverability'. In this paper, a six-story frame building was taken as an example. Four joint performance limit states were proposed, as per FEMA 273, to establish a two-dimensional probabilistic seismic demand model that considers parameter correlations. The limit state function was established, and the two-dimensional seismic vulnerability curve was calculated. The seismic intensity–economic loss curve and the annual average economic loss established by one-dimensional and two-dimensional seismic vulnerability curves were compared. The results showed that the seismic performance of the structure was lower than expected when using only a one-dimensional seismic vulnerability curve. However, the situation was more serious under high-intensity earthquake and high-performance levels. [ABSTRACT FROM AUTHOR]

The structure is said to be damaged if there is a permanent shift in the post-event natural frequency of a structure as compared with the pre-event frequency. To assess the damage to the structure, a time-frequency approach that can capture the pre-event and post-event frequency of the structure is required. In this study, to determine these frequencies, a local maximum synchrosqueezing transform (LMSST) method is employed. Through the simulation results, we have shown that the traditional methods such as the Wigner distribution, Wigner–Ville distributions, pseudo-Wigner–Ville distributions, smoothed pseudo-Wigner–Ville distribution, and synchrosqueezing transforms are not capable of capturing the pre-event and post-event frequency of the structure. The amplitude of the signal captured by sensors during those events is very small compared with the signal captured during the seismic event. Thus, traditional methods cannot capture the frequency of pre-event and post-event, whereas LMSST employed in this work can easily identify these frequencies. This attribute of LMSST makes it a very attractive method for post-earthquake damage detection. In this study, these claims are qualitatively and quantitatively substantiated by comprehensive numerical analysis. [ABSTRACT FROM AUTHOR]

With the gradual development of and improvement in earthquake early warning systems (EEWS), more accurate real-time seismic intensity measurements (IMs) methods are needed to assess the impact range of earthquake intensities. Although traditional point source warning systems have made some progress in terms of predicting earthquake source parameters, they are still inadequate at assessing the accuracy of IMs predictions. In this paper, we aim to explore the current state of the field by reviewing real-time seismic IMs methods. First, we analyze different views on the ultimate earthquake magnitude and rupture initiation behavior. Then, we summarize the progress of IMs predictions as they relate to regional and field warnings. The applications of finite faults and simulated seismic wave fields in IMs predictions are analyzed. Finally, the methods used to evaluate IMs are discussed in terms of the accuracy of the IMs measured by different algorithms and the cost of alerts. The trend of IMs prediction methods in real time is diversified, and the integration of various types of warning algorithms and of various configurations of seismic station equipment in an integrated earthquake warning network is an important development trend for future EEWS construction. [ABSTRACT FROM AUTHOR]

At present, traditional seismic design methods often ignore the structural damage caused by aftershocks in the evaluation of structural stability. In this paper, seven main aftershock sequences were constructed by using the attenuation method. The incremental dynamic analysis method (IDA) was used to analyze the nonlinear dynamic time history of the aqueduct structure. The main aftershock vulnerability curve of the aqueduct structure was obtained by taking the seismic intensity IM and the maximum ratio of the plastic strain energy to the total strain energy D p as the structural performance parameter. The analysis results show that the residual displacement of the aqueduct increases by 33%, 66%, 44%, 37%, 0.01%, 60%, and 59%, respectively, under the seven main aftershock sequences. The incremental damage percentages of the aftershock at the end of the period were 9.85%, 15.00%, 26.53%, 2.10%, 0.9%, 35.97%, and 9.85%, respectively. The main aftershock made the damage at the bottom of the arch and the aqueduct more extensive. When the earthquake intensity is 0.3 g, the exceedance probabilities of moderate damage and severe damage are 62.68% and 14.39%, respectively, under the action of the main aftershock sequence. The exceedance probabilities under the action of the main aftershock sequence are 38.52% and 12.08% higher than that of the single main earthquake, respectively. [ABSTRACT FROM AUTHOR]