Seismic Vulnerability Research Articles

Seismic Fragility Analysis of Offshore Wind Turbines Considering Site-Specific Ground Responses

This study investigated the seismic performance and assessed the seismic fragility of an existing pentapod suction-bucket-supported offshore wind turbine, focusing on the amplification of earthquake ground motions. A simplified suction bucket–soil interaction model with nonlinear spring elements was employed within a finite element framework, linking the suction bucket and soil to hypothetical points on the OWT structures at the mudline. Unlike conventional approaches using bedrock earthquake records, this study utilized free-field surface motions as input, derived from bedrock ground motions through one-dimensional wave theory propagation to estimate soil-layer-induced amplification effects. The validity of the simplified model was confirmed, enabling effective assessment of seismic vulnerability through fragility curves. These curves revealed that the amplification effect increases the vulnerability of the OWT system, raising the probability of exceeding damage limit states such as horizontal displacement of the tower top, tower stress, and horizontal displacement at the mudline during small to moderate earthquakes, while decreasing this likelihood during strong earthquakes. Comparisons between the Full Model and the simplified Spring Model reveal that the simplified model reduces computational time by approximately 75%, with similar seismic response accuracy, making it a valuable tool for rapid seismic assessments. This research contributes to enhancing seismic design practices for suction-bucket-supported offshore wind turbines by employing a minimalist finite element model approach.

Machine learning (ML) algorithms for seismic vulnerability assessment of school buildings in high-intensity seismic zones

Ensuring seismic resilience of school buildings is crucial for safeguarding their occupants during earthquakes. This paper focuses on assessing the seismic vulnerability of school buildings constructed in the Kashmir region of Pakistan after the 2005 earthquake, which claimed the lives of 19,000 school-going children. It explores the feasibility of utilizing machine learning (ML) algorithms for enhanced rapid screening of schools to establish fragility information. The study is based on data collected in the Kashmir region and focuses on assessing representative reinforced concrete (RC) and unreinforced masonry (URM) school buildings. To determine structural fragility curves, Incremental Dynamic Analyses (IDA) are performed, simulating fifteen historical earthquakes. Four different ML models are investigated to predict fragility curves, including Random Forest (RF), Artificial Neural Networks (ANNs), Extreme Gradient Boosting (XGBoost), and Extremely Randomized Tree Regressor (ERTR). The performance of the algorithms is compared using performance metrics such as precision, accuracy, and f1 score. The study identified XGBoost and RF as the highest performing algorithms, achieving highly satisfactory accuracy with the correlation coefficients of 0.91 and 0.81 for RC schools, and 0.88 and 0.83 for URM schools during testing phases. Alternatively, ERTR’s performance could not justify its use for structural seismic vulnerability assessments. This highlights the significant potential of using ML algorithms for automated seismic vulnerability evaluation of buildings, greatly reducing the overall computational burden while maintaining high accuracy and reliability.

Simplified method for seismic vulnerability of plan irregular RC buildings using degree of irregularity

Irregular buildings are more vulnerable to seismic loading, depending on their degree of irregularity. The degree of irregularity in vertically irregular buildings and its correlation to seismic vulnerability (SV) have been quantified in previous studies. However, these studies on plan irregular buildings were focused on only evaluating seismic performance. A simplified method, based on the degree of irregularity, is proposed to identify the SV of plan irregular reinforced concrete (PIRC) buildings. The different types of plan irregularities considered were diaphragm discontinuity, re-entrant corners, non-parallel systems and torsional irregularity. For each type of plan irregularity, numerical models were developed with varying degrees of irregularity. The numerical models were subjected to incremental dynamic analysis and the maximum interstorey drift was recorded to develop fragility curves. The proposed simplified method effectively identified the SV of the PIRC buildings based on their degree of plan irregularity. The method can help to identify the most vulnerable PIRC buildings at the initial stage of large-scale seismic simulations, such as integrated earthquake simulations of urban areas. It can thus be used as a filtering method to select the most vulnerable PIRC buildings that need detailed seismic analyses.

