Search Results (194)

In the design of an experimental water tank equipped with a movable underwater shaking table featuring a large travel range, numerous auxiliary devices must be installed beneath the tank, resulting in substantial occupation of the available space. In this context, the optimal design of the water-supply passage within the flow-making system has emerged as a key engineering challenge. To investigate the optimal design of the flow-making system for an experimental water tank equipped with a movable underwater shaking table, this study uses the construction of the experimental water tank at the National Facility for Earthquake Engineering Simulation (NFEES) as a case study. Several candidate design schemes were proposed and evaluated using computational fluid dynamics (CFD) simulations to identify the optimal configuration. Following the selection of the flow circulation scheme, a flow-guiding device was further designed at the tank outlet to improve the flow pattern within the water tank. The results demonstrate that the horizontal–vertical combined layout is the optimal configuration for the water-supply passage. For the flow-guiding device, the optimal design consists of guide vanes arranged parallel to the guiding slope with a vane angle of 0°, a total of five vanes, and a vane density of 1.0. The flow-making system was constructed based on the optimal design identified through numerical simulations, and full-section flow-making experiments were subsequently conducted in the completed water tank under various water depth conditions. The experimental results show good agreement with the numerical predictions, confirming the feasibility and effectiveness of the proposed design. The findings of this study provide valuable guidance for the design and performance optimization of flow-making systems in experimental water tanks equipped with movable underwater shaking tables. Full article

Investigating the relationship between ground motion intensity measures (IMs) and structural responses is fundamental to seismic hazard assessment and performance-based structural design. However, most existing studies are based on the fixed-base assumption, where foundation flexibility is neglected, limiting the understanding of the effects of Soil–Structure Interaction (SSI) on IM–engineering demand parameters (EDPs) correlations. This study systematically evaluates the correlations between various IMs and EDPs while explicitly accounting for SSI effects, with particular emphasis on the influence of ground motion type (near-fault and far-field records). The results indicate that SSI modifies the correlations between IMs and structural responses, although its influence varies among different categories of IMs. For acceleration-based IMs, SSI has a limited impact on their relative effectiveness, preserving their ranking despite moderate changes in correlation coefficients. Velocity-based IMs consistently exhibit the strongest correlations with structural responses; however, their relative performance is strongly dependent on the characteristics of the input ground motions. In contrast, displacement-based IMs demonstrate substantial sensitivity to both soil conditions and ground motion characteristics, resulting in pronounced variability in their predictive capability across different seismic scenarios. These findings highlight the important influence of SSI in IM–EDP correlation analysis and emphasize the necessity of incorporating foundation flexibility when selecting candidate IMs for seismic performance assessment. The results are expected to improve the understanding of IM–response correlations in SSI systems and may help inform the preliminary screening of candidate IMs for performance-based earthquake engineering applications Full article

The assessment of seismic performance of existing buildings has traditionally focused on structural safety and damage limitation, often neglecting the explicit quantification of the associated economic consequences. In recent years, performance-based earthquake engineering (PBEE) frameworks have enabled a direct link between structural response and probabilistic loss estimation, allowing economic metrics to be integrated into seismic risk evaluation. Among these, the Expected Annual Loss (EAL) represents a comprehensive indicator that accounts for seismic hazard, structural vulnerability, and exposure over the building’s lifetime. This study presents a performance-based seismic loss assessment of an existing reinforced concrete building, adopting EAL as a global metric for seismic performance evaluation. The case study concerns an existing hospital building designed primarily for gravity loads and representative of a large portion of the Italian building stock. A detailed nonlinear numerical model is developed using OpenSees ver. 3.8.0, incorporating shear-critical behavior through nonlinear link elements. Structural performance is evaluated through modal analysis, pushover analysis, and nonlinear time-history analyses using a set of ground motions selected and scaled according to intensity-based criteria. Seismic losses are estimated following the FEMA P-58 methodology, implemented through the PACT software ver. 3.1.2, integrating structural response demands, component fragility functions, collapse probability, and seismic hazard curves. Probabilistic loss curves are derived, and the EAL is computed as a synthetic indicator of economic seismic performance. The results highlight the effectiveness of EAL in capturing the combined effects of seismic hazard and structural vulnerability, demonstrating its potential as a robust decision-support metric for seismic risk mitigation, retrofit prioritization, and insurance-related applications for existing buildings. Full article

