Bulletin of Earthquake Engineering最新文献

Mitigating seismic risk for critical facilities is crucial for governments, decision-makers, researchers, society, and the economy in earthquake-prone regions in Europe and worldwide. The paper discusses some essential concepts and methods for developing and implementing a real-time risk assessment methodology through a specific testbed example in light of an engineering-based seismic risk reduction approach for critical buildings. The goal is to demonstrate that real-time seismic risk assessment of a target building could be feasible by combining a calibrated earthquake early warning system (EEWS) with the knowledge of structure-specific fragility curves evaluated with the aid of well-designed structural monitoring arrays. The whole approach is illustrated for a school building located in Thessaloniki city center. The target school is instrumented with permanent and temporary monitoring arrays using commercial accelerometric/velocimeter stations and special in-house developed low-cost Micro-Electro-Mechanical Systems (MEMS). Structural health monitoring (SHM) allows identifying the dynamic characteristics of the building and, finally, generate structure-specific fragility functions, which may differ from generic ones. Past and current seismic events recorded on the regional seismic network and locally on sensors installed at the school building are used for the calibration and validation of the regional EEWS in order to reduce the rate of false or missed alarms. The refined structure-specific fragility functions are incorporated into the central database and used by the developed real-time risk assessment software for the promptly prediction of seismic damages and losses. The performance of the whole system is effectively checked for a strong seismic event by reproducing the Mw 6.5, 1978 Thessaloniki destructive earthquake based on 3D physics-based numerical simulations.

This study analyzes the Pazarcik and Elbistan earthquakes, which occurred on February 6, 2023 and are among the most destructive seismic events of the 21st century. Since the greatest damage was seen in Hatay in these earthquakes centered in Kahramanmaras, the study aims to contribute to the field of earthquake engineering by evaluating the seismic data obtained from these regions. In the first part of the analysis, peak ground accelerations (PGA) recorded at the stations in Kahramanmaras and Hatay were examined and these data were compared with the DD1 (maximum considered earthquake) and DD2 (design basis earthquake) design levels of the Turkish Building Earthquake Code (TBEC 2018). In addition, the effects of ground properties and proximity of faults on seismic records obtained from various stations were evaluated by examining the PGA distribution spatially. The impacts of factors such as the near-fault effect, directivity effect, ground amplification effect and impulse-like motions were determined by examining the peak ground accelations, peak ground velocities, peak ground displacements and spectral accelerations. The study uses NGA-West2 Ground Motion Prediction Equations (GMPEs) to evaluate peak ground accelerations in stiff soil and to consider impulse and directivity effects. In addition, the applicability of USGS Vs30 maps in Turkiye is evaluated by comparing with AFAD data. These comprehensive analysis provide critical insights from a structural safety perspective on how seismic characteristics change with ground properties and proximity to earthquake sources.

Explicit representation of uncertainties is essential to improve the reliability of seismic assessments of earthquake-damaged buildings, particularly when dealing with unreinforced masonry buildings. Modern inspection techniques use images for detecting and quantifying the damage to a structure. Based on the principle of falsification, this paper evaluates how the use of information of damage that is obtained from images taken on earthquake-damaged buildings reduces the uncertainty when predicting the seismic response under a future earthquake. New model falsification criteria use information on the residual state of a building, such as shear cracks, residual roof displacements, and observation of out-of-plane failure. To demonstrate the effectiveness of these criteria in reducing the uncertainty in response predictions, results from a four-story unreinforced masonry building stiffened with reinforced concrete walls, which was experimentally tested under a sequence of ground motions, are assessed. Three commonly used modeling approaches (single degree of freedom (DOF) systems, multi DOF systems with four DOFs, and equivalent frame models) are used, where uncertainties in model parameters and model bias are included and propagated through the analysis. Out of the models used, and in the absence of any additional source of information, the proposed falsification criteria are most effective in connection with the equivalent frame model because this model can simulate the response at the element-level, while the simpler models can only represent the global response or the response at the storey-level. The results show that when using only the information on the presence of shear cracks, which might be the first and only source of information after an earthquake, the effectiveness of model falsification is increased, thus reducing the uncertainty in model parameter values and seismic response predictions through the use of image-based inspection.

This paper experimentally investigated the in-plane seismic behavior of perforated masonry walls (pier-spandrel substructures) retrofitted using engineered cementitious composites (ECC). One unreinforced masonry (URM) specimen and two ECC-reinforced masonry substructures were prepared and subjected to pseudostatic cyclic lateral loads. The failure mode, hysteretic curves, strength, deformability, stiffness, and energy dissipation capacity of three specimens were compared and discussed. The results revealed that the failure pattern of masonry pier-spandrel substructure was improved by the ECC layer with shear failure of masonry piers changing to bending failure. Multiple thin cracks were observed on the surface of ECC overlay. Moreover, the external ECC layer effectively increased the load-carrying capacity and ultimate deformation of the substructures, with maximum increases of 104% in strength and 72% in ultimate displacement, respectively. Finally, the excellent energy dissipation capacity was obtained by ECC overlay, which can improve the collapse resistance of masonry structures subjected to strong earthquake action.