Earthquake risk assessment for Kuwait City, Kuwait

Estimating the expected losses from a seismic disaster, whether economic or human is considered one of the most important priorities for urban development in countries, especially those with continually expanding urban areas, high-rise buildings, and skyscraper construction as is the case in Kuwait City. It is necessary to conduct an earthquake risk assessment study due to Kuwait’s geographical location which makes it close to the most important global seismic belt, the Zagros Seismic Belt, and its proximity to local seismic sources. To conduct such a study, three inputs including seismic hazard, exposure, and vulnerability modules were incorporated, considering the inputs’ uncertainty. To assess the seismic hazard module, a unified earthquake catalog was compiled, a seismotectonic model of 27 seismic sources was designed, the recurrence parameters of seismicity and the strongest predictable earthquake were calculated for each source, and the unified hazard spectrums were obtained. Earthquake scenarios were generated to create a seismic hazard module. The exposure module is performed using data from the Kuwaiti Public Authority for Civil Information including coordinates of 33,066 facilities and buildings, area, height, shape, and type of buildings, the materials used in their construction, their occupancy, and replacement cost. The vulnerability module was implemented using mean damage ratio curves by choosing the most appropriate equations that describe the condition of buildings in Kuwait, the vast majority of which are modern multi-story concrete buildings. The final results including the economic losses of the exposures were calculated using probabilistic metrics (predicted annual losses, loss exceedance curve, and probable maximum loss). The results showed that the annual average loss is $12,793,319.52 and that seismic source No.27 to the north of Kuwait has a significant value to the losses, but the frequent occurrence of losses from seismic source No.15 to the east of Kuwait, in the Zagros region, gave the most danger to Kuwait. Seismic risk results can be used to create emergency response scenarios and risk mitigation strategies.

Intelligent prediction and evaluation models for the seismic risk and vulnerability of reinforced concrete girder bridges in large-scale zones

Intelligent prediction and evaluation models for the seismic risk and vulnerability of reinforced concrete girder bridges in large-scale zones

Impact of soil conditions and seismic codes on collapsed structures during the 2023 Kahramanmaraş earthquakes: An in-depth study of 400 reinforced concrete buildings

Türkiye has a history full of devastating earthquakes from past to present. The February 6, 2023, earthquakes in Kahramanmaraş Pazarcık and Elbistan, with magnitudes of Mw 7.7 and Mw 7.6, were among the most destructive in recent history, impacting 11 provinces and causing severe structural damage, especially in regions close to the fault line. Within the scope of this study, the 400 reinforced concrete buildings that collapsed due to the 2023 Kahramanmaraş earthquakes in the provinces of Kahramanmaraş, Adıyaman, Hatay, Gaziantep were examined in terms of seismic codes and soil conditions. The evolution of the Codes on Buildings to be Built in Disaster Areas (1975 and 1997-8), Code on Buildings to be Built in Earthquake Zones (2007) to which the relevant reinforced concrete buildings are subject, and Türkiye Building Earthquake Code (2018) were discussed. The differences between the local soil conditions in these codes were revealed and it was evaluated how these local soil properties affect the seismic vulnerability of buildings. This study's findings highlight the critical role of the soil conditions on seismic vulnerability of buildings in earthquake-prone regions. They also offer valuable insights into developing strategies to enhance the structural resilience of similar buildings in other earthquake regions against future seismic events.