The seismic fragility of reinforced concrete (RC) bridge piers is critical for urban rail transport systems, as severe pier damage may interrupt post-earthquake operation and threaten network safety. Compared with conventional highway bridge piers, urban rail transport RC solid piers usually have lower axial load ratios, larger cross-sections, and stricter serviceability requirements. However, the combined effects of geometric parameters, reinforcement detailing, and material strength on their cyclic behavior, dynamic response, and seismic fragility remain insufficiently understood. To address this issue, seven 1/4-scale RC solid pier specimens were tested under quasi-static cyclic loading to examine the effects of pier height, transverse reinforcement ratio, and longitudinal reinforcement ratio on damage evolution, hysteretic response, skeleton curves, and energy dissipation. A fiber-based OpenSees model considering bond-slip effects was then established, validated against the tests, and extended to a full-scale prototype pier for parametric analysis. The effects of aspect ratio, axial load ratio, longitudinal reinforcement ratio, stirrup ratio, steel yield strength, and concrete strength were evaluated under cyclic loading and nonlinear dynamic time-history excitations. An incremental dynamic analysis-based probabilistic seismic demand model was further developed using 30 near-fault ground motions, with peak ground acceleration as the intensity measure and displacement ductility as the engineering demand parameter. The results showed that increasing the aspect ratio changed the failure mode from flexure-shear-dominated to flexure-dominated behavior, increasing the ultimate displacement from 122 mm to 155 mm while reducing the peak lateral strength from 263 kN to 248 kN. Increasing the longitudinal reinforcement ratio improved both peak strength and ultimate displacement, from 226 kN to 262 kN and from 120 mm to 160 mm, respectively. The numerical results indicated that aspect ratio, axial load ratio, and longitudinal reinforcement ratio had more pronounced effects on seismic demand and fragility than stirrup ratio. Increasing steel yield strength generally reduced seismic fragility, whereas increasing concrete strength enhanced lateral resistance but did not necessarily improve fragility performance. These findings suggest that the seismic performance of urban rail transport RC solid piers should be evaluated by combining cyclic response, dynamic demand, and fragility-based performance, rather than by maximizing any single design parameter. Full article

Türkiye has many historically rich cities that host structures of significant cultural value. These structures, especially masonry bridges, reflect the construction techniques and materials of the periods in which they were built. However, studies on the origins of these bridges and the structural deteriorations that develop over time are limited. This situation may lead to damage and even the risk of collapse if necessary precautions are not taken. In this study, stone and mortar samples were first collected from the historic Pamukçular (Şifalısu) Bridge in Bitlis, and the collected materials were analyzed. The structural behavior of the bridge under seismic effects was then investigated using the Finite Element Method (FEM). A three-dimensional geometric model of the bridge was created, and material parameters were defined based on values from the material analyses. Static analysis under self-weight and modal analysis were performed in the ABAQUS software (Version 6.14) to obtain the natural frequencies. Under the bridge’s self-weight, local stress concentrations were concentrated at the arch crown and pier-arch connections, with maximum tensile and compressive stresses reaching approximately 0.15 MPa and 0.27 MPa, respectively. These low stress levels demonstrate that the structure remains fully stable under static loading conditions. Finally, dynamic analyses in the time domain were carried out. In these analyses, records from the 2011 Van Earthquake and the 2023 Kahramanmaraş Earthquake were used to identify the bridge’s critical regions and evaluate its seismic performance. The results indicate that the overall structural stability is adequate; however, local stress concentrations occur in the arch crown and pier connection regions. The study provides engineering-based recommendations for preserving and strengthening historic masonry bridges. Full article

The recent seismic activity in southeastern Turkey in February 2023 again emphasized the critical need to promptly evaluate structural damage to assist in emergency response operations. This study introduces a comprehensive ensemble deep learning approach to structural damage classification following earthquake events, based on a dataset containing 13,270 high-resolution images with 15 different damage classes. Six different state-of-the-art convolutional neural network models (VGG16, ResNet50, InceptionV3, DenseNet121, EfficientNetB0, and MobileNetV2) are combined using a weighted voting approach to handle extreme class imbalance using weighted categorical cross-entropy loss. An integrated explainability component is incorporated into the trained convolutional neural network models to highlight the image regions that contribute to the predicted damage class, thereby improving the interpretability of deep learning decisions in safety-critical post-disaster assessment scenarios. The performance evaluation results show that the ensemble model achieves a test accuracy of 93.77%, with an increase of 2.67% compared to the best performing model individually. Notably, the ensemble model improves performance in minority classes like collapsed buildings. The proposed framework can be used to provide a powerful approach to structural damage evaluation, balancing accuracy with interpretability, to assist structural engineers in post-earthquake evaluation procedures. Full article

