Bulletin of Earthquake Engineering最新文献

Nepal’s earthquake risk is intensified by rapid urbanization, substandard construction practices, limited preparedness, and vulnerable reinforced (RC) buildings. Many RC structures are either non-engineered or built using outdated Mandatory Rules of Thumb (MRT) (NBC 205:1994), termed “pre-engineered”, which no longer meet current standards. The Gorkha earthquake exposed severe vulnerabilities, highlighting the need for retrofitting interventions to enhance seismic resilience. While previous studies assessed existing low- to mid-rise RC buildings, significant gaps remain in the application of conventional methods, open-source software, and cost-effective retrofitting schemes that incorporate both traditional and innovative techniques across diverse building typologies. This study selected six typical buildings including symmetrical, plan-irregular, and vertically irregular structures of three- and four-stories. The seismic vulnerability of non-engineered and pre-engineered buildings within these typologies was assessed through non-linear static and dynamic analyses performed in OpenSees. Retrofitting methods, including RC jacketing, Steel jacketing, and Fiber-reinforced cementitious matrix (FRCM) including Glass FRCM and Hemp FRCM, were applied to upgrade these structures to meet the latest seismic design code NBC 105:2020. Incremental dynamic analysis (IDA) was conducted, and fragility functions were derived for each building model before and after retrofitting. The findings indicated that retrofitted models exhibited higher ductility and lateral load-carrying capacity, reduced inter-story drifts, and delayed damage onset under increasing seismic loads, thereby meeting current code requirements. At 0.4 PGA, the probability of exceeding the life-safety limit state decreased from 100% to 45% in non-engineered buildings and from 90% to 38% in pre-engineered buildings. Glass-FRCM was the most effective, while Hemp-FRCM was least effective. Irregular structures required more extensive retrofitting than symmetrical ones.

Seismic risk analysis is crucial for assessing and mitigating the impacts of earthquakes on infrastructure. A fundamental component of this analysis involves the selection of hazard-consistent ground motions that exhibit good consistency with seismic hazard curves over various periods and encompass a wide range of hazard levels. Traditional methods for selecting such hazard-consistent ground motions often have limitations, typically maintaining consistency at only a limited number of periods and using discrete intensity levels, potentially leading to inaccurate risk assessments. This study proposes an innovative methodology that overcomes these limitations by employing equivalent earthquakes, which are derived from specialized seismic hazard disaggregation techniques. Unlike traditional methods that focus on a target response spectrum corresponding to a specified hazard level, this new method utilizes seismic hazard curves at multiple periods as the primary targets. The ground motions selected using this method cover a wide range of seismic hazard levels, with particular emphasis on higher hazard levels associated with rare events. Numerical examples in the study demonstrate that ground motions selected by the proposed method maintain robust consistency with the site-specific seismic hazard curves over various periods. Importantly, the proposed method is independent of the fundamental periods of specific structures, allowing for its application in accurate seismic risk analyses for various buildings at the same site. This comprehensive methodology is expected to enhance the field of seismic risk analysis by improving the accuracy and applicability of hazard-consistent ground motion selection. However, it is important to note that the proposed method is designed for risk-based applications, where a larger number of ground motions are selected. One limitation of the method is that it may not be as practical for intensity-based assessments.

In existing pre-disaster earthquake reconstruction cost estimation methods, the basic assumption is that the building meets building code standards. However, in Indonesia, many buildings do not meet these standards, requiring a special approach. One such approach is to categorize buildings based on damage levels that follow standardized damage criteria. The main objective of this research is to identify the cost drivers of earthquake rehabilitation and reconstruction at each level of damage. This research uses multiple linear regression analysis models for each damage level (light, medium, and heavy). The regression analysis was conducted on 79 public buildings (schools, clinics, and government buildings) from post-earthquake reconstructions in Lombok in 2018 and Mamuju in 2021, Indonesia. The results show that, at the light damage level, variable cost drivers were identified as seismicity, building occupancy level, total floor area, reconstruction duration, and total reconstructed ceiling area. At the moderate damage level, the identified variable cost drivers were seismicity, building occupancy level, reconstruction duration, total reconstructed wall area, and demolition cost per total area. At the heavy damage level, the variable cost drivers identified were seismicity, location class, structure type, total floor area, and total reconstructed wall area. Identifying cost drivers is important for improving the accuracy of pre-disaster estimation models. In addition, the identified cost driver variables also reflect the key variables in the standardized building code that are often not complied with in Indonesia, indicating that regulatory improvements could begin with these variables.

This study proposes an enhanced macroseismic method, based on RISK-UE LM1 Vulnerability Index model, for assessing the vulnerability of social housing buildings constructed between 1950 and 1975, which typically lack seismic provisions, feature repetitive architectural designs, and have either exceeded or are about to exceed their design working life. Initially, a comprehensive review of existing literature was conducted to identify relevant vulnerability parameters for calculating the Vulnerability Index. Huelva, located in southern Spain, was chosen as a pilot city due to the representativeness of its buildings and the availability of original project documents. Analysing these documents, along with microzonation studies and on-site visual inspections, facilitated an understanding of the structural types (primarily reinforced concrete moment-resistant frames or unreinforced masonry walls) and the further analysis of the selected vulnerability parameters. The new method improves upon the original by incorporating several enhancements, like integrating the number of floors into the Type of Soil Modifier, creating a Combined Modifier that amalgamates parameters based on the construction year, defining the Vertical Irregularity Modifier based on the building’s compactness ratio, and introducing a Slope of the Ground Modifier. Additionally, it considers pounding effects solely for staggered floor slabs and features adapted modifier weights for the specific building types. To address potential overestimation caused by summing multiple modifiers, the method employs a modified square root of the sum of squares (SRSS) approach, which provides a more robust estimation of their combined impact. The method was applied to buildings in Huelva using deterministic (recurrence of the 1755 Lisbon earthquake) and probabilistic (code, intensity VII) scenarios. Results reveal expected damage levels contradicting the damage control philosophy, indicating the need for preventing interventions and further research on similar structures.

On February 6, 2023, the Kahramanmaraş-centered earthquakes caused significant loss of life and extensive structural damage. These events have considerably increased research attention, especially on the seismic performance of retrofitted buildings. This study investigates a school building that was retrofitted in 2020 through the in-plane insertion of reinforced concrete shear walls but collapsed during the 2023 earthquakes. It is a significant case, as it is the only retrofitted building that collapsed according to official records. A comprehensive dataset was collected, comprising retrofitting plans, structural drawings, material and soil properties, and structural analysis reports. Finite element models of the retrofitted and non-retrofitted structures were developed in ETABS, and nonlinear pushover and time history analyses were performed. Pushover analyses assessed the retrofitting’s engineering suitability, while time-history analyses investigated the collapse mechanisms and overall seismic response. Results were compared in terms of story displacement, drift, forces, acceleration, energy components, and structural performance. Pushover analyses demonstrated up to an 80.6% reduction in both story displacements and drift ratios after retrofitting. However, damage levels in some columns increased, and improvements at upper stories remained limited. Time history analyses revealed reductions in displacement and drift demands of up to 89%, confirming overall performance gains. Stiffness increase caused substantial rises in story accelerations (up to 1600%) and shear forces (up to 70%), particularly in upper floors. These findings indicate that performance limitations stem from both design-related and construction-phase deficiencies. Therefore, future retrofitting strategies should adopt a holistic approach, integrating balanced stiffness distribution, optimized shear wall layout, precise connection detailing, and strict construction quality control.

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.