Seismic Assessment Research Articles

Uncertainty effect on seismic capacity assessment in the out-of-plane failure mechanisms of masonry structures by probabilistic and non-probabilistic approaches

The present paper aims to provide a contribution in the study of the seismic analysis of existing masonry structures in presence of uncertain parameters described by following both probabilistic and non-probabilistic models. By posing the attention on the local out-of-plane failure mechanisms, the non-deterministic analysis is conducted on the kinematic chains of masonry portions by first applying the upper bound theorem of the limit analysis providing the expressions of the load multiplier parameter and in turn the acceleration capacity of the local mechanism with an explicit dependence on the uncertainties. Specifically, two particular local failure mechanisms commonly observed in post-earthquake scenarios, namely the vertical bending mechanism and the corner overturning mechanism, are analyzed considering the masonry-specific weight, the position of the cylindrical hinge and the cracks lines inclination as uncertain variables. In the framework of a stochastic approach, the uncertain parameters are described by random variables with assigned probability density functions (PDFs) and the Probability Transformation Method is applied to return the PDFs of the seismic response functions. In a non-probabilistic setting, the same parameters are defined as uncertain-but-bounded variables in terms of lower and upper bounds and a global optimization technique straightforwardly allows to estimate the intervals for the seismic response functions. Taking full advantage of the close link between the two proposed approaches, the numerical investigations allow to better understand whether the interval analysis is adequate for a reliable assessment of the seismic acceleration capacity or a stochastic analysis is preferable and therefore a more in-depth experimental campaign is required to fully describe the uncertain input parameters as random variables. Moreover, results on the separate and combined effect of the uncertain parameters on the seismic response functions provide other useful information to predict the masonry capacity and preserve integrity.

Operational modal analysis, seismic vulnerability assessment and retrofit of a degraded RC bell tower

This paper presents damage assessment through Operational Modal Analysis (OMA) and Finite Element (FE) model updating of the bell tower of the church of Castro in Bergamo, Italy. The tower is a 39 m high reinforced concrete structure with hollow cross-section and double-curved shape. The research was dictated by the need to identify the actual damage state of the structure, which was found through visual inspections. Piezoelectric accelerometers were used to record the ambient vibrations in subsequent test setups, using the roving technique for system identification. A detailed FE model was created with shell elements and calibrated to match the system identification results. A simplified beam model was then developed based on the modal analysis results of the detailed model. A sensitivity analysis was performed to identify the most influential model parameters on the modal characteristics of the system. Subsequently, the optimal values of these parameters were determined by an optimisation procedure carried out using a typical global optimization algorithm. The updating results allowed assessment of the actual condition of the bell tower and its seismic vulnerability. Finally, a seismic strengthening solution was recommended.

Seismic risk assessment for the downtown of the city of Blida, Algeria

Blida (Algeria) is characterized by a high level of seismic exposure and vulnerability due to its dense population and the presence of aging buildings. The historical earthquake that occurred in 1825, with a moment magnitude (Mw7.1), underscored the urgent need for a thorough assessment of seismic risk in the area. Here, an extensive study conducted in downtown of the city of Blida to evaluate seismic risk and its consequences is presented. Geounits 141 and 148 emerged as the most severely affected in all the simulated earthquake scenarios indicating severe damage and casualties mainly for closest earthquakes (Blida and Bounaian, both with moment magnitude Mw7.1) but also for furthest earthquakes as Mouzaia El Affroun (Mw6.6), and Hammam Melouane (Mw6.5). The sensitivity analysis demonstrated the importance of the selection of the performance point computation method (improved displacement coefficient method -IDCM, modified capacity spectrum-MADRS, and nonlinear analysis method-N2) and the choice of the ground motion prediction equation. IDCM results are less influenced by the choice of the GMPE, but they provide higher damage results expressed as a mean damage ratio. Moreover, the study estimated potential human impacts in the Blida region, highlighting varying levels of impact on different geounits under different earthquake scenarios. The study's primary findings from seismic risk assessments in the studied region highlight its high susceptibility to earthquakes and can be summarized as follows: The mean damage ratio will be 52.6% ± 1.4%, 50.9% ± 1.6%; 31.8% ± 3.4% and 21.4% ± 3.1% for the Blida, Bounaian, Mouzaia El Affroun and Hammam Melouane earthquakes respectively.

