Search Results (778)

Pile foundation failures during earthquakes can cause severe structural damage, emphasizing the importance of accurate strength evaluation. This study focuses on concrete-filled steel pipe pile heads with inner ribs, which play a crucial role in resisting compressive loads. Compression tests were conducted on specimens simulating pile heads to investigate stress transfer between the steel pipe and infill concrete. A numerical analysis model was developed using ABAQUS 6.14 and validated against experimental results, successfully reproducing load-deformation relationships and stress transfer mechanisms. Simulations extended the study by analyzing the bearing strength of the infill concrete under rib-induced pressure, with varying diameter-to-thickness ratios D/t. The results show that the compressive strength is primarily governed by the combined effects of steel pipe buckling resistance and concrete bearing resistance of a single layer of inner ribs. The proposed evaluation formula provides a lower-bound estimate of compressive strength and effectively captures key parameters influencing performance. Full article

This review article presents a detailed investigation into the seismic behavior of structures employing supplementary dampers or additional damping mechanisms over the past decade. The study covers a range of damping systems, including viscous, viscoelastic, and friction dampers, as well as tuned mass dampers and other approaches. A systematic analysis of more than 160 publications in the current literature is undertaken, providing a clear overview of structures equipped with supplementary damping devices and the challenges they face. The theoretical principles that underpin these technologies are examined, along with their practical applications and effectiveness in alleviating seismic effects. Additionally, the article highlights recent developments in the design of damping devices, the challenges related to their implementation, and prospective directions for future research. By synthesizing results from experimental studies, numerical simulations, and real-world applications, this review offers valuable insights for researchers and engineers involved in the design of earthquake-resistant structures. Full article

It is of great importance to quantify the seismic damage of reinforced concrete (RC) short columns since they often experience severe damage due to likely excessive shear deformation. In this paper, the seismic damage quantification method of RC short columns under earthquakes is proposed based on crack images and the enhanced U-Net. To this end, RC short-column specimens were prepared and tested under cyclic loading. The force-displacement hysteresis curves were obtained to quantitatively calculate the damage indicator of the RC short column based on the energy criterion. At the same time, crack images of the column surfaces were taken by smartphones using the partition photographing scheme and image stitching algorithm. The widely used U-Net was enhanced by adding a double attention mechanism to segment the cracks in the images. The results demonstrate that it has better accuracy in terms of recognizing tiny cracks compared to the original U-Net. By image analysis, the crack information was further extracted from the crack images to investigate the damage development of RC short columns. Finally, correlations between the damage indicator based on the energy criterion and crack information of the RC short columns under cyclic loading were analyzed, showing that the highest correlation exists between the damage indicator and the total crack area. Finally, the normalized total crack area, i.e., the ratio between the total crack area and the corresponding monitored area of the surface, is defined to quantify the seismic damage of RC short columns when utilizing crack images for damage assessment. Full article

Due to its high axial bearing capacity and good ductility, the embedded steel plate composite shear wall structure has become one of the most widely used lateral force-resisting structural members in building construction. However, bending failure is prone to occur during strong earthquakes, and the single energy dissipation mechanism of the plastic hinge zone at the bottom leads to the concentration of local wall damage. To improve the embedded steel plate composite shear wall structure, the plastic hinge zone of the composite shear wall is replaced by fiber-reinforced concrete (FRC) and analyzed by ABAQUS finite element simulation analysis. Firstly, the structural model of the embedded steel plate composite shear wall structure with FRC in the plastic hinge zone is established and the accuracy of the model is verified. Secondly, the effects of steel ratio, longitudinal reinforcement ratio, and FRC strength on the bearing capacity of composite shear walls are analyzed by numerical simulation. Finally, a method for calculating the embedded steel plate composite shear wall structure with FRC in the plastic hinge zone is proposed. It is shown that the displacement and load curves and failure modes of the model are basically consistent with the experimental results, and the model has high accuracy. The axial compression ratio and FRC strength have a great influence on the bearing capacity of composite shear walls. The calculation formula of the normal section bending capacity of the embedded steel plate composite shear wall structure with FRC in the plastic hinge zone is proposed. The calculated values of the bending capacity are in good agreement with the simulated values, which can provide a reference for its engineering application. Full article

