Bulletin of Earthquake Engineering最新文献

A ground motion database of about 600 recordings from 15 intermediate-depth Vrancea earthquakes which occurred in the period 1977–2024 was assembled for this study. The Japan Meteorological Agency intensity (I_JMA) is evaluated for all the recordings in the database in order to have a more objective measure of the ground motion intensity since I_JMA takes into account both the amplitude, and the frequency content, as well. The results of the analyses show no visible trends in the variation of I_JMA with the horizontal peak ground acceleration as a function of the soil class. The ANOVA method shows that the earthquake magnitude is the most relevant parameter influencing I_JMA, while the soil class is the least relevant one. It has also been observed that the normal probability is appropriate for modelling the distribution of I_JMA for a given seismic event. Moreover, it has been observed that the horizontal components having the largest I_JMA for the largest five earthquakes in the database (the events of 1977, 1986, 1990 and 2004) can be considered as being pulse-like. The coefficient of variation for the PGA evaluated for the ground motions recorded in Bucharest area is on average 3.7 times larger than the one corresponding to I_JMA. An empirical model using the earthquake magnitude and the horizontal peak ground acceleration as parameters is proposed for the evaluation of I_JMA. Finally, the computed mean annual rate of exceedance for Bucharest for a level I_JMA = 5.0 is of about 0.02, a value obtained both from observations and from a simulated Monte-Carlo earthquake catalogue.

Earthquakes pose significant risks to urban areas, often leading to devastating economic losses and casualties. This paper aims to introduce YouSimulator, an innovative city-wide seismic damage simulation software, as a valuable platform for assessing urban resilience to earthquakes. Applied to Thessaloniki, Greece—a city with a notable seismic history as it was the first modern metropolitan area in Greece to be hit by a catastrophic earthquake—YouSimulator demonstrates its ability to quantify the functional integrity of urban areas by creating a digital twin of 1,252 buildings. The software consists of four key functional modules enabling automated modeling, seismic response calculations, comprehensive analysis of multi-degree-of-freedom responses and three-dimensional visualization of the seismic response. Utilizing parallel computing and high-performance algorithms, YouSimulator automates the assessment of building vulnerability, calculating a generalized damage index that categorizes buildings into five levels: free of damage, minor damage, moderate damage, severe damage, and destroyed/collapsed. The analysis reveals that Thessaloniki’s downtown performs satisfactorily under design earthquake scenarios, with no building collapses but a significant reduction in overall strength capacity of buildings. Notably, older pre-code reinforced concrete structures, which make up 96.3% of the building stock, exhibit high seismic vulnerability, highlighting the urgent need for retrofitting measures. Medium and tall buildings show increased susceptibility to severe damage, indicating a need for height-specific mitigation strategies. Additionally, pre-1959 buildings facing severe damage state should be targeted for structural interventions. Overall, this research validates YouSimulator for assessing urban seismic vulnerability and emphasizes the necessity of integrating detailed local seismic data into urban planning efforts to bolster resilience of cities against future earthquakes.

Using three Levels of detail with increasing complexity in terms of approaches and information required, Seismic Microzonation studies aim to map and assess the seismic ground response and the susceptibility to ground instability phenomena. In this paper, attention is focused on the assessment of 2D site effects for Seismic Microzonation studies of Level 3 performed for several municipalities located in Eastern Sicily (Italy) characterized by high seismic risk. The Seismic Microzonation studies of Level 3 required the collection of all existing geological, geotechnical and geophysical data performed in the investigated areas to define coherent subsoil models and the reference geological cross-sections for each municipality. The software REXELite was employed to select datasets of accelerometric waveforms from the Engineering Strong Motion database to be used for the ground response analyses. 2D Finite Elements Method analyses were performed using PLAXIS2D software. The Hardening Soil model with small-strain stiffness, that includes an increased soil stiffness for small strains, was adopted to model the soil non-linearity. In the framework of Seismic Microzonation studies, Amplification Factors were computed for three different period intervals and then compared with the simplified approach provided by the Italian seismic code for the evaluation of site effects, which is based on the definition of soil and topographic classes. Finally, the Topographic Aggravation Factor was assessed for each reference geological cross-section, demonstrating the importance of considering topographic effects in Seismic Microzonation studies. The outcome of this study provides a valuable base for engineers and planners in developing mitigation policies for the seismic risk reduction.

