Bulletin of Earthquake Engineering最新文献

This paper is focused on the definition of the vertical elastic response spectra. This study follows the recent development of the horizontal response spectrum in the framework of the revision of the Algerian seismic code RPA99 (Laouami and Slimani 2025). The same ground motion database is used, which comprises 773 3-component records, from magnitude ranging from 3.0 to 7.4, and hypocentral distances less than 200 Km. A statistical method is used to estimate constant spectral acceleration branch limits, attenuation indexes, and the ratio of the vertical to horizontal response spectra, at two seismicity levels: weak to moderate seismicity (wms) and moderate to high seismicity (mhs). The results of the analysis showed significant differences between the control periods of the elastic response spectra as a function of both the site class and the magnitude. The results reveal that the control period T_Cv increases as the site moves from rock to soft classes and from low to high earthquake magnitude, whereas the attenuation index decreases with increasing earthquake magnitude. The findings reveal also that the vertical to horizontal spectral ratio increase with magnitude and can exceed unity at near field for vertical vibration periods in the range 0.05–0.1 s. The recommended values of the ratio of vertical to horizontal design acceleration, (:{C}_{v/h}), for wms and mhs seismicity levels, are 0.60 and 0.80 respectively. Comparison to the vertical spectra of the ASCE7-16 and the new generation EC8-draft2022 standards, reveals that period Tc of the proposed spectra is in agreement with the ASCE7-16 for the wms seismicity level, and with EC8-draft2022 for the mhs seismicity level. Finally, two spectral shapes are proposed for the two seismicity levels wms and mhs. This solution enables a significant upgrade over the present version of the national seismic design code RPA99, which does not offer elastic response spectra for the vertical component of seismic motion.

Reinforced concrete (RC) structures are continuously exposed to aging, environmental effects, and extreme events such as earthquakes, resulting in progressive stiffness degradation and increased vulnerability. Accurate, time-resolved assessment of stiffness variations is essential for structural health monitoring (SHM) and seismic performance evaluation. This study proposes a novel framework based on the Enhanced Hilbert-Huang Transform (EHHT), integrating Empirical Mode Decomposition (EMD) and a newly defined Instantaneous Total Amplitude (ITA), to identify story-level stiffness variations. Unlike traditional frequency-domain methods that rely on stationarity assumptions, the proposed approach enables extraction of noise-resilient and physically interpretable stiffness patterns under both linear and nonlinear responses. The dynamic equilibrium equation is reformulated in the time-frequency domain, allowing for robust estimation of stiffness while minimizing the impact of modeling uncertainties, high-frequency noise, and permanent deformations. The method is validated through numerical and experimental studies, including a four-story RC frame with nonlinear behavior and a full-scale five-story RC structure tested on the UCSD-NEES shake table. Comparative analysis with analytical formulations, Power Spectral Density (PSD-based) operational modal analysis, and modal flexibility confirms the superior performance of the EHHT-based method. Findings highlight that stiffness degradation may occur even under weak ground motions, and that characteristics derived from strong shaking may not represent post-seismic conditions accurately. Instead, ambient vibration data recorded after seismic events are more suitable for reliable model updating. The proposed EHHT framework offers a theoretically sound and practically applicable tool for post-earthquake stiffness monitoring in civil infrastructure.

The Standard Spectra Ratio (SSR) of S-wave earthquake ground-motion, is a commonly applied technique between a target and a nearby reference-site, that provides Site spectral-Amplification Factor (SAF[f]). The required “nearby reference-site” constitutes a significant restriction of the SSR technique, which however, has been partially overcome, by relaxing it, based on a recent study, using an analytical, time–consuming 10–step analysis, using the Spectral Factorization method on Coda-waves (SFC). A first effort on this direction, has been earlier proposed by Phillips and Aki (Bull Seismol Soc Am 76:627–648, 1986), based on a more sophisticated technique on coda–waves, using vertical-component data, considering however an undefined reference–site, as the average of all studied–stations. Here, a new simplified empirical technique of SAF[f] computation at a target site with respect to a distant reference one, is examined as a combination of SSR and SFC methods, satisfying at the same time their main advantages, i.e. the easy application of SSR and the use of longer target-reference site distance of SFC. This SSR technique based on coda-waves (SSRc), has been applied in the past in several cases but based on a nearby reference-station. Here, it is modified to make use of a distant reference–station from the target one as well and is demonstrated and applied for several stations in two areas of different seismicity level: the low-to-moderate and the high seismicity areas of southeastern-France and western-Greece, respectively. The results are encouraging in further applying this alternative SSRc technique, compared to those retrieved by different methodologies and datasets, supporting its valid and effective application.

