Search Results (200)

Earthquake-induced soil liquefaction poses a severe threat to the structural safety of underground infrastructure. This paper presents a shaking table model test conducted on sand sites, where two site models—namely, uniform saturated sand and layered dry–saturated sand—are designed to systematically analyze the influences of seismic wave amplitude, seismic wave frequency, and structure burial depth on the development of pore water pressure. The research findings indicate the following: (1) As the input peak ground acceleration (PGA) increases, the output surface peak ground acceleration rises, while the acceleration amplification factor decreases. Under high-intensity earthquakes, sand boiling and water gushing are observed in the uniform saturated sand site, and the overlying unsaturated layer can effectively inhibit the liquefaction development of the underlying saturated sand layer. (2) When the predominant frequency of the input seismic wave is close to the natural vibration frequency of the test site, the surface acceleration response is significantly enhanced, while the resonance effect of low-frequency seismic components is relatively weak. (3) The pore pressure ratio is higher in shallow soil layers, indicating that shallow strata are more prone to liquefaction. Both the pore pressure accumulation rate and the peak pore pressure ratio under uniform saturated sand conditions are higher than those measured in the layered dry–saturated sand site. (4) The sensitivity ranking of the three influencing factors is input PGA > burial depth > seismic wave frequency, where the input PGA is the dominant influencing factor, and the effect of the seismic wave frequency is not statistically significant. The conclusions of this study can provide a reference for seismic response assessment and anti-liquefaction design of shallow-buried structures in liquefiable sites. Full article

High-speed railway track–bridge systems (HSRTBSs) in near-fault high-seismicity regions face combined threats from pulse-type seismic excitations, vertical earthquake components and track defects, which may trigger structural damage and deterioration of track regularity. This paper establishes refined OpenSEES coupled numerical models for a typical 32 m simply supported girder bridge equipped with CRTS II slab ballastless track, considering both conventional spherical steel bearings and friction pendulum bearings (FPBs). Nonlinear time-history analyses are performed with near-fault pulse-like and far-field non-pulse ground motions to explore the influences of peak ground acceleration (PGA), vertical-to-horizontal acceleration ratio (αVH), and CA mortar void length. The results demonstrate hierarchical controlling effects of these parameters. PGA dominates the overall seismic response; sliding layer damage follows the sensitivity sequence PGA > αVH > CA mortar void, whereas post-earthquake traffic capacity degradation obeys PGA > CA mortar void > αVH. Near-fault pulse-like ground motions produce more severe structural damage compared with far-field inputs. FPB isolation yields a maximum pier-top seismic reduction ratio of 86.73% and effectively mitigates structural deformation, but cannot eliminate track irregularity originating from CA mortar void defects. Conditional on the 0.2 g seismic level and the given structural configuration adopted in this study, αVH = 0.65 and the 1.95 m critical CA mortar void length for longitudinal track constraint failure can serve as reference values, though they are not universally applicable for all track–bridge systems. This work provides insights for seismic design, CA mortar defect remediation and post-earthquake traffic assessment of near-fault isolated HSRTBSs. Full article

This paper proposes an urban-scale dynamic screening method for the preliminary seismic-risk prioritization of masonry buildings. The method is based on the integration of rapid surveys, relational databases, geographic information systems, and accelerometric data recorded during seismic events. It is not intended to replace comprehensive seismic vulnerability or risk assessment procedures. In its present formulation, it provides an event-specific preliminary dynamic-priority indicator, derived from recorded ground motions, to support post-event inspections and subsequent detailed analyses at the urban scale. The procedure combines a rapid visual survey (on average covering ca. 300 buildings per day) with a database management system (DBMS) linked to a three-dimensional cartographic database of the building stock. The geometric and structural information collected in the field is integrated with the processing of ground acceleration records, from which the pseudo-acceleration spectra, peak ground acceleration (PGA), and spectral amplification ratios (DAF) are derived. Through the relationship between spectral period and building height, the method identifies height classes and number of storeys corresponding to the highest spectral amplification ratios derived from the recorded ground motions. Buildings belonging to these classes are not classified as vulnerable in absolute terms, but are considered priority buildings for subsequent checks, inspections, or detailed analyses. The method was applied to the municipalities of Umbertide and Gubbio, in the province of Perugia, which were affected by the seismic sequence of 9 March 2023. The processed accelerometric records identified Classes I, II and III, corresponding to one-, two-, and three-storey masonry buildings. The illustrative GIS application focused on Classes II and III; 27 of the 33 masonry buildings included in the damaged-building sample (82%) belonged to these two classes. The main contribution of the study is the definition of an integrated, rapid, and replicable workflow that can support local authorities, technicians, and civil protection operators in the preliminary management of seismic risk at the urban scale. Full article