Consequences of consequence models: The impact of economies of scale on seismic loss estimates

The detailed evaluation of expected losses and damage experienced by structural and nonstructural components is a fundamental part of performance-based seismic design and assessment. The FEMA P-58 methodology represents the state of the art in this area. Increasing interest in improving structural performance and community resilience has led to widespread adoption of this methodology and the library of component models published with it. This study focuses on the modeling of economies of scale for repair cost calculation and specifically highlights the lack of a definition for aggregate damage, a quantity with considerable influence on the component repair costs. The article illustrates the highly variable and often substantial impact of damage aggregation that can alter total repair costs by more than 25%. Four so-called edge cases representing different damage aggregation methods are introduced to investigate which components experience large differences in their repair costs and under what circumstances. A three-step evaluation strategy is proposed that allows engineers to quickly evaluate the potential impact of damage aggregation on a specific performance assessment. This helps users of currently available assessment tools to recognize and communicate this uncertainty even when the tools they use only support one particular damage aggregation method. A case study of a 9-story building illustrates the proposed strategy and the impact of this ambiguity on the performance of a realistic structure. The article concludes with concrete recommendations toward the development of a more sophisticated model for repair consequence calculation.

A Deep Learning Method for Building Extraction from Remote Sensing Images by Fuzing Local and Global Features

As important disaster-bearing bodies, buildings are the focus of attention in seismic disaster risk assessment and emergency rescue. It is of great practical significance to extract buildings quickly and accurately with complex textures and variable scales and shapes from high-resolution remote sensing images. We proposed an improved TransUnet model based on multiscale grouped convolution and attention named MATUnet to retain more local detail features and enhance the representation ability of global features, while reducing the network parameters. We designed the multiscale grouped convolutional feature extraction module with attention (GAM) to enhance the representation of detailed features. The convolutional positional encoding module (PEG) was added to redetermine the number of transformer, it solved the problem of local feature information loss and the difficulty of convergence of the network. The channel attention module (CAM) of the decoder enhanced the salient information of the features and solved the problem of information redundancy after feature fusion. We experimented through MATUnet on the WHU building dataset and Massachusetts dataset. MATUnet achieved the best IOU results of 92.14% and 83.22%, respectively, and achieved better than the other generalized and state-of-the-art networks under the same conditions. We also have achieved good segmentation results on the GF2 Xichang building dataset.

Seismic fragility and resilience assessment of shallowly buried large-section underground civil defense structure in soft soils: Framework and application

The assessment of fragility of underground civil defense structures is of paramount importance in ensuring their functionality and enhancing safety in seismic-prone regions. This study aims to explore the evolution law of seismic fragility for a shallowly buried large-section underground civil defense structure in soft soils, employing advanced data-based approaches. To achieve this, a two-dimensional (2D) nonlinear finite element model of the soil-civil defense structure interaction system was established, integrating data-based parameters and insights. Subsequently, the cloud and incremental dynamical analysis (IDA) methods were employed to develop a probabilistic seismic demand model for the shallowly buried large-section civil defense structure, effectively utilizing data-based approaches to account for the nonlinear characteristics of the soil and the uncertainties of input seismic motions. Based on this model, seismic fragility curves were generated using different seismic intensity measures (IMs), and the evaluation of IMs was carried out by the efficiency and practicality analyses of IMs. These curves were then systematically compared with other existing empirical and analytical fragility curves. The developed fragility curves were subsequently applied to assess seismic risk and resilience for a typical underground civil defense structure in soft soils, offering valuable data-driven insights into the structure's performance under various scenarios. The results indicated that the seismic fragility of the civil defense structure increases with the softening of the soil. Moreover, this study highlighted the substantial influence of structural typologies and local soil conditions on the fragility of civil defense structures, particularly the seismic fragility of underground structures characterized by shallowly buried and large-section, and demonstrating the utility of data-based approaches in comprehending complex interactions. The efficiency and practicality analyses highlighted that ground surface IMs outperform bedrock IMs and acceleration-type IMs over velocity-type IMs. The proposed seismic fragility curves indicated that the exceedance probability for each damage state gradually approaches 100% with the increase of seismic intensity. Finally, a case study was presented on the use of seismic fragility curves to assessment of seismic risk and seismic resilience of civil defense structure. The outcomes of this research, enriched by data-based approaches, can serve as invaluable references for seismic performance assessment, risk analysis, and resilience evaluation of typical civil defense structures in similar soft soil sites.