This paper presents the mechatronic design, mathematical modeling, parameter identification, and nonlinear position control of an open-architecture biaxial shake table capable of generating base acceleration along two orthogonal horizontal directions. The shake table is tailored for engineering research and education. Addressing the limitations of proprietary “black-box” systems, the platform is constructed using standard industrial components (HLTNC-CNC modules and NEMA 23 BLDC motors) to ensure reproducibility. A core contribution is the characterization of the system’s nonlinear dynamics to enhance tracking fidelity. The mathematical model, derived via the Euler–Lagrange formulation, incorporates viscous and Coulomb friction phenomena, which are critical for accurately reproducing zero-velocity crossings in seismic signals. System parameters are identified using the Recursive Least Squares (RLS) algorithm combined with State Variable Filters (SVFs) to process the regression vector. To enable precise closed-loop performance, a nonlinear state observer incorporating the identified friction dynamics is designed for velocity estimation. Furthermore, a Computed Torque Control (CTC) strategy is synthesized and compared against a conventional Proportional-Velocity (PV) controller. Experimental validations using historical ground motions, including the 1986 Colima earthquake, confirm that the CTC strategy reduces the maximum absolute tracking error by more than 75% compared to the PV approach, bounding the peak error to $0.36\mathrm{mm}$ across both axes. Furthermore, in high-amplitude scenarios, the proposed model-based approach achieved an RMS tracking error reduction of more than 83%. These results validate the proposed platform as a reliable and accessible tool for structural dynamics testing. Full article

Based on the global geospatial liquefaction model, this study adopts updated datasets of 30 m depth-averaged shear wave velocity ($V_{S30}$) and groundwater table depth ($wtd$) for the 2008 Wenchuan earthquake. Two models are then established: the local geospatial liquefaction model (LGLM), based solely on regional data, and the Bayesian-updated geospatial liquefaction model (BGLM), using Bayesian recalibration with global prior information and regional updated data. Model performance is evaluated using stratified five-fold cross-validation and spatial blocked cross-validation. The results show that integrating regional recalibration into the Bayesian framework effectively balances global prior information and regional data characteristics, reduces the global model’s systematic biases in regional applications, and provides accurate, stable, and regionally adaptable predictions within the study area. The Bayesian framework quantifies predictive uncertainty and characterizes performance variability. The uncertainty information obtained is more comprehensive and informative than the single-point AUC metric. Key variables for liquefaction prediction can be identified through Bayesian posterior distribution analysis. Regional updated data optimizes parameter estimation and enhances the regional consistency and interpretability of parameters for the Wenchuan earthquake case, providing supportive information for local engineering risk analysis and preliminary assessment. Full article

In performance-based earthquake engineering (PBEE), fragility curves hold significant importance for a reliable risk assessment of the existing reinforced concrete (RC) structures. Fragility curves require numerous incremental nonlinear dynamic analyses, which are highly time-consuming and computationally intensive. However, predicting the fragility curve parameters of RC structures by a machine learning algorithm could effectively reduce this cost. In this study, machine learning (ML)-based numerical analyses were performed in order to predict the fragility curve parameters of the existing RC structures, considering rapidly observable structural parameters by street survey. The construction date, story number, plan irregularities, soft story, and damage states are the main variables that are considered in this study. Hence, a dataset comprising the results of 620 structural fragility analyses was compiled from the existing literature. Key fragility parameters, namely the median and standard deviation, are predicted using several machine learning algorithms, including Random Forest (RF), Extreme Gradient Boosting (XGBoost), Support Vector Machine (SVM), and Artificial Neural Networks (ANNs). The performance of the proposed models is evaluated using R², RMSE, and MAE metrics under a five-fold cross-validation scheme. Furthermore, nonlinear dynamic analyses are conducted on a representative set of structural models to validate the machine learning predictions. The results indicate that the ANN model achieves the highest predictive accuracy, followed by ensemble tree-based methods, demonstrating the capability of machine learning approaches to effectively capture complex nonlinear relationships between seismic input parameters and structural response. The proposed framework significantly reduces computational effort while maintaining reliable prediction accuracy, offering an efficient tool for seismic risk assessment and fragility estimation of existing structures. Full article