The study delves into direct displacement-based design (DDBD), an approach rooted in performance-based design, operating within predetermined response limits. The approach’s positive influence on diverse structural typologies is evident, emphasising the soil beneath reinforced concrete (RC) frame structures, particularly those designed using DDBD. The present research scrutinises the performance of a 15-storey RC frame building, considering the intricate interplay of soil-structure interaction (SSI). Employing a fiber modelling approach for frame elements and adopting a pile-raft foundation model, incorporating soil stiffness and nonlinearity through soil springs, the RC frame is meticulously designed to meet rigorous life safety performance criteria under DDBD principles. Various ground motions of varying intensities are applied to the RC frame to conduct incremental dynamic analysis (IDA), offering a comprehensive assessment of nonlinear structural behaviour in terms of displacements and inter-storey drift ratios. Ground motions are judiciously selected and scaled following the comprehensive calculative procedure outlined in FEMA P695 (Quantification of building seismic performance factors, FEMA P695. Prepared by Applied Technology Council For the Federal Emergency Management Agency, Washington, 2009). The resulting responses are leveraged to predict collapse probabilities, employing diverse approaches in the construction of seismic fragility curves. The research significantly contributes to the advancement of seismic design methodologies, ensuring structures adhere to robust resilience standards against seismic hazards. The RC frame design incorporating SSI demonstrates an 11.25% reduction in the inter-storey drift ratio and a lower probability of collapse at higher intensities compared to a fixed-based RC frame, indicating improved structural flexibility.

Confined brick masonry structures have garnered considerable attention as an effective solution for earthquake-prone regions due to their robust construction, efficient wall-to-column connections, and optimised utilisation of material strength. Within the realm of building design and construction, openings play a pivotal role, serving as essential elements for facilitating natural light and fresh air into the structure. However, the presence of openings within confined brick masonry walls causes a significant reduction in their seismic resistance. Hence, striking the right balance between these openings and structural strength is crucial. For this purpose, it is necessary to investigate the influence of size, shape, and position of the openings in confined brick masonry walls on their seismic performance. In this work, a comprehensive finite element macro-model is adopted that treats the wall and tie members as a unified system. A concrete damage plasticity approach is employed to predict damage progression in confined brick masonry walls. Using a pushover analysis in finite element framework, the ultimate strength, stiffness, and energy absorption capacity of confined brick masonry with different types of openings is assessed. Furthermore, a parametric study is conducted incorporating various scenarios, such as aspect ratios of confined brick masonry walls, diverse shapes of opening and variations in the positions of windows, doors, and combinations of both openings. Based on the results, simplified equations are developed to facilitate analytical estimation of ultimate strength, along with recommendations for optimising opening shape, size, and placement to enhance the design of confined brick masonry walls with openings. The study highlights that larger openings in confined brick masonry walls diminish ultimate strength, stiffness, and energy dissipation due to reduced load distribution and increased stress concentrations. Openings smaller than 10% of the masonry area maintain load paths, but larger openings require additional support. Rectangular openings with greater height than width exhibit superior performance. Furthermore, the positioning of windows significantly influences wall strength, with placements farther from the loading point proving favorable. Door placement also impacts ultimate strength, with central placement compromising stiffness. Combining window openings with a centrally located door maintains consistent ultimate strength but affects stiffness. Overall, this research contributes to a better understanding of the seismic behaviour of confined brick masonry structures with openings, offering valuable insights for engineers and architects working in regions susceptible to seismic activity.