Development of a GIS-Based Predicted-VS30 Map of Türkiye Using Geological and Topographical Parameters: Case Study for the Region Affected by the 6 February 2023 Kahramanmaraş Earthquakes

Abstract The time-averaged shear-wave velocity in the upper 30 m of a site (VS30) is virtually essential in characterizing local soil conditions for multiple purposes, including estimation of site effects, anticipated ground-motion levels, seismic hazards, and the shape of design spectra. Considering the significance of this proxy and that a number of the Disaster and Emergency Management Presidency of Türkiye (AFAD) strong ground-motion stations across Türkiye lack assigned VS30 values, a comprehensive study was performed herein to develop empirical equations for estimating VS30 values in Türkiye based on relationships between 432 VS30 measurements at the AFAD stations, geologic units, and topographic data. Initially, units in the geological digital maps were reclassified into four geological periods. Statistical relationships between geological period classes and VS30 samples were interpreted to determine the VS30 boundaries for each period class. Second, VS30 estimations with topographic parameters by utilizing a 2D trend surface analysis method were performed. The resultant two-parameter polynomial coefficients were associated with VS30 according to the least squares principle, leading to the development of topographic functions for VS30 estimation under each geological period class (R2=0.601). Thereby, digital VS30 estimation maps were produced in grid (90 m) format that may be queried in a Geographic Information Systems environment. Moreover, the quantile regression method was also utilized to determine the coefficients of the envelope curve corresponding to a given exceedance probability (p) for the worst case scenario. Finally, to evaluate the accuracy of the proposed equations, the verifications performed with the VS30 data at the selected AFAD stations in the region affected by the 6 February 2003 earthquakes have also presented successful outcomes. Considering the availability of VS30 maps derived from digital elevation data in the literature, this study offers novel equations that take into account geological units and provide crucial background data for the regional seismic hazard-based risk assessments in Türkiye, especially for site effect studies using VS30 as a regional site classification parameter.

Damage Evaluation and Seismic Assessment of a Typical Historical Unreinforced Masonry Building in the Zagreb 2020 Earthquake: A Case Study—Part I

The city of Zagreb, the national capital and economic hub of Croatia, is situated in a seismically active region and hosts a significant array of historical buildings, from the medieval to Austro-Hungarian periods. These buildings possess varying but generally high degrees of vulnerability to seismic loading. This was highlighted in the Zagreb earthquake of 22 March 2020, emphasizing the need for seismic retrofitting in order to preserve this architectural heritage. In this paper, the seismic capacity of one such unreinforced masonry building is considered through a number of analysis methods, including response spectrum, pushover, and out-of-plane wall failure analyses. Given the advantages and disadvantages of the individual methods, their applicability and value in a seismic analysis is considered. Ambient vibration measurements before and after the Zagreb 2020 earthquake, used for model calibration, are also presented. Conclusions are drawn from each individual analysis and later compared. In conclusion, no single analysis method considers all relevant failure modes, and a combination of nonlinear static or dynamic analysis and out-of-plane analysis is recommended. Due to the large volume of the material, it is published in two parts, with ground motion record selection, dynamic analysis, and a comparison of the results published in part two.