The piping systems are critical non-structural elements (NSEs) whose seismic performance directly affects the post-earthquake functionality of essential facilities. However, current seismic design provisions for such systems remain largely empirical, and behavioural factors are rarely calibrated using performance-based methods. This study implements an FEMA P695-inspired framework to calibrate the behaviour factor $\left(q_a\right)$for the installation of sway-braced suspended piping restraint systems in following the force-based requirements specified in Eurocode 8. The representative piping archetypes were developed and analysed using non-linear time history analyses under multiple seismic intensity levels derived from the floor response spectra (FRS) of prototype-reinforced concrete buildings. Fragility curves for two limit states were derived with displacement ductility adopted as the engineering demand parameter (EDP) and peak floor acceleration (PFA) used as the intensity measure (IM). The results show that increasing $\left(q_a\right)$ systematically shifts the fragility curves towards lower median PFA values, indicating higher seismic vulnerability at larger behaviour factor values. The effect of piping layout configuration was of secondary importance compared to the applied reduction factor. The implemented approach provides a rational basis for selecting behavior factors consistent with explicit performance objectives and supports further development of performance-oriented seismic design procedures for non-structural systems. The results show that increasing the behaviour factor $\left(q_a\right)$ leads to a systematic shift in the fragility curves towards lower median PFA values and a noticeable increase in the dispersion of the response. A quantitative analysis shows that increasing the behaviour factor $\left(q_a\right)$ from 1 to 4 results in a reduction of up to approximately 60% in median PFA, highlighting a significant increase in seismic vulnerability at higher behaviour factor values. Full article

Coupling beams are critical connecting components in coupled shear wall systems and core tube structures. At the same time, they play an important role when the structure is subjected to an earthquake. Plate-reinforced composite (PRC) coupling beams exhibit superior comprehensive performance in terms of bearing capacity, deformation performance, energy dissipation capacity, and construction efficiency. However, research on PRC coupling beams remains limited both domestically and internationally. To better describe the structural response of steel plate–concrete composite coupling beams, this study collected existing experimental data. The beams had a small span-to-depth ratio. The loading was cyclic. The study normalized the skeleton curves of each specimen. The span-to-depth ratio ranged from 0.9 to 2.5. The plate ratio ranged from 3% to 5%. For these beams, preliminary skeleton curve fitting equations are proposed. The equations are based on existing data. The equations apply to two types of composite coupling beams. One type uses a steel plate and ordinary concrete. The other type uses a steel plate and fiber concrete. These equations are derived using a trilinear model and linear fitting tools. Furthermore, restoring force models for steel plate–conventional concrete and steel plate–fiber concrete composite coupling beams with a small span-to-depth ratio are proposed. Comparative analysis shows that each model captures the hysteretic response of PRC coupling beams with acceptable accuracy in the elastic and decline phases, while the elastic–plastic stage is suitable only for trend prediction. It should be noted that the proposed models are preliminary engineering approximations primarily applicable within the following ranges: a span-to-depth ratio of 0.9~2.5, a plate ratio of 3~5%, concrete strength of C30~C50, a longitudinal reinforcement ratio of 0.86~2.23%, a stirrup ratio of 0.56~0.63%, and a steel plate thickness of 6~10 mm. For configurations significantly outside these ranges, additional experimental validation is required. Full article

On 26 January 2026, a 5.5-magnitude earthquake occurred in Diebu County, Gansu Province, causing different degrees of damage and collapse to houses. To understand the damage characteristics and causes of typical buildings, a post-earthquake damage assessment was conducted on buildings in the epicentral area through field investigations of 16 urban buildings and rural houses in 10 natural villages. The results indicate that among the rural buildings, timber frame structures accounted for the largest proportion and suffered the worst damage, primarily manifested as overall collapse of enclosure walls, partial wall collapse, and wall cracking. Brick–wood structures and non-seismic fortification masonry structures suffered relatively minor damage, mainly characterized by cracks at the intersections of longitudinal and transverse walls, as well as diagonal cracks around door and window openings. In urban buildings, reinforced concrete frame structures are more prevalent, with damage primarily concentrated on infill walls, stairwells, suspended ceilings and decorative surfaces. In seismic-resistant masonry structures, the damage primarily involves the failure of non-structural components such as parapets and canopies. The primary causes of seismic damage are construction defects and the absence of seismic structural measures in self-built houses, insufficient seismic resilience in non-structural components of seismic-resistant structures, and the site amplification effect and secondary seismic hazards, which exacerbate the damage to buildings. Furthermore, improvement measures are proposed based on the seismic damage characteristics of different structures. These include conducting research on the construction techniques of Tibetan-style timber-frame houses, developing design and construction standards tailored to local conditions, and enhancing the seismic performance of non-structural components for seismic-resistant structures. The aim is to provide a scientific basis and engineering guidance for post-disaster reconstruction and earthquake disaster prevention in affected areas. Full article

