Seismic Areas Research Articles

Detecting DC Electrical Resistivity Changes in Seismic Active Areas: State-of-the-Art and Future Directions

In this paper, a critical review of the geoelectrical monitoring activities carried out in seismically active areas is presented and discussed. The electrical resistivity of rocks is one of the geophysical parameters of greatest interest in the study of possible seismic precursors, and it is strongly influenced by the presence of highly fractured zones with high permeability and fluid levels. The analysis in the present study was carried out on results obtained over the last 50 years in seismic zones in China, Japan, the USA and Russia. These past works made it possible to classify the different monitoring strategies, analyze the theoretical models for interpreting possible correlations between anomalies in resistivity signals and local seismicity, and identify the main scientific and technological gaps in the literature. In addition, great attention has been paid to some recent works on the study of the correlations between focal mechanisms and the shapes of anomalous patterns in resistivity time series. Finally, some future scenarios for the development of new activities in this field have been identified.

The influence of soils of selected sites of Addis Ababa on predicted earthquake ground motions

One-dimensional nonlinear ground response analyses were conducted on selected sites of Addis Ababa. The sites were characterized based on the results of seismic and geotechnical surveys. Input motions were selected from the Pacific Earthquake Engineering Research Center (PEER) ground motion database. The results of the analyses show that the selected sites have a potential amplification significantly higher than the current seismic code specifications. In particular, the average PSA obtained at the ground surface is more than double the code values in the lower period range of up to 1.3 s. Considering that most buildings lie within this range, this calls for a revisiting of the code provisions for such sites of seismic prone areas in the region in general.

Simplified Vulnerability Assessment of Historical Churches in Banat Seismic Region, Romania

ABSTRACT Romania, a mid-eastern European country, has a moderate seismicity and a large stock of historical buildings and churches. One of the most important seismic areas of the country is the Banat area, which ranks as the second most seismic area in Romania, with shallow earthquakes of crustal type. Many Orthodox and Catholic churches can be found in the area, the majority of them having a central nave. The churches are built in masonry, with vaults and wooden frameworks, and they present valuable architectural-artistic details, including paintings made by recognized painters. Various forms of structural damage appeared to the historical churches after past earthquakes, depending on the architectural configuration. This paper illustrates a study made on six historic churches in the Banat region, to investigate seismic vulnerability with simplified methods. The study highlights the most vulnerable points of the historic religious structures and the importance of investigating in a quick and simplified way the seismic behavior of such important buildings for the local community. Moreover, the main novelty of the paper is the highlighting of the importance of the sustainability aspect in the process of heritage preservation, as simplified assessment procedures are essential for more resilient risk reduction policies.

DESIGN OF REINFORCED CONCRETE STRUCTURE WITH ORDINARY MOMENT FRAME IN LOW SEISMIC REGION (CASE STUDY: MIDRISE SHOPPING BUILDING IN SINGKAWANG CITY)

This paper focuses on the design of a reinforced concrete structure for an eight-story shopping building in Singkawang City, located in a low to moderate seismic area. The study integrates relevant design considerations in response to the region's seismic conditions. Through structural analysis, the building is categorized as seismic design category B due to moderate seismic risk, leading to the selection of an ordinary moment-resisting frame system compliant with SNI 1726:2019. Emphasis is placed on the importance of using such a system to enhance ductility and prevent brittleness during earthquakes.The research emphasizes the need to design structures capable of withstanding various loads, including dead, superimposed dead, live, wind, and earthquake loads, particularly in West Kalimantan, known for its historically low to moderate seismic activity. Recent earthquake records highlight the necessity of earthquake-resistant design for safety and durability. Structural analysis confirms the building's stability against seismic forces, with a modal participation ratio meeting SNI 1726:2019 requirements, indicating robust response under seismic loads.The study also assesses inter-story drift and P-Delta effects to ensure they meet allowable limits, which is crucial for preserving structural integrity and preventing post-earthquake instability. A detailed reinforcement design following SNI 2847:2019 enhances structural strength and durability, especially when under seismic loading. The foundation design uses tailored hollow spun piles to provide sufficient bearing capacity and stability. This approach demonstrates resilience against potential seismic events in low-to-moderate seismic regions, highlighting the importance of integrating seismic design principles and ductility considerations for effective earthquake hazard mitigation.