Seismic Damage Assessment of Reinforced Concrete Slab-Column Connections—Review of Test Data, Code Provisions and Analytical Models

Reinforced concrete slab-column connections are vulnerable to punching shear failure when subjected to combined gravity and lateral loadings during earthquakes. Over the years, many experimental campaigns have been conducted and assessed the seismic performance of flat slabs. The experimental findings were used to derive empirical equations for the design provisions. The paper aims to provide a detailed description of the code development for seismic punching shear. Two current code provisions (ACI 318-19, EC 2 & EC 8-2004) for seismic punching shear are presented and discussed. Relevant and updated experimental data of interior slab-column connections without and with shear reinforcement are selected and assessed against the current design provisions with a focus on key response parameters such as the drift ratio and the gravity shear ratio. The ACI 318-19 limit drift line is considered to assess the lateral deformation demand for the connections with respect to the updated database. The gravity shear ratio is shown to have a considerable impact on the limit drift ratio of slab-column connections without shear reinforcement. The majority of the test specimens with no shear reinforcement experienced punching shear failure, followed by the specimens which showed a combined flexure–punching failure. Punching shear failures occurred for a range of gravity shear ratios of 0.2 to 0.9, while all combined flexure–punching shear failures occurred for gravity shear ratio values below 0.5. The shear-reinforced concrete slab-column connections can achieve much higher drift ratios. Most of the slabs were reinforced with shear studs, particularly in the range of gravity shear ratios of 0.4 to 0.6. Most test specimens failed by flexure for gravity shear ratio values of 0.1 to 0.7, followed by the specimens which failed in combined flexure–punching for gravity shear ratio values that ranged from 0.3 to 0.9. Finally, the available numerical and analytical models for seismic punching shear are presented with the objective of observing their potential strengths and limitations.

Comprehensive review of seismic performance assessment for skew-reinforced concrete box-girder bridges

Comprehensive review of seismic performance assessment for skew-reinforced concrete box-girder bridges

Efficient seismic fragility assessment method for a frictional isolated bridge constrained by shape memory alloy cables under pulse-like ground motion

Utilizing shape memory alloy (SMA) cables to constrain frictional isolated bridges is considered an efficient approach to limit bearing displacement and prevent serious earthquake damage. Accurate seismic fragility assessments of this kind of structure are crucial for aseismic decision making. However, traditional assessment methods cannot quantitatively describe the impact of the pulse effect on pulse-type seismic motions, which may lead to inaccurate assessment results. Therefore, this study deduced a novel equation for seismic fragility assessment that considers the pulse effect. Firstly, the impact of the pulse effect is quantified. Then, a multivariable probabilistic seismic demand model (MV-PSDM) is developed that is conditioned on the pulse period, peak ground velocity, structural period, maximum friction coefficient and SMA consumption. Based on the MV-PSDM, an effective approach for predicting structural seismic vulnerability is recommended, which does not require finite element modeling or nonlinear time-history analysis. Finally, a novel equation for calculating the intensity measure corresponding to 50% damage probability is deduced. The results indicate that increased friction coefficients and SMA consumption can enhance structural seismic safety under pulse-type ground motions. However, when the ratio of pulse period to structural period is too small, increased friction coefficients or SMA consumption have no meaningful effect on the seismic fragility of the structure.

Lifetime seismic resilience assessment of a sea-crossing cable-stayed bridge exposed to long-term scour and corrosion

In the marine environment, bridges are exposed to long-term foundation scour and structural corrosion. Consideration of scour and corrosion effects is of crucial importance for the lifetime seismic resilience assessment of existing sea-crossing bridges. This study presented a framework of seismic resilience assessment for sea-crossing bridges exposed to long-term scour and corrosion. Three typical recovery functions were employed to establish the post-earthquake functionality recovery model considering underwater repair. The time-variant model of scour depth was developed by fitting the annual measured data with the empirical function. The time-variant corrosion model induced by chloride was developed by considering different exposure zones. Then, the models of scour depth and corrosion were applied to an example cable-stayed bridge to assess the lifetime fragility and resilience of the bridge. It is concluded that the developed scour depth model agrees well with the measured data and can reasonably estimate the time-variant scour depth. Compared to scour, corrosion dominates the increase in lifetime fragility and resilience loss for the bridge. Scour and corrosion effects significantly reduce the bridge's functionality and increase the difficulty of the recovery process. Ignoring the effects of scour and corrosion can lead to an overestimation of the seismic resilience of the bridge.