Seismic resilience of deteriorating bridges under changing climatic conditions

This study underscores the critical need to integrate changing climatic conditions into corrosion models for civil engineering infrastructures, particularly highway bridges, given the potential reduction in structural performance post-seismic events. The paper introduces a novel framework for assessing the seismic resilience of deteriorated highway bridges in the context of changing climatic conditions. The framework is demonstrated on a non-seismically designed simply supported highway bridge situated near the sea in a seismically active region of Gujarat, India. An improved corrosion deterioration model is used that considers the impact of climate change and non-uniform pitting corrosion for evaluating the deterioration of RC bridge components. A detailed three-dimensional finite-element model of the case-study bridge is developed that can accurately simulate various failure modes of corroding bridge piers. Time-varying seismic fragility curves are developed using damage limit states and probabilistic seismic demand models while considering the influence of climate change. Bridge seismic resilience is estimated by aggregating the seismic vulnerability, losses, and recovery functions. Results show that incorporation of changing climatic factors will considerably reduce the seismic resilience of the 75-year corroded bridge up to 56 %. Finally, a comparison of seismic fragility and resilience is carried out using the proposed and conventional corrosion deterioration model to evaluate the significance of considering the effects of climate change in the seismic resilience assessment framework.

Evaluation of the Seismic Vulnerability of Typical Buildings in the Urban Area of Cuenca by Me ans of Simulation and Multivariate Techniques

Evaluation of the Seismic Vulnerability of Typical Buildings in the Urban Area of Cuenca by Me ans of Simulation and Multivariate Techniques

Earthquake risks assessment and urban vulnerability: Case of Nador city, northeast Morocco

This study introduces an innovative approach to assessing seismic risks and urban vulnerabilities in Nador, a coastal city in northeastern Morocco at the convergence of the African and Eurasian tectonic plates. By integrating advanced spatial datasets, including Landsat 8–9 OLI imagery, Digital Elevation Models (DEM), and seismic intensity metrics, the research develops a robust urban vulnerability index model. This model incorporates urban land cover dynamics, topography, and seismic activity to identify high-risk zones. The application of Landsat 8–9 OLI data enables precise monitoring of urban expansion and environmental changes, while DEM analysis reveals critical topographical factors, such as slope instability, contributing to landslide susceptibility. Seismic intensity metrics further enhance the model by quantifying earthquake risk based on historical event frequency and magnitude. The calculation based on higher density in urban areas, allowing for a more accurate representation of seismic vulnerability in densely populated areas. The modeling of seismic intensity reveals that the most susceptible impact area is located in the southern part of Nador, where approximately 50% of the urban surface covering 1780.5 hectares is at significant risk of earthquake disaster due to vulnerable geological formations, such as unconsolidated sediments. While the findings provide valuable insights into urban vulnerabilities, some uncertainties remain, particularly due to the reliance on historical seismic data and the resolution of spatial datasets, which may limit the precision of risk estimations in less densely populated areas. Additionally, future urban expansion and environmental changes could alter vulnerability patterns, underscoring the need for continuous monitoring and model refinement. Nonetheless, this research offers actionable recommendations for local policymakers to enhance urban planning, enforce earthquake-resistant building codes, and establish early warning systems. The methodology also contributes to the global discourse on urban resilience in seismically active regions, offering a transferable framework for assessing vulnerability in other coastal cities with similar tectonic risks.

Seismic Vulnerability Index Mapping Based on PGA, GSS, and MMI Values in Pasar Ujung Kepahiang Village

Pasar Ujung Village is located in Kepahiang District, which has the highest growth rate and population compared to other sub-districts in Kepahiang Regency, with a growth rate of 1.63% and a population of 53,066 thousand people. As one of the efforts to minimize the occurrence of damage due to earthquake disasters in Pasar Ujung Village, Kepahiang, it is necessary to map the seismic vulnerability index using the microtremor method. The research was conducted in Pasar Ujung Village, Kepahiang. Measurement points were placed at 28 points with a distance of approximately 200 m between points. Primary data used in this study came from microtremor surveys with A0 and f0 values. The results of the study are also included in the high-risk category for the social impact of earthquake disasters with an MMI value of more than 7. Based on the PGA map, it shows that the research location is quite prone to damage due to earthquakes, with a PGA value of > 564gal. Based on the PGA value obtained, the value is classified as instrumental intensity scale VI-VIII with shaking strength in the strong to very strong category. The magnitude of the earthquake, the depth of the source, and the distance of the earthquake source from the research location also contribute. The thickness of the surface sediment layer can be a consideration for people who will carry out development.