The contribution of higher order modes in the dynamic response of slender vertical structures with application to wind turbine towers

Understanding the contribution of the vibration modes to the response of a tower-like structure subjected to base excitations is crucial for a safe and optimized design. The modal contributions to the structural response are generally assessed through modal participation factors and effective masses; however, relatively recent studies pointed out the variability of the modal contributions depending on the response effect (e.g., top displacement, base shear force, base bending moment). The formulation proposed here derives the shear force and the bending moment at the base of a tower-like structure by combining the influence function technique with the quasi-static equivalent forces technique. The resulting formulation of the tower response relies on the concept of modal contribution factors, which provides a straightforward indication of the modal contributions associated with a given response effect. The proposed methodology is applied to the case of wind turbine towers erected on temporary foundations at the port quayside without rotor nacelle assembly to assess the forces on the foundations due to the seismic loading on the towers. This technique may be of great relevance for assessing the tower integrity during installation and for the design of the temporary foundations at the quayside of harbors in seismic area, also considering the quick expansion of the offshore wind energy in countries prone to earthquakes.

Design of Earthquake-Resistant Buildings. New Generation Standards

In modern practice of designing buildings in seismic areas, there is a constant increase in the level of detail of models, however, calculations often ignore the fact that seismic impact is a random process with large variability of parameters, and the interaction of the structure with a nonlinearly deformable foundation is not always taken into account correctly. In addition, when calculating seismic impacts, it is necessary to use modern material models that take into account the nonlinear nature of deformation under cyclic loads. All the factors described above indicate the need to develop complex methods for calculating seismic impacts. The article describes an integrated approach to the calculations of buildings and structures being built in seismic areas, and also provides the main theses for the STO “Construction in seismic areas. Basic provisions”. The section “materials used and research methods” presents the key components of the proposed methodology (nonlinear calculation method, material models and foundation model). The section “research results” presents the main provisions of the proposed two-level calculation. In conclusion, it was concluded that it is necessary to update modern standards and methods of calculation for seismic impacts.

Influence of pulse-like motions and extreme environmental loads on the seismic foundation response of offshore wind turbines on layered liquefiable soils

Monopile foundations are known as the most common foundation solution for offshore wind turbines (OWTs). However, the state of practice for designing monopile foundations in high seismicity areas is still limited. In particular, the impact of soil liquefaction on the seismic soil-foundation-OWT interaction is not yet well understood. In this paper, three-dimensional (3D), fully-coupled, nonlinear finite-element analyses performed in the OpenSees numerical platform were used to evaluate the seismic performance of a series of hypothetical 5 MW OWTs on monopile foundations in layered, liquefiable sites. A suite of earthquake recordings with and without strong velocity pulses (i.e., near fault, pulse-like and ordinary motions, respectively) was used to investigate the impact of ground motion characteristics on the seismic response of the OWT system. Also, the influence of soil-structure interaction and earthquake shaking coupled with extreme environmental loading (i.e., wind and wave loads) on the seismic performance of soil-OWT systems was evaluated. The numerical results showed pile movements induced by extreme climate loading led to a bias in permanent settlement accumulation across the foundation area and accumulation of soil deformations in the proximity of the pile. Ground motion velocity pulses increased the cyclic stress demand in soil and, therefore, the potential for the occurrence of soil liquefaction. A subsequent, limited numerical sensitivity study showed that the foundation rotations of the OWT system were influenced by ground motion characteristics such as polarity and velocity pulses, and the presence of the wind and wave loads. The cumulative absolute velocity (CAV) was identified as the optimum ground motion intensity measure for permanent foundation settlement and tilt as well as for peak transient foundation tilt of the OWT system under extreme environmental loadings. The net outcome of these factors determined the magnitude and orientation of the foundation rotations at the end of shaking. This study highlights the importance of considering the effects of extreme loadings and pulse-like motions in the design and performance of OWT systems.

Shaking table test of a dry-connection fully precast frame structure system

In view of the construction difficulties and ecological environment sensitivity of building construction in extremely cold and high seismic intensity areas, a new type of dry-connection fully precast frame structure system was proposed. The connections of the structure are easy to assemble, which can greatly improve the construction efficiency and provide convenience for the upgrading and replacement of components during service. In order to provide essential insights into the seismic performance of the dry-connection precast structure, a three-story precast frame structure specimen with a scale ratio of 1/2 was designed, constructed, and tested on a shaking table subjected to a series of ground motions with increasing seismic intensities. The connections of the specimen structure include beam-column joint, beam-floor joint and column-foundation joint, precast components were processed in the factory and assembled in the laboratory. The vibration characteristics, damage development, acceleration response and displacement response of the structure were investigated. The experimental results illustrated the excellent seismic performance of the structure with sufficient strength and relatively confined damage. The gradually decreasing frequency and increasing damping ratio were attributed to the slippage and plastic deformation of the connectors and the cracking of beam concrete. And the maximum story drift under rare earthquake of intensity 8 was within the design limit, indicated that the precast frame structure could achieve the performance target of no collapse under severe earthquakes. The data of this test provided support for further study on the design methods and numerical modeling of dry-connection fully precast frame structure systems.