To simulate the fracture behavior of members during structural collapse, this paper proposes a member fracture simulation algorithm that integrates the plastic hinge model with a ductile fracture damage model within the member discrete element method (MDEM) framework. The coupling is achieved by computing stresses at the four most unfavorable edge points of the contact section and using the minimum fracture strain as the section-level failure criterion. The algorithm is validated against a cantilever beam fracture example, yielding results in good agreement with reference data under two yield stress conditions. The fracture algorithm is then embedded as a self-contained module into an adaptively coupled DEM/FEM algorithm and applied to simulate the shaking table collapse test of a single-layer spherical reticulated shell. The simulation predicts structural collapse at a peak ground acceleration (PGA) of 2268 gal—consistent with the experimental value—with 126 members fractured at collapse onset, and reproduces the observed fracture sequence in which first-ring diagonal members near the supports fail progressively from the bottom upward. The proposed framework provides a computationally robust and practically deployable tool for collapse analysis of large-span reticulated structures, with direct implications for progressive-collapse prevention in seismic design and post-event structural forensic investigation of collapse mechanisms. Full article

Ground-motion intensity measures (IMs) are key parameters for seismic hazard and risk assessment. However, seismic hazard characterization and code-based design spectra commonly rely on a limited set of parameters, particularly peak ground acceleration (PGA), spectral acceleration, and control periods defining spectral shape. Such representations may not fully capture seismic input relevant to structural response, soil deformation, slope instability, and indirect environmental impacts. This study analyzes 220 horizontal accelerogram components recorded during the Vrancea earthquakes of 4 March 1977, 30 August 1986, 30 May 1990, and 31 May 1990. Twenty-three IMs were computed, covering peak and effective amplitudes, velocity-related measures, cumulative and energy-based indicators, spectral intensities, duration, cyclicity, and impulsivity, together with a set of frequency content-related parameters. Pearson and Spearman correlations were evaluated using both the geometric mean and the maximum of the two horizontal components. Hierarchical clustering, PGA-centered correlation profiles, event-specific comparisons, and spatial representations were used to assess redundancy, complementarity, and relationship stability. Results show that amplitude-, velocity-, and spectrum-related IMs form strongly correlated groups, whereas duration, cyclicity, and impulsivity remain more distinct. Spatial comparisons also show that different IMs may produce different station rankings and regional patterns for the same event. These findings support selecting complementary IM families for more comprehensive, risk-informed structural and geotechnical applications. Full article

Steel-reinforced concrete (SRC) frame-bent hybrid structures are widely used in conventional island buildings of nuclear power plants because of their favorable seismic performance and economic efficiency. However, the seismic fragility of these structures has not been adequately investigated. In this study, the main turbine building of the CAP1400 nuclear power plant in Rongcheng, Shandong Province, China, was selected as the prototype. A three-bay frame-bent substructure was extracted, and a 1/7-scale model was designed for pseudo-dynamic testing to investigate the evolution of seismic damage and the failure mechanisms of the structure. Based on the experimental results, a refined numerical model was developed in OpenSees. Incremental dynamic analysis (IDA) was subsequently conducted to evaluate the seismic fragility of the SRC frame-bent main turbine building under far-field and near-fault ground motions. The results indicate that the structural stiffness progressively decreases with increasing seismic demand because of concrete cracking and cumulative damage. Damage is primarily concentrated in the short columns, beam-column joints, and column bases. The fragility response also exhibits pronounced directional dependence. Because of the lower lateral stiffness in the X direction, the structure develops larger interstory drift demands and higher probabilities of exceeding the prescribed damage states in the X direction than in the Y direction. For the selected ground-motion suites, near-fault records generally produce slightly higher exceedance probabilities than far-field records at the same peak ground acceleration (PGA), with a maximum difference of 3.68%. However, the magnitude of this difference varies with the damage state, excitation direction, and ground-motion intensity. These findings indicate that pulse-like near-fault ground motions may have a measurable but moderate effect on the seismic fragility of SRC frame-bent main turbine buildings. This study establishes an experimentally validated framework for assessing the seismic fragility of SRC frame-bent structures in nuclear power plants and identifies their vulnerable components, dominant damage mechanisms, and fragility characteristics under different types of ground-motion input. Full article