Site response measurements and implications for soil deformation using geophysical and geotechnical characterization of Djen-Djen Port, Jijel, Northeast Algeria

This paper describes the concept used to develop a methodology and an integrated approach based on the ambient vibration horizontal-to-vertical spectral ratio (HVSR) combined with geotechnical analysis for assessing soil deformations observed in Djen-Djen port located near Jijel-City (north-east Algeria).140 ambient vibrations recording were carried out to generate a spatial distribution map of the HVSR curves, seismic vulnerability index (Kg) and the ground shear strain GSS-(γ) value distribution maps. The spatial distribution of Kg and GSS-(γ) values estimated correlates well with both the geological units and soil deformations in the study area. In addition, the mapping of the spatial distribution of the HVSR curves delineates six distinct zones, thus reflecting the sensitivity of the HVSR peak amplification factor with the compactness and technical properties of the soil.The qualitative and quantitative analysis developed in this study made it possible to characterize the embankments, settlement, and liquefaction observed at the port of Djen-Djen in eastern Algeria. This paper shows that the HVSR method is a useful and promising technique for studying soil settlement and liquefaction. The Kg and GSS maps can be used as a guide to implementation of geotechnical tests before any conventional study and as well to identify sites that are vulnerable to deformation for seismic hazard reduction.

Mathematical modelling for seismic affected zoning of tunnel cavity section under SH wave incidence and shaking table verification

Tunnel portals are particularly vulnerable during seismic events due to the influence of adjacent slope geometry and fractured rock formations. This study evaluates the seismic response of tunnel portals and determines an appropriate fortification range. Ray theory is employed to calculate the displacement field of a single-sided slope subjected to incident SH waves, while the tunnel entrance is modeled as an elastic foundation beam. An analytical expression for hoop strain is derived, accounting for the interaction between the tunnel and the surrounding rock, as well as the attenuation of seismic waves. A parametric analysis is also performed to examine the impact of slope angle, seismic wavelength, frequency, and foundation stiffness on the tunnel response. Shaking table tests are conducted to validate the theoretical results and reveal failure patterns in both the slope and tunnel. The findings show that the spandrel and arch foot exhibit the highest hoop strain responses, identifying these positions as critical points of seismic vulnerability. The seismic-affected zones of the tunnel portal are classified into three distinct regions based on the distribution of peak hoop strain. The recommended fortification range for the tunnel portal extends up to 7.5 times the tunnel span, effectively encompassing the areas of peak strain to mitigate potential damage.

Seismic Design of Underground Structures’ Vulnerability – Review.

This article examines the vulnerability of underground structures to seismic activity, with a particular focus on design and mitigation strategies. Underground buildings are essential to the development of modern infrastructure and must include tunnels, subway stations, and storage facilities. Because of its deep location, seismic design and earthquake performance are both more challenging. In this study of seismic susceptibility, topics such as ground motion characterization, soil-structure interaction, structural reaction, and failure mechanisms specific to underground structures are discussed. According to the paper, their susceptibility can be affected by geotechnical conditions, the kind of structures they have, and the construction methods that are used. The seismic stability design and analysis process involves measuring the dynamic response of subsurface structures to seismic loads. The goal is to keep earthquake and seismic forces from toppling structures in any way that is possible. Advanced analytical and numerical approaches are used in seismic stability design. Some examples of these methods are finite element analysis (FEA), discrete element modeling (DEM), and the boundary element method (BEM). In addition to that, it investigates contemporary methodologies for assessing seismic vulnerability as well as international design standards. In addition, seismic retrofitting and design advances for underground structures are analyzed and discussed in this paper. This document compiles and evaluates previous research to gain an understanding of the seismic susceptibility of subsurface structures and to promote more seismic engineering research on this extremely important topic.