This paper focuses on the theoretical and analytical modeling of a novel seismic isolator termed the Passive Friction Mechanical Metamaterial Seismic Isolator (PFSMBI) system, which is designed for seismic hazard mitigation in multi-story buildings. The PFSMBI system consists of a lattice structure composed of a series of identical small cells interconnected by layers made of viscoelastic materials. The main function of the lattice is to shift the fundamental natural frequency of the building away from the dominant frequency of earthquake excitations by creating low-frequency bandgaps (FBGs) below 20 Hz. In this configuration, each unit cell contains an inner resonator that slides over a friction surface while it is tuned to vibrate at the fundamental natural frequency of the building. This resonance enhances the energy dissipation capacity of the PFSMBI system. After deriving the governing equations for four selected lattice configurations (i.e., Cases 1–4), a parametric study is performed to optimize the PFSMBI system for a wide range of harmonic ground motion frequencies. In this study, we examine how key parameters, such as the mass ratios of the cells and resonators, tuning frequency ratios, the number of cells, and the coefficient of friction, affect the system’s performance. The PFSMBI system is then incorporated into the dynamic model of a six-story base-isolated building to evaluate its effectiveness in reducing the floor acceleration and inter-story drift under actual earthquake ground motion records. This dynamic model is used to investigate the effect of stick–slip motion (SSM) on the energy dissipation performance of a PFSMBI system by employing the LuGre friction model. The numerical results show that the optimized PFSMBI system, through its lattice structure and frictional resonators, effectively reduces floor acceleration and inter-story drift by leveraging FBGs and frictional energy dissipation, particularly when SSM effects are properly accounted for. Finally, a small-scale prototype of the PFSMBI system with two cells is developed to verify the effect of SSM. This experimental validation highlights that neglecting SSM can lead to an overestimation of the energy dissipation performance of PFSMBI systems. Full article

On 23 March 2018, an event of magnitude M_L 3.9 occurred about 10 km from the town of Ostuni, in the Adriatic offshore. It was the most energetic earthquake in South–Central Apulia ever recorded instrumentally. On 13 February 2019, in the same area, a second M_L 3.3 event was recorded. The analysis of the 2018 event shows that the ambiguity of the solution of the fault plane reported by INGV (Istituto Nazionale di Geofisica e Vulcanologia) on the Italian National Earthquake Centre website can be solved considering existing seismic profiles, exploration well logs and the Quaternary activity of faults in the epicentral area. A seismogenic source was identified in the rupture of a small portion of a 40 km length structure with strike NW-SE, dipping at a high angle toward the south. In this work, we have relocated the recent earthquakes by using the seismic stations managed by the University of Bari (UniBa), one of which is quite close to the event’s epicenter (about 20 km), together with data coming from the RSN (Rete Sismica Nazionale). Furthermore, we have determined the focal mechanism of some events, with implications on stress field of the area. Our results show right-lateral transtensional kinematics of the seismogenic faults along approximately E-W striking planes, with a tension, T, with a trend of about 60° (NE-SW direction) and a plunge of 20°. Finally, we have tried to correlate the location of the four best constrained earthquakes with their seismogenic structures. Full article