Near-fault pulse-like ground motions produce coupled intensity, duration, and period-matching effects, making nonlinear seismic assessment of multi-ribbed composite slab structures (MCSS) computationally expensive and difficult to generalize. To address this problem, a 4000-case OpenSees nonlinear time-history analysis (NLTHA) database is generated from Wenchuan ground motions through Latin hypercube sampling, and a mechanically informed feature-enhanced deep neural network (MIFE-DNN, previously denoted as PE-DNN in the first submission) is trained using equivalent stiffness, equivalent yield strength, mass proxy, demand-capacity ratios, period-matching ratio, normalized duration, and energy-capacity proxy; a validation-weighted stacked surrogate is further constructed from multi-seed MIFE-DNN and residual learners. On the independent test set, the mean $R^2$ increases from 0.9645 for the ordinary deep neural network (DNN) and 0.9686 for the single MIFE-DNN to 0.9782 for the stacked mechanically informed surrogate, while the maximum inter-story drift-ratio $R^2$ reaches 0.9541. Additional checks include 16 active-learning OpenSees enrichment cases, 12 analyses under two external near-fault records, 3 out-of-domain parameter cases, 100 cross-story tests, SHAP-based interpretation, and multi-EDP fragility post-processing. These checks show that the surrogate is reliable for interpolation and screening within the calibrated equivalent-model domain, but direct OpenSees recalculation is required for boundary, out-of-domain, and cross-configuration use. Parameter-importance, SHAP, and fragility analyses identify peak ground acceleration (PGA), pulse index, period matching, rib height, rib spacing, and damping ratio as dominant factors, indicating that mechanically informed feature-enhanced surrogate modeling provides an interpretable and efficient tool for MCSS response prediction and conditional fragility assessment within the sampled structural and ground-motion domain. Full article

Reinforced concrete frame structures (RCFSs) subjected to strong seismic excitation may enter a metastable semi-ruin state before global collapse, characterized by severe local damage, degraded stability, and high secondary collapse risk. However, systematic experimental investigations and quantitative identification techniques for this critical transitional state are still lacking in existing seismic engineering literature, forming a notable research gap for post-earthquake safety evaluation. To investigate this critical transition, a Digital Image Correlation (DIC)-assisted shaking table test was conducted on a 1/25-scale RCFS specimen derived from an earthquake-damaged exterior-corridor teaching building, using the Wolong ground motion recorded during the 2008 Wenchuan earthquake as input. DIC was employed to track the full-field evolution of cracking, through-crack development, and concrete cover spalling under incremental seismic loading. Four local damage indices—crack line density (CLD), crack propagation rate (CPR), through-crack ratio (TCR), and concrete spalling ratio (CSR)—were extracted and evaluated with the inter-story drift ratio (IDR) to quantify local-to-global degradation. The results show that visible cracks initiated at PGA = 0.3 g, while accelerated crack propagation occurred at 0.7–0.8 g, with CPR peaks of 1187.5 and 1140 mm/g, respectively. At 0.5–1.0 g, the crack number increased from 13 to 26, total crack length reached 0.443 m, CLD increased to 3.9 × 10⁻⁴, and TCR reached 37.04%. At 1.1–1.5 g, crack development approached saturation, with total crack length of 0.552 m, maximum TCR of 63.6%, and CLD of 4.8 × 10⁻⁴. Under ultimate excitation of 1.6–1.8 g, the crack number stabilized at 33–34, TCR remained around 63%, cumulative spalling area reached 1026 mm², CSR reached 0.015, and the third-floor IDR approached the 1/50 elastoplastic limit. Severe through-cracking, reinforcement exposure, concrete spalling, and residual inclination indicated the onset of the semi-ruin state. The proposed multi-index framework provides quantitative support for semi-ruin-state identification and post-earthquake secondary collapse risk assessment of RCFSs. Full article