The assessment of the seismic fragility of unreinforced Masonry (URM) buildings in cities, using advanced numerical approaches, is hampered by the complex connectivity which develops with the diachronic process of urban growth and regeneration. The building stock forming 43 urban aggregates in the historic neighborhood of Yungay in Santiago, Chile, is the focus of this manuscript. The Failure Mechanism Identification and Vulnerability Evaluation method (FaMIVE), a mechanical approach based on limit-state analysis and failure modes, determines the collapse load factors and derive capacity curves for each of the 423 structures surveyed and analyzed. The objective of the study is to correlate specific sets of architectural features of these buildings to their seismic performance as represented through fragility functions. To this end we have introduced a new selection algorithm to automatically group the buildings using an optimal logic tree analysis (LTA). As a result, we obtain clusters of capacity curves using the observable properties of the façades as the decision variables of the LTA, while minimizing the variability of the parameters which define the capacity curves. The median capacity curve of each cluster is then used to derive Analytical Fragility Functions (AFFs), using a capacity-demand approach, which considers different sets of nonlinear spectra. The structure of the LTA is observed to be adequately preserved for fragility functions, fully justifying the subdivision in clusters. The aim of this work is to provide the data to prioritize mitigation strategies that enables us to preserve this heritage, as well as that of other similar historical urban areas in Chile and Latin American cities, which bear a strong architectural resemblance since their foundation.

Concrete pier caps are used for various bridge and submarine applications due to their unique features, including reduced stress on piers, efficient load distribution, enhanced durability, and improved stability. However, environmental factors can negatively impact concrete pier caps, leading to structural degradation and a reduced lifespan. This research investigates the application of tin (IV) oxide ceramic coatings to enhance the performance of concrete pier caps subjected to hydrodynamic pressure. Computational Fluid Dynamics (CFD) analysis is employed to study the effects of these coatings. The results focus on the flow of fluid and the presence of cracks within the structure, aiming to understand better how to control structural deterioration. All evaluations were conducted using MATLAB, where data processing was applied to analyze the simulation’s crack distribution patterns and stress distribution. The integration of CFD modelling with ceramic coatings represents a significant innovation for extending the lifespan of bridges, especially in harsh environmental conditions. The findings are compelling: by optimizing fluid dynamics around the pier cap, we achieve a 15% reduction in pressure drag, which significantly enhances overall flow efficiency. It found a reduced crack length of 0.7 mm at a stress of 20 MPa and improved thermal stability at 50 °C. Furthermore, scanning electron microscopy reveals that the application of tin (IV) oxide coatings results in a remarkably smoother and superior surface morphology compared to standard cement concrete, underscoring the potential of this innovative approach.

Soil liquefaction during earthquakes poses a persistent challenge in geotechnical engineering, particularly in translating advanced numerical simulations into reliable, performance-based damage predictions. This study presents a novel framework that incorporates the maximum excess pore pressure ratio (PPR_max)—a simulation–derived yet underutilized Engineering Demand Parameter (EDP)—to directly predict liquefaction–induced damage under site–specific seismic loading conditions. Dynamic effective–stress finite element simulations were performed for soft alluvial soils in the seismically active İzmir–Karşıyaka region. Using logistic regression and receiver operating characteristic (ROC) analysis, PPR_max thresholds were statistically calibrated against observed damage levels to define transition points between minor and moderate damage. This calibration enabled the derivation of fragility curves linking peak ground acceleration (PGA) to probabilistic damage states within a regional hazard–consistent framework. The study further demonstrates the critical role of liquefiable layer thickness in controlling seismic pore pressure response. Even under identical ground motion intensities, variations in stratigraphy produced significantly different damage outcomes—highlighting a major gap in current seismic codes, which often neglect subsurface variability. The proposed framework enhances the predictive capacity of liquefaction risk assessments by bridging physics–based numerical modeling and empirical damage observations. It provides a scalable foundation for integrating simulation–compatible EDPs into performance–based seismic design and risk mitigation strategies.