In this paper, a fiber-section model for the seismic analysis of ductile reinforced concrete columns with ribbed bars is proposed. The model is based on the simulation of the results of uniaxial-bending experimental tests and is built by using OpenSees software. Material models are proposed to replicate the response of cover concrete, of core concrete, and of steel rebars. A modelling strategy already proposed in the literature is incorporated in the proposed model to account for strain penetration effects. Correction coefficients are calibrated to account for the additional confinement provided to the end sections of structural members by other structural members, such as foundation elements. Literature formulations are applied to account for the fracture in tension of longitudinal rebars after buckling in compression. The proposed model can be adopted for the seismic nonlinear static and dynamic analysis of reinforced concrete structures.

Implementing advanced material-specific hysteretic models in structural analysis has opened new possibilities for post-earthquake damage assessment. This study introduces a novel methodology for estimating maximum seismic displacements utilizing the Takeda model for reinforced concrete and the AlBermani model for steel structures in single-degree-of-freedom systems. The research establishes correlations between residual and maximum displacements based on an extensive series of numerical simulations incorporating far-field and near-fault earthquake records. The developed mathematical relationships account for the distinct hysteretic behavior of different structural materials, providing a practical tool for post-earthquake evaluation. Field measurements of residual deformations can be directly applied to these relationships, enabling rapid assessment of maximum displacement demands experienced during seismic events. Statistical validation demonstrates the reliability of the proposed approach across various ground motion characteristics and structural parameters.

This study presents an investigation on the effects of damage and strengthening on the dynamic behavior of buildings. Forced vibration tests were carried out on the shake table of two 1/3 scale, 3D, 2-story, single-span reinforced concrete frame specimens produced in laboratory. The damage was created by weakening the joint areas. Then the damaged zones were repaired and strengthening methods using in-plane reinforced concrete shear walls and X-shaped steel diagonal bracings were applied. The aim here is to perform a dynamic-based performance evaluation of these two commonly used global systemic strengthening techniques in practice. A total of more than 105 forced vibration experiments were carried out under 4 different intensities of dynamic load in different conditions of the specimens. Dynamic parameters were determined with the experimental modal analysis method. Moreover, story displacements time history, base shears time history, base shear-top displacement hysteresis curves, and lateral translational stiffnesses were obtained. In addition, numerical analyses using ETABS finite element software were also conducted. As a result, it was observed that the damage reduced the lateral translational stiffnesses by about 50%, steel bracings increased the stiffness in the damaged condition by 147% and RC shear walls increased it by 381%. On average, the 1st natural frequency decreased by 36.5% in the damaged conditions, increased by 83% in the strengthened conditions compared to the damaged conditions. Strengthening of the members tends to limit the soft story behavior. In general, although its application is difficult, the best performance in all studied parameters was obtained from the specimen strengthened with in-plane reinforced concrete shear walls.

This paper investigates the seismic response of the three-story Cross-Laminated Timber (CLT) building of the SOFIE project subjected to the Near-Field (NF) Far-Field (FF) ground motions according to FEMA P-695. The numerical models have been developed in connector, wall and full-scale building levels in OpenSees. Nonlinear nonlinear springs have been utilised to model the behaviour of CLT connectors while considering Gap joints only to transfer compression forces between panels and the rigid foundation without the ability to carry tensile forces. The CLT panels have been modelled as moment-resisting frames by applying elastic beam elements with high stiffness. The panel-to-panel and panel-to-foundation friction has also been considered by modifying the initial stiffness of the CLT connector springs. The building was analysed using Incremental Dynamic Analysis (IDA), including 2450 time-history simulations, to assess its behaviour during ground motions. Significant Damage (SD) and Near-Collapse (NC) damage stated have been identified for the building based on EN12512 standard through Modal Push-over Analysis (MPA). Subsequently, the fragility curves have been developed for the CLT building under NF and FF ground motions. The IDA curves prove that the CLT building considered in this paper is more affected by Near-Field Pulse-like (NF-P) than by Near-Field No-Pulse (NF-NP) and FF ground motions. Moreover, the modelled building is significantly more affected by NF-P ground motions than by NF-NP and FF motions, with a higher probability of collapse under NF-P conditions.