Near-fault pulse-like ground motions (NFPLGMs) impose concentrated energy demands that can severely damage bridges, yet their scarcity and the influence of structural parameter uncertainties are often neglected in seismic fragility assessments. This study proposed a synthesis method for NFPLGMs by superposing low-frequency pulse components (extracted via the Gabor wavelet transform and low-pass filtering) with high-frequency stochastic components based on an evolutionary power spectrum. A three-span reinforced concrete bridge was modeled in OpenSeesPy, and Incremental Dynamic Analysis (IDA), together with a quadratic response surface model, were used to plot seismic fragility curves. The damping ratio (ξ), elastic modulus of steel reinforcement (E_s), yield strength of steel reinforcement (f_y), diameter of longitudinal reinforcement (D), and peak ground acceleration (PGA) were treated as random variables. Sensitivity indices were computed using Monte Carlo sampling (n = 10,000). Results show that ξ most strongly affects the displacement ductility ratio of the bridge pier (u_d) (variation of up to 32.6%), while E_s dominates the shear deformation of the bridge bearing (d) (variation of up to 43.8%). Neglecting structural parameter uncertainties overestimates median PGA thresholds (m_R) for different damage states by 1.5%–36.1%, and replacing NFPLGMs with ordinary ground motions overestimates seismic capacity by 1.7%–36.6%. The bridge bearing is consistently more vulnerable than the pier, with a collapse probability of 0.9566 at PGA = 1.0 g. These findings highlight the necessity of incorporating both NFPLGM characteristics and structural parameter uncertainties into bridge seismic fragility assessment. On the other hand, when seismic retrofitting of bridges is carried out using coating materials, priority should be given to more vulnerable components, such as bridge bearings, to improve the utilization efficiency of limited resources. Full article

Earthquake-induced landslides represent a critical threat to transportation infrastructure in tectonically active mountainous regions, particularly in tropical volcanic settings where weak, highly weathered geomaterials dominate. This study develops an integrated framework that directly links physically based seismic threshold modelling with real-time landslide monitoring and operational early warning. The approach is demonstrated in the Cugenang area of Cianjur Regency, West Java, Indonesia, which was severely impacted by the moment magnitude (Mw) 5.6 earthquake in 2022. Slopes composed of highly weathered pyroclastic deposits [Plasticity Index (PI) = 54–68%; porosity > 60%] exhibit low shear strength and high sensitivity to seismic loading. Limit equilibrium analysis using the Morgenstern–Price method that combines the influence of seismic loading and groundwater conditions suggests that a horizontal seismic coefficient (kh) of approximately 0.06, corresponding to a Peak Ground Acceleration (PGA) of about 0.12 gravitational acceleration (g), is a critical threshold for initial landsliding. This comparatively low threshold challenges commonly reported values and demonstrates that slope failure in tropical volcanic terrains can occur under moderate ground shaking, reinforcing the need for site-specific hazard characterisation. The derived thresholds are operationalised within a multi-sensor early warning system integrating Micro-Electro-Mechanical Systems (MEMS) accelerometers and inclinometer measurements. Three hazard levels—Normal (<0.06 g), Alert (0.06–0.12 g), and Emergency (≥0.12 g)are combined with deformation thresholds [<10 milimeter (mm), 10–30 mm, >30 mm] to capture progressive failure processes and minimise false alarms. By coupling geotechnical modelling and real-time monitoring, this study provides a transferable and scalable framework for enhancing infrastructure resilience in landslide-prone regions. Full article