Systemic seismic risk assessment of urban healthcare system considering interdependencies to critical infrastructures

The performance of healthcare and other emergency systems, like firefighting, is of utmost importance in the aftermath of natural disasters such as seismic events. However, previous studies have often overlooked the interconnectedness of emergency systems to other critical infrastructures. In reality, the performance of the healthcare system does not only rely on the vulnerability of hospital buildings, but also on the vulnerability and performance of interdependent critical infrastructures, such as the transportation system for the accessibility of injured people to hospitals from the damaged sites or the continuous supply of water and electricity for the uninterrupted operation of hospital facilities. These interdependencies can significantly impact the overall emergency response effectiveness and is vital to consider them in the design and assessment of healthcare systems to safeguard resilience of the community. This study proposes a comprehensive methodological framework and associated metrics for evaluating and mapping the healthcare system's performance considering its interdependencies with other critical infrastructures. It encompasses hazard characterization, risk assessment at both component and system levels, and network-based analysis with conditional branching to account for first and second order interdependencies. The proposed framework is applied to the healthcare system of Thessaloniki, Greece. The operational tool and insights can help to prioritize ex-ante investments and identify ex-post intervention measures, ensuring an emergency response system on an urban scale within a resilient systemic perspective. Its applicability can be extended to address a spectrum of other hazards and interdependencies at urban and regional scales, to ensure peoples' safety and minimize socioeconomic losses.

Regional seismic response assessment using indicator buildings

Regional seismic response assessment using indicator buildings

The Te Puninga Fault, Hauraki Plains: a new seismic source in the low seismicity northern region of New Zealand

ABSTRACT In this study, we provide the first field-based assessment of the seismic potential of the Te Puninga Fault, Hauraki Plains, Waikato region. Initially considered to be part of the nearby Kerepehi Fault, our new mapping and field data suggest the Te Puninga Fault is independent. A new net slip rate value of 0.25 mm/yr, based on geomorphic data and evaluations from two paleoseismic trenches, is slightly higher than previously considered. Comparisons of geomorphic expression between the two faults suggest that the slip rate currently assigned to the Kerepehi Fault could be underestimated. The earthquake magnitude estimated here for the Te Puninga Fault (Mw 6.9 ± 0.35) is based on a characteristic earthquake model. New PGA and MMI estimates here are only slightly larger than those published prior to this study. Although ruptures of the Te Puninga Fault are infrequent (derived recurrence range of 3000–11,500 years), and thus its hazard is low, with this paper we wish to enhance the community awareness to prepare for the rare large earthquake in the region. We also recommend that this new information is added to fault databases used for seismic assessment.

Assessment of Initial Seismicity for Offshore Platforms: a Case Study of the Pechora Sea

Assessment of Initial Seismicity for Offshore Platforms: a Case Study of the Pechora Sea

A Physics-Based Seismic Risk Assessment of the Qujiang Fault: From Dynamic Rupture to Disaster Estimation

This study achieved the construction of earthquake disaster scenarios based on physics-based methods—from fault dynamic rupture to seismic wave propagation—and then population and economic loss estimations. The physics-based dynamic rupture and strong ground motion simulations can fully consider the three-dimensional complexity of physical parameters such as fault geometry, stress field, rock properties, and terrain. Quantitative analysis of multiple seismic disaster scenarios along the Qujiang Fault in western Yunnan Province in southwestern China based on different nucleation locations was achieved. The results indicate that the northwestern segment of the Qujiang Fault is expected to experience significantly higher levels of damage compared to the southeastern segment. Additionally, there are significant variations in human losses, even though the economic losses are similar across different scenarios. Dali Bai Autonomous Prefecture, Chuxiong Yi Autonomous Prefecture, Yuxi City, Honghe Hani and Yi Autonomous Prefecture, and Wenshan Zhuang and Miao Autonomous Prefecture were identified as at medium to high seismic risks, with Yuxi and Honghe being particularly vulnerable. Implementing targeted earthquake prevention measures in Yuxi and Honghe will significantly mitigate the potential risks posed by the Qujiang Fault. Notably, although the fault is within Yuxi, Honghe is likely to suffer the most severe damage. These findings emphasize the importance of considering rupture directivity and its influence on ground motion distribution when assessing seismic risk.