This study presents a comprehensive multi-algorithm framework for optimizing the Collapse Margin Ratio (CMR) of reinforced concrete (RC) structures subjected to seismic loading, in accordance with the FEMA P695 methodology. A hybrid approach combining Artificial Neural Networks (ANNs) with Genetic Algorithms (GAs) is employed, alongside standalone optimization techniques including Particle Swarm Optimization (PSO), Simulated Annealing (SA), and Bayesian Optimization (BO), to improve key seismic performance parameters. A dataset of 114 RC archetype structures is analyzed through more than 5,000 Incremental Dynamic Analyses (IDA) using far-field ground motion records. Surrogate models and metaheuristic algorithms are used to efficiently identify optimal values for input parameters such as fundamental period, yield and ultimate displacements, overstrength factor, and spectral acceleration. The results demonstrate that ANNs and PSO deliver the most robust performance, achieving a maximum CMR of 5.99. Sensitivity analysis further underscores the dominant influence of the fundamental period and overstrength factor. The study also incorporates uncertainty quantification and outlier detection to enhance the reliability of the optimization process. This data-driven methodology not only improves seismic resilience and cost-efficiency in structural design but also advances the integration of computational intelligence into performance-based earthquake engineering.

The objective of the present paper is the evaluation of the seismic response of reinforced concrete corner buildings interacting with adjacent structures along two orthogonal directions (biaxial seismic interaction). For this purpose, two 8-storey corner buildings, one with soft ground storey and one fully infilled with masonry panels, are designed according to current European standards. The corner buildings under consideration are supposed to be in contact with lower structures in many alternative ways, formulating various cases of biaxial seismic interaction. All structural systems are analyzed by means of inelastic dynamic step by step analysis for concurrent action of two horizontal accelerograms applied with four alternative orientations. The response of the corner buildings is assessed through the calculation of crucial response quantities. The whole study demonstrates the importance of biaxial seismic interaction which might amplify up to about four and ten times the internal forces and deformations, respectively. It also highlights the role of several factors such as the unfavorable soft-storey effect which might increase the column shear deformations twentyfold and the role of the ground motion orientation. Finally, it indicates that the phenomenon is much more severe in comparison with the well-studied uniaxial seismic interaction between adjacent structures since it produces up to nine times larger response quantities.

This study investigates the seismic performance of reinforced concrete (RC) dual frame-shear wall buildings with nonparallel system irregularities under both far-field and near-field ground motions. Utilizing nonlinear time history analysis and Incremental Dynamic Analysis (IDA), seven six-story RC models—comprising one regular and six irregular configurations—are analyzed to evaluate collapse capacities, torsional responses, and story drift demands. The findings challenge the classification criteria in ASCE 7–22, revealing that minor wall inclinations (up to ~ 14°) have a negligible impact on collapse capacity, whereas more pronounced inclinations (~26.5°) significantly increase local seismic demands and compromise structural performance. The results suggest that local wall inclinations have a more significant impact on collapse resistance than overall torsional irregularity, highlighting the need for refined regularity classifications that consider localized effects rather than relying solely on global torsional behavior. Although enhanced design strategies improved collapse resistance, they failed to ensure secure performance in highly irregular models, even when fully compliant with seismic code provisions. Near-field ground motions intensified structural vulnerabilities, prompting earlier collapse onset and necessitating stricter criteria for distinguishing between regular and irregular models. These findings underscore the challenges posed by short-duration, high-intensity seismic pulses and the limitations of current design provisions in mitigating their effects. This study emphasizes the need for refined classification criteria and performance-based design improvements to better capture the complex behavior of nonparallel system irregularities, offering critical insights for developing more resilient structural design frameworks.

Unreinforced masonry (URM) structures subjected to moderate-to-severe earthquake ground motion often experience a poor performance, characterised by extensive cracking phenomena and the activation and development of collapse mechanisms. This produces high repair costs and a severe threat to human life. Furthermore, outward projection and accumulation of debris may reduce road serviceability, undermining rescue efforts and increasing post-event downtime. In this study, the suitability of the Applied Element Method – a discrete crack, rigid body and springs-based numerical technique – to capture damage spread, collapse mechanism activation and debris projection phenomena is tested against experimental data. Fracture energy-based softening laws are employed, improving numerical accuracy over the standard brittle failure models commonly implemented within AEM tools. The validated models are then used to assess the seismic performance of URM buildings under varying masonry quality, and hence mechanical properties. The study leverages on the inherent advantage of the AEM, that is, explicit simulation of cracking phenomena and body fragmentation with lower computational demand than other advanced numerical techniques, in order to: (i) simulate complex failure mechanisms, eventually leading up to collapse activation and subsequent stages of debris formation and accumulation; (ii) introduce novel damage measures that are able to explicitly quantify crack propagation and severity in URM load-bearing structures.