Utilizing ensemble learning in the classifications of ductile and brittle failure modes of UHPC strengthened RC members

This study aims to achieve the swift and precise classification of ductile and brittle failure modes in flexural reinforced concrete (RC) members, specifically those with tension sides strengthened by ultrahigh performance concrete (UHPC). Employing six ensemble learning techniques—Bagging, Random Forest, AdaBoost, Gradient Boosting, XGBoost, and LightGBM—the authors utilize a comprehensive dataset comprising 14 features, which include manually labeled failure modes obtain from load–deflection curves. The model training spans four scenarios, varying in the inclusion or exclusion of features describing the cross-sectional area of RC members and moment resistance. XGBoost emerges as the most effective classifier, achieving an impressive 84% accuracy with high confidence. Additionally, the study employs the Shapley Additive Explanation (SHAP) technique on the best-performing model to illuminate the significance and impacts of various features in UHPC-strengthened flexural members’ failure modes. Notably, moment resistance and UHPC tensile strength surface as the most influential factors in predicting failure modes. Increased rebar yield strength, UHPC compressive strength, UHPC reinforcement ratio, and steel fiber volume in UHPC contribute to enhanced ductility in flexural members, while heightened moment resistance and UHPC layer thickness, along with a robust RC-UHPC interface, tend to induce brittleness. The introduction of such an effective failure modes classification model, coupled with the model’s explainability, instills trust in its predictions and facilitates seamless integration into real-world applications, particularly in seismic areas. The model’s ability to operate without the need for pre-experimental tests marks a significant advancement in the field.

Seismic isolation technology of shallow buried large section utility tunnel with soft soils in seismically vulnerable area

Shallow utility tunnels with exceptionally large cross-sections in weak soil can face significantly more severe seismic risks compared to conventional deep tunnels in seismic hazard areas. This study investigates the seismic response and isolation technologies applied to a large section utility tunnel with 4 compartments in one layer, employing seismic simulations. The engineering context, dynamic motions, and measuring points of the numerical simulation were introduced. Subsequently, the finite element method was employed to explore the seismic behaviors of the large section utility tunnel when subjected to strong earthquake excitations under four conditions. The study explored and comparatively evaluated the seismic isolation effectiveness of three proposed schemes: the grouting scheme, the buffer layer, and the assembly of three-quarters buffer layer, cushion and grouting. The analysis included various indexes such as the deformation, the principal and shear stress, and the safety factor. The finding reveals that the assembly seismic scheme exhibits the most significant seismic effect (95.39%), followed by the buffer layer (38.82%), and the grouting scheme (25.66%). The assembly seismic scheme is recommended for the seismic design in the current large-section utility tunnels. These conclusions provide valuable scientific guidance for the seismic design of large-section utility tunnels, aiding in enhancing earthquake resilience.

Outdated Provisions of the Russian Federation Norms Regulating Construction in Seismic Areas

Outdated Provisions of the Russian Federation Norms Regulating Construction in Seismic Areas

The Effect of Soil-Structure Interaction (SSI) on Structural Stability and Sustainability of RC Structures

The issue of SSI involves how the ground or soil reacts to a building built on top of it. Both the character of the structure and the nature of the soil have an impact on the stresses that exist between them, which in turn affects how the structure and soil beneath it move. The issue is crucial, particularly in earthquake regions. The interaction between soil and structure is an extremely intriguing factor in increasing or reducing structural damage or movement. Structures sitting on deformable soil as opposed to strong soil will experience an increase in static settlement and a decrease in seismic harm. The engineer must take into account that the soil liquefaction problem occurs for soft ground in seismic areas. A reinforced concrete wall-frame dual framework's dynamic reaction to SSI has not been sufficiently studied and is infrequently taken into consideration in engineering practice. The structures’ seismic performance when SSI effects are taken into account is still unknown, and there are still some misconceptions about the SSI idea, especially regarding RC wall-frame dual systems. The simulation study of the soil beneath the foundations significantly impacts the framework's frequency response and dynamic properties. Therefore, the overall significance of SSI in the structural aspect and sustainability aspects will be reviewed in this research.