Does seismic isolation reduce the seismic vulnerability and the variability of the inelastic seismic response? Large-scale experimental investigation

AbstractThis paper focuses on the large-scale experimental investigation of the seismic vulnerability and the variability of the inelastic seismic response of seismically isolated structures in comparison to conventional, fixed-based structures. The experimental setup comprises a steel structure consisting of two steel columns and a steel mass on top. The structure is seismically isolated using four friction pendulum bearings and subjected to an ensemble of strong recorded earthquake ground motion excitations using the shaking table of ETH laboratory. A mechanical clevis connection consisting of two hinges and two replaceable steel coupons is designed and constructed to facilitate the investigation of the seismic inelastic behavior of the structure for the selected ground motion record ensemble through the replacement of the damaged coupons after each shaking table excitation. Within this frame, the mechanical clevis connection presented in this study facilitates the parametric and experimental investigation of the seismic, inelastic behaviour of a wide range of structures and the experimental determination of their seismic fragility curves. The seismic vulnerability and the variability of the seismic response of the seismically isolated and the corresponding fixed-based structure are compared for three seismic hazard levels. The comparison of the response of the two structures demonstrates experimentally the ability of seismic isolation to reduce the seismic vulnerability and the variability of the seismic response of structures subjected to strong earthquake ground motion excitation, thus leading to the design of structures of higher performance, predictability and reliability in their response, even for extreme earthquake events.

Finite element modeling of the influence of FRP techniques on the seismic behavior of an arch stone bridge of historical interest

In this paper, a masonry bridge is simulated in order to assess both its structural and seismic vulnerability. Therefore, the present study aimed to approximately analyze the real behavior of Mikron Bridge structure. The modeling was conducted by combining the finite element method (FEM) and discrete element method (DEM) using the ABAQUS® software. By comparing the results of numerical and experimental modal analyses, the accuracy of simulation was verified. To simulate the seismic behavior of the Mikron Bridge, the component of Erzincan earthquake occurred in 1992 was used. The results extracted from the seismic analysis show that some parts of the bridge structure are damaged but not destroyed.

Finite element modeling of the influence of FRP techniques on the seismic behavior of an arch stone bridge of historical interest

In this paper, a masonry bridge is simulated in order to assess both its structural and seismic vulnerability. Therefore, the present study aimed to approximately analyze the real behavior of Mikron Bridge structure. The modeling was conducted by combining the finite element method (FEM) and discrete element method (DEM) using the ABAQUS® software. By comparing the results of numerical and experimental modal analyses, the accuracy of simulation was verified. To simulate the seismic behavior of the Mikron Bridge, the component of Erzincan earthquake occurred in 1992 was used. The results extracted from the seismic analysis show that some parts of the bridge structure are damaged but not destroyed.

Mainshock-aftershock building fragility methodology for community resilience modeling

This study introduces a methodology for developing fragility functions that enable the assessment of seismic vulnerability and resilience at the community level for buildings subjected to mainshock-aftershock sequences. To date, this has been assessed at a single structural level or through statistical combinatorial approaches. This paper provides a solution for a suite of archetypes including ductile and non-ductile reinforced concrete frames as well as woodframe buildings. The findings highlight the central role of aftershocks in exacerbating damage states and increasing economic losses, emphasizing the importance of including these events in accurate assessments of community resilience and seismic risk. The suite of archetypes is applied at the community level using the IN-CORE platform to quantify the effect of incorporating aftershocks into community-level seismic vulnerability analyses. The ability to accurately include the effect of aftershocks within community-level risk and resilience analyses will be key to planning for earthquakes.