This study presents a probabilistic seismic fragility assessment of a jointed rock slope by integrating field characterization, incremental dynamic analysis (IDA), and numerical modeling. Dominant joint sets are identified through field mapping, and key discontinuity parameters are estimated for the Barton–Bandis non-linear shear strength criterion. Dynamic simulations are performed using the distinct element method with the continuously yielding (C-Y) joint model to capture progressive shear degradation. Twenty real earthquake ground-motion records are scaled incrementally to perform IDA, with critical block displacement and cumulative joint slip adopted as engineering demand parameters (EDPs). A probabilistic seismic demand model (PSDM) is developed to correlate peak ground acceleration (PGA) with EDPs. Kinematic analysis indicates that planar failure along joint set 1 is the most likely failure mechanism (90% probability), followed by wedge failure along the intersection of joint sets 1 and 2 (52%). Fragility curves are derived for three displacement-based damage states: minor (1 cm), moderate (5 cm), and severe (15 cm). The results demonstrate that seismic deformation is strongly controlled by discontinuity geometry and progressive joint slip, with the slope exceeding the severe damage state at PGA levels as low as 0.4 g, indicating high seismic vulnerability. This highlights the importance of integrating field characterization with dynamic numerical modeling for reliable seismic stability assessment of such discontinuous rock mass. Future work should incorporate larger datasets, in situ testing, and 3D modeling to enhance assessment reliability. Full article

This study presents an integrated design methodology for earthquake demolition rescue robots by combining UXMs, Kano, and QFD to improve design rationality and performance in extreme rescue scenarios. It addresses key gaps in existing approaches, particularly the lack of systematic experiential data acquisition, quantitative requirement analysis, and effective design translation. UXMs are applied to reconstruct critical task scenarios and identify high-load nodes and user experience variations. The Kano model is used to prioritise and classify user requirements, which are then translated into engineering characteristics through QFD. Based on this framework, a conceptual robot design is developed using the FBS model and evaluated through process-level simulation and usability assessment. The results demonstrate that the proposed method enables structured requirement transformation and supports traceable design decisions. Simulation indicates the consistency of task workflows and coordination among functional modules at the process level. A System Usability Scale score of 80.22 indicates a relatively high level of perceived usability at the conceptual evaluation stage. The proposed methodology provides a structured and traceable conceptual design framework for earthquake rescue robots. While the current validation is based on conceptual-level evaluation, the methodology offers a traceable design pathway that may be extended to other high-risk emergency equipment with further empirical testing. Full article

To explore the evolution of dynamic characteristics of Chuan-Dou timber structures under different damage states, this study takes a typical Chuan-Dou timber structure in Southwest China as the research object. A 1:7 scaled model of a two-story timber frame with five main columns and four secondary columns, three bays, and two rooms was designed and fabricated, and combined pseudo-static and dynamic tests were carried out. When the specimen was in three typical states, namely intact, moderate damage, and severe damage, the sudden release method was adopted to obtain structural vibration responses. The natural frequencies and damping ratios in the X- and Y-directions under each state were identified, and the damage sensitivity differences among stiffness, frequency, and damping ratio were compared and analyzed. The test results show that with the aggravation of damage degree, structural stiffness degrades continuously, and the natural frequency shows a monotonic decreasing trend. The X-direction frequency decreases from 11.178 Hz to 7.8 Hz, and the Y-direction frequency decreases from 6.2 Hz to 5.156 Hz. The damping ratio increases significantly. The X-direction damping ratio increases from 3.552% to 8.951% (an increase of 152.0%), and the Y-direction damping ratio increases from 4.391% to 11.94% (an increase of 171.9%). Comparative analysis shows that the change amplitude of the damping ratio is about 5 to 10 times that of the natural frequency, and it has higher identification sensitivity to structural non-linear damage behavior. This paper innovatively applies the frequency-damping ratio dual-index collaborative determination strategy to Chuan-Dou timber structures, establishes a damage identification method based on the evolution of dynamic characteristic parameters, and discusses the engineering application paths of sensor optimal layout strategy, structural health archive establishment, and post-earthquake rapid screening. The research results can provide experimental basis and technical reference for daily health monitoring, post-earthquake rapid identification, and seismic performance evaluation of traditional timber structures of Chuan-Dou timber structures. Full article