Comparative analysis of two strengthening solutions for the structural rehabilitation of a historical masonry building

The paper presents a comparative analysis based on the Finite Element Method (FEM) for a masonry building located in Iasi, the North-Eastern side of Romania. This specific region is known to be found in a seismic area having a design peak ground acceleration of 0.25g. The building was assessed as being in the 1st seismic risk class, according to the Romanian norms, with a high probability of collapse in case of future earthquakes. Being a historical monument, the structural strengthening solutions are very limited. The study consists of modal and seismic analyses for the masonry structure. A comparison of the advantages and disadvantages of two approaches of structural rehabilitation solutions is done. The structural strengthening solution “A” consists of the addition of reinforced concrete thin wall elements, while the other - called solution “B” - consists of an interior steel profile skeleton mechanically and chemically connected to the adjacent masonry walls.

Strength and Deformability of Structural Steel for Use in Construction

The purpose of the study is an experimental determination of the stress-related characteristics of the structural steel produced in the Republic of Kazakhstan for use in conventional and earthquake-resistive construction. Since 2015, the construction industry has been using European regulatory documents—Eurocodes—as a statutory framework. In particular, the Eurocode 1993 for steel structures and the Eurocode 1998 for the design of earthquake-resistant structures However, the study of stress-related properties of structural steel using experimental methods of ISO standards has not been performed. Therefore, in the construction industry of the Republic of Kazakhstan, steel-work structures have been used in fairly limited volume since 2015. The experimental studies were conducted on 7 types of structural steel with thicknesses of 8, 10, and 20 mm manufactured by Arcelor Mittal. The yield strength, ultimate tensile strength (breaking stress), and tensile strength at break were studied. The experimental studies were carried out on the basis of ISO standards. In each test run, 5 samples were used. In two series, 20 samples each were tested, which made it possible to estimate the yield strength and strength distribution functions. The correlation relationships between Brinell hardness and yield and strength limits have been studied. As a result of experimental studies, it was found that the strength and deformability parameters fully comply with the requirements of Eurocode 1993. Based on the application of the Student's test, it is revealed that the distribution functions of yield strength and resistance correspond to the normal law (Gaussian function). The calculation of a three-story, two-span residential building with box section columns for construction in an area with a seismicity of 8 points is performed by the finite element method. The work results will significantly increase the scope of Kazakhstani structural steel use in seismic and conventional areas of the Republic of Kazakhstan. Doi: 10.28991/CEJ-2024-010-03-09 Full Text: PDF

Landslide spatial prediction using cluster analysis

Temporal clustering is an intrinsic nature of landslide occurrences, therefore it should be considered in data-driven landslide spatial prediction (i.e., susceptibility assessment). However, it remains problematic regarding how to determine landslide temporal clusters and how to integrate susceptibility maps derived from different landslide temporal clusters. In this paper, a general framework of landslide spatial prediction model considering the temporal clustering of landslides is proposed. This novel framework first assesses landslide susceptibility separately based on each landslide temporal cluster identified by spatiotemporal clustering analysis and then integrates separate assessments by weighted averaging. In a case study, this general framework is implemented using the stacking network landslide susceptibility assessment method and used in the landslide spatial prediction of the Sanming City and Wenchuan seismic areas. The results show that the proposed framework outperformed traditional susceptibility models that do not consider landslide temporal clustering, and the integration of susceptibility models based on all landslide temporal clusters will promote the performance of landslide spatial prediction because levels of knowledge in long-term spatiotemporal landslide activities are considered. This novel general framework highlights the benefit of considering landslide temporal clustering in landslide spatial prediction and can provide better support for landslide risk management.

Time history comparative analyses of a thin-walled cold-formed steel structure considering P-D effect

The paper presents a comparative time history analysis based on the 1D-beam Finite Element Method (FEM) for a thin-walled cold-formed steel structure previously investigated both theoretically and experimentally. The recent earthquake which occurred in Turkey with 7.8Mw and a Peak Ground Acceleration (PGA) of almost 0.5g showed numerous collapses of different types of buildings. Romania has an active seismic area located in the Vrancea region where, in 1977 a 7.5Mw earthquake also occurred. In this context, this paper presents a comparative analysis with time history accelerograms of the recorded earthquake in North – South and East - West directions. The structural model was analyzed in Robot Structural Analysis software in two scenarios of the time history accelerograms considering also the P-Δ effect. The finite elements of the structure were defined as 1-D beam elements with hinged joints and limited axial stiffness previously obtained in past studies. The results showed a substantial increase in terms of displacements and stresses.