Test-Based Assessment of the Seismic Response of Bracing Systems for Concealed Grid Suspended Ceilings

ABSTRACT Despite not directly contributing to a structure’s load-bearing capacity, non-structural elements like partitions, cladding, ceilings, floor finishes, and facades play a pivotal role in the overall building design and occupant safety. Their susceptibility to damage during seismic events, however, can lead to substantial economic losses, business interruptions, and potential risks to occupants. Focusing on concealed grid suspended ceiling systems, this study focuses on enhancing their seismic resilience introducing and experimentally evaluating two innovative bracing systems (Typology N and Typology W) that utilize steel members, already used in non-seismic application, as braces. Unlike prior research using shake tables, this study employs a specially designed set-up on a universal testing machine, offering a cost-effective and efficient approach for cyclic testing and considering the spatial variability of seismic loads. As a complementary task, component-level tests were conducted on the compressed strut to extend the results for suspended ceiling systems having suspension height up to 2 meters. The results show that Typology N performs better than Typology W, with 1.7 times greater resistance and 2.5 times greater stiffness on average, demonstrating the importance of considering different directions of horizontal seismic loading in the performance assessment. The study provides valuable insights, including design resistance values and a step-by-step procedure for determining the maximum ceiling area that a single bracing system can cover, aiding in optimizing bracing system selection and mitigating seismic vulnerability in concealed grid suspended ceilings for seismic-prone regions.

Optimization of a novel lateral energy dissipation system for cable-stayed bridge with short piers based on seismic vulnerability analysis

Cable-stayed bridges with short piers are susceptible to becoming the structural weak link in seismic resistance during strong earthquakes. Traditional lateral restraint systems, such as fixed and sliding bearing systems, may impose substantial lateral forces and displacement demands, affecting the entire bridge's seismic safety. A butterfly-shaped steel plate damper has been developed and integrated into a lateral energy dissipation system along with elastoplastic cables to address this. Given the significant computational challenges and the complexity of identifying the optimal parameters for the energy dissipation system, this paper combines the probabilistic seismic demand model (PSDM) with the response surface method (RSM) to propose the seismic vulnerability fitting optimization method (SVFOM). Based on SVFOM, utilizing a central composite design (CCD), 17 analysis scenarios that account for the parameter variations of the lateral energy dissipation system are established. By developing response surface functions for bearing damage (ys) and pier damage (yp) through the seismic response fitting of the structure across all scenarios, we determined the optimal parameters for the lateral energy dissipation system to minimize damage to both bearings and piers. The finite element model validation analysis, which demonstrated significant reductions in pier displacement and the probability of bearing damage, confirms the effectiveness of the SVFOM. Optimized parameters showed that the new lateral energy dissipation system can significantly enhance the lateral seismic performance of cable-stayed bridges with short piers. Compared to scenarios without energy dissipation and with lateral sliding bearings, they demonstrated that this optimized system reduces the relative displacement of the piers and girders by 56 % and the probability of complete bearing failure by 87 % while maintaining pier damage within acceptable limits. This optimized system offers a valuable reference for the seismic design of similar bridge structures.

Analysis of Earthquake Vulnerability of The Demak Coastal Area based on the HVSR (Horizontal To Vertical Spectral Ratio) Method

<p>Most of the Demak Coastal area, especially on the north coast, has a subsurface structure which is quite thick sediment. The impact of an earthquake will cause damage to subsurface structures and buildings above it, so a method is needed that can determine earthquake vulnerability in an area to take mitigation steps. This research aims to analyze vulnerability to earthquakes based on natural frequency (fo), amplification (Ao) and seismic vulnerability index (SVI). The research was carried out by measuring the microseismic signal response at 89 locations using a 3-component seismograph and data logger. The research results showed that the dominant frequency varied from 0.26 – 5.26 Hz, the amplification factor varied from 0.51 – 3.56 and the seismic susceptibility index varied from 0.14-14.77 micro cm<sup>2</sup>/s. The study area was classified into low SVI (SVI < 5), medium SVI (5 < SVI < 10), and high SVI (SVI > 10). The potential earthquake hazard described by SVI with a value range of 10 < SVI (high classification) is found at observation station 60 (Bedono Hamlet) and observation station 70 (Karangwaru Hamlet Cemetery)</p>