The devastating (:{M}_{W}) 7.8 Pazarcık earthquake on February 6, 2023, profoundly impacted a large region in south-central Türkiye and northwestern Syria, resulting in over 50,000 casualties and widespread damage. To better understand source properties and wave-propagation effects of this event, we analyze the strong ground-motion data recorded at ~ 230 stations. We determine the regional distance-dependent attenuation using the horizontal RotD50 Fourier acceleration amplitude spectrum (FAS) in the frequency range of 0.1–20 Hz. We find an apparent near-source saturation effect which needs to incorporate an additional finite-fault factor for the distance scaling. Uncertainty and sensitivity analyses are considered by variable decay rates in the geometric spreading model. For each decay rate, we derive a corresponding (:Qleft(fright)) model to account for the frequency-dependent anelastic attention. Significant duration of ground motions is modelled for two different measurements based on Arias intensity ((:{I}_{A})). For site amplification, we construct a model containing both (:{V}_{S30})-scaling and peak ground acceleration (PGA)-scaling. Source parameters are then determined using a reference Fourier source spectrum at 1.0 km. Specifically, we estimate the mean corner-frequency as (:{f}_{0})= 0.036 Hz, Brune stress drop as Δσ = 4.79 MPa and the reference rock site κ₀ = 0.051 s. By analyzing near-source pulse-like waveforms, we demonstrate that the mismatch of peak ground velocity (PGV) between our model and close-distance observations is due to the rupture directivity effect. Finally, we compare ground motions of the 2023 (:{M}_{W}) 7.8 event to those of the 2023 (:{M}_{W}) 7.6 Elbistan and the 2020 (:{M}_{W}) 6.7 Sivrice earthquakes. Attenuation effects estimated for the three events are found to be identical between ~ 0.2 and 6.0 Hz, with slight differences in site responses above ~ 5.0 Hz. Source spectra comparisons indicate that the source properties are complicated for all three events. Our comprehensive ground-motion analyses contribute to understanding and modeling regional properties of attenuation, site response, and event-based source characteristics that are important for future region-specific seismic hazard assessment.

The seismic resilience of steel bridge piers can be weakened due to the ageing effect that occurs throughout their entire life-cycle stage. Seismic strengthening is a practical approach to enhance the seismic performance of ageing piers. Nevertheless, the conventional strengthening methods often result in a higher stiffness of bridge piers. This can potentially intensify the local seismic responses of the strengthened bridge pier and change the failure mode during seismic events. Hence, this study extends a strengthening technique, the Contact Stiffener Strengthening Method (CSSM), which aims to enhance the ductility of ageing steel bridge piers without causing an excessive increase in stiffness. This method uses the contact effect to increase the seismic performance of aging piers by ingeniously designed stiffeners. The static and dynamic approaches are employed to compare the effects of CSSM and traditional strengthening methods on seismic performance enhancement. Finally, this study proposes the prediction methods for the ultimate strength and displacement of the strengthened piers. The analysis results reveal that the occurrence of the contact phenomenon and buckling at the free-end plate indicate the initiation and ultimate states of the contact stiffeners. The strengthening efficiency in retrofitted piers is greatly influenced by the parameters of the free-end plate. The strengthening efficiency of bridge piers can be significantly affected by varying parameters of corrosion when using the same contact stiffener. The errors in the proposed prediction methods for the ultimate displacement and ultimate strength of the strengthened piers can be controlled within 15% and 10%, respectively.

Following the 2010/2011 Canterbury, New Zealand earthquake sequence, Auckland Council actively identified and assessed commercial buildings within the Auckland region to establish whether they were earthquake prone. Masonry infill buildings are one class of building type that was considered to be potentially earthquake-prone, with this building type constituting a significant proportion (9%) of all commercial buildings in the Auckland region. Despite the Auckland region being categorised as a low seismicity region in the current New Zealand seismic loadings standard, rupture of the Wairoa North fault located within the Auckland region could potentially generate significant earthquake shaking in the future. The reported study was undertaken to forecast the damage distribution for low-rise and mid-rise masonry infill buildings when subjected to ground motions from the Wairoa North fault that incorporated a combined mainshock-aftershock earthquake sequence. The results showed that mid-rise masonry infill buildings were forecast to exhibit significant damage when compared to low-rise masonry infill buildings. In addition, the seismic risk associated with mid-rise masonry infill buildings was forecast to significantly increase when aftershock earthquake scenarios were applied. It is noted that the increased seismic risk of mid-rise masonry infill buildings (when compared to their low-rise equivalent) was unsurprising because post-earthquake observation following the Canterbury earthquake sequence showed that mid-rise masonry infill buildings sustained higher levels of damage in comparison to low-rise masonry infill buildings.

Two new structure-specific scalar intensity measures for plane reinforced concrete moment resisting frames under far-fault ground motions are proposed. These intensity measures, of the spectral acceleration and spectral displacement type, are characterized as multi-modal and multi-level. They encompass the effects of the first four natural periods and are defined for four performance levels, including considerations of inelasticity up to the collapse prevention level. This is achieved with the aid of equivalent linear modal damping ratios previously developed by the authors for performance-based seismic design purposes. These modal damping ratios, dependent on period, soil type, and deformation, are associated with the transformation of the original multi-degree-of-freedom (MDOF) nonlinear structure into an equivalent MDOF linear one. The proposed intensity measures are conceptualized to be simple and elegant, incorporating all the aforementioned features rationally, without the artificial combination of terms, definition of period ranges, or addition of coefficients determined by optimization procedures. This approach sets it apart from existing measures that attempt to account for multiple modes and inelasticity. A comparison of the proposed intensity measures against ten of the most popular existing ones in the literature, focusing on efficiency, practicality, proficiency, scaling robustness and sufficiency, demonstrate their advantages.