Many landslides triggered by earthquakes have caused a countless loss of life and property, therefore, it is very important to predict landslide hazards accurately. In this work, regional seismic landslide data were obtained via a field survey, remote sensing interpretation, and data collection, and a multilevel physical and mechanical parameter system for seismic landslide hazard assessment was established; this system included a landslide inventory, loose accumulation layers, and geological units, enabling higher accuracy in the data. The Newmark displacement model with a modified correlation coefficient was used to assess the regional seismic landslide hazard in four scenarios (a = 0.1, 0.2, 0.3, 0.4) to study the influence of the landslide hazard at different peak ground accelerations. Moreover, the information value model was used to modify the calculated results to improve their accuracy in the assessment. By assessing the potential seismic landslide hazard in Shimian County in the upper reaches of the Yangtze River, the regional landslide distribution and pattern at different peak ground accelerations were obtained. The results show that with decreasing parameter accuracy in the system, the importance of the landslide inventory increases. When the peak ground acceleration is a = 0.3, which can be defined as a high hazard grade, in which the landslide area demonstrates a large-scale sharp increase, a devastating hazard threshold is reached. As the peak ground acceleration increases, the factor controlling landslides transforms from the landslide inventory to the slope, which reflects the reasonableness of the parameters in the system. The input parameters were regarded as important factors for efficiently increasing the accuracy of the results of the Newmark displacement model in the discussion. Full article

The widely used Bouc–Wen–Baber–Noori (BWBN) hysteresis model, although effective in simulating hysteresis behaviors, does not account for variations in the pinching region of hysteretic behaviors. This can negatively impact the accuracy of the BWBN model in simulating structural responses and damage mechanisms in structures such as reinforced concrete (RC) and timber, which exhibit highly pinched hysteresis behavior when damaged by earthquakes. This paper introduces a BWBN model with varying pinching region characteristics (BWBN-VP model) which can degrade pinching stiffness and increase pinching effects under seismic loads. Unlike the original BWBN model using constant pinching stiffness ($k_p$), this modified new model, inspired by real-world structural damage, improves structural damage detection, identifiability, and analysis in real-world scenarios. Model validation uses experimental data from three RC column tests with different failure modes and hysteresis loop shapes, resulting in an ~0.98 correlation coefficient between the experimental and simulated responses. Further validation uses real-world seismic data from a six-story RC building and achieves an average correlation of ~0.97 with a minor 2.5% difference in the peak restoring forces compared to direct measurements. The proposed BWBN-VP model also accurately and realistically captures damage to both the elastic and pinching stiffness values of the building, with an average difference of ~4%. Results confirm that the BWBN-VP model, compared to the original, more accurately predicts hysteretic responses, especially in Shear Failure (SF) modes. Therefore, the BWBN-VP model, superior in simulating highly pinched behaviors in RC and timber structures, would be an advanced tool for resilient seismic design and Structural Health Monitoring (SHM). Full article

In the last decades, the scientific community has been focused on searching earthquake signatures in the Earth’s atmosphere, ionosphere, and magnetosphere. This work investigates an offshore Mw 5.5 earthquake that struck off the Marche region’s coast (Italy) on 9 November 2022, with a focus on the potential coupling between the Earth’s lithosphere, atmosphere, and magnetosphere triggered by the seismic event. Analysis of atmospheric temperature data from ERA5 reveals a significant increase in potential energy (Ep) at the earthquake’s epicenter, consistent with the generation of Atmospheric Gravity Waves (AGWs). This finding is further corroborated by the MILC analytical model, which accurately simulates the observed Ep trends (within 5%), supporting the theory of Lithosphere–Atmosphere–Ionosphere–Magnetosphere coupling. The study also examines the vertical Total Electron Content (vTEC) and finds notable fluctuations at the epicenter, exhibiting periodicities (7–12 min) characteristic of AGWs and traveling ionospheric disturbances. The correlation between ERA5 observations and MILC model predictions, particularly in temperature deviations and Ep distributions, strengthens the hypothesis that earthquake-generated AGWs impact atmospheric conditions at high altitudes, leading to observable ionospheric perturbations. This research contributes to a deeper understanding of Lithosphere–Atmosphere–Ionosphere–Magnetosphere coupling mechanisms and the potential for developing reliable earthquake prediction tools. Full article