Technology Focus: Seismic (February 2024)

2023 wrapped up nicely with COP28 in Dubai. The key highlights were the commitments by both governments and the private sector to zero-methane production by 2030, net-zero greenhouse gas emissions from operations by 2050, and triple renewable power-generation capacity and double energy efficiency in this decade. There has been tremendous progress on our collective journey toward cleaner energy production, and now we must take it a notch higher. In the past couple of years, JPT’s Seismic feature has been marked by highly innovative seismic techniques and machine-learning work flows focused on reduction of carbon footprint; frontier exploration, expanding heartlands and brownfield development; and improved seismic survey, imaging, and attribute analysis for reservoir characterization and fracture diagnostics, which are in line with the COP28 pledges. This year’s feature is no different. Recent technical-paper titles have further shown the steady increase in the application of advanced seismic techniques and machine learning to mature “stranded” and “advantaged” hydrocarbon-bearing accumulations to production; improve carbon capture, storage, and leak detection; and analyze naturally and artificially induced fractured reservoirs and seismicity. The selected papers are reflective of these themes. In addition, some remarkable applications of seismic techniques are presented in the recommended papers. They include the following: - 2D nonlinear seismic site response analyses used to determine if the capacity of a silty sedimentation could support the load of a pipeline end termination in the event of an earthquake - The results of a pilot test of the Marine Vibrator, an industry-leading seismic-survey technique - High-resolution modeling to infer if an increase in seismicity is caused by an increase in pore pressure from wastewater injection in the Fort Worth Basin of north central Texas - 4D time/depth shifts and strain signals successfully used to estimate pressure depletion in the Gulf of Mexico Others are applying advanced measurement and modeling techniques to optimally place a long horizontal injector well in multilayered heterogeneous sandstone reservoirs and predicting reservoir presence from seismic velocity and pore-pressure prediction. These topics will supply the insights that will help us achieve the COP28 targets while we look forward to more exciting innovations in 2024. Recommended additional reading at OnePetro: www.onepetro.org. OTC 32267 Seismic Stability Assessment of a Mudmat on Liquefiable Seabed by Brian Carlton, Norwegian Geotechnical Institute, et al. OTC 32393 Predicting Reservoir Presence From Seismic Velocity Mapping and Pore-Pressure Prediction by Matthew James Legg, Shell OTC 32741 Marine Vibrator Milestone: A Pilot Seismic Survey by R. Alfaro, TotalEnergies, et al. SPE 212951 High-Resolution Modeling of Pore-Pressure Change, Fault Slip Potential, and Induced Seismicity in the Fort Worth Basin by Changqing Yao, Texas A&M University, et al. URTeC 3870451 Impact of Fracture Roughness on Fines Migration and Fracture-Aperture Growth in Calcareous Shale Rocks During Acidized Corefloods by Hasan J. Khan, King Fahd University of Petroleum and Minerals, et al.

Analytical and Numerical Models for Wind and Seismic Design and Assessment of Mass Timber Diaphragms

Analytical and Numerical Models for Wind and Seismic Design and Assessment of Mass Timber Diaphragms

Seismic Microzonation of the Himalayan Region Considering Site Characterization: Application toward Seismic Risk Assessment for Sustainable Tunneling Projects

Seismic Microzonation of the Himalayan Region Considering Site Characterization: Application toward Seismic Risk Assessment for Sustainable Tunneling Projects