One of the most significant challenges in structural civil engineering is accurately modeling the nonlinear behavior of structures under various loading conditions. To address this challenge, it is essential to consider three fundamental variables in mathematical modeling: the type of structural element, the material properties, and the complexity of the model used. In this context, the present investigation compares the structural responses of several reinforced concrete wall specimens, both with regular and irregular sections, subjected to complex loading protocols. Different two-dimensional material models, such as the fixed angle approach (FSAM) and the rotation angle approach, are evaluated using a novel computational element called the Membrane Element with Fibers in 3D (MEFI-3D). This element has been designed to predict the nonlinear behavior and response of three-dimensional reinforced concrete (RC) wall systems. In addition, this research presents the implementation of this novel element, MEFI-3D, in the open-source analysis software OpenSees (Open System for Earthquake Engineering Simulation). The element uses four nodes with a total of 24 degrees of freedom (DOF), encompassing six DOF per node (three translations and three rotations). The formulation employs a tangent stiffness matrix approach, effectively coupling nonlinear membrane effects with linear bending effects, addressing shear-flexure-compression interactions within the plane of the element. The study demonstrates that the MEFI-3D element is a reliable tool for predicting both global and local nonlinear responses of reinforced concrete walls based on different loading conditions, quadrature points and material approaches, thus MEFI-3D offers a promising advance in predicting the complex behavior of three-dimensional reinforced concrete walls contributing to more efficient and accurate structural analyses.

The IFMIF-DONES project will carry out the design and construction of a scientific facility near Granada (Spain), whose purpose is irradiation of materials with a neutronic spectrum similar to what is obtained within a nuclear fusion reactor. In the framework of the seismic hazard assessment for the IFMIF-DONES site, this paper compares two approaches to correct the overdamped high-frequency response of soil columns computed via regular equivalent-linear analyses. The site has a soft soil profile, with a V_s30 around 375 m/s. For soft soils, when introducing site effects in seismic hazard assessments, equivalent-linear analyses are known to overdamp high-frequency responses. This may result in unrealistically small relative amplification factors (RAFs) with respect to the host profile response, which is the reference in Ground Motion Prediction Equations. In this paper the overall methodology for derivation of RAFs is presented, based on equivalent-linear analyses, and two approaches to RAF correction are described: an empirical lower bound on the RAFs, taken from accepted practice, and the so-called kappa2 correction of the Fourier Amplitude Spectra. For small ground motions, differences in RAFs computed by the two methods are minimal, since soil degradation is limited. For higher-severity events, significant differences appear beyond 8 Hz. Two empirical RAF lower bounds, 0.5 and 0.6, were tested. The results for the IFMIF-DONES site suggest that the 0.6 lower bound provides a good average fit to the results obtained using kappa2 correction. For the stronger motions, the 0.5 lower bound provides a better fit in the 2.5–10.0 Hz band.

Analytical studies have demonstrated that tunnel-form system possesses relatively high strength and rigidity. However, in seismic evaluations of this system, only peak ground acceleration and spectral acceleration have traditionally been considered as the primary intensity measures representing earthquake ground motions. While this approach aligns with current seismic guidelines, it overlooks the importance of other critical ground motion characteristics. The present study introduces the time scaling of earthquake record method and, for the first time, employs it to modify the primary characteristics of input ground motions for the seismic evaluation of tunnel-form buildings. For the analyzed models of 2-, 5-, and 10-story, the findings reveal that significant duration, peak ground acceleration, and peak ground velocity have direct effects on the seismic responses of the system. Results indicate that, at a given hazard level, accurate predictions of seismic performance and demands require simultaneous consideration of all three parameters. Analyses show that at high hazard levels, an increase in velocity while keeping acceleration and significant duration constant can change the performance level of the system from immediate occupancy to collapse prevention. This highlights the critical role of velocity in seismic performance. Similarly, variations in acceleration and significant duration yielded comparable results. Under constant conditions for the other parameters, increases in acceleration and significant duration led to performance levels of life safety and immediate occupancy in the worst cases, respectively. Accordingly, these parameters rank second and third in importance when estimating seismic performance levels. Furthermore, the findings demonstrate that code-based relationships fail to predict the seismic demands of tunnel-form systems accurately. Consequently, revisions and modifications are necessary to incorporate the effects of ground motion characteristics.