In recent seismic events that occurred worldwide and in Peru, it has been observed that irregular structures in plan present greater structural damage compared to regular structures. Investigations carried out after seismic events indicate that irregular plan structures collapse due to erroneous structural conception and poor seismic analysis. Likewise, the Peruvian earthquake-resistant standard does not establish a permissible limit for the degree of irregularity under analysis, instead qualitatively assessing the structural irregularity. The objective of this article was to study the effect of plan irregularities using innovative methodologies on the structural response of tall 10-story reinforced concrete buildings. In this sense, seventeen (17) structural models are proposed that reflect different irregular configurations in plan: 06 structures Type L, 05 structures Type I, 05 structures Type I, and one regular building. These buildings are numerically modeled using ETABS software V.18.0 through modal analysis, Modal Spectral and Linear Time History (MSLTH), and Multi-Mode Pushover (MPA). For the MSLTH, seven (07) pairs of representative Peruvian earthquakes were analyzed. The results of the modal analysis evaluated in the first two vibration modes demonstrated that Type L irregular structures change their behavior from translational to torsional when the structures present an irregularity greater than 57%. Type I and O structures present translational behavior. Furthermore, the results of the Modal Spectral and MSLTH analysis demonstrate that Type L structures present greater displacements and drifts in both directions. The shear force and the overturning moment for Types L, I, and O decrease as the irregularity in plan increases. Finally, the results of the MPA for irregular Type L structures demonstrated that the lateral stiffness of the structures decreases as the irregularity in plan is critical, increasing the possibility of the formation of plastic mechanisms in the structural elements. Full article

It has been recently argued that numerous enigmatic observations remain challenging to explain within the framework of conventional physics. These anomalies include unexpected correlations between temperature variations in the stratosphere, the total electron content of the Earth’s atmosphere, and earthquake activity on one hand and the positions of planets on the other. Decades of collected data provide statistically significant evidence for these observed correlations. These works suggest that these correlations arise from strongly interacting “streaming invisible matter” which gets gravitationally focused by the solar system bodies including the Earth’s inner mass distribution. Here, we propose that some of these, as well as other anomalies, may be explained by rare yet energetic events involving the so-called axion quark nuggets (AQNs) impacting the Earth. In other words, we identify the “streaming invisible matter” conjectured in that works with AQNs, offering a concrete microscopic mechanism to elucidate the observed correlations. It is important to note that the AQN model was originally developed to address the observed similarity between the dark matter and visible matter densities in the Universe, i.e., ${\mathrm{\Omega }}_{\mathrm{DM}}\sim {\mathrm{\Omega }}_{\mathrm{visible}}$, and not to explain the anomalies discussed here. Nonetheless, we support our proposal by demonstrating that the intensity and spectral characteristics of AQN-induced events are consistent with the aforementioned puzzling observations. Full article

On 5 September 2022, the moment magnitude (Mw) 6.7 Luding earthquake struck in the Xianshuihe Fault system on the eastern edge of the Tibet Plateau, illuminating the seismic gap in the Moxi segment. The fault system geometry and rupture process of this earthquake are relatively complex. To better understand the underlying driving mechanisms, this study first uses the Interferometric Synthetic Aperture Radar (InSAR) technique to obtain static surface displacements, which are then combined with Global Positioning System (GPS) data to invert the coseismic slip distribution. A machine learning approach is applied to extract a high-quality aftershock catalog from the original seismic waveform data, enabling the analysis of the spatiotemporal characteristics of aftershock activity. The catalog is subsequently used for fault fitting to determine a reliable fault geometry. The coseismic slip is dominated by left-lateral strike-slip motion, distributed within a depth range of 0–15 km, with a maximum fault slip > 2 m. The relocated catalog contains 15,571 events. Aftershock activity is divided into four main seismic clusters, with two smaller clusters located to the north and south and four interval zones in between. The geometry of the five faults is fitted, revealing the complexity of the Xianshuihe Fault system. Additionally, the Luding earthquake did not fully rupture the Moxi segment. The unruptured areas to the north of the mainshock, as well as regions to the south near the Anninghe Fault, pose a potential seismic hazard. Full article