This study focuses on RCS frame structures and selects six different types of ground-motion intensity measures (IMs), including peak ground acceleration (PGA), spectral acceleration at the fundamental period Sa(T₁), the modified intensity measure S^* considering period elongation effects, IM₁₂ and IM₁₂₃ accounting for higher-mode effects, and Housner intensity (HI). Based on a set of near-fault pulse-like ground-motion records, a Bayesian seismic fragility analysis characterized by different IMs is conducted. This study reveals the influence of these IMs on the estimation of fragility parameters under three limit states—immediate occupancy (IO), life safety (LS), and collapse prevention (CP)—using both uniform non-informative priors and lognormal weakly informative priors. The results indicate that, in terms of the applicability of IMs across different limit states, all IMs exhibit highly stable fragility parameters in the elastic IO stage, where the results from maximum likelihood estimation (MLE), uniform priors, and lognormal priors are nearly identical, suggesting that sufficient sample information renders the influence of priors negligible. In contrast, in the CP stage, characterized by strong nonlinearity and collapse, the differences among IMs become most pronounced. HI consistently yields stable results across all methods with almost no variation. When the structure enters the CP stage with small samples and strong nonlinearity, the lognormal prior effectively promotes distribution convergence, suppresses over-dispersion, and corrects asymmetry, significantly improving the robustness of parameter estimation. Notably, different IMs exhibit varying sensitivity to Bayesian priors, among which S^* and HI are the least sensitive, demonstrating strong inherent stability and minimal dependence on prior constraints. 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

Baguio City, a highly populated city in the mountainous portion of the Cordillera, is vulnerable to earthquake hazards due to its proximity to earthquake generators. For this reason, identifying its threats by generating seismic hazard assessments such as peak ground acceleration (PGA) is one of the important necessities to be considered in order to mitigate damages and reduce casualties. Further, the effects of topography, aside from the site conditions, play an important role in the amplification of ground motions. In this study, a peak ground acceleration (PGA) is generated with the influence of topographic effects. Data gathered from geophysical surveys were utilized as inputs in generating the site amplification for Baguio City. The amplification values are then incorporated into the composite peak ground acceleration (PGA) generated by simulating each individual fault source surrounding Baguio City, thereby generating the final PGA for Baguio City. Results revealed that 39% of Baguio City may experience a ground acceleration value of 0.71 g to 0.8 g. Specific places, such as the Pinsao Proper area, may experience higher acceleration. Full article

Armenia is located within the central segment of the Arabia–Eurasia continental collision zone and is exposed to significant seismic hazard. This study presents an updated probabilistic seismic hazard assessment (PSHA) for Armenia based on an integrated seismotectonic framework incorporating active fault data, paleoseismological evidence, and historical and instrumental seismicity. A hybrid seismic source model was developed by combining fault-based characteristic earthquake sources with distributed background seismicity. Hazard calculations were performed using the OpenQuake engine within a logic-tree framework to account for epistemic uncertainties in earthquake occurrence and ground-motion prediction. Ground motion was estimated using a weighted set of ground motion prediction equations (GMPEs). Peak ground acceleration (PGA) hazard maps were computed for several return periods, with emphasis on the 475-year return period (10% probability of exceedance in 50 years). The results indicate PGA values across Armenia ranging from approximately 0.2 g to 0.5 g, with the highest hazard levels in northwestern Armenia along the Pambak–Sevan–Syunik Fault System. Hazard deaggregation shows that seismic hazard in major Armenian cities is primarily controlled by shallow earthquakes with magnitudes Mw 6.8–7.4 occurring within ~30 km of urban centers. The results provide a scientific basis for seismic hazard assessment, zonation, and earthquake risk mitigation in Armenia. Full article

This study evaluates the seismic performance of the East Main Hall of Foguang Temple in Shanxi, focusing on the impact of wood property degradation on structural stability. A dynamic model of the hall is developed using the discrete element method (DEM) and Wallstat 5.1.3 software, simulating seismic responses under three conditions: intact wood properties, 0.85-fold reduction, and 0.75-fold reduction in wood properties. Peak ground acceleration (PGA) is used as the seismic intensity measure, and the maximum inter-story drift angle of the column frame is selected as the structural response parameter. Incremental dynamic analysis (IDA) is applied to generate seismic vulnerability curves to assess the influence of wood degradation on seismic performance. The results show that the DEM model’s natural frequency (2.40 Hz) is only 2.13% different from the code-estimated value (2.35 Hz), confirming the model’s reliability. As wood degradation increases, the maximum inter-story drift angle grows significantly, with the 0.75-fold reduction model exhibiting larger displacements than the intact and 0.85-fold reduction models. Seismic vulnerability curves indicate that wood degradation accelerates damage progression, with the 0.75-fold reduction model showing an 8.74% higher collapse probability under a PGA of 1 g. Full article