Seismic design and performance assessment of a retrofitted building with tuned viscous mass dampers (TVMD)

Vibration control technologies have been widely implemented for the seismic retrofitting of buildings in high seismic regions. Among various vibration control devices, the tuned viscous mass damper (TVMD) has proven effective in mitigating both lateral inter-story drifts and floor accelerations. This paper presents the seismic design and performance assessment of a retrofitted structure located in a highly seismic area. The existing masonry building is being retrofitted into a steel frame-jacketed masonry wall interacting structural system installed with TVMDs. A simplified iterative design process is proposed for the tuning design of TVMDs used in the retrofitted structure, which is based on the fixed-point method. The seismic responses of the buildings are calculated using non-linear dynamic analysis in OpenSees. Applying the FEMA P-58 approach, the seismic performance of the buildings as measured by the repair cost and repair time is evaluated. The findings reveal that the majority of the structural damage is focused within the masonry walls, coupling beams, and non-structural components. Use of TVMDs results in reduced maximum inter-story drifts that when subjected to very rare earthquake (VRE) shaking are up to approximately 40% lower in both transverse and longitudinal directions compared with the uncontrolled structure. Owing to the effective control of seismic damage to both structural and non-structural components, the TVMD-equipped structure achieves a 42% reduction in median repair cost and a 46% reduction in median repair time at VRE compared with the uncontrolled building. The seismic performance assessment results also illustrate the advantages of TVMD control compared with conventional viscous dampers.

Seismic Risk Analysis of Government Buildings in the City of Tembilahan using FEMA P-58

Research in estimating losses and harm experienced by structures in the high seismic zone had been conducted in previous studies. Yet there is limited study carried out in low-moderate seismic areas. Therefore, an accurate method for calculating losses incurred due to earthquake events is needed in assessing the performance of building structures. This study aims to analyze the seismic risk of government buildings in Indragiri Hilir Regency Riau Province according to FEMA P-58. Seismic risk analysis was carried out on four reinforced concrete buildings. The four buildings reviewed in this study were categorized as low-rise buildings (Immigration Office) and medium-rise buildings (Regent's Office, Puri Husada Hospital, and Rusunawa). The buildings’ location according to SNI 1726-2019 was categorized as soft soil class. The results showed that the Immigration Office, Regent's Office, Puri Husada Hospital and Rusunawa were in a safe state. This is drawn by the value of the collapse probability in the current search condition, which is lower than the value of the collapse probability in the upper bound condition. Regent's Office and Rusunawa were the most vulnerable buildings where the value of the mean loss probability was the highest, namely 23.2%.

Shaking Table Tests of Chuandou-Type Timber Structure Building for Seismic Fortification High-Intensity Area

ABSTRACT This study investigated the seismic performance of Chuandou-type timber structure buildings intended for seismic fortification in a high-intensity zone. An earthquake simulation shaking-table test was conducted on a two-layer Chuandou-type structure constructed in Yunnan, China. The El Centro, Kobe, and artificial waves were used as input excitations. The natural frequency, stiffness, acceleration response, and displacement response to the earthquake events were determined. The experimental results indicate that as the acceleration intensity of the earthquake increases, the natural frequency and stiffness of the model structure decrease. The acceleration amplification coefficient of each layer varied from 0.47 to 1.95. The energy dissipation of column foot slip, mortise-tenon joint friction and extrusion were visible, and the dynamic amplification coefficient of the first layer was less than one except for Kobe wave excitation. When the input peak acceleration is 0.63 or 0.95 g, the model shocks violently and exhibits a spectacular whiplash effect, with the model’s maximum inter-story drifts being 1/23 and 1/26, respectively. However, the model did not tilt or collapse, which displays that the Chuandou-type structure had an overall good deformation and self-centering ability. Additionally, it satisfies the standards of the Chinese Code for Seismic Design of Buildings (GB2011–2010).

Deep learning forecasting of large induced earthquakes via precursory signals

Precursory phenomena to earthquakes have always attracted researchers’ attention. Among the most investigated precursors, foreshocks play a key role. However, their prompt identification with respect to background seismicity still remains an issue. The task is worsened when dealing with low-magnitude earthquakes. Despite that, seismology and, in particular real-time seismology, can nowadays benefit from the use of Artificial Intelligence (AI) to face the challenge of effective precursory signals discrimination. Here, we propose a deep learning method named PreD-Net (precursor detection network) to address precursory signal identification of induced earthquakes. PreD-Net has been trained on data related to three different induced seismicity areas, namely The Geysers, located in California, USA, Cooper Basin, Australia, Hengill in Iceland. The network shows a suitable model generalization, providing considerable results on samples that were not used during the network training phase of all the sites. Tests on related samples of induced large events, with the addition of data collected from the Basel catalogue, Switzerland, assess the possibility of building a real-time warning strategy to be used to avoid adverse consequences during field operations.