Non-autoclaved aerated concrete (NAAC) is gaining attention for its strength-to-weight ratio and sustainability benefits. Produced by incorporating a blowing agent into a binder, aggregate, and water mixture, NAAC offers a lightweight and porous construction material. Ash and slag waste (ASW), primarily composed of silicon, aluminum, iron, and calcium oxides, presents significant potential as a sustainable additive. However, industrial-scale processing of ASW still needs to be explored in Kazakhstan. This study evaluates the feasibility of utilizing ASW from the Ust-Kamenogorsk Thermal Power Plant to produce earthquake-resistant NAAC. Incorporating 31.5% ASW by weight optimizes compressive strength, achieving 2.35 MPa and significantly improving the mechanical properties. Chemical and microstructural analyses confirm ASW’s suitability as a construction material. The study also introduces innovative processing methods and explores convolutional neural network models for predicting material structure changes, providing insights into optimizing production processes. The findings address the research objectives by confirming the viability of ASW in NAAC production and demonstrating its potential for sustainable construction. The results offer a pathway for industrial-scale applications, contributing to waste utilization and resource conservation. Full article

The using of flat slab systems is a common structural solution for residential and commercial buildings as they are a cost-effective structural solution that simplifies and speeds up the construction phase. However, the flat slab systems have complex behavior, particularly in the slab–column connection zones, because of punching shear. Therefore, to prevent brittle flat slab collapse because of punching shear, there are some conditions which must be met in regulations such as Eurocode 2, American Concrete Institute’s Code, and Türkiye Building Earthquake Code—2018. Flat slab collapses because of punching shear can be caused by deficiencies in the design phase as well as deficiencies in the construction phase. The purpose of this study is to investigate the causes of flat slab collapses due to punching shear, focusing on whether these failures arise from design or construction deficiencies. The study highlights the importance of adhering to regulations to prevent brittle flat slab collapses. A case study of an actual building collapse due to punching shear was conducted. Theoretical punching shear strength was calculated based on the Türkiye Building Earthquake Code—2018. A finite element model of the collapsed part of the building was created, and collapse mechanism simulations were performed. It was examined whether the punching collapse mechanism was caused by deficiencies in the design or the construction phase. The findings revealed the critical role of proper design phases and construction practices in ensuring structural integrity. Full article

This study investigates the structural behavior of bahareque earth walls, a traditional construction system commonly used in rural areas of northern South America. Bahareque (wattle and daub) walls, consisting of guadua (a bamboo-like material) or wooden frames filled with soil mixes, have demonstrated considerable resilience in seismic zones due to their lightweight and flexible nature. Despite their widespread use in these communities, limited scientific data exist on their seismic performance under in-plane pseudo-static horizontal loading. This research addresses this gap by experimentally evaluating the seismic behavior of five wall models with different combinations of guadua, wood, and earth filling materials. The methodology included four main phases, namely field visits to document traditional construction techniques, material characterization, prototype testing under pseudo-static loads, and an analysis of mechanical behavior. Key material properties, including compressive strength and Young’s modulus, were determined, alongside the mechanical and physical properties of the infill material, which incorporated natural fibers. Pseudo-static tests were conducted on five wall prototypes, featuring various configurations of guadua and wood frameworks, both with and without soil infill. The walls were subjected to horizontal in-plane loads to assess their deformation capacity, energy dissipation, and failure mechanisms. The results indicated that walls with soil mixture infill—specifically the GSHS (guadua frame with horizontal guadua strips and soil mixture infill) and TSHS (wood frame with horizontal guadua strips and soil mixture infill) configurations—demonstrated the best seismic performance, with maximum displacements reaching up to 166 mm and strengths ranging from 6.4 to 8.4 kN. The study concludes that bahareque walls, particularly those incorporating soil mixes and horizontal guadua strips, exhibit high resilience under seismic conditions and provide a sustainable construction alternative for rural regions. The scope of this study is limited by the exclusion of dynamic seismic simulations, which could offer additional insights into the behavior of bahareque walls under real earthquake conditions. The novelty of this research lies in the direct evaluation of the seismic performance of traditional bahareque configurations, specifically comparing walls constructed with guadua and wooden frameworks, while emphasizing the critical role of soil infill and guadua strips in